Behind every line on a graph, there lies an extraordinary human story. Mathematician Hannah Fry is here to tell us ten of them.

There is a bizarre number in maths referred to simply as ‘i’. It appears to break the rules of arithmetic - but turns out to be utterly essential for applications across engineering and physics. We’re talking about the square root of -1. WHICH MAKES NO SENSE. Professor Fry waxes lyrical about the beauty and power of this so-called ‘imaginary’ number to a sceptical Dr Rutherford. Dr Michael Brooks tells the surprising story of the duelling Italian mathematicians who gave birth to this strange idea, and shares how Silicon Valley turned it into cold hard cash. It's all about oscillations, Professor Jeff O’Connell demonstrates. And finally, Dr Eleanor Knox reveals that imaginary numbers are indispensable for the most fundamental physics of all: quantum mechanics. Imaginary, impossible…but essential! Contributors: Professor Jeff O’Connell, Ohlone College California, Dr Michael Brooks, Author of 'The Maths That Made Us', and Dr Eleanor Knox, Philosopher of Physics at KCL and a Senior Visiting Fellow at the University of Pittsburgh. Producer: Ilan Goodman

This episode will render you oblivious, conked out and blissfully unaware. It’s about anaesthetics: those potent potions that send you into a deep, deathly sleep. Listener Alicia wants to know how they work, so our sleuths call on the expertise of consultant anaesthetist Dr Fiona Donald. Fiona shares her experience from the clinical frontline, and explains what we do and don’t know about how these chemicals work their mind-numbing magic. We hear about ground-breaking research led by Professor Irene Tracey, which reveals how a pattern of slow brain waves can be used to determine the optimum dosage of these dangerous drugs. And finally, Drs Rutherford and Fry wonder: what does all this tell us about normal consciousness? Professor Anil Seth shares how we can use brain tech to measure different levels of conscious awareness – from sleepy to psychedelic. Presenters: Hannah Fry and Adam Rutherford Producer: Ilan Goodman

‘Can we bring back extinct species?’ wonders listener Mikko Campbell. Well, Professor Fry is pretty excited by the prospect of woolly mammoths roaming the Siberian tundra once more. And everyone is impressed with the science that might make it happen. But Dr Rutherford comes out STRONGLY against the whole thing. Can our expert guests win him over? Dr Helen Pilcher shares the tale of Celia the lonely mountain goat, and makes the case for cloning to help protect species at risk of extinction. Professor Beth Shapiro sets out how biotech company ‘Colossal’ plans to engineer Asian elephants’ DNA to make a new group of mammoth-like creatures. And we hear how genetic technologies are being used in conservation efforts around the world. BUT WHAT ABOUT T-REXES? Not gonna happen. Sorry. Contributors: Dr Helen Pilcher, author of ‘Bring Back the King: The New Science of De-Extinction’, Professor Beth Shapiro from the University of California Santa Cruz, Dr Ben Novak of Revive and Restore and Tullis Matson from Nature’s SAFE. Presenters: Hannah Fry and Adam Rutherford Producer: Ilan Goodman

The Great Pyramids of Giza are awesome feats of engineering and precision. So who built them - and how? Was it a mysteriously super-advanced civilization now oddly extinct? Was it even aliens? Nah, course not! Rutherford and Fry investigate how these inspiring monuments were really constructed, and learn about the complex civilisation and efficient bureaucracy that made them possible. Professor Sarah Parcak busts the myth that they were built by slaves. In fact, she reveals, it was gangs of well-paid blokes fuelled by the ancient Egyptian equivalent of burgers and beer. And Dr Chris Naunton explains how it was not some mysterious tech, but incredible organisation and teamwork which made it possible to transport massive stone blocks over long distances several thousand years before trucks arrived. Dr Heba Abd El Gawad points out how racism led to bizarre assumptions in the history of archaeology, and how those assumptions linger in contemporary conspiracy theories which refuse to accept that Egyptians could have built the pyramids themselves! Presenters: Hannah Fry and Adam Rutherford Contributors: Professor Sarah Parcak, University of Alabama, Dr Chris Naunton, Egyptologist and broadcaster, Dr Heba Abd El Gawad, University College London Producers: Ilan Goodman & Emily Bird

Magnets are inside loads of everyday electronic kit - speakers, motors, phones and more - but listener Lucas is mystified: what, he wonders, is a magnetic field? Our sleuths set out to investigate the mysterious power of magnets, with the help of wizard / physicist Dr Felix Flicker - author of the The Magick of Matter - and materials scientist Dr Anna Ploszajski. They cover the secrets of lodestones - naturally occurring magnetic rocks - and how to levitate crystals, frogs and maybe even people. Matthew Swallow, the Chair of the UK Magnetics Society, explains why magnets make the best brakes for rollercoasters, and Dr Ploszajski explains how magnetically-induced eddy currents are used to sort through our recycling. Finally, Dr Flicker persuades Adam and Hannah that to really understand magnetic fields you have to leave classical physics behind, and go quantum... So our sleuths take a leap into the strange subatomic realm. Contributors: Dr Felix Flicker, Lecturer in Physics at Cardiff University and author of ‘The Magick of Matter’, Dr Anna Ploszajski, materials scientist and author of ‘Handmade’, Matthew Swallow, Chair of the UK Magnetics Society Presented by Hannah Fry and Adam Rutherford Producer: Ilan Goodman

Close your eyes and think of a giraffe. Can you see it? I mean, *really* see it - in rich, vivid detail? If not - you aren’t alone! We’ve had scores of messages from listeners who report having a ‘blind mind’s eye’. They don’t see mental images at all and they want to know why. Jude from Perth wants to know what makes her brain different, and Diane from Scotland wonders whether it affectes her ability to remember family holidays. Our sleuths learn that this is a condition recently termed ‘aphantasia’. They meet the chap who came up with the name, Professor Adam Zeman, a neurologist from the University of Exeter, and quiz him on the brain mechanisms behind this mystery. Professor Julia Simner - a psychologist who, herself, doesn’t see mental images - shares the surprising research into how aphants differ slightly from others in a range of cognitive skills. We also hear about the world class artists and animators who can’t visualise - but can create beautiful, imaginary worlds. Philosophy professor Fiona Macpherson from the University of Glasgow, deepens the mystery: perhaps this largely hidden phenomenon is behind some of the most profound disagreements in the history of psychology. Our mental experiences are all very different - maybe that’s why thinkers have come up with such different theories about how our minds work. Search for the “VVIQ” or Vividness of Visual Imagery questionnaire to take the test yourself. Look for “The Perception Census” to take part in this massive online study of perceptual variation. And look up the 'Aphtantasia Network' if you're curious to find out more. Presenters: Hannah Fry and Adam Rutherford Contributors: Professor Adam Zeman, Professor Julia Simner, Professor Fiona Macpherson Producer: Ilan Goodman

The new series kicks off very soon! As a little aperitif, Hannah and Adam review some surprising studies published in scientific journals. Warning: contains fruity language and grisly medical scenarios…

What do you get if you smash two hydrogen nuclei together? Helium and lots of energy. That’s no joke – it's nuclear fusion! Nuclear fusion is the power source of the sun and the stars. Physicists and engineers here on earth are trying to build reactors than can harness fusion power to provide limitless clean energy. But it’s tricky... Rutherford and Fry are joined by Dr Melanie Windridge, plasma physicist and CEO of Fusion Energy Insights, who explains why the fourth state of matter – plasma – helps get fusion going, and why a Russian doughnut was a key breakthrough on the path to fusion power. Dr Sharon Ann Holgate, author of Nuclear Fusion: The Race to Build a Mini Sun on Earth, helps our sleuths distinguish the more familiar nuclear fission (famous for powerful bombs) from the cleaner and much less radioactive nuclear fusion. And plasma physicist (another one!) Dr Arthur Turrell describes the astonishing amount of investment and innovation going on to try and get fusion power working at a commercial scale. Contributors: Dr Melanie Windridge, Dr Sharon Ann Holgate, Dr Arthur Turrell Producer: Ilan Goodman

Sneezes, wheezes, runny noses and red eyes - this episode is all about allergies. An allergic reaction is when your immune system reacts to something harmless – like peanuts or pollen – as if it was a parasitic invader. It’s a case of biological mistaken identity. Professor Judith Holloway from the University of Southampton guides our sleuths through the complex immune pathways that make allergies happen and tells the scary story of when she went into anaphylactic shock from a rogue chocolate bar. Professor Adam Fox, a paediatric allergist at Evelina Children’s Hospital, helps the Drs distinguish intolerances or sensitivities – substantial swelling from a bee sting, for example - from genuine allergies. Hannah’s orange juice ‘allergy’ is exposed as a probable fraud! Hannah and Adam explore why allergies are on the increase, and Professor Rick Maizels from the University of Glasgow shares his surprising research using parasitic worms to develop anti-allergy drugs! Producer: Ilan Goodman Contributors: Professor Judith Holloway, Professor Adam Fox, Professor Rick Maizels

Hungry for pi? Chow down on this! Pi is the ratio between a circle’s diameter and its circumference. Sounds dull – but pi turns out to have astonishing properties and crop up in places you would never expect. For a start, it goes on forever and never repeats, meaning it probably contains your name, date of birth, and the complete works of Shakespeare written in its digits. Maths comedian Matt Parker stuns Adam with his ‘pie-endulum’ experiment, in which a chicken and mushroom pie is dangled 2.45m to form a pendulum which takes *exactly* 3.14 seconds per swing. Mathematician Dr Vicky Neale explains how we can be sure that the number pi continues forever and never repeats - despite the fact we can never write down all its digits to check! She also makes the case that aliens would probably measure angles using pi because it’s a fundamental constant of the universe. NASA mission director Dr Marc Rayman drops in to explain how pi is used to navigate spacecraft around the solar system. And philosopher of physics Dr Eleanor Knox serves up some philoso-pi, revealing why some thinkers have found pi’s ubiquity so deeply mysterious. Hannah grins with delight for most of show. It’s all maths! Producer: Ilan Goodman Contributors: Matt Parker, Dr Vicky Neale, Dr Marc Rayman, Dr Eleanor Knox

Why are some smells so nasty and others so pleasant? Rutherford and Fry inhale the science of scent in this stinker of an episode. Our sleuths kick off with a guided tour of the airborne molecules and chemical receptors that power the sense of smell. Armed with a stack of pungent mini-flasks, Professor Matthew Cobb from the University of Manchester shows Hannah and Adam just how sensitive olfaction can be, and how our experience of some odours depends on our individual genetic make-up. Dr Ann-Sophie Barwich from Indiana University reveals how most everyday smells are complex combinations of hundreds of odorants, and how the poo-scented molecule of indole turns up in some extremely surprising places. With the help of a flavoured jellybean and some nose clips, Hannah experiences how smell is crucial to flavour, adding complexity and detail to the crude dimensions of taste. Speaking of food, listener Brychan Davies is curious about garlic and asparagus: why do they make us whiff? Professor Barry Smith from the Centre for the Study of the Senses reveals it's down to sulphur-containing compounds, and tells the story of how a cunning scientist managed to figure out the puzzle of asparagus-scented urine. Finally, another listener Lorena Busto Hurtado wants to know whether a person’s natural odour influences how much we like them. Barry Smith says yes - we may sniff each other out a bit like dogs - and cognitive neuroscientist Dr Rachel Herz points to evidence that bodily bouquet can even influence sexual attraction! Producer: Ilan Goodman Contributors: Professor Matthew Cobb, Professor Barry Smith, Dr Ann-Sophie Barwich, Dr Rachel Herz

How do winds start and why do they stop? asks Georgina from the Isle of Wight. What's more, listener Chris Elshaw is suprised we get strong winds at all: why doesn't air just move smoothly between areas of high and low pressure? Why do we get sudden gusts and violent storms? To tackle this breezy mystery, our curious duo don their anoraks and get windy with some weather experts. Dr Simon Clark, a science Youtuber and author of Firmament, convinces Adam that air flow is really about the physics of fluids, which can all be captured by some nifty maths. The idea of pressure turns out to be key, so Hannah makes her own barometer out of a jar, a balloon and some chopsticks, and explains why a bag of crisps will expand as you walk up a mountain. Professor Liz Bentley, Chief Executive of the Royal Meteorological Scoiety, reveals how the dynamics of a simple sea breeze – where air over land is heated more than air over water – illustrates the basic forces driving wind of all kinds. Then everyone gets involved to help Adam understand the tricky Coriolis effect and why the rotation of the Earth makes winds bend and storms spin. And Professor John Turner from the British Antarctic Survey explains why the distinctive features of the coldest continent make its coastline the windiest place on earth. Producer: Ilan Goodman Contributors: Dr Simon Clark, Professor Liz Bentley, Professor John Turner

DO WE HAVE YOUR ATTENTION? Good! But how does that work!? Our intrepid science sleuths explore why some things immediately catch your eye - or ear - while others slip by totally unnoticed. Even, on occasion, basketball bouncing gorillas. Professor Polly Dalton, a psychologist who leads The Attention Lab at Royal Holloway University, shares her surprising research into ‘inattentional blindness’ - when you get so absorbed in a task you can miss striking and unusual things going on right in front of you. Dr Gemma Briggs from the Open University reveals how this can have dangerous everyday consequences: you are four times more likely to have a crash if you talk on the phone while driving - even handsfree. Drs Rutherford and Fry also hear from stroke survivor Thomas Canning, who developed the tendency to ignore everything on the left side of space, despite his vision being totally intact. And Dr Tom Manly, from the University of Cambridge’s Cognition and Brain Sciences Unit, helps our sleuths unpack the neuroscience of this fascinating condition. Producer: Ilan Goodman Contributors: Professor Polly Dalton, Dr Gemma Briggs, Dr Tom Manly

We asked you to send us the boldest, barmiest bits of published research you could find and, dear Curios, you didn't disappoint! It’s time for some silly science.

