Melvyn Bragg and guests discuss the tiny drifting organisms in the oceans that sustain the food chain for all the lifeforms in the water and so for the billions of people who, in turn, depend on the seas for their diet. In Earth's development, the plant-like ones among them, the phytoplankton, produced so much oxygen through photosynthesis that around half the oxygen we breathe today originated there. And each day as the sun rises, the animal ones, the zooplankton, sink to the depths of the seas to avoid predators in such density that they appear on ship sonars like a new seabed, only to rise again at night in the largest migration of life on this planet. With Carol Robinson Professor of Marine Sciences at the University of East Anglia Abigail McQuatters-Gollop Associate Professor of Marine Conservation at the University of Plymouth And Christopher Lowe Lecturer in Marine Biology at Swansea University Producer: Simon Tillotson Reading list: Juli Berwald, Spineless: The Science of Jellyfish and the Art of Growing a Backbone (Riverhead Books, 2018) Sir Alister Hardy, The Open Sea: The World of Plankton (first published 1959; Collins New Naturalist Library, 2009) Richard Kirby, Ocean Drifters: A Secret World Beneath the Waves (Studio Cactus Ltd, 2010) Robert Kunzig, Mapping the Deep: The Extraordinary Story of Ocean Science (Sort Of Books, 2000) Christian Sardet, Plankton: Wonders of the Drifting World (University of Chicago Press, 2015) Helen Scales, The Brilliant Abyss: True Tales of Exploring the Deep Sea, Discovering Hidden Life and Selling the Seabed (Bloomsbury Sigma, 2022)

Melvyn Bragg and guests discuss the man who, in 1905, produced several papers that were to change the world of physics and whose name went on to become a byword for genius. This was Albert Einstein, then still a technical expert at a Swiss patent office, and that year of 1905 became known as his annus mirabilis ('miraculous year'). While Einstein came from outside the academic world, some such as Max Planck championed his theory of special relativity, his principle of mass-energy equivalence that followed, and his explanations of Brownian Motion and the photoelectric effect. Yet it was not until 1919, when a solar eclipse proved his theory that gravity would bend light, that Einstein became an international celebrity and developed into an almost mythical figure. With Richard Staley Professor in History and Philosophy of Science at the University of Cambridge and Professor in History of Science at the University of Copenhagen Diana Kormos Buchwald Robert M. Abbey Professor of History and Director and General Editor of The Einstein Papers Project at the California Institute of Technology And John Heilbron Professor Emeritus at the University of California, Berkeley Producer: Simon Tillotson Reading list: Ronald W. Clark, Einstein: The Life and Times (first published 1971; HarperPaperbacks, 2011) Albert Einstein (eds. Jurgen Renn and Hanoch Gutfreund), Relativity: The Special and the General Theory - 100th Anniversary Edition (Princeton University Press, 2019) Albert Einstein, Out of My Later Years (first published 1950; Citadel Press, 1974) Albert Einstein (ed. Paul A. Schilpp), Albert Einstein: Philosopher-Scientist: The Library of Living Philosophers Volume VII (first published 1949; Open Court, 1970) Albert Einstein (eds. Otto Nathan and Heinz Norden), Einstein on Peace (first published 1981; Literary Licensing, 2011) Albrecht Folsing, Albert Einstein: A Biography (Viking, 1997) J. L. Heilbron, Niels Bohr: A Very Short Introduction (Oxford University Press, 2020) Walter Isaacson, Einstein: His Life and Universe (Simon & Schuster, 2008) Max Jammer, Einstein and Religion (Princeton University Press, 2002) Michel Janssen and Christoph Lehner (eds.), The Cambridge Companion to Einstein (Cambridge University Press, 2014) Dennis Overbye, Einstein in Love: A Scientific Romance (Viking, 2000) Abraham Pais, Subtle Is the Lord: The Science and the Life of Albert Einstein (Oxford University Press, 1982) David E. Rowe and Robert Schulmann (eds.), Einstein on Politics: His Private Thoughts and Public Stands on Nationalism, Zionism, War, Peace, and the Bomb (Princeton University Press, 2007) Matthew Stanley, Einstein's War: How Relativity Triumphed Amid the Vicious Nationalism of World War I (Dutton, 2019) Fritz Stern, Einstein’s German World (Princeton University Press, 1999) A. Douglas Stone, Einstein and the Quantum: The Quest of the Valiant Swabian (Princeton University Press, 2013) Milena Wazeck (trans. Geoffrey S. Koby), Einstein's Opponents: The Public Controversy About the Theory of Relativity in the 1920s (Cambridge University Press, 2014)

Melvyn Bragg and guests discuss the power-packs within cells in all complex life on Earth. Inside each cell of every complex organism there are structures known as mitochondria. The 19th century scientists who first observed them thought they were bacteria which had somehow invaded the cells they were studying. We now understand that mitochondria take components from the food we eat and convert them into energy. Mitochondria are essential for complex life, but as the components that run our metabolisms they can also be responsible for a range of diseases – and they probably play a role in how we age. The DNA in mitochondria is only passed down the maternal line. This means it can be used to trace population movements deep into human history, even back to an ancestor we all share: mitochondrial Eve. With Mike Murphy Professor of Mitochondrial Redox Biology at the University of Cambridge Florencia Camus NERC Independent Research Fellow at University College London and Nick Lane Professor of Evolutionary Biochemistry at University College London Producer Luke Mulhall

Melvyn Bragg and guests discuss the life, ideas and legacy of the pioneering Swedish botanist Carl Linnaeus (1707 – 1778). The philosopher Jean-Jacques Rousseau once wrote: "Tell him I know no greater man on earth". The son of a parson, Linnaeus grew up in an impoverished part of Sweden but managed to gain a place at university. He went on to transform biology by making two major innovations. He devised a simpler method of naming species and he developed a new system for classifying plants and animals, a system that became known as the Linnaean hierarchy. He was also one of the first people to grow a banana in Europe. With Staffan Muller-Wille University Lecturer in History of Life, Human and Earth Sciences at the University of Cambridge Stella Sandford Professor of Modern European Philosophy at Kingston University, London and Steve Jones Senior Research Fellow in Genetics at University College, London Producer Luke Mulhall

Paul Erdős (1913 – 1996) is one of the most celebrated mathematicians of the 20th century. During his long career, he made a number of impressive advances in our understanding of maths and developed whole new fields in the subject. He was born into a Jewish family in Hungary just before the outbreak of World War I, and his life was shaped by the rise of fascism in Europe, anti-Semitism and the Cold War. His reputation for mathematical problem solving is unrivalled and he was extraordinarily prolific. He produced more than 1,500 papers and collaborated with around 500 other academics. He also had an unconventional lifestyle. Instead of having a long-term post at one university, he spent much of his life travelling around visiting other mathematicians, often staying for just a few days. With Colva Roney-Dougal Professor of Pure Mathematics at the University of St Andrews Timothy Gowers Professor of Mathematics at the College de France in Paris and Fellow of Trinity College, Cambridge and Andrew Treglown Associate Professor in Mathematics at the University of Birmingham The image above shows a graph occurring in Ramsey Theory. It was created by Dr Katherine Staden, lecturer in the School of Mathematics at the Open University.

Melvyn Bragg and guests discuss the pioneering Danish astronomer Tycho Brahe (1546 – 1601) whose charts offered an unprecedented level of accuracy. In 1572 Brahe's observations of a new star challenged the idea, inherited from Aristotle, that the heavens were unchanging. He went on to create his own observatory complex on the Danish island of Hven, and there, working before the invention of the telescope, he developed innovative instruments and gathered a team of assistants, taking a highly systematic approach to observation. A second, smaller source of renown was his metal prosthetic nose, which he needed after a serious injury sustained in a duel. The image above shows Brahe aged 40, from the Atlas Major by Johann Blaeu. With Ole Grell Emeritus Professor in Early Modern History at the Open University Adam Mosley Associate Professor of History at Swansea University and Emma Perkins Affiliate Scholar in the Department of History and Philosophy of Science at the University of Cambridge.

Melvyn Bragg and guests discuss the discovery made in 1911 by the Dutch physicist Heike Kamerlingh Onnes (1853-1926). He came to call it Superconductivity and it is a set of physical properties that nobody predicted and that none, since, have fully explained. When he lowered the temperature of mercury close to absolute zero and ran an electrical current through it, Kamerlingh Onnes found not that it had low resistance but that it had no resistance. Later, in addition, it was noticed that a superconductor expels its magnetic field. In the century or more that has followed, superconductors have already been used to make MRI scanners and to speed particles through the Large Hadron Collider and they may perhaps bring nuclear fusion a little closer (a step that could be world changing). The image above is from a photograph taken by Stephen Blundell of a piece of superconductor levitating above a magnet. With Nigel Hussey Professor of Experimental Condensed Matter Physics at the University of Bristol and Radbout University Suchitra Sebastian Professor of Physics at the Cavendish Laboratory at the University of Cambridge And Stephen Blundell Professor of Physics at the University of Oxford and Fellow of Mansfield College Producer: Simon Tillotson

Melvyn Bragg and guests discuss the voyage of HMS Challenger which set out from Portsmouth in 1872 with a mission a to explore the ocean depths around the world and search for new life. The scale of the enterprise was breath taking and, for its ambition, it has since been compared to the Apollo missions. The team onboard found thousands of new species, proved there was life on the deepest seabeds and plumbed the Mariana Trench five miles below the surface. Thanks to telegraphy and mailboats, its vast discoveries were shared around the world even while Challenger was at sea, and they are still being studied today, offering insights into the ever-changing oceans that cover so much of the globe and into the health of our planet. The image above is from the journal of Pelham Aldrich R.N. who served on the Challenger Surveying Expedition from 1872-5. With Erika Jones Curator of Navigation and Oceanography at Royal Museums Greenwich Sam Robinson Southampton Marine and Maritime Institute Research Fellow at the University of Southampton And Giles Miller Principal Curator of Micropalaeontology at the Natural History Museum London Producer: Simon Tillotson

Melvyn Bragg and guests discuss one of the greatest changes in the history of life on Earth. Around 400 million years ago some of our ancestors, the fish, started to become a little more like humans. At the swampy margins between land and water, some fish were turning their fins into limbs, their swim bladders into lungs and developed necks and eventually they became tetrapods, the group to which we and all animals with backbones and limbs belong. After millions of years of this transition, these tetrapod descendants of fish were now ready to leave the water for a new life of walking on land, and with that came an explosion in the diversity of life on Earth. The image above is a representation of Tiktaalik Roseae, a fish with some features of a tetrapod but not one yet, based on a fossil collected in the Canadian Arctic. With Emily Rayfield Professor of Palaeobiology at the University of Bristol Michael Coates Chair and Professor of Organismal Biology and Anatomy at the University of Chicago And Steve Brusatte Professor of Palaeontology and Evolution at the University of Edinburgh Producer: Simon Tillotson

Melvyn Bragg and guests discuss an atomic particle that's become inseparable from modernity. JJ Thomson discovered the electron 125 years ago, so revealing that atoms, supposedly the smallest things, were made of even smaller things. He pictured them inside an atomic ball like a plum pudding, with others later identifying their place outside the nucleus - and it is their location on the outer limit that has helped scientists learn so much about electrons and with electrons. We can use electrons to reveal the secrets of other particles and, while electricity exists whether we understand electrons or not, the applications of electricity and electrons grow as our knowledge grows. Many questions, though, remain unanswered. With Victoria Martin Professor of Collider Physics at the University of Edinburgh Harry Cliff Research Fellow in Particle Physics at the University of Cambridge And Frank Close Professor Emeritus of Theoretical Physics and Fellow Emeritus at Exeter College at the University of Oxford Producer: Simon Tillotson

Melvyn Bragg and guests discuss the abrupt transformation of stars after shining brightly for millions or billions of years, once they lack the fuel to counter the force of gravity. Those like our own star, the Sun, become red giants, expanding outwards and consuming nearby planets, only to collapse into dense white dwarves. The massive stars, up to fifty times the mass of the Sun, burst into supernovas, visible from Earth in daytime, and become incredibly dense neutron stars or black holes. In these moments of collapse, the intense heat and pressure can create all the known elements to form gases and dust which may eventually combine to form new stars, new planets and, as on Earth, new life. The image above is of the supernova remnant Cassiopeia A, approximately 10,000 light years away, from a once massive star that died in a supernova explosion that was first seen from Earth in 1690 With Martin Rees Astronomer Royal, Fellow of Trinity College, Cambridge Carolin Crawford Emeritus Member of the Institute of Astronomy and Emeritus Fellow of Emmanuel College, University of Cambridge And Mark Sullivan Professor of Astrophysics at the University of Southampton Producer: Simon Tillotson

Melvyn Bragg and guests discuss one of our ancestors, Homo erectus, who thrived on Earth for around two million years whereas we, Homo sapiens, emerged only in the last three hundred thousand years. Homo erectus, or Upright Man, spread from Africa to Asia and it was on the Island of Java that fossilised remains were found in 1891 in an expedition led by Dutch scientist Eugène Dubois. Homo erectus people adapted to different habitats, ate varied food, lived in groups, had stamina to outrun their prey; and discoveries have prompted many theories on the relationship between their diet and the size of their brains, on their ability as seafarers, on their creativity and on their ability to speak and otherwise communicate. The image above is from a diorama at the Moesgaard Museum in Denmark, depicting the Turkana Boy referred to in the programme. With Peter Kjærgaard Director of the Natural History Museum of Denmark and Professor of Evolutionary History at the University of Copenhagen José Joordens Senior Researcher in Human Evolution at Naturalis Biodiversity Centre and Professor of Human Evolution at Maastricht University And Mark Maslin Professor of Earth System Science at University College London Producer: Simon Tillotson

Melvyn Bragg and guests discuss the study of earthquakes. A massive earthquake in 1755 devastated Lisbon, and this disaster helped inspire a new science of seismology which intensified after San Francisco in 1906 and advanced even further with the need to monitor nuclear tests around the world from 1945 onwards. While we now know so much more about what lies beneath the surface of the Earth, and how rocks move and crack, it remains impossible to predict when earthquakes will happen. Thanks to seismology, though, we have a clearer idea of where earthquakes will happen and how to make some of them less hazardous to lives and homes. With Rebecca Bell Senior lecturer in Geology and Geophysics at Imperial College London Zoe Mildon Lecturer in Earth Sciences and Future Leaders Fellow at the University of Plymouth And James Hammond Reader in Geophysics at Birkbeck, University of London Producer: Simon Tillotson

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Melvyn Bragg and guests discuss William Herschel (1738 – 1822) and his sister Caroline Herschel (1750 – 1848) who were born in Hanover and made their reputation in Britain. William was one of the most eminent astronomers in British history. Although he started life as a musician, as a young man he became interested in studying the night sky. With an extraordinary talent, he constructed telescopes that were able to see further and more clearly than any others at the time. He is most celebrated today for discovering the planet Uranus and detecting what came to be known as infrared radiation. Caroline also became a distinguished astronomer, discovering several comets and collaborating with her brother. With Monica Grady Professor of Planetary and Space Sciences at the Open University Carolin Crawford Institute of Astronomy, Cambridge and an Emeritus Fellow of Emmanuel College, University of Cambridge And Jim Bennett Keeper Emeritus at the Science Museum in London. Studio producer: John Goudie

Melvyn Bragg and guests discuss the simple animals which informed Charles Darwin's first book, The Structure and Distribution of Coral Reefs, published in 1842. From corals, Darwin concluded that the Earth changed very slowly and was not fashioned by God. Now coral reefs, which some liken to undersea rainforests, are threatened by human activity, including fishing, pollution and climate change. With Steve Jones Senior Research Fellow in Genetics at University College London Nicola Foster Lecturer in Marine Biology at the University of Plymouth And Gareth Williams Associate Professor in Marine Biology at Bangor University School of Ocean Sciences Producer Simon Tilllotson.

Melvyn Bragg and guests discuss the race to build an atom bomb in the USA during World War Two. Before the war, scientists in Germany had discovered the potential of nuclear fission and scientists in Britain soon argued that this could be used to make an atom bomb, against which there could be no defence other than to own one. The fear among the Allies was that, with its head start, Germany might develop the bomb first and, unmatched, use it on its enemies. The USA took up the challenge in a huge engineering project led by General Groves and Robert Oppenheimer and, once the first bomb had been exploded at Los Alamos in July 1945, it appeared inevitable that the next ones would be used against Japan with devastating results. The image above is of Robert Oppenheimer and General Groves examining the remains of one the bases of the steel test tower, at the atomic bomb Trinity Test site, in September 1945. With Bruce Cameron Reed The Charles A. Dana Professor of Physics Emeritus at Alma College, Michigan Cynthia Kelly Founder and President of the Atomic Heritage Foundation And Frank Close Emeritus Professor of Theoretical Physics at the University of Oxford and a Fellow of Exeter College, Oxford Producer: Simon Tillotson

Melvyn Bragg and guests discuss the remarkable diversity of the animals that dominated life on land in the Triassic, before the rise of the dinosaurs in the Jurassic, and whose descendants are often described wrongly as 'living fossils'. For tens of millions of years, the ancestors of alligators and Nile crocodiles included some as large as a bus, some running on two legs like a T Rex and some that lived like whales. They survived and rebounded from a series of extinction events but, while the range of habitats of the dinosaur descendants such as birds covers much of the globe, those of the crocodiles have contracted, even if the animals themselves continue to evolve today as quickly as they ever have. With Anjali Goswami Research Leader in Life Sciences and Dean of Postgraduate Education at the Natural History Museum Philip Mannion Lecturer in the Department of Earth Sciences at University College London And Steve Brusatte Professor of Palaeontology and Evolution at the University of Edinburgh Producer Simon Tillotson

Melvyn Bragg and guests discuss the search for Longitude while at sea. Following efforts by other maritime nations, the British Government passed the Longitude Act in 1714 to reward anyone who devised reliable means for ships to determine their longitude at sea. Mariners could already calculate how far they were north or south, the Latitude, using the Pole Star, but voyaging across the Atlantic to the Caribbean was much less predictable as navigators could not be sure how far east or west they were, a particular problem when heading for islands. It took fifty years of individual genius and collaboration in Britain and across Europe, among astronomers, clock makers, mathematicians and sailors, for the problem to be resolved. With Rebekah Higgitt Principal Curator of Science at National Museums Scotland Jim Bennett Keeper Emeritus at the Science Museum And Simon Schaffer Professor of History and Philosophy of Science at the University of Cambridge Producer: Simon Tillotson

Melvyn Bragg and guests discuss Laplace (1749-1827) who was a giant in the world of mathematics both before and after the French Revolution. He addressed one of the great questions of his age, raised but side-stepped by Newton: was the Solar System stable, or would the planets crash into the Sun, as it appeared Jupiter might, or even spin away like Saturn threatened to do? He advanced ideas on probability, long the preserve of card players, and expanded them out across science; he hypothesised why the planets rotate in the same direction; and he asked if the Universe was deterministic, so that if you knew everything about all the particles then you could predict the future. He also devised the metric system and reputedly came up with the name 'metre'. With Marcus du Sautoy Simonyi Professor for the Public Understanding of Science and Professor of Mathematics at the University of Oxford Timothy Gowers Professor of Mathematics at the College de France And Colva Roney-Dougal Professor of Pure Mathematics at the University of St Andrews Producer: Simon Tillotson

Melvyn Bragg and guests discuss the devastating mass extinctions of the Late Devonian Period, roughly 370 million years ago, when around 70 percent of species disappeared. Scientists are still trying to establish exactly what happened, when and why, but this was not as sudden as when an asteroid hits Earth. The Devonian Period had seen the first trees and soils and it had such a diversity of sea life that it’s known as the Age of Fishes, some of them massive and armoured, and, in one of the iconic stages in evolution, some of them moving onto land for the first time. One of the most important theories for the first stage of this extinction is that the new soils washed into oceans, leading to algal blooms that left the waters without oxygen and suffocated the marine life. The image above is an abstract group of the huge, armoured Dunkleosteus fish, lost in the Late Devonian Extinction With Jessica Whiteside Associate Professor of Geochemistry in the Department of Ocean and Earth Science at the University of Southampton David Bond Professor of Geology at the University of Hull And Mike Benton Professor of Vertebrate Paleontology at the School of Life Sciences, University of Bristol.

Melvyn Bragg and guests discuss one of the outstanding French mathematicians and natural philosophers of the 18th Century, celebrated across Europe. Emilie du Châtelet, 1706-49, created a translation of Newton’s Principia from Latin into French that helped spread the light of mathematics on the emerging science, and her own book Institutions de Physique, with its lessons on physics, was welcomed as profound. She had the privileges of wealth and aristocracy, yet had to fight to be taken seriously as an intellectual in a world of ideas that was almost exclusively male. With Patricia Fara Emeritus Fellow of Clare College, Cambridge David Wootton Anniversary Professor of History at the University of York And Judith Zinsser Professor Emerita of History at Miami University of Ohio and biographer of Emilie du Châtelet. Producer: Simon Tillotson

Melvyn Bragg and guests discuss solar eclipses, some of life’s most extraordinary moments, when day becomes night and the stars come out before day returns either all too soon or not soon enough, depending on what you understand to be happening. In ancient China, for example, there was a story that a dragon was eating the sun and it had to be scared away by banging pots and pans if the sun were to return. Total lunar eclipses are more frequent and last longer, with a blood moon coloured red like a sunrise or sunset. Both events have created the chance for scientists to learn something remarkable, from the speed of light, to the width of the Atlantic, to the roundness of Earth, to discovering helium and proving Einstein’s Theory of General Relativity. With Carolin Crawford Public Astronomer based at the Institute of Astronomy, University of Cambridge and a fellow of Emmanuel College Frank Close Emeritus Professor of Physics at the University of Oxford And Lucie Green Professor of Physics and a Royal Society University Research Fellow at Mullard Space Science Laboratory at University College London Producers: Simon Tillotson and Julia Johnson

Melvyn Bragg and guests discuss Alan Turing (1912-1954) whose 1936 paper On Computable Numbers effectively founded computer science. Immediately recognised by his peers, his wider reputation has grown as our reliance on computers has grown. He was a leading figure at Bletchley Park in the Second World War, using his ideas for cracking enemy codes, work said to have shortened the war by two years and saved millions of lives. That vital work was still secret when Turing was convicted in 1952 for having a sexual relationship with another man for which he was given oestrogen for a year, or chemically castrated. Turing was to kill himself two years later. The immensity of his contribution to computing was recognised in the 1960s by the creation of the Turing Award, known as the Nobel of computer science, and he is to be the new face on the £50 note. With Leslie Ann Goldberg Professor of Computer Science and Fellow of St Edmund Hall, University of Oxford Simon Schaffer Professor of the History of Science at the University of Cambridge and Fellow of Darwin College And Andrew Hodges Biographer of Turing and Emeritus Fellow of Wadham College, Oxford Producer: Simon Tillotson

Melvyn Bragg and guests discuss the theoretical physicist Dirac (1902-1984), whose achievements far exceed his general fame. To his peers, he was ranked with Einstein and, when he moved to America in his retirement, he was welcomed as if he were Shakespeare. Born in Bristol, he trained as an engineer before developing theories in his twenties that changed the understanding of quantum mechanics, bringing him a Nobel Prize in 1933 which he shared with Erwin Schrödinger. He continued to make deep contributions, bringing abstract maths to physics, beyond predicting anti-particles as he did in his Dirac Equation. With Graham Farmelo Biographer of Dirac and Fellow at Churchill College, Cambridge Valerie Gibson Professor of High Energy Physics at the University of Cambridge and Fellow of Trinity College And David Berman Professor of Theoretical Physics at Queen Mary University of London Producer: Simon Tillotson

Melvyn Bragg and guests discuss the origins of horses, from their dog sized ancestors to their proliferation in the New World until hunted to extinction, their domestication in Asia and their development since. The genetics of the modern horse are the most studied of any animal, after humans, yet it is still uncertain why they only have one toe on each foot when their wider family had more, or whether speed or stamina has been more important in their evolution. What is clear, though, is that when humans first chose to ride horses, as well as eat them, the future of both species changed immeasurably. With Alan Outram Professor of Archaeological Science at the University of Exeter Christine Janis Honorary Professor in Palaeobiology at the University of Bristol and Professor Emerita in Ecology and Evolutionary Biology at Brown University And John Hutchinson Professor in Evolutionary Biomechanics at the Royal Veterinary College Producer: Simon Tillotson

Melvyn Bragg and guests discuss the flow of particles from the outer region of the Sun which we observe in the Northern and Southern Lights, interacting with Earth's magnetosphere, and in comet tails that stream away from the Sun regardless of their own direction. One way of defining the boundary of the solar system is where the pressure from the solar wind is balanced by that from the region between the stars, the interstellar medium. Its existence was suggested from the C19th and Eugene Parker developed the theory of it in the 1950s and it has been examined and tested by a series of probes in C20th up to today, with more planned. With Andrew Coates Professor of Physics and Deputy Director in charge of the Solar System at the Mullard Space Science Laboratory, University College London Helen Mason OBE Reader in Solar Physics at the Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Fellow at St Edmund's College And Tim Horbury Professor of Physics at Imperial College London Producer: Simon Tillotson

Melvyn Bragg and guests discuss what happens when parents from different species have offspring, despite their genetic differences. In some cases, such as the zebra/donkey hybrid in the image above, the offspring are usually infertile but in others the genetic change can lead to new species with evolutionary advantages. Hybrids can occur naturally, yet most arise from human manipulation and Darwin's study of plant and animal domestication informed his ideas on natural selection. With Sandra Knapp Tropical Botanist at the Natural History Museum Nicola Nadeau Lecturer in Evolutionary Biology at the University of Sheffield And Steve Jones Senior Research Fellow in Genetics at University College London Producer: Simon Tillotson

Melvyn Bragg and guests discuss the work and ideas of Dorothy Crowfoot Hodgkin (1910-1994), awarded the Nobel Prize in Chemistry in 1964 for revealing the structures of vitamin B12 and penicillin and who later determined the structure of insulin. She was one of the pioneers of X-ray crystallography and described by a colleague as 'a crystallographers' crystallographer'. She remains the only British woman to have won a Nobel in science, yet rejected the idea that she was a role model for other women, or that her career was held back because she was a woman. She was also the first woman since Florence Nightingale to receive the Order of Merit, and was given the Lenin Peace Prize in recognition of her efforts to bring together scientists from the East and West in pursuit of nuclear disarmament. With Georgina Ferry Science writer and biographer of Dorothy Hodgkin Judith Howard Professor of Chemistry at Durham University and Patricia Fara Fellow of Clare College, Cambridge Producer: Simon Tillotson

Melvyn Bragg and guests discuss how scientists sought to understand the properties of gases and the relationship between pressure and volume, and what that search unlocked. Newton theorised that there were static particles in gases that pushed against each other all the harder when volume decreased, hence the increase in pressure. Those who argued that molecules moved, and hit each other, were discredited until James Maxwell and Ludwig Boltzmann used statistics to support this kinetic theory. Ideas about atoms developed in tandem with this, and it came as a surprise to scientists in C20th that the molecules underpinning the theory actually existed and were not simply thought experiments. The image above is of Ludwig Boltzmann from a lithograph by Rudolf Fenzl, 1898 With Steven Bramwell Professor of Physics at University College London Isobel Falconer Reader in History of Mathematics at the University of St Andrews and Ted Forgan Emeritus Professor of Physics at the University of Birmingham Producer: Simon Tillotson

Melvyn Bragg and guests discuss theories about the origins of teeth in vertebrates, and what we can learn from sharks in particular and their ancestors. Great white sharks can produce up to 100,000 teeth in their lifetimes. For humans, it is closer to a mere 50 and most of those have to last from childhood. Looking back half a billion years, though, the ancestors of sharks and humans had no teeth in their mouths at all, nor jaws. They were armoured fish, sucking in their food. The theory is that either their tooth-like scales began to appear in mouths as teeth, or some of their taste buds became harder. If we knew more about that, and why sharks can regenerate their teeth, then we might learn how humans could grow new teeth in later lives. With Gareth Fraser Assistant Professor in Biology at the University of Florida Zerina Johanson Merit Researcher in the Department of Earth Sciences at the Natural History Museum and Philip Donoghue Professor of Palaeobiology at the University of Bristol Producer: Simon Tillotson

Melvyn Bragg and guests discuss how members of the same species send each other invisible chemical signals to influence the way they behave. Pheromones are used by species across the animal kingdom in a variety of ways, such as laying trails to be followed, to raise the alarm, to scatter from predators, to signal dominance and to enhance attractiveness and, in honey bees, even direct development into queen or worker. The image above is of male and female ladybirds that have clustered together in response to pheromones. With Tristram Wyatt Senior Research Fellow at the Department of Zoology at the University of Oxford Jane Hurst William Prescott Professor of Animal Science at the University of Liverpool and Francis Ratnieks Professor of Apiculture and Head of the Laboratory of Apiculture and Social Insects at the University of Sussex Producer: Simon Tillotson

Melvyn Bragg and guests discuss the remarkable achievement of Aristotle (384-322BC) in the realm of biological investigation, for which he has been called the originator of the scientific study of life. Known mainly as a philosopher and the tutor for Alexander the Great, who reportedly sent him animal specimens from his conquests, Aristotle examined a wide range of life forms while by the Sea of Marmara and then on the island of Lesbos. Some ideas, such as the the spontaneous generation of flies, did not survive later scrutiny, yet his influence was extraordinary and his work was unequalled until the early modern period. The image above is of the egg and embryo of a dogfish, one of the animals Aristotle described accurately as he recorded their development. With Armand Leroi Professor of Evolutionary Development Biology at Imperial College London Myrto Hatzimichali Lecturer in Classics at the University of Cambridge And Sophia Connell Lecturer in Philosophy at Birkbeck, University of London Producer: Simon Tillotson

Melvyn Bragg and guests discuss the ideas and life of one of the greatest mathematicians of the 20th century, Emmy Noether. Noether’s Theorem is regarded as one of the most important mathematical theorems, influencing the evolution of modern physics. Born in 1882 in Bavaria, Noether studied mathematics at a time when women were generally denied the chance to pursue academic careers and, to get round objections, she spent four years lecturing under a male colleague’s name. In the 1930s she faced further objections to her teaching, as she was Jewish, and she left for the USA when the Nazis came to power. Her innovative ideas were to become widely recognised and she is now considered to be one of the founders of modern algebra. With Colva Roney Dougal Professor of Pure Mathematics at the University of St Andrews David Berman Professor in Theoretical Physics at Queen Mary, University of London Elizabeth Mansfield Professor of Mathematics at the University of Kent Producer: Simon Tillotson

Melvyn Bragg and guests discuss the planet Venus which is both the morning star and the evening star, rotates backwards at walking speed and has a day which is longer than its year. It has long been called Earth’s twin, yet the differences are more striking than the similarities. Once imagined covered with steaming jungles and oceans, we now know the surface of Venus is 450 degrees celsius, and the pressure there is 90 times greater than on Earth, enough to crush an astronaut. The more we learn of it, though, the more we learn of our own planet, such as whether Earth could become more like Venus in some ways, over time. With Carolin Crawford Public Astronomer at the Institute of Astronomy and Fellow of Emmanuel College, University of Cambridge Colin Wilson Senior Research Fellow in Planetary Science at the University of Oxford And Andrew Coates Professor of Physics at Mullard Space Science Laboratory, University College London Produced by: Simon Tillotson and Julia Johnson

Melvyn Bragg and guests discuss the properties of atoms or molecules with a single unpaired electron, which tend to be more reactive, keen to seize an electron to make it a pair. In the atmosphere, they are linked to reactions such as rusting. Free radicals came to prominence in the 1950s with the discovery that radiation poisoning operates through free radicals, as it splits water molecules and produces a very reactive hydroxyl radical which damages DNA and other molecules in the cell. There is also an argument that free radicals are a byproduct of normal respiration and over time they cause an accumulation of damage that is effectively the process of ageing. For all their negative associations, free radicals play an important role in signalling and are also linked with driving cell division, both cancer and normal cell division, even if they tend to become damaging when there are too many of them. With Nick Lane Professor of Evolutionary Biochemistry at University College London Anna Croft Associate Professor at the Department of Chemical and Environmental Engineering at the University of Nottingham And Mike Murphy Professor of Mitochondrial Redox Biology at Cambridge University Producer: Simon Tillotson

Melvyn Bragg and guests discuss the history of real and imagined machines that appear to be living, and the questions they raise about life and creation. Even in myth they are made by humans, not born. The classical Greeks built some and designed others, but the knowledge of how to make automata and the principles behind them was lost in the Latin Christian West, remaining in the Greek-speaking and Arabic-speaking world. Western travellers to those regions struggled to explain what they saw, attributing magical powers. The advance of clockwork raised further questions about what was distinctly human, prompting Hobbes to argue that humans were sophisticated machines, an argument explored in the Enlightenment and beyond. The image above is Jacques de Vaucanson's mechanical duck (1739), which picked up grain, digested and expelled it. If it looks like a duck... with Simon Schaffer Professor of History of Science at Cambridge University Elly Truitt Associate Professor of Medieval History at Bryn Mawr College And Franziska Kohlt Doctoral Researcher in English Literature and the History of Science at the University of Oxford Producer: Simon Tillotson

Melvyn Bragg and guests discuss how some bats, dolphins and other animals emit sounds at high frequencies to explore their environments, rather than sight. This was such an unlikely possibility, to natural historians from C18th onwards, that discoveries were met with disbelief even into the C20th; it was assumed that bats found their way in the dark by touch. Not all bats use echolocation, but those that do have a range of frequencies for different purposes and techniques for preventing themselves becoming deafened by their own sounds. Some prey have evolved ways of detecting when bats are emitting high frequencies in their direction, and some fish have adapted to detect the sounds dolphins use to find them. With Kate Jones Professor of Ecology and Biodiversity at University College London Gareth Jones Professor of Biological Sciences at the University of Bristol And Dean Waters Lecturer in the Environment Department at the University of York Producer: Simon Tillotson.

