CrowdScience

What are the clouds like where you are? When you look upwards can you see great tufts of cotton wool, or do they stretch off into the distance, flat like sheets. Are they dark greys and purples, bringing the promise of rain or maybe there aren’t any at all. For listener John from Lincolnshire in the UK clouds looking up at the clouds is a favourite pastime and he wants to know why they look the way they do and why they are so different from one day to the next.Join Presenter Marnie Chesterton as we turn our gaze skyward to discover what gives clouds their shape. Join us for a cloud spotting mission with Gavin Pretor-Pinney, founder of the cloud appreciation society as he helps us de-code the shapes across the sky to reveal what they can tell us about our atmosphere. Dr Claire Vincent at the University of Melbourne introduces us to one of the superstars of the cloud world, Hector the Convector to explain where thunderstorms come from. And we learn how people like you can help NASA to understand the clouds better with Marilé Colón Robles project scientist at the GLOBE programme. Presented by Marnie Chesterton and Produced by Emily Bird[Image: Dramatic looking clouds. Credit: Getty Images]

As someone who dislikes crowds, listener Graham is curious about them. Crowds gather in all sorts of places, from train stations and football matches, to religious events and protest marches. But is there a science behind how they move and behave? To find out, Anand Jagatia speaks to some actual crowd scientists. He learns about the psychology of social identity, which influences everything from how close we stand to others to how we react in emergencies. He visits the Athens marathon, and hears about the algorithm that predicts how 50,000 runners will move through a city on race day. And he explores research into the science of riots, which explains why some peaceful crowds turn violent.Presented and produced by Anand JagatiaContributors: Dr Anne Templeton, University of Edinburgh Marcel Altenburg, Manchester Metropolitan University Prof John Drury, University of SussexArchive: BBC News Image: Crowd from above. Creidt: Getty Images

Why don’t we fall out of bed when we’re asleep? That’s the question that’s been keeping CrowdScience listener Isaac in Ghana awake, so presenter Alex Lathbridge snuggles up with some experts to find the answer.We get a lot of emails about sleep, so we’ve gathered together some of our favourite questions and put them to academics working on the science of snoozing.We’re wondering why some people laugh in their sleep, why some people remember their dreams and not others, and why we need to sleep at all - can’t we just rest?Our slumber scholars tell us about how our bodies continue to gather information while we’re asleep, how the tired brain is more likely to remember negative experiences, how we mimic other people in our sleep, and how sleep makes you more attractive to other people. And Alex takes a trip to the zzzzoo to meet some animals that have very different sleep patterns to humans. It’s his dream assignment.Contributors: Vanessa Hill, University of Central Queensland Professor Russell Foster, University of Oxford Mark Kenward, Drusillas Zoo ParkPresented by Alex Lathbridge Produced by Ben Motley for the BBC World Service[Image: Man Falling into bed. Credit: Getty Images]

After learning how long it will take the Earth's ice sheets to melt in the previous episode, we continue our journey in Greenland. As world leaders gather in Egypt for the annual UN climate conference, listener Johan isn't too optimistic about governments' ability to curb greenhouse gas emissions and get a handle on climate change. So from his coastal perch in Denmark, he has asked where we should live when the poles have melted away and coastlines creep inland.Along with the help of BBC correspondents around the world, Marnie Chesterton scours the globe for the best option for listener Johan's new home.BBC Mundo reporter Rafael Rojas takes us to a manmade island off Colombia's Caribbean coast to see how we might be able to live with the seas. Meanwhile, reporter Furkan Khan takes us into the high, cold desert region of Ladakh to see if heading for the hills might be the answer.As Marnie searches for a climate-proof destination, she speaks to conservation biogeographer Matt Fitzpatrick, from the Appalachian Laboratory at the University of Maryland Center for Environmental Science. He's made a map that shows what towns and cities will feel like in 60 years and where you should visit in order to get a preview of your home's future climate. But Matt also tells us that we might not be the only ones on the move.And as climate scientist Ruth Mottram from the Danish Meteorological Institute tells us, waters are not going to rise evenly around the world. So can Marnie find a place to go, away from the expanding seas?Additional contributors: Alexander Atencio, environmental sustainability teacher, Santa Cruz del Islote, Colombia Sebastian Martinez, local leader, Santa Cruz del Islote, Colombia Professor Mohammad Din, Ladakh Environment and Health Organisation Ellen and Carl Fiederickson, teacher and sheep farmers, Qassiarsuk, GreenlandPresenter: Marnie Chesterton Producer: Sam Baker

We know the Earth's atmosphere is warming and it's thanks to us and our taste for fossil fuels. But how quickly is this melting the ice sheets, ice caps, and glaciers that remain on our planet? That's what listener David wants to know. With the help of a team of climate scientists in Greenland, Marnie Chesterton goes to find the answer, in an icy landscape that's ground zero in the story of thawing. She discovers how Greenland’s ice sheet is sliding faster off land, and sees that the tiniest of creatures are darkening the ice surface and accelerating its melt. CrowdScience explores what we're in store for when it comes to melting ice. In the lead-up to yet another UN climate conference, we unpack what is contributing to sea level rise – from ice sheets in Greenland and Antarctica, to melting mountain glaciers and warming oceans. There's a lot of ice at the poles. The question is: how much of it will still be there in the future? Research Professor and climate scientist Jason Box from the Geological Survey of Denmark and Greenland shows us how much ice Greenland we've already committed ourselves to losing, even if we stopped burning all fossil fuels today. His team, including Jakob Jakobsen, show us how these scientists collect all this data that helps feed climate models and helps us all to understand how quickly the seas might rise.Professor Martyn Trantor from Aarhus University helps us understand why a darkening Greenland ice sheet would only add to the problem of melting. And climate scientist Ruth Mottram from the Danish Meteorological Institute breaks down how the ice is breaking down in Antarctica and other glaciers around the world.Presented by Marnie Chesterton and produced by Sam Baker for the BBC World ServiceImage: Greenland ice sheets. Credit: Getty Images

Record-breaking heatwaves swept across the Earth’s northern hemisphere this summer, while Australia experienced flooding and East Africa is enduring its worst drought in decades. Listener Geoff in Australia wants to know: Is climate change really responsible, or could it just be weather?Presenter Marnie Chesterton goes to Kenya, where the traditional Maasai way of life is at risk following a series of failed rainy seasons. She meets members of the Maasai community who have herded cattle for generations, who tell her how the unprecedented lack of rain is making it difficult to feed the animals, and themselves.She speaks to meteorologists and climate scientists to unpick the differences between weather and climate, discovering that not only is climate change affecting local weather systems, but it’s also affecting our ability to forecast it.She’ll also be learning about the IPCC report, and how there is no longer any doubt that climate change is a real and present threat to life on earth.Contributors: Esther Tinayo, Maasai villager Esther Kirayian, Maasai villager Patricia Nying’uro, Kenya Meteorological Department Abebe Tadege, IGAD Climate Prediction and Application Centre Professor Mark Maslin, University College LondonPresented by Marnie Chesterton Produced by Ben Motley, with Christine Yohannes, for the BBC World Service[Image credit: Getty Images]