The world is full of colour! But, wonders listener Maya Crocombe, ‘how do we see colour and why are some people colour blind?’ Dr Rutherford and Professor Fry set out to understand how special light-sensitive cells in our eyes start the process of colour perception, why people sometimes have very different experiences of colour and whether, in the end, colour is really just ‘in our heads’. Dr Gabriele Jordan from Newcastle University explains why lots of men struggle to discriminate between certain colours and why there were lots of complaints from colour-blind viewers when Wales played Ireland at rugby. Professor Anya Hurlbert, also from Newcastle University, tackles the most divisive of internet images: The Dress! Did you see it as blue-black or yellow-gold? Anya explains why people see it so differently, and why our ability to compensate for available light is so useful. Finally, Dr Mazviita Chirimuuta, a philosopher at the University of Edinburgh, gives us her take on what all this means: are colours real, or just in our minds? If you want to see some of the images and activities referenced in the episode read on... To take the colour perception test which Hannah and Adam do in the epsiode, search for the 'Farnsworth Munsell Hue test' - you can do it online for free. To see the Dunstanborough Castle illusion as described in the episode, check out the Gallery section on the Curious Cases BBC website. To learn more about colour blindness, and for support and resources go to colourblindawareness.org Producer: Ilan Goodman

Mathematician Hannah Fry and geneticist Adam Rutherford investigate your everyday science queries. Today, they get stuck into two questions about tides. Lynn Godson wants to know why isn’t high tide at the same time at all points around the coast? Whilst Tim Mosedale asks, could we ever harness tidal power commercially? Did you think tides are caused by the pull of the Moon? And that they come in and out twice a day? Well, yes, that’s true but it turns out there’s so much more to it than that, especially here in the UK, which has the second largest tidal range in the world at the Seven Estuary near Bristol, coming in at an average of 15 metres (50ft in old money). But why should high and low tide times be so different even in places that are relatively close to each other? The answer partly lies in something called bathymetry (which has more to do with baths than you might think – well basins at any rate). As for harnessing sea power, there are some ambitious projects currently in development and predictions that wave and tidal could make up as much as 15 percent of the UK’s energy needs in future. But how realistic is this and how do you ensure that your power generators can survive the rigours of the ocean – storms, saltwater and all those pesky barnacles? To help answer these queries, Hannah and Adam are joined by Physicist and Oceanographer, Helen Czerski and Professor Deborah Greaves OBE, who heads up the COAST lab at the University of Plymouth which studies marine renewable energy technologies. Producers: Rami Tzabar and Jen Whyntie

Why does human hair go grey and is it ever possible for it to go white overnight from shock? Hannah and Adam explore why hair goes grey, how much stressful life events and a lack of sleep can speed up the process. They hear from the pilot whose hair turned white after a flight where all 4 of his engines failed after flying through a volcanic ash cloud - was the shock responsible? They also uncover new research which has shown it's possible for greying hair to return to its natural colour and ask if this finding could be exploited to uncover a cosmetic way to reverse hair greying?

Two eyes, two arms, two legs - we’re roughly symmetrical on the outside, but inside we’re all over the place! We just have one heart, which is usually on the left, one liver on the right, one spleen and one appendix….‘Why is that?’ wonders listener Joanne. Our science sleuths discover that being symmetrical down the middle - at least on the outside - is by far the most common body plan across the animal kingdom. Professor Sebastian Shimeld from the University of Oxford takes us on a journey into the deep evolutionary past, to uncover how two-sided body structures first emerged in ancient worm-like creatures, and why this layout eventually proved so useful for swimming, walking and flying. Garden snails turn out to be a surprising exception – their shells coil in one direction and on just one side of their body. Professor Angus Davison from the University of Nottingham tells the tale of his international quest to find a romantic partner for Jeremy – a rare left-coiling snail who could only mate with another left-coiling snail! Dr Daniel Grimes from the University of Oregon unfolds the delicate mechanisms by which an initally symmetrical embryo starts to develop differently down one side, and everyone puzzles over the mystery of the left-handed 'mirror molecules' - so called L-amino acids - which turn out to be the building blocks of every living organism. A curious case indeed! Presenters: Hannah Fry and Adam Rutherford Producer: Ilan Goodman

We use Wi-Fi every day, but do you know how it works? “Is it waves and science or just some mystical magical force?” wonders listener Abby. Well, our science sleuths are on the case. To help them navigate the strange realm of electromagnetic waves they are joined by Andrew Nix, Professor of Wireless Communication Systems from the University of Bristol. He explains why your wi-fi router won’t heat up your baked beans, but your microwave will. Andrea Goldsmith, Professor of Electrical and Computer Engineering at Princeton University, also joins to reveal how these waves are crammed full of 0s and 1s- whether that's a pic of your pets or a video chat with pals. And finally, how do you get the best Wi-Fi at home? Dr Rutherford, it turns out, has made some rookie errors... Listen out for our top tips so you don't make them too! Presenters: Hannah Fry and Adam Rutherford Producer: Ilan Goodman

‘Why are teens prone to risky behaviour?’ asks Dr Mark Gallaway, ‘especially when with their friends?’ 13 year old Emma wonders why she’s chatty at school but antisocial when she gets home. And exasperated mum Michelle wants to know why her teens struggle to get out of bed in the morning. Swirling hormones and growing bodies have a lot to answer for but, as Professor of Psychology from the University of Cambridge Sarah-Jayne Blakemore explains, there’s also a profound transformation going on in the brain. Hannah and Adam discover how the adolescent brain is maturing and rewiring at the cellular level and why evolution might have primed teens to prefer their peers over their parents. Frances Jensen, Professor of Neurology at the University of Pennsylvania, tells us how all these brain changes can impact social relationships. And Dr Rachel Sharman, a sleep researcher from the University of Oxford, reports the surprising findings from her sleep study tracking 100 teenagers around the UK. Producer: Ilan Goodman

Our sci-curious detectives will be investigating a menagerie of mysteries sent in by listeners - from teenage brains to the magic of Wi-Fi and our strangely symmetrical bodies.

As huge tech companies race to develop ever more powerful AI systems, the creation of super-intelligent machines seems almost inevitable. But what happens when, one day, we set these advanced AIs loose? How can we be sure they’ll have humanity’s best interests in their cold silicon hearts? Inspired by Stuart Russell’s fourth and final Reith lecture, AI-expert Hannah Fry and AI-curious Adam Rutherford imagine how we might build an artificial mind that knows what’s good for us and always does the right thing. Can we ‘programme’ machine intelligence to always be aligned with the values of its human creators? Will it be suitably governed by a really, really long list of rules - or will it need a set of broad moral principles to guide its behaviour? If so, whose morals should we pick? On hand to help Fry and Rutherford unpick the ethical quandaries of our fast-approaching future are Adrian Weller, Programme Director for AI at The Alan Turing Institute, and Brian Christian, author of The Alignment Problem. Producer - Melanie Brown Assistant Producer - Ilan Goodman

The refrain ‘robots will take your job’ is one heard with increased frequency, but how quickly is automation of the labour force really happening and would it really be such a bad thing if many jobs were powered by artificial intelligence? In this third episode, inspired by this year’s BBC Reith lectures from AI expert Stuart Russell, Adam Rutherford and Hannah Fry - together with expert guests - imagine what the future of work might look like. Will the move towards increased use of artificial intelligence in areas like healthcare, customer service and manufacturing see jobs disappear or will it simply create new ones we cannot yet imagine? Economists are divided on what the effects of machines doing our jobs will be. Some argue it could lead to wide scale unemployment, or skilled workers being forced in into lower skilled jobs. Others believe this might be an opportunity to reshape our socio-economic systems to one where workers are freed from tedious repetitive jobs and instead have more leisure time to pursue their own interests and find meaning outside of work. Will we all one day receive a universal basic income and stop asking each other what we do for work when we meet someone new? Producer - Melanie Brown Assistant Producer - Ilan Goodman

What if a despotic leader could programme a swarm of drones to kill a set of identified targets with just the push of a button? Due to ever expanding AI capabilities this extreme dystopian vision may not be technically unfeasible. In this second of a four part series responding to this year's BBC Reith lectures from Stuart Russell, Adam Rutherford and Hannah Fry unpick the role of AI in warfare. Joining them to help them navigate the battlefield of information is Ulrike Franke, a senior policy fellow at the European Council on Foreign Relations who specialises in the future of warfare. Together they will be investigating 'lethal autonomous weapons' - these are weapons that can find, chose and kill human targets without human supervision. We will be discussing how advanced this technology actually is - some think the world may have already experienced the first ever autonomous strike in Libya. What are the repercussions of this technology for safety on the battlefield , and what are the wider geo-political ramifications? Stuart Russell has deep concerns over the development of these types of weapons and Rutherford and Fry pick apart some of the ethical debates this technology raises. Who would be responsible if a system malfunctioned and killed a civilian? What's to stop it getting into the wrong hands? Should we even be creating these weapons in the first place - do we instead need a convention banning them? And is that even possible?

Artificial Intelligence (AI) is already ubiquitous in our lives. It curates our nightly TV entertainment, connects us to our friends online and navigates us, mostly successfully, to our destinations. However these uses are just the beginning, and it will likely bring societal changes we can’t yet imagine. In this year’s BBC Reith lectures, AI expert Professor Stuart Russell will be exploring how AI has been represented in popular fiction, envisaging how this technology might shape our futures and how we best prepare for it. So who better to unwrap his ideas than science sleuths Adam Rutherford and Hannah Fry, with their customary curiosity and irreverent insights? In this, the first of four episodes, Rutherford and Fry – together with guests author and podcaster Azeem Azhar and AI scholar Kate Crawford - will be unravelling what we actually mean by AI, exploring how far machine learning already underpins our lives, imagining the functions it might provide in the future and asking what challenges and risks might lie ahead. Can AI transform society as profoundly as electricity once did leading to a golden age for humanity, or have we all watched too many sci-fi movies?

Whilst watching a documentary about some poisonous frogs, Curio Janni in Amsterdam, started to wonder what would happen if a frog licked itself or another frog of the same species. She asks Dr Adam Rutherford and Professor Hannah Fry to investigate whether an animal would react badly to a toxin it itself produces? In essence, 'can a venomous snake kill itself by biting itself?' Of course the answer is complicated, but the sleuths know exactly who to ask. Steve Backshall, award-winning wildlife explorer, best known for his BBC series 'Deadly 60'. Author of 'Venom – Poisonous Creatures in the Natural World'. Steve has been bitten, stung and spat at by a plethora of venomous creatures during his career. He also studied the first-known venomous newt - the sharp-ribbed newt - a creature that has sharpened ribs that when it's under attack, it will squeeze its body force those ribs out through its skin, coating them in venom, which is then delivered into the mouth of an attacker. Professor Nick Casewell, studies venomous snakes and their impact on humans. He works on treatments for snakebites at the Liverpool School of Hygiene and Tropical Medicine. Snakebites have a huge impact on communities in South Asia, Sub-Saharan Africa and South America. It's now been reinstated as one of the most serious neglected tropical diseases by the World Health Organisation. Traditional treatments - antivenins - can be expensive, difficult to access and don't always work - Nick is looking into alternative medicines to treat snakebite victims. Dr. Ronald Jenner is Principle Researcher in the Comparative Venomics group at the Natural History Museum's Life Sciences, Invertebrates Division and co-wrote the book ‘Venom -the secrets of nature's deadliest weapon.’ He explains the evolutionary arms race between venomous predators and their prey and poisonous prey and their predators. He explains how resistance to venom has evolved and how venom has evolved to be more or less powerful over time, answering another Curio - Scott Probert's question on the evolution of venom. Christie Wilcox wrote 'Venomous – How Earth’s Deadliest Creatures Mastered Biochemistry'. She studied the molecular basis of lionfish venom. Christie describes how venom and immunity to venom works at the molecular level. Presenters - Adam Rutherford and Hannah Fry Produced by Fiona Roberts

'What is the slipperiest thing in the world?' asks 8 year old Evelyn. Why do my feet slip on a wet floor but when my feet are even slightly moist it's nearly impossible to put on a pair of socks without falling over and cursing the universe. What is going on here?' asks Evelyn's Dad, Sam. Hannah and Adam investigate the science of friction and lubrication - so called 'tribology' with the help of tribologists and mechanical engineers Professor Ashlie Martini from California University Merced and Professor Roger Lewis from the University of Sheffield. With their help Hannah and Adam find out why leaves on the line are so slippery, what happens to graphite in space and what is the slipperiest food. Professor of Materials, Mark Miodownik from University College London explains what's going on when friction stops two materials sliding past each other and wonders whether the slipperiest substance was actually discovered accidentally in a lab by scientists looking for something completely different. Also in the programme why the ability to reduce friction, even by minuscule amounts could have a huge impact for sustainability and reducing energy use. Producers: Jen Whyntie and Pamela Rutherford First broadcast on BBC Radio 4 in 2021.

Why does my heart not ache after exercise? asks listener Keith. Rutherford and Fry explore how and why heart muscle cells are special. Dr Mitch Lomax is a sports scientist at the University of Portsmouth. She helps actual Olympic swimmers get faster. She explains how most of the muscles attached to our skeletons work: Tiny fibres use small-scale cellular energy, which, when all these fibres work in concert, turns into visible muscular movement. Mitch also explains how the dreaded Delayed Onset Muscle Soreness, or DOMS, can hit, taking a stair-wincing 48-72 hours to peak after exercise. But skeletal muscles turn out to be quite different to heart muscles, as consultant cardiologist Dr Rohin Francis explains. Heart cells are more efficient and don't get fatigued like skeletal muscle cells. They are extremely energetic and 'just want to beat'. He also explains that the sensory feedback from the heart muscles is different too. They have a different sort of nerve supply, with fewer sensory nerves, so that there is less chance of pain signals being sent to the brain. However, heart cells' incredible abilities are counterbalanced by one Achilles-like flaw: They cannot easily heal. Professor Sanjay Sinha is a British Heart Foundation (BHF) Senior Research Fellow and a Professor in Cardiovascular Regenerative Medicine at the University of Cambridge. His job is to fix broken hearts and he explains to Adam how new research into stem cells could be used to fix normally irreparable heart cells. Presenters: Hannah Fry and Adam Rutherford Producers: Jennifer Whyntie and Fiona Roberts First broadcast on BBC Radio 4 in 2021.

