Dara O Briain and Isy Suttie meet special guest experts to help them unravel some seriously surprising tales.

The buzz of a fly hovering just above your head has got to be one of the most irritating sounds around, but this week we try to work out just how fast they could be flying. Could a claim horseflies reach speeds of up to 90 mph possibly be true, and Dara wants to know if this is what makes them so difficult to swat? Entomologist Erica McAlister is better known as the ‘fly lady’ and speaks up in defence of these tiny creatures, explaining there are 7,000 known species in the UK alone. Which makes it all the more shocking there are several that don’t have wings. For Professor Graham Taylor the question of speed comes down to a simple calculation, and the team try to work out whether a horsefly beats its wings fast enough relative to its size to travel so rapidly. He explains horseflies aren't clever, but scientists are interested in their simple brains and are studying them to use as models for drones and mini robots. Contributors: Dr Erica McAlister, Natural History Museum Professor Graham Taylor, Oxford University Producer: Marijke Peters Executive Producer: Alexandra Feachem A BBC Studios Audio Production

Anyone who has ever done a long car journey with kids will be familiar with the idea of being bored to death – but can this feeling really be fatal? Hannah and Dara hear about a club where members count roundabouts and collect milk bottle tops, but boredom expert Wijnand van Tilburg explains these dull-sounding hobbies might actually have mental health benefits. He explains that science and comedy are stereotypically both seen as exciting subjects but warns them their chat about Venn diagrams might tip the balance the other way. Mind-wandering specialist Mike Esterman reveals why we're rubbish at staying on task when there are more rewarding things to do, and sets the pair a challenge to play a computer game that distracts them with pictures of cute babies and fluffy animals. Contributors: Dr Wijnand van Tilburg: University of Essex Dr Mike Esterman: Boston Attention and Learning Lab Producer: Marijke Peters Executive Producer: Alexandra Feachem A BBC Studios Audio Production

When you die, would you want to be frozen so that one day you might be brought back to life? Listener Elspeth wants to know if that’s even possible. So Hannah and Dara embark on a quest to explore the chiling science of ‘cryobiology’: preserving living things at really low temperatures. It turns out there are already thousands of people alive who were once suspended in antifreeze and stored in liquid nitrogen - when they were just a small clump of cells! There’s even a frog which can turn into a ‘frogsicle’ for months on end. But re-animating full size humans is a challenge no one has solved…yet. Will some miraculous nanotechnology of a distant future solve the problem? Contributors: Professor João Pedro de Magalhães: University of Birmingham Hayley Campbell: Author and broadcaster Professor Joyce Harper: UCL Dr Hanane Hadj-Moussa: The Babraham Institute, Cambridge Garrett Smyth: Cryonics UK Producer: Ilan Goodman Executive Producer: Alexandra Feachem A BBC Studios Audio Production

Wake up! It’s time for a dreamy new episode of Curious Cases all about the science of sleepwalking. Listener Abigail has done some strange things in her sleep, from taking all the pictures off the wall, to searching for Turkish language courses. And she wants to know: WHY IS THIS HAPPENING? It turns out Abigail is not alone. Hannah and Dara hear weird and wonderful stories of extreme sleepwalkers - from the lady who went on midnight motorbike excursions, to the artist who does all his best work while asleep. They delve into the neuroscience to find out how you can remain in deep sleep while walking, talking or even peeing in your mum's shopping basket. They learn about some cutting edge research where the participants were sleep deprived and then half-woken with scary sounds, and they zero in on the key triggers, from a boozy night out to a squeaky bed. Contributors Professor Russell Foster: University of Oxford. Professor Guy Leschziner: King’s College London and Guys’ and St Thomas’ hospital Lee Hadwin: the sleep artist Professor Francesca Siclari: The Netherlands Institute for Neuroscience Producer: Ilan Goodman Executive Producer: Alexandra Feachem A BBC Studios Audio Production