Why do some people pick up accents without even trying, while others can live in another country for decades without ever losing the sound of their mother tongue? It’s a question that's been bothering CrowdScience listener Monica who, despite 45 years of living in the US, is still answering questions about where her accent is from. Presenter Marnie Chesterton sets off to discover why learning a new language is possible but perfecting the accent is so much harder. Marnie speaks to a linguist about how we learn language and develop our first accent, and what we can - and can't change - about our accents. A phonetician explains to Marnie the difficulty of even hearing sounds that are not from our mother tongue, let alone replicating them. And Marnie enlists some expert help to learn some of the pitch sounds of Japanese – with mixed success.Finally Marnie asks why people so dearly want to change their accents when doing so is such hard work. She hears from a sociolinguist about stereotypes and the impact of accent bias, and Shalu Yadav reports from the front line of Delhi call centres where workers experience prejudice about their accents regularly. Presented by Marnie Chesterton Produced by Lorna Stewart for the BBC World Service. Contributors: Yosiane White - Assistant Professor of Linguistics at University College Utrecht in the Netherlands Jane Setter - professor of phonetics at the University of Reading in the UK Akiko Furukawa - Reader in Japanese and Applied Linguistics at SOAS University of London in the UK Erez Levon - professor of sociolinguistics at the University of Bern in Switzerland. Shalu Yadav - BBC reporter in Delhi, India.[Image: woman with written words coming out of mouth. Credit: Getty images]

One in every eight people live with a mental health disorder, so if that’s not you, it’s likely to be a close friend or family member. Despite there being a variety of known treatments, globally the majority of people suffering do not receive any medical support.To see how the discussion around mental health is playing out across the African continent, CrowdScience visits Nairobi, Kenya. Presenter Marnie Chesterton is joined by a live audience and panel of experts - psychiatrist David Ndetei, psychotherapist Reson Sindiyo and mental health journalist Dannish Odongo - to get to the heart of what’s going on in our heads.They discuss issues from taboo and superstition around mental health, to the treatment methods being used in Kenya that the rest of the world should know about.

Human sexuality comes in many forms, from exclusively heterosexual to exclusively homosexual. But seeing as homosexuality creates apparent reproductive and evolutionary disadvantages, listener Ahmed from Oslo wants to know: why are some people gay?CrowdScience presenter Caroline Steel examines what science can - and can't - tell us about the role of nature, nurture and evolution in human sexual attraction. She asks a geneticist what we know of the oft-debated 'gay gene', as well as looking into why homosexual men on average have more older brothers than heterosexual men.Caroline looks into the role of nurture with a developmental psychologist to answer a question from a CrowdScience listener from Myanmar. He wonders if the distant relationship he has with his own father has impacted his own feelings of attraction.She also learns about research into a group of people in Samoa who may shed light on the benefits of traditionally non-reproductive relationships for communities as a whole.Presented by Caroline Steel Produced by Jonathan Blackwell for BBC World ServiceContributors: Dr. Kevin Mitchell - Associate Professor of Genetics and Neuroscience, Trinity College Dublin Dr. Malvina Skorska - Postdoctoral Fellow at the Centre for Addiction and Mental Health, Toronto Prof. Lisa Diamond - Professor of Psychology and Gender Studies, University of Utah Prof. Paul Vasey - Professor and Research Chair, Department of Psychology, University of Lethbridge Vaitulia Alatina Ioelu - Chief Executive Officer, Samoa Business Hub(Photo credit: Ahmed Umar)

There are over 30,000 species of fish – that’s more than all the species of amphibians, reptiles, birds and mammals combined. But despite the sheer diversity of life on Earth, we still tend to think of all fish in roughly the same way: with an oblong scaley body, a tail and pairs of fins. Why? And is that really the case? Crowdscience listener and pet fish-owner Lauria asked us to dive into the depths of this aquatic world to investigate why fish are shaped the way they are. Do we just think that fish are all the same because we are land-dwelling? Presenter Anand Jagatia makes a splash exploring the fascinating story of fish evolution, how they came to be such a different shape from mammals and even how some mammals have evolved to be more like fish.Produced by Hannah Fisher and presented by Anand Jagatia for the BBC World Service. Contributors: Professor Frank Fish – Professor of Biology, West Chester University Dr Carla McCabe - Lecturer in Sport & Exercise Biomechanics Dr Andrew Knapp – postdoctoral researcher at the Natural History Museum, London Image: School of fish in shape of fish. Credit: Getty Images

CrowdScience listener Alix has a burning question - what’s actually happening inside the flames of a campfire to make it glow? And why do some materials burn easily, while others refuse to light at all?To find out, Alex Lathbridge travels to the Fire Research Centre at the University of Edinburgh to (safely) set various things ablaze. He learns about the fundamentals of fire and why things react differently to heat. He then heads to archives of the Royal Institution of London, to see an invention from the 19th century that can stop a fireball in its tracks: the miner’s safety lamp, which saved countless lives. And he speaks to a chemist about the science of flame retardants, and how even though they can make products less flammable, they may also have unintended consequences.Presenter: Alex Lathbridge Producer: Anand JagatiaContributors: Dr Rory Hadden, University of Edinburgh Charlotte New, Royal Institution Dan Plane, Royal Institution Professor Richard Hull, University of Central Lancashire

Laugh and the world laughs with you, or so you might think. But watch any good comedian on TV by yourself and chances are you’ll laugh a lot less than if you were sat in a lively comedy crowd watching the same comedian in the flesh. But why is that? Do people from different cultures and corners of the world all laugh at the same things? These are questions raised by CrowdScience listener Samuel in Ghana who wonders why he’s always cracking up more easily than those around him. Presenter Caroline Steel digs into whether it’s our personality, the people around us, or the atmosphere of the room that determines how much we giggle, following neuroscience and psychology on a global trail in search of a good laugh. Producer: Richard Walker Presenter: Caroline Steel [Image: Two Women laughing. Credit: Getty Images]

Mathematics and our ability to describe the world in terms of number, shape and measurement may feel like a uniquely human ability. But is it really? Listener Mamadu from Sierra Leone wants to know: can animals count too? CrowdScience presenter Marnie Chesterton goes on a hunt to uncover the numerical abilities of the animal kingdom. Can wild lions compare different numbers? Can you teach bees to recognise and choose specific amounts? And if the answer is yes, how do they do it? Marnie tries to find out just how deep the numerical rabbit hole goes… and comes across a parrot named Alex who is perhaps the most impressive example of animal counting of them all.Contributors: Brian Butterworth - emeritus professor of cognitive neuropsychology at University College London Mai Morimoto - researcher at Queen Mary University of London Lars Chittka - professor of sensory and behavioural ecology at Queen Mary University of London Irene Pepperberg - comparative psychologist, and research associate at Harvard UniversitySounds: Lions from Karen McComb, emeritus professor at University of Sussex Túngara frogs from Michael Ryan, professor of zoology at University of Texa at AustinPresenter: Marnie Chesterton Producer: Florian Bohr

