Can you slow down time by hurtling through space at breakneck speed? Could listener Saskia’s friend - currently one year older - end up the same age as her if he went fast enough? It sounds bananas, but it’s all part of Einstein’s mind-warping theory of relativity.

With expert copilots Professor Sean Carroll and Dr. Katie Clough, Hannah Fry and Dara Ó Briain embark on a cosmic roller coaster through space and time. They uncover why GPS satellites - whizzing around Earth at 14,000 km/h - need to account for time bending, why penthouse dwellers age faster than those on the ground floor, and, most importantly, why clowns on trains might just hold the key to understanding modern physics.

Contributors:

Katy Clough - Research Fellow at Queen Mary University of London

Producer: Ilan Goodman

How big can animals really get before they collapse under their own weight or run out of snacks? Could a 12-foot comedian survive their first punchline without snapping in half? Listener Andrew sends Hannah and Dara on a deep dive into the science of supersized species.

With evolutionary biologists Ben Garrod and Tori Herridge as their guides, they explore the quirky rules of scaling: why giant bones need air pockets, how pressure stockings aren’t just stylish but essential, and why massive creatures have to choose between inefficient chewing or letting dinner ferment in their cavernous stomachs.

Discover why scaling up a mouse would turn it into a blood-boiling disaster and learn the curious logic behind whether the meat bear should eat the two meat dogs, or vice versa (it’s a maths thing…you’ll have to listen). Oh, and here’s the weird constant: whether you’re a mouse or an elephant, everyone takes roughly the same time to pee!

Join Hannah and Dara for a colossal romp through the wild world of ancient giants and the gross super blobs of the (possible) future.

Contributors:

Tori Herridge - Senior Lecturer in evolutionary biology at the University of Sheffield

Producer: Ilan Goodman

Think of a shark and you'll probably conjure up images of Jaws, but it turns out their skin is also covered in tiny teeth. Hannah and Dara investigate the incredible properties of these so-called dermal denticles, to find out whether they could be replicated at a nanoscale to increase vehicle speeds. They learn that while sharks might look like they have beautifully sleek surfaces, up close their skin is covered in something extremely rough and textured, a property that helps them swim up to 12 percent faster. And it's already inspiring airlines to design ultra-thin films that can reduce drag and increase efficiency.

Contributors

Dr Jess Wade

Producer: Marijke Peters

A BBC Studios Audio Production

Why do we giggle, snort, and bust a gut laughing? Is it just humans being weird, does it serve some higher function or do other animals crack up too? And, okay, Dara is a comedian, but has he ever really made anyone laugh, like properly?

With help from Professor Greg Bryant and Professor Sophie Scott, they dive into the science of LOLs, exploring how laughter bonds us, eases stress, and even spices up flirting. They uncover the difference between genuine belly laughs and those polite chuckles that pepper everyday interactions.

Contributors:

Sophie Scott - Professor of Cognitive Neuroscience at UCL

Producer: Ilan Goodman

Ever wondered why some people are mosquito magnets and other people barely get bitten? Hannah and Dara grapple with the question of whether these insects are evil or genius, discovering how they’re experts at finding blood when they’re hungry, even using a specially designed syringe to suck it out. But when Professor Leslie Vosshall tells them some people are more than 100 times likely to be attacked than others, the pair start wondering which one of them is more attractive? So they put the science to the test, and reluctantly agree to send their stinky socks to Professor Sarah Reece. She reveals that one of them smells extra special to these annoying little animals, possibly because of their cheesy feet. But can you guess who?

Contributors:

Producer: Marijke Peters

The team test the theory that you can use the weather to predict pain, separating science fact from fiction. It's an area with a huge amount of conflicting research, but one man who has investigated this is Professor Will Dixon, who explains that low pressure could be causing people's joints to ache more. Dara and Hannah are intrigued to hear our genes may also be responding to changes in temperature and hear how we might be pre-programmed to produce more inflammation during wintertime to fight off bugs - which has the unfortunate side effect of making other some conditions worse. But don't despair! The pair find out 21 degrees is the optimum temperature for health and wellbeing - a perfect English summer day.