“I don’t really understand why water has so many properties on different scales ranging from very large and cosmic to very small quantum and quarky - Could you help by zooming in and out on water to explain what is known about it? "Asks Neil Morton in Stirling. “Why does boiling water sound different to cold water?’ asks Barbara Dyson in Brittany in France Ollie Gordon, in Christchurch in New Zealand, wants to know ‘why water is essential for all life as we know it?’ And many more questions on the weirdness of water are tackled by super science sleuths Hannah Fry and Adam Rutherford. With assistance from: * Quantum physicist Professor Patricia Hunt, at the Victoria University in Wellington in New Zealand * Science writer and author of ‘H2O – a biography of water’ Philip Ball * Physicist and bubble expert in the Department of Mechanical Engineering at UCL, Dr Helen Czerski. Producer: Fiona Roberts First broadcast on BBC Radio 4 in October 2021.

“I don’t really understand why water has so many properties on different scales ranging from very large and cosmic to very small quantum and quarky - Could you help by zooming in and out on water to explain what is known about it?" asks Neil Morton in Stirling. Rutherford and Fry learn about the special hydrogen bonds that makes water such an unusual liquid. Quantum physicist Professor Patricia Hunt, at the Victoria University in Wellington in New Zealand explains to Hannah the quantum properties of individual water molecules and how they link up with other water molecules in liquid water and solid ice. She describes the hydrogen bonds that give water some of it’s weird and wonderful properties such as why ice floats, why water is able to store huge amounts of heat and why water has such a strong surface tension. Science writer and author of ‘H2O – a biography of water’ Philip Ball describes how in the 18th century it was discovered that water was not one of the classical elements, but a compound liquid of water and hydrogen and explains to Adam why there are at least 15 different types of ice. Physicist Dr. Helen Czerski sets the record straight on how ice forms in oceans and lakes and why water is at its densest at 4 degrees Centigrade and not zero. Presenters: Hannah Fry & Adam Rutherford Producer: Fiona Roberts First broadcast on BBC Radio 4 in October 2021.

How do guide dogs know where they're going? It's not like their handler whispers in their ear and asks to go to the pharmacy, maybe the toothpaste aisle. So how does it work? asks Charlotte, aged 42. Dogs and humans have gone paw in hand for thousands of years. Historic and genetic evidence shows we’ve shaped each other's existence over millennia. But dogs were only first trained as guides for blind people in the UK 90 years ago. What’s the biology behind this extraordinary partnership? Hannah heads to Guide Dogs UK’s training school in Royal Leamington Spa. She meets up with expert Graham Kensett to find out what it takes to make a guide dog from nose to tail, starting from before birth and following the life course through to retirement. Hannah also meets the delightful Wendy and Wilmott, a German shepherd and a retriever cross. Despite both still growing into their ears, they show her their already extraordinary skill set, from tackling obstacle courses to safely crossing roads. Cool, calm, patient, unflappable: Guide dogs are the astronauts of the canine world. But, as trainer Jenna explains, it’s all in the partnership with the owner, who needs to do plenty of work in terms of training and learning routes to journey in harmony with their furry guide. Richard Lane has owned guide dogs for over 25 years, and confirms this first hand. He reveals just how he gets to the toothpaste aisle, and tells Adam how at its peak a partnership can navigate London Waterloo station better than some sighted people, even at rush hour. Richard also explains how deeply felt the bond that forms between owner and dog is, and describes the hardest part of guide dog ownership: Letting go at the end. Presenters: Hannah Fry & Adam Rutherford Producer: Jen Whyntie A BBC Audio Science Unit production for BBC Radio 4

Rutherford and Fry are back in the business of solving your science queries and rooting out the quirks and conundrums of everything that is science!

It was a dark and stormy night. A secret message arrived addressed to Rutherford & Fry from a mysterious woman called Heidi Daugh, who demanded to know: "Why do people like to be scared? For example, going on scary amusement park rides and watching horror movies that make you jump.” What followed was an investigation, which would test our intrepid duo to their very limits. They explore the history of horror, starting with its literary origins in the Gothic fiction classic 'The Castle of Otranto'. Adam challenges Hannah to watch a horror film without hiding behind a cushion. She quizzes horror scholar Mathias Clasen to find out why some people love the feeling of terror, whilst it leaves other cold. Sociologist Margee Kerr and psychologist Claudia Hammond are also on hand to explore why scary movies are so powerful and popular. Then Rutherford and Fry investigate the more physical side of fear, when they delve into the history of roller coasters to investigate why we enjoy being scared. Never ones to shy away from a challenge, the pair attempt to channel their inner adrenaline junkies with a trip on one the UK's scariest roller coasters at Thorpe Park. David Poeppel from New York University studies the science of screaming, and we discover what makes screams uniquely terrifying. Plus, psychologist and broadcaster Claudia Hammond describes some early experiments which tested how fear affects our body. This episode is a remake of two earlier broadcast episodes. Producers: Fiona Roberts & Michelle Martin Presenter: Adam Rutherford & Hannah Fry First broadcast on BBC Radio 4 in February 2021.

Why are some people left-handed, whereas the majority are right handed? Rutherford and Fry revisit The Sinister Hand episodes to further investigate handedness in humans and animals. They considered cockatoos, chimpanzees and Hannah's dog, Molly, to discover that humans are unique, with just one in ten of us being left-handed. They ask if there is an evolutionary reason for just 10% of the human population being southpaws Hannah talks to primatologist Prof Linda Marchant from Miami University about Neanderthal teeth and termite fishing. Adam consults handedness expert Prof Chris McManus from University College London. He's been trying to track down the genes responsible for whether we're right or left handed. And what about left-handed brains or eyes or molecules? Prof Andrea Sella explains handedness, or chirality, at the molecular scale and why when we consider Thalidomide, something seemingly so trivial can be extremely important. They also explore the left-handed brain. Some researchers point to a link between left-handedness and impairments like autism or dyslexia. Others claim that lefties are more creative and artistic. So what's the truth? The team consults Professors Sophie Scott, Chris McManus and Dorothy Bishop to find out. This episode is an updated version of two earlier broadcast episodes. If you have any Curious Cases for the team to investigate please email curiouscases@bbc.co.uk Producers: Fiona Roberts & Michelle Martin Presenter: Adam Rutherford & Hannah Fry A BBC Audio Science Unit production for BBC Radio 4, first broadcast in 2021.

The doctors continue their investigation into gravity, and answer Peter Fraser’s question: Is dark matter a proper theory or just a fudge to fit existing 'proper' theories to otherwise inexplicable observations? Whilst scientists are pretty convinced our understanding of gravity is largely correct, there are still some significant gaps. Namely, given the way galaxies are observed to behave, around 85% of the matter that they think should be in our universe is missing. So where – and, as importantly, what – is it? Cosmologist Andrew Pontzen introduces the evidence from our observations of the cosmic microwave background, light leftover from the Big Bang, which indicate that dark matter exists. However, this evidence alone is not enough for science. Physicist Chamkaur Ghag is trying to find particles of dark matter here on Earth. Unsurprisingly, no-one is quite sure where these critters are hiding in the particle zoo of protons, neutrons, electrons, quarks, bosons, muons and the rest – or even what they look like. One theory suggests a weakly interacting massive particle, or WIMP, may be the dark matter minibeast. Hundreds of thousands of these could be flying through our fingertips every second. To tell whether they’re there, Cham and hundreds of scientists are building detectors, huge vats of liquid xenon in underground caverns. Bond villain-esque lairs don’t come cheap, and listener Peter’s query is valid – what if dark matter goes the same way as the aether, an all-permeating (and ultimately non-existent) material that was hypothesised to carry light through the vacuum of space? Astrophysicist Katy Clough reiterates that experiments are the way to test predictions. Building a picture of how gravity works continues to take many people enormous effort, but this is the scientific process. Presenters: Hannah Fry & Adam Rutherford Producer: Jen Whyntie A BBC Audio Science Unit production for BBC Radio 4, first broadcast in 2021.

The doctors investigate a millennia-old query, as listener Emma in New Zealand asks: ‘How does gravity pull us?’ People have been thinking about how gravity works for a very long time. Way longer than when that particular apple almost certainly didn’t fall on the head of Isaac Newton. Cosmologist Andrew Pontzen begins guiding us through our journey by taking us back to the almost entirely incorrect writings of ancient Greeks. We then fast forward past Galileo and Newton, and throw in an extra dimension. Using an all-too-believable analogy where some merry cyclists suddenly ride into a meteor crater, astrophysicist Katy Clough tells us how Einstein’s spacetime works. Limitations of analogies accepted, this explains some of the observations that didn’t fit with Newton’s workings alone. But there are other snags with our understanding of gravity, both at the very small quantum scale and the very large galactic scale. Physicist Chamkaur Ghag introduces what scientists think may account for some of these issues: the mysterious dark matter. Presenters: Hannah Fry & Adam Rutherford Producer: Jen Whyntie A BBC Audio Science Unit production for BBC Radio 4, first broadcast in February 2019.

Do individuals perceive time differently? Psychologist and presenter of All in the Mind, Claudia Hammond wrote the book ‘Time Warped – Unlocking the Mysteries of Time Perception’. She explains how emotion and memory are big factors in how time is perceived. She stresses how time can stretch and squeeze depending on whether you are looking backwards or forwards. And she explains how lockdown has warped time in different ways for different people. Professor David Eagleman, from Baylor College of Medicine in Houston, conducted a very famous experiment on time dilation, to see whether time slows down when you are very frightened. He wanted to see whether people actually have increased time resolution during a terrifying moment, and tested whether his students actually see in slow motion when they leapt off a tall building (in a safe manner). Professor Marc Whitman is a neurologist who has spent his career looking for the clock in our brains. He says that time is dealt with in many parts of the brain, with some parts dealing with different durations, from milliseconds to decades. Katya Rubia is Professor of Cognitive Neuroscience at Kings College London and is an expert on time perception in children with ADHD. She links the impulsiveness of children with Attention Deficit Hyperactivity Disorder to problems with time perception and has found that the pre frontal lobe, which is key for perceiving time is both functionally and structurally different in children with the disorder, which means that time goes much slower for them. This goes some way to explain their impatience and inability to sit still. Producer: Fiona Roberts Presenters: Dr Hannah Fry and Dr Adam Rutherford A BBC Audio Science Unit Production for BBC Radio 4, first broadcast 2021.

The doctors put mosquitoes on trial, as listener Cathy in the UK asks, ‘What is the point of mosquitoes?’ in response to our show about wasps. Mosquitoes have undeniably played a role in killing millions of people. Malaria is the single biggest cause of death in human history. But Erica McAlister, senior curator of flies and fleas at the UK’s Natural History Museum, reveals that not all mosquitoes are interested in biting us for a blood meal, or are involved in transmitting disease. Only the females of about 10 species are the most problematic for humanity, from around 3600 true species of mosquito. Limited research indicates that many play important roles in ecosystems, for example as pollinators on land and as food sources during their larval stage in aquatic environments. Nonetheless, those roughly 10 species cause devastating disease. Kate Jones’ research at University College London examines the interface of ecology and human health. Malaria and dengue fever alone cause over 300 million infections annually. And there are many more diseases transmitted by mosquitoes: Zika, West Nile fever, Yellow fever, Japanese encephalitis – the list goes on, and with urbanisation and climate change, the picture is constantly changing. So what can be done? Should we try to annihilate the disease-carrying species? Insecticide use has historic and ongoing controversy, as the difficulties of needing to stop deaths in the short term risks longer term environmental damage, with unforeseen and possibly greater consequences for humanity. So Adam turns to new, genetic technology with zoologist Matthew Cobb. Can and should we modify mosquitoes to wipe themselves out, by wrecking local populations with sterile males, or use a technique called a gene drive to perpetuate debilitation through generations? Or could life find a way to evolve past our attempts at control, and cause greater problems? The doctors deliberate and try to decide a verdict on mosquitoes’ fate. Presenters: Hannah Fry & Adam Rutherford Producer: Jen Whyntie A BBC Audio Science Unit production for BBC Radio 4, first broadcast in 2021.

Astrology – could there be something to it? asks Dan from Australia. Rutherford and Fry investigate the science that has investigated astrology. Professor Richard Wiseman, (sceptical of all things paranormal and a Virgo) and Professor in the Public Understanding of Psychology at the University of Hertfordshire, explains the long history of the scientific investigation of astrology. He has also run his own experiments to test whether astrology can help you play the stock market and to investigate if people born in the summer are luckier than those born in the winter – the results may surprise you. Journalist and author, Jo Marchant (Leo and fascinated non-believer) has written all about the history of astrology in her new book – 'The Human Cosmos – A Secret History to the Stars'. In the beginning astrology and astronomy were one and the same. She explains how astrology flourished with the elite and ruling classes of ancient Babylon, Egypt and Greece. Data scientist, Alex Boxer (Taurus and cautious astrology tourist) explains that astrology may have been humanity's first attempt to predict the future with algorithms, something we’re doing more and more of now. In his book, ‘A scheme of heaven, astrology and the birth of science’, he describes how astrological and scientific algorithms are all just big data science looking for patterns. The issue lies in what that data is. Presenters: Hannah Fry (Pisces) & Adam Rutherford (Capricorn) Producer: Fiona Roberts (Libra) First broadcast on BBC Radio 4 in 2021.