When CrowdScience listener Eric spotted a few gnats flying around on a milder day in mid-winter it really surprised him - Eric had assumed they just died out with the colder weather. It got him wondering where the insects had come from, how they had survived the previous cold snap and what the implications of climate change might be for insect over-wintering behaviour? So he asked CrowdScience to do some bug investigation. CrowdScience presenter Marnie Chesterton takes up the challenge and heads out into the British countryside – currently teeming with buzzes and eight legged tiny beasties - to learn about the quite amazing array of tactics these small creatures use to survive the arduous days of cold. She hears how some insects change their chemical structure to enhance their frost resistance whist others hanker down in warmer microclimates or rely on their community and food stocks to keep them warm. But cold isn’t the only climatic change insects have to endure, in the tropics the seasons tend to fluctuate more around wet and dry so what happens then? Marnie talks with a Kenyan aquatic insect expert who describes how mosquitoes utilise the rains and shares his worry climate change could have a big impact on insect populations.Contributors: Dr Erica McAlister – Entomologist and Senior Curator, Natural History Museum, Dr Adam Hart – Entomologist and Professor of Science Communication - University of Gloucestershire Fran Haidon – Beekeeper Laban Njoroge – Entomologist, head of the Invertebrate Zoology – Museum of Kenya Dr Natalia Li – Biochemist Presenter: Marnie Chesterton Producer: Melanie Brown[Image: Butterfly in winter resting on snow covered branch. Credit: Getty Images]

Have you ever wondered why waterfalls appear white when still water is transparent? Why clouds, or snow, appear white when they too are essentially just water molecules in different states? What makes something white, opaque or transparent? These are the questions CrowdScience listener Gerardo has been pondering ever since taking in the beauty of fallen water on a hiking trail in his home of Cantabria, Northern Spain. Presenter Marnie Chesterton, sets off on a quest to find out the answers to all of those questions and more. What even is white? Is it a colour, the absence of colour or all the colours of the rainbow combined? Is black really the opposite of white? And what colours do we mix to make white or black paint?Image: White paint in pots and a paintbrush. Credit: Getty Images

Imagine waking up to the smell of freshly baked bread. Doesn’t it make your mouth water? Now imagine the smell of a fish market on a warm day… still feeling hungry? CrowdScience listener Thanh from Vietnam is intrigued by the effects of smell on our appetite, and wants to know whether certain aromas can make us feel more full than others. Never averse to a food-based challenge, presenter Anand Jagatia takes us on a journey from the nose to the brain, where we find out what exactly happens when we get a whiff of various foods. He discovers how the digestive system prepares for a meal and the extent to which our stomach has a say in whether or not we want to eat, based on how appetizing the smells are around us. Anand also explores our cultural differences. In some parts of the world a stinky Limburger cheese is considered a delicacy, while in other places it could make people lose their lunch. We’ll find out why some of us get triggered in different ways than others.

From dumping raw sewage into rivers to littering the streets with our trash, humans don’t have a great track record when it comes to dealing with our waste. It’s something that CrowdScience listener and civil engineer Marc has noticed: he wonders if humans are particularly prone to messing up our surroundings, while other species are instinctively more hygienic and well-organised.Are we, by nature, really less clean and tidy than other animals? Farming and technology have allowed us to live more densely and generate more rubbish - maybe our cleaning instincts just aren’t up to the vast quantities of waste we spew out? CrowdScience digs into the past to see if early human rubbish heaps can turn up any answers. We follow a sewer down to the River Thames to hear about The Great Stink of Victorian London; turn to ants for housekeeping inspiration; and find out how to raise hygiene standards by tapping into our feelings of disgust and our desire to follow rules.Presented by Marnie Chesterton and produced by Cathy Edwards for the BBC World Service.[Image: Man on beach with rubbish. Credit: Getty Images]

You have probably experienced an ‘earworm’ - a catchy bit of music that plays round and round in your head and won’t go away – at least for a short while. But why did it pop up in the first place and how did it get stuck?CrowdScience listener Ryota in Japan wants us to dig into earworms, so presenter Datshiane Navanayagam bravely puts on her headphones to immerse herself in the world of sounds that stick. She meets with a composer of children’s songs as well as music psychologists to find out if there is a special formula to creating catchy songs and probes if this musical brain quirk serves any useful purpose. Datshiane then explores whether some people are more prone to catching earworms than others. Finally, for those who find this phenomenon disturbing - she asks is there a good way of getting rid of them? Come join us down the audio wormhole - disclaimer - the BBC is not responsible for any annoying earworms caused by this broadcast.Presented by Datshiane Navanayagam and produced by Melanie BrownInterviewees: Kelly Jakubowski – Assistant Professor in Music Psychology, Durham University Bill Sherman – Musical Director of Sesame Street Ashley Burgoyne – Computational Musicologist, University of Amsterdam[Image: Audio Cassette. Credit: Getty Images

We are running out of ammunition against certain infections, as bacteria increasingly evade the antibiotics we’ve relied on for nearly a century. Could bacteriophages – viruses that hunt and kill bacteria – be part of the solution?In 2019, CrowdScience travelled to Georgia where bacteriophages, also known as phages, have been used for nearly a hundred years to treat illnesses ranging from a sore throat to cholera. Here we met the scientists who have kept rare phages safe for decades, and are constantly on the look-out for new ones. Phages are fussy eaters: a specific phage will happily chew on one bacteria but ignore another, so hunting down the right one for each infection is vital.Since then, we’ve lived through a pandemic, the medical landscape has been transformed, and interest in bacteriophages as a treatment option is growing throughout the world. We turn to microbiologist Professor Martha Clokie for updates, including the answer to listener Garry’s question: could phages help in the fight against Covid-19?Contributors: Prof Martha Clokie, University of Leicester Dr Naomi Hoyle, Eliava Phage Therapy Center Prof Nina Chanishvili, Eliava Institute Dr Eka Jaiani, Eliava InstitutePresented by Marnie Chesterton Produced by Cathy Edwards and Louisa Field for the BBC World Service[Photo:Bacteriophages infecting bacteria, illustration. Credit: Getty Images]

Artists can conjure up people, cities, landscapes and entire worlds using just a pencil or a paintbrush. But some of us struggle to draw simple stick figures or a circle that’s round. CrowdScience listener Myck is a fine artist from Malawi, and he’s been wondering if there’s something special about his brain.Myck takes Marnie Chesterton on a tour of his studio, where he paints onto huge canvases sewn from offcuts of local fabric. He’s a self-taught artist and he’s convinced he sees things differently to other people. So where does that all come from? Do artists have different brains from non-artists? And what is it that makes someone a creative person, while others are not? With the help of a jigsaw puzzle, a large metal donut, a swimming cap covered in electrodes and and a really boring brick, Marnie probes the brains of people working to find answers to those questions. She’ll be learning about how we don’t really see what we think we see, why creative people’s brains are like private aeroplanes, and how daydreaming can be a full time job.Contributors: Rebecca Chamberlain, Goldsmiths University of London Robert Pepperell, Cardiff School of Art Ariana Anderson, UCLA Darya Zabelina, University of ArkansasPresented by Marnie Chesterton Produced by Ben Motley for the BBC World Service

