Sneezes, wheezes, runny noses and red eyes - this episode is all about allergies.

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

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

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...

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

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.