Why do some people find noises like a fork scraping a plate so terrible? asks Findlay in Aberdeenshire. Rutherford and Fry endure some horrible noises to find out the answer. Warning - This episode contains some horrible sounds Trevor Cox, Professor of Acoustic Engineering at the University of Salford, has run experiments to find out the worst, most cringe-making sound. He divided horrible sounds into three categories: scraping sounds, like nails down a blackboard; disgusting sounds like a snotty sniffy nose; and sounds that make us cringe because of what we associate them with, like the dentist’s drill. All horrible sounds have some sort of association whether it’s a primal scream or fear of catching a disease, and they’re dealt with in the ancient part of the brain – the amygdala. Professor Tim Griffiths is a Cognitive Neurologist at Newcastle University’s Auditory Cognition Group. He has been studying people with misophonia, a condition where ordinary, everyday sounds, such as someone eating or breathing causes a severe anxiety and anger response. Misophonia may affect around 15% of the population and Tim thinks that different parts of the brain – the insula and the motor cortex - are involved in this fight or flight response to seemingly innocuous sounds. Cat Thomas’s job is to make horrible sounds. She is a foley artist at Boompost. If you watch Call the Midwife or Peaky Blinders, all the incidental sounds are created by Cat and her team. She also created some of the sounds for the horror film Camilla, which involved evisceration and disembowelling with the aid of some squishy oranges and bananas. Adam Rutherford and Hannah Fry try their own horror sounds when they chop off a finger with the aid of some large pasta shells, an orange and a knife. If you want more information on misophonia – http://www.misophonia-uk.org https://www.allergictosound.com Presenters: Hannah Fry & Adam Rutherford Producer: Fiona Roberts A BBC Audio Science Unit production for BBC Radio 4 first broadcast in January 2021.

Can I make a pizza that contains my recommended daily intake of everything? asks listener Paul in Manchester. We investigate whether a pizza can meet our full dietary requirements. The optimum diet for humans has been long contested. From William the Conqueror's alcohol diet to the infamous apple cider vinegar diet, discovering the healthiest nutrition is a centuries-long work in progress. So could The Pizza Diet be the next food fad? We investigate a theory that a basic margherita pizza – with its components of a flour-filled base, along with a cheese topping – should meet our needs for carbohydrate, protein and fat. Adam meets up with body-weight geneticist Giles Yeo from their respective kitchens for a remote cook-off to find out if it's possible to make this mythical one-meal wonder in practice. On closer inspection of the evidence-based government dietary requirements, this task appears somewhat challenging. Dietitian Clare Thornton-Wood analyses the components of a margherita and unsurprisingly finds they do not entirely meet the guidance. She then scrutinises our attempt to retrofit a recipe that might do the job. Giles attempts to put our proposed pizza into practice. He has to ad-lib, as the resultant mountain of eclectic toppings – chickpea and sweetcorn pizza, anyone? – and giant base won’t fit in his oven. Disappointingly for hardcore pizza fans like Paul who may be attempting healthier eating habits in 2021, it seems that this particular approach is not the way forward. Food choice psychologist Suzanna Forwood explains why there is so much more to our dietary decisions than digestive physiology, and offers tips for listeners hoping to make seasonal steps in a healthy direction. Presenters: Hannah Fry & Adam Rutherford Producer: Jen Whyntie A BBC Audio Science Unit production for BBC Radio 4 first broadcast in 2020.

"Why are some fungi helpful and others harmful?" asks Paul Glaister in Reading. Rutherford and Fry try to outdo each other with fungal top trumps to get to grips with the answer. Decomposition ecologist Lynne Boddy, Professor of Microbial Ecology at Cardiff University, helps Hannah calculate the amount of dead plant material we’d be buried in across the globe, if we didn’t have fungi to recycle it. And she describes her first fungal encounter in her student flat which was riddled with dry rot, and explains how without fungi, we wouldn’t have plants. On Adam’s team is Curator of Mycology, Dr. Bryn Dentiger, at the Natural History Museum of Utah. Bryn tells Adam that he can’t think of a single food that doesn’t have some association with fungus. And the links are mostly positive rather than just mould on the top of your jam or rotten fruit in your fridge. He introduces Adam to the Humungous Fungus – the biggest living organism on Earth - and they get excited at the prospect of 20,000 different fungal sexes. The pros and cons of fungi don’t stop there. Microbiologist Dr. Ada Hagan, in Michigan lists some of the fungal diseases we’re prone to, and the numerous drugs derived from fungi that help treat a whole host of common diseases. Presenters: Hannah Fry & Adam Rutherford Producer: Fiona Roberts A BBC Audio Science Unit production, first broadcast on BBC Radio 4 in 2020.

What would it take for humans to live permanently on Mars? asks Martin in Weston-super-Mare, UK. The doctors dig into requirements and possibilities of a long-term Martian outpost. We know that many missions to Mars have failed, for a range of reasons – malfunctions, crashes and even a mix-up between imperial and metric units. Getting to Mars – let alone decelerating from 30,000 miles per hour to a safe landing speed in about seven minutes – is not straightforward. Aerospace engineer Anita Sengupta helped land NASA’s Curiosity rover on Mars. She knows first-hand the challenges of putting a robot on the red planet. But getting robots to Mars is an easier proposition than doing the same for humans. Even if we work out how to survive the radiation exposure on the eight-month journey and the pulverising descent, Mars’ surface isn’t easily habitable. Principal investigator for NASA’s Mars Atmosphere and Volatile Evolution Mission (MAVEN) Bruce Jakosky describes the conditions on Mars: Freezing, with an atmosphere containing mostly carbon dioxide and very little water, and subject to annual global dust storms. However, this isn’t deterring space agencies and private companies from researching the challenge. The European Space Agency and Russian Institute for Biomedical Problems focussed on finding out the physiological and psychological tolls by selecting six candidates to spend 520 days in a simulated spacecraft and landing module. Diego Urbina explains the personal challenge of taking part in the Mars500 experiment. Some private company owners have gone even further. As well as making technology based on the current physical conditions, could those constraints themselves be altered? Could Mars be terraformed, or warmed, for easier human survival? Bruce Jakosky shares just what that would take – and compares these requirements with what’s actually available. Presenters: Hannah Fry & Adam Rutherford Producer: Jen Whyntie A BBC Audio Science Unit production, first broadcast on BBC Radio 4 in 2020.

"How many hamsters on wheels would it take to power London?" asks Judah from Virginia in the USA. Rutherford & Fry return with engineering, ethics and economics to answer this electric query. Smart grid engineer Lynne McDonald helps keep the lights on for 8.3 million homes and businesses across London at UK Power Networks. She explains how the kilowatt hours we see on our electricity bills relate to the thousands of gigawatt hours required when thinking about powering the whole of London. In theory, a hamster in a wheel might be able to produce about half a watt of power – enough to run a small LED light bulb. Whilst the doctors argue the case on the resultant practicalities and ethics of even considering such a scenario – as, for example, the required cubic kilometre stack of hamster habitats would cover Canary Wharf – Royal Veterinary College researcher Zoe Davies points out some biological and anatomical home truths. As an expert in biomechanics currently investigating athletic performance in racehorses, she walks Adam through the impossibilities of using pretty much any animal, bird or insect as a source of power. There may be one exception though: humans. Veteran lecturer of undergraduate chemistry for biologists and cycling enthusiast, Andrea Sella discusses whether human power might realistically work. We consider what this or other more realistic sources of renewable energy could mean for the future of our national grid. Presenters: Hannah Fry & Adam Rutherford Producer: Jen Whyntie A BBC Audio Science Unit production for BBC Radio 4, first broadcast in December 2020.

Rutherford and Fry are back in the business of solving your science queries and rooting out the quirks and conundrums of everything that is science!

Is there a point in space where the Sun could heat a burrito perfectly? asks Will. The doctors tackle this and a plethora of other conundrums from the Curious Cases inbox. Featuring expert answers from: Astrophysicist Samaya Nissanke Cosmologist Andrew Pontzen Cognitive neuroscientist Sophie Scott Presenters: Hannah Fry & Adam Rutherford Producer: Jen Whyntie First broadcast on BBC Radio 4 in July 2020.

‘Today I learnt that tigons and ligers are what you get when lions and tigers interbreed?!’ surprised listener Jamz G tells the doctors. ‘What determines whether species can interbreed?’ Geneticist Aoife McLysaght studies molecular evolution. She explains the modern definition of a species, built on ideas from Aristotle, Linnaeus and Darwin: a species is a group of organisms capable of interbreeding to produce fertile offspring. Hybrids – such as ligons and tigers – are usually infertile, because their common ancestors long ago diverged into the lions and tigers we know today. However, this definition isn’t absolute, and there are many ways a new species can be formed. Hybrids also offer rich study subjects for scientists. Mathematical biologist Kit Yates discusses why he’s been reading research papers about hebras and zorses (horse x zebra) as their patterns offer insights into how cells spread and develop into organisms, building on a prediction made by codebreaking mathematician Alan Turing. And it turns out that these hybrids are even more intriguing. As speciation and evolution expert Joana Meier explains, hybrids are not always infertile. Hybridisation can lead to successful new species arising, such as in Lake Victoria’s cichlid fish, who it seems have been having a wild evolutionary party for the last 15,000 years. And the picture gets even murkier when we discover that modern genetics reveals our human ancestors successfully mated with Neanderthals. Presenters: Hannah Fry & Adam Rutherford Producer: Jen Whyntie First broadcast on BBC Radio 4 in July 2020.

Everyone knows about the Big Bang being the beginning of the universe and time - but when and how is it going to end? ask brothers Raffie and Xe from Rome. For this series, with lockdown learning in mind, Drs Rutherford and Fry are investigating scientific mysteries for students of all ages. The doctors sift science from philosophy to find out. Cosmologist Jo Dunkley studies the origins and evolution of the universe. She explains how astrophysical ideas and techniques have evolved to tell us what we now know about our galaxy and far beyond, from the elegant parallax technique to standard candles. This particular distance measure, which uses stars of a known brightness to work out how far away other objects in the universe are, was discovered by American astronomer Henrietta Swan Leavitt in 1912, who worked at the Harvard University as one of several “computers” – women who processed and calculated data and made significant contributions to astronomy. Curious Cases’ universal guru Andrew Pontzen puts this into context. Because the universe is so enormous, it turns out that these measurements are just the first steps on the cosmic distance ladder – a suite of tools that astrophysicists use to determine distances to celestial objects. Scientists know that objects are moving away from us because the wavelengths of light from them get stretched and appear redder in our telescopes – the so-called red shift effect. But having a handle on the distances to and between those objects allows cosmologists to monitor what’s happening to them over time. And it turns out that not only are they getting further apart, indicating that the universe is expanding, but that this process is accelerating. So what might happen in the end? Expansion and then collapse – a big crunch? Expansion into the void – a big freeze, or a big rip? Or what if there is more than one universe – might a new one bubble up with totally different laws of physics that would cause our own to cease existing? It turns out that when dealing with predictions for something involving infinite space and time, the possibilities are largely limited by human imagination alone. Ideas are where science starts, but experiments are required to build evidence confirming or rejecting them as fact. The doctors discuss how gravitational wave detectors and quantum computers might one day provide this. Presenters: Hannah Fry & Adam Rutherford Producer: Jen Whyntie First broadcast on BBC Radio 4 in June 2020.

"What’s the point of wasps?" asks listener Andrew, who is fed up with being pestered. For this series, with lockdown learning in mind, Drs Rutherford and Fry are investigating scientific mysteries for students of all ages. Do wasps do anything to justify their presence as a picnic menace? Ecologist Seirian Sumner researches social wasp behaviour and champions their existence. Not only do yellow jacket wasps perform important ecological services as generalist pest controllers of aphids, caterpillars and flies in the UK, they have complex societies and may even perform pollination services, making them more like their better-loved bee cousins than many might think. However, much remains unknown about wasps’ contribution to our ecosystem. Seirian works with entomologist Adam Hart, and together they run The Big Wasp Survey each summer, a citizen science project dedicated to find out more about UK wasp species and their populations. Prof. Hart sets up an experimental picnic with Dr Rutherford to try and attract some native wasps, and discusses why they are so maligned. But in some parts of the world UK wasp species have become a major problem. Just after World War II, having unwittingly chosen some aircraft parts destined for New Zealand as their overwintering home, some wasp queens woke up in the city of Hamilton. With no natural predators or competitors, they quickly established a growing population. Fast forward to today, and by late summer the biomass of wasps becomes greater than all the birds, rodents and stoats in the southern island’s honeydew beech forests. Multiyear nests have been discovered that are over three metres tall and contain millions of wasps. Researcher Bob Brown is digging into wasp nests back in the UK to discover which species keep wasps in check here, and whether they might work as biological control. This causes the doctors to ponder the problems of humans moving species around the planet. Accidental or even well-meaning introductions all too often become invasive. As climate change and urbanisation accelerate, wasps may become more helpful in some ways and more harmful in others. Presenters: Hannah Fry, Adam Rutherford Producer: Jen Whyntie First broadcast on BBC Radio 4 in 2020.

"Could you make a machine to make it rain in minutes?" asks listener Alexander from Hampshire, aged 12. For this series, with lockdown learning in mind, Drs Rutherford and Fry are investigating scientific mysteries for students of all ages. Rutherford and Fry dive into the clouded story of weather modification. First, we need to decide where and when we might deploy any rain machine. Liz Bentley, Chief Executive of the Royal Meteorological society, takes us through the science, maths and art of predicting the weather. Hannah heads down to the BBC Weather Centre to meet meteorologist Helen Willetts, who takes us through the highs and lows of forecasting. And then for the technology itself. Mark Miodownik, scientist and author of Liquid: The Delightful and Dangerous Substances The Flow Through Our Lives, reveals that a technique called cloud seeding has almost certainly been tried in different places around the world for decades. But, whilst it’s supposed to induce showers and even clear the way for sunny spells, the results aren’t always reliable. And even if we can make it rain, Liz explains why messing with the weather may be at our peril. Presenters: Hannah Fry, Adam Rutherford Producer: Jen Whyntie First broadcast on BBC Radio 4 in 2020.