Hair is an important part of our identities – straight, frizzy, long, not there at all – and our efforts to keep it styled and clean have created an $80 billion hair care industry. Many products offer to improve the life of the stuff on our heads, but isn't it all just dead protein?CrowdScience listener Toria wants to know what 'healthy' hair really means. To untangle the science behind hair, we zoom in to see how hair grows from the follicles in our scalp and explore how the hair growth process will change over our lifetimes.Changes in our hair and disorders affecting the scalp can often have emotional impacts on our lives, as presenter Marnie Chesterton learns from a dermatologist who specialises in hair issues.Having been on a journey with her own hair in recent years following chemotherapy, Marnie is ready for a new 'do and ventures to the hair salon to find out about the health of her own hair.Meanwhile, another CrowdScience listener, Lucy, wonders why humans lost hair (or fur) on most of our bodies when most other mammals are covered in the stuff. A biological anthropologist who studies not only why hair became concentrated on our heads, but also why there's so much diversity in hair types across humans, unpacks the evolutionary benefits.With all these different hair types, does different hair need different care? And when it comes to shampoo, conditioner, washing, blowdrying and dyeing, what should we be doing to keep our hair structure sound?As we learn about this strange nonliving feature of our bodies, Marnie finds a new appreciation for the "dead strands of protein sticking out of our skin". And with listener Toria's help and advice, she also finds a new shade for her chemo-curled locks.Presented by Marnie Chesterton and produced by Sam Baker for BBC World Service.Featuring:● Tina Lasisi, Penn State Department of Anthropology ● Sharon Wong, Consultant Dermatologist ● Ekwy Chukwuji-Nnene, Equi Botanics

Death is inevitable, though many of us would rather not dwell on it. For those with a terminal illness, however, the end of life is clearly a more pressing reality.CrowdScience listener Sam has known for a while that her illness is terminal, and by now she’s got used to the idea. But she finds many friends and family would rather avoid the subject at all costs; they don’t want to acknowledge what’s happening until it’s all over. She’s wondering if there’s a way to lighten up the topic of her approaching death, and create the openness she craves.If we could learn to be more accepting of illness and dying, the end of life could be a more positive experience for all involved. So how can we face up to the impending death of a loved one, and best support that person in the process? In search of answers, we talk a clinical psychologist about death anxiety, visit a death café, and learn about a scheme in India where whole communities are trained in caring for people at the end of life.With Dr Rachel Menzies, Abigail Griffin, Dr Suresh Kumar and Rebecca Nellis. Thanks to Lola, Juan, Leon, Qayyah, Bessy, Madhumita, Ashley, Amaru, Mila and Sheila.Presented by Caroline Steel Produced by Cathy Edwards for the BBC World Service[Image: A woman sitting next to her sister who has cancer. She is wearing a headscarf. Credit: Getty Images]

Every year, new computers are being developed that are faster and smarter than ever before. But if you really want to take things to the next level, you've got to go quantum. CrowdScience listener Atikah in Hungary likes the sound of a quantum computer but wants to know: what exactly is it, what can it do that a normal computer can't, and how soon can she get hold of one?The digital devices in our everyday lives - from laptop computers to smartphones - are all based on 0s and 1s: so-called ‘bits’. But quantum computers are based on ‘qubits’ - the quantum 0s and 1s that are altogether stranger, but also more powerful. With the help of quantum computing researcher Jessica Pointing and a spinning doughnut, presenter Alex Lathbridge learns how these ‘qubits’ allow computers to perform calculations millions of times faster than normal.While quantum computers do exist, it turns out they're not yet big enough or stable enough to be really useful. Alex visits Professor Winfried Hensinger and his prototype quantum computer at the University of Sussex to understand what they can do right now, and why it’s so incredibly difficult to scale them up. He hears from the engineers racing to overcome the obstacles and unlock the potential of these mega-powerful systems.But once the engineering problems are solved, what then? Professor Shohini Ghose opens our eyes to the exciting range of possible applications - from helping create new drugs, to making electric batteries much more efficient and maybe even helping farmers fertilise their crops for a fraction of the price.Contributors - Jessica Pointing, Professor Winfried Hensinger, Professor Shohini Ghose Presenter - Alex Lathbridge Producer - Ilan Goodman Sound Design - Jon Nicholls[Image: Winfried Hensinger in his lab at the University of Sussex, Credit: Universal Quantum]

Humans can walk for miles, solve problems and form complex relationships using the energy provided by daily meals. That is a lot of output for a fairly modest input. Listener Charlotte from the UK wants to know: how efficient are humans? How do they compare to cars, other animals and even to each other? Presenter Marnie Chesterton pits her energetic self against everything from cars to rabbits to find out how she shapes up. Marnie also explores whether humans are born equal when it comes to fuel efficiency. Does the energy from one banana get converted into the same amount of movement from person to person? Marnie gets on a treadmill to find out how efficient she really is. With contributors from Herman Pontzer, Duke University, Rhona Pearce, Loughborough University and Christian Gammelgaard Olesen from Wolturnus wheelchair manufacturing company.Presenter: Marnie Chesterton Producer: Caroline Steel Editor: Richard Collings Production co-ordinator: Jonathan HarrisArt Design: Jonathan HarrisImage credits: Airplane: Credit: Ghrzuzudu Creative #:1337512445 Red car: Credit: EgudinKa Creative #:625457854 Wheelchair Woman: Credit: Ponomariova_Maria Creative #:1401730072 Getty Images

This week’s CrowdScience is dedicated to bodily fluids – and why humans spend so much time spraying them all over the place. From snot and vomit to sweat and sneezes, listeners have been positively drenching our inbox with queries. Now presenter Marnie Chesterton and a panel of unsqueamish expert guests prepare themselves to wade through… One listener has found that as he ages, bright light seems to make him sneeze more and more – with his current record sitting at 14 sneezes in a row. He’d like to know if light has the same effect on other people and why? Sticking with nasal fluids, another listener wants to know why she’s always reaching for a tissue to blow her endlessly dripping nose and yet her family seem to produce hardly any snot at all. Could it be because she moved from a hotter climate to a colder one? CrowdScience reveals the answers to these and other sticky questions… if you can find the stomach to listen. Produced by Melanie Brown Contributors: Jagdish Chaturvedi – ENT Surgeon Åsmund Eikenes – Author Prof. Lydia Bourouiba - Associate Professor of Civil and Environmental Engineering, MIT Rubiaya Hussain – PhD student, optics and photonics, ICFO[Image: Woman sneezing. Credit: Getty Images]