Melvyn Bragg and guests discuss the discovery and growing understanding of the Proton, formed from three quarks close to the Big Bang and found in the nuclei of all elements. The positive charges they emit means they attract the fundamental particles of negatively charged electrons, an attraction that leads to the creation of atoms which in turn leads to chemistry, biology and life itself. The Sun (in common with other stars) is a fusion engine that turn protons by a series of processes into helium, emitting energy in the process, with about half of the Sun's protons captured so far. Hydrogen atoms, stripped of electrons, are single protons which can be accelerated to smash other nuclei and have applications in proton therapy. Many questions remain, such as why are electrical charges for protons and electrons so perfectly balanced? With Frank Close Professor Emeritus of Physics at the University of Oxford Helen Heath Reader in Physics at the University of Bristol And Simon Jolly Lecturer in High Energy Physics at University College London Producer: Simon Tillotson.

In a programme first broadcast on April 12th 2018, Melvyn Bragg and guests discuss the contribution of George Stephenson (1781-1848) and his son Robert (1803-59) to the development of the railways in C19th. George became known as The Father of Railways and yet arguably Robert's contribution was even greater, with his engineering work going far beyond their collaboration. Robert is credited with the main role in the design of their locomotives. George had worked on stationary colliery steam engines and, with Robert, developed the moving steam engine Locomotion No1 for the Stockton and Darlington Railway in 1825. They produced the Rocket for the Rainhill Trials on the Liverpool and Manchester Railway in 1829. From there, the success of their designs and engineering led to the expansion of railways across Britain and around the world. with Dr Michael Bailey Railway historian and editor of the most recent biography of Robert Stephenson Julia Elton Past President of the Newcomen Society for the History of Engineering and Technology and Colin Divall Professor Emeritus of Railway Studies at the University of York Producer: Simon Tillotson. This programme is a repeat

Melvyn Bragg and guests discuss the pioneering scientist Rosalind Franklin (1920 - 1958). During her distinguished career, Franklin carried out ground-breaking research into coal and viruses but she is perhaps best remembered for her investigations in the field of DNA. In 1952 her research generated a famous image that became known as Photograph 51. When the Cambridge scientists Francis Crick and James Watson saw this image, it enabled them the following year to work out that DNA has a double-helix structure, one of the most important discoveries of modern science. Watson, Crick and Franklin's colleague Maurice Wilkins received a Nobel Prize in 1962 for this achievement but Franklin did not and today many people believe that Franklin has not received enough recognition for her work. With: Patricia Fara President of the British Society for the History of Science Jim Naismith Interim lead of the Rosalind Franklin Institute, Director of the Research Complex at Harwell and Professor at the University of Oxford Judith Howard Professor of Chemistry at Durham University Producer: Victoria Brignell.

Melvyn Bragg and guests discuss fungi. These organisms are not plants or animals but a kingdom of their own. Millions of species of fungi live on the Earth and they play a crucial role in ecosystems, enabling plants to obtain nutrients and causing material to decay. Without fungi, life as we know it simply would not exist. They are also a significant part of our daily life, making possible the production of bread, wine and certain antibiotics. Although fungi brought about the colonisation of the planet by plants about 450 million years ago, some species can kill humans and devastate trees. With: Lynne Boddy Professor of Fungal Ecology at Cardiff University Sarah Gurr Professor of Food Security in the Biosciences Department at the University of Exeter David Johnson N8 Chair in Microbial Ecology at the University of Manchester Producer: Victoria Brignell.

The octopus, the squid, the nautilus and the cuttlefish are some of the most extraordinary creatures on this planet, intelligent and yet apparently unlike other life forms. They are cephalopods and are part of the mollusc family like snails and clams, and they have some characteristics in common with those. What sets them apart is the way members of their group can change colour, camouflage themselves, recognise people, solve problems, squirt ink, power themselves with jet propulsion and survive both on land, briefly, and in the deepest, coldest oceans. And, without bones or shells, they grow so rapidly they can outstrip their rivals when habitats change, making them the great survivors and adaptors of the animal world. With Louise Allcock Lecturer in Zoology at the National University of Ireland, Galway Paul Rodhouse Emeritus Fellow of the British Antarctic Survey and Jonathan Ablett Senior Curator of Molluscs at the Natural History Museum Producer: Simon Tillotson.

In a programme first broadcast in 2017, Melvyn Bragg and guests discuss Gauss (1777-1855), widely viewed as one of the greatest mathematicians of all time. He was a child prodigy, correcting his father's accounts before he was 3, dumbfounding his teachers with the speed of his mental arithmetic, and gaining a wealthy patron who supported his education. He wrote on number theory when he was 21, with his Disquisitiones Arithmeticae, which has influenced developments since. Among his achievements, he was the first to work out how to make a 17-sided polygon, he predicted the orbit of the minor planet Ceres, rediscovering it, he found a way of sending signals along a wire, using electromagnetism, the first electromagnetic telegraph, and he advanced the understanding of parallel lines on curved surfaces. With Marcus du Sautoy Professor of Mathematics and Simonyi Professor for the Public Understanding of Science at the University of Oxford Colva Roney-Dougal Reader in Pure Mathematics at the University of St Andrews And Nick Evans Professor of Theoretical Physics at the University of Southampton Producer: Simon Tillotson.

In a programme first broadcast in 2017, Melvyn Bragg and guests discuss the development of theories about dinosaur feathers, following discoveries of fossils which show evidence of feathers. All dinosaurs were originally thought to be related to lizards - the word 'dinosaur' was created from the Greek for 'terrible lizard' - but that now appears false. In the last century, discoveries of fossils with feathers established that at least some dinosaurs were feathered and that some of those survived the great extinctions and evolved into the birds we see today. There are still many outstanding areas for study, such as what sorts of feathers they were, where on the body they were found, what their purpose was and which dinosaurs had them. With Mike Benton Professor of Vertebrate Palaeontology at the University of Bristol Steve Brusatte Reader and Chancellor's Fellow in Vertebrate Palaeontology at the University of Edinburgh and Maria McNamara Senior Lecturer in Geology at University College, Cork Producer: Simon Tillotson.

In a programme first broadcast in 2017, Melvyn Bragg and guests discuss why some birds migrate and others do not, how they select their destinations and how they navigate the great distances, often over oceans. For millennia, humans set their calendars to birds' annual arrivals, and speculated about what happened when they departed, perhaps moving deep under water, or turning into fish or shellfish, or hibernating while clinging to trees upside down. Ideas about migration developed in C19th when, in Germany, a stork was noticed with an African spear in its neck, indicating where it had been over the winter and how far it had flown. Today there are many ideas about how birds use their senses of sight and smell, and magnetic fields, to find their way, and about why and how birds choose their destinations and many questions. Why do some scatter and some flock together, how much is instinctive and how much is learned, and how far do the benefits the migrating birds gain outweigh the risks they face? With Barbara Helm Reader at the Institute of Biodiversity, Animal Health and Comparative Medicine at the University of Glasgow Tim Guilford Professor of Animal Behaviour and Tutorial Fellow of Zoology at Merton College, Oxford and Richard Holland Senior Lecturer in Animal Cognition at Bangor University Producer: Simon Tillotson.

Melvyn Bragg and guests discuss enzymes, the proteins that control the speed of chemical reactions in living organisms. Without enzymes, these reactions would take place too slowly to keep organisms alive: with their actions as catalysts, changes which might otherwise take millions of years can happen hundreds of times a second. Some enzymes break down large molecules into smaller ones, like the ones in human intestines, while others use small molecules to build up larger, complex ones, such as those that make DNA. Enzymes also help keep cell growth under control, by regulating the time for cells to live and their time to die, and provide a way for cells to communicate with each other. With Nigel Richards Professor of Biological Chemistry at Cardiff University Sarah Barry Lecturer in Chemical Biology at King's College London And Jim Naismith Director of the Research Complex at Harwell Bishop Wardlaw Professor of Chemical Biology at the University of St Andrews Professor of Structural Biology at the University of Oxford Producer: Simon Tillotson.

Melvyn Bragg and guests discuss the life and work of Louis Pasteur (1822-1895) and his extraordinary contribution to medicine and science. It is said few people have saved more lives than Pasteur. A chemist, he showed that otherwise identical molecules could exist as 'left' and 'right-handed' versions and that molecules produced by living things were always left-handed. He proposed a germ theory to replace the idea of spontaneous generation. He discovered that microorganisms cause fermentation and disease. He began the process named after him, pasteurisation, heating liquids to 50-60 C to kill microbes. He saved the beer and wine industries in France when they were struggling with microbial contamination. He saved the French silk industry when he found a way of protecting healthy silkworm eggs from disease. He developed vaccines against anthrax and rabies and helped establish immunology. Many of his ideas were developed further after his lifetime, but one of his legacies was a charitable body, the Pasteur Institute, to continue research into infectious disease. With Andrew Mendelsohn Reader in the School of History at Queen Mary, University of London Anne Hardy Honorary Professor at the Centre for History in Public Health at the London School of Hygiene and Tropical Medicine and Michael Worboys Emeritus Professor in the History of Science, Technology and Medicine at the University of Manchester Producer: Simon Tillotson.

Melvyn Bragg and guests discuss the life and ideas of Wolfgang Pauli (1900-1958), whose Exclusion Principle is one of the key ideas in quantum mechanics. A brilliant physicist, at 21 Pauli wrote a review of Einstein's theory of general relativity and that review is still a standard work of reference today. The Pauli Exclusion Principle proposes that no two electrons in an atom can be at the same time in the same state or configuration, and it helps explain a wide range of phenomena such as the electron shell structure of atoms. Pauli went on to postulate the existence of the neutrino, which was confirmed in his lifetime. Following further development of his exclusion principle, Pauli was awarded the Nobel Prize in Physics in 1945 for his 'decisive contribution through his discovery of a new law of Nature'. He also had a long correspondence with Jung, and a reputation for accidentally breaking experimental equipment which was dubbed The Pauli Effect. With Frank Close Fellow Emeritus at Exeter College, University of Oxford Michela Massimi Professor of Philosophy of Science at the University of Edinburgh and Graham Farmelo Bye-Fellow of Churchill College, University of Cambridge Producer: Simon Tillotson.

Melvyn Bragg and guests discuss the high temperatures that marked the end of the Paleocene and start of the Eocene periods, about 50m years ago. Over c1000 years, global temperatures rose more than 5 C on average and stayed that way for c100,000 years more, with the surface of seas in the Arctic being as warm as those in the subtropics. There were widespread extinctions, changes in ocean currents, and there was much less oxygen in the sea depths. The rise has been attributed to an increase of carbon dioxide and methane in the atmosphere, though it is not yet known conclusively what the source of those gases was. One theory is that a rise in carbon dioxide, perhaps from volcanoes, warmed up the globe enough for warm water to reach the bottom of the oceans and so release methane from frozen crystals in the sea bed. The higher the temperature rose and the longer the water was warm, the more methane was released. Scientists have been studying a range of sources from this long period, from ice samples to fossils, to try to understand more about possible causes. With Dame Jane Francis Professor of Palaeoclimatology at the British Antarctic Survey Mark Maslin Professor of Palaeoclimatology at University College London And Tracy Aze Lecturer in Marine Micropaleontology at the University of Leeds Producer: Simon Tillotson.

Melvyn Bragg and guests discuss the Kuiper Belt, a vast region of icy objects at the fringes of our Solar System, beyond Neptune, in which we find the dwarf planet Pluto and countless objects left over from the origins of the solar system, some of which we observe as comets. It extends from where Neptune is, which is 30 times further out than the Earth is from the Sun, to about 500 times the Earth-Sun distance. It covers an immense region of space and it is the part of the Solar System that we know the least about, because it is so remote from us and has been barely detectable by Earth-based telescopes until recent decades. Its existence was predicted before it was known, and study of the Kuiper Belt, and how objects move within it, has led to a theory that there may be a 9th planet far beyond Neptune. With Carolin Crawford Public Astronomer at the Institute of Astronomy and Fellow of Emmanuel College, University of Cambridge Monica Grady Professor of Planetary and Space Sciences at the Open University And Stephen Lowry Reader in Planetary and Space Sciences, University of Kent Producer: Simon Tillotson.

Melvyn Bragg and guests discuss the flourishing of maths in the early Islamic world, as thinkers from across the region developed ideas in places such as Baghdad's House of Wisdom. Among them were the Persians Omar Khayyam, who worked on equations, and Al-Khwarizmi, latinised as Algoritmi and pictured above, who is credited as one of the fathers of algebra, and the Jewish scholar Al-Samawal, who converted to Islam and worked on mathematical induction. As well as the new ideas, there were many advances drawing on Indian, Babylonian and Greek work and, thanks to the recording or reworking by mathematicians in the Islamic world, that broad range of earlier maths was passed on to western Europe for further study. With Colva Roney-Dougal Reader in Pure Mathematics at the University of St Andrews Peter Pormann Professor of Classics & Graeco-Arabic Studies at the University of Manchester And Jim Al-Khalili Professor of Physics at the University of Surrey Producer: Simon Tillotson.

Melvyn Bragg and guests discuss the relationship between parasites and hosts, where one species lives on or in another to the benefit of the parasite but at a cost to the host, potentially leading to disease or death of the host. Typical examples are mistletoe and trees, hookworms and vertebrates, cuckoos and other birds. In many cases the parasite species do so well in or on a particular host that they reproduce much faster and can adapt to changes more efficiently, and it is thought that almost half of all animal species have a parasitic stage in their lifetime. What techniques do hosts have to counter the parasites, and what impact do parasites have on the evolution of their hosts? With Steve Jones Emeritus Professor of Genetics at University College, London Wendy Gibson Professor of Protozoology at the University of Bristol and Kayla King Associate Professor in the Department of Zoology at the University of Oxford Producer: Simon Tillotson.

Melvyn Bragg and guests discuss the German astronomer Johannes Kepler (1571 - 1630). Although he is overshadowed today by Isaac Newton and Galileo, he is considered by many to be one of the greatest scientists in history. The three laws of planetary motion Kepler developed transformed people's understanding of the Solar System and laid the foundations for the revolutionary ideas Isaac Newton produced later. Kepler is also thought to have written one of the first works of science fiction. However, he faced a number of challenges. He had to defend his mother from charges of witchcraft, he had few financial resources and his career suffered as a result of his Lutheran faith. With David Wootton Professor of History at the University of York Ulinka Rublack Professor of Early Modern European History at the University of Cambridge and Fellow of St John's College Adam Mosley Associate Professor in the Department of History at Swansea University Producer: Victoria Brignell.

The scientist John Dalton was born in North England in 1766. Although he came from a relatively poor Quaker family, he managed to become one of the most celebrated scientists of his age. Through his work, he helped to establish Manchester as a place where not only products were made but ideas were born. His reputation during his lifetime was so high that unusually a statue was erected to him before he died. Among his interests were meteorology, gasses and colour blindness. However, he is most remembered today for his pioneering thinking in the field of atomic theory. With: Jim Bennett Former Director of the Museum of the History of Science at the University of Oxford and Keeper Emeritus at the Science Museum Aileen Fyfe Reader in British History at the University of St Andrews James Sumner Lecturer in the History of Technology at the Centre for the History of Science, Technology and Medicine at the University of Manchester Producer: Victoria Brignell.

Melvyn Bragg and guests discuss plasma, the fourth state of matter after solid, liquid and gas. As over ninety-nine percent of all observable matter in the Universe is plasma, planets like ours, with so little plasma and so much solid, liquid and gas, appear all the more remarkable. On the grand scale, plasma is what the Sun is made from and, when we look into the night sky, almost everything we can see with the naked eye is made of plasma. On the smallest scale, here on Earth, scientists make plasma to etch the microchips on which we rely for so much. Plasma is in the fluorescent light bulbs above our heads and, in laboratories around the world, it is the subject of tests to create, one day, an inexhaustible and clean source of energy from nuclear fusion. With Justin Wark Professor of Physics and Fellow of Trinity College at the University of Oxford Kate Lancaster Research Fellow for Innovation and Impact at the York Plasma Institute at the University of York and Bill Graham Professor of Physics at Queens University, Belfast Producer: Simon Tillotson.

In a programme first broadcast in 2016, Melvyn Bragg and guests discuss Zeno of Elea, a pre-Socratic philosopher from c490-430 BC whose paradoxes were described by Bertrand Russell as "immeasurably subtle and profound." The best known argue against motion, such as that of an arrow in flight which is at a series of different points but moving at none of them, or that of Achilles who, despite being the faster runner, will never catch up with a tortoise with a head start. Aristotle and Aquinas engaged with these, as did Russell, yet it is still debatable whether Zeno's Paradoxes have been resolved. With Marcus du Sautoy Professor of Mathematics and Simonyi Professor for the Public Understanding of Science at the University of Oxford Barbara Sattler Lecturer in Philosophy at the University of St Andrews and James Warren Reader in Ancient Philosophy at the University of Cambridge Producer: Simon Tillotson

Melvyn Bragg and guests discuss the development of photography in the 1830s, when techniques for 'drawing with light' evolved to the stage where, in 1839, both Louis Daguerre and William Henry Fox Talbot made claims for its invention. These followed the development of the camera obscura, and experiments by such as Thomas Wedgwood and Nicéphore Niépce, and led to rapid changes in the 1840s as more people captured images with the daguerreotype and calotype. These new techniques changed the aesthetics of the age and, before long, inspired claims that painting was now dead. With Simon Schaffer Professor of the History of Science at the University of Cambridge Elizabeth Edwards Emeritus Professor of Photographic History at De Montfort University And Alison Morrison-Low, Research Associate at National Museums Scotland Producer: Simon Tillotson.

Melvyn Bragg and guests discuss penicillin, discovered by Alexander Fleming in 1928. It is said he noticed some blue-green penicillium mould on an uncovered petri dish at his hospital laboratory, and that this mould had inhibited bacterial growth around it. After further work, Fleming filtered a broth of the mould and called that penicillin, hoping it would be useful as a disinfectant. Howard Florey and Ernst Chain later shared a Nobel Prize in Medicine with Fleming, for their role in developing a way of mass-producing the life-saving drug. Evolutionary theory predicted the risk of resistance from the start and, almost from the beginning of this 'golden age' of antibacterials, scientists have been looking for ways to extend the lifespan of antibiotics. With Laura Piddock Professor of Microbiology at the University of Birmingham Christoph Tang Professor of Cellular Pathology and Professorial Fellow at Exeter College at the University of Oxford And Steve Jones Emeritus Professor of Genetics at University College, London Producer: Simon Tillotson.

Melvyn Bragg and guests discuss Euclid's Elements, a mathematical text book attributed to Euclid and in use from its appearance in Alexandria, Egypt around 300 BC until modern times, dealing with geometry and number theory. It has been described as the most influential text book ever written. Einstein had a copy as a child, which he treasured, later saying "If Euclid failed to kindle your youthful enthusiasm, then you were not born to be a scientific thinker." With Marcus du Sautoy Professor of Mathematics and Simonyi Professor for the Public Understanding of Science at the University of Oxford Serafina Cuomo Reader in Roman History at Birkbeck University of London And June Barrow-Green Professor of the History of Mathematics at the Open University Producer: Simon Tillotson.

Melvyn Bragg and guests discuss the impact of the eruption of Mt Tambora, in 1815, on the Indonesian island of Sambawa. This was the largest volcanic eruption in recorded history and it had the highest death toll, devastating people living in the immediate area. Tambora has been linked with drastic weather changes in North America and Europe the following year, with frosts in June and heavy rains throughout the summer in many areas. This led to food shortages, which may have prompted westward migration in America and, in a Europe barely recovered from the Napoleonic Wars, led to widespread famine. With Clive Oppenheimer Professor of Volcanology at the University of Cambridge Jane Stabler Professor in Romantic Literature at the University of St Andrews And Lawrence Goldman Director of the Institute of Historical Research at the University of London Producer: Simon Tillotson.

Melvyn Bragg and guests discuss the neutron, one of the particles found in an atom's nucleus. Building on the work of Ernest Rutherford, the British physicist James Chadwick won the Nobel Prize for Physics for his discovery of the neutron in 1932. Neutrons play a fundamental role in the universe and their discovery was at the heart of developments in nuclear physics in the first half of the 20th century. With Val Gibson Professor of High Energy Physics at the University of Cambridge and fellow of Trinity College Andrew Harrison Chief Executive Officer of Diamond Light Source and Professor in Chemistry at the University of Edinburgh And Frank Close Professor Emeritus of Physics at the University of Oxford.

Melvyn Bragg and guests discuss the life and work of Robert Hooke (1635-1703) who worked for Robert Boyle and was curator of experiments at the Royal Society. The engraving of a flea, above, is taken from his Micrographia which caused a sensation when published in 1665. Sometimes remembered for his disputes with Newton, he studied the planets with telescopes and snowflakes with microscopes. He was an early proposer of a theory of evolution, discovered light diffraction with a wave theory to explain it and felt he was rarely given due credit for his discoveries. With David Wootton Anniversary Professor of History at the University of York Patricia Fara President Elect of the British Society for the History of Science And Rob Iliffe Professor of History of Science at Oxford University Producer: Simon Tillotson.

Melvyn Bragg and guests discuss the origins, development and uses of chromatography. In its basic form, it is familiar to generations of schoolchildren who put a spot of ink at the bottom of a strip of paper, dip it in water and then watch the pigments spread upwards, revealing their separate colours. Chemists in the 19th Century started to find new ways to separate mixtures and their work was taken further by Mikhail Tsvet, a Russian-Italian scientist who is often credited with inventing chromatography in 1900. The technique has become so widely used, it is now an integral part of testing the quality of air and water, the levels of drugs in athletes, in forensics and in the preparation of pharmaceuticals. With Andrea Sella Professor of Chemistry at University College London Apryll Stalcup Professor of Chemical Sciences at Dublin City University And Leon Barron Senior Lecturer in Forensic Science at King's College London.

Melvyn Bragg and guests discuss the planet Saturn with its rings of ice and rock and over 60 moons. In 1610, Galileo used an early telescope to observe Saturn, one of the brightest points in the night sky, but could not make sense of what he saw: perhaps two large moons on either side. When he looked a few years later, those supposed moons had disappeared. It was another forty years before Dutch scientist Christiaan Huygens solved the mystery, realizing the moons were really a system of rings. Successive astronomers added more detail, with the greatest leaps forward in the last forty years. The Pioneer 11 spacecraft and two Voyager missions have flown by, sending back the first close-up images, and Cassini is still there, in orbit, confirming Saturn, with its rings and many moons, as one of the most intriguing and beautiful planets in our Solar System. With Carolin Crawford Public Astronomer at the Institute of Astronomy and Fellow of Emmanuel College, University of Cambridge Michele Dougherty Professor of Space Physics at Imperial College London And Andrew Coates Deputy Director in charge of the Solar System at the Mullard Space Science Laboratory at UCL.

Melvyn Bragg and guests discuss the eminent 19th-century scientist Michael Faraday. Born into a poor working-class family, he received little formal schooling but became interested in science while working as a bookbinder's apprentice. He is celebrated today for carrying out pioneering research into the relationship between electricity and magnetism. Faraday showed that if a wire was turned in the presence of a magnet or a magnet was turned in relation to a wire, an electric current was generated. This ground-breaking discovery led to the development of the electric generator and ultimately to modern power stations. During his life he became the most famous scientist in Britain and he played a key role in founding the Royal Institution's Christmas lectures which continue today. With: Geoffrey Cantor Professor Emeritus of the History of Science at the University of Leeds Laura Herz Professor of Physics at the University of Oxford Frank James Professor of the History of Science at the Royal Institution Producer: Victoria Brignell.

Melvyn Bragg and his guests discuss the evolution and role of Circadian Rhythms, the so-called body clock that influences an organism's daily cycle of physical, behavioural and mental changes. The rhythms are generated within organisms and also in response to external stimuli, mainly light and darkness. They are found throughout the living world, from bacteria to plants, fungi to animals and, in humans, are noticed most clearly in sleep patterns. With Russell Foster Professor of Circadian Neuroscience at the University of Oxford Debra Skene Professor of Neuroendocrinology at the University of Surrey And Steve Jones Emeritus Professor of Genetics at University College London.

Melvyn Bragg and guests discuss the problem of P versus NP, which has a bearing on online security. There is a $1,000,000 prize on offer from the Clay Mathematical Institute for the first person to come up with a complete solution. At its heart is the question "are there problems for which the answers can be checked by computers, but not found in a reasonable time?" If the answer to that is yes, then P does not equal NP. However, if all answers can be found easily as well as checked, if only we knew how, then P equals NP. The area has intrigued mathematicians and computer scientists since Alan Turing, in 1936, found that it's impossible to decide in general whether an algorithm will run forever on some problems. Resting on P versus NP is the security of all online transactions which are currently encrypted: if it transpires that P=NP, if answers could be found as easily as checked, computers could crack passwords in moments. With Colva Roney-Dougal Reader in Pure Mathematics at the University of St Andrews Timothy Gowers Royal Society Research Professor in Mathematics at the University of Cambridge And Leslie Ann Goldberg Professor of Computer Science and Fellow of St Edmund Hall, University of Oxford Producer: Simon Tillotson.

Melvyn Bragg and guests discuss the rise of the idea of perpetual motion and its decline, in the 19th Century, with the Laws of Thermodynamics. For hundreds of years, some of the greatest names in science thought there might be machines that could power themselves endlessly. Leonardo Da Vinci tested the idea of a constantly-spinning wheel and Robert Boyle tried to recirculate water from a draining flask. Gottfried Leibniz supported a friend, Orffyreus, who claimed he had built an ever-rotating wheel. An increasing number of scientists voiced their doubts about perpetual motion, from the time of Galileo, but none could prove it was impossible. For scientists, the designs were a way of exploring the laws of nature. Others claimed their inventions actually worked, and promised a limitless supply of energy. It was not until the 19th Century that the picture became clearer, with the experiments of James Joule and Robert Mayer on the links between heat and work, and the establishment of the First and Second Laws of Thermodynamics. With Ruth Gregory Professor of Mathematics and Physics at Durham University Frank Close Professor Emeritus of Physics at the University of Oxford and Steven Bramwell Professor of Physics and former Professor of Chemistry at University College London Producer: Simon Tillotson.

In 1977, scientists in the submersible "Alvin" were exploring the deep ocean bed off the Galapagos Islands. In the dark, they discovered hydrothermal vents, like chimneys, from which superheated water flowed. Around the vents there was an extraordinary variety of life, feeding on microbes which were thriving in the acidity and extreme temperature of the vents. While it was already known that some microbes are extremophiles, thriving in extreme conditions, such as the springs and geysers of Yellowstone Park (pictured), that had not prepared scientists for what they now found. Since the "Alvin" discovery, the increased study of extremophile microbes has revealed much about what is and is not needed to sustain life on Earth and given rise to new theories about how and where life began. It has also suggested forms and places in which life might be found elsewhere in the Universe. With Monica Grady Professor of Planetary and Space Sciences at the Open University Ian Crawford Professor of Planetary Science and Astrobiology at Birkbeck University of London And Nick Lane Reader in Evolutionary Biochemistry at University College London Producer: Simon Tillotson.

While glass items have been made for at least 5,000 years, scientists are yet to explain, conclusively, what happens when the substance it's made from moves from a molten state to its hard, transparent phase. It is said to be one of the great unsolved problems in physics. While apparently solid, the glass retains certain properties of a liquid. At times, ways of making glass have been highly confidential; in Venice in the Middle Ages, disclosure of manufacturing techniques was a capital offence. Despite the complexity and mystery of the science of glass, glass technology has continued to advance from sheet glass to crystal glass, optical glass and prisms, to float glasses, chemical glassware, fibre optics and metal glasses. With: Dame Athene Donald Professor of Experimental Physics at the University of Cambridge and Master of Churchill College, Cambridge Jim Bennett Former Director of the Museum of the History of Science at the University of Oxford and Keeper Emeritus at the Science Museum Paul McMillan Professor of Chemistry at University College London Producer: Simon Tillotson.

Melvyn Bragg and his guests discuss the Earth's Core. The inner core is an extremely dense, solid ball of iron and nickel, the size of the Moon, while the outer core is a flowing liquid, the size of Mars. Thanks to the magnetic fields produced within the core, life on Earth is possible. The magnetosphere protects the Earth from much of the Sun's radiation and the flow of particles which would otherwise strip away the atmosphere. The precise structure of the core and its properties have been fascinating scientists from the Renaissance. Recent seismographs show the picture is even more complex than we might have imagined, with suggestions that the core is spinning at a different speed and on a different axis from the surface. With Stephen Blundell Professor of Physics and Fellow of Mansfield College at the University of Oxford Arwen Deuss Associate Professor in Seismology at Utrecht University and Simon Redfern Professor of Mineral Physics at the University of Cambridge Producer: Simon Tillotson.

Melvyn Bragg and his guests discuss the scientific achievements of the Curie family. In 1903 Marie and Pierre Curie shared a Nobel Prize in Physics with Henri Becquerel for their work on radioactivity, a term which Marie coined. Marie went on to win a Nobel in Chemistry eight years later; remarkably, her daughter Irène Joliot-Curie would later share a Nobel with her husband Frédéric Joliot-Curie for their discovery that it was possible to create radioactive materials in the laboratory. The work of the Curies added immensely to our knowledge of fundamental physics and paved the way for modern treatments for cancer and other illnesses. With: Patricia Fara Senior Tutor of Clare College, University of Cambridge Robert Fox Emeritus Professor of the History of Science at the University of Oxford Steven T Bramwell Professor of Physics and former Professor of Chemistry at University College London Producer: Simon Tillotson.

Melvyn Bragg and his guests discuss dark matter, the mysterious and invisible substance which is believed to make up most of the Universe. In 1932 the Dutch astronomer Jan Oort noticed that the speed at which galaxies moved was at odds with the amount of material they appeared to contain. He hypothesized that much of this 'missing' matter was simply invisible to telescopes. Today astronomers and particle physicists are still fascinated by the search for dark matter and the question of what it is. With Carolin Crawford Public Astronomer at the Institute of Astronomy, University of Cambridge and Gresham Professor of Astronomy Carlos Frenk Ogden Professor of Fundamental Physics and Director of the Institute for Computational Cosmology at the University of Durham Anne Green Reader in Physics at the University of Nottingham Producer: Simon Tillotson.

Melvyn Bragg and his guests discuss the photon, one of the most enigmatic objects in the Universe. Generations of scientists have struggled to understand the nature of light. In the late nineteenth century it seemed clear that light was an electromagnetic wave. But the work of physicists including Planck and Einstein shed doubt on this theory. Today scientists accept that light can behave both as a wave and a particle, the latter known as the photon. Understanding light in terms of photons has enabled the development of some of the most important technology of the last fifty years. With: Frank Close Professor Emeritus of Physics at the University of Oxford Wendy Flavell Professor of Surface Physics at the University of Manchester Susan Cartwright Senior Lecturer in Physics and Astronomy at the University of Sheffield. Producer: Thomas Morris.

