It has been said that you can't start a fire without a spark, but as Hannah and Dara are about to discover, that's not true!

Welcome to the fiery phenomenon of spontaneous combustion, when something can ignite all on its own: no matches, no sparks, no external flame. It happens when certain materials heat themselves up internally through chemical or biological reactions, and if that carried on unchecked and the material gets hot enough, it can eventually ignite itself.

This process can occur in various everyday items such as piles of hay or grass clippings, oily rags and in certain instances lithium batteries; but there are also several useful chemical substances that autoignite when they come into contact with air - as Hannah, Dara and a wary BBC fire officer witness in the studio...

So how can we stop things regularly bursting into flames? How scared should we be about oiling floorboards and our increasingly battery-powered life? And is spontaneous human combustion really a thing? Our investigators are on the case.

To submit your question to the Curious Cases team, please email: curiouscases@bbc.co.uk

Contributors: - Andrea Sella, Professor of inorganic chemistry at University College London - Emanuel ‘Big Manny’ Wallace, former science teacher now a science content creator - Matt Oakley, fire investigations officer at Surrey Fire and Rescue Service - Roger Byard, Emeritus Professor of pathology at the University of Adelaide and a senior specialist forensic pathologist at Forensic Science SA (FSSA)

Producer: Lucy Taylor Executive Producer: Alexandra Feachem

A BBC Studios Production

Are you a lucky person? Do the cards just fall well for you? Whether it's always finding a parking spot when you need one or chance encounters that change your life's trajectory for the better, some people seem to have more luck than others. Hannah and Dara explore the world of probability and psychology to figure out if some people are luckier than others, and if there's anything we can do to turn things around.

You can send your everyday mysteries for the team to investigate to: curiouscases@bbc.co.uk

Contributors David Spiegelhalter - Emeritus Professor of Statistics in the Centre for Mathematical Sciences at the University of Cambridge Richard Wiseman - Professor of the Public Understanding of Psychology University of Hertfordshire Maia Young - Professor of Organization and Management at UC Irvine, California US Edward Oldfield

Producer: Emily Bird Executive Producer: Sasha Feachem A BBC Studios Production

It turns out that the whole world wobbles. Everything has a natural frequency - the rate at which it moves when disturbed - be it a cup of tea, a building or a human organ.

Even more incredibly, if an external force matches an object's natural frequency, it causes it to absorb that energy and vibrate with increasingly large waves; and that can have consequences, from helping a spider find its lunch to making a bridge collapse.

On the trail of good and bad vibes and everything in between, Hannah and Dara investigate whether the famous 1940 collapse of the Tacoma Narrows Bridge in the USA was really down to resonance, explore examples of resonance in nature, and find out what this mysterious vibration can do to the human body: from the pressures of repetitive tractor-driving, to absorbing the reverberations of certain instruments...

To submit your question to the Curious Cases team, please email: curiouscases@bbc.co.uk

Contributors: - Helen Czerski, Professor of Physics at University College London - Wanda Lewis, Emeritus Professor of Civil Engineering at Warwick University - Phillip Moxley, Senior Research Associate at the University of Southampton - Sana Bokhari, sound therapy practitioner

Producers: Lucy Taylor & Emily Bird Executive Producer: Alexandra Feachem

A BBC Studios Audio Production

We can all picture a crab, but did you know that nature has reinvented those claw clicking, sideways scuttling crustaceans at least five separate times? In recent years the internet has run wild with the idea that crabs are the ultimate life-form, and that even humans might one day end up with pincers too. But is there any truth behind the memes? Hannah and Dara scale the tangled tree of life and tackle taxonomy to figure out if ‘crab’ really is evolution’s favourite shape. Exploring coconut to spanner, ghost to hermit, soldier to spider they learn how to tell the ‘true’ crabs from the impostors.

You can send your everyday mysteries for the team to investigate to: curiouscases@bbc.co.uk

Contributors Dr Joanna Wolfe – Evolutionary Biologist, Harvard University and UC Santa Barbara Professor Matthew Wills - Professor of Evolutionary Paleobiology, University of Bath Ned Suesat-Williams – Director of the Crab Museum, Margate

Producer: Emily Bird Executive Producer: Sasha Feachem A BBC Studios Production

Hannah Fry and Dara Ó Briain return to Curious Cases HQ for a brand-new series. And curios, there’s a lot to unpack! Coming soon to BBC Sounds.

The term 'bird brain' might suggest our feathered friends are stupid, but Hannah and Dara learn it's completely untrue. They play hide and seek with a raven called Bran, and hear how his behaviour changes depending on his mood. Corvid expert Nicola Clayton explains these creatures are actually cleverer than the average 8-year-old, and can learn how to choose specific tools for different scenarios. And neurobiologist Andreas Nieder tells them that while crows evolved totally different brains from humans - 300,000 years apart - they might just be capable of the same type of intelligence.