If you go outside with a spade and start digging, the chances are you won't find any gold. You might get lucky or just happen to live in a place where people have been finding gold for centuries. But for the most part, there'll be none. But why is that? Why do metals and minerals show up in some places and not others?It's a question that's been bothering CrowdScience listener Martijn in the Netherlands, who has noticed the physical effects of mining in various different places while on his travels. It’s also a really important question for the future – specific elements are crucial to modern technology and renewable energy, and we need to find them somewhere.Marnie Chesterton heads off on a hunt for answers, starting in a Scottish river where gold can sometimes be found. But why is it there, and how did it get there? Marnie goes on a journey through the inner workings of Earth's geology and the upheaval that happens beneath our feet to produce a deposit that’s worth mining.On the way she discovers shimmering pools of lithium amongst the arid beauty of the Atacama Desert, meets researchers who are blasting rocks with lasers and melting them with a flame that’s hotter than the surface of the sun, and heads to the bottom of the ocean to encounter strange potato-sized lumps containing every single element on Earth.And maybe, just maybe, she’ll also find gold.Contributors: Leon Kirk, gold panning expert Holly Elliott, University of Derby Jamie Wilkinson, Natural History Museum, London Corrado Tore, SQM, Chile Yannick Buret, Natural History Museum, London Andrea Koschinsky, Jacobs University, BremenPresented by Marnie Chesterton Report by Jane Chambers Produced by Ben Motley for the BBC World Service[Image: Hands holding Gold Nuggets. Credit: Getty Images]

Digging and excavating are bywords for archaeology. But why does history end up deep under our feet?This question struck CrowdScience listener Sunil in an underground car park. Archaeological remains found during the car park’s construction were displayed in the subterranean stairwells, getting progressively older the deeper he went. How had these treasures become covered in so much soil over the centuries?CrowdScience visits Lisbon, the capital of Portugal – and home to the above-mentioned multi-storey car park. The city has evidence of human habitation stretching back into prehistory, with remnants of successive civilisations embedded and jumbled up below today’s street level. Why did it all end up like this?Human behaviour is one factor, but natural processes are at work too. Over at Butser Ancient Farm, an experimental archaeology site in the UK, we explore the myriad forces of nature that cover up – or expose - ancient buildings and artefacts over time.Contributors:Dr Mariana Nabais, University of Lisbon Carolina Grilo, Lisbon Museum of the Roman Theatre Dr Matt Pope, University College LondonPresented by Marnie Chesterton, Produced by Cathy Edwards for the BBC World Service. IMAGE: Getty Images

Most people are great at remembering key points from important events in their lives, while the finer details - such as the colour of the table cloth in your favourite restaurant or the song playing on the radio while you brushed your teeth - are forgotten. But some people seem to have the power to remember events, documents or landscapes with almost perfect recall, which is widely referred to as having a photographic memory. Crowdscience listeners Tracy and Michael want to know if photographic memory actually exists and if not, what are the memory processes that allow people to remember certain details so much better than others? Putting her own memory skills to the test along the way, presenter Marnie Chesterton sets out to investigate just what’s happening inside our brains when we use our memories, the importance of being able to forget and why some people have better memories than others.Produced by Hannah Fisher and presented by Marnie Chesterton for the BBC World Service.Contributors: Stephen Wiltshire Annette Wiltshire Dr Farahnaz Wick Professor Craig Stark[Image credit: Getty Images]

Humans now have the ability to directly change their DNA, and gene-editing tool CRISPR has led to a new era in gene-editing. CrowdScience listener ‘Bones’ wants to know how gene-editing is currently being used and what might be possible in the future.Gene-editing offers huge opportunities for the prevention and treatment of human diseases, and trials are currently underway in a wide range of diseases like sickle cell anaemia. CrowdScience presenter Caroline Steel finds out about some of the most promising work tackling disease before turning to consider the possibilities of using gene editing to enhance ourselves.Will we be able to extend human longevity, swap our eye colour or improve athletic performance? And even if we can do all these things, should we?As scientists push the boundaries of gene-editing and some people are DIY experimenting on themselves with CRISPR, we discuss the practical and ethical challenges facing this promising but potentially perilous area of science.Produced by Melanie Brown and presented by Caroline Steel for the BBC World Service Contributors: Prof George Church Prof Waseem Qasim Jimi Olaghere Josiah Zayner Prof Joyce harper Prof Julian Suvalescu

How do we stay up when we ride a bicycle? Lots of us can do it without even thinking about it, but probably very few of us can say exactly HOW we do it. Well, CrowdScience listener Arif and his children Maryam and Mohammed from India want to understand what’s going on in our heads when go for a cycle, and how we learn to do it in the first place.Presenter Marnie Chesterton is on the case, tracking down a neuroscientist studying how our brains and bodies work together to keep us balanced whether we’re walking or trying to ride a bicycle. She learns about the quirks of bicycle engineering from researchers in the Netherlands who are part of a lab entirely devoted to answering this question. In the process falling off of some unusual bicycles and uncovering the surprising truth that physics might not yet have a proper answer. And we peer deeper into our brains to find out why some memories last longer than others, whether some people can learn quicker than others and the best way to learn a new skill. Presented by Marnie Chesterton and Produced by Emily Bird for the BBC World Service.Featuring: Kathleen Cullen, Johns Hopkins University, USA Jason Moore, University of Technology Delft, The Netherlands Lara Boyd, University of British Columbia, Canada Rado Dukalski, University of Technology Delft, The Netherlands Josie and Freesia, Pedal Power

The ancient Maya flourished in modern day Mexico and Central America for millennia. They built incredible cities and they had sophisticated knowledge of astronomy, architecture and the natural world. But although Maya culture continues to exist today, around 900 AD, many of their great settlements collapsed, and today they lie in ruins. CrowdScience listener Michael wants to know - how did the Maya sustain their populations successfully for so long? And what happened 1000 years ago that led them to abandon their cities?To find out, presenter Melanie Brown travels to the forests of Western Belize. She visits the archaeological site of Xunantunich to learn about what life would have been like for the Maya living in what was once a prosperous city. She hears about the importance of water to the Maya way of life in this region, and their ingenious methods for capturing and storing rainfall. She meets archaeologists using lasers and drones to map Maya settlements that have lain hidden by jungle for centuries. And she discovers what material from the bottom of lakes can tell us about how the Maya faced a changing climate, which may have had huge consequences for their society.This episode is being released on Earth Day 2022. As we face an uncertain future of our own amid a climate crisis, are there any lessons we can learn from the Maya about how to live sustainably on this planet? Presented by Melanie Brown and produced by Anand JagatiaFeaturing: Elias Cambranes, Maya expert and tour guide Prof Lisa Lucero, University of Illinois Urbana-Champaign Prof Tim Murtha, University of Florida Dr Eben Broadbent, University of Florida Prof Mark Brenner, University of FloridaPhoto: Ancient ruins of the Mayas deep in the forest of Belize Credit: Simon Dannhauer/Getty Images