Melvyn Bragg and guests discuss Behavioural Ecology, the scientific study of animal behaviour. What factors influence where and what an animal chooses to eat? Why do some animals mate for life whilst others are promiscuous? Behavioural ecologists approach questions like these using Darwin's theory of natural selection, along with ideas drawn from game theory and the economics of consumer choice. Scientists had always been interested in why animals behave as they do, but before behavioural ecology this area of zoology never got much beyond a collection of interesting anecdotes. Behavioural ecology gave researchers techniques for constructing rigorous mathematical models of how animals act under different circumstances, and for predicting how they will react if circumstances change. Behavioural ecology emerged as a branch of zoology in the second half of the 20th century and proponents say it revolutionized our understanding of animals in their environments. GUESTS Steve Jones, Emeritus Professor of Genetics at University College London Rebecca Kilner, Professor of Evolutionary Biology at the University of Cambridge John Krebs, Principal of Jesus College at the University of Oxford Producer: Luke Mulhall.

Melvyn Bragg and guests discuss Isambard Kingdom Brunel, the Victorian engineer responsible for bridges, tunnels and railways still in use today more than 150 years after they were built. Brunel represented the cutting edge of technological innovation in Victorian Britain, and his life gives us a window onto the social changes that accompanied the Industrial Revolution. Yet his work was not always successful, and his innovative approach to engineering projects was often greeted with suspicion from investors. Guests: Julia Elton, former President of the Newcomen Society for the History of Engineering and Technology Ben Marsden, Senior Lecturer in the School of Divinity, History and Philosophy at the University of Aberdeen Crosbie Smith, Professor of the History of Science at the University of Kent Producer: Luke Mulhall.

Melvyn Bragg and his guests discuss nuclear fusion, the process that powers stars. In the 1920s physicists predicted that it might be possible to generate huge amounts of energy by fusing atomic nuclei together, a reaction requiring enormous temperatures and pressures. Today we know that this complex reaction is what keeps the Sun shining. Scientists have achieved fusion in the laboratory and in nuclear weapons; today it is seen as a likely future source of limitless and clean energy. Guests: Philippa Browning, Professor of Astrophysics at the University of Manchester Steve Cowley, Chief Executive of the United Kingdom Atomic Energy Authority Justin Wark, Professor of Physics and fellow of Trinity College at the University of Oxford Producer: Thomas Morris.

Melvyn Bragg and his guests discuss Euler's number, also known as e. First discovered in the seventeenth century by the Swiss mathematician Jacob Bernoulli when he was studying compound interest, e is now recognised as one of the most important and interesting numbers in mathematics. Roughly equal to 2.718, e is useful in studying many everyday situations, from personal savings to epidemics. It also features in Euler's Identity, sometimes described as the most beautiful equation ever written. With: Colva Roney-Dougal Reader in Pure Mathematics at the University of St Andrews June Barrow-Green Senior Lecturer in the History of Maths at the Open University Vicky Neale Whitehead Lecturer at the Mathematical Institute and Balliol College at the University of Oxford Producer: Thomas Morris.

Melvyn Bragg and his guests discuss the Sun. The object that gives the Earth its light and heat is a massive ball of gas and plasma 93 million miles away. Thanks to the nuclear fusion reactions taking place at its core, the Sun has been shining for four and a half billion years. Its structure, and the processes that keep it burning, have fascinated astronomers for centuries. After the invention of the telescope it became apparent that the Sun is not a placid, steadily shining body but is subject to periodic changes in its appearance and eruptions of dramatic violence, some of which can affect us here on Earth. Recent space missions have revealed fascinating new insights into our nearest star. With: Carolin Crawford Gresham Professor of Astronomy and Fellow of Emmanuel College, Cambridge Yvonne Elsworth Poynting Professor of Physics at the University of Birmingham Louise Harra Professor of Solar Physics at UCL Mullard Space Science Laboratory Producer: Thomas Morris.

Melvyn Bragg and his guests discuss the life and work of Robert Boyle, a pioneering scientist and a founder member of the Royal Society. Born in Ireland in 1627, Boyle was one of the first natural philosophers to conduct rigorous experiments, laid the foundations of modern chemistry and derived Boyle's Law, describing the physical properties of gases. In addition to his experimental work he left a substantial body of writings about philosophy and religion; his piety was one of the most important factors in his intellectual activities, prompting a celebrated dispute with his contemporary Thomas Hobbes. With: Simon Schaffer Professor of the History of Science at the University of Cambridge Michael Hunter Emeritus Professor of History at Birkbeck College, University of London Anna Marie Roos Senior Lecturer in the History of Science and Medicine at the University of Lincoln Producer: Thomas Morris.

Melvyn Bragg and his guests discuss photosynthesis, the process by which green plants and many other organisms use sunlight to synthesise organic molecules. Photosynthesis arose very early in evolutionary history and has been a crucial driver of life on Earth. In addition to providing most of the food consumed by organisms on the planet, it is also responsible for maintaining atmospheric oxygen levels, and is thus almost certainly the most important chemical process ever discovered. With: Nick Lane Reader in Evolutionary Biochemistry at University College London Sandra Knapp Botanist at the Natural History Museum John Allen Professor of Biochemistry at Queen Mary, University of London. Producer: Thomas Morris

Melvyn Bragg and his guests discuss the science of matter and the states in which it can exist. Most people are familiar with the idea that a substance like water can exist in solid, liquid and gaseous forms. But as much as 99% of the matter in the universe is now believed to exist in a fourth state, plasma. Today scientists recognise a number of other exotic states or phases, such as glasses, gels and liquid crystals - many of them with useful properties that can be exploited. With: Andrea Sella Professor of Chemistry at University College London Athene Donald Professor of Experimental Physics at the University of Cambridge Justin Wark Professor of Physics and Fellow of Trinity College at the University of Oxford Producer: Thomas Morris.

Melvyn Bragg and his guests discuss the eye. Humans have been attempting to understand the workings and significance of the organ for at least 2500 years. Some ancient philosophers believed that the eye enabled creatures to see by emitting its own light. The function and structures of the eye became an area of particular interest to doctors in the Islamic Golden Age. In Renaissance Europe the work of thinkers including Kepler and Descartes revolutionised thinking about how the organ worked, but it took several hundred years for the eye to be thoroughly understood. Eyes have long attracted more than purely scientific interest, known even today as the 'windows on the soul'. With: Patricia Fara Senior Tutor of Clare College, University of Cambridge William Ayliffe Gresham Professor of Physic at Gresham College Robert Iliffe Professor of Intellectual History and History of Science at the University of Sussex Producer: Thomas Morris.

Melvyn Bragg and his guests discuss Social Darwinism. After the publication of Charles Darwin's masterpiece On the Origin of Species in 1859, some thinkers argued that Darwin's ideas about evolution could also be applied to human society. One thinker particularly associated with this movement was Darwin's near-contemporary Herbert Spencer, who coined the phrase 'survival of the fittest'. He argued that competition among humans was beneficial, because it ensured that only the healthiest and most intelligent individuals would succeed. Social Darwinism remained influential for several generations, although its association with eugenics and later adoption as an ideological position by Fascist regimes ensured its eventual downfall from intellectual respectability. With: Adam Kuper Centennial Professor of Anthropology at the LSE, University of London Gregory Radick Professor of History and Philosophy of Science at the University of Leeds Charlotte Sleigh Reader in the History of Science at the University of Kent. Producer: Thomas Morris.

Melvyn Bragg and his guests discuss Catastrophism, the idea that natural disasters have had a significant influence in moulding the Earth's geological features. In 1822 William Buckland, the first reader of Geology at the University of Oxford, published his famous Reliquae Diluvianae, in which he ascribed most of the fossil record to the effects of Noah's flood. Charles Lyell in his Principles of Geology challenged these writings, arguing that geological change was slow and gradual, and that the processes responsible could still be seen at work today - a school of thought known as Uniformitarianism. But in the 1970s the idea that natural catastrophes were a major factor in the Earth's geology was revived and given new respectability by the discovery of evidence of a gigantic asteroid impact 65 million years ago, believed by many to have resulted in the extinction of the dinosaurs. With: Andrew Scott Leverhulme Emeritus Fellow in the Department of Earth Sciences at Royal Holloway, University of London Jan Zalasiewicz Senior Lecturer in Geology at the University of Leicester Leucha Veneer Visiting Scholar at the Faculty of Life Sciences at the University of Manchester Producer: Thomas Morris.

Melvyn Bragg and his guests discuss complexity and how it can help us understand the world around us. When living beings come together and act in a group, they do so in complicated and unpredictable ways: societies often behave very differently from the individuals within them. Complexity was a phenomenon little understood a generation ago, but research into complex systems now has important applications in many different fields, from biology to political science. Today it is being used to explain how birds flock, to predict traffic flow in cities and to study the spread of diseases. With: Ian Stewart Emeritus Professor of Mathematics at the University of Warwick Jeff Johnson Professor of Complexity Science and Design at the Open University Professor Eve Mitleton-Kelly Director of the Complexity Research Group at the London School of Economics. Producer: Thomas Morris.

Melvyn Bragg and his guests discuss the development of the microscope, an instrument which has revolutionised our knowledge of the world and the organisms that inhabit it. In the seventeenth century the pioneering work of two scientists, the Dutchman Antonie van Leeuwenhoek and Robert Hooke in England, revealed the teeming microscopic world that exists at scales beyond the capabilities of the naked eye. The microscope became an essential component of scientific enquiry by the nineteenth century, but in the 1930s a German physicist, Ernst Ruska, discovered that by using a beam of electrons he could view structures much tinier than was possible using visible light. Today light and electron microscopy are among the most powerful tools at the disposal of modern science, and new techniques are still being developed. With: Jim Bennett Visiting Keeper at the Science Museum in London Sir Colin Humphreys Professor of Materials Science and Director of Research at the University of Cambridge Michelle Peckham Professor of Cell Biology at the University of Leeds Producer: Thomas Morris.

Melvyn Bragg and his guests discuss the Roman physician and medical theorist Galen. The most celebrated doctor in the ancient world, Galen was Greek by birth but spent most of his career in Rome, where he was personal physician to three Emperors. He was one of the most prolific authors of his age, and a sixth of all surviving ancient literature in Greek was written by him. Celebrated in his own lifetime, he was regarded as the preeminent medical authority for centuries after his death, both in the Arab world and in medieval Europe. It was only the discoveries of Renaissance science which removed Galen from his dominant position in the pantheon of medicine. With: Vivian Nutton Emeritus Professor of the History of Medicine at University College London Helen King Professor of Classical Studies at the Open University Caroline Petit Wellcome Trust Senior Research Fellow in Classics at the University of Warwick Producer: Thomas Morris.

Melvyn Bragg and his guests discuss exoplanets. Astronomers have speculated about the existence of planets beyond our solar system for centuries. Although strenuous efforts were made to find such planets orbiting distant stars, it was not until the 1990s that instruments became sophisticated enough to detect such remote objects. In 1992 Dale Frail and Aleksander Wolszczan discovered the first confirmed exoplanets: two planets orbiting the pulsar PSR B1257+12. Since then, astronomers have discovered more than 900 exoplanets, and are able to reach increasingly sophisticated conclusions about what they look like - and whether they might be able to support life. Recent data from experiments such as NASA's space telescope Kepler indicates that such planets may be far more common than previously suspected. With: Carolin Crawford Gresham Professor of Astronomy and a member of the Institute of Astronomy at the University of Cambridge Don Pollacco Professor of Astronomy at the University of Warwick Suzanne Aigrain Lecturer in Astrophysics at the University of Oxford and a Fellow of All Souls College. Producer: Thomas Morris.

Melvyn Bragg and his guests begin a new series of the programme with a discussion of the French polymath Blaise Pascal. Born in 1623, Pascal was a brilliant mathematician and scientist, inventing one of the first mechanical calculators and making important discoveries about fluids and vacuums while still a young man. In his thirties he experienced a religious conversion, after which he devoted most of his attention to philosophy and theology. Although he died in his late thirties, Pascal left a formidable legacy as a scientist and pioneer of probability theory, and as one of seventeenth century Europe's greatest writers. With: David Wootton Anniversary Professor of History at the University of York Michael Moriarty Drapers Professor of French at the University of Cambridge Michela Massimi Senior Lecturer in the Philosophy of Science at the University of Edinburgh. Producer: Thomas Morris.

Melvyn Bragg and his guests discuss the invention of radio. In the early 1860s the Scottish physicist James Clerk Maxwell derived four equations which together describe the behaviour of electricity and magnetism. They predicted the existence of a previously unknown phenomenon: electromagnetic waves. These waves were first observed in the early 1880s, and over the next two decades a succession of scientists and engineers built increasingly elaborate devices to produce and detect them. Eventually this gave birth to a new technology: radio. The Italian Guglielmo Marconi is commonly described as the father of radio - but many other figures were involved in its development, and it was not him but a Canadian, Reginald Fessenden, who first succeeded in transmitting speech over the airwaves. With: Simon Schaffer Professor of the History of Science at the University of Cambridge Elizabeth Bruton Postdoctoral Researcher at the University of Leeds John Liffen Curator of Communications at the Science Museum, London Producer: Thomas Morris.

Melvyn Bragg and his guests discuss Einstein's theories of relativity. Between 1905 and 1917 Albert Einstein formulated a theoretical framework which transformed our understanding of the Universe. The twin theories of Special and General Relativity offered insights into the nature of space, time and gravitation which changed the face of modern science. Relativity resolved apparent contradictions in physics and also predicted several new phenomena, including black holes. It's regarded today as one of the greatest intellectual achievements of the twentieth century, and had an impact far beyond the world of science. With: Ruth Gregory Professor of Mathematics and Physics at Durham University Martin Rees Astronomer Royal and Emeritus Professor of Cosmology and Astrophysics at the University of Cambridge Roger Penrose Emeritus Rouse Ball Professor of Mathematics at the University of Oxford. Producer: Thomas Morris.

Melvyn Bragg and his guests discuss cosmic rays. In 1912 the physicist Victor Hess discovered that the Earth is under constant bombardment from radiation coming from outside our atmosphere. These so-called cosmic rays have been known to cause damage to satellites and electronic devices on Earth, but most are absorbed by our atmosphere. The study of cosmic rays and their effects has led to major breakthroughs in particle physics. But today physicists are still trying to establish where these highly energetic subatomic particles come from. With: Carolin Crawford Gresham Professor of Astronomy and a member of the Institute of Astronomy at the University of Cambridge Alan Watson Emeritus Professor of Physics at the University of Leeds Tim Greenshaw Professor of Physics at the University of Liverpool. Producer: Thomas Morris.

Melvyn Bragg and his guests discuss one of the simplest and most remarkable of all molecules: water. Water is among the most abundant substances on Earth, covering more than two-thirds of the planet. Consisting of just three atoms, the water molecule is superficially simple in its structure but extraordinary in its properties. It is a rare example of a substance that can be found on Earth in gaseous, liquid and solid forms, and thanks to its unique chemical behaviour is the basis of all known life. Scientists are still discovering new things about it, such as the fact that there are at least fifteen different forms of ice. Hasok Chang Hans Rausing Professor of History and Philosophy of Science at the University of Cambridge Andrea Sella Professor of Chemistry at University College London Patricia Hunt Senior Lecturer in Chemistry at Imperial College London. Producer: Thomas Morris.

In a programme first broadcast in 2013, Melvyn Bragg and his guests discuss absolute zero, the lowest conceivable temperature.  In the early eighteenth century the French physicist Guillaume Amontons suggested that temperature had a lower limit.  The subject of low temperature became a fertile field of research in the nineteenth century, and today we know that this limit - known as absolute zero - is approximately minus 273 degrees Celsius.  It is impossible to produce a temperature exactly equal to absolute zero, but today scientists have come to within a billionth of a degree.  At such low temperatures physicists have discovered a number of strange new phenomena including superfluids, liquids capable of climbing a vertical surface. With: Simon Schaffer Professor of the History of Science at the University of Cambridge Stephen Blundell Professor of Physics at the University of Oxford Nicola Wilkin Lecturer in Theoretical Physics at the University of Birmingham Producer: Thomas Morris

Melvyn Bragg and his guests discuss the life and work of the Victorian anthropologist and archaeologist Augustus Pitt-Rivers. Over many years he amassed thousands of ethnographic and archaeological objects, some of which formed the founding collection of the Pitt Rivers Museum at Oxford University. Inspired by the work of Charles Darwin, Pitt-Rivers believed that human technology evolved in the same way as living organisms, and devoted much of his life to exploring this theory. He was also a pioneering archaeologist whose meticulous records of major excavations provided a model for later scholars. With: Adam Kuper Visiting Professor of Anthropology at Boston University Richard Bradley Professor in Archaeology at the University of Reading Dan Hicks University Lecturer & Curator of Archaeology at the Pitt Rivers Museum at the University of Oxford. Producer: Thomas Morris.

Melvyn Bragg and his guests discuss comets, the 'dirty snowballs' of the Solar System. In the early 18th century the Astronomer Royal Sir Edmond Halley compiled a list of appearances of comets, bright objects like stars with long tails which are occasionally visible in the night sky. He concluded that many of these apparitions were in fact the same comet, which returns to our skies around every 75 years, and whose reappearance he correctly predicted. Halley's Comet is today the best known example of a comet, a body of ice and dust which orbits the Sun. Since they contain materials from the time when the Solar System was formed, comets are regarded by scientists as frozen time capsules, with the potential to reveal important information about the early history of our planet and others. With: Monica Grady Professor of Planetary and Space Sciences at the Open University Paul Murdin Senior Fellow at the Institute of Astronomy at the University of Cambridge Don Pollacco Professor of Astronomy at the University of Warwick Producer: Thomas Morris.

Melvyn Bragg and his guests discuss the history of crystallography, the study of crystals and their structure. The discovery in the early 20th century that X-rays could be diffracted by a crystal revolutionised our knowledge of materials. This crystal technology has touched most people's lives, thanks to the vital role it plays in diverse scientific disciplines - from physics and chemistry, to molecular biology and mineralogy. To date, 28 Nobel Prizes have been awarded to scientists working with X-ray crystallography, an indication of its crucial importance. The history of crystallography began with the work of Johannes Kepler in the 17th century, but perhaps the most crucial leap in understanding came with the work of the father-and-son team the Braggs in 1912. They built on the work of the German physicist Max von Laue who had proved that X-rays are a form of light waves and that it was possible to scatter these rays using a crystal. The Braggs undertook seminal experiments which transformed our perception of crystals and their atomic arrangements, and led to some of the most significant scientific findings of the last century - such as revealing the structure of DNA. With: Judith Howard Director of the Biophysical Sciences Institute and Professor of Chemistry at the University of Durham Chris Hammond Life Fellow in Material Science at the University of Leeds Mike Glazer Emeritus Professor of Physics at the University of Oxford and Visiting Professor of Physics at the University of Warwick Producer: Natalia Fernandez.

Melvyn Bragg and his guests discuss Fermat's Last Theorem. In 1637 the French mathematician Pierre de Fermat scribbled a note in the margin of one of his books. He claimed to have proved a remarkable property of numbers, but gave no clue as to how he'd gone about it. "I have found a wonderful demonstration of this proposition," he wrote, "which this margin is too narrow to contain". Fermat's theorem became one of the most iconic problems in mathematics and for centuries mathematicians struggled in vain to work out what his proof had been. In the 19th century the French Academy of Sciences twice offered prize money and a gold medal to the person who could discover Fermat's proof; but it was not until 1995 that the puzzle was finally solved by the British mathematician Andrew Wiles. With: Marcus du Sautoy Professor of Mathematics & Simonyi Professor for the Public Understanding of Science at the University of Oxford Vicky Neale Fellow and Director of Studies in Mathematics at Murray Edwards College at the University of Cambridge Samir Siksek Professor at the Mathematics Institute at the University of Warwick. Producer: Natalia Fernandez.

Melvyn Bragg and his guests discuss the cell, the fundamental building block of life. First observed by Robert Hooke in 1665, cells occur in nature in a bewildering variety of forms. Every organism alive today consists of one or more cells: a single human body contains up to a hundred trillion of them. The first life on Earth was a single-celled organism which is thought to have appeared around three and a half billion years ago. That simple cell resembled today's bacteria. But eventually these microscopic entities evolved into something far more complex, and single-celled life gave rise to much larger, complex multicellular organisms. But how did the first cell appear, and how did that prototype evolve into the sophisticated, highly specialised cells of the human body? With: Steve Jones Professor of Genetics at University College London Nick Lane Senior Lecturer in the Department of Genetics, Evolution and Environment, University College London Cathie Martin Group Leader at the John Innes Centre and Professor in the School of Biological Sciences at the University of East Anglia Producer: Thomas Morris.

Melvyn Bragg and his guests discuss game theory, the mathematical study of decision-making. First formulated in the 1940s, the discipline entails devising 'games' to simulate situations of conflict or cooperation. It allows researchers to unravel decision-making strategies, and even to establish why certain types of behaviour emerge. Some of the games studied in game theory have become well known outside academia - they include the Prisoner's Dilemma, an intriguing scenario popularised in novels and films, and which has inspired television game shows. Today game theory is seen as a vital tool in such diverse fields as evolutionary biology, economics, computing and philosophy. With:Ian StewartEmeritus Professor of Mathematics at the University of WarwickAndrew ColmanProfessor of Psychology at the University of LeicesterRichard BradleyProfessor of Philosophy at the London School of Economics and Political Science.Producer: Thomas Morris.

Melvyn Bragg and his guests discuss the emergence of geology as a scientific discipline. A little over two hundred years ago a small group of friends founded the Geological Society of London. This organisation was the first devoted to furthering the discipline of geology - the study of the Earth, its history and composition. Although geology only emerged as a separate area of study in the late eighteenth century, many earlier thinkers had studied rocks, fossils and the materials from which the Earth is made. Ancient scholars in Egypt and Greece speculated about the Earth and its composition. And in the Renaissance the advent of mining brought further insight into the nature of objects found underground and how they got there. But how did such haphazard study of rocks and fossils develop into a rigorous scientific discipline?With:Stephen PumfreySenior Lecturer in the History of Science at Lancaster UniversityAndrew ScottProfessor of Applied Palaeobotany at Royal Holloway, University of LondonLeucha VeneerResearch Associate at the Centre for the History of Science, Technology and Medicine at the University of Manchester.Producer: Thomas Morris.

Melvyn Bragg and his guests discuss the measurement of time. Early civilisations used the movements of heavenly bodies to tell the time, but even in the ancient world more sophisticated timekeeping devices such as waterclocks were known. The development of mechanical clocks in Europe emerged in the medieval period when monks used such devices to sound an alarm to signal it was the hour to pray, although these clocks did not tell them the time. For hundreds of years clocks were inaccurate and it proved hard to remedy the problems, let alone settle on a standard time that the country should follow. It was with the advent of the railways that time finally became standardised in Britain in the mid-19th century and only in 1884 that Greenwich became the prime meridian of the world. Atomic clocks now mark the passing of the days, hours, and minutes and they are capable of keeping time to a second in 15 million years. With:Kristen LippincottFormer Director of the Royal Observatory, GreenwichJim BennettDirector of the Museum of the History of Science at the University of OxfordJonathan BettsSenior Curator of Horology at the Royal Observatory, GreenwichProducer: Natalia Fernandez.

Melvyn Bragg and his guests discuss the physics of electrical conduction. Although electricity has been known for several hundred years, it was only in the early twentieth century that physicists first satisfactorily explained the phenomenon. Electric current is the passage of charged particles through a medium - but a material will only conduct electricity if its atomic structure enables it to do so. In investigating electrical conduction scientists discovered two new classes of material. Semiconductors, first exploited commercially in the 1950s, have given us the transistor, the solar cell and the silicon chip, and have revolutionised telecommunications. And superconductors, remarkable materials first observed in 1911, are used in medical imaging and at the Large Hadron Collider in Geneva. With:Frank CloseProfessor of Physics at the University of OxfordJenny NelsonProfessor of Physics at Imperial College LondonLesley CohenProfessor of Solid State Physics at Imperial College LondonProducer: Thomas Morris.

Melvyn Bragg and his guests discuss the evolution of the Scientific Method, the systematic and analytical approach to scientific thought. In 1620 the great philosopher and scientist Francis Bacon published the Novum Organum, a work outlining a new system of thought which he believed should inform all enquiry into the laws of nature. Philosophers before him had given their attention to the reasoning that underlies scientific enquiry; but Bacon's emphasis on observation and experience is often seen today as giving rise to a new phenomenon: the scientific method.The scientific method, and the logical processes on which it is based, became a topic of intense debate in the seventeenth century, and thinkers including Isaac Newton, Thomas Huxley and Karl Popper all made important contributions. Some of the greatest discoveries of the modern age were informed by their work, although even today the term 'scientific method' remains difficult to define.With: Simon SchafferProfessor of the History of Science at the University of CambridgeJohn WorrallProfessor of the Philosophy of Science at the London School of Economics and Political ScienceMichela MassimiSenior Lecturer in the Philosophy of Science at University College London.Producer: Thomas Morris.

Melvyn Bragg and guests discuss the giant molecules that form the basis of all life. Macromolecules, also known as polymers, are long chains of atoms. They form the proteins that make up our bodies, as well as many of the materials of modern life. Man's ability to mimic the structure of macromolecules has led to the invention of plastics such as nylon, paints and adhesives. Most of our clothes are made of macromolecules, and our food is macromolecular. The medical sciences are making increasingly sophisticated use of macromolecules, from growing replacement skin and bone to their increasing use in drug delivery. One of the most famous macromolecules is DNA, an infinitely more complex polymer than man has ever managed to produce. We've only known about macromolecules for just over a century, so what is the story behind them and how might they change our lives in the future?With:Tony RyanPro-Vice Chancellor for the Faculty of Science at the University of SheffieldAthene DonaldProfessor of Experimental Physics at the University of Cambridge and a Fellow of Robinson CollegeCharlotte WilliamsReader in Polymer Chemistry and Catalysis at Imperial College, London Producer: Natalia Fernandez.

Melvyn Bragg and his guests discuss the Hippocratic Oath. The Greek physician Hippocrates, active in the fifth century BC, has been described as the father of medicine, although little is known about his life and some scholars even argue that he was not one person but several. A large body of work originally attributed to him, the Hippocratic Corpus, was disseminated widely in the ancient world, and contains treatises on a wide variety of subjects, from fractures to medical ethics.Today we know that the Hippocratic Corpus cannot have been written by a single author. But many of its texts shaped Western medicine for centuries. The best known is the Hippocratic Oath, an ethical code for doctors. Celebrated in the ancient world, and later referred to by Arabic scholars, it offers medics guidance on how they should behave. Although it has often been revised and adapted, the Hippocratic Oath remains one of the most significant and best known documents of medical science - but there is little evidence that it was routinely sworn by doctors until modern times. With:Vivian NuttonEmeritus Professor of the History of Medicine at University College LondonHelen KingProfessor of Classical Studies at the Open UniversityPeter PormannWellcome Trust Associate Professor in Classics and Ancient History at the University of WarwickProducer: Thomas Morris.

Melvyn Bragg and his guests discuss the origins of infectious disease. Infectious disease has been with us for millennia. There are reports of ancient outbreaks of plague in the Bible, and in numerous historical sources from China, the Middle East and Europe. Other infections, including smallpox, tuberculosis and measles, have also been known for centuries. But some diseases made their first appearances only recently: HIV emerged around a century ago, while the Ebola virus was first recorded in the 1970s.But where do the agents of disease come from, and what determines where and when new viruses and bacteria appear? Modern techniques allow scientists to trace the histories of infective agents through their genomes; the story of disease provides a fascinating microcosm of the machinery of evolution.With:Steve JonesProfessor of Genetics at University College LondonSir Roy AndersonProfessor of Infectious Disease Epidemiology at Imperial College LondonMark PallenProfessor of Microbial Genomics at the University of Birmingham.Producer: Thomas Morris.

Melvyn Bragg and his guests discuss the neutrino.In 1930 the physicist Wolfgang Pauli proposed the existence of an as-yet undiscovered subatomic particle. He also bet his colleagues a case of champagne that it would never be detected. He lost his bet when in 1956 the particle, now known as the neutrino, was first observed in an American nuclear reactor. Neutrinos are some of the most mysterious particles in the Universe. The Sun produces trillions of them every second, and they constantly bombard the Earth and everything on it. Neutrinos can pass through solid rock, and even stars, at almost the speed of light without being impeded, and are almost impossible to detect. Today, experiments involving neutrinos are providing insights into the nature of matter, the contents of the Universe and the processes deep inside stars.With:Frank CloseProfessor of Physics at Exeter College at the University of OxfordSusan CartwrightSenior Lecturer in Particle Physics and Astrophysics at the University of SheffieldDavid WarkProfessor of Particle Physics at Imperial College, London, and the Rutherford Appleton Laboratory. Producer: Thomas Morris.

Melvyn Bragg and his guests discuss the age of the Universe.Since the 18th century, when scientists first realised that the Universe had existed for more than a few thousand years, cosmologists have debated its likely age. The discovery that the Universe was expanding allowed the first informed estimates of its age to be made by the great astronomer Edwin Hubble in the early decades of the twentieth century. Hubble's estimate of the rate at which the Universe is expanding, the so-called Hubble Constant, has been progressively improved. Today cosmologists have a variety of other methods for ageing the Universe, most recently the detailed measurements of cosmic microwave background radiation - the afterglow of the Big Bang - made in the last decade. And all these methods seem to agree on one thing: the Universe has existed for around 13.75 billion years.With:Martin ReesAstronomer Royal and Emeritus Professor of Cosmology and Astrophysics at the University of CambridgeCarolin CrawfordMember of the Institute of Astronomy and Fellow of Emmanuel College at the University of CambridgeCarlos FrenkDirector of the Institute for Computational Cosmology at the University of Durham.Producer: Thomas Morris.

Melvyn Bragg and his guests discuss the nervous system. Most animals have a nervous system, a network of nerve tissues which allows parts of the body to communicate with each other. In humans the most significant parts of this network are the brain, spinal column and retinas, which together make up the central nervous system. But there is also a peripheral nervous system, which enables sensation, movement and the regulation of the major organs. Scholars first described the nerves of the human body over two thousand years ago. For 1400 years it was believed that they were animated by 'animal spirits', mysterious powers which caused sensation and movement. In the eighteenth century scientists discovered that nerve fibres transmitted electrical impulses; it was not until the twentieth century that chemical agents - neurotransmitters - were first identified. With: Colin Blakemore Professor of Neuroscience at the University of Oxford Vivian Nutton Emeritus Professor of the History of Medicine at University College, London Tilli Tansey Professor of the History of Modern Medical Sciences at Queen Mary, University of London. Producer: Thomas Morris.

Melvyn Bragg and his guests discuss randomness and pseudorandomness.Randomness is the mathematics of the unpredictable. Dice and roulette wheels produce random numbers: those which are unpredictable and display no pattern. But mathematicians also talk of 'pseudorandom' numbers - those which appear to be random but are not. In the last century random numbers have become enormously useful to statisticians, computer scientists and cryptographers. But true randomness is difficult to find, and mathematicians have devised many ingenious solutions to harness or simulate it. These range from the Premium Bonds computer ERNIE (whose name stands for Electronic Random Number Indicator Equipment) to new methods involving quantum physics.Digital computers are incapable of behaving in a truly random fashion - so instead mathematicians have taught them how to harness pseudorandomness. This technique is used daily by weather forecasters, statisticians, and computer chip designers - and it's thanks to pseudorandomness that secure credit card transactions are possible.With:Marcus du SautoyProfessor of Mathematics at the University of OxfordColva Roney-DougalSenior Lecturer in Pure Mathematics at the University of St AndrewsTimothy GowersRoyal Society Research Professor in Mathematics at the University of CambridgeProducer: Thomas Morris.

Melvyn Bragg and his guests discuss the innovations and influence of Thomas Edison, one of the architects of the modern age.Edison is popularly remembered as the man who made cheap electric light possible. Born in 1847, he began his career working in the new industry of telegraphy, and while still in his early twenties made major improvements to the technology of the telegraph. Not long afterwards he invented a new type of microphone which was used in telephones for almost a century. In the space of three productive years, Edison developed the phonograph and the first commercially viable light bulb and power distribution system. Many more inventions were to follow: he also played a part in the birth of cinema in the 1890s. When he died in 1931 he had patented no fewer than 1093 devices - the most prolific inventor in history. As the creator of the world's first industrial research laboratory he forever changed the way in which innovation took place.With:Simon SchafferProfessor of the History of Science, University of CambridgeKathleen BurkProfessor of History, University College LondonIwan MorusReader in History, University of AberystwythProducer: Thomas Morris.