"Why do our tummies rumble - and when they do, does it always mean we are hungry?" asks listener James, aged 12. For this series, with lockdown learning in mind, Drs Rutherford and Fry are investigating scientific mysteries for students of all ages. To get to the bottom of this noisy problem, the doctors tune in to our guts. Geneticist Giles Yeo studies food intake and obesity. He explains the wavy workings of our digestive system, and how those audible rumbles are a sign that digestion is taking place – a phenomenon thought to be onomatopoeically named 'borborygmi' by the ancient Greeks, and explored further in the gruesome 19th century experiments of surgeon William Beaumont. However, tuning in to the gut’s sounds can tell us more than whether we need a snack. Family doctor Margaret McCartney takes us through the process of how and why she and her medical colleagues may use a stethoscope to listen to your abdomen for both particular noises and silence. Microbiologist Barry Marshall has taken medical listening one step further in his Noisy Guts Project. Inspired by microphones used to listen for termites hiding in walls, the Nobel Prize-winning scientist is trialling an acoustic belt, which could be worn to help diagnose and treat Irritable Bowel Syndrome. Presenters: Hannah Fry, Adam Rutherford Producer: Jen Whyntie First broadcast on BBC Radio 4 in 2020.

Rutherford & Fry are back with longer duration episodes brought to you from slightly shouty socially distanced studio and bedroom settings.

"What are wormholes and do they really exist?" asks Manlee-Fidel Spence, aged 12. In this exotic episode, the doctors investigate how wormholes would work. Cosmologist Andrew Pontzen explains why wormholes could allow you to travel through time as well as space. And physicist Jim AlKhalili outlines the infinite problems this could generate. When it comes to wormholes and time travel, many science fiction stories have married solid science and successful storytelling, as Jennifer Oullette describes, but others really have defied the laws of physics. Jim also reveals why some quantum physicists now think that wormholes could be everywhere. But don't expect to jump back to 1955 any time soon. Presenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin First broadcast on BBC Radio 4 in 2020.

Two cold callers feature in this episode. Jennifer Langston from Ontario in Canada sent this message to curiouscases@bbc.co.uk: "My husband has just taken up cold water swimming and he'll swim in temperatures as low as 6 degrees Celsius. I worry that it's too cold for him, but he claims that 'swimming in cold water is good for you', which drives me bonkers. Can you tell us if there is any scientific proof behind this?” Adam takes a trip to his local lido and asks the locals why they get a kick out of a chilly winter dip. Meanwhile, Hannah calls the Antarctic to talk to meteorologist Richard Warren about the perils of a frozen beard. Our second cold caller, Sarah Dudley, asks why women get cold feet in bed. Thermal physiologist Heather Massey is on hand with the answer. But when it comes to the natural world, other animals are masters of sub-zero living. Frozen Planet producer Kathryn Jeffs, from the BBC's Natural History Unit, explains why polar bears are perfectly designed for the Arctic. And we discover why Paddington Bear is better suited to Peru. Presenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin First broadcast on BBC Radio 4 in 2020.

“I suppose a cold is called a cold because we catch it in the winter," writes Alison Evans from St Albans. "But why is it that we get more colds in winter than in the summer?” This week's Cold Case is all about the common cold, a set of symptoms caused by hundreds of different strains of cold and flu viruses. Adam uncovers the stinky history of infectious disease with medical historian Claire Jones. Virologists Jonathan Ball and Wendy Barclay describe how spiky viruses lock on to our cells, but why many of the symptoms of a common cold are due to our own body's overreaction. Plus, we delve into the science of sneezing with nose doctor Carl Philpott. Presenters: Adam Rutherford, Hannah Fry Producer: Michelle Martin

"My question is about something I became aware of at a young age," explains Samantha Richter from Cambridgeshire. "I was sitting on the carpet at school, being read a story by the teacher. My hair felt as though it was standing on end as waves of a tingly sensation washed over my head. I subsequently found certain scenes in films had this effect, when actors were talking softly, or someone was having their hair brushed." "Then, a few years ago, I discovered that there is a name for the tingles, it's called ASMR. My question is, what is ASMR, and why do we experience it?" In this episode, we explore the world of Autonomous Sensory Meridian Response. It's a trend which has risen quickly on YouTube, with devoted subscribers following their favourite 'ASMRtists' whose videos receive millions of plays. Hannah speaks to Dr Nick Davis, who published the very first research paper on the phenomenon in 2015. And Adam is put to the test by Dr Giulia Poerio, to see if he is susceptible to the sensation of ASMR. Are there any proven benefits for devoted fans, or is it just a YouTube fad? We've concocted our very own Curious recordings so you can find out if your brain begins to tingle. You'll find them in our normal podstream, where you can enjoy Adam and Hannah crafting a very ASMRy cocktail for your listening pleasure. Presenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin First broadcast on BBC Radio 4 in 2020.

Adam Rutherford concocts an Old Fashioned. First listen to our episode on ASMR, then grab some headphones and let Adam mix you a cocktail. Let us know if it gives you the brain tingles, or any other kind of reaction, by emailing curiouscases@bbc.co.uk.

Hannah Fry mixes a mojito. This ASMR recording accompanies the episode of The Curious Cases of Rutherford and Fry on the science of ASMR. Listen to that first, then grab some headphones and let us know if it gives you the brain tingles by emailing curiouscases@bbc.co.uk.

Two questions about love and heartbreak in this episode for our Valentine's special edition. Jessica Glasco, aged 29, wrote in to ask about the power of love and how it affects our brain. Hannah tracks down Dr Helen Fisher, who conducted some of the first MRI studies on love by putting besotted couples into the brain scanner. Adam talks to broadcaster Claudia Hammond, author of Emotional Rollercoaster, to find out how psychologists have grappled with the messy business of love. And we hear why a small furry vole was thought to hold the answer to the mystery of monogamy. Our second question concerns the pain of heartbreak - why does our heart ache? Can emotional hurt cause physical pain? On call is our very own agony aunt, Irene Tracey, Prof of Pain Research. Presenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin First broadcast on BBC Radio 4 in 2020.

"How do you make gold?" asks curious listener, Paul Ruddick. Inspired by the promise of riches, Hannah and Adam embark on a mission to discover the origin of gold. It's a tale that takes them from the clandestine codes of Aristotle to the alchemy of Isaac Newton, alongside materials scientist Mark Miodownik. They boldly go into the cosmos with astronomers Lucie Green and Andrew Pontzen, to learn what happens in the most exotic areas of space. By the end one thing is for sure - you'll never look at your gold jewellery in quite the same way again. Presenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin First broadcast on BBC Radio 4 in 2020.

Rutherford & Fry reveal which of your questions they’ve chosen for Series 15. Plus they select more of their favourite strange-but-true science papers, including how to use mathematics to challenge a parking fine and training tortoises to yawn.

"What would become the dominant species if, or when, humans go extinct?" This cheery question leads Drs Rutherford and Fry to embark on an evolutionary thought experiment. Zoologist Matthew Cobb questions whether humans really are the dominant species. Ecologist Kate Jones explains why some species are more extinction-prone than others. Plus Phil Plait, AKA The Bad Astronomer, busts some myths about why the dinosaurs went extinct. Send your questions for future series, along with any Curio correspondence for the podcast, to: curiouscases@bbc.co.uk Presenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin First broadcast on BBC Radio 4 in 2019.

"Why is it so difficult to predict the weather?" asks Isabella Webber, aged 21 from Vienna. "I am sure there are many intelligent meteorologists and it seems rather straight forward to calculate wind speed, look at the clouds, and data from the past to make accurate predictions, but yet it’s not possible." Adam delves into the history of forecasting with author Andrew Blum, beginning with the mystery of a lost hot air balloon full of Arctic explorers. Hannah visits the BBC Weather Centre to talk to meteorologist and presenter Helen Willetts about how forecasting has changed, and whether people get annoyed at her if she gets the forecast wrong. Plus mathematician Steven Strogatz suggests a chaotic explanation as to why we can't produce the perfect forecast. Presenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin First broadcast on BBC Radio 4 in 2019.

"How do you make antimatter?' asks Scott Matheson, aged 21 from Utah. The team takes charge of this question with a spin through the history of antimatter. Adam talks to physicist Frank Close, author of 'Antimatter', about its origins in the equations of Dirac to its manufacture in the first particle accelerator, the Bevatron. Cosmologist Andrew Pontzen tells Hannah why physicists today are busy pondering the mystery of the missing antimatter. Anyone who discovers why the Universe is made of matter, rather than antimatter, is in line for the Nobel Prize. Plus, neuroscientist Sophie Scott describes how antimatter has been put to good use down here on Earth to peer into people's brains. Presenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin First broadcast on BBC Radio 4 in 2019.

Stephen Fry (no relation) asks Adam and Hannah to investigate the following question: "All my life I have been mildly plagued by the fact that I have a quite appalling ability to remember faces. I cut people I should know well dead in the street, or at least fail to recognise them in a way which must often be hurtful. At a party I can talk to someone for ten minutes and then see them again twenty later and have no idea who they are unless I’ve made an effort to fix some accessory or item of their dress in my mind. If I see them the next day in another context I’ll have no idea who they are. It’s distressing for me in as much as I hate the idea that people might think I am blanking them, or think little of them, don’t consider them significant and so forth. I’d be very grateful if my sister-in-surname and her eximious partner Adam could investigate prosopagnosia for me and offer any hint add to as to its cause or even possible – I won’t say “cure” as I am sure it’s chronic and untreatable – but at least any interesting ways of relieving it." Hannah and Adam call in the experts, neuroscientists Sophie Scott and Brad Duchaine. Why is it that some people struggle with prosopagnosia, whilst others never forget a face? You can find out more about Face Blindness, who it affects and how to cope with it by visiting www.faceblind.org.uk/ Presenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin First broadcast on BBC Radio 4 in 2019.

Rutherford and Fry delve into the history of roller coasters in the second instalment of their investigation into why we enjoy being scared. Amelie Xenakis asks: "Why do people enjoy rollercoasters? I am a thrill-seeker and I am always terrified before riding a roller coaster but I enjoy the ride itself. (I would like BOTH of you to ride a roller coaster if possible)." Never ones to shy away from a challenge, the pair attempt to channel their inner adrenaline junkies with a trip on one the UK's scariest rollercoasters at Thorpe Park. They discover the birth of the roller coaster in the 18th century, when Catherine the Great enjoyed careering down Russian Ice Mountains covered in snow. Adam talks to scary sociologist Margee Kerr, author of 'Scream! The Science of Fear', about how the modern roller coaster evolved. David Poeppel from New York University studies the science of screaming, and we discover what makes screams uniquely terrifying. Plus, psychologist and broadcaster Claudia Hammond describes some early experiments which tested how fear affects our body. Presenters: Adam Rutherford, Hannah Fry Producer: Michelle Martin First broadcast on BBC Radio 4 in 2019.

It was a dark and stormy night around the time of Halloween. A secret message arrived addressed to Rutherford & Fry from a mysterious woman called Heidi Daugh, who demanded to know: "Why do people like to be scared? For example, going on scary amusement park rides and watching horror movies that make you jump.” What followed was an investigation over two chapters, which would test our intrepid duo to their very limits. In this first instalment, they explore the history of horror, starting with its literary origins in the Gothic fiction classic 'The Castle of Otranto'. Adam challenges Hannah to watch a horror film without hiding behind a cushion. She quizzes horror scholar Mathias Clasen to find out why some people love the feeling of terror, whilst it leaves other cold. Sociologist Margee Kerr and psychologist Claudia Hammond are also on hand to explore why scary movies are so powerful and popular. Presenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin FIrst broadcast on BBC Radio 4 in 2019.

Rutherford and Fry are back with Series 14. In an extended podcast trailer they discuss their favourite strange-but-true scientific studies, from jetlagged hamsters to flatulent snakes. Presenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin

"Is there is any way of knowing what noises, if any, dinosaurs would have made?" asks Freddie Quinn, aged 8 from Cambridge in New Zealand. From Jurassic Park to Walking with Dinosaurs, the roars of gigantic dinosaurs like T.Rex are designed to evoke fear and terror. But did dinosaurs actually roar? And how do paleontologists investigate what noises these extinct animals may have produced? Hannah and Adam talk to dinosaur experts Steve Brusatte and Julia Clarke to find out. Plus Jurassic World sound designer Al Nelson reveals the strange sounds they used as dinosaur noises in their Hollywood blockbusters. Presenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin First broadcast on BBC Radio 4 in 2019.

In the second installment of our double episode on the Moon we ask what life would be like if we had more than one Moon. From the tides to the seasons, the Moon shapes our world in ways that often go unnoticed. And, as we'll find out, it played a vital role in the creation of life itself. This week we celebrate the many ways the Moon and the Earth are linked. If one Moon is so great, why not have two? We discover why multiple moons could spell disaster for our planet, from giant volcanoes to cataclysmic collisions. Featuring astronomer Brendan Owens from the Royal Observatory Greenwich and physicist Neil Comins, author of 'What if the Earth had two Moons?' Presenters: Adam Rutherford, Hannah Fry Producer: Michelle Martin First broadcast on BBC Radio 4 in 2019.

A double episode to mark the 50th anniversary of Apollo 11, and the first humans to walk on the Moon in 1969. Harley Day emailed curiouscases@bbc.co.uk to ask “Why do we only have one Moon and what would life on Earth be like if we had more? I'll be over the moon if you can help me solve this mystery.” In this first episode, Hannah and Adam look at how the Moon was formed and why we only have one. Featuring Maggie Aderin-Pocock space scientist and author of 'The Book of the Moon' and cosmic mineralogist Sara Russell from the Natural History Museum. Presenters: Adam Rutherford, Hannah Fry Producer: Michelle Martin First broadcast on BBC Radio 4 in 2019.

“We play many musical instruments in our family. Lots of them produce the same pitch of notes, but the instruments all sound different. Why is this?” asks Natasha Cook aged 11, and her Dad Jeremy from Guelph in Ontario, Canada. For this instrumental case Hannah and Adam are joined by the Curious Cases band - Matt Chandler and Wayne Urquhart - to play with today's question. Bringing the science we have acoustic engineer and saxophone player Trevor Cox. Plus materials expert Zoe Laughlin demonstrates a selection of her unusual musical creations, including a lead bugle. Presenters: Adam Rutherford, Hannah Fry Producer: Michelle Martin First broadcast on BBC Radio 4 in 2019.