The team at CrowdScience have spent years answering all sorts of listener questions, which must make them pretty smart, right? IN this week’s episode, that assumption is rigorously tested as Marnie Chesterton and the team pit their wits against a multitude of mindbending puzzles from an old TV gameshow - all in the name of answering a question from Antonia in Cyprus. She wants to know: how do we work out how clever someone is? Is IQ the best measure of cleverness? Why do we put such weight on academic performance? And where does emotional intelligence fit into it all?In the search for answers, presenter Marnie Chesterton and the team are locked in rooms to battle mental, physical, mystery and skill-based challenges, all against the clock. Unpicking their efforts in the studio are a global team of cleverness researchers: Dr Stuart Ritchie from Kings College London, Professor Sophie von Stumm from York University and Dr Alex Burgoyne, from Georgia Institute of Technology in the US. They are challenged to face the toughest questions in their field: Why do men and women tend to perform differently in these tests? Is our smartness in our genes? And what about the Flynn effect – where IQs appear to have risen, decade after decade, around the world. Produced by Marnie Chesterton on BBC World Service [Image: Man doing puzzle. Credit: Getty Images]

The odds of becoming a fossil are vanishingly small. And yet there seem to be an awful lot of them out there. In some parts of the world you can barely look at a rock without finding a fossil, and museum archives worldwide are stuffed with everything from ammonites to Archaeopteryx. But how many does that leave to be discovered by future fossil hunters? What’s the total number of fossils left to find? That’s what listener Anders Hegvik from Norway wants to know and what CrowdScience is off to investigate. Despite not having the technology or time to scan the entire planet, presenter Marnie Chesterton prepares to find a decent answer. During her quest, she meets the scientists who dig up fossils all over the world; does some very large sums; and asks, have we already found all the T-rexes out there?Presented by Marnie Chesterton and produced by Anna Lacey(Photo: Fossilized dinosaur bones and skull in the send. Credit: Getty Images)

Many animals undertake remarkable migratory journeys; travelling thousands of miles only to return to same burrow or beach they departed from. Yet, unlike humans, they don’t have digital or paper maps to guide their way, so how are they able to orientate themselves with such accuracy?In the second part of this migration story, CrowdScience’s Anand Jagatia explores how animals are able to navigate using the sun, stars, smells, landmarks and magnetism to help guide them. Anand journeys to the coast of Florida where he helps to place a satellite tracker on a sea turtle in order to follow the long-distance journeys of these animals. He then visits a lab in North Carolina to meet a team that is recreating the earth’s magnetic fields to examine how sea turtles might be using these forces to find their feeding and nesting grounds.Anand wades into the hotly contested topic of just how birds may be sensing magnetic fields – and hears about one of the latest theories that suggests birds eyes may be exploiting quantum physics. The range of navigational tools we encounter throughout the animal kingdom from whales to ants is beguiling, Anand asks what does our increased understanding of these feats might mean for animal conservation as well as human development of mapping systems.Contributors: David Godfrey – Sea Turtle Conservancy Rick Herren – University of Florida Tim Guilford – University of Oxford Ken Lohmann – University of North Carolina Kayla Goforth – University of North Carolina Henrik Mouritsen – University of Oldenburg(Photo: Sea Turtles. Credit: Getty Images)

Wherever you are in the world you are probably near an animal that has undertaken a remarkable migratory journey, be that a butterfly, bird or sea turtle. But what CrowdScience listener Moses in Kenya wants to know is why they bother making such long and precarious voyages - and how they're able to reliably navigate over hundreds and sometimes even thousands of miles. In this first of two episodes, presenter Anand Jagatia travels to the Americas to meet the scientists finding and tracking these animals in order to solve the puzzle of where they go and why.Deep in the lush and noisy Belizean jungle, Anand joins avian biologist Abidas who is collecting data on the beautiful birds that visit tropical forests to escape harsh winters. Here, using misting nets, Abidas and her team carefully catch birds to measure their health and status before tagging and releasing them so they can continue stocking up on jungle food. Anand finds out why having long term data on migrant birds can help in understanding why some birds, like the wood thrush, have been declining in their native homes further north.Anand then jumps aboard a turtle boat in Florida where scientists from the Sea Turtle Conservancy have been collecting data on these dinosaur-like creatures. But finding them is harder it might seem. They move fast, so Anand accompanies the research team who are experienced in safely catching them, will he be lucky and find one of these magnificent creatures?Presented by Anand Jagatia and produced by Melanie BrownContributors: David Barrie – Navigator & author Tim Guilford – University of Oxford Abidas Ash – University of Belize Kristen Ruegg - Colorado State University David Godfrey – Sea Turtle Conservancy[Image credit: BBC Staff, Melanie Brown]

Faced with one cake and eight hungry people, it’s pretty obvious how maths underpins reality. But as mathematics gets further from common sense and into seemingly abstract territory, nature still seems to obey its rules - whether in the orbit of a planet, the number of petals on a flower, or the structure of an atom.But what exactly is the relationship between mathematics and reality? That’s the impossibly difficult question CrowdScience has been set this week by our listener Sergio in Peru. It’s one that’s been pondered by humans for millennia: the Greek philosopher Pythagoras believed “All is number”.Is maths a human construct to help us make sense of reality - a tool, a model, a language? Does maths create its own reality? Or is it reality itself?CrowdScience explores these questions with the help of experts from the fields of philosophy, mathematics and science: Dr Eleanor Knox, Dr Eugenia Cheng, Professor Lucie Green, Alex Bellos and Stefano Centineo.Presenter: Marnie Chesterton Produced by Cathy Edwards for the BBC World Service(Photo: A young woman with her eyes closed standing in front of chalkboard, working out maths formulas. Credit: Getty Images)

Massage has been used for thousands of years to soothe our aches and pains and help us relax. Today there are a wide array of styles to choose from – Swedish massage, deep tissue, hot stone, sport, Thai, the list goes on. But which techniques are backed up by evidence?CrowdScience listeners Catherine and Stacy are keen for us to untangle this knotty issue, so presenter Caroline Steel selflessly ventures from her desk to the massage table all in the name of science.Is there such thing as a muscle 'knot' and can massage help to get rid of them? Does lactate build up in our muscles and need to be released? And why does rubbing sore muscles feel so good? We dig into the physiological and psychological aspects of what's happening in our bodies when we get a massage.With scientists only beginning to study massage in recent decades, we put the research to the test with our many questions and even a bit of myth-busting. Can massage help us avoid injury or recover faster when we exercise? Does drinking water after a massage flush out toxins? Is self-massage or massage from a friend or family member just as good as that from a professional massage therapist? Can children benefit from massage?Caroline talks to medical professionals and experts to find out what works when it comes to treating a stiff neck and tight muscles and unpacks the importance of touch in relieving the tensions of modern life.Presented by Caroline Steel and produced by Sam Baker for BBC World Service. Featuring: ● Cecillia Ljunggren, London School of Massage ● Mark Tarnopolsky, McMaster University ● Tiffany Field, Touch Research Institute, University of Miami Health System ● Wichai Eungpinichpong, Department of Physical Therapy, Khon Kaen University[Image credit: Getty Images]