Melvyn Bragg and his guests discuss the role played by women in Enlightenment science. During the eighteenth century the opportunities for women to gain a knowledge of science were minimal. Universities and other institutions devoted to research were the preserve of men. Yet many important contributions to the science of the Enlightenment were made by women. These ranged from major breakthroughs like those of the British astronomer Caroline Herschel, the first woman to discover a comet, to important translations of scientific literature such as Emilie du Chatelet's French version of Newton's Principia - and all social classes were involved, from the aristocratic amateur botanists to the women artisans who worked in London's workshops manufacturing scientific instruments. The image above, of Emilie du Chatelet, is attributed to Maurice Quentin de La Tour. With Patricia Fara Senior Tutor at Clare College, University of Cambridge Karen O'Brien Professor of English at the University of Warwick Judith Hawley Professor of 18th Century Literature at Royal Holloway, University of London Producer: Thomas Morris.

Melvyn Bragg and his guests discuss the history of logic. Logic, the study of reasoning and argument, first became a serious area of study in the 4th century BC through the work of Aristotle. He created a formal logical system, based on a type of argument called a syllogism, which remained in use for over two thousand years. In the nineteenth century the German philosopher and mathematician Gottlob Frege revolutionised logic, turning it into a discipline much like mathematics and capable of dealing with expressing and analysing nuanced arguments. His discoveries influenced the greatest mathematicians and philosophers of the twentieth century and considerably aided the development of the electronic computer. Today logic is a subtle system with applications in fields as diverse as mathematics, philosophy, linguistics and artificial intelligence.With:A.C. GraylingProfessor of Philosophy at Birkbeck, University of LondonPeter MillicanGilbert Ryle Fellow in Philosophy at Hertford College at the University of OxfordRosanna KeefeSenior Lecturer in Philosophy at the University of Sheffield.Producer: Thomas Morris.

Melvyn Bragg and his guests discuss imaginary numbers. In the sixteenth century, a group of mathematicians in Bologna found a solution to a problem that had puzzled generations before them: a completely new kind of number. For more than a century this discovery was greeted with such scepticism that the great French thinker Rene Descartes dismissed it as an "imaginary" number.The name stuck - but so did the numbers. Long dismissed as useless or even fictitious, the imaginary number i and its properties were first explored seriously in the eighteenth century. Today the imaginary numbers are in daily use by engineers, and are vital to our understanding of phenomena including electricity and radio waves. With Marcus du SautoyProfessor of Mathematics at Oxford University Ian StewartEmeritus Professor of Mathematics at the University of WarwickCaroline SeriesProfessor of Mathematics at the University of WarwickProducer: Thomas Morris.

Melvyn Bragg and his guests discuss Pliny's Natural History.Some time in the first century AD, the Roman scholar Pliny the Elder published his Naturalis Historia, or Natural History, an enormous reference work which attempted to bring together knowledge on every subject under the sun. The Natural History contains information on zoology, astronomy, geography, minerals and mining and - unusually for a work of this period - a detailed treatise on the history of classical art. It's a fascinating snapshot of the state of human knowledge almost two millennia ago.Pliny's 37-volume magnum opus is one of the most extensive works of classical scholarship to survive in its entirety, and was being consulted by scholars as late as the Renaissance. It had a significant influence on intellectual history, and has provided the template for every subsequent encyclopaedia.With:Serafina CuomoReader in Roman History at Birkbeck, University of LondonAude DoodyLecturer in Classics at University College, DublinLiba TaubReader in the History and Philosophy of Science, Cambridge UniversityProducer: Thomas Morris.

Melvyn Bragg and his guests discuss the history of Antarctica.The most southerly of the continents is the bleakest and coldest place on Earth. Almost entirely covered in ice, Antarctica spends much of the winter in total darkness.Antarctica was first named in the second century AD by the geographer Marinus of Tyre, who was one of many early geographers to speculate about the existence of a huge southern landmass to balance the known lands of northern Europe. But it wasn't until the nineteenth century that modern man laid eyes on the continent.In the intervening two hundred years the continent has been the scene for some of the most famous - and tragic - events of human exploration. In 1959 an international treaty declared Antarctica a scientific reserve, set aside for peaceful use by any nation willing to subscribe to the terms of the agreement.With: Jane FrancisProfessor of Paleoclimatology at the University of LeedsJulian DowdeswellDirector of the Scott Polar Research Institute and Professor of Physical Geography at the University of CambridgeDavid WaltonEmeritus Professor at the British Antarctic Survey and Visiting Professor at the University of Liverpool.Producer: Thomas Morris.

Melvyn Bragg and his guests discuss the Neanderthals.In 1856, quarry workers in Germany found bones in a cave which seemed to belong to a bear or other large mammal. They were later identified as being from a previously unknown species of hominid similar to a human. The specimen was named Homo neanderthalis after the valley in which the bones were found.This was the first identified remains of a Neanderthal, a species which inhabited parts of Europe and Central Asia from around 400,000 years ago. Often depicted as little more advanced than apes, Neanderthals were in fact sophisticated, highly-evolved hunters capable of making tools and even jewellery.Scholarship has established much about how and where the Neanderthals lived - but the reasons for their disappearance from the planet around 28,000 years ago remain unclear.With: Simon Conway MorrisProfessor of Evolutionary Palaeobiology at the University of CambridgeChris Stringer Research Leader in Human Origins at the Natural History Museum and Visiting Professor at Royal Holloway, University of LondonDanielle SchreveReader in Physical Geography at Royal Holloway, University of LondonProducer: Thomas Morris.

From the 1600s to the 1800s, scientific research in Britain was not yet a professional, publicly-funded career.So the wealth, status and freedom enjoyed by British aristocrats gave them the opportunity to play an important role in pushing science forwards - whether as patrons or practitioners.The Cavendish family produced a whole succession of such figures.In the 1600s, the mathematician Sir Charles Cavendish and his brother William collected telescopes and mathematical treatises, and promoted dialogue between British and Continental thinkers. They brought Margaret Cavendish, William's second wife, into their discussions and researches, and she went on to become a visionary, if eccentric, science writer, unafraid to take on towering figures of the day like Robert Hooke.In the 1700s, the brothers' cousin's great-grandson, Lord Charles Cavendish, emerged as a leading light of the Royal Society.Underpinned by his rich inheritance, Charles' son Henry became one of the great experimental scientists of the English Enlightenment.And in the 1800s, William Cavendish, Henry's cousin's grandson, personally funded the establishment of Cambridge University's Cavendish Laboratory. In subsequent decades, the Lab become the site of more great breakthroughs.With:Jim BennettDirector of the Museum of the History of Science at the University of OxfordPatricia FaraSenior Tutor of Clare College, University of CambridgeSimon SchafferProfessor of History of Science at the University of Cambridge and Fellow of Darwin College, CambridgeProducer - Phil Tinline.

The Cool Universe is the name astronomers give to the matter between the stars.These great clouds of dust and gas are not hot enough to be detected by optical telescopes.But over the last few decades, they have increasingly become the focus of infrared telescopy.Astronomers had long encountered dark, apparently starless patches in the night sky. When they discovered that these were actually areas obscured by dust, they found a way to see through these vexing barriers, using infrared telescopes, to the light beyond.However, more recently, the dust itself has become a source of fascination.The picture now being revealed by infrared astronomy is of a universe that is dynamic.In this dynamic universe, matter is recycled - and so the dust and gas of the Cool Universe play a vital role. They are the material from which the stars are created, and into which they finally disintegrate, enriching the reservoir of cool matter from which new stars will eventually be formed. As a result of the new research, we are now beginning to see first-hand the way our planet was formed when the solar system was born.With:Carolin CrawfordMember of the Institute of Astronomy, and Fellow of Emmanuel College, at the University of CambridgePaul MurdinVisiting Professor of Astronomy at Liverpool John Moores University's Astronomy Research InstituteMichael Rowan-RobinsonProfessor of Astrophysics at Imperial College, LondonProducer: Phil Tinline.

Melvyn Bragg and guests Usha Goswami, Annette Karmiloff-Smith and Denis Mareschal discuss what new research reveals about the infant brain.For obvious reasons, what happens in the minds of very young, pre-verbal children is elusive. But over the last century, the psychology of early childhood has become a major subject of study. Some scientists and researchers have argued that children develop skills only gradually, others that many of our mental attributes are innate. Sigmund Freud concluded that infants didn't differentiate themselves from their environment. The pioneering Swiss child psychologist Jean Piaget thought babies' perception of the world began as a 'blooming, buzzing confusion' of colour, light and sound, before they developed a more sophisticated worldview, first through the senses and later through symbol. More recent scholars such as the leading American theoretical linguist Noam Chomsky have argued that the fundamentals of language are there from birth. Chomsky has famously argued that all humans have an innate, universally applicable grammar.Over the last ten to twenty years, new research has shed fresh light on important aspects of the infant brain which have long been shrouded in mystery or mired in dispute, from the way we start to learn to speak to the earliest understanding that other people have their own minds. With:Usha Goswami, Professor of Education at the University of Cambridge and Director of its Centre for Neuroscience in Education Annette Karmiloff-Smith, Professorial Research Fellow at the Centre for Brain and Cognitive Development at the Department of Psychological Sciences, Birkbeck College, University of LondonDenis Mareschal, Professor of Psychology at the Centre for Brain and Cognitive Development at Birkbeck College, University of London.

Melvyn Bragg and guests John Barrow, Colva Roney-Dougal and Marcus du Sautoy explore the unintended consequences of mathematical discoveries, from the computer to online encryption, to alternating current and predicting the path of asteroids.In his book The Mathematician's Apology (1941), the Cambridge mathematician GH Hardy expressed his reverence for pure maths, and celebrated its uselessness in the real world. Yet one of the branches of pure mathematics in which Hardy excelled was number theory, and it was this field which played a major role in the work of his younger colleague, Alan Turing, as he worked first to crack Nazi codes at Bletchley Park and then on one of the first computers.Melvyn Bragg and guests explore the many surprising and completely unintended uses to which mathematical discoveries have been put. These include:The cubic equations which led, after 400 years, to the development of alternating current - and the electric chair.The centuries-old work on games of chance which eventually contributed to the birth of population statistics.The discovery of non-Euclidean geometry, which crucially provided an 'off-the-shelf' solution which helped Albert Einstein forge his theory of relativity.The 17th-century theorem which became the basis for credit card encryption.In the light of these stories, Melvyn and his guests discuss how and why pure mathematics has had such a range of unintended consequences.John Barrow is Professor of Mathematical Sciences at the University of Cambridge and Professor of Geometry at Gresham College, London; Colva Roney-Dougal is Lecturer in Pure Mathematics at the University of St Andrews; Marcus du Sautoy is Charles Simonyi Professor for the Public Understanding of Science and Professor of Mathematics at the University of Oxford.

As part of the BBC's year of science programming, Melvyn Bragg looks at the history of the oldest scientific learned society of them all: the Royal Society. The horrors of the First World War were a shocking indictment of the power of science. Picking up the thread at this hiatus in scientific optimism, this programme, recorded in the current home of the Royal Society in Carlton House Terrace in London, looks at the more subtle, discreet role the Society played in the 20th century, such as secretly arranging for refugee scientists to flee Germany, co-ordinating international scientific missions during the Cold War and quietly distributing government grant money to fund the brightest young researchers in the land. As ever more important scientific issues face the world and Britain today, the programme asks how well placed the Royal Society is to take an important lead in the future.

As part of the BBC's year of science programming, Melvyn Bragg looks at the history of the oldest scientific learned society of them all: the Royal Society. The 19th century blooms scientifically with numerous alternative, specialist learned societies and associations, all threatening the Royal Society's pre-eminence. Attempts to reform the membership criteria - marking scientific leadership's painful transition from patronage to expertise - are troubled, and organisations such as the British Association for the Advancement of Science (now the BSA) excite and enliven scientific discourse outside of London. Science becomes a realistic career and a path of improvement, and by the time HG Wells writes science fiction at the end of the 19th century, there are sufficient numbers of interested, informed readers to suggest that Edwardian society contained the beginnings of a scientific society.

As part of the BBC's year of science programming, Melvyn Bragg looks at the history of the oldest scientific learned society of them all: the Royal Society. Programme two begins in the coffee house Isaac Newton and the fellows of the early 18th century frequented. At the Royal Observatory, Greenwich, we learn how Newton's feud with the Astronomer Royal John Flamsteed tested the lines between government-funded research and public access. In the age of exploration, senior fellows accompany naval expeditions, such as Cook's expedition to Tahiti and subsequent discovery of Australia. International relations are fostered between scientists such as Benjamin Franklin, whose house in London serves as live-in lab and de facto American embassy. By the end of the century the President, Sir Joseph Banks, successfully embeds the Royal Society in the imperial bureaucratic hub of the new Somerset House. But while senior fellows concentrated on foreign fields, a more radical, dissident science and manufacturing base wrought the Industrial Revolution right under their noses.

As part of the BBC's year of science programming, Melvyn Bragg looks at the history of the oldest scientific learned society of them all: the Royal Society. Melvyn travels to Wadham College, Oxford, where under the shadow of the English Civil War, the young Christopher Wren and friends experimented in the garden of their inspirational college warden, John Wilkins. Back in London, as Charles II is brought to the throne from exile, the new Society is formally founded one night in Gresham College. When London burns six years later, it is two of the key early Fellows of the Society who are charged with its rebuilding. And, as Melvyn finds out, in the secret observatory in The Monument to the fire, it is science which flavours their plans.

Melvyn Bragg and guests Serafina Cuomo, John O'Connor and Ian Stewart discuss the ideas and influence of the Greek mathematician Pythagoras and his followers, the Pythagoreans.The Ancient Greek mathematician Pythagoras is probably best known for the theorem concerning right-angled triangles that bears his name. However, it is not certain that he actually developed this idea; indeed, some scholars have questioned not only his true intellectual achievements, but whether he ever existed. We do know that a group of people who said they were followers of his - the Pythagoreans - emerged around the fifth century BC. Melvyn Bragg and his guests discuss what we do and don't know about this legendary figure and his followers, and explore the ideas associated with them. Some Pythagoreans, such as Philolaus and Archytas, were major mathematical figures in their own right. The central Pythagorean idea was that number had the capacity to explain the truths of the world. This was as much a mystical belief as a mathematical one, encompassing numerological notions about the 'character' of specific numbers. Moreover, the Pythagoreans lived in accordance with a bizarre code which dictated everything from what they could eat to how they should wash. Nonetheless, Pythagorean ideas, centred on their theory of number, have had a profound impact on Western science and philosophy, from Plato through astronomers like Copernicus to the present day.Serafina Cuomo is Reader in Roman History at Birkbeck College, University of London; John O'Connor is Senior Lecturer in Mathematics at the University of Saint Andrews; Ian Stewart is Emeritus Professor of Mathematics at the University of Warwick.

Melvyn Bragg and guests Jim Al-Khalili, Frank Close and Frank James discuss the history of the discovery of radiation.Today the word 'radiation' conjures up images of destruction. But in physics, it simply describes the emission, transmission and absorption of energy, and the discovery of how radiation works has allowed us to identify new chemical elements, treat cancer and work out what the stars are made of.Over the course of the 19th century, physicists from Thomas Young, through Michael Faraday to Henri Becquerel made discovery after discovery, gradually piecing together a radically new picture of reality. They explored the light beyond the visible spectrum, connected electricity and magnetism, and eventually showed that heat, light, radio and mysterious new phenomena like 'X-rays' were all forms of 'electromagnetic wave'. In the early 20th century, with the discovery of radioactivity, scientists like Max Planck and Ernest Rutherford completed the picture of the 'electromagnetic spectrum'. This was a cumulative achievement that transformed our vision of the physical world, and what we could do in it.Jim Al-Khalili is Professor of Theoretical Physics and Chair in the Public Engagement in Science at the University of Surrey; Frank Close is Professor of Physics at Exeter College, University of Oxford; Frank James is Professor of the History of Science at the Royal Institution.

Melvyn Bragg and guests Richard Corfield, Jane Francis and Sanjeev Gupta discuss the geological formation of Britain.Around 600 million years ago the island that we now call Britain was in two parts, far to the south of the Equator. Scotland and north-western Ireland were part of a continent (Laurentia) that also included what is now North America. To the south-east, near the Antarctic Circle, meanwhile, you would have found southern Ireland, England and Wales. They formed a mini-continent (Avalonia) with what is now Newfoundland.Over the course of hundreds of millions of years, as they inched their way north, the two parts came together - first as part of a vast unitary continent (Pangaea), later as a promontory on the edge of Europe, and eventually, as sea levels rose, as an island. The story of how Britain came to be where it is now, in its current shape - from the separation of North America and Europe to the carving out of the English Channel - is still being uncovered today.Richard Corfield is Visiting Senior Resarch Fellow at Oxford University; Jane Francis is Professor of Palaeoclimatology at the University of Leeds; Sanjeev Gupta is a Royal Society-Leverhulme Trust Research Fellow at Imperial College London.

Melvyn Bragg discusses the epic feud between Sir Isaac Newton and Gottfried Leibniz over who invented an astonishingly powerful new mathematical tool - calculus. Both claimed to have conceived it independently, but the argument soon descended into a bitter battle over priority, plagiarism and philosophy. Set against the backdrop of the Hanoverian succession to the English throne and the formation of the Royal Society, the fight pitted England against Europe, geometric notation against algebra. It was fundamental to the grounding of a mathematical system which is one of the keys to the modern world, allowing us to do everything from predicting the pressure building behind a dam to tracking the position of a space shuttle.Melvyn is joined by Simon Schaffer, Professor of History of Science at the University of Cambridge and Fellow of Darwin College; Patricia Fara, Senior Tutor at Clare College, University of Cambridge; and Jackie Stedall, Departmental Lecturer in History of Mathematics at the University of Oxford.

Melvyn Bragg and guests Martin Brasier, Richard Corfield and Rachel Wood discuss the Ediacara Biota, the Precambrian life forms which vanished 542 million years ago, and whose discovery proved Darwin right in a way he never imagined. Darwin was convinced that there must have been life before the Cambrian era, but he didn't think it was possible for fossils like the Ediacara to have been preserved. These sea-bed organisms were first unearthed in the 19th century, but were only recognised as Precambrian in the mid-20th century. This was an astonishing discovery. Ever since, scientists have been working to determine its significance. Were the Ediacara the earliest forms of animal life? Or were they a Darwinian dead end? Either way, it is argued, they reveal some of the secrets of the workings of evolution. Richard Corfield is Senior Lecturer in Earth Sciences at the Open University; Martin Brasier is Professor of Palaeobiology at the University of Oxford; Rachel Wood is Lecturer in Carbonate Geoscience at the University of Edinburgh.

Melvyn Bragg discusses Logical Positivism, the eye-wateringly radical early 20th century philosophical movement. The Logical Positivists argued that much previous philosophy was built on very shaky foundations, and they wanted to go right back to the drawing board. They insisted that philosophy - and science - had to be much more rigorous before it started making grand claims about the world. The movement began with the Vienna Circle, a group of philosophically-trained scientists and scientifically-trained philosophers, who met on Thursdays, in 'Red Vienna', in the years after the First World War. They were trying to remould philosophy in a world turned upside down not just by war, but by major advances in science. Their hero was not Descartes or Hegel but Albert Einstein. The group's new doctrine rejected great swathes of earlier philosophy, from meditations on the existence of God to declarations on the nature of History, as utterly meaningless. When the Nazis took power, they fled to England and America, where their ideas put down new roots, and went on to have a profound impact.Melvyn is joined by Barry Smith, Professor of Philosophy at the University of London; Nancy Cartwright, Professor of Philosophy at the London School of Economics; and Thomas Uebel, Professor of Philosophy at Manchester University.

Melvyn Bragg and guests Steve Jones, Bill Amos and Eleanor Weston discuss the evolutionary history of the whale. The ancestor of all whales alive today was a small, land-based mammal with cloven hoofs, perhaps like a pig or a big mole. How this creature developed into the celebrated leviathan of the deep is one of the more extraordinary stories in the canon of evolution. The whale has undergone vast changes in size, has moved from land to water, lost its legs and developed specialised features such as filter feeding and echo location. How it achieved this is an exemplar of how evolution works and how natural selection can impose extreme changes on the body shape and abilities of living things. How the story of the whales was pieced together also reveals the various forms of evidence - from fossils to molecules - that we now use to understand the ancestry of life on Earth.Steve Jones is Professor of Genetics at University College London; Eleanor Weston is a mammalian palaeontologist at the Natural History Museum, London; Bill Amos is Professor of Evolutionary Genetics at Cambridge University.

Melvyn Bragg and guests Frank Close, Jocelyn Bell Burnell and Ruth Gregory discuss the Vacuum of Space. The idea that there is a nothingness at the heart of nature has exercised philosophers and scientists for millennia, from Thales's belief that all matter was water to Newton's concept of the Ether and Einstein's idea of Space-Time. Recently, physicists have realised that the vacuum is not as empty as we thought and that the various vacuums of nature vibrate with forces and energies, waves and particles and the mysterious phenomena of the Higgs field and dark energy.

Patricia Fara, Stephen Pumfrey and Rhodri Lewis join Melvyn Bragg to discuss the Jacobean lawyer, political fixer and alleged founder of modern science Francis Bacon.In the introduction to Thomas Spratt's History of the Royal Society, there is a poem about man called Francis Bacon which declares 'Bacon, like Moses, led us forth at last, The barren wilderness he past, Did on the very border stand Of the blest promis'd land, And from the mountain's top of his exalted wit, Saw it himself, and shew'd us it'.Francis Bacon was a lawyer and political schemer who climbed the greasy pole of Jacobean politics and then fell down it again. But he is most famous for developing an idea of how science should be done - a method that he hoped would slough off the husk of ancient thinking and usher in a new age. It is called Baconian Method and it has influenced and inspired scientists from Bacon's own time to the present day.

Melvyn Bragg and guests discuss the Library at Alexandria. Founded by King Ptolemy in the 3rd century BC the library was the first attempt to collect all the knowledge of the ancient world in one place. Scholars including Archimedes and Euclid came to study its grand array of papyri. the legacy of the library is with us today, not just in the ideas it stored and the ideas it seeded but also in the way it organised knowledge and the tools developed for dealing with it. It still influences the things we know and the way we know them to this day.With Simon Goldhill, Professor of Greek at the University of Cambridge; Matthew Nicholls, Lecturer in Classics at the University of Reading; Serafina Cuomo, Reader in Roman History at Birkbeck College, University of London.

Melvyn Bragg and guests discuss one of the deepest problems in contemporary physics. It’s called the measurement problem and it emerged from the flurry of activity in the early 20th century that gave rise to Quantum Mechanics. If the most famous fruit in physics is an apple, the most famous animal in physics is a cat. Schrödinger’s cat is named after Edwin Schrödinger, a theoretical physicist who in the early 20th century helped to develop the radical theories of Quantum Mechanics. The cat does not actually exist – it is the subject of a thought experiment – in which the rules of quantum mechanics make it appear both dead and alive at the same time.The problem of a cat that is both dead and alive illustrates the challenges of quantum physics and at the heart of this apparent absurdity is a thing called the measurement problem.The measurement problem arises because we don’t really understand how the atoms that constitute our world behave. They are fundamentally mysterious to us, even shocking, and they defy our attempts to measure and make sense of them. Possible solutions range from the existence of multiple realities to the rather more mundane possibility of an error in our mathematics - but a solution, if found, could transform our understanding of reality. With Basil Hiley, Emeritus Professor of Physics at Birkbeck, University of London, Simon Saunders, Reader in Philosophy of Physics and University Lecturer in Philosophy of Science at the University of Oxford; Roger Penrose, Emeritus Rouse Ball Professor of Mathematics at the University of Oxford

Melvyn Bragg and guests discuss the Observatory in Jaipur with its vast and beautiful instruments built to make astronomical measurements of the stars. Commissioned in the early 18th century by the Rajput prince and child prodigy, Jai Singh, it was at the centre of attempts to marry hundreds of years of Indian and Persian astronomical tradition. The Observatory was also at the very centre of the city which was laid out according to astrological principles. Jai Singh’s observatory was the cutting edge of Indian astronomy but also a repository for aeons of Hindu and Islamic intellectual life. The instruments were extraordinarily accurate for the time but used no lenses and were built of masonry, not metal. They helped to develop astrological tables, immensely important in Hindu Society, and come down to us as a record of Indian astronomy on the cusp of colonialism. With Chandrika Kaul, Lecturer in Modern History at the University of St Andrews; David Arnold, Professor of Asian and Global History at the University of Warwick; Chris Minkowski, Professor in Sanskrit at the University of Oxford

To celebrate the 200th anniversary of the birth of Charles Darwin in 2009 and the 150th anniversary of the publication of On the Origin of Species, Melvyn Bragg presents a series about Darwin's life and work.Melvyn visits Darwin's home at Down House in Kent. Despite ill health and the demands of his family, Darwin continued researching and publishing until his death in April 1882.Featuring contributions from Darwin biographer Jim Moore, geneticist at University College London Steve Jones, Darwin expert Alison Pearn of the Darwin Correspondence Project and former garden curator at Down House Nick Biddle.

To celebrate the 200th anniversary of the birth of Charles Darwin and the 150th anniversary of the publication of On the Origin of Species, Melvyn Bragg presents a series about Darwin's life and work.How Darwin was eventually persuaded to publish On the Origin of Species in November 1859 and the book's impact on fellow scientists and the general public.Featuring contributions from Darwin biographer Jim Moore, Steve Jones, geneticist at University College London, Jim Secord of the Darwin Correspondence Project and Johannes Vogel, Sandy Knapp and Judith Magee, all of the National History Museum.

To celebrate the 200th anniversary of the birth of Charles Darwin and the 150th anniversary of the publication of On the Origin of Species, Melvyn Bragg presents a series about Darwin's life and work.Darwin's expedition aboard the Beagle in December 1831 and how his work during the voyage influenced and provided evidence for his theories.Featuring contributions from Darwin biographer Jim Moore, Steve Jones, geneticist at University College London, David Norman, Fellow of Christ's College Cambridge and Jenny Clack, curator of the University.

To celebrate the 200th anniversary of the birth of Charles Darwin in 2009 and the 150th anniversary of the publication of On the Origin of Species, Melvyn Bragg presents a series about Darwin's life and work.Melvyn tells the story of Darwin's early life in Shropshire and discusses the significance of the three years he spent at Cambridge, where his interests shifted from religion to natural science.Featuring contributions from Darwin biographer Jim Moore, geneticist at University College London Steve Jones, fellow of Christ's College Cambridge David Norman and assistant librarian at Christ's College Cambridge Colin Higgins.

Melvyn Bragg and guests discuss the physics of time. When writing the Principia Mathematica, Isaac Newton declared his hand on most of the big questions in physics. He outlined the nature of space, explained the motions of the planets and conceived the operation of gravity. He also laid down the law on time declaring: “Absolute, true, and mathematical time, of itself and from its own nature, flows equably without relation to anything external.” For Newton time was absolute and set apart from the universe, but with the theories of Albert Einstein time became more complicated; it could be squeezed and distorted and was different in different places.Time is integral to our experience of things but we find it very difficult to think about. It may not even exist and yet seems written into the existence of absolutely everything. With Jim Al-Khalili, Professor of Theoretical Physics and Chair in the Public Engagement in Science at the University of Surrey; Monica Grady, Professor of Planetary and Space Sciences at the Open University and Ian Stewart, Professor of Mathematics at the University of Warwick.

Melvyn Bragg and guests discuss the history of scientific ideas about heat. As anyone who’s ever burnt their hand will testify – heat is a pretty commonplace concept. Cups of coffee cool down, microwaves reheat them, water boils at 100 degrees and freezes on cold winter nights.Behind the everyday experience of hot things lies a complex story of ideas spread across Paris, Manchester and particularly Glasgow. It’s a story of brewing vats and steam engines, of fridges, thermometers and the heat death of the universe. But most importantly, it was the understanding and harnessing of heat that helped make the modern world of industry, engineering and technology.With Simon Schaffer, Professor of History of Science at the University of Cambridge and Fellow of Darwin College; Hasok Chang, Professor of Philosophy of Science at University College London and Joanna Haigh, Professor of Atmospheric Physics at Imperial College London

Melvyn Bragg and guests examine the relationship between the mind and the brain as they discuss recent developments in Neuroscience. In the mid-19th century a doctor had a patient who had suffered a stroke. The patient was unable to speak save for one word. The word was ‘Tan’ which became his name. When Tan died, the doctor discovered damage to the left side of his brain and concluded that the ability to speak was housed there. This is how neuroscience used to work – by examining the dead or investigating the damaged – but now things have changed. Imaging machines and other technologies enable us to see the active brain in everyday life, to observe the activation of its cells and the mass firing of its neuron batteries. Our extraordinary new knowledge of how the brain works has challenged concepts of free will and consciousness and opened up new ways of understanding the brain. Yet these new ideas seem to conform to some old ideas such as Freudian Psychoanalysis. But what picture of the brain has emerged, how has our understanding of it changed and what are the implications for understanding that most mysterious and significant of all phenomena – the human mind?With Martin Conway, Professor of Psychology at the University of Leeds; Gemma Calvert, Professor of Applied Neuroimaging at WMG, University of Warwick and David Papineau, Professor of Philosophy of Science at King’s College London.

Melvyn Bragg and guests discuss Vitalism, an 18th and 19th century quest for the spark of life. On a dreary night in November 1818, a young doctor called Frankenstein completed an experiment and described it in his diary: “I collected the instruments of life around me, that I might infuse a spark of being into the lifeless thing that lay at my feet…By the glimmer of the half-extinguished light, I saw the dull yellow eye of the creature open…”Frankenstein may seem an outlandish tale, but Mary Shelley wrote it when science was alive with ideas about what differentiated the living from the dead. This was Vitalism, a belief that living things possessed some spark of life, some vital principle, perhaps even a soul, that distinguished the quick from the dead and lifted them above dull matter. Electricity was a very real candidate; when an Italian scientist called Luigi Galvani made dead frogs twitch by applying electricity he thought he had found it. Vitalists aimed at unlocking the secret of life itself and they raised questions about what life is that are unresolved to this day. With Patricia Fara, Fellow of Clare College and Affiliated Lecturer in the Department of History and Philosophy of Science at Cambridge University; Andrew Mendelsohn, Senior Lecturer in the History of Science and Medicine at Imperial College, University of London and Pietro Corsi, Professor of the History of Science at the University of Oxford.

Melvyn Bragg and guests discuss an iconic piece of 20th century maths - Gödel’s Incompleteness Theorems. In 1900, in Paris, the International Congress of Mathematicians gathered in a mood of hope and fear. The edifice of maths was grand and ornate but its foundations, called axioms, had been shaken. They were deemed to be inconsistent and possibly paradoxical. At the conference, a young man called David Hilbert set out a plan to rebuild the foundations of maths – to make them consistent, all encompassing and without any hint of a paradox. Hilbert was one of the greatest mathematicians that ever lived, but his plan failed spectacularly because of Kurt Gödel. Gödel proved that there were some problems in maths that were impossible to solve, that the bright clear plain of mathematics was in fact a labyrinth filled with potential paradox. In doing so Gödel changed the way we understand what mathematics is and the implications of his work in physics and philosophy take us to the very edge of what we can know.With Marcus du Sautoy, Professor of Mathematics at Wadham College, University of Oxford; John Barrow, Professor of Mathematical Sciences at the University of Cambridge and Gresham Professor of Geometry and Philip Welch, Professor of Mathematical Logic at the University of Bristol.

Melvyn Bragg and guests discuss the music of the spheres, the elegant and poetic idea that the revolution of the planets generates a celestial harmony of profound and transcendent beauty. In Shakespeare’s The Merchant of Venice the young Lorenzo woos his sweetheart with talk of the stars: “There’s not the smallest orb which thou behold’stBut in his motion like an angel sings,Still quiring to the young-eyed cherubins;Such harmony is in immortal souls;But whilst this muddy vesture of decayDoth grossly close it in, we cannot hear it.”The idea of music of the spheres ran through late antiquity and the medieval period into the Renaissance and its echoes could be heard in astrology and astronomy, in theology, and, of course, in music itself. Influenced by Pythagoras and Plato, it was discussed by Cicero, Boethius, Marcello Ficino and Johannes Kepler It affords us a glimpse into minds for which the universe was full of meaning, of strange correspondences and grand harmonies.With Peter Forshaw, Postdoctoral Fellow at Birkbeck, University of London; Jim Bennett, Director of the Museum of the History of Science at the University of Oxford and Angela Voss, Director of the Cultural Study of Cosmology and Divination at the University of Kent, Canterbury.