Fruit-powered batteries are the ultimate school science experiment, but they’re normally used to power a pocket calculator. This week’s listener wants to know if they could do more, and sends the team on a quest to discover whether they could used to send a rocket into space? Professor Saiful Islam is the Guinness World Record holder for the highest voltage from a fruit-based battery, but disappoints the team when he reveals they produce very little power. He used 3,000 of them and only managed a measly 2 Watts. Given that spaceships are famously difficult to get off the ground, it seems a lemon battery might just fail the acid test. Author Randall Munroe is undeterred and suggests alternative ways to get energy from citrus, including burying them to make oil. Then the team discuss the pros and cons of switching to a lemon-based diet. For battery expert Paul Shearing, all this raises a serious question, about how we will power the planes of the future. He suggests solar power could play a part in short-haul flights and discusses some of the exciting battery materials being tested today. Contributors: Randall Munroe, author Professor Paul Shearing, Oxford University Professor Saiful Islam, Oxford University Producer: Marijke Peters Executive Producer: Alexandra Feachem A BBC Studios Audio Production

Are you more of a rhino or a kitten? More like a tortoise or a hare? Listener Ivy wants to know what makes a good athlete and so Hannah and Dara tackle the science of sport. Our curious duo get to grips with the rigours of training tailored for endurance events vs those based on more explosive bursts of activity. They consider the contribution of genetics, fast vs slow twitch muscle fibres, the unique advantage of Michael Phelps's body proportions and whether butterfly really is the most ridiculous stroke in swimming. And after a rigorous scientific analysis, Dara turns out to be ideally suited for…netball. Much to his surprise. Contributors Dr Polly McGuigan: University of Bath Dr Mitch Lomax: University of Portsmouth Professor Alun Williams: Manchester Metropolitan University Dr Josephine Perry: Sports psychologist Producer: Ilan Goodman Executive Producer: Alexandra Feachem A BBC Studios Audio Production

Listener Vivienne has heard that tardigrades - aka moss piglets - have special powers of survival. Radiation? Drought? Extreme cold? NO PROBLEM. Does that mean they could survive an apocalypse? And could they even help us master space travel!? Hannah and Dara learn how to find these little moss piggies in roof gutters and garden corners. And they're amazed by their capacity to dry out and hunker down for decades before springing back to life. But calamity strikes when it turns out that fine glass tubing - in the form of pipettes - is their natural predator. And worse is to come: our curious duo learn that there may be some tardigrades stuck on the moon, and one researcher has even fired them out of a gun. All in the name of science. But they have survived at least 5 mass extinctions so far. So their chances of surviving the next one are pretty good. As long as pipettes aren't involved. Contributors Dr James Frederick Fleming: Natural History Museum of Norway and the University of Oslo Dr Nadja Møbjerg: University of Copenhagen Dr Thomas Boothby: University of Wyoming Producer: Ilan Goodman Executive Producer: Alexandra Feachem A BBC Studios Audio Production

If there’s one type of discharge you really want to avoid, it’s lightning, but what happens when it hits you? We hear from lightning survivor Kerry Evans, and discover that the best place to shelter – if you ever find yourself in a similarly charged storm – is in a car, or low to the ground. And why this is never a good time to take a selfie. Dr Dan Mitchard from Cardiff University’s excitingly-named Lightning Lab explains why there's no lightning at the poles, and the presenters lament that polar bears and penguins are missing out. We all know about the gods of lightning, but the mysticism doesn't stop there. Above cloud level there are many other types of unusually-named phenomena, reaching to the edge of space, including sprites, trolls and even pixies. And Professor Karen Aplin reveals that lightning has even been discovered on other planets, in a science story that could affect our plans to colonise Mars. Contributors: Dr Daniel Mitchard, Lightning Laboratory, Cardiff University Professor Karen Aplin, University of Bristol Producer: Marijke Peters Executive Producer: Alexandra Feachem A BBC Studios Audio Production

11 year old Esther visualises days of the week in a kind of 3D structure. It’s something called ‘synaesthesia’ and she wants to know why it happens - and why other people don’t experience things the way she does. Hannah Fry and Dara Ó Briain explore the vibrant and varied ways different people experience the world, from the man who tastes individual words - including all the stops of the tube - to the composer who sees music in shapes and colours. And along the way, they figure out why Mozart is white wine while Beethoven is red. Contributors: Professor Julia Simner: Professor of Psychology,University of Sussex Professor Jamie Ward: Professor of Cognitive Neuroscience, University of Sussex James Wannerton, President of UK Synaesthesia Association CoriAnder: electronic music producer Producer: Ilan Goodman Executive Producer: Alexandra Feachem A BBC Studios Audio Production