If you took a fly into a really tall elevator and let it out at the top, would it still be able to fly? And what’s the absolute highest an insect could possibly go? It’s a question that’s been bugging CrowdScience listener Chee for a while, but presenter Alex Lathbridge is on the case. He discovers that when they’re not buzzing around your lunch, insects can be routinely found flying high up in the atmosphere travelling from A to B. There are also ground-dwelling bumblebees living in the mountains of Sichuan, China that have demonstrated an ability to fly at altitudes higher than the highest point on the planet. But leaving aside how high insects DO fly, how high COULD they fly if given the chance? Alex explores the theoretical limits of insect flight with the help of a bit of biomechanics – before contemplating the ultimate heights of the International Space Station where the mystery of whether a fruit fly will fly in zero gravity is finally answered. Contributors: Jason Chapman, University of Exeter Inés Dawson, science youtuber and expert in insect flight biomechanics Michael Dillon, University of Wyoming Wes Shaw, Head Gardener, Sky Garden Sharmila Bhattacharya, NASAPresented by Alex Lathbridge Produced by Ben Motley for the BBC World Service[Photop credit: Getty Images]

Controlling fire was a turning point in the development of human civilisation. But how did fire become part of the human toolkit? It's a question that has got Crowdscience listener Joseph wondering. He wants to know how humans first made fire and how that knowledge spread around the world, eventually developing into our industrial civilisations today. Archaeologists have many different ideas and theories about this. Did humans learn the skill millions of years ago, and carry it with them as they migrated out of what is now Africa? Or was it a skill developed much later, after different groups had settled in different locations? Did people share the skill with each other or did different groups of people discover it individually?Marnie Chesterton speaks to experts to try to piece together the archaeological clues to discover what kindled humankind's relationship with fire and flame. She hears about the early evidence of fire from Anand Jagatia, who visits Wonderwerk Cave in South Africa, and she speaks to an archaeologist who has found remains of burned flint suggesting campfire locations dating back hundreds of thousands of years in Israel. Marnie also tries her hand at making fire, Neanderthal style. Contributors: Dr Andrew Sorensen, Leiden University Prof Nira Alperson-Afil, Bar-Ilan University Prof Richard Wrangham, Harvard University Dr David Morris, McGregor Museum Candice Koopowitz, Simon Fraser University Dr Katharine MacDonald, Leiden University Presented by Marnie Chesterton and Produced by Hannah Fisher for BBC World ServiceImage Credit: Getty Images

How good are you at finding your way from A to B? Humans throughout history have used all sorts of tools to get us to our destination – from a trusty map and compass to the instant directions on a smartphone. But CrowdScience listener Pam from Florida wants to know what happens when we leave the surface of the Earth and try to navigate our way around space. Is there a North and South we can use to orientate ourselves? Which way is left if your nearest landmark is a million light years away? And if you can’t tell which way is up, how do spacecraft know where they’re going? Presenter Anand Jagatia speaks to experts in an attempt to find his way through the tricky problem of intergalactic space navigation.Contributors: Ethan Siegal, journalist and astrophysicist Michelle Baker, ESA Coryn Bailer-Jones, Max Planck Institute for Astronomy Presented by Anand Jagatia Produced by Caroline Steel for the BBC World Service

Climate change and biodiversity loss are two of the biggest threats humanity has ever faced - and tackling them is going to take a whole lot of collaboration and putting others before ourselves. But are humans cut out for this level of cooperation? Or are we fundamentally too self-interested to work together for the common good?Listener Divyesh is not very hopeful about all this, so he’s asked CrowdScience if humans have a “selfish gene” that dooms us to failure when trying to meet these challenges. He's worried that humans are destined by our evolution to consume ever more natural resources and destroy the environment in the process.But while it's true that humans often act in our own interest, we also show high levels of cooperation and care. Could tapping into these beneficial behaviours help us solve our global problems? Marnie Chesterton goes on the hunt for the best ways to harness human nature for the good of planet Earth - from making sure the green choice is always the cheaper and easier option, to encouraging and nurturing our better, altruistic and collaborative sides.We visit a rural mountain community in Spain to see the centuries-old system they have for sharing common resources; while in the city, we meet activists figuring out how to live a more community-spirited and sustainable urban life. And we speak to experts in evolution, ecology and psychology to find out what helps nudge us into greener habits.Presenter: Marnie Chesterton. Produced by Cathy Edwards for BBC World Service.Image Credit: Getty Images

How is a small budget pocket radio able to recreate all the atmosphere and sounds of a football match? CrowdScience listener Andy wants to know about the science enabling his radio listening, so presenter CrowdScience Geoff Marsh sets off - microphone in hand - to follow the journey of sound on the radio. Starting with the microphone, Geoff learns how acoustic energy is converted into electrical signals. Then BBC World Service presenter Gareth takes Geoff to a little-known room in the BBC called the Radio Shack. Gareth demonstrates how these electrical signals are attached to radio waves before being sent over the airwaves and they take a radio kit apart to understand how these waves are received and converted back into sound waves. Geoff talks to a speech and hearing specialist who, through the use of auditory illusions, shows Geoff that our brains are often filling in the gaps of lower quality audio.Finally, Geoff visits an acoustic lab at Salford University where he hears a demonstration of ‘object based audio’. This technology could enable us to create our own bespoke mix of dramas and sports, such as heightening the commentary sound or choosing to hear just the crowd, just by using the everyday speakers many have lying around them, such as mobile phones.Tune in and join us! Presented by Geoff Marsh Produced by Melanie Brown[Image Credit: Getty Images]

Scientists have been searching for dark matter for decades, and think there’s six times more of it in the universe than the stuff we can actually see, like stars and planets. But they still don’t know what it is. So how can we be sure dark matter really exists? And why does it matter, anyway? Back in 2018, armed with a boiler suit, hard hat and ear defenders, Marnie Chesterton travelled over a kilometre underground into a hot and sweaty mine to see how scientists are valiantly trying to catch some elusive particles – in the hope of settling things once and for all. Several years on we return to the problem, tackling a few more CrowdScience listeners’ questions about dark matter, and hearing whether we’re any closer to uncovering its mysteries. We’re joined in our quest by Dr Chanda Prescod-Weinstein, physicist and author of The Disordered Cosmos: A Journey into Dark Matter, Spacetime, and Dreams Deferred. With Professor Malcolm Fairbairn, Dr Chanda Prescod-Weinstein, Dr Chamkaur Ghag and Professor Katherine Freese. Presented by Marnie Chesterton Produced by Graihagh Jackson and Cathy Edwards

We live in a world where bigger is often seen as better - and the size of someone's brain is no exception. But a listener in Nairobi wants to know, does size really matter when it comes to grey matter? CrowdScience presenter Marnie Chesterton is on a mission to find out if the physical attributes of our head and brain can tell us anything about what's going on inside. We certainly thought so in the past. In the 1800s, phrenology – determining someone’s characteristics by their skull shape – was very fashionable and curator Malcolm MacCallum gives us a tour of the extensive phrenological collection of death masks and skulls in Edinburgh’s anatomy museum. It's a 'science' that's now been completely debunked. Yet there’s no escaping the fact that over our evolutionary history, human brain size has increased dramatically alongside our cognitive capabilities. But is it the whole story? Rick Potts, Director of the Human Origins Program at the Smithsonian tells of the point in time when human brains expanded the most; a time when the climate was changing, resources were unreliable and the intelligence to be adaptable might mean the difference between life and death. Adaptability is also key to Professor Wendy Johnson’s definition of intelligence, although she points out that IQ test, flawed as they are, are still the best predictor we have for intelligence… and that, yes, there is a weak correlation between having a larger head, and doing better at IQ tests. Why is that? We don’t know, says Dr Stuart Ritchie from KCL. According to him, neuroscientists are only in the foothills of understanding how a physical difference in the brain might underpin a person’s psychology. But researching this could offer valuable insights into how our amazing brains work. [Image: Brain being measured. Credit: Getty Images]