Melvyn Bragg and guests delve into the dark world of genetics under Joseph Stalin in discussing the career of Trofim Lysenko. In 1928, as America lurched towards the Wall Street Crash, Joseph Stalin revealed his master plan - nature was to be conquered by science, Russia to be made brutally, glitteringly modern and the world transformed by communist endeavour.Into the heart of this vision stepped Trofim Lysenko, a self-taught geneticist who promised to turn Russian wasteland into a grain-laden Garden of Eden. Today, Lysenko is a byword for fraud but in Stalin’s Russia his outlandish ideas about genetic inheritance and evolution became law. They reveal a world of science distorted by ideology, where ideas were literally a matter of life and death. To disagree with Lysenko risked the gulag and yet he destroyed Soviet Agriculture and damaged, perhaps irreparably, the Soviet Union’s capacity to fight and win the Cold War. With Robert Service, Professor of Russian History at the University of Oxford; Steve Jones, Professor of Genetics at University College London; Catherine Merridale, Professor of Contemporary History at Queen Mary, University of London.

Melvyn Bragg and guests discuss the strange mathematics of probability where heads or tails is a simple question with a far from simple answer. Gambling may be as old as the hills but probability as a mathematical discipline is a relative youngster. Probability is the field of maths relating to random events and, although commonplace now, the idea that you can pluck a piece of maths from the tumbling of dice, the shuffling of cards or the odds in the local lottery is a relatively recent and powerful one. It may start with the toss of a coin but probability reaches into every area of the modern world, from the analysis of society to the decay of an atom. With Marcus du Sautoy, Professor of Mathematics at the University of Oxford; Colva Roney-Dougal, Lecturer in Pure Mathematics at the University of St Andrews; Ian Stewart, Professor of Mathematics at the University of Warwick

Melvyn Bragg and guests discuss the history of ideas about the human brain. Since time immemorial people have puzzled over the brain and its functions. In the 5th century BC the Greek physician Hippocrates confidently asserted:“Men ought to know that from the brain and from the brain only arise our pleasures, joys, laughter and jests, as well as our sorrows, pains, grieves and tears.” This might suggest that people have never doubted the importance of the brain, but for Aristotle the heart was the ruler of the body and the seat of the soul. Only in the 17th century, with new scientific advances, did the true importance of the brain begin to be appreciated. In 1669 the Danish anatomist, Nicolaus Steno, still lamented that, “the brain, the masterpiece of creation, is almost unknown to us.”How far have our perceptions of how the brain works and what it symbolises changed over the centuries? And, in amongst the matter or our little grey cells, are we still searching for our souls? With Vivian Nutton, Professor of the History of Medicine at University College London; Jonathan Sawday, Professor of English Studies at the University of Strathclyde; Marina Wallace, Professor at the University of the Arts, London, Central St Martin’s College of Art and Design

Melvyn Bragg and guests discuss Newton’s Laws of Motion. In 1687 Isaac Newton attempted to explain the movements of everything in the universe, from a pea rolling on a plate to the position of the planets. It was a brilliant, vaultingly ambitious and fiendishly complex task; it took him three sentences. These are the three laws of motion with which Newton founded the discipline of classical mechanics and conjoined a series of concepts - inertia, acceleration, force, momentum and mass - by which we still describe the movement of things today. Newton’s laws have been refined over the years – most famously by Einstein - but they were still good enough, 282 years after they were published, to put Neil Armstrong on the Moon. With Simon Schaffer, Professor in History and Philosophy of Science at the University of Cambridge and Fellow of Darwin College; Raymond Flood, University Lecturer in Computing Studies and Mathematics and Senior Tutor at Kellogg College, University of Oxford; Rob Iliffe, Professor of Intellectual History and History of Science at the University of Sussex.

Melvyn Bragg and guests discuss the 19th century mathematician Ada Lovelace. Deep in the heart of the Pentagon is a network of computers. They control the US military, the most powerful army on the planet, but they are controlled by a programming language called Ada. It’s named after Ada Lovelace, the allegedly hard drinking 19th century mathematician and daughter of Lord Byron. In her work with Charles Babbage on a steam driven calculating machine called the Difference Engine, Ada understood, perhaps before anyone else, what a computer might truly be. As such the Difference Engine is the spiritual ancestor of the modern computer. Ada Lovelace has been called many things - the first computer programmer and a prophet of the computer age – but most poetically perhaps by Babbage himself as an ‘enchantress of numbers’. With Patricia Fara, Senior Tutor at Clare College, Cambridge; Doron Swade, Visiting Professor in the History of Computing at Portsmouth University; John Fuegi, Visiting Professor in Biography at Kingston University.

Melvyn Bragg and guests will be leaving the studio, the planet and indeed, the universe to take a tour of the Multiverse. If you look up the word ‘universe’ in the Oxford English Dictionary you will find the following definition: “The whole of created or existing things regarded collectively; all things (including the earth, the heavens, and all the phenomena of space) considered as constituting a systematic whole.” That sounds fairly comprehensive as a description of everything, but for an increasing number of physicists and cosmologists the universe is not enough. They talk of a multiverse – literally many universes – to explain aspects of their theory, the character of the universe and the riddle of our existence within it. Indeed, compared to the scope and complexity of the multiverse, the whole of our known reality may be as a speck of sand upon a beach.The idea of a multiverse is still controversial, some argue that it isn’t even science, because it is based on an idea that we may never be able to prove or even see. But what might a multiverse be like, why are physicists and cosmologists increasingly interested in it and is it really scientific to discuss the existence of universes we may never know anything With Martin Rees, President of the Royal Society and Professor of Cosmology and Astrophysics at the University of Cambridge; Fay Dowker, Reader in Theoretical Physics at Imperial College; Bernard Carr, Professor of Mathematics and Astronomy at Queen Mary, University of London

Melvyn Bragg and guests discuss how the science of plate tectonics revolutionised our understanding of the planet on which we live. America is getting further away from Europe. This is not a political statement but a geological fact. Just as the Pacific is getting smaller, the Red Sea bigger, the Himalayas are still going up and one day the Horn of Africa will be a large island. This is the theory of plate tectonics, a revolutionary idea in 20th century geology that claimed the continents of Earth were dancing to the music of deep time. A dance of incredible slowness, yet powerful enough to throw up the mountains and pour away the oceans.Plate tectonics, the idea that the earth’s surface moved on a carpet of molten magma, constituted a genuine scientific revolution in geology. It explained why mountains appeared and why earth quakes occurred; it explained the curious distribution of fossils across the globe and finally solved the age old conundrum of why continents such as Africa and South America appeared to fit together like a giant jigsaw puzzle. Plate tectonics has made geologists, and many more besides, profoundly re-think what the Earth was, how it worked and how it related to all the things in it. With Richard Corfield, Visiting Senior Lecturer in Earth Sciences at the Open University; Joe Cann, Senior Fellow in the School of Earth and Environment at the University of Leeds; Lynne Frostick, Director of the Hull Environment Research Institute and Professor of Physical Geography at the University of Hull

Melvyn Bragg and guests talk about blood, black bile, yellow bile and phlegm. These are the four humours, a theory of disease and health that is among the most influential ideas aver conceived. According to an 11th century Arabic book called the Almanac of Health, an old man went to the doctor complaining of a frigid complexion and stiffness in winter. The doctor, after examining his condition, prescribed a rooster. Being a hot and dry bird it was the perfect tonic for a cold and rheumatic old man. This is medicine by the four humours. The idea that the body is a concoction of these four essential juices is one of the oldest on record. From the Ancient Greeks to the 19th century it explained disease, psychology, habit and personality. When we describe people as being choleric, sanguine or melancholic we are still using the language of the humours today. It also explains why, in the long and convoluted history of medical practice, pigeon livers were an aphrodisiac, blood letting was a form of heroism (and best done in spring) and why you really could be frightened to death. The theory was dismantled from the 17th century but in its belief that the mind and body are intimately connected and that health requires equilibrium the humours retain an influence to this dayWith David Wootton, Anniversary Professor of History at the University of York; Vivian Nutton, Professor of the History of Medicine at University College London; Noga Arikha, Visiting Fellow at the Institut Jean-Nicod in Paris

Melvyn Bragg and guests discuss mutation in genetics and evolution. When lying mortally ill with cancer, the British geneticist J.B.S. Haldane penned the following lines: Cancer's a Funny Thing:I wish I had the voice of HomerTo sing of rectal carcinoma,Which kills a lot more chaps, in fact,Than were bumped off when Troy was sacked...Haldane knew better than most that many cancers, and many other diseases, are caused by genetic mutation. A mutation is an error in reproduction between one generation and the next as the copying mechanism that allows you to inherit your parent’s genes goes awry. Mutations are almost always bad news for the organism that suffers them and yet mutation is also a giver of life. Without it there would be no natural selection, no evolution and, arguably, no life on this planet. It’s not unreasonable to see life itself as a mutation and to understand this may also hold the key to aging and disease. It is, in the Darwinian view of life, the raw material of evolution.With Steve Jones, Professor of Genetics in the Galton Laboratory, University College London; Adrian Woolfson, lectures in Medicine at Cambridge University; Linda Partridge, Weldon Professor of Biometry at University College LondonTags

Melvyn Bragg and guests discuss the Fibonacci Sequence. Named after a 13th century Italian Mathematician, Leonardo of Pisa who was known as Fibonacci, each number in the sequence is created by adding the previous two together. It starts 1 1 2 3 5 8 13 21 and goes on forever. It may sound like a piece of mathematical arcania but in the 19th century it began to crop up time and again among the structures of the natural world, from the spirals on a pinecone to the petals on a sunflower.The Fibonacci sequence is also the mathematical first cousin of the Golden Ratio – a number that has haunted human culture for thousands of years. For some, the Golden ratio is the essence of beauty found in the proportions of the Parthenon and the paintings of Leonardo Da Vinci. With Marcus du Sautoy, Professor of Mathematics at the University of Oxford; Jackie Stedall, Junior Research Fellow in History of Mathematics at Queen’s College, Oxford; Ron Knott, Visiting Fellow in the Department of Mathematics at the University of Surrey

Melvyn Bragg discusses the discovery of Oxygen by Joseph Priestley and Antoine Lavoisier. In the late 18th century Chemistry was the prince of the sciences – vital to the economy, it shaped how Europeans fought each other, ate with each other, what they built and the medicine they took. And then, in 1772, the British chemist, Joseph Priestley, stood in front of the Royal Society and reported on his latest discovery: “this air is of exalted nature…A candle burned in this air with an amazing strength of flame; and a bit of red hot wood crackled and burned with a prodigious rapidity. But to complete the proof of the superior quality of this air, I introduced a mouse into it; and in a quantity in which, had it been common air, it would have died in about a quarter of an hour; it lived at two different times, a whole hour, and was taken out quite vigorous.” For the British dissenting preacher, Joseph Priestley, and the French aristocrat, Antoine Lavoisier, Chemistry was full of possibilities and they pursued them for scientific and political ends. But they came to blows over oxygen because they both claimed to have discovered it, provoking a scientific controversy that rattled through the laboratories of France and England until well after their deaths. To understand their disagreement is to understand something about the nature of scientific discovery itself. With Simon Schaffer, Professor in History and Philosophy of Science at the University of Cambridge; Jenny Uglow, Honorary Visiting Professor at the University of Warwick; Hasok Chang, Reader in Philosophy of Science at University College London.

Melvyn Bragg and guests discuss Antimatter, a type of particle predicted by the British physicist, Paul Dirac. Dirac once declared that “The laws of nature should be expressed in beautiful equations”. True to his word, he is responsible for one of the most beautiful. Formulated in 1928, it describes the behaviour of electrons and is called the Dirac equation. But the Dirac equation is strange. For every question it gives two answers – one positive and one negative. From this its author concluded that for every electron there is an equal and opposite twin. He called this twin the anti-electron and so the concept of antimatter was born.Despite its popularity with Science Fiction writers, antimatter is relatively mundane in physics – we have created antimatter in the laboratory and we even use it in our hospitals. But one fundamental question remains – why isn’t there more antimatter in the universe. Answering that question will involve developing new physics and may take us closer to understanding events at the origin of the universe. With Val Gibson, Reader in High Energy Physics at the University of Cambridge; Frank Close, Professor of Physics at Exeter College, University of Oxford; Ruth Gregory, Professor of Mathematics and Physics at the University of Durham

Melvyn Bragg and guests discuss the Permian-Triassic boundary. 250 million years ago, in the Permian period of geological time, the most ferocious predators on earth were the Gorgonopsians. Up to ten feet in length, they had dog-like heads and huge sabre-like teeth. Mammals in appearance, their eyes were set in the side of their heads like reptiles. They looked like a cross between a lion and giant monitor lizard and were so ugly that they are named after the gorgons from Greek mythology – creatures that turned everything that saw them to stone. Fortunately, you’ll never meet a gorgonopsian or any of their descendants because they went extinct at the end of the Permian period. And they weren’t alone. Up to 95% of all life died with them. It’s the greatest mass extinction the world has ever known and it marks what is called the Permian-Triassic boundary. But what caused this catastrophic juncture in life, what evidence do we have for what happened and what do events like this tell us about the pattern and process of evolution itself?With Richard Corfield, Senior Lecturer in Earth Sciences at the Open University; Mike Benton, Professor of Vertebrate Palaeontology in the Department of Earth Sciences at the University of Bristol; Jane Francis, Professor of Palaeoclimatology at the University of Leeds

Melvyn Bragg and guests discuss Renaissance Astrology. In Act I Scene II of King Lear, the ne’er do well Edmund steps forward and rails at the weakness and cynicism of his fellow men:This is the excellent foppery of the world, that,when we are sick in fortune, - often the surfeitof our own behaviour, - we make guilty of ourdisasters the sun, the moon, and the stars: asif we were villains by necessity.The focus of his attack is astrology and the credulity of those who fall for its charms. But the idea that earthly life was ordained in the heavens was essential to the Renaissance understanding of the world. The movements of the heavens influenced many things from the practice of medicine to major political decisions. Every renaissance court had its astrologer including Elizabeth Ist and the mysterious Dr. John Dee who chose the most propitious date for her coronation. But astrologers also worked in the universities and on the streets, reading horoscopes, predicting crop failures and rivalling priests and doctors as pillars of the local community. But why did astrological ideas flourish in the period, how did astrologers interpret and influence the course of events and what new ideas eventually brought the astrological edifice tumbling down? With Peter Forshaw, Lecturer in Renaissance Philosophies at Birkbeck, University of London; Lauren Kassell, Lecturer in the History and Philosophy of Science at the University of Cambridge; and Jonathan Sawday, Professor of English Studies at the University of Strathclyde.

Melvyn Bragg and guests discuss mysterious phenomena called Gravitational Waves in contemporary physics. The rather un-poetically named star SN 2006gy is roughly 150 times the size of our sun. Last week it went supernova, creating the brightest stellar explosion ever recorded. But among the vast swathes of dust, gas and visible matter ejected into space, perhaps the most significant consequences were invisible – emanating out from the star like the ripples from a pebble thrown into a pond. They are called Gravitational Waves, predicted by Einstein and much discussed since, their existence has never actually been proved but now scientists may be on the verge of measuring them directly. To do so would give us a whole new way of seeing the cosmos. But what are gravitational waves, why are scientists trying to measure them and, if they succeed, what would a gravitational picture of the universe look like?With Jim Al-Khalili, Professor of Physics at the University of Surrey; Carolin Crawford, Royal Society Research Fellow at the Institute of Astronomy, Cambridge; Sheila Rowan, Professor in Experimental Physics in the Department of Physics and Astronomy at the University of Glasgow

Melvyn Bragg and guests discuss symmetry. Found in Nature - from snowflakes to butterflies - and in art in the music of Bach and the poems of Pushkin, symmetry is both aesthetically pleasing and an essential tool to understanding our physical world. The Greek philosopher Aristotle described symmetry as one of the greatest forms of beauty to be found in the mathematical sciences, while the French poet Paul Valery went further, declaring; “The universe is built on a plan, the profound symmetry of which is somehow present in the inner structure of our intellect”.The story of symmetry tracks an extraordinary shift from its role as an aesthetic model - found in the tiles in the Alhambra and Bach's compositions - to becoming a key tool to understanding how the physical world works. It provides a major breakthrough in mathematics with the development of group theory in the 19th century. And it is the unexpected breakdown of symmetry at sub-atomic level that is so tantalising for contemporary quantum physicists.So why is symmetry so prevalent and appealing in both art and nature? How does symmetry enable us to grapple with monstrous numbers? And how might symmetry contribute to the elusive Theory of Everything?With Fay Dowker, Reader in Theoretical Physics at Imperial College, London; Marcus du Sautoy, Professor of Mathematics at the University of Oxford; Ian Stewart, Professor of Mathematics at the University of Warwick.

Melvyn Bragg and guests discuss the history of anaesthetics, from laughing gas in the 1790s to the discovery of “blessed chloroform”. Remembering his unsuccessful stint at Edinburgh Medical school Charles Darwin described the horrors of surgery before anaesthetics : "I attended the operating theatre and saw two very bad operations... but I rushed away before they were completed. Nor did I ever attend again, for hardly any inducement would have been strong enough to make me do so; this being long before the blessed days of chloroform. The two cases fairly haunted me for many a long year."The suffering Darwin witnessed is almost unimaginable. In the 19th Century, a simple fracture often led to amputation carried out on a conscious patient, whose senses would be dulled only by brandy or perhaps some morphine. Many patients died of shock.The properties of gases like nitrous oxide or “laughing gas” held out hope. The chemist Humphrey Davy in the 1790s described it as “highly pleasurable, thrilling”. He also noticed his toothache disappeared. But he failed to apply his observations and it wasn't until the 1840s that there was a major breakthrough in anaesthetics, when an enterprising dentist in Boston managed to anaesthetize a patient with ether. It became known as the “Yankee Dodge”. Ether had its drawbacks and the search for a suitable alternative continued until chloroform was tried in 1847, winning many admirers including Queen Victoria, the first English royal to use it. So why did it take so long for inhaled gases to advance from providing merely recreational highs to providing an essential tool of humane surgery? What role did the development of the atomic bomb play in the development of anaesthetics? And how have society's changing attitudes to pain informed the debate?With David Wilkinson, Consultant Anaesthetist at St Bartholomew’s Hospital in London and President of the History of Anaesthesia Society; Stephanie Snow, Research Associate at the Centre for the History of Science, Technology & Medicine at the University of Manchester; Anne Hardy, Professor in the History of Modern Medicine at University College London

Melvyn Bragg and guests discuss the history of microbiology. We have more microbes in our bodies than we have human cells. We fear them as the cause of disease, yet are reliant on them for processes as diverse as water purification, pharmaceuticals, bread-making and brewing. In the future, we may look to them to save the planet from environmental hazards as scientists exploit their ability to clean up pollution. For microbes are the great recyclers on the earth, processing everything – plants, animals and us. Without microbes life would grind to a halt. How did we first discover these invisible masters of the universe? The development of microscopes in the 17th Century played a key part, but for a while science seemed stuck in this purely observational role. It is only when Louis Pasteur and Robert Koch began to manipulate microbes in the lab two hundred years later that stunning advances were made. These breakthroughs led to an understanding of how microbes transform matter, spread disease and also prevent it with the development of antibiotics and vaccines.With John Dupré, Professor of Philosophy of Science at Exeter University; Anne Glover, Professor of Molecular and Cell Biology at Aberdeen University; and Andrew Mendelsohn, Senior Lecturer in the History of Science and Medicine at Imperial College, University of London

Melvyn Bragg and guests discuss the history of optics. From telescopes to microscopes, from star-gazing to the intimacies of a magnified flea. As Galileo turned his telescope to the heavens in the early 1600s, Kepler began to formulate a theory of optics. The new and improving instruments went hand in hand with radical new ideas about how we see and what we see. Spectacles allowed scholars to study long into the evening (and into old age), while giant telescopes, up to 100 feet long, led to the discovery of planets and attempts to map the universe. The craze for optical trickery swept Europe with enthusiastic amateurs often providing valuable discoveries. But this new view of the world through a lens raised questions too – how much can you rely on the senses, on what you see? The further into space you can spy, the larger and more unmanageable the universe becomes. At the same time, the microscope was utterly transforming the world close at hand.So how did these developments inform ideas of knowledge? If new methods of scientific observation support an empirical approach, what does this mean for divine, innate reason?With Simon Schaffer, Professor in History and Philosophy of Science at the University of Cambridge; Jim Bennett, Director of the Museum of the History of Science and Fellow of Linacre College at the University of Oxford; Emily Winterburn, Curator of Astronomy at the National Maritime Museum

Melvyn Bragg and guests discuss one of the most important philosophers of the 20th century, Karl Popper whose ideas about science and politics robustly challenged the accepted ideas of the day. He strongly resisted the prevailing empiricist consensus that scientists' theories could be proved true.Popper wrote: “The more we learn about the world and the deeper our learning, the more conscious, specific and articulate will be our knowledge of what we do not know, our knowledge of our ignorance”. He believed that even when a scientific principle had been successfully and repeatedly tested, it was not necessarily true. Instead it had simply not proved false, yet! This became known as the theory of falsification.He called for a clear demarcation between good science, in which theories are constantly challenged, and what he called “pseudo sciences” which couldn't be tested. His debunking of such ideologies led some to describe him as the “murderer of Freud and Marx”. He went on to apply his ideas to politics, advocating an Open Society. His ideas influenced a wide range of politicians, from those close to Margaret Thatcher, to thinkers in the Eastern Communist bloc and South America.So how did Karl Popper change our approach to the philosophy of science? How have scientists and philosophers made use of his ideas? And how are his theories viewed today? Are we any closer to proving scientific principles are “true”?With John Worrall, Professor of Philosophy of Science at the London School of Economics; Anthony O'Hear, Weston Professor of Philosophy at Buckingham University; Nancy Cartwright, Professor of Philosophy at the LSE and the University of California

Melvyn Bragg and guests discuss the Greek mathematician Archimedes. Reputed to have shouted “Eureka!” as he leapt from his bath having discovered the principles of floating bodies. Whatever the truth of the myths surrounding the man, he was certainly one of the world’s great mathematicians. The practical application of his work in pulleys and levers created formidable weapons such as catapults and ship tilting systems, allowing his home city in Sicily to defend itself against the Romans. “Give me a place to stand and I will move the earth”, he declared.But despite these triumphs, his true love remained maths for maths sake. Plutarch writes: “He placed his whole affection and ambition in those purer speculations where there can be no reference to the vulgar needs of life.” His most important breakthroughs came in the field of geometry with his work on the areas and volumes of curved objects.So how did this Greek mathematician in the third century BC arrive at a calculation of Pi? Did he really create a Death Ray to fight off invading ships? And what does a recently discovered manuscript reveal about his methods?With Jackie Stedall, Junior Research Fellow in the History of Mathematics at Queen's College, Oxford; Serafina Cuomo, Reader in the History of Science at Imperial College London; George Phillips, Honorary Reader in Mathematics at St Andrews University

Melvyn Bragg and guests discuss the Jesuits, a Catholic religious order of priests who became known as “the school masters of Europe”. Founded in the 16th century by the soldier Ignatius Loyola, they became a major force throughout the world, from China to South America. “Give us a boy and we will return you a man, a citizen of his country and a child of God”, they declared. By the 17th century there were more than 500 schools established across Europe. Their ideas about a standardised curriculum and teaching became the basis for many education systems today.They were also among the greatest patrons of art in early modern Europe, using murals and theatre to get their message across. To their enemies they were a sinister collective whose influence reached into the courts of kings. Their wealth and their adaptability to local customs abroad provoked suspicion, prompting their eventual suppression in the late 18th century. They were re-established in 1814 and now have more than twenty thousand members.So why was education so important to the Jesuit movement? How much influence did they really have in the courts and colonies of Europe? And were they really at the heart of conspiracies to murder kings?With Nigel Aston, Reader in Early Modern History at the University of Leicester; Simon Ditchfield, Reader in History at the University of York; Dame Olwen Hufton, Emeritus Fellow of Merton College, Oxford.

Melvyn Bragg and guests discuss the planet Mars. Named after the Roman god of war, Mars has been a source of continual fascination. It is one of our nearest neighbours in space, though it takes about a year to get there. It is very inhospitable with high winds racing across extremely cold deserts. But it is spectacular, with the highest volcano in the solar system and a giant chasm that dwarfs the Grand Canyon.For centuries there has been fierce debate about whether there is life on Mars and from the 19th century it was even thought there might be a system of canals on the planet. This insatiable curiosity has been fuelled by writers like HG Wells and CS Lewis and countless sci-fi films about little green men.So what do we know about Mars – its conditions, now and in the past? What is the evidence that there might be water and thus life on Mars? And when might we expect man to walk on its surface?With John Zarnecki, Professor of Space Science at the Open University and a team leader on the ExoMars mission; Colin Pillinger, Professor of Planetary Sciences at the Open University and leader of the Beagle 2 expedition to Mars; Monica Grady, Professor of Planetary and Space Sciences at the Open University and an expert on Martian meteorites.

Melvyn Bragg and guests discuss the contribution Indian mathematicians have made to our understanding of the subject. Mathematics from the Indian subcontinent has provided foundations for much of our modern thinking on the subject. They were thought to be the first to use zero as a number. Our modern numerals have their roots there too. And mathematicians in the area that is now India, Pakistan and Bangladesh were grappling with concepts such as infinity centuries before Europe got to grips with it. There’s even a suggestion that Indian mathematicians discovered Pythagoras’ theorem before Pythagoras. Some of these advances have their basis in early religious texts which describe the geometry necessary for building falcon-shaped altars of precise dimensions. Astronomical calculations used to decide the dates of religious festivals also encouraged these mathematical developments. So how were these advances passed on to the rest of the world? And why was the contribution of mathematicians from this area ignored by Europe for centuries?With George Gheverghese Joseph, Honorary Reader in Mathematics Education at Manchester University; Colva Roney-Dougal, Lecturer in Pure Mathematics at the University of St Andrews; Dennis Almeida, Lecturer in Mathematics Education at Exeter University and the Open University.

Melvyn Bragg and guests discuss the speed of light. Scientists and thinkers have been fascinated with the speed of light for millennia. Aristotle wrongly contended that the speed of light was infinite, but it was the 17th Century before serious attempts were made to measure its actual velocity – we now know that it’s 186,000 miles per second. Then in 1905 Einstein’s Special Theory of Relativity predicted that nothing can travel faster than the speed of light. This then has dramatic effects on the nature of space and time. It’s been thought the speed of light is a constant in Nature, a kind of cosmic speed limit, now the scientists aren’t so sure. With John Barrow, Professor of Mathematical Sciences and Gresham Professor of Astronomy at Cambridge University; Iwan Morus, Senior Lecturer in the History of Science at The University of Wales, Aberystwyth; Jocelyn Bell Burnell, Visiting Professor of Astrophysics at Oxford University.

Melvyn Bragg and guests discuss the Poincaré Conjecture. The great French mathematician Henri Poincaré declared: “The scientist does not study mathematics because it is useful; he studies it because he delights in it, and he delights in it because it is beautiful. If nature were not beautiful, it would not be worth knowing and life would not be worth living. And it is because simplicity, because grandeur, is beautiful that we preferably seek simple facts, sublime facts, and that we delight now to follow the majestic course of the stars.” Poincaré’s ground-breaking work in the 19th and early 20th century has indeed led us to the stars and the consideration of the shape of the universe itself. He is known as the father of topology – the study of the properties of shapes and how they can be deformed. His famous Conjecture in this field has been causing mathematicians sleepless nights ever since. He is also credited as the Father of Chaos Theory.So how did this great polymath change the way we understand the world and indeed the universe? Why did his conjecture remain unproved for almost a century? And has it finally been cracked?With June Barrow-Green, Lecturer in the History of Mathematics at the Open University; Ian Stewart, Professor of Mathematics at the University of Warwick; Marcus du Sautoy, Professor of Mathematics at the University of Oxford.

Melvyn Bragg and guests discuss the Needham Question; why Europe and not China developed modern technology. What do these things have in common? Fireworks, wood-block printing, canal lock-gates, kites, the wheelbarrow, chain suspension bridges and the magnetic compass. The answer is that they were all invented in China, a country that, right through the Middle Ages, maintained a cultural and technological sophistication that made foreign dignitaries flock to its imperial courts for trade and favour. But then, around 1700, the flow of ingenuity began to dry up and even reverse as Europe bore the fruits of the scientific revolution back across the globe. Why did Modern Science develop in Europe when China seemed so much better placed to achieve it? This is called the Needham Question, after Joseph Needham, the 20th century British Sinologist who did more, perhaps, than anyone else to try and explain it.But did Joseph Needham give a satisfactory answer to the question that bears his name? Why did China’s early technological brilliance not lead to the development of modern science and how did momentous inventions like gunpowder and printing enter Chinese society with barely a ripple and yet revolutionise the warring states of Europe? With Chris Cullen, Director of the Needham Research Institute in Cambridge; Tim Barrett, Professor of East Asian History at SOAS; Frances Wood, Head of Chinese Collections at the British Library.

Melvyn Bragg and guests discuss the Prussian naturalist and explorer Alexander Von Humboldt. He was possibly the greatest and certainly one of the most famous scientists of the 19th century. Darwin described him as 'the greatest scientific traveller who ever lived'. Goethe declared that one learned more from an hour in his company than eight days of studying books and even Napoleon was reputed to be envious of his celebrity.A friend of Goethe and an influence on Coleridge and Shelly, when Darwin went voyaging on the Beagle it was Humboldt's works he took for inspiration and guidance. At the time of his death in 1859, the year Darwin published On the Origin of Species, Humboldt was probably the most famous scientist in Europe. Add to this shipwrecks, homosexuality and Spanish American revolutionary politics and you have the ingredients for one of the more extraordinary lives lived in Europe (and elsewhere) in the 18th and 19th centuries. But what is Humboldt's true position in the history of science? How did he lose the fame and celebrity he once enjoyed and why is he now, perhaps, more important than he has ever been? With Jason Wilson, Professor of Latin American Literature at University College London, Patricia Fara, Affiliated Lecturer in the Department of History and Philosophy of Science at the University of Cambridge, Jim Secord, Professor in the Department of History and Philosophy of Science at the University of Cambridge and Director of the Darwin Correspondence Project.

Melvyn Bragg and guests discuss the galaxies. Spread out across the voids of space like spun sugar, but harbouring in their centres super-massive black holes. Our galaxy is about 100,000 light years across, is shaped like a fried egg and we travel inside it at approximately 220 kilometres per second. The nearest one to us is much smaller and is nicknamed the Sagittarius Dwarf. But the one down the road, called Andromeda, is just as large as ours and, in 10 billion years, we'll probably crash into it. Galaxies - the vast islands in space of staggering beauty and even more staggering dimension. But galaxies are not simply there to adorn the universe; they house much of its visible matter and maintain the stars in a constant cycle of creation and destruction. But why do galaxies exist, how have they evolved and what lies at the centre of a galaxy to make the stars dance round it at such colossal speeds? With John Gribbin, Visiting Fellow in Astronomy at the University of Sussex; Carolin Crawford, Royal Society University Research Fellow at the Institute of Astronomy at Cambridge; Robert Kennicutt, Plumian Professor of Astronomy and Experimental Philosophy at the University of Cambridge.

Melvyn Bragg and guests discuss Carbon. It forms the basis of all organic life and has the amazing ability to bond with itself and a wide range of other elements, forming nearly 10 million known compounds. It is in the food we eat, the clothes we wear, the shampoo we use and the petrol that fuels our cars. Because carbon has the largest range of subtle bonding capabilities, 95% of everything that exists in the universe is made up of carbon atoms that are stuck together. It is an extraordinary element for many reasons: the carbon-nitrogen cycle provides some of the energy produced by the Sun and the stars; it has the highest melting point of all the elements; and its different forms include one of the softest and one of the hardest substances known. What gives carbon its great ability to bond with other atoms? What is the significance of the recent discovery of a new carbon molecule - the C60? What role does carbon play in the modern chemistry of nanotechnology? And how should we address the problem of our diminishing carbon energy sources? With Harry Kroto, Professor of Chemistry at Florida State University; Monica Grady, Professor of Planetary and Space Sciences at the Open University; Ken Teo, Royal Academy of Engineering Research Fellow at Cambridge University.