Contributors:

Dr Chris Wallace

Producer: Marijke Peters

A BBC Studios Audio Production

From mouldy bread to athlete’s foot, fungi don’t exactly scream “home improvement.” But what if this misunderstood kingdom is the secret to the sustainable materials of the future?

Listener Alexis - definitely not a gnome - wants to know how much of our homes we could build with fungi. Professor Katie Field describes how the mushroom is the just tip of the iceberg - it’s the network of thread-like filaments called mycelium where fungi really do their best work. Architect Phil Ayers explains how fungi, like yeast in bread, can bind waste products into firm, MDF-like blocks. And while we’re not constructing skyscrapers with mushrooms just yet, it turns out fungi-based materials are already making waves in interior design. Think sound-absorbing wall panels or insulation that’s both eco-friendly and chic.

And here’s a cool one: mushroom leather! Using discarded stalks from mushroom farms, one company is crafting strong, flexible material for trainers, handbags, and even car dashboards. Move over, cows - mushrooms are pushing their way up.

Oh, and NASA? They’re dreaming big with fungi too - to grow habitats in space. From mould...to the moon!

Contributors:

Katie Field - Professor of Plant-Soil Processes at the University of Sheffield

Producer: Ilan Goodman

What happens in your brain when Cupid’s arrow strikes? As a teenager, Alison developed an intense crush on George Harrison from the Beatles. But, she wants to know, why do we develop these feelings for pop stars we’ve never actually met? And what potent swirl of neurochemistry drives those fierce emotions?

With neuroscientist Dr. Dean Burnett and evolutionary anthropologist Dr. Anna Machin as their guides, Hannah and Dara investigate everything from the brain’s chemical fireworks during a crush to the evolutionary perks of love and bonding. Along the way, they dissect teenage infatuations, lifelong love affairs with football teams, and why love can feel as addictive as heroin.

There’s even a guest appearance from two cute rodents: the monogamous prairie voles and their more, shall we say, commitment-phobic cousins, the montane voles, who gave us early clues about the role of the ‘cuddle’ hormone oxytocin.

Whether you're a hopeless romantic or a hard-nosed skeptic, prepare to fall head over heels for the science of love.

Contributors:

Dr Anna Machin - evolutionary anthropologist and author of Why We Love

Producer: Ilan Goodman

Hannah and Dara tackle a disarmingly simple question: is anything in the universe truly invisible? After ruling out mysterious Nordic spirits and ‘Dara’s ire’, our curious duo start to track down the invisible waves all around them. Including, it turns out, some which are emanating from their VERY OWN FACES! An infrared camera reveals Hannah’s nose as a particular hotspot.

Turning their gaze to bigger things, they wonder: what does our own galaxy look like when viewed in this invisible spectrum? Infrared reveals vast loops and whorls of dust and gas - gigantic structures otherwise totally hidden. But there are even cooler surprises. Ever wondered what an X-ray of the universe looks like? Turns out it’s a sparkly map of white-hot black holes!

Back on earth, the discussion turns to ways of making objects disappear by bending light in tricksy ways. But why is the fancy science of ‘metamaterials’ still struggling to make a proper invisibility cloak? Sorry, Harry Potter fans.

In the end, our physicists reveal a universe bursting with even more elusive, even more mysterious stuff: dark matter and dark energy. Prepare to see the unseen in a whole new light!

Contributors:

Matthew Bothwell - the Public Astronomer at the University of Cambridge and author of The Invisible Universe

Producer: Ilan Goodman

For any of you who have ever told a porkie pie, don't worry, this week we hear why we all do it... and discover that deception is actually good for social bonding. From the red squirrels who cry wolf to scare off the competition, to kids who look you in the eye as they tell bare faced lies, this is a behaviour that occurs across all species. And one man who's particularly good at it is Traitors contestant Paul Gorton who reveals he felt absolutely no guilt about his tv trickery. But it seems that while we're masters at telling tall stories, we're terrible at detecting them, because we've all been focusing on completely the wrong cues.

Contributors:

Paul Gorton

Producer: Marijke Peters

A BBC Studios Audio Production