Contributors:

Bran the raven Lloyd Buck, bird handler Professor Nicky Clayton, University of Cambridge Professor Andreas Nieder, University of Tubingen

Producer: Marijke Peters Executive Producer: Alexandra Feachem

A BBC Studios Audio Production

Could you ever trade memories with someone else? Fancy downloading the experience of landing on the moon, winning an Oscar or performing at Glastonbury? Listener Adam wants to know, and Hannah Fry and Dara Ó Briain are on the case.

With expert insights from Professor Chris French and Professor Amy Milton, they dive into the mind’s tendency to blur the lines between reality and imagination - often embellishing, distorting, or downright making stuff up.

Discover how memory conformity makes us “see” things like spoons being bent by paranormal forces, how scientists can implant artificial memories in mice, and hear Al Hopwood’s hilariously vivid tales of things that definitely never happened. Chris even spills the secrets of how to deliberately plant false memories in others (don’t try this at home!).

From rewiring trauma to curing phobias, the potential of memory manipulation is both exciting and unnervingly sci-fi. Prepare to question everything you think you remember.

Contributors:

Amy Milton - Professor of Behavioural Neuroscience at the University of Cambridge Chris French - Professor of Anomalistic Psychology at Goldsmiths University Al Hopwood - Artist, writer and curator

Producer: Ilan Goodman Executive Producer: Alexandra Feachem A BBC Studios Audio Production

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 Sean Carroll - Professor of Natural Philosophy at Johns Hopkins University Peter Buist - Manager of the Galileo Reference Centre Richard Dyer - PhD student at the University of Cambridge

Producer: Ilan Goodman Executive Producer: Alexandra Feachem A BBC Studios Audio Production

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 Ben Garrod - Professor of Evolutionary Biology and Science Engagement at the University of East Anglia Martin Sander - Professor of Palaeontology at the University of Bonn

Producer: Ilan Goodman Executive Producer: Alexandra Feachem A BBC Studios Audio Production

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 Professor Manish Tiwari

Producer: Marijke Peters Executive Producer: Sasha Feachem

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 Greg Bryant - Professor of Communication at UCLA Betty La France - Professor or Communication, Northern Illinois University

Producer: Ilan Goodman Executive Producer: Alexandra Feachem A BBC Studios Audio Production

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: Professor Sarah Reece Professor Leslie Vosshall Professor John Pickett

Producer: Marijke Peters Executive Producer: Alexandra Feachem A BBC Studios Audio Production

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 Professor Will Dixon Professor Trevor Professor Trevor Harley

Producer: Marijke Peters Executive Producer: Alexandra Feachem

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 Phil Ayres - Professor of Biohybrid Architecture at the Royal Danish Academy Patrick Baptista Pinto - co-founder of Really Clever Maurizio Montalti - Co-founder and Chief Mycelium Officer of SQIM / MOGU Lynn Rothschild - Senior Research Scientist at NASA Ames research centre

Producer: Ilan Goodman Executive Producer: Alexandra Feachem A BBC Studios Audio Production

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 Dr Dean Burnett - honorary research fellow at Cardiff Psychology School, author of The Idiot Brain and The Happy Brain. Carmine Pariante - Professor of Biological Psychiatry at King’s College London

Producer: Ilan Goodman Executive Producer: Alexandra Feachem A BBC Studios Audio Production

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 Andrew Pontzen - Professor of Physics at Durham University Mitch Kenney - Assistant Professor in metamaterials at the University of Nottingham

Producer: Ilan Goodman Executive Producer: Sasha Feachem A BBC Studios Audio Production

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 Professor Richard Wiseman Professor Sophie van der Zee

Producer: Marijke Peters Executive Producer: Alexandra Feachem

A BBC Studios Audio Production

“Diamonds are nonsense!” Hannah boldly proclaimed in a previous episode. But listener Guy is a diamond enthusiast, and he and his diamond-loving pals were NOT OKAY WITH THIS. He demanded we re-open the case, and here we are...

SO in this glittering showdown, Dara is on a quest to flip Hannah’s perspective from “meh” to “marvelous.” And for Hannah, some uncomfortable facts soon emerge. It turns out that diamonds are much more than just overpriced bling. They're the secret ingredient in all sorts of high-tech gadgets with a whole arsenal of little-known superpowers.

Enter electrochemist Julie Macpherson, who blows Hannah’s mind by showing how diamonds can slice through ice like butter, thanks to their unmatched ability to conduct heat. Not impressed yet? Physicist Mark Newton makes a diamond glow in the dark, using nothing but his phone flashlight.

And that’s just to start! These ultra-robust gems can scrub nasty chemicals from water, serve as supercharged electrodes, and even reveal deep-earth secrets locked away for billions of years.

By the end of this episode, will Hannah finally admit diamonds are forever cool?

Contributors:

Charlie Bexfield - Gemmologist and diamond specialist Julie MacPherson - Professor of Chemistry at the University of Warwick Mark Newton - Professor of Physics at the University of Warwick Grahame Pearson - Professor of Earth Sciences from the University of Alberta

Producer: Ilan Goodman Executive Producer: Sasha Feachem A BBC Studios Audio Production

Hannah Fry and Dara Ó Briain return to tackle listener's questions with the power of science!

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