“I’m bored!” We can all relate to the uncomfortable - and at times unbearable - feeling of boredom. But what is it? Why does it happen? And could this frustrating, thumb-twiddling experience actually serve some evolutionary purpose? CrowdScience listener Brian started wondering this over a particularly uninspiring bowl of washing up, and it’s ended with Marnie Chesterton going on a blessedly un-boring tour through the science and psychology of tedium. She finds out why some people are more affected than others, why boredom is the key to discovery and innovation, and how we can all start improving our lives by embracing those mind-numbing moments.Featuring: Prof James Danckert (University of Waterloo, Canada), Dr Elizabeth Weybright (Washington State University), Dr Christian Chan (Hong Kong University) and Annie Runkel (University of Dundee). Presented by Marnie Chesterton Produced by Samara Linton Image: Young Asian girl feeling lonely and bored at home. Screen addiction withdrawal symptoms (Credit: Oscar Wong, Getty Images)

Should you wash your eggs? Well believe it or not, there is quite an international debate about this question from CrowdScience listener Susan. In Canada, where Susan grew up, commercially sold eggs are washed before they reach stores, whereas in the UK where she is now living they are not. So what is best to avoid contamination?It’s one of a number of egg-themed questions that CrowdScience tries to crack in this episode. One of our presenters, Marnie Chesterton, heads over to Susan’s home in London to cook some eggs and explore other egg cooking questions from our listeners, such as what is the science behind frying an egg without it sticking to the pan and why are some boiled eggs harder to shell than others?Meanwhile this episode’s other presenter, Anand Jagatia, explores questions about eggs after they have hatched. He investigates a case of curious chicken behaviour sent in by listener Laurie, as well as working out how a cuckoo knows it’s a cuckoo when it’s been raised in another bird’s nest.Presented by Marnie Chesterton and Anand Jagatia Produced by Jonathan Blackwell for BBC World ServiceFeaturing: Dr. Vincent Guyonnet, Dr. Valérie Lechevalier, Dr. Siobhan Abeyesinghe and Dr. Ros Gloag(Photo credit: Getty Images)

Raindrops on roses and whiskers on kittens – CrowdScience has covered a lot this year. And what better way to see out 2021 than to look back at a few of our (and your!) favourite things? Great questions are right at the top of the team’s list – especially with the way that for every one we answer, five more appear in our inbox! So for a festive treat, Marnie asks the crew to answer three of them. What's the sun's role in our sense of direction? Why are we so uncomfortable with other people’s sadness? And why does listening to the radio make us sleepy? (Or is it just too much eggnog…?) From our favourite listener advice on how to keep your Christmas lights untangled to why cold swimming could activate your Vagus nerve, tune in for new questions and more CrowdScience favourites to light up your holiday season!Presented by Marnie Chesterton and many members the CrowdScience Team – Melanie Brown, Marijke Peters, Caroline Steel, Hannah Fisher, Samara Linton and Anand Jagatia. Produced by Sam Baker for BBC World Service.Featuring:• Haneul Jang, post-doctoral researcher, the Max Planck Institute for Evolutionary Anthropology • Juliet Rosenfeld, psychotherapist and author of The State of Disbelief: A Story of Death, Love and Forgetting • Mathias Basner, professor of psychiatry, University of Pennsylvania

As many of us gear up for the annual Christmas feast, some of you may be wondering how to eat everything before it goes off. It’s a great question, as the UN puts global food waste at a whopping 1.3 billion tonnes a year – that’s one third of all edible produce being thrown in the bin. So this week the team investigates listener Peter’s query about what makes some fruit and vegetables rot faster than others. Preserving food used to be about ensuring nomadic populations could keep moving without going hungry, but these days some things seem to have an almost indefinite shelf-life. Is it about better packaging or can clever chemistry help products stay better for longer? A Master Food Preserver explains how heat and cold help keep microbes at bay, and how fermentation encourages the growth of healthy bacteria which crowd out the ones that make us ill. Presenter Datshiane Navanayagam learns how to make a sauerkraut that could keep for weeks, and investigates the gases that food giants use to keep fruit and veg field-fresh. But as the industry searches for new techniques to stretch shelf-life even further could preservatives in food be affecting our microbiome? Research shows sulphites may be killing off ‘friendly’ gut bacteria linked to preventing conditions including cancer and Crohn’s disease.Produced by Marijke Peters for BBC World Service.Featuring:Christina Ward, Master Food Preserver Dr Heidy den Besten, Food Microbiologist, Wageningen University Ian Shuttlewood, Tilbury Cold Store Professor Sally Irwin, University of Hawaii

Life is full of choices, from the mundane (like what to wear today) to the critical (how should we deal with the pandemic?). So how can we make the best decisions? That’s what listener David wants to know.To investigate, Caroline Steel learns how being smarter doesn’t necessarily make you a good decision maker. She speaks to researchers about the importance of ‘gut feelings’ – and how certain people with no intuition whatsoever can struggle to make choices. She also learns why it’s easier to give advice to other people than to follow it yourself, and how we can work together to make the best decisions in a group.Presenter: Caroline Steel Producer: Anand JagatiaContributors: Wändy Bruin de Bruin - Professor of Public Policy, Psychology and Behavioural Science, University of Southern California, USA David Robson, science journalist and author Valerie van Mulukom, Assistant Professor, Coventry University, UK Liz Steel Igor Grossmann, Associate Professor of psychology, University of Waterloo, Canada Anita Williams Woolley associate professor of organisational behaviour and theory, Carnegie Mellon University, USA

What makes things sticky? Listener Mitch from the USA began wondering while he was taking down some very sticky wallpaper. Our world would quite literally fall apart without adhesives. They are almost everywhere – in our buildings, in our cars and in our smartphones. But how do they hold things together? To find out, presenter Marnie Chesterton visits a luthier, Anette Fajardo, who uses animal glues every day in her job making violins. These glues have been used since the ancient Egyptians –but adhesives are much older than that. Marnie speaks to archaeologist Dr Geeske Langejans from Delft University of Technology about prehistoric glues made from birch bark, dated to 200,000 years ago. She goes to see a chemist, Prof Steven Abbott, who helps her understand why anything actually sticks to anything else. And she speaks to physicist Dr Ivan Vera-Marun at the University of Manchester, about the nanotechnologists using adhesion at tiny scales to make materials of the future. Presented by Marnie Chesterton. Produced by Anand