Melvyn Bragg and guests discuss the heart. Aristotle considered the heart to be the seat of thought, reason and emotion. The Roman physician Galen located the seat of the passions in the liver, the seat of reason in the brain, and considered the heart to be the seat of the emotions. It was not until the 17th century that the physician William Harvey wrote in the preface to his thesis On the Motion of the Heart and Blood in Animals, a letter addressed to King Charles I. 'The heart of animals is the foundation of their life, the sovereign of everything within them...from which all power proceeds. The King, in like manner, is the foundation of his kingdom, the sun of the world around him, the heart of the republic, the foundation whence all power, all grace doth flow'. Harvey was probably wise to address the King in this manner, for what he laid out in his groundbreaking text challenged scientific wisdom that had gone unquestioned for centuries about the true function of the heart. Organs had been seen in a hierarchical structure with the heart as the pinnacle. But Harvey transformed the metaphor into something quite different: the heart as a mechanistic pumping device. How had the Ancient Greeks and Islamic physicians understood the heart? What role did the bodily humours play in this understanding? Why has the heart always been seen as the seat of emotion and passion? And why was it that despite Harvey's discoveries about the heart and its function, this had limited implications for medical therapy and advancement? With David Wootton, Anniversary Professor of History at the University of York; Fay Bound Alberti, Research Fellow at the Wellcome Unit for the History of Medicine at the University of Manchester; Jonathan Sawday, Professor of English Studies at the University of Strathclyde.

Melvyn Bragg and guests discuss the relationship between astronomy and the British Empire. The 18th century explorer and astronomer James Cook wrote: 'Ambition leads me not only farther than any other man has been before me, but as far as I think it possible for man to go'. Cook's ambition took him to the far reaches of the Pacific and led to astronomical observations which measured the distance of Venus to the Sun with unprecedented accuracy. Cook's ambition was not just personal and astronomical. It represented the colonial ambition of the British Empire which was linked inextricably with science and trade. The discoveries about the Transit of Venus, made on Cook's voyage to Tahiti, marked the beginning of a period of expansion by the British which relied on maritime navigation based on astronomical knowledge. With Simon Schaffer, Professor in History and Philosophy of Science at the University of Cambridge; Kristen Lippincott, former Director of the Royal Observatory, Greenwich; Allan Chapman, Historian of Science at the History Faculty at Oxford University.

Melvyn Bragg and guests discuss the search for immunisation. In 1717, Lady Mary Wortley Montagu, the wife of the British Ambassador to the Ottoman Empire, wrote a letter to her friend describing how she had witnessed the practice of smallpox inoculation in Constantinople. This involved the transfer of material from a smallpox postule into multiple cuts made in a vein. Lady Montagu had lost her brother to smallpox and was amazed that the Middle Eastern practice of inoculation rendered the fatal disease harmless. In Britain, the practice was unknown. Inoculation was an early attempt at creating immunity to disease, but was later dismissed when Edward Jenner pioneered immunisation through vaccination in 1796. Vaccination was hailed a huge success. Napoleon described it as the greatest gift to mankind, but when the British government introduced the compulsory Vaccination Act in 1853, targeted at the poor and the working class, it sparked a mass opposition movement.How did a Gloucestershire country surgeon become known as the father of vaccination? Why did the British government introduce compulsory smallpox vaccination in 1853? What were the consequences of those who opposed it? And how was the disease finally eradicated? With Nadja Durbach, Associate Professor of History at the University of Utah, Chris Dye, Co-ordinator of the World Health Organisation's work on tuberculosis epidemiology, Sanjoy Bhattacharya, Lecturer in the Wellcome Trust Centre for the History of Medicine at UCL

Melvyn Bragg and guests discuss the formation of the Royal Society. In the 17th century the natural philosopher Francis Bacon heralded the new age of science. The frontispiece to his 1620 edition of the Instauratio Magna depicted a galleon travelling between the metaphorical Pillars of Hercules thought to lie at the Strait of Gibraltar and believed to mark the end of the known world. The image encapsulated Bacon's desire to sail beyond the limits set by Aristotle and the curriculum of the Ancient universities towards the new continent of science. Bacon imagined practical scientists engaged in a collaborative effort to expand knowledge of the natural world. But it was not until the turbulence of the Civil War and Commonwealth years had passed that such a group of scientists would gather together in London for this purpose, and form the Royal Society. Amongst its members were Robert Boyle, Robert Hooke, Christopher Wren and Isaac Newton, who explicitly rejected dogma and insisted on practical experimentation and observation. How was the Royal Society formed against a backdrop of religious and political strife? What was it about the way this group of men worked that allowed each individual to flourish in his own field? How successful was the Royal Society in disseminating the benefits of experimental science and what is its enduring legacy? With Stephen Pumfrey, Senior Lecturer in the History of Science at the University of Lancaster; Lisa Jardine, Professor of Renaissance Studies at Queen Mary, University of London; Michael Hunter, Professor of History at Birkbeck, University of London.

Melvyn Bragg and guests discuss negative numbers, a history of mystery and suspicion. In 1759 the British mathematician Francis Maseres wrote that negative numbers "darken the very whole doctrines of the equations and make dark of the things which are in their nature excessively obvious and simple". Because of their dark and mysterious nature, Maseres concluded that negative numbers did not exist, as did his contemporary, William Friend. However, other mathematicians were braver. They took a leap into the unknown and decided that negative numbers could be used during calculations, as long as they had disappeared upon reaching the solution. The history of negative numbers is one of stops and starts. The trailblazers were the Chinese who by 100 BC were able to solve simultaneous equations involving negative numbers. The Ancient Greeks rejected negative numbers as absurd, by 600 AD, the Indians had written the rules for the multiplication of negative numbers and 400 years later, Arabic mathematicians realised the importance of negative debt. But it wasn't until the Renaissance that European mathematicians finally began to accept and use these perplexing numbers. Why were negative numbers considered with such suspicion? Why were they such an abstract concept? And how did they finally get accepted? With Ian Stewart , Professor of Mathematics at the University of Warwick; Colva Roney-Dougal , Lecturer in Pure Mathematics at the University of St Andrews; Raymond Flood , Lecturer in Computing Studies and Mathematics at Kellogg College, Oxford.

Melvyn Bragg and guests discuss the story of human evolution, which stretches back over six million years. It is not the story of one species but of several diverse species, some of whom walked the Earth at the same time. From the earliest hominids to the early Homo sapiens, there was nothing inevitable about the course of human evolution. But what conditions created the opportunity for diverse human species to thrive? What environmental factors led to the survival of one human species, but contributed to the extinction of so many others? What can the fossil record and the science of genetics tell us about our ancestors? How does the brain make modern man so unique in the natural world? With Steve Jones, Professor of Genetics in the Galton Laboratory at University College London; Fred Spoor, Professor of Evolutionary Anatomy at University College London; Margaret Clegg, Honorary Research Fellow in the Department of Biological Anthropology at University College London.

Melvyn Bragg and guests discuss relativism, a philosophy of shifting sands. "Today, a particularly insidious obstacle to the task of educating is the massive presence in our society and culture of that relativism which, recognizing nothing as definitive, leaves as the ultimate criterion only the self with its desires. And under the semblance of freedom it becomes a prison for each one, for it separates people from one another, locking each person into his or her own 'ego'." Pope Benedict XVI, in a speech given in June 2005, showed that the issue of relativism is as contentious today as it was in Ancient Greece, when Plato took on the relativist stance of Protagoras and the sophists. Relativism is a school of philosophical thought which holds to the idea that there are no absolute truths. Instead, truth is situated within different frameworks of understanding that are governed by our history, culture and critical perspective. Why has relativism so radically divided scholars and moral custodians over the centuries? How have its supporters answered to criticisms that it is inherently unethical? And if there are universal standards such as human rights, how do relativists defend culturally specific practices such as honour killings or female infanticide? With Barry Smith, Senior Lecturer in Philosophy at Birkbeck College, University of London; Jonathan Rée, freelance philosopher who holds visiting professorships at the Royal College of Art and Roehampton University; Kathleen Lennon, Senior Lecturer in Philosophy at the University of Hull.

Melvyn Bragg and guests discuss prime numbers: 2, 3, 5, 7, 11, 13, 17 … This sequence of numbers goes on literally forever. Recently, a team of researchers in Missouri successfully calculated the highest prime number - it has 9.1 million digits. For nearly two and a half thousand years, since Euclid first described the prime numbers in his book Elements, mathematicians have struggled to write a rule to predict what comes next in the sequence. The Swiss mathematician Leonhard Euler feared that it is "a mystery into which the human mind will never penetrate." But others have been more hopeful... In the middle of the nineteenth century, the German mathematician Bernhard Riemann discovered a connection between prime numbers and a complex mathematical function called the 'zeta function'. Ever since, mathematicians have laboured to prove the existence of this connection and reveal the rules behind the elusive sequence. What exactly are prime numbers and what secrets might they unlock about our understanding of atoms? What are the rules that may govern the prime sequence? And is it possible that the person who proves Riemann's Hypothesis may bring about the collapse of the world financial system? With Marcus du Sautoy, Professor of Mathematics and Fellow of Wadham College at the University of Oxford; Robin Wilson, Professor of Pure Mathematics at the Open University and Gresham Professor of Geometry; Jackie Stedall, Junior Research Fellow in the History of Mathematics at Queen's College, Oxford.

Melvyn Bragg and guests discuss artificial intelligence. Can machines think? It was a question posed by the mathematician and Bletchley Park code breaker Alan Turing and it is a question still being asked today. What is the difference between men and machines and what does it mean to be human? And if we can answer that question, is it possible to build a computer that can imitate the human mind? There are those who have always had robust answers to the questions that those who seek to create artificial intelligence have posed. In 1949 the eminent neurosurgeon, Professor Geoffrey Jefferson argued that the mechanical mind could never rival a human intelligence because it could never be conscious of what it did: "Not until a machine can write a sonnet or compose a concerto because of thoughts and emotions felt", he declared "and not by the chance fall of symbols, could we agree that machine equals brain - that is, not only write it but know that it had written it." Yet the quest rolled on for machines that were bigger and better at processing symbols and calculating infinite permutations. Who were the early pioneers of artificial intelligence and what drove them to imitate the operations of the human mind? Is intelligence the defining characteristic of humanity? And how has the quest for artificial intelligence been driven by warfare and conflict in the twentieth century? With Jon Agar, Lecturer in the History and Philosophy of Science, University of Cambridge; Alison Adam, Professor of Information Systems, Salford University; Igor Aleksander, Professor of Neural Systems Engineering at Imperial College, University of London.

Melvyn Bragg and guests discuss the search for the Graviton particle. Albert Einstein said "I know why there are so many people who love chopping wood. In this activity one immediately sees the results". Einstein spent the last thirty years of his life trying to find a theory that would unify electromagnetism with gravity, but success eluded him. The search is still on for a unifying theory of gravitational force and hopes are pinned on the location of the graviton - a hypothetical elementary particle that transmits the force of gravity. But the graviton is proving hard to find. Indeed, the Large Hadron Collider at CERN still won't allow us to detect gravitons per se, but might be able to prove their existence in other ways. The idea of the graviton particle first emerged in the middle of the 20th century, when the notion that particles as mediators of force was taken seriously. Physicists believed that it could be applicable to gravity and by the late 20th century the hunt was truly on for the ultimate theory, a theory of quantum gravity. So why is the search for the graviton the major goal of theoretical physics? How will the measurement of gravitation waves help prove its existence? And how might the graviton unite the seemingly incompatible theories of general relativity and quantum mechanics? With Roger Cashmore, Former Research Director at CERN and Principal of Brasenose College, Oxford; Jim Al-Khalili, Professor of Physics at the University of Surrey; Sheila Rowan, Reader in Physics in the Department of Physics and Astronomy at the University of Glasgow.

Melvyn Bragg and guests discuss the unique properties of asteroids. They used to be regarded as the 'vermin of the solar system', irritating rubble that got in the way of astronomers trying to study more interesting phenomena. It was difficult or even impossible for an observer of asteroids to book time using the world's best telescopes, because they were regarded as unspectacular objects that could tell us little about the origins of the universe. However, that has all changed. It is now thought that asteroids are the unused building blocks of planets, 'pristine material' that has remained chemically unchanged since the creation of the solar system; a snapshot of matter at the beginning of time. At the moment the Japanese probe Hayabusa is 180 million miles away, pinned to the back of the asteroid Itokawa, attempting to gain our first samples of the chemical composition of an asteroid. Why did asteroids fail to form planets? How do they differ from their celestial cousins, the comets? And are either of them likely to create another impact on planet Earth? With Monica Grady, Professor of Planetary and Space Sciences, Open University; Carolin Crawford, Royal Society Research Fellow, University of Cambridge; John Zarnecki, Professor of Space Science, Open University.

Melvyn Bragg and guests discuss the rise of the mammals. The Cenozoic Era of Earth's history began 65 million years ago and runs to this day. It began with the extraordinary 'KT event', a supposed asteroid impact that destroyed the dinosaurs, and incorporates the break up of Pangaea, the enormous landmass that eventually formed the continents we know today. It is known as the 'Age of the Mammals', and it is the period in which warm-blooded, lactating, often furry animals diversified rapidly and spread across the globe on land and in the sea. According to evolutionary theory, what conditions created the opportunity for mammals to thrive? What environmental factors lead to the characteristics they share - and the features they don't? And how did they become the most intelligent class of animals on the planet? With Richard Corfield, Senior Lecturer in Earth Sciences at the Open University; Steve Jones, Professor of Genetics at University College London; Jane Francis, Professor of Palaeoclimatology at the University of Leeds.

Melvyn Bragg and guests discuss the history of magnetism. Pliny the Elder, in his Historia Naturalis, tells a story of a legendary Greek shepherd called Magnes who, while guiding his flock on Mount Ida, suddenly found it hard to move his feet. The nails of his sandals held fast to the rock beneath them, and the iron tip of his crook was strangely attracted to the boulders all around. Magnes had stumbled across the lodestone, or 'Magnetite', and discovered the phenomenon of magnetism. Plato was baffled by this strange force, as were Aristotle and Galen, and despite being used in navigation, supposedly suspended over the body of Mohammed and deployed in the pursuit of medical cures. St Thomas Aquinas thought magnets had souls. it was not until the late 16th century that any serious scientific attempt was made to explain the mystifying powers of the magnet. Descartes developed a particle theory of magnetism but the great Isaac Newton fought shy of the problem of what caused magnets to attract and repelWho pioneered the study of magnetism? What theories did they construct from its curious abilities and how was the power of the magnet brought out of the realm of magic and into the service of science? With Stephen Pumfrey, Senior Lecturer in the History of Science at the University of Lancaster; John Heilbron, Emeritus Professor of History at the University of California, Berkeley; Lisa Jardine, Professor of Renaissance Studies at Queen Mary, University of London.

Melvyn Bragg and guests discuss the KT Boundary. Across the entire planet, where it hasn't been eroded or destroyed in land movements, there is a thin grey line. In Italy it is 1 cm thick, in America it stretches to three centimetres, but it is all the same thin grey line laid into the rock some 65 million years ago and it bears witness to a cataclysmic event experienced only once in Earth's history. It is called the KT Boundary and geologists believe it is the clue to the death of the dinosaurs and the ultimate reason why mammals and humans inherited the Earth.But exactly what did happen 65 million years ago? How was this extraordinary line created across the Earth and does it really hold the key to the death of the dinosaurs?With Simon Kelley, Head of Department in the Department of Earth Sciences, Open University, Jane Francis, Professor of Palaeoclimatology, University of Leeds; Mike Benton, Professor of Vertebrate Palaeontology in the Department of Earth Sciences, University of Bristol.

Melvyn Bragg and guests discuss Renaissance Mathematics. As with so many areas of European thought, mathematics in the Renaissance was a question of recovering and, if you were very lucky, improving upon Greek ideas. The geometry of Euclid, Appollonius and Ptolemy ruled the day. Yet within two hundred years, European mathematics went from being an art that would unmask the eternal shapes of geometry to a science that could track the manifold movements and changes of the real world. The Arabic tradition of Algebra was also assimilated. In its course it changed the way people understood numbers, movement, time, even nature itself and culminated in the calculus of Isaac Newton and Gottfried Leibniz. But how did this profound change come about? What were the ideas that drove it and is this the period in which mathematics became truly modern?With Robert Kaplan, co-founder of the Maths Circle at Harvard University; Jim Bennett, Director of the Museum of Science and Fellow of Linacre College, University of Oxford; Jackie Stedall, Research Fellow in the History of Mathematics, The Queen's College, Oxford.

Melvyn Bragg and guests discuss perception: how the brain reacts to the mass of data continually crowding it. Barry Stein's laboratory at Wake Forest University in the United States found that the shape of a right angle drawn on the hand of a chimpanzee starts the visual part of the brain working, even when the shape has not been seen. It has also been discovered that babies learn by touch before they can properly make sense of visual data, and that the senses of smell and taste chemically combine to give us flavour.Perception is a tangled web of processes and so much of what we see, hear and touch is determined by our own expectations that it raises the question of whether we ever truly perceive what others do.What governs our perception of the world? And are we correct to distinguish between sight, sound, smell, touch and taste when they appear to influence each other so very much?With Richard Gregory, Senior Research Fellow in the Department of Experimental Psychology, Bristol University; David Moore, Director of the Medical Research Council Institute of Hearing Research, University of Nottingham; Gemma Calvert, Reader in Cognitive Neuroscience, University of Bath.

Melvyn Bragg and guests discuss 'dark energy'. Only 5% of our universe is composed of visible matter, stars, planets and people; something called 'dark matter' makes up about 25% and an enormous 70% of the universe is pervaded with the mysteriously named 'dark energy'. It is a recent discovery and may be only a conjecture, but it has been invoked to explain an abiding riddle of the cosmos: if the expansion of the universe is powered by the energy of the Big Bang, then why isn't the expansion slowing down over time as the initial energy runs down and the attractive force of gravity asserts itself? Scientists had predicted a Big Crunch as the logical opposite of the Big Bang, but far from retracting, the expansion of the universe is actually accelerating...it's running away with itself.How do we know that the universe is behaving like this and what's causing it? If dark energy is the culprit, then what is this elusive, though omnipresent entity?With Sir Martin Rees, Astronomer Royal and Professor of Cosmology and Astrophysics, Cambridge University; Carolin Crawford, Royal Society University Research Fellow at the Institute of Astronomy, University of Cambridge; Sir Roger Penrose, Emeritus Rouse Ball Professor of Maths at Oxford University.

Melvyn Bragg and guests discuss the history of Alchemy, the ancient science of transformations. The most famous alchemical text is the Emerald Tablet, written around 500BC and attributed to the mythical Egyptian figure of Hermes Trismegistus. Among its twelve lines are the essential words - “as above, so below". They capture the essence of alchemy, that the heavens mirror the earth and that all things correspond to one another. Alchemy was taken up by some of the most extraordinary people in our intellectual development, including Roger Bacon, Paracelsus, the father of chemistry, Robert Boyle, and, most famously, Isaac Newton, who wrote more about alchemy than he did about physics. It is now contended that it was Newton’s studies into alchemy which gave him the fundamental insight into the famous three laws of motion and gravity.With Peter Forshaw, Lecturer in Renaissance Philosophies at Birkbeck, University of London, Lauren Kassell, Lecturer in the History and Philosophy of Science at the University of Cambridge, Stephen Pumfrey, Senior Lecturer in the History of Science at the University of Lancaster.

Melvyn Bragg and guests discuss the Cambrian period when there was an explosion of life on Earth. In the Selkirk Mountains of British Columbia in Canada, there is an outcrop of limestone shot through with a seam of fine dark shale. A sudden mudslide into shallow water some 550 million years ago means that a startling array of wonderful organisms has been preserved within it. Wide eyed creatures with tentacles below and spines on their backs, things like flattened rolls of carpet with a set of teeth at one end, squids with big lobster-like arms. There are thousands of them and they seem to testify to a time when evolution took a leap and life on this planet suddenly went from being small, simple and fairly rare to being large, complex, numerous and dizzyingly diverse. It happened in the Cambrian Period and it's known as the Cambrian Explosion.But if this is the great crucible of life on Earth, what could have caused it? How do the strange creatures relate to life as we see it now? And what does the Cambrian Explosion tell us about the nature of evolution?With Simon Conway Morris, Professor of Evolutionary Palaeobiology, Cambridge University; Richard Corfield, Visiting Senior Lecturer at the Centre for Earth, Planetary, Space and Astronomical Research, Open University; Jane Francis, Professor of Palaeoclimatology, University of Leeds.

Melvyn Bragg and guests discuss the mind/body problem in philosophy. At the start of René Descartes' Sixth Meditation he writes: "there is a great difference between mind and body, inasmuch as body is by nature always divisible, and mind is entirely indivisible. For when I consider the mind, or myself in so far as I am merely a thinking thing, I am unable to distinguish many parts within myself; I understand myself to be something quite single and complete. Although the whole mind seems to be united to the whole body, I recognize that if a foot or an arm or any other part of the body is cut off nothing has thereby been taken away from the mind".This thinking is the basis of what's known as 'Cartesian dualism', Descartes' attempt to address one of the central questions in philosophy, the mind/body problem: is the mind part of the body, or the body part of the mind? If they are distinct, then how do they interact? And which of the two is in charge?With Anthony Grayling, Reader in Philosophy at Birkbeck, University of London; Julian Baggini, editor of The Philosophers' Magazine; Sue James, Professor of Philosophy at Birkbeck, University of London.

Melvyn Bragg and guests discuss the Second Law of Thermodynamics which can be very simply stated like this: "Energy spontaneously tends to flow from being concentrated in one place to becoming diffused and spread out". It was first formulated – derived from ideas first put forward by Lord Kelvin - to explain how a steam engine worked, it can explain why a cup of tea goes cold if you don't drink it and how a pan of water can be heated to boil an egg.But its application has been found to be rather grander than this. The Second Law is now used to explain the big bang, the expansion of the cosmos and even suggests our inexorable passage through time towards the 'heat death' of the universe. It's been called the most fundamental law in all of science, and CP Snow in his Two Cultures wrote: "Not knowing the Second Law of Thermodynamics is like never having read a work of Shakespeare".What is the Second Law? What are its implications for time and energy in the universe, and does it tend to be refuted by the existence of life and the theory of evolution?With John Gribbin, Visiting Fellow in Astronomy at the University of Sussex; Peter Atkins, Professor of Chemistry at Oxford University; Monica Grady, Head of Petrology and Meteoritics at the Natural History Museum.

Melvyn Bragg and guests discuss the extraordinary mind of the psychiatrist Carl Gustav Jung. In 1907 Sigmund Freud met a young man and fell into a conversation that is reputed to have lasted for 13 hours. That man was the Swiss psychiatrist Carl Gustav Jung. Freud is celebrated as the great pioneer of the 20th century mind, but the idea that personality types can be 'introverted' or 'extroverted', that certain archetypal images and stories repeat themselves constantly across the collective history of mankind, and that personal individuation is the goal of life, all belong to Jung: "Your vision will become clear only when you look into your heart... Who looks outside, dreams. Who looks inside, awakens", he declared. And he also said "Show me a sane man and I will cure him for you".Who was Jung? What is the essence and influence of his thought? And how did he become such a controversial and, for many, such a beguiling figure?With Brett Kahr, Senior Clinical Research Fellow in Psychotherapy and Mental Health at the Centre for Child Mental Health in London and a practising Freudian; Ronald Hayman, writer and biographer of Jung; Andrew Samuels, Professor of Analytical Psychology at the University of Essex and a Jungian analyst in clinical practice.

Melvyn Bragg and guests discuss the Higgs Boson particle. One weekend in 1964 the Scottish scientist Peter Higgs was walking in the Cairngorm Mountains. On his return to his laboratory in Edinburgh the following Monday, he declared to his colleagues that he had just experienced his 'one big idea' and now had an answer to the mystery of how matter in the universe got its mass. That big idea took many years of refining, but it has now generated so much international interest and has such an important place in physics that well over one billion pounds is being spent in the hope that he was right. It's the biggest science project on Earth; the quest to find the 'Higgs Boson', a fundamental constituent of nature that - if it does exist - has such a central role in defining the universe that it's also known as the God Particle.What is the Higgs Boson? Why is it so important to scientists and how are they planning to find it?With Jim Al-Khalili, Senior Lecturer in Physics at the University of Surrey; David Wark, Professor of Experimental Physics at Imperial College London and the Rutherford Appleton Laboratory; Professor Roger Cashmore, former Research Director at CERN and now Principal of Brasenose College, Oxford.

Melvyn Bragg and guests discuss the dawn of the age of electricity. In Gulliver's Travels, published in 1726, Jonathan Swift satirised natural philosophers as trying to extract sunbeams from cucumbers. Perhaps he would have been surprised, or even horrified, by the sheer force of what these seemingly obscure experimentalists were about to unleash on society. Electricity soon reached into all areas of 18th century life, as Royal Society Fellows vied with showmen and charlatans to reveal its wonders to the world. It was, claimed one commentator, 'an entertainment for Angels rather than for Men'. Electricity also posed deep questions about the nature of life. For some it was the divine spark that animated all things, for others it represented a dangerous materialism that reduced humans to mere machines.But how did electricity develop in the 18th and 19th centuries? Why was it so politically contentious and how was it understood during the age in which it changed the world forever?With Simon Schaffer, Professor in History and Philosophy of Science at the University of Cambridge and a Fellow of Darwin College; Patricia Fara, historian of science and a Fellow of Clare College, Cambridge; Iwan Morus, Lecturer in the History of Science at Queen's University Belfast.

Melvyn Bragg and guests discuss the emergence of the world’s first organic matter nearly four billion years ago. Scientists have named 1.5 million species of living organism on the land, in the skies and in the oceans of planet Earth and a new one is classified every day.  Estimates of how many species remain to be discovered vary wildly, but science accepts one categorical point – all living matter on our planet, from the nematode to the elephant, from the bacterium to the blue whale, is derived from a single common ancestor. What was that ancestor?  Did it really emerge from a ‘primordial soup’? And what, in the explanation of evolutionary science, provided the catalyst to start turning the cycle of life?With Richard Dawkins, Charles Simonyi Professor of the Public Understanding of Science at Oxford University; Richard Corfield, Visiting Senior Lecturer at the Centre for Earth, Planetary, Space and Astronomical Research at the Open University; Linda Partridge, Biology and Biotechnology Research Council Professor at University College London.

Melvyn Bragg and guests discuss the history of the most detailed number in nature. In the Bible's description of Solomon's temple it comes out as three, Archimedes calculated it to the equivalent of 14 decimal places and today's super computers have defined it with an extraordinary degree of accuracy to its first 1.4 trillion digits. It is the longest number in nature and we only need its first 32 figures to calculate the size of the known universe within the accuracy of one proton. We are talking about Pi, 3.14159 etc, the number which describes the ratio of a circle's diameter to its circumference. How has something so commonplace in nature been such a challenge for maths? And what does the oddly ubiquitous nature of Pi tell us about the hidden complexities of our world? With Robert Kaplan, co-founder of the Maths Circle at Harvard University, Eleanor Robson, Lecturer in the Department of History and Philosophy of Science at Cambridge University; and Ian Stewart, Professor of Mathematics at the University of Warwick.

Melvyn Bragg and guests discuss Renaissance obsession with Magic. In 1461 one of the powerful Medici family’s many agents carried a mysterious manuscript into his master’s house in Florence. It purported to be the work of an ancient Egyptian priest-king and magician called Hermes Trismegistus. When Cosimo de Medici saw the new discovery, he ordered his translations of Plato to be stopped so that work could begin on the new discovery at once. Hermes promised secret knowledge to his initiates and claimed to have spoken with the spirits and turned base metal into gold. His ideas propelled natural magic into the mainstream of Renaissance intellectual thought, as scholars and magi vied to understand the ancient secrets that would bring statues to life and call the angels down from heaven.But why did magic appeal so strongly to the Renaissance mind? And how did the scholarly Magus, who became a feature of the period, manage to escape prosecution and relate his work to science and the Church?With Peter Forshaw, Lecturer in Renaissance Philosophies at Birkbeck, University of London; Valery Rees, Renaissance historian and a translator of Ficino’s letters; Jonathan Sawday, Professor of English Studies at the University of Strathclyde.

Melvyn Bragg and guests discuss our knowledge of the planets in both our and other solar systems. Tucked away in the outer Western Spiral arm of the Milky Way is a middle aged star, with nine, or possibly ten orbiting planets of hugely varying sizes. Roughly ninety-two million miles and third in line from that central star is our own planet Earth, in thrall to our Sun, just one of the several thousand million stars that make up the Galaxy.Ever since Galileo and Copernicus gave us a scientific model of our own solar system, we have assumed that somewhere amongst the myriad stars there must be other orbiting planets, but it took until 1995 to find one. ‘51 Pegasus A’ was discovered in the Pegasus constellation and was far bigger and far closer to its sun than any of our existing theories could have predicted. Since then 121 new planets have been found. And now it is thought there may be more planets in the skies than there are stars.What causes a planet to form? How do you track one down? And how likely is there to be another one out there with properties like the Earth’s?With Paul Murdin, Senior Fellow at the Institute of Astronomy in Cambridge; Hugh Jones, planet hunter and Reader in Astrophysics at Liverpool John Moores University; Carolin Crawford, Royal Society Research Fellow at the Institute of Astronomy in Cambridge.

Melvyn Bragg and guests discuss the history of the number between 1 and -1, which has strange and uniquely beguiling qualities. Shakespeare’s King Lear warned, “Nothing will come of nothing”. The poet and priest John Donne said from the pulpit, “The less anything is, the less we know it: how invisible, unintelligible a thing is nothing”, and the English monk and historian William of Malmesbury called them “dangerous Saracen magic”. They were all talking about zero, the number or symbol that had been part of the mathematics in the East for centuries but was finally taking hold in Europe.What was it about zero that so repulsed their intellects? How was zero invented? And what role does zero play in mathematics today?With Robert Kaplan, co-founder of the Maths Circle at Harvard University and author of The Nothing That Is: A Natural History of Zero; Ian Stewart, Professor of Mathematics at the University of Warwick; Lisa Jardine, Professor of Renaissance Studies at Queen Mary, University of London.

Melvyn Bragg and guests discuss a problematic notion which can be an emotional condition, a syndrome, an extreme or over-reaction, or the physical signs of trauma. The term ‘hysteria’ was first used in Greece in the 5th century BC by Hippocratic doctors. They were trying to explain an illness whose symptoms were breathing difficulties and a sense of suffocation, and whose sufferers were seen chiefly to be recently bereaved widows. The explanation was thought to be a wandering womb putting pressure on other organs. The use that Sigmund Freud put to the term was rather different, but although there is no wandering womb in his notion of hysteria, there is still a mysterious leap from the emotional to the physical, from the mind to the body. What is hysteria? How can emotional experiences cause physical illnesses? And has hysteria’s association with old stereotypes of femininity put it off the modern medical map? With Juliet Mitchell, Professor of Psychoanalysis and Gender Studies at the University of Cambridge and author of Mad Men and Medusas: Reclaiming Hysteria and the Effects of Sibling Relations on the Human Condition; Rachel Bowlby, Professor of English at the University of York who has written the introduction to the latest Penguin translation of Sigmund Freud and Joseph Breuer’s Studies in Hysteria; Brett Kahr, Senior Clinical Research Fellow in Psychotherapy and Mental Health at the Centre for Child Mental Health in London.

Melvyn Bragg and guests discuss the 30 year search to solve all the biggest questions in physics. At the end of the last century, brave voices were predicting that all the big questions of physics were on the verge of being answered by a Theory of Everything. The disparity between the physics of the very small would finally be reconciled with the very large, and the four forces of nature would finally be united with a single set of equations. It was suggested that with such a theory we might solve the riddle of black holes, unlock the secrets of the Big Bang, probe other universes and even uncover the mystery of travelling through time. But Stephen Hawking, who once said that with a Theory of Everything “we would know the mind of God”, has changed his mind and now says that it may not be possible after all. So what are the prospects for a Theory of Everything? Why do we need one? How do we get one? And what would it mean if we did? With Brian Greene, Professor of Physics and Mathematics at Columbia University and author of The Fabric of the Cosmos; John Barrow, Professor of Mathematical Sciences at the University of Cambridge and author of The Constants of Nature; Dr Val Gibson, particle physicist from the Cavendish Laboratory and Fellow of Trinity College, Cambridge.