"Will the periodic table ever be complete?" asks Philip Craven on Twitter. In 2016 four new chemical elements were given the official stamp of approval - nihonium, moscovium, tennessine, and oganesson. And 2019 was named by the UN as the International Year of the Periodic Table. In this episode, Hannah and Adam dive into the test tubes of history to hear why the first element was discovered in boiled urine, why chips don't explode and how a cancelled trip to a cheese factory resulted in the creation of the periodic table. We'll hear from Dawn Shaughnessy from Lawrence Livermore National Lab, part of the team that discovered the latest 'superheavy' elements. Science writer Philip Ball shows Adam around Humphry Davy's lab equipment at the Royal Institution of Great Britain and Jim Al-Khalili explains why scientists are eager to reach the Island of Stability. Presenters: Adam Rutherford, Hannah Fry Producer: Michelle Martin First broadcast on BBC Radio 4 in April 2019.

“Is hypnosis real, and if so how does it work? Does it have any practical uses and which of Hannah and Adam is most susceptible?” This question came from two Curios, Peter Jordan aged 24 from Manchester and Arran Kinnear aged 13 from Bristol. Arch sceptics Hannah and Adam visit stage hypnotist Ben Dali to find out if they are susceptible to the power of suggestion. One of them will be successfully hypnotised, but who will it be? Along the way we hear about the history of hypnosis from Wendy Moore author of 'The Mesmerist'. Plus psychologist Devin Terhune explains what we know about the science of hypnosis today. Presenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin First broadcast on BBC Radio 4 in 2019.

Hannah and Adam return to crack open the Curious Cases they’ll be examining during the coming series, from the sound of musical instruments to the science of hypnosis. Please send your questions for future episodes and entries for Curio of the Week to: curiouscases@bbc.co.uk. Presenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin

"My name is Ava and I've never had a hangover," writes Ava Karuso. "I'm a 25 year-old Australian and I enjoy going out for drinks. However, the next day when everyone else sleeps in and licks their wounds, I get up early and get right back to my normal routine.” Drs Rutherford and Fry investigate the ancient origins of alcohol, from Sumerians drinking beer through straws, to Aristotle's teachings ‘On Intoxication’. But what can modern science tell us about how alcohol affects our brains? What causes the morning-after hangover and do some drinks make you feel worse than others? Are there any hangover cures that have been scientifically validated? Featuring health psychologist and hangover researcher Sally Adams, chemist Andrea Sella and science writer Adam Rogers, author of 'Proof: The Science of Booze'. Presenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin First broadcast on BBC Radio 4 in 2018.

“Why does bad food taste so good?” asks Alan Fouracre from Tauranga, New Zealand. "And by ‘bad’ food, I mean the things we are told to hold back on like sausage, chips and chocolate." From sugar to salt and fat, we investigate why our body derives pleasure from the very foods we're often told to avoid. Adam discovers why retronasal smelling makes bacon taste delicious on a trip to the BBC canteen with materials scientist, Mark Miodownik. Hannah consults food scientist Linda Bartoshuk on her fizzy pop habit. Plus The Angry Chef, Anthony Warner, discusses the dangers of labeling certain foods as 'bad'. Presenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin First broadcast on BBC Radio 4 in 2018.

In the second part of our eternal quest to investigate infinity, inspired by this question from father and son duo Sorley and Tom Watson from Edinburgh: “Is anything in the Universe truly infinite, or is infinity something that only exists in mathematics?” Hannah and Adam try and find something that is truly infinite, from the infinitely small particles that live in the subatomic world to the infinitely dense heart of a black hole. But how about the Universe itself? We find out how physicists go about measuring the shape of the Universe, with the help of an orange and a game of Asteroids. Plus, we consider the possibility that the Universe might be finite and have an edge. If so, what's on the other side? Theoretical physicist Sean Carroll from Caltech and cosmologist Andrew Pontzen from University College London help us navigate our biggest question yet. Presenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin First broadcast on BBC Radio 4 in 2018.

“Is anything in the Universe truly infinite, or is infinity something that only exists in mathematics?” This momentous question came from father and son duo from Edinburgh Sorley aged 10 and Tom, aged adult. It's a subject so big, that we've devoted two episodes to our never-ending quest to investigate infinity. The first installment is a story of mathematics, music and murder. We'll find out why the ancient Pythagoreans decided that infinity was evil, and why some infinities are bigger than others. Featuring the marvellous mathematical minds of Steven Strogatz from the Cornell University and Eugenia Cheng, author of 'Beyond Infinity'. Presenters: Adam Rutherford, Hannah Fry Producer: Michelle Martin First broadcast on BBC Radio 4 in December 2018.

"How do accents start and where did they come from?” asks Sachin Bahal from Toronto in Canada. Hannah is schooled in speaking Geordie by top accent coach Marina Tyndall. And Adam talks to author and acoustics expert Trevor Cox about how accents evolved and why they persist. We meet Debie who has Foreign Accent Syndrome - an extremely rare condition in which your accent can change overnight. After a severe bout of flu, which got progressively worse, Debie's Brummie accent suddenly transformed into something distinctively more European. If you have any more Curious Cases for the team to solve, please send them in for consideration: curiouscases@bbc.co.uk Presenters: Adam Rutherford, Hannah Fry Producer: Michelle Martin First broadcast on BBC Radio 4 in November 2018.

"Is it true all British people can trace their ancestry to Vikings and how do ancestry DNA tests work?" asks Chloe Mann from Worthing. Genetic ancestry tests promise to reveal your ancestral origins and map your global heritage, but do they? Rutherford and Fry are here to bust some myths. Adam takes a trip through Norse history with Viking historian Janina Ramirez, whilst flying over the Medieval town of Ludwig. Meanwhile Hannah discovers how DNA ancestry tests work with evolutionary geneticist Mark Thomas, including why most of us can rightly reclaim our royal lineage. If you have any more Curious Cases for the team to solve, please send them in for consideration: curiouscases@bbc.co.uk Presenters: Adam Rutherford, Hannah Fry Producer: Michelle Martin First broadcast on BBC Radio 4 in November 2018.

"Why do people experience pain differently when they go through the same event?" asks Claire Jenkins from Cwmbran in Wales. Professor of Pain Research, Irene Tracey, welcomes Adam in to the room she calls her 'Torture Chamber'. Burning, electrocuting, lasering and piercing are all on the menu, but which will hurt the most? Hannah speaks to Steve Pete from Washington who has a rare genetic condition which means he doesn't feel pain. For chronic sufferers, this sounds like heaven, but a life without pain has brought untold suffering to him and his family, including the tragic story of his brother, Chris. We look at how the body creates pain, why some people feel it more than others, and how this knowledge could help scientists treat pain more effectively in the future. Presenters: Adam Rutherford, Hannah Fry Producer: Michelle Martin.

Two random questions in this episode. "Is anything truly random, or is everything predetermined?" asks Darren Spalding from Market Harborough. Hannah and Adam go in search of random events, from dice throws to lava lamps. Can we predict the outcome of any event? And "how do computers manage to pick random numbers?", asks Jim Rennie from Mackinaw in Illinois. Joining them are a random selection of experts: mathematician Colva Roney-Dougal, technology journalist Bill Thompson, Science Museum Curator Tilly Blyth and quantum physicist Jim AlKhalili. Presenters: Adam Rutherford, Hannah Fry Producer: Michelle Martin.

"How fast can a human run and would we be faster as quadrapeds?" This question flew in via Twitter from historian Greg Jenner. Is there a limit to human sprinting performance? In this episode we investigate the biomechanics of running, statistical trends in human performance and which kind of monkey runs the fastest. But first, an experiment. Due to some spurious and possibly fictional injuries, neither Hannah nor Adam are fit enough to take part in a sprint trial at the University of Bath. So long-suffering Producer Michelle steps up to the challenge and into the starting blocks. Not known for her love of athletics, or exercise of any sort, how will she fair in the ultimate speed test? Biomechanist Peter Weyand from Texas discusses the role of different muscle types in speed versus endurance. Sports scientist Polly McGuigan reveals why Usain Lightning Bolt is still the fastest man in the world. And Prof of Sports Engineering Steve Haake reveals how fast a man can run like a monkey. Presenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin.

Do alien civilisations exist? When will ET phone home? In the second part of our alien double bill, Hannah and Adam boldly go in search of intelligence. They may be some time. What will aliens look like? Where should we look for them? And what are the chances of finding complex life in the cosmos? Featuring astronomer Seth Shostak from the SETI Institute in California, exoplanet hunter Sara Rugheimer from the University of St Andrews and zoologist Matthew Cobb from Manchester University, Presenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin.

Mike Holcombe from Largs in Scotland asks, "How do we look for alien life and what are we expecting to find?" In the first of two episodes on the search for ET, Hannah and Adam look for life inside the Solar System. How do we define life and why we obsessed with finding it on Mars? Or should we be looking for space squid on Europa instead? Features interviews with planetary scientist Monica Grady from the Open University, senior astronomer Seth Shostak from SETI and zoologist Matthew Cobb from the University of Manchester. Send your Curious Cases for consideration in to curiouscases@bbc.co.uk Presenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin.

"Winter is finally over and the birds are all singing their hearts out at dawn. What's all the noise about? And why are some songs so elaborate?" asks Tony Fulford from Ely in Cambridgeshire. We find out how birds produce multiple notes at once, which one has the widest repertoire of songs, and why males like to show off quite so much. Plus, we talk to researcher Lauryn Benedict about the project which aims to solve the mystery of why female birds sing - www.femalebirdsong.org. Featuring interviews with RSPB President and nature presenter Miranda Krestovnikoff, and world-renowned birdsong expert and sound recordist, Don Kroodsma. Archive of 'singing like a wren' courtesy of The One Show, BBC TV. Send your cases for consideration to curiouscases@bbc.co.uk. Presenters: Adam Rutherford, Hannah Fry Producer: Michelle Martin.

"My boss insists that if you choose the same numbers in the lottery each time your probability of winning will increase. Is this true?" asks Vince Scott from Edinburgh. National lotteries are played in more than 80 countries worldwide, but can you increase your chances of winning? Hannah consults statistician Jen Rogers to discover the best way to select your lucky numbers. Adam talks chance and luck with David Spiegelhalter and hears how the field of probability began with a philandering gambling polymath in 16th century Italy. Plus, we meet the Oxford professor who tried to beat the house in a Las Vegas casino, using a computer concealed inside his shoe. Presenters: Adam Rutherford, Hannah Fry Producer: Michelle Martin.

"Do we know what causes déjà vu?" asks Floyd Kitchen from Queenstown in New Zealand. Drs Rutherford and Fry investigate this familiar feeling by speaking to world-leading reseacher Chris Moulin from the University of Grenoble in France and memory expert Catherine Loveday from Westminster University. Plus, they find out why early investigations classed déjà vu as a type of paranormal phenomenon. For most of us, it's a fleetingly strange experience, but for some people it can become a serious problem. Lisa from Hulme in Manchester started experiencing déjà vu when she was 22 with episodes that could last all day. The origin of her déjà vu has been the key to helping psychologists investigate its cause. Presenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin.

"What happens to the human voice as we age? If I hear a voice on the radio, I can guess roughly how old they are. But singer's voices seem to stay relatively unchanged as they age. Why is this?" All these questions were sent to curiouscases@bbc.co.uk by Jonathan Crain from Long Island in New York. The Doctors discover how the human voice is produced and listen to how our voice sounds when it emerges from our vocal cords. Acoustic engineer Trevor Cox, author of 'Now You're Talking', explains why German and French babies have a different accent. And neuroscientist Sophie Scott describes what happens when boys' voices break, and why a similar thing can happen to women during the menopause. Finally, our voices often change dramatically in later life, as demonstrated by impressionist Duncan Wisbey from Radio 4's Dead Ringers. Expect cameos from David Attenborough, Dumbledore and Paul McCartney. Presenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin.

"What is the fifth dimension?" asks Lena Komaier-Peeters from East Sussex. Proving the existence of extra dimensions, beyond our 3D universe, is one of the most exciting and controversial areas in modern physics. Hannah and Adam head to CERN, the scientific cathedral for quantum weirdness, to try and find them. Theoretical physicist Rakhi Mahbubani explains why we think that dimensions beyond our own might exist. Adam meets Sam Harper, who has spent 14 years hunting for an elusive particle called the 'graviton', which could provide a portal to these extra dimensions. But if they exist, where have these extra dimensions been hiding? Sean Carroll from Caltech explains various ideas that have been dreamt up by physicists, from minuscule hidden planes to gigantic parallel worlds. Producer: Michelle Martin Presenters: Hannah Fry, Adam Rutherford.

"How do we measure the age of the Universe?" asks Simon Whitehead. A hundred years ago this wouldn't even have been considered a valid question, because we didn't think the Universe had a beginning at all. Even Einstein thought that space was eternal and unchanging. This is the tale of how we discovered that the Universe had a beginning, and why calculating its age has been one of the greatest challenges in modern astronomy. We also uncover the mysterious dark energy that pervades the cosmos and discover why it's been putting a scientific spanner in the works. Helping to unravel today's question are physicists Andrew Pontzen, Jo Dunkley and Jim Al-Khalili. Presenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin.

"What makes things sharp? Why are thinner knives sharper? What happens on the molecular level when you cut something?" All these questions came from Joshua Schwartz in New York City. The ability to create sharp tools allowed us to fashion clothing, make shelters and hunt for food, all essential for the development of human civilisation, according to materials scientist Mark Miodownik. We hear from IBM scientist Chris Lutz, who has used one of the sharpest blades in the world to slice up individual atoms. Plus palaeoarchaeologist Becky Wragg Sykes reveals the sharpest natural object in the world, a volcanic glass used by the Aztecs called obsidian. Presenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin.

"What is the tiniest dinosaur?" asks younger listener Ellie Cook, aged 11. Today's hunt takes us from the discovery of dinosaurs right up to the present day, which is being hailed as a 'golden age' for palaeontology. One new species of dinosaur is currently being unearthed on average every single week. But what's the smallest dino? And what can size reveal about the life of extinct animals? Hannah goes underground at the Natural History Museum to look through their vaults in search of the tiniest dinosaur with palaeontologist Susie Maidment. Meanwhile Adam chats to dinosaur expert Steve Brusatte from Edinburgh University about why size really does matter, especially when it comes to fossils. Presenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin.

The second instalment in our double bill on the science of sex, answering this question from Robert Turner, a Curio from Leeds: "Why do we only have two sexes?" Drs Rutherford and Fry look for anomalies in the animal kingdom that go beyond the traditional mechanics of human reproduction. Biologist and author Carin Bondar describes some of the wild and somewhat disturbing ways other animals like to do it. Take the hermaphrodite sea slug who races to stab its penis into its partner's brain during sex, or the female redback spider who loves to indulge in a spot of post-coital cannibalism. But the greatest number of different sexes is found in the world of fungi. Some species can have hundreds of distinct mating types. Fungal ecologist Lynne Boddy explains how mushrooms have sex and why on earth they need so many polygamous partners. Presenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin.

"Why do we only have two sexes and are there any anomalies in the animal kingdom?" asks Robert Turner from Leeds. From reptilian virgin births to hermaphrodite sea slugs, over the next two episodes Drs Rutherford and Fry examine the weird ways other creatures reproduce. In this first instalment, they tackle what's been called 'the hardest problem in evolutionary biology' - why does sex exist? Why aren't we all one single sex that clone ourselves to produce offspring? It makes perfect evolutionary sense - you could pass on all of your genes and don't need to bother finding a partner. Hannah visits London Zoo to meet a fierce komodo dragon named Ganas, the result of a virgin birth. And Adam meets some tiny bdelloid rotifers, microscopic worm-like females who have survived for 50 million years by cloning themselves. You can send your questions in to curiouscases@bbc.co.uk Presenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin.

"The other day I was watching the James Bond film Goldfinger. He boasts a laser powerful enough to project a spot on the Moon. Is this possible? If so, just how powerful would such a laser need to be?" This curious question was sent to curiouscases@bbc.co.uk by Eddie Griffith from Hinckley in Leicestershire. Adam visits one of the most powerful lasers in the world, the Gemini Super Intense Laser at the aptly named Rutherford Appleton Laboratory in Didcot, Oxfordshire. Plasma physicist Ceri Brenner gives him a quick zap, whilst explaining what would happen if they attempted to shoot their quadrillion watt laser at the Moon. Hannah talks to Tom Murphy from the University of California San Diego, who fires lasers at the Moon for a living. However, unlike Goldfinger, he's not using his Moon Laser for crime, he's using it for science. Presenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin.

"Are machines better than humans at identifying faces?" asks the excellently named Carl Vandal. Today's Face Off leads our intrepid detectives to investigate why we see Jesus on toast, Hitler in houses and Kate Middleton on a jelly bean. Face perception psychologist Rob Jenkins from the University of York explains why we're so good at spotting familiar faces, like celebrities. Plus, Franziska Knolle from the University of Cambridge discusses her face recognition study involving Barack Obama and a group of highly-trained sheep. But are we outwitted by artificial intelligence when it comes to face ID? BBC technology correspondent Rory Cellan-Jones gives us the low-down on the pros and cons of current technology. Presenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin.

"We often read that the fastest thing in the Universe is the speed of light. Why do we have this limitation and can anything possibly be faster?" Ali Alshareef from Qatif in Saudia Arabia emailed curiouscases@bbc.co.uk with this puzzling problem. The team grapples with Einstein's Special Theory of Relativity, with help from cosmologist Andrew Pontzen and a British train, travelling somewhat slower than the speed of light. Plus physicist and presenter Jim Al-Khalili describes how he nearly lost his boxer shorts in a daring bet concerning the speed of subatomic particles. Send your questions for consideration to: curiouscases@bbc.co.uk Presenters: Adam Rutherford, Hannah Fry Producer: Michelle Martin.

"Why don't children like vegetables?" asks Penny Young from Croydon, and every parent ever. This week Rutherford and Fry dig into the science of taste and discover that there may be more to this question than meets the eye. Children and adults have a different taste experience when they eat the same foods. When you're young, foods can taste saltier and more bitter. What's more, as Jackie Blisset, Professor of Childhood Eating Behaviour explains, there are even evolutionary reasons why toddlers avoid vegetables. For most children it's a phase, but a minority of adults are also labelled as fussy eaters. According to food psychologist Linda Bartoshuk, they are probably what's known as 'supertasters'. Supertasters live in a neon taste world where vegetables are more bitter, and chillies are unbearably hot. Adam sets out on a quest to find potential supertasters in the Radio 4 offices. First stop, the Today programme where Nick Robinson and Sarah Montague become his experimental guinea pigs, with surprising results. Send your questions for consideration to: curiouscases@bbc.co.uk Presenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin.

"Why don't thousands of bats in a cave get confused? How do they differentiate their own location echoes from those of other bats?" This puzzling problem was sent in to curiouscases@bbc.co.uk by Tim Beard from Hamburg in Germany. Since ecolocation was first discovered, this question has perplexed biologists. Hannah turns bat detective to try and track down these elusive creatures at The Queen Elizabeth Olympic Park in East London. This is where zoologist Kate Jones from University College London is using a network of smart sensors to find, identify and track wild bats. John Ratcliffe from Toronto University chats bats and sonar with Adam to try and locate the answer. It's an unlikely tale involving gruesome early experiments, cunning electric fish and some surprising bat maths. Send your Curious Cases for consideration to: curiouscases@bbc.co.uk Presenters: Adam Rutherford, Hannah Fry Producer: Michelle Martin.

"Why do we dream and why do we repeat dreams?" asks Mila O'Dea, aged 9, from Panama. Hannah and Adam delve into the science of sleep. From a pioneering experiment on rapid eye movement sleep, to a brand new 'dream signature' found in the brain, they discover how scientists are investigating our hidden dreamworld. Featuring sociologist Bill Domhoff from the University of California Santa Cruz, sleep psychologist Mark Blagrove from the University of Swansea, and neurologist Francesca Siclari from the University of Lausanne. Presenters: Adam Rutherford, Hannah Fry Producer: Michelle Martin.

Why do we get static shocks? Jose Chavez Mendez from Guatemala asks, "Some years ago, in the dry season, I used to be very susceptible to static electricity. I want to know - why do static shocks happen?" The team uncover some slightly unethical science experiments on static electricity from the 1700s. Hannah Fry uses a Leyden Jar to demonstrate how static electricity works with help from her glamorous assistant, Adam Rutherford. Spoiler Alert: it doesn't end well for Adam. They discover what makes some people more susceptible to static shocks, and how bees and spiders have harnessed the awesome power of electricity. Featuring electromagnetism scientist Rhys Phillips and physicist Helen Czerski, author of 'Storm in a Teacup: The Physics of Everyday Life'. Presenters: Adam Rutherford, Hannah Fry Producer: Michelle Martin.

Why do songs get stuck in our heads? And what makes some tunes stickier than others? Drs Rutherford and Fry investigate 'earworms', those musical refrains that infect our brains for days. Every morning 6Music DJ Shaun Keaveney asks his listeners for their earworms, and Hannah finds out which tunes keep coming back. Adam asks Dr Lauren Stewart, from Goldsmiths University, to reveal the musical features that make some songs catchier than others. And they find out why, in times of crisis, an earworm may just save your life. Producer: Michelle Martin.

No one knows why the Earth's magnetic North and South poles swap. But polar reversals have happened hundreds of times over the history of the Earth. So, asks John Turk, when is the next pole swap due and what will happen to us? Hannah turns to astronomer Lucie Green from Mullard Space Science Laboratory to discover how the earth's magnetic field protects us from the ravages of space. And Adam consults geophysicist Phil Livermore from the University of Leeds to find out if, and when, we're facing a global apocalypse. Plus astronaut Terry Virts, author of The View from Above, describes his experiences of a strange magnetic glitch in the earth's magnetic field, known as The Bermuda Triangle of Space, which could help us prepare for the next event. Presenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin.

Can chemistry help us bake the perfect cake? Listener Helena McGinty aged 69 from Malaga in Spain asks, "'I have always used my mother's sponge cake recipe. But is there a noticeable difference in the outcome if you vary some of the ingredients, or the method?" In this episode Hannah and Adam go head to head in a competition to create the perfect cake using the power of science. They are aided by materials scientist Mark Miodownik, from University College London, with tips on how to combine the ideal ingredients and trusted techniques to construct a structurally sound sponge. Jay Rayner, food critic and presenter of Radio 4's The Kitchen Cabinet, is on hand to judge the results. But who will emerge victorious in this messy baking battle? Presenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin.

"It started while listening to the excellent Experiment IV by Kate Bush. The premise of the song is of a band who secretly work for the military to create a 'sound that could kill someone'. Is it scientifically possible to do this?" asks Paul Goodfield. Hannah consults acoustic engineer Trevor Cox to ask if sonic weapons could kill. And Adam delves into subsonic frequencies with parapsychologist Chris French to investigate their spooky effects. You can send your everyday mysteries for the team to investigate to: curiouscases@bbc.co.uk Presenters: Adam Rutherford, Hannah Fry Producer: Michelle Martin.

"What is an itch and how does scratching stop it? Why does scratching some itches feel so good?!" asks Xander Tarver from Wisborough Green in West Sussex. Our doctors set off to probe the mysteries of itch, and discover that this overlooked area of medicine is revealing surprising results about the human brain. From why itching is contagious to why scratching is pleasurable, we get under the skin of this medical mystery. The programme features interviews with neuroscientist Prof Francis McGlone from Liverpool John Moores University, and dermatologist Dr Brian Kim from the Center for the Study of Itch at Washington University. Yes, that is a real place. You can send your everyday mysteries for the team to investigate to: curiouscases@bbc.co.uk Presenters: Adam Rutherford, Hannah Fry Producer: Michelle Martin.

"What is fire? Is it a solid, liquid or a gas? Why is it hot and why can you see it in the dark?" asks Hannah Norton, aged 10. Dr Fry visits the Burn Hall at The Buildings Research Establishment in Watford where they test the effects of fire on building materials. Whilst Dr Rutherford gets to grips with Michael Faraday's pioneering Christmas Lectures at the Royal Institution of Great Britain on 'The Chemical History of a Candle'. Plus, he chats to forensic chemist Niamh Nic Daeid from Dundee University about our lasting fascination with fire. You can send your Curious Cases for the team to investigate to: curiouscases@bbc.co.uk Presenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin.

"What's inside a black hole and could we fly a spaceship inside?" asks Jorge Luis Alvarez from Mexico City. Some interstellar fieldwork is on the agenda in today's Curious Cases. Astrophysicist Sheila Rowan explains how we know invisible black holes actually exist. And cosmologist Andrew Pontzen is on hand to help cook one up. But which of our intrepid doctors will volunteer to fly into the heart of a black hole? You can send your Curious Cases for the team to investigate to: curiouscases@bbc.co.uk Presenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin.

"How on earth do cats find their way back to their previous home when they move house?" asks Vicky Cole from Nairobi in Kenya. Our enduring love for our feline friends began when Egyptian pharaohs began to welcome domesticated moggies into their homes. Pictured reclining in baskets at the feet of royalty, pet cats soon became fashionable throughout society in Egypt. Today they are the most popular pet in the world, and home is definitely where their hearts lie. "Whereas dogs are bonded to people, cats are bonded to place," explains zoologist Dr John Bradshaw. "It's very typical for them to try and find their way back to their old house when you move." But how do they do it? And if their navigational skills are so good, why do they get lost? Plus, Prof Matthew Cobb reveals the super-senses that cats possess, which humans don't, and how to spot when your cat is deploying them. You can send your Curious Cases for the team to investigate to: curiouscases@bbc.co.uk Presenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin.

"Why do we have different blood types?" asks Doug from Norfolk. The average adult human has around 30 trillion red blood cells, they make up a quarter of the total number of cells in the body. We have dozens of different blood groups, but normally we're tested for just two - ABO and Rhesus factor. Adam and Hannah delve into the gory world of blood and the early history of blood transfusions, to discover why we have blood groups and what makes them so important. Featuring interviews with Dr Jo Mountford, from the Scottish National Blood Transfusion Service and immunologist Dr Sheena Cruikshank from the University of Manchester. Send your Curious Cases for consideration to: curiouscases@bbc.co.uk Presenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin.

"Why don't we remember the first few years of our lives?" asks David Foulger from Cheltenham. The team investigate the phenomenon of 'infant amnesia' and how memories are made with Catherine Loveday from the University of Westminster. A whopping 40% of people say they can remember back to before they were two years old, and 18% can recall being babies. But can we really trust these early memories? Martin Conway from City University discusses his latest findings, taken from data gathered during 'The Memory Experience' on BBC Radio 4. Presenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin.

"How far up can a helium balloon go? Could it go out to space?" asks Juliet Gok, aged 9. This calls for some fieldwork! Adam travels to the Meteorology Department at the University of Reading where Dr Keri Nicholl helps him launch a party balloon and track its ascent. But this experiment doesn't quite go to plan. Meanwhile, Hannah consults Public Astronomer Dr Marek Kukula, from the Royal Observatory Greenwich, to discover where space begins. And she decides to take matters into her own hands, with the help of a helium canister and some trusty equations, to help answer Juliet's question. Send your Curious Cases for consideration to: curiouscases@bbc.co.uk Presenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin.

"Why does the Earth spin?" asks Joe Wills from Accra in Ghana. Hannah quizzes cosmologist Andrew Pontzen about the birth of the Solar System and why everything in space seems to spin. Is there anything in the Universe that doesn't revolve? BBC weatherman John Hammond explain to Adam how the rotation of the Earth creates our weather systems and the strange things that would happen if we spun the opposite way. Send your Curious Cases for consideration to: curiouscases@bbc.co.uk Presenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin.

"Science tells us that our body houses microbial organisms. Then how much our weight is really our weight? If I am overweight, is it because of my own body cells or excess microflora?" asks Ajay Mathur from Mumbai in India. Adam bravely sends off a sample to the 'Map My Gut' project at St Thomas' Hospital to have his microbes mapped. Prof Tim Spector reveals the shocking results - a diet of fried breakfasts and fizzy drinks has left his guts in disarray. But help is at hand to makeover his bacterial lodgers. Science writer Ed Yong, author of 'I Contain Multitudes', reveals how much our microbes weigh. We're just beginning to discover the vast array of vital functions they perform, from controlling our weight, immune system and perhaps even influencing our mood and behaviour. Send your Curious Cases for consideration to: curiouscases@bbc.co.uk Presenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin.

Why do some people have a terrible sense of direction? The team receive a mysterious message from an anonymous listener who constantly gets lost. Can they help her find the answer? This listener may, or may not, be the team's producer, Michelle. She would like to state that it's not her fault that she has been dealt a bad genetic hand which has led to faulty place cells developing in her brain. And head direction cells that appear to be pointing the wrong way. More understanding should surely be afforded to those who are navigationally challenged. Hugo Spiers from University College London, has devised a free game called 'Sea Hero Quest' which anyone can use to test their navigational skills. Plus Catherine Loveday from the University of Westminster suggests strategies to help those who tend to get lost. If you have any Curious Cases for us to solve please email curiouscases@bbc.co.uk Presenters: Adam Rutherford & Hannah Fry Producer: Michelle Martin.

'A teacher I work with swears that around the time of the full moon kids are rowdier in the classroom, and more marital disharmony in the community," says Jeff Boone from El Paso in Texas. 'Is there any biological reason why the moon's phases could affect human moods and behaviour?' Our scientific sleuths sift through the evidence to find out if the moon really does inspire lunacy. They consider Othello's testimony, a study on dog bites and homicides in Florida before coming to a conclusion based on current scientific evidence. Featuring neuroscientist Eric Chudler from the University of Washington and health broadcaster and author Claudia Hammond. If you have any Curious Cases for the team to solve please email curiouscases@bbc.co.uk Presenters: Adam Rutherford & Hannah Fry Producer: Michelle Martin.

In the last episode the team started investigating the following inquiry, sent in to curiouscases@bbc.co.uk: 'Is there any such thing as nothing?' They discovered why quantum fluctuations and the Higgs field mean that nothing is impossible. But how about in mathematics? The story of zero is fraught with inspiration, competition and controversy. Banned in Florence and hated by the Church, zero had a rocky road to acceptance after its genesis in India. Hannah talks to author Alex Bellos and hears about his journey to India to see the birth of zero, featuring archive from 'Nirvana by Numbers' on BBC Radio 4. Plus, Adam is sent on a mission to understand calculus and enlists the help of Jeff Heys from Montana State University. If you have any Curious Cases for the team to solve please email curiouscases@bbc.co.uk Presenters: Adam Rutherford & Hannah Fry Producer: Michelle Martin.

"Is there any such thing as nothing?" This question from Bill Keck sparked so much head scratching that we have devoted two episodes to this curious quandary. In the first programme, the team considers the philosophy and physics of nothing. As Prof Frank Close, author of "Nothing: A Very Short Introduction" explains, nothing has intrigued great thinkers for thousands of years, from the Ancient Greeks to today's particle physicists. Otto Von Geuricke, the Mayor of Magdeburg in Germany, invented the artificial vacuum pump in the 17th century and presented spectacular displays to demonstrate the awesome power of nothing. Cosmologist Andrew Pontzen helps Hannah search for nothing in the depths of space and inside the atom. However, as they find out, recent discoveries in physics involving quantum fluctuations and the Higgs field have proved that nothing is impossible. If you have any Curious Cases for the team to solve please email curiouscases@bbc.co.uk Presenters: Adam Rutherford & Hannah Fry Producer: Michelle Martin.

'Why is my mother tone deaf?' asks listener Simon, 'and can I do anything to ensure my son can at least carry a tune?' Hannah Fry has a singing lesson with teacher Michael Bonshor to see if he can improve her vocal tone, although things don't quite go to plan.* We meet Martin who dislikes music intensely because he has the clinical form of tone deafness, known as amusia. Just as people with dyslexia see words differently to other people, if you have amusia you don't hear melodies in the same way. Adam talks to music psychologist Dr Vicky Williamson from Sheffield University who studies Martin, and others like him, to try and discover why their brains operate differently. Please send your Curious Cases for consideration to: curiouscases@bbc.co.uk Presenters: Adam Rutherford, Hannah Fry Producer: Michelle Martin *earmuffs may be required.

"What is the strongest substance in the universe? Some people say it is spiderweb, because it is stronger than steel. Is it iron? Is it flint? Is it diamond because diamond can be only be cut by diamond?" asks Françoise Michel. Adam and Hannah put a variety of materials, from biscuits to spider web, under the hammer to test their strength. In their quest to find the strongest substance they quiz materials scientist Mark Miodownik, engineer Danielle George and spidergoat creator, Dr Randy Lewis from Utah. Features archive from 'Horizon: Playing God', first broadcast in January 2012. Please send your Curious Cases for the team to investigate to curiouscases@bbc.co.uk Presenters: Adam Rutherford, Hannah Fry Producer: Michelle Martin.

Listener Paul Don asks: "I'm wondering what's the feasibility of terraforming another planet i.e. Mars and if it's possible to do the same thing with something like the moon? Or, why isn't there already a moon-base? Surely that's easier." Adam & Hannah consider moving to another planet, and discover what challenges they would need to overcome to live in space. They consult engineer Prof Danielle George from the University of Manchester and Dr Louisa Preston, UK Space Agency Aurora Research Fellow in Astrobiology. Adam also hears about attempts to recreate a Martian base on a volcano in Hawaii. He calls HI-SEAS crew member Tristan Bassingthwaighte, who has just emerged from a year of isolation. If you have any Curious Cases for the team to solve please email curiouscases@bbc.co.uk Features archive from 'Outlook' on BBC World Service, broadcast in August 2016. Presenters: Adam Rutherford & Hannah Fry Producer: Michelle Martin.

"Why do we have middle aged spread?" asks Bart Janssen from New Zealand. From obese mice to big bottoms, the duo discovers what science can tell us about fat. Why do we put on weight in middle age? And are some types of fat better than others? Hannah meets Prof Steve Bloom at Imperial College, London to discuss apples and pears. Adam talks to Dr Aaron Cypess from the National Institutes of Health in Maryland, who has created a 'fatlas' - an atlas that maps fat inside the body. Please email your Curious Cases for the team to investigate to: curiouscases@bbc.co.uk Presenters: Hannah Fry & Adam Rutherford Producer: Michelle Martin.

In the previous episode the team started investigating the following enquiry, sent in to curiouscases@bbc.co.uk: "What determines left or right handedness and why are us lefties in the minority?" They considered cockatoos, chimpanzees and Hannah's dog, Molly, to discover that humans are unique, with just one in ten of us being left-handed. Today, they look inside the left-handed brain. Some researchers point to a link between left-handedness and impairments like autism or dyslexia. Others claim that lefties are more creative and artistic. So what's the truth? The team consults Professors Sophie Scott, Chris McManus and Dorothy Bishop to find out. Presenter: Adam Rutherford & Hannah Fry Producer: Michelle Martin.

Neal Shepperson asks, "What determines left or right handedness and why are us lefties in the minority?" When we started investigating this question it became clear that there were just too many scientific mysteries to squeeze into one episode. So there are two whole episodes devoted to this very Curious Case. One in ten people are left-handed, but where does this ratio come from and when did it appear in our evolutionary past? Hannah talks to primatologist Prof Linda Marchant from Miami University about Neanderthal teeth and termite fishing. Adam consults handedness expert Prof Chris McManus from University College London. He's been trying to track down the genes responsible for whether we're right or left handed. If you have any Curious Cases for the team to investigate please email curiouscases@bbc.co.uk Presenter: Adam Rutherford & Hannah Fry Producer: Michelle Martin.

"Can horses count?" asks retired primary school teacher, Lesley Marr. Our scientific sleuths consider the case of Clever Hans, with a spectacular re-enactment of a 20th century spectacle. Plus, we hear from Dr Claudia Uller who has been conducting modern studies on equine counting. Mathematician Prof Marcus Du Sautoy explains the basic concept of counting to Adam, and Hannah looks across the animal kingdom to find the cleverest mathematical creature. If you have any questions you'd like the duo to investigate, please email curiouscases@bbc.co.uk Presenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin.

Our science detectives answer the following perplexing problem, sent in by Hannah Monteith from Edinburgh in Scotland: "How does leg hair know it has been cut? It doesn't seem to grow continuously but if you shave it, it somehow knows to grow back." Hannah consults dermatologist Dr Susan Holmes, from the Hair Clinic at Southern General Hospital in Glasgow, to discover why the hairs on your legs don't grow as long as the hairs on your head. Adam attempts to have a serious discussion about the evolutionary purpose of pubic hair with anatomist and broadcaster Prof Alice Roberts. If you have a scientific mystery for the team to investigate, please email: curiouscases@bbc.co.uk Presenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin.

Today the team study the heavens, thanks to listener Brian Passineau who wonders 'why everything in space tends to be circular or spherical?' Hannah gazes at Jupiter at The Royal Observatory, Greenwich with Public Astronomer, Dr Marek Kukula. Science writer, Philip Ball, explains how the astronomical obsession with celestial spheres came to an untidy end. And physicist Dr Helen Czerski helps Adam on his quest to find the perfect natural sphere. If you have a scientific mystery for the team to investigate, please email: curiouscases@bbc.co.uk Presenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin.

Listener Edith Calman challenges our scientific sleuths to investigate the following conundrum: 'What is it about extreme pain, emotional shock or the sight of a three year old stumbling their way through an off-key rendition of 'Away in a Manger' that makes the brain send messages to the lacrimal glands to chuck out water?" Hannah discovers how the eye produces tears, with the help of Dr Nick Knight. Broadcaster Claudia Hammond, author of 'Emotional Rollercoaster', explains why Darwin experimented on his children until they cried. Adam watches a tearjerker to take part in a psychological study, but ends up getting quite angry instead. If you have any everyday mysteries you'd like the team to solve email: curiouscases@bbc.co.uk Presenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin.

Today the team examine the chemistry of tea, in answer to the following question sent in by Fred Rickaby from North Carolina: "When we are preparing a cup of tea and the cup contains nothing but hot, brewed tea we need to add milk and sugar. My wife always adds the sugar first, stirs the cup to make sure it is dissolved and then add the milk. So, is that an optimum strategy for adding milk and sugar to a cup of tea?” Adam consults Prof Andrea Sella from University College London about the perfect formula for a cup of tea. Inside his tea factory in Kent, Master Blender Alex Probyn teaches Hannah an unusual method for tasting tea. Most importantly, the duo discovers whether you should add milk first or last. But can tea professionals really tell the difference? If you have any questions for Drs Rutherford & Fry to investigate send them to curiouscases@bbc.co.uk Presenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin

An unusual case today for science sleuths Hannah Fry and Adam Rutherford sent by Elisabeth Hill: 'Can we shoot garbage into the sun?' The duo embark on an astronomical thought experiment to see how much it would cost to throw Hannah's daily rubbish into our stellar dustbin. From space elevators to solar sails, they explore the various options that could be used to send litter to the Sun. Featuring space scientist Lucie Green and astrophysicist Andrew Pontzen. If you have any everyday mysteries for the team to investigate using the power of science, please email: curiouscases@bbc.co.uk Presenters: Hannah Fry & Adam Rutherford Producer: Michelle Martin.

Science sleuths Hannah Fry and Adam Rutherford investigate the following question sent in by Philip Le Riche: 'Why do some people faint at the sight of blood, or a hypodermic needle, or even if they bash their funny bone? Does it serve any useful evolutionary purpose, or is just some kind of cerebral error condition?' Adam is strapped onto a hospital tilt table in an attempt to make him blackout and Hannah receives an aromatic surprise. Featuring consultant cardiologists Dr Nicholas Gall and Dr Adam Fitzpatrick and cardiac physiologist Shelley Dougherty. If you have any scientific cases for the team to investigate please email: curiouscases@bbc.co.uk Presenters: Hannah Fry & Adam Rutherford Producer: Michelle Martin.

Drs Rutherford and Fry tackle a vexing case sent in by Daniel Sarano from New Jersey, who asks why people shout on their mobile phones in public. Our science sleuths find the answer by delving into the inner workings of telephony with a tale of engineering rivalry, Victorian etiquette and early otolaryngology. Featuring acoustic technologist Nick Zakarov and historian Greg Jenner, author of 'A Million Years in a Day: A Curious History of Daily Life.' If you have any scientific cases for the team to investigate please email: curiouscases@bbc.co.uk Presenters: Hannah Fry & Adam Rutherford Producer: Michelle Martin.

Drs Rutherford and Fry set out to discover what makes traffic jam. Adam ventures on to the M25 in search of a tailback, and Hannah looks at projects around the world that have attempted to solve the scourge of the traffic jam. Featuring Neal Harwood from the Transport Research Laboratory and BBC technology reporter, Jane Wakefield. And Masdar City man. If you have any scientific cases for the team to investigate please email: curiouscases@bbc.co.uk Presenters: Hannah Fry & Adam Rutherford Producer: Michelle Martin.

Drs Adam Rutherford and Hannah Fry are on hand to solve everyday mysteries sent in by listeners. For the last few weeks they've been collecting cases to investigate using the power of science - from why people shout on their mobile phones to what causes traffic jams. In the first episode, called 'The Scarlet Mark', they get to the root of the following conundrum, posed by Sheena Cruickshank in Manchester: 'My eldest son is ginger but I am blonde and my husband brunette so we are constantly asked where the red came from. Further, people do say the "ginger gene" is dying out, but how good is that maths or is it just anecdotal?' Our science sleuths set out to discover what makes gingers ginger with a tale of fancy mice, Tudor queens and ginger beards. Featuring historian and author Kate Williams and Jonathan Rees from the University of Edinburgh, one of the team who discovered the ginger gene. If you have any scientific cases for the team to investigate please email: curiouscases@bbc.co.uk Presenters: Hannah Fry & Adam Rutherford Producer: Michelle Martin.