It’s sometimes said that timing is everything and this week the pair investigate the mystery of rhythm, discovering why some of us might be better at staying in tempo. From the daily cycle of dawn and dusk to sea tides and circadian clocks, rhythm governs many aspects of our lives, and cognitive psychologist Dr Maria Witek says it makes sense we also place great importance on its presence in music. She specialises in ‘groove’, or the feeling of pleasure associated with moving to a beat – and it’s not just something the dancers among us enjoy; groove has even been used to treat patients with Parkinson’s Disease. Neuroscientist Professor Nina Kraus has studied drummers’ brains and found their neurons fire with more precision. She explains that teaching kids rhythm can improve their language and social skills. But no need to take her word for it, because Skunk Anansie’s drummer Mark Richardson is in the studio to put Hannah to the test. Can she handle a high hat at the same time as a snare? Contributors: Dr Maria Witek, University of Birmingham Professor Nina Kraus, Northwestern University Mark Richardson, drummer with Skunk Anansie Producer: Marijke Peters Executive Producer: Alexandra Feachem A BBC Studios Audio Production

9 year old listener Koby sends Hannah and Dara on a mission to find the shiniest thing in the world. And so they enter a world of mirrors… The journey takes them into the subatomic goings on of shiny metal surfaces, where electrons waggle and dance and send light waves back at *just* the right angle. Our curious duo play with an astonishingly reflective plastic film that can be found hidden in devices we all use. And they probe the mysterious power of refraction, harnessed to make the $2 million mirrors which reflect the lasers at the huge LIGO experiment. And everyone ponders the surprisingly reflective properties of a pint in space. Contributors: Dr Felix Flicker: University of Bristol, author of The Magick of Matter Professor Stuart Reid: University of Strathclyde Quinn Sanford: optical engineer from 3M GariLynn Billingsley: Optical Sciences Group Leader at LIGO Producer: Ilan Goodman Executive Producer: Alexandra Feachem A BBC Studios Audio Production

Would you eat food that fell on the floor? That’s the question Hannah and Dara are getting their teeth into this week as they put the so-called ‘5 second rule’ through its paces. For some people it’s 3 seconds, and for others its 10 – especially if it involves a dropped ice cream and a screaming child. But microbiologist Don Schaffner says there’s no safe amount of time to leave food on the floor if you’re planning to eat it. And while you might think buttered toast would pick up the biggest number of bugs, it may surprise you to hear that wet foods like watermelon are actually the worst when it comes to attracting harmful bacteria. If all this is putting you off your dinner, the bad news is that the rest of your kitchen is also a microbiological minefield. Research shows nearly 70% of us keep our fridges are the wrong temperature, which sparks a lively discussion about whether it’s ever safe to reheat rice. For home hygiene guru Sally Bloomfield it’s all a question of being a bit more clever about the kind of germs we expose ourselves to and weighing up risks. Contributors: Dr Don Schaffner: Rutgers University Dr Ellen Evans: Cardiff Metropolitan University Professor Sally Bloomfield: International Scientific Forum on Home Hygiene Producer: Marijke Peters Executive Producer: Alexandra Feachem A BBC Studios Audio Production

While chatting at the back of class, best mates Abi and Sofia got curious about bubbles. How do you make really giant ones? Could you even get one around the entire planet? Hannah and Dara set out to investigate. They hear from a renowned 'bubbleologist', and learn how NASA helped him blow his way to a world record. They coax a physicist to reveal the secrets of his peer-reviewed bubble-juice formula, and investigate how bubbles work in space and in the ocean. Our curious duo also discover an audacious project aiming to build a Brazil-sized raft of bubbles... in space! Contributors: Dr Helen Czerski, UCL Dr Justin Burton, Emory University Dr Awesome, Bubbleologist Professor Carlo Ratti, MIT Producer: Ilan Goodman Executive Producer: Alexandra Feachem A BBC Studios Audio Production

Curious Cases is returning! Superstar mathematician and broadcaster Hannah Fry teams up with legendary comedian and fellow science nerd Dara Ó Briain for an all-new series of the show which takes your quirkiest questions and solves them with the power of SCIENCE. In this short preview ep, our dynamic duo tease some of the upcoming episodes in which they enlist the world’s top experts to tackle the most profound and puzzling questions to have ever trickled through your curious minds: Could you power a spaceship with a lemon? Can you actually die of boredom? Why do some people *taste* words? Why does Hannah have absolutely no sense of rhythm? And could we stop climate change with massive space bubbles!? Producers: Marijke Peters and Ilan Goodman Executive Producer: Alexandra Feachem A BBC Studios Audio Production

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