Melvyn Bragg and guests discuss the interpretation of dreams. Over a hundred years ago, Sigmund Freud declared confidently, “The interpretation of dreams is the royal road to a knowledge of the unconscious activities of the mind”. He was writing in his famous volume, The Interpretation of Dreams and his ideas made a huge impact on the century that was to follow. However, despite the cultural influence of his work, there is still no agreement in neuroscience as to the function or mechanism of dreaming; this is partly because for much of the century the prevailing wisdom was that there was no meaning to dreams at all.What is the mental circuitry that creates our dreams? If they have no meaning, why do we dream them? And why is the tide turning with neuroscientists starting to find reasons to take dreams seriously again?With Professor V S Ramachandran, Director of the Center for Brain and Cognition at the University of California, San Diego; Mark Solms, Professor of Neuropsychology at the University of Cape Town; Martin Conway, Professor of Psychology at the University of Durham.

Melvyn Bragg and guests discuss Ernest Rutherford. He was the father of nuclear science, a great charismatic figure who mapped the landscape of the sub-atomic world. He identified the atom’s constituent parts, discovered that elemental decay was the cause of radiation and became the first true alchemist in the history of science when he forced platinum to change into gold. He was born at the edge of the Empire in 1871, the son of Scottish immigrant farmers and was working the fields when a telegram came from the great British physicist J J Thomson asking him to come to Cambridge. Rutherford immediately laid down his spade saying "that’s the last potato I ever dig". It was. He went on to found a science, win a Nobel Prize and pioneer the ‘big science’ of the twentieth century. With Simon Schaffer, Professor in the History and Philosophy of Science at the University of Cambridge; Jim Al–Khalili, Senior Lecturer in Physics at the University of Surrey; Patricia Fara, Fellow of Clare College, Cambridge.

Melvyn Bragg and guests discuss the origins and history of codes. In October 1586, in the forbidding hall of Fotheringhay Castle, Mary Queen of Scots was on trial for her life. Accused of treason and denied legal representation, she sat alone in the shadow of a vast and empty throne belonging to her absent cousin and arch rival Elizabeth I of England. Walsingham, Elizabeth’s Principal Secretary, had already arrested and executed Mary’s fellow conspirators, her only hope lay in the code she had used in all her letters concerning the plot. If her cipher remained unbroken she might yet be saved. Not for the first time the life of an individual and the course of history depended on the arcane art of Cryptography.What are the origins of this secretive science? And what links the ‘Caesar Cipher’ with the complex algorithms which underpin so much of our modern age?With Simon Singh, science writer and author of The Code Book: The Secret History of Codes and Code-Breaking; Professor Fred Piper, Director of the Information Security Group at Royal Holloway, University of London and co-author of Cryptography: A Very Short Introduction; Lisa Jardine, Professor of Renaissance Studies at Queen Mary, University of London and author of Ingenious Pursuits.

Melvyn Bragg discusses Jean-Baptiste Lamarck, the 18th century French scientist.Charles Darwin defined Natural Selection in On the Origin of Species, “Variations, however slight and from whatever cause proceeding, if they be in any degree profitable to the individuals of a species… will tend to the preservation of such individuals, and will generally be inherited by the offspring”. It was a simple idea that had instant recognition, “How extremely stupid not to have thought of that!” said T H Huxley. However, Darwin did not invent the idea of evolution and not everyone saw his ideas as original. The great geologist Charles Lyell repeatedly referred to “Lamarck’s theory as modified by Darwin”, Darwin complained to him, “I believe this way of putting the case is very injurious to its acceptance”. He desperately wanted to escape the shadow of this genuine scientific precursor and what has become known as the ‘Lamarckian Heresy’ has maintained a ghostly presence on the fringes of biology to this day.Who was Lamarck? How did Natural Selection escape from his shadow and gain acceptance from the scientific establishment? And has any evidence emerged that might challenge the elegant simplicity of Darwin’s big idea?With Sandy Knapp, Senior Botanist at the Natural History Museum, Steve Jones, Professor of Genetics in the Galton Laboratory at University College London and author of Almost Like a Whale: The Origin of Species Updated; Simon Conway Morris, Professor of Evolutionary Paleobiology at Cambridge University.

Melvyn Bragg and guests discuss the age of the Earth. It was once thought that the world began in 4004 BC. Lord Kelvin calculated the cooling temperature of a rock the size of our planet and came up with a figure of 20 million years for the age of the Earth. Now, the history of our planet is divided into four great Eons: the Hadean, the Archaen, the Proterozoic and the Phanerozoic. Together, they are taken to encompass an incredible four and a half billion years. How can we begin to make sense of such a huge swathe of time? And can we be sure that we have got the Earth's age right? Geologists use Eras, Periods and Epochs to further punctuate what's known as 'Deep Time', but can we be sure that the classifications we use don't obscure more than they reveal? With Richard Corfield, Research Associate in the Department of Earth Sciences at Oxford University; Hazel Rymer, Senior Lecturer in the Department of Earth Sciences at the Open University; Henry Gee, Senior Editor at Nature.

Melvyn Bragg and guests discuss the nature and existence of mathematical infinity. Jonathan Swift encapsulated the counter-intuitive character of infinity with insouciant style:“So, naturalists observe, a fleaHath smaller fleas on him that preyAnd these hath smaller fleas to bite ‘emAnd so proceed ad infinitum.”Alas, the developing utility mathematicians put to the idea of infinity did not find the English philosopher Thomas Hobbes quite so relaxed. When confronted with a diagram depicting an infinite solid whose volume was finite, he wrote, “To understand this for sense, it is not required that a man should be a geometrician or logician, but that he should be mad”. Yet philosophers and mathematicians have continued to grapple with the unending, and it is a core concept in modern maths.So, what is mathematical infinity? Are some infinities bigger than others? And does infinity exist in nature?With Ian Stewart, Professor of Mathematics at the University of Warwick; Robert Kaplan, co-founder of The Math Circle at Harvard University and author of The Art of the Infinite: Our Lost Language of Numbers; Sarah Rees, Reader in Pure Mathematics at the University of Newcastle.

Melvyn Bragg and guests discusses the life and ideas of James Clerk Maxwell whose work is not widely known, but whose genius and contribution to the age in which we live is enormous.He took the first colour photograph, defined the nature of gases and with a few mathematical equations expressed all the fundamental laws of light, electricity and magnetism - and in doing so he provided the tools to create the technological age, from radar to radio and televisions to mobile phones. He is credited with fundamentally changing our view of reality, so much so that Albert Einstein said, “One scientific epoch ended and another began with James Clerk Maxwell”. But who was James Clerk Maxwell? What were his ideas, and does this nineteenth century ‘natural philosopher’ deserve a place alongside Newton and Einstein in the pantheon of science? With Simon Schaffer, Reader in History and Philosophy of Science at the University of Cambridge; Peter Harman, Professor of the History of Science at Lancaster University and editor of The Scientific Letters and Papers of James Clerk Maxwell; Joanna Haigh, Professor of Atmospheric Physics at Imperial College London.

Melvyn Bragg and guests discuss the attempt to define humanity’s part in the natural world. In Childe Harold’s Pilgrimage Lord Byron wrote:“There is a pleasure in the pathless woods, There is a rapture on the lonely shore,There is society where none intrudes,By the deep Sea, and music in its roar:I love not man the less, but Nature more.” In the Bible’s book of Genesis, ‘nature’ was the paradise of Eden, but for the philosopher Thomas Hobbes it was a place of perpetual war, where the life of man was “solitary, poore, nasty, brutish and short”. The defining of Nature, whether “red in tooth and claw” or as the fount of all innocence, is an attempt to define man’s origins and purpose and humanity’s part in the natural world. With Jonathan Bate, Professor of English Literature at the University of Warwick; Roger Scruton, Professor of Philosophy at the University of Buckingham; Karen Edwards, Lecturer in English at the University of Exeter.

Melvyn Bragg and guests discuss the formation of volcanoes. In 79AD Mount Vesuvius erupted on the Bay of Naples, buried Pompeii in ash and drowned nearby Herculaneum in lava. The great letter writer Pliny the Younger was staying with his uncle in Misenum and was a witness to the cataclysm. He described it to the historian Tacitus, It seemed as though the sea was being sucked backwards, as if it were being pushed back by the shaking of the land. Certainly the shoreline moved outwards, and many sea creatures were left on dry sand. Behind us were frightening dark clouds, rent by lightning twisted and hurled, opening to reveal huge figures of flame. These were like lightning but bigger. This eruption, which claimed the life of Pliny's uncle, is one of about 500 volcanoes to have erupted in the last two thousand years, some of which are now categorised by vulcanologists as Plinian, after Pliny's famous description.What causes volcanoes? What role do they play in the formation and maintenance of our planet? And is it ever possible to predict when and where they are about to erupt?With Hilary Downes, Professor of Geochemistry at Birkbeck, University of London; Steve Self, Professor of Vulcanology at the Open University; Bill McGuire, Benfield Professor of Geophysical Hazards at University College London.

Melvyn Bragg and guests discuss the Lunar Society. In the late 18th century, with the ascendant British Empire centred on London, a small group of friends met at a house on the crossroads outside Birmingham and applied their minds to the problems of the age. Between them they managed to launch the Industrial Revolution, discover oxygen, harness the power of steam and pioneer the theory of evolution. They were the Lunar Society, a gathering of free and fertile minds centred on the remarkable quartet of Matthew Boulton, James Watt, Joseph Priestly and Erasmus Darwin. The potter Josiah Wedgwood, another member, summed up the ethos of this group when he said that they were ‘living in an age of miracles in which anything could be achieved’.But how did the Lunar Society operate? What was the blend of religious dissent, entrepreneurial spirit and intellectual adventure that proved so fertile and how did their discoveries permanently change the shape and character of this country?With Simon Schaffer, Reader in History and Philosophy of Science at the University of Cambridge; Jenny Uglow, Honorary Visiting Professor at the University of Warwick and author of The Lunar Men: The Friends who Made the Future; Peter Jones, Professor of French History at the University of Birmingham.

Melvyn Bragg and guests discuss the function and significance of memory. The great writer of remembrance, Marcel Proust, declared “We are able to find everything in our memory, which is like a dispensary or chemical laboratory in which chance steers our hand, sometimes to a soothing drug and sometimes to a dangerous poison”. The memory is vital to life and without it we could not be the people we are, but can it really contain the sum of all our experience? Is it a repository constantly mounting events waiting to be plucked to consciousness, or if not, then under what criteria are memories turfed out?With Martin Conway, Professor of Psychology at Durham University; Mike Kopelman, Professor of Neuropsychiatry at King's College London and St Thomas’ Hospital; Kim Graham, Senior Scientist at the Medical Research Council’s Cognition and Brain Sciences Unit.

Melvyn Bragg and guests discuss blood. For more than 1500 years popular imagination, western science and the Christian Church colluded in a belief that blood was the link between the human and the divine. The Greek physician, Galen, declared that it was blood that contained the force of life and linked the body to the soul, the Christian Church established The Eucharist – the taking of the body and blood of Christ. In our blood was our individuality, it was thought, our essence and our blood lines were special. Transfusion threatened all that and now itself is being questioned.Why is it that blood was used to define both man and messiah? And how has the tradition of blood in religious thought been affected by the progress of medicine?With Miri Rubin, Professor of European History at Queen Mary, University of London; Dr Anne Hardy, Reader in the History of Medicine at the Wellcome Trust Centre for the History of Medicine at University College London; Jonathan Sawday, Professor of English Studies at the University of Strathclyde.

Melvyn Bragg and guests discuss the life cycle of stars. In his poem Bright Star John Keats wrote, "Bright Star, would I were steadfast as thou art". For Keats the stars were symbols of eternity- they were beautiful and ordered and unchanging - but modern astronomy tells a very different story. Stars, like everything else in the universe, are subject to change. They are born among vast swirls of gas and dust and they die in the stunning explosions we call supernovae. They create black holes and neutron stars and, in the very beginning of the universe, they forged the elements from which all life is made. But how do stars keep burning for millions of years, why do they self-destruct with such ferocity and what will happen to the universe when they all go out?With Paul Murdin, Senior Fellow at the Institute of Astronomy, Cambridge; Janna Levin, Advanced Fellow in Theoretical Physics in the Department of Applied Mathematics & Theoretical Physics at the University of Cambridge; Phil Charles, Professor of Astronomy at Southampton University.

Melvyn Bragg and guests discuss meteorology. The Book of Genesis resounds with a terrible act of vengeance, carried out by an angry God seeking to punish his people. And the mechanism with which this is carried out - a catastrophic flood which wipes out evil on earth. In fact, many ancient civilisations believed extreme meteorological phenomena like thunder and lightning, hailstones and even meteors were acts of divine intervention. Running parallel with this belief, however, was also a desire to understand and explain the natural world through rational enquiry and observation. This complex relationship – between the natural world and divinity – has fascinated philosophers, artists and scientists alike from antiquity to our own time. Aristotle, for example, coined the phrase meteorology but to what extent did he link meteorological events to the cosmos and the Gods? How did the development of instrumentation during the Renaissance aid the prediction of weather events? Why did 18th century writers such as Keats feel that these scientific advances stripped the skies of its mystique and romance? And why does meteorology continue to fascinate and mystify to this day? With Vladimir Jankovic, Wellcome Research Lecturer at the Centre for the History of Science, Technology and Medicine at Manchester University;Richard Hamblyn, writer; Liba Taub, Director of the Whipple Museum of the History of Science at Cambridge University.

Melvyn Bragg and guests discuss the theories of a grand design in the universe. The late evolutionary biologist Stephen Jay Gould argued that if you re-ran the tape of evolutionary history, an entirely different set of creatures would emerge. Man would not exist because the multitude of random changes that resulted in us would never be repeated exactly the same way. Others disagree, arguing that there is a pattern that points to some kind of direction – even, perhaps, a design, a sense that some things are pre-ordained. Who were the original proponents of the idea of a grand design? Were they deliberately setting out to find a scientific theory that could sit alongside religious faith? On the other hand, can the concept of contingency – or the randomness of evolution - be compatible with a belief in God? With Simon Conway Morris, Professor of Evolutionary Palaeobiology at Cambridge University and author of The Crucible of Creation – the Burgess Shale and the Rise of Animals; Sandy Knapp, botanist at the Natural History Museum; John Brooke, Andreas Idreos Professor of Science and Religion at Oxford University.

Melvyn Bragg and guests discuss the calendar, which shapes the lives of millions of people. It is an invention that gives meaning to the passing of time and orders our daily existence. It links us to the arcane movements of the heavens and the natural rhythms of the earth. It is both deeply practical and profoundly sacred. But where does this strange and complex creation come from? Why does the week last seven days but the year twelve months? Who named these concepts and through them shaped our lives so absolutely? The answers involve Babylonian Astronomers and Hebrew Theologians, Roman Emperors and Catholic Popes. If the calendar is a house built on the shifting sands of time, it has had many architects. With Robert Poole, Reader in History at St Martin’s College Lancaster and author of Time’s Alteration, Calendar Reform in Early Modern England; Kristen Lippincott, Deputy Director of the National Maritime Museum in Greenwich; Peter Watson, Research Associate at the McDonald Institute for Archaeological Research at Cambridge University and author of A Terrible Beauty – A History of the People and Ideas that Shaped the Modern Mind.

Melvyn Bragg and guests discuss man and disease. The Book of Exodus makes clear that when God wants to strike humankind, he does so with plague and disease. For millennia epidemics were understood exactly that way - as acts of divine retribution, a force of nature that could devastate empires and annihilate great swathes of population at a stroke. From the bubonic plague to measles, from cholera to smallpox, epidemics have constantly reshaped our world, leaving destruction and huge social upheaval in their wake. Before advanced science, what defences did humankind have? How much did the ancient Greeks understand of the root causes of disease - or did they simply explain it as an imbalance of the four humours that governed the body? What were the social and political consequences of The Black Death of 14th century Europe which wiped out a third of the population? How did the scientific breakthroughs of the 19th century - and the discovery of germ theory - alter people's perception of disease? And is it possible to live in a disease free society? How have we understood these afflictions, how have we fought against them and is it a war we can ever win?With Dr Anne Hardy, Reader in the History of Medicine at the Wellcome Trust Centre at University College London; David Bradley, Professor of Tropical Hygiene at the London School of Hygiene and Tropical Medicine; Dr Chris Dye, epidemiologist with the World Health Organisation.

Melvyn Bragg investigates the creatives forces of the imagination. Immanuel Kant said, "Imagination is a blind but indispensable function of the soul without which we should have no knowledge whatever but of which we are scarcely even conscious". Imagination has been the companion of artists, scientists, leaders and visionaries but what exactly is it? When did human beings first develop an imagination and why? How does it relate to creativity and what evolutionary function does creativity have? And is it possible to know whether our brains’ capacity for imagination is still evolving? With Dr Susan Stuart, Lecturer in Philosophy of Mind at the University of Glasgow; Steven Mithen, Professor of Early Prehistory at the University of Reading; Semir Zeki, Professor of Neurobiology at the University of London and author of Inner Vision: An Exploration of Art and the Brain.

Melvyn Bragg and guests discuss the vexing issue of human nature. Some argue that we are born as blank slates and our natures are defined by upbringing, experience, culture and the ideas of our time. Others believe that human nature is innate and pre-destined, regardless of time and place. Is there really such a thing as human nature? And, if there is, can it be changed? Does the truth about human nature mean we should stop striving for progress, or should it give us cause for optimism? How important is the human race in the wider scheme of things? With Steven Pinker, Professor of Psychology and Director of the Centre of Cognitive Neuroscience, Massachusetts Institute of Technology; Janet Radcliffe Richards, Philosopher, Reader in Bioethics, University College London; John Gray, Professor of European Thought, London School of Economics.

Melvyn Bragg and guests discuss the origin of the concept and historical role of the scientist. The word "science" first appeared in the English language in 1340 and ever since its meaning has been in a state of flux. The notion of "the scientist" has had a similarly evolving history. For some, "the scientist" does not truly appear until after the Renaissance, others put its emergence much later than that. When did the words and concepts we recognise today take on their contemporary meaning? How has the role of the scientist, and our understanding of it, changed? Has science always been a rival to religion, or was it once an ally? And how has the scientist been perceived by the wider world – as a modern saint, the "priest of reason", or as a terrifying and amoral menace - the "mad scientist" of film and literature? With John Gribbin, Visiting Fellow in Astronomy, University of Sussex; Patricia Fara, Lecturer on the History and Philosophy of Science, Cambridge University; Hugh Pennington, Head of the Department of Medical Microbiology, University of Aberdeen.

Melvyn Bragg and guests discuss the impact of politics on psychoanalysis. The 20th century saw the birth and rise of psychoanalysis. Sigmund Freud led people to think about how the mind functioned and how our behaviour might be understood through the process of working with a psychoanalyst, either one-to-one or in a group. Freud thought a lot about this process and in 1922 he published Group Psychology and the Analysis of the Ego, in which he pronounced that the group "wants to be ruled and oppressed and to fear its masters." He was writing at a time when ideas about rules and oppression were much discussed because the 20th century was also a century of fascism, totalitarianism and dictatorship. Freud died in 1939, just as a wave of despotism was sweeping across Europe. To what extent does psychoanalysis function by the rules of a dictatorship and to what extent does it function like a democracy? Is there a part of us that craves dictatorship and, if so, why? Is there a war going on in our own minds between ideas that we allow in to our consciousness and other ideas that we repress? With Adam Phillips, general editor of the new Penguin translations of Freud; Sally Alexander, Professor of History, Goldsmiths College, University of London; Malcolm Bowie, Marshal Foch Professor of French Literature and Fellow, All Souls College, Oxford.

Melvyn Bragg and guests discuss the history of drugs. Throughout history people have taken them to alter their perceptions and change their moods. The attractions lie in the promise of instant pleasure and the possibility of heightened perceptions. Nietzsche said that no art could exist without intoxication and believed that a dream-like state was an essential precondition to superior vision and understanding. But artists and writers from De Quincey to Coleridge to Huxley have found drugs to be both a creative and a destructive force in their lives and work. Coleridge said in his poem about opium: Fantastic Passions! Maddening Brawl! And shame and terror over all! The world of drugs is a topsy-turvy world of ambivalence and paradox: a world of clarity and confusion; stimulation and stupefaction; medicine and poison; vitality and death.Can drugs really stimulate creativity? What is the impact of drugs on the body? And what role have narcotics and stimulants played in the history of medicine? With Richard Davenport-Hines, historian and author of The Pursuit of Oblivion: A Global History of Narcotics; Sadie Plant, author of Writing on Drugs; Mike Jay, historian and author of Emperors of Dreams, Drugs in the Nineteenth Century.

Melvyn Bragg examines whether world is a fundamentally chaotic or orderly place. When Newton published his Principia Mathematica in 1687 his work was founded on one simple message: Nature has laws and we can find them. His explanation of the movements of the planets, and of gravity, was rooted in the principle that the universe functions like a machine and its patterns are predictable. Newton’s equations not only explained why night follows day but, importantly, predicted that night would continue to follow day for evermore. Three hundred years later Newton’s principles were thrown into question by a dread word that represented the antithesis of his vision of order: that word was Chaos. According to Chaos Theory, the world is far more complicated than was previously thought. Instead of the future of the universe being irredeemably fixed, we are, in fact, subject to the whims of random unpredictability. Tiny actions can change the world by setting off an infinite chain of reactions: famously, if a butterfly flaps its wings in Brazil - it could cause a tornado in Berlin. So what’s the answer? Is the universe chaotic or orderly? If it’s all so complicated, why does night still follow day? And what is going on in that most complex machine of all - the brain - to filter and construct our perception of the world? With Susan Greenfield, Senior Research Fellow, Lincoln College, Oxford University; David Papineau, Professor of the Philosophy of Science, Kings College, London; Neil Johnson,University Lecturer in Physics at Oxford University.

Melvyn Bragg examines the physics of reality. When Quantum Mechanics was developed in the early 20th century reality changed forever. In the quantum world particles could be in two places at once, they disappeared for no reason and reappeared in unpredictable locations, they even acted differently according to whether we were watching them. It was so shocking that Erwin Schrodinger, one of the founders of Quantum Theory, said "I don’t like it and I'm sorry I ever had anything to do with it." He even developed an experiment with a cat to show how absurd it was. Quantum Theory was absurd, it disagreed with the classical physics of Newton and Einstein and it clashed with our experience of the everyday world. Footballs do not disappear without reason, cats do not split into two and shoes do not act differently when we are not looking at them. Or do they? Eighty years later we are still debating whether the absurd might actually be true. But why are features of quantum physics not seen in our experience of everyday reality? Can the classical and quantum worlds be reconciled, and why should reality make sense to us? With Roger Penrose, Emeritus Rouse Ball Professor of Mathematics, Oxford University; Fay Dowker, Lecturer in Theoretical Physics, Queen Mary, University of London; Tony Sudbery, Professor of Mathematics, University of York.

Melvyn Bragg examines Extra Terrestrials. New planets have been observed far beyond our solar system and telescopes are being built that will enable us to look for water and oxygen on these distant planets. If water and oxygen are present, there is every reason to suppose that some form of life might also exist there. It has even been suggested that we might find life within our own solar system. One of Jupiter’s moons, Europa, appears to be covered in an ice-crusted ocean and there is evidence that water once flowed on Mars. On our own planet, there are forms of life that don’t need the sun, living instead on energy from volcanic vents on the ocean floor. This discovery has changed our concept of what life needs in order to survive. Could life only exist on another planet like ours and what are our chances of ever discovering such a planet? If we find life, will it be intelligent, or little more than green slime? And if intelligent aliens exist, why aren’t they here? With Simon Goodwin, Researcher in Astronomy, Cardiff University; Heather Couper Space expert; Ian Stewart, Professor of Mathematics, Warwick University.

Melvyn Bragg examines the history of mankind's quest to understand the human body. The Greeks thought we were built like pigs, and when Renaissance man first cut his sacred flesh it was an act of heresey. We trace the noble ambitions of medical science to the murky underworld of Victorian grave robbing, we trace 2000 years of anatomical study. From the great showman Vesalius, enthralling the Renaissance Artists in the operating theatres of Italy to the sad and gruesome pursuits of Burke and Hare, Anatomy is mankind's often frustrated attempt to understand the body of man. What role has science, religion and art played in the quest to understand the male and the female body?With Harold Ellis, Clinical Anatomist, School of Biomedical Sciences, King's College, London; Ruth Richardson, Historian, and author of Death, Dissection and the Destitute, Phoenix Press; Andrew Cunningham, Wellcome Trust Senior Research Fellow in the History of Medicine, Department of History and Philosophy of Science, Cambridge University.

Melvyn Bragg and guests discuss the shape of the universe. In the Beginning, runs one account, was the Big Bang. All matter in existence today originated around 13 billion years ago in a phenomenally hot, extraordinarily condensed primordial atom that exploded with incredible force. Hydrogen and helium were shot across the firmament, gravity caused the gases to condense into clouds and in these clouds the first stars were formed, then galaxies came and more galaxies in clusters, onwards and outwards, ever expanding. It is still expanding, runs the orthodox account, and may even be speeding up. It is still creating new galaxies and it continues to colonise more and more of infinite space, despite the fact that it is supposedly infinite itself.So, if our universe is expanding, what is it expanding into? If it is already infinite how can it be getting any bigger? And is there really only one?With Sir Martin Rees, Royal Society Research Professor in Astronomy and Physics, Cambridge University; Julian Barbour, Independent Theoretical Physicist; Janna Levin, Advanced Fellow in Theoretical Physics at the University of Cambridge.

Melvyn Bragg examines one of the greatest scientific breakthroughs of the 20th century, and certainly the most controversial; the development of nuclear physics. Harnessing the enigmatic qualities of the atom’s tiny core brought us nuclear power and gave us The Bomb, a breakthrough with such far-reaching consequences that it moved the physicist Albert Einstein to say, “Had I known, I should have become a watch maker”.How can such outlandish power be released from such infinitesimal amounts of matter and what does the science of the nucleus tell us about how our universe is built? Nuclear technology provokes strong emotional and political reactions, but what are the plain facts behind its development as a science? With Jim Al-Khalili, Senior Lecturer in Physics at the University of Surrey; Christine Sutton, Particle Physicist and Lecturer in Physics at St Catherine’s College Oxford; John Gribbin, Visiting Fellow in Astronomy at the University of Sussex.

Melvyn Bragg looks at the development of the science of genetics. In the 1850s and 60s, in a monastery garden in Burno in Moravia, a Franciscan monk was cultivating peas. He began separating the wrinkly peas from the shiny peas and studying which characteristics were passed on when the next crop of peas were grown. In this slow and systematic way Gregor Mendel worked out the basic law of heredity and stumbled upon what was later to be described as the fundamental unit of life itself…the gene.But Mendel’s work was ignored when he published his findings in 1865, and it was not until the 20th century that he was rediscovered and the science of genetics was born. What effect did the discovery of the gene have on Darwin’s ideas? How do our genes work upon us, and how can we manipulate them?With Steve Jones, Professor of Genetics and Head of the Galton Laboratory at University College London, Richard Dawkins, Charles Simonyi Professor of the Public Understanding of Science at Oxford University and the genetic scientist Linda Partridge, NERC Research Professor at the Galton Laboratory, University College London.

Melvyn Bragg and guests discuss the science of Oceanography. In 1870 Jules Verne described the deep ocean in 2,000 Leagues Under the Sea. He wrote: “The sea is an immense desert where man is never alone for he feels life, quivering around him on every side.” This was actually closer to the truth than the science of the time, when ‘Azoic Theory’ held sway and it was believed that nothing could exist below 600 metres. Now we estimate that there are more species in the deep ocean than in the rest of the planet put together, somewhere between 2 million and 100 million different species of organism are living on the ocean floor.Science has dispelled the idea that huge underground tunnels join our oceans together and the notion that giant Kraken lurk in the deep, but our seas still retain much of their mystery and there have been more men on the surface of the moon than at the bottom of the ocean. How should we understand the sea? With Margaret Deacon, visiting Research Fellow at Southampton Oceanography Centre and author of Scientists and the Sea, Tony Rice, Biological Oceanographer and author of Deep Ocean, Simon Schaffer, Reader in History and Philosophy of Science at the University of Cambridge, and a fellow of Darwin College.

Melvyn Bragg discusses the origin of the Earth. Ideas used to be very clear about its origins. Bishop Ussher, in 1654 arrived at an exact figure and specified it in his work Annalis Veteris et Novi Testamenti: He deduced that work on Planet Earth began at exactly 9am, on Monday 23rd October 4004 BC. The date was then printed in the margin of The Bible and preached from the pulpit, and right up to the nineteenth century to the left of ‘In The Beginning…’ was specified ‘Before Christ 4004’.Christian believers thought the creation story was solid as a rock…until the geologists arrived. First Hutton, then Smith, and then Lyell smashing away at orthodox belief in a way that made poor Ruskin quail, but in doing so they created a science. With Simon Winchester, author of The Map That Changed the World: the Tale of William Smith and the Birth of A Science; Cherry Lewis, geologist and author of The Dating Game: One Man’s Search for the Age of the Earth; John Cosgrove, Structural Geologist from the Royal School of Mines at Imperial College, London.

Melvyn Bragg and guests discuss Black Holes. They are the dead collapsed ghosts of massive stars and they have an irresistible pull: their dark swirling, whirling, ever-hungry mass has fascinated thinkers as diverse as Edgar Allen Poe, Stephen Hawking and countless science fiction writers. When their ominous existence was first predicted by the Reverend John Mitchell in a paper to the Royal Society in 1783, nobody really knew what to make of the idea - they couldn’t be seen by any telescope. Although they were suggested by the eighteenth century Marquis de Laplace and their existence was proved on paper by the equations of Einstein’s General Theory of Relativity, it was not until 1970 that Cygnus X 1, the first black hole, was put on the astral map. What causes Black Holes? Do they play a role in the formation of galaxies and what have we learnt of their nature since we have found out where they are?With the Astronomer Royal - 2001 Sir Martin Rees, Professor of Physics and Astronomy at Cambridge University; Jocelyn Bell Burnell, Professor of Physics at The Open University; Professor Martin Ward, director of the X-Ray Astronomy Group at the University of Leicester.

Melvyn Bragg and guests discuss the significance of fossils. In the middle of the nineteenth century the discoveries of the fossil hunters used to worry poor Ruskin to death, he wrote in a letter in 1851, “my faith, which was never strong, is being beaten to gold leaf…If only those Geologists would let me alone I could do very well, but those dreadful Hammers! I hear the clink of them at the end of every cadence of the Bible verses.”The testimony of fossils over the ages has been remarkably eloquent when we have wanted to listen; and now with mass spectrometers, electron microscopes and secondary X-ray detectors, these long dead organisms can speak to us of the past in ways they never could before.With Richard Corfield, Research Associate in the Department of Earth Sciences at Oxford University; Dianne Edwards, Distinguished Research Professor in Palaeobotany at Cardiff University; Richard Fortey, Senior Research Palaeontologist at the Natural History Museum.

Melvyn Bragg examines Quantum Gravity. Early in the 20th century physicists were startled by the realisation that the smallest things in the universe do not obey Newton’s laws of gravity. Ripe apples fall from trees, billiard balls roll mostly on the table and the moon orbits the Earth in thrall to its gravitational pull, but there is no such force of gravity at work in the world of very small things. It seems there is one set of rules for the realm of every day objects, and a very different set of laws for the quantum world - where tiny particles actually form the building blocks of all those larger things.But how can this be? It doesn’t appear to make sense. Physicists decided that there must be another theory - a much larger theory - that unites, incorporates and finally makes sense of these divided realms. And this has been the Holy Grail of physics ever since. With Dr John Gribbin, Visiting Fellow in Astronomy, University of Sussex; Lee Smolin, Professor of Physics, Centre for Gravitational Physics and Geometry, Pennsylvania State University and Visiting Professor of Physics at Imperial College, London; Dr Janna Levin, Advanced Fellow, Department of Applied Mathematics and Theoretical Physics, Cambridge University.

