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

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 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.

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

"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.

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

"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.

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

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.

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

First broadcast on BBC Radio 4 in March 2022.

Mathematician Hannah Fry and geneticist Adam Rutherford investigate your everyday science queries.

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

First broadcast on BBC Radio 4 in March 2022.

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?

Presenters: Hannah Fry and Adam Rutherford Producer: Pamela Rutherford

First broadcast on BBC Radio 4 in March 2022.

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

First broadcast on BBC Radio 4 in March 2022.

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

First broadcast on BBC Radio 4 in 2022.

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

‘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.

Dr Adam Rutherford and Dr Hannah Fry 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

First broadcast on BBC Radio 4 in February 2022.

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 Principal 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

Producer: Fiona Roberts

First broadcast on BBC Radio 4 in November 2021.