Melvyn Bragg and guests discuss what drove the British Empire, especially in Victoria’s century. Was it science, more specifically, the science of plants, of agriculture, a scientific notion of nature and the improvement of nature? Was this seemingly rather adjacent notion - that the source of Empire can be found in Kew Gardens, Royal, Botanical, rather than in the muzzle of a gun or in the purse of a plunderer or in the consciousness of a conqueror - was science “the force that was with us?” Francis Bacon said of the Irish in 1603, “We shall reclaim them from their barbarous manners…populate plant and make civil all the provinces of that kingdom ..as we are persuaded that it is one of the chief causes for which God hath brought us to the Imperial Crown of these Kingdoms”. Centuries later, at the height of the Empire, John Stuart Mill wrote in On Liberty: “Despotism is a legitimate mode of government in dealing with barbarians, provided the end be their improvement”. But - despotism aside - was this notion of ‘improvement’ really the driving force behind the Empire? And did the British Empire have any firm basis in believing that the ‘light of pure reason’ that it brought to its colonies was any brighter than the knowledge that existed before they came? With Richard Drayton, Professor of History at the University of Virginia and author of Nature’s Government: Science, Imperial Britain and the ‘Improvement’ of the World; Maria Misra, Lecturer in Modern History and fellow of Keble College Oxford; Ziauddin Sardar, Professor of Science and Technology Policy, Middlesex University.

Melvyn Bragg looks at the deep claims made for mathematics, the discipline some believe to be the soul and true key to the understanding of all life, from the petals on the sunflower to the pulse in our wrists. The notion that mathematics is akin to theology might take some taking in at first. But from the first, in the West, they were. To Pythagoras, numbers were mystical and “prove” God. To Plato, who, it is claimed, has driven mathematics for over two thousand years, the ideals beyond the reality of our lives are to be found in mathematical perfections, immutable truth, God again in numbers. Are mathematics there in the universe, waiting to be discovered as the great ocean lying before Newton - or are they constructs applied by us to the universe and imposed rather than uncovered? It’s a long way from chalky sums on the blackboard and the first careless swing of the compass. Galilei Galileo wrote, “The Universe cannot be read until we have learnt the language and become familiar with the characters in which it was written. It is written in mathematical language, and the letters are triangles, circles and other geometrical figures, without which means it is humanly impossible to comprehend a single word”. But is he right that mathematics is the script in which the universe was written, or is it really just one of many possible systems that humankind has invented to interpret our world? Is mathematics is a process of invention or a voyage of discovery?With Ian Stewart, Professor of Mathematics and Gresham Professor of Geometry, University of Warwick; Margaret Wertheim, science writer, journalist and author of Pythagoras’ Trousers; John D Barrow, Professor of Applied Mathematics and Theoretical Physics, University of Cambridge.

Melvyn Bragg and guests discuss role of Freudian analysis in understanding the great works of literature. Freud said, “The poets and philosophers before me discovered the unconscious. What I discovered was the scientific method by which the unconscious can be studied”. Psychoanalysis has always been more than a ‘talking cure’ and it has strong ties to literature, but one hundred years after the publication of the first great work of psychoanalysis, The Interpretation of Dreams, critics are putting the scientific basis of Freud’s work in grave doubt and he is in danger of being pitched in with poets. The great American critic Harold Bloom has said “Freud, the writer will survive the death of psychoanalysis”, and the analyst and writer Adam Phillips seems to go further in his new book Promises Promises where he writes, “I think of Freud as a romantic writer, and I read psychoanalysis as poetry, so I don’t have to worry whether it is true or even useful”.So what is the relationship of psychoanalysis to literature, and if it is to be reclassified as literature itself can it still be practised as a talking cure?With Adam Phillips, author of Promises Promises: Essays on Psychoanalysis and Literature; Malcolm Bowie, Marshal Foch Professor of French Literature, Oxford University; Lisa Appignanesi novelist and co-author of Freud’s Women.

Melvyn Bragg and guests discuss Evolutionary Psychology. Richard Dawkins redefined human nature in 1976, when he wrote in The Selfish Gene: “They swarm in huge colonies, safe inside giant lumbering robots, sealed off from the outside world, communicating with it by tortuous indirect routes, manipulating it by remote control. They are in you and me; they created us body and mind; and their preservation is the ultimate rational of our existence…they go by the name of genes and we are their survival machines”. Potent ideas like this have given birth to a new discipline, ‘Evolutionary Psychology’: It claims that all of human behaviour can be understood in terms of a single compulsion - we must sexually reproduce so that our genes will live on. How has this idea developed, what can it tell us of how we behave, and can it be trusted? With Janet Radcliffe Richards, Reader in Bioethics, University College, London; Nicholas Humphrey, Professor of Psychology, New School for Social Research, New York; Professor Steven Rose, Professor of Physic, Open University.

Melvyn Bragg and guests discuss the Laws of Nature. Since ancient times philosophers and physicists have tried to discover simple underlying principles that control the Universe: In the 6th Century BC Thales declared “Everything is water”, centuries later Aristotle claimed that all of creation was forged from four elements, Newton more successfully laid down the Law of Universal Gravitation and as we speak, contemporary scientists are struggling to complete the task of ‘String Theory’ - the quest to find a single over-arching equation that unites all of physics, and can perhaps explain the organisation of everything in existence.But are the Laws of Physics really ‘facts of life’? Is what is true in physics, true in all areas of existence? Is it even true in other areas of physics?With Mark Buchanan, physicist and author of Ubiquity; Professor Frank Close, theoretical physicist and author of Lucifer’s Legacy: The Meaning of Asymmetry; Nancy Cartwright, Professor of Philosophy, LSE.

Melvyn Bragg and guests discuss the question of consciousness, our sense of self, and how we are able to imagine things when they are not there, which are problems that have troubled the great minds of philosophy for thousands of years. Consciousness has been linked to language, has been married to the mind and divorced from the body; it has been denied to animals, opposed to the subconscious and declared irreducible, but still it defies definition, and the debate rages on as to why we evolved it at all. But perhaps science will finally provide the answer. With Professor Gerald Edelman, Director of the Neurosciences, Institute in California and winner of the Nobel Prize for Physiology or Medicine in 1972; Igor Aleksander is Professor of Neural Engineering Systems, Imperial College, London; Margaret Boden, Professor of Philosophy and Psychology, University of Sussex.

Melvyn Bragg and guests discuss the chemical elements. The aim and challenge in chemistry, according to the Encyclopaedia Britannica, is the understanding of the complex materials which constitute everything in existence since the Big Bang, when the whole universe emerged out of the two elements of hydrogen and helium. For Aristotle there were four elements: Earth, Air, Fire and Water. Now there are one hundred and eight, sixteen of which are produced artificially, and none of which figure in Aristotle's original four. But they are all still elements - defined as substances which cannot be broken down, the building blocks of all life.Today we have the key to understanding these elements, the Periodic Table, which is a pattern embedded in nature and was miraculously discovered in a dream. With Paul Strathern, former lecturer in philosophy and science, Kingston University and author of Mendeleyev's Dream: The Quest for the Elements; Dr Mary Archer, Visiting Professor of Chemistry at Imperial College, London; John Murrell, Emeritus Professor of Chemistry, University of Sussex.

Melvyn Bragg and guests discuss the evolution of the human species. Where did we come from - we being Homo Sapiens? Let’s not go back to the Big Bang or in search of Genesis, but sift through the evidence from biology, palaeontology, climatology and anthropology.The story of human evolution is one that stretches back over five million years, and during that time there are reckoned to have been between fifteen and twenty species of hominid to have walked this planet. From the earliest (Genus) Australopithecus (Species) Anamensis through times when there have been several divergent pre-human species existing at once, we have now arrived at a period unique in the history of the earth when a sole human species, Homo Sapiens, is in evidence right across the globe.With Leslie Aiello, Professor of Biological Anthropology, University College, London; Robert Foley, evolutionary ecologist, writer and lecturer in biological anthropology at Cambridge University; Mark Roberts, Field Archaeologist, Project Leader of Boxgrove excavation and the discoverer of ‘Boxgrove Man’.

Melvyn Bragg examines the science of taxonomy. The Argentinean author Jose Luis Borges illustrated the problematic nature of scientific classification when he quoted from an ancient Chinese Encyclopaedia, the Celestial Emporium of Benevolent Knowledge. On these remote pages, in a complete absence of Phylum, Genus and Species, animals are divided into: “(a) those that belong to the Emperor, (b) embalmed ones, (c) those that are trained, (d) suckling pigs” and “those that tremble as if they were mad” ending with “those drawn with a very fine camel's hair brush”, “others”, “those that have just broken the flower vase” and “those that at a distance resemble flies.”Perhaps our own system of classifying the natural world might seem just as fantastical to a more knowing mind, and perhaps underlying the Linnaean system that homo sapiens currently finds useful there are prejudices of our own which distort the scientific truth. How does natural history classify the ‘natural order’?With Colin Tudge, writer, scientist and author of The Variety of Life: A Survey and a Celebration of all the Creatures that Have Ever Lived; Dr Sandy Knapp, Research Botanist, Department of Botany, Natural History Museum, London; Henry Gee, Senior Editor of Nature and author of Deep Time: Cladistics, the Revolution in Evolution.

Melvyn Bragg examines 20th century physics’ quest for the ultimate theory of everything. Einstein left us with his theory of General Relativity, which explained how gravity works on the scale of stars, galaxies, and the universe itself and Schroedinger left us with the equation that explained the mechanics of the tiny quantum realm. Both theories work to wonderful effect in their own worlds, but (and this is the sticking point) gravity is strangely absent from the quantum realm and planets behave nothing like particles. The enigma for scientists throughout most of the last century is that, as they are currently formulated, general relativity and quantum mechanics cannot both be right. The history of twentieth century physics has been a struggle to find a way to unite them, to find what has become the holy grail of modern physics: The Grand Unified Theory. With Brian Greene, Professor of Physics and Mathematics, Columbia University and Cornell University; Sir Martin Rees, Astronomer Royal and Royal Society Research Professor in Astronomy and Physics at Cambridge University.

Melvyn Bragg and guests discuss Johann Wolfgang von Goethe, the great poet and dramatist, famous for Faust, for The Sorrows of Young Werther, for Storm und Drang and for being a colossus in German literature. Born in the middle of the eighteenth century he lived through the first third of the nineteenth. He wrote lyric and epic verse, literary criticism, prose fiction, translations from 28 languages, he was a politician as well and was hailed by Napoleon as the boundless measure of man; but for much of his time, often to the exclusion of everything else, Goethe was a scientist. That was also part of this late flowering Renaissance man. Some say he paved the way for Darwin, some say he pre-dated the chaos theory, that he foreshadowed Gaia. In an age of romantic giants he was certainly a titan. He gave us the term morphology and sometimes he is even credited with inventing biology itself. How important were Goethe’s discoveries, and where does he really stand in the history of science? With Nicholas Boyle, Reader in German Literary and Intellectual History, Magdalene College, Cambridge, and biographer of Goethe; Simon Schaffer, Reader in the History and Philosophy of Science, Cambridge University and Fellow of Darwin College, Cambridge.

Melvyn Bragg discusses the social and economic consequences of the information revolution. There are now more than 200 million people connected to the internet world-wide. The world’s biggest ever merger has just seen Time Warner united with the internet service provider America Online, and in the United States alone it is predicted that transactions conducted in cyberspace will account for 327 billion dollars worth of business by 2002. Should we be pleased? Is it the ‘third wave’ as Dr Toffler predicted in 1980 - after the first wave, the agricultural revolution about 8000 BC and then the second, the Industrial Revolution three centuries ago.Is this change going to alter our society radically, empowering the individual and offering greater choice, or will information technology lead us into a dark age for society that destroys democracy, the work-place and family life? With Charles Leadbeater, Demos Research Associate and author of Living On Thin Air: The New Economy; Ian Angell, Professor of Information Systems, London School of Economics and author of The New Barbarian Manifesto: How to Survive the Information Age.

Melvyn Bragg discusses climate change. In 1999 the weather gave the planet’s occupants a terrible beating: 16,000 people lost their lives as a result of storms. Some 15 million people were left homeless and 10,000 died when the world’s worst cyclone swept across eastern India. Hurricane Floyd wreaked 4.3 billion pounds worth of damage in the United States, Typhoon Bart hit Japan and Typhoon York hit Hong Kong and Macau. Western Europe is unused to hurricane force winds, but since Christmas 80 people have died in France as a result of storms. And in Venezuela floods and mud slides are continuing to cause devastation on a massive scale.The climate has become political but is the science, supposedly underpinning apocalyptic and apposite millennial claims of doom, really water-tight? It might seem that the effects of global warming are already upon us, but are they - and if so how can we really hope to stop them? With Sir John Houghton, Co-Chair of the Inter-Governmental Panel on Climate Change - the United Nations’ global warming science committee; George Monbiot, environmentalist, journalist and Visiting Professor, Department of Philosophy, Bristol University.

Melvyn Bragg and guests discuss the history of mankind’s attempt to understand the nature of time. At the end of the 19th century, H.G.Wells imagined travelling through time in The Time Machine; “The palpitation of night and day merged into one continuous greyness; the sky took on a wonderful deepness of blue, a splendid luminous colour like that of early twilight; the jerking sun became a streak of fire, a brilliant arch in space”. When he was writing we thought time was unbending and universal and counted out by Newton’s clock. A hundred years later we have had Einstein and relativity, quantum theory, and atomic clocks, but in the third millennium, is mankind any closer to understanding what time really is? What, in short, do we know about time itself? A Greek philosopher thought that time was a figment of the imagination and there are contemporary physicists who go a long way to agreeing with him. Newton’s views on time were bent by Einstein. The ancient skills of astronomy once ruled the known world and skill in time usage could be said to be enthroned as a master craft in our day. “But at my back I always hear time’s winged chariot hurrying near and yonder all before us lie deserts of vast eternity” - Marvel wrote that of love, but it could be our epigraph for time. With Dr Neil Johnson, theoretical physicist at the Clarendon Laboratory, Oxford University and Royal Institution Christmas Lecturer 1999 on the subject of Time; Lee Smolin, cosmologist and Professor of Physics, Pennsylvania State University.

Melvyn Bragg examines the technological advances and ethics of modern medicine. On an average working day about three quarters of a million of us go to the doctor’s. About a hundred thousand are visited by nurses and other health professionals. Then there are the three hundred thousand that go to the dentist. Health is a central preoccupation. It is also big business, saving life, lengthening life and even promising a stab at eternal life. Yet while some technology is Space Age, the morality is often not far away from the Stone Age. Who decides who lives or dies? Insurance firms, for instance, want genetic information - should they have it? Stem cell research - hailed by many as an extraordinary advance - now runs into conflict with those who do not want the human embryo to be, as they see it, abused. In the 16th century Francis Bacon told us in his Advancement of Learning “Medicine is a science which hath been more professed than laboured, and yet more laboured than advanced: the labour having been, in my judgement, rather in a circle than in a progression”. Well, after a century that has brought us penicillin, the discovery of DNA, heart transplants and key-hole surgery, have we finally escaped the loop? Or does our ethical application of what we can technologically achieve mean we are marching in Bacon’s circle still? With Barry Jackson, consultant surgeon and President of the Royal College of Surgeons of England; Professor Sheila McLean, Director of the Institute of Law and Ethics in Medicine, Glasgow University.

Melvyn Bragg and guests discuss the problems of consciousness, one of the greatest mysteries facing science and philosophy today. The frustrations, the stubborn facts and the curiosities of today’s thinkers, philosophers, physicists and psychologists, demonstrate the elusiveness, and the utter impenetrability of consciousness. Can we explain our perception of colour, smell or what it is like to be in love in purely physical terms? Can memory, conviction and reason be explained primarily in terms of neural firing sequences in the brain? Three centuries ago Descartes famously believed that the problem was best solved by being ignored. Was he right? Could it be that the human mind is just not built to understand its own basis?With Ted Honderich, philosopher and former Grote Professor of the Philosophy of Mind and Logic, University College, London; Sir Roger Penrose eminent physicist, mathematician and author of The Large, The Small, and the Human Mind.

Melvyn Bragg and guests discuss the theory of Genetic Determinism. In the middle of the last century two men - Gregor Mendel, an Austrian monk, and Charles Darwin, an English naturalist, established the central theories of modern biology and changed the world forever. Darwin’s On the Origin of Species has been described as the book of the Millennium, “the only best-seller to change man’s conception of himself”. Through the rediscovery of Mendel’s work in the early decades of our century, evolutionary theory was transformed by the emergence of genetics as a science. Crick and Watson found DNA at Cambridge and announced that they had discovered the secret of life in a local pub, and the rest has been the most compulsive element in the intellectual history of the twentieth century. It seems as if almost every week we read about another gene which claims to determine our fate - whether it governs our intelligence, personality or sexual orientation. Many rail against what they see as “genetic determinism” - the idea that genes are the destiny we can do nothing about. Others willingly blame their anti-social behaviour on “criminal genes” - thus absolving themselves of any responsibility. Genetics may be all about inheritance but is inheritance all about the genes? With Steve Jones, Professor of Genetics, University College, London and author of Almost Like a Whale: The Origin of Species Updated; Matt Ridley, science journalist, chairman of the International Centre for Life and author of Genome: The autobiography of a species in 23 chapters.

Melvyn Bragg and guests discuss pain; something of which everyone has an individual experience. What causes it, how do we cope with it, what mechanisms are involved, what is the traditional view of pain and how is that being challenged today? Do we experience pain in the same way and how is emotional pain different from physical pain? What can our experience of pain tell us about ourselves and human consciousness? Is each individual human experience unique or are there experiences we can say apply across all of human consciousness? Is science a blunt instrument for examining subjective experience?With Patrick Wall, Professor of Physiology at St Thomas’ Hospital, London and author of Pain: The Science of Suffering; Semir Zeki, Professor of Neurobiology at University College, London.

Melvyn Bragg and guests discuss a question that has stalked the twentieth century: Intelligence. Since the first IQ tests were invented in 1905, the question of what makes Homo Sapiens stupid and what makes him clever has involved human kind in sterilisation, racism and misery. How do we define intelligence, how do we measure it; what are its origins and how do we uncover it? But are we any closer to understanding what this elusive quality of intelligence is? The debate still rages as to whether we are born with it or whether intelligence is something we develop as we grow, and evidence for either camp seems to pile up almost daily. With Dr Ken Richardson, educational psychologist, former Senior Lecturer, Open University and author of The Making of Intelligence; Professor Michael Ruse Philosopher of Biology, University of Guelph, Ontario and author of Mystery of Mysteries: Is Evolution a Social Construction?

Melvyn Bragg and guests discuss the shift that has gone on through the 20th century from our being an industrial society to what is often called ‘the information society’. Francis Fukuyama’s book, The Great Disruption talks of the third great shift in the whole history of humankind. Along with all the technological and economic changes, in the past thirty years we have seen massive social changes. What has been the cause of this shift and how will we recover the social cohesion that preceded it? With Francis Fukuyama, Hirst Professor of Public Policy, George Mason University, Washington DC and author of The Great Disruption: Human Nature and the Reconstitution of Social Order; Amos Oz, author and Professor of Hebrew Literature, Ben-Gurion University, Beer-Sheva.

Melvyn Bragg and guests discuss memory. At the start of the twentieth century Freud put memory at the centre of our psychology, and as the century has worn on what a nation remembers and what it should try to forget has become one of the binding political questions that modern societies face. As every second passes, humanity has a moment more to remember, and perhaps this fact alone goes a long way to explaining the ever changing role of memory, both in the mind of individuals and at the heart of the body politic. Memory, what to remember and when to forget, has personal and national implications. Whether we look to Chile, South Africa, Germany or Northern Ireland, these are all societies where the issue of memory is at the centre of the dilemmas and challenges they face. And in the mind of the individual too - as ever more forms of information crowd for space in our minds, and the image from someone else’s photograph can be more enduring than our own first hand experience of an event, can memory itself forever remain unchanged in its role within our psychology? Have our ways of remembering changed? Not in the sense neuro-biologists would explore the subject, but in its cultural and collective, as well as its individual, sense. “Memory is decidedly in fashion” writes Dr Nancy Wood, “whether attention is focused on the so-called return of repressed memories of the abused individual, or on the black holes in a nation’s recollection of its past. The topic of memory has become a compelling preoccupation”. With Professor Malcolm Bowie, Marshall Foch Professor of French Literature at Oxford University and Director of Oxford’s European Humanities Research Centre; Dr Nancy Wood, Chair of Media Studies, University of Sussex and author of Vectors of Memory.

Melvyn Bragg examines the history of what we know about the origins of the universe. Some four hundred years ago in Rome, one Giordano Bruno was burnt at the stake for his belief in other inhabited worlds - it’s a possibility which has fascinated scientists, writers, artists and the general public for centuries - and any consideration of the origins of life and matter on other planets, and indeed this one, inevitably raises huge questions. Do other worlds exist? How did our planet come into existence? How can we know anything at all about the origins of life and matter so many billions of years ago, and how has our thinking on these - amongst the deepest of questions - changed over the 20th century? Are we any closer to knowing whether other worlds exist and how our own planet came into being? And does the knowledge we have about these things change our perception of ourselves and our position in the universe?With Professor Sir Martin Rees, Astronomer Royal and Royal Society Research Professor in Astronomy and Physics, Cambridge University; Professor Paul Davies, theoretical physicist and Visiting Professor at Imperial College, London.

Melvyn Bragg and guests discuss the way perceptions of the importance of mathematics have fluctuated in the 20th century, the nature of mathematical ability, and what mathematics can show us about how life began, and how it might continue. Galileo wrote “this grand book the universe… is written in the language of mathematics”. It was said before Galileo and has been said since and in the last decades of the 20th century it is being said again, most emphatically. How important is maths in relation to other sciences at the end of the twentieth century - will it ever be made redundant, or is it increasingly crucial to our understanding of the world and ourselves? What insight can it give us into the origins of life, and the functioning of our brains, and what does it mean to say that maths has become more ‘visual’?With Ian Stewart, Professor of Mathematics and Gresham Professor of Geometry, University of Warwick; Brian Butterworth, Professor of Cognitive Neuroscience, University College, London.

Melvyn Bragg and guests discuss artificial intelligence. Can we create a machine that creates? Some argue so. And is consciousness, as we are, with headaches and tiffs and moods and small pleasures and sore feet - often all at the same time - capable of taking place in a machine? Artificial intelligence machines have been growing much more intelligent since Alan Turing’s pioneering days at Bletchley in World War Two. Its claims are now very grand indeed. It is 31 years since Stanley Kubrick and Arthur C Clarke gave us HAL - the archetypal thinking computer of the film 2001: A Space Odyssey. But are we any nearer to achieving the thinking, feeling computer? Or is it just a dream - and should it remain as one?With Igor Aleksander, Professor, Imperial College London and inventor of Magnus - a neural computer which he says is an artificially conscious machine; John Searle, Professor of Philosophy, University of California and one of only two people in the world to invent an argument, the Chinese Room Argument, which destroys the plausibility of the idea of conscious machines.

Melvyn Bragg examines the future of gene therapy and advances in evolutionary biology. Are we continuing to evolve? If so, what are the signs and if not, why not? And those apes, so very very near us in genetic kinship, why are they so far away in so much else, and will they ever evolve? And is evolution necessarily progression? If so, does our apparent lack of evolution mean lack of progress? Also on the evolutionary front, could electronic devices discover the means of self-replication, and what will that mean for us? The march of the life sciences after the discovery of DNA accelerates by the year but what are the implications?With Professor John Maynard Smith evolutionary biological theorist and Emeritus Professor of Biology at the University of Sussex; Colin Tudge, writer, journalist and Research Fellow at the Centre for Philosophy.

Melvyn Bragg and guests discuss the role of animals in humankind's search for knowledge. Since the Greek physician Galen used pigs for anatomical studies in the 2nd century, animals have been used by scientists to further human knowledge. Yet few, if any subjects in this country, raise such violent feelings and passions as animals and their place in our society. With the growing politicisation of animal rights, it is a subject which is increasing in intensity. Do animals have rights and do our needs permit us to use them still to enhance our own lives in the twentieth century? Is it still necessary to experiment on animals for the good of humankind? Or is that morally unacceptable and barbaric - particularly in the light of new research into animal consciousness?With Colin Blakemore, Professor of Physiology, Oxford University, President of the British Association for the Advancement of Science, Fellow of the Royal Society and targeted in the 1980s by animal welfare activists protesting at his research methods; Dr Lynda Birke, biologist, teacher at Lancaster and Warwick Universities, and previously worked for 7 years in animal behaviour at the Open University.

Melvyn Bragg and guests discuss the history of thought about space, and examines whether cyberspace has introduced a new concept of space in our world or if its roots are in Einsteinian physics. It would have seemed extraordinary to Dante or Newton, from their different perspectives, that at the end of the 20th century there would be learned scholars who would find no place for religion in the great schemes of thought and belief. In the 20th century our notions of physical space have been revolutionised. Einstein said that space was not a separate entity; we’ve probed and explored the outer reaches of our physical space with space flight, powerful telescopes and theoretical physics. But in the last 20 years, with the birth of the Internet, a virtual form of space has been introduced to us - cyberspace - where people can meet and communicate ideas; you sit at home, punch the keys and you can rove all over the world - the keyboard becomes a magic carpet. But does cyberspace introduce a new concept of space in our world? Or does it really have its roots in Einsteinian physics and even in Medieval theologyAccording to the science writer Margaret Wertheim, cyberspace - life on the surfing internet - gives us not only virtual reality, but a soul. Dr John Polkinghorne, the distinguished physicist and ordained priest in the C of E, is not happy with this news, but he does believe that religion is not destroyed by the new technology, and that latest theories in physics reinforce it. With The Reverend Dr John Polkinghorne, Fellow of Queen’s College, Cambridge and Canon Theologian of Liverpool; Margaret Wertheim, science writer and author of The Pearly Gates of Cyberspace: A History of Space from Dante to the Internet.

Melvyn Bragg and guests discuss the history of our ideas about the formation of language. The psychologist George Miller worked out that in English there are potentially a hundred million trillion sentences of twenty words in length - that’s a hundred times the number of seconds since the birth of the universe. “Language”, as Chomsky put it, “makes infinite use of finite media”. “Language”, as Steven Pinker puts it, “comes so naturally to us that it’s easy to forget what a strange and miraculous gift it is”. “All over the world”, he writes, “members of our species spend a good part of their lives fashioning their breath into hisses and hums and squeaks and pops and are listening to others do the same”. Jean Jacques Rousseau once said that we differ from the animal kingdom in two main ways - the use of language and the prohibition of incest. Language and our ability to learn it has been held up traditionally as our species’ most remarkable achievement, marking us apart from the animals. But in the 20th century, our ideas about how language is formed are being radically challenged and altered. With Dr Jonathan Miller, medical doctor, performer, broadcaster, author and film and opera director; Steven Pinker, cognitive scientist, Professor of Psychology and Director of the Centre for Neuroscience, Massachusetts Institute of Technology, California.

Melvyn Bragg and guests discuss the relevance of psychoanalysis at the end of the 20th century. It’s 100 years since Sigmund Freud, the founder of psychoanalysis, a term which he coined, published The Interpretation of Dreams. Sixty years after his death, Freud’s influence and the influence of that book, has been felt in the 20th century in everything from the arts, history and anthropology, to of course psychology and even science. Dreams have inspired political speeches, songs, and seduction, captivating and fascinating mankind since time immemorial. For Sigmund Freud, they were the key to unlocking the working of the unconscious. But at the end of the 20th century, has psychoanalysis become too fractured and too insistent on privileging the past over the present to go forward into the future? Has it failed to develop and adapt to an age increasingly dominated by science? With Dr Juliet Mitchell, psychoanalyst, Fellow of Jesus College, Cambridge, Department of Political and Social Sciences; Adam Phillips, psychoanalyst and author of The Beast in the Nursery.

Melvyn Bragg and guests discuss ageing. In 1900, 1% of the world’s population were over 65. In the 1990s nearly 8% are. By the year 2020, nearly 1/5th of the world’s population will be over 65 - the figure rises to 25% in the UK. We are now living longer than at any time in our history. How much do economic factors, rather than biological factors, determine what ageing really means and our attitude to it? And what are the ethical, economic and biological implications of living longer?Tom Kirkwood, is an expert on the science of ageing and he brings to bear a close study of how the ageing process is being arrested and speculates on the very great age some of us could and will reach. He has said: “Today’s older people are the vanguard of an extraordinary revolution in longevity that is radically changing the structure of society and altering our perceptions of life and death. The price for this success - and make no mistake it is a success - is that we now face the challenge of ageing.”Alan Walker is an expert in the sociology of ageing and he takes in the whole context, especially the economic dimension. With Professor Alan Walker, social gerontologist, advisor to the UN’s programme on Ageing and has chaired the European Commission’s observatory on Ageing and Older People; Professor Tom Kirkwood, Britain’s first professor of Biological Gerontology, University of Manchester and President of the British Society for Research into Ageing.

Melvyn Bragg and guests discuss the implications of the developments in genetic engineering. Out of the city of Cambridge in the mid century came DNA and out of Edinburgh at the end of the century came the cloning of Dolly the sheep. These two facts might well do more to change the world literally, and our view of the world, than anything else that has happened at any time. Genetics have become the conversation of our day and with the Human Genome Project lumbering towards completion, its power grows. But are the consequences likely to be destructive and will what we think of as a human being, a personality, or even a person, change uncomfortably and irredeemably? With Grahame Bulfield, geneticist, honorary professor, Edinburgh University and Director of the Roslin Institute, Edinburgh; Bryan Appleyard, features writer for The Sunday Times and author of Brave New Worlds: Genetics and the Human Experience.

Melvyn Bragg and guests marvel at our brains and discuss how at the end of a century of research we still understand so little about how they work.Developments in the understanding of the brain represent one of the major leaps forward in science in the 20th century, and the research is gathering pace and intensity. It’s a subject which captures the imagination, particularly the search for consciousness whatever that might be, and brings together some of the newest technology and the oldest belief systems. What a piece of work is the brain - a grain-of-sand-sized piece contains one hundred thousand neurons, two-million axons and one billion synapses which all talk to each other. How far we have got with our understanding of the brain and what can it tell us about ourselves and the world we live in?With Professor Susan Greenfield, director of the Royal Institution, Professor of Pharmacology, Oxford University and Professor of Physics at Gresham College; Professor Vilayanur Ramachandran, Professor of Neuroscience and Psychology, Director of the Brain Perception Laboratory, University of California in San Diego and Professor at the Salk Institute.

Melvyn Bragg and guests discuss how our increased knowledge of the functioning of the brain and the mechanisms of memory in the 20th century has changed our feelings about our own natures, and our approach to the behaviour and treatment of others.Many questions have been thrown up this century by our growing knowledge about how the brain and the mind function. How easy is it to establish the relationship between the two, and what light can this relationship throw on our understanding of our own and others natures? With Steven Rose, Professor of Biology and Director of the Brain and Behaviour Research Group, Open University, Dan Robinson, Distinguished Research Professor, Georgetown University and visiting lecturer in Philosophy and Senior Member of Linacre College, Oxford University.

Melvyn Bragg and guests discuss how perceptions of science and the power of science have changed in the 20th century. Does scientific endeavour increasingly concern itself with doubt rather than certainty, and is it coming any closer to integrating with other disciplines - philosophy or the social sciences? How much does the scientific explanation of the world owe to a wish for coherent understanding we all have, rather than objective observation, and why are we alternately disapproving of, then obsessively over-enthusiastic about new scientific theories? How far has specialisation in the sciences obscured our view of the world in its entirety, and if scientists want to operate within a social framework, can they do so and still claim to be objective and value-free in their findings?With John Gribbin, Visiting Fellow in Astronomy, University of Sussex and consultant to New Scientist; Mary Midgley, moral philosopher and former Senior Lecturer in Philosophy, University of Newcastle.

Melvyn Bragg and guests discuss whether the mass of scientific understanding and knowledge we have accumulated has destroyed our sense of poetic wonder at the world. Has our sense of awe at how the world works obscured our desire to know why it works the way it does? With Richard Dawkins evolutionary biologist, reader in Zoology and Fellow of New College, Oxford, Charles Simonyi Chair of Public Understanding of Science, Oxford University and author of Unweaving The Rainbow: Science, Delusion and The Appetite For Wonder; Ian McEwan, novelist, and author of the Booker prize winning novel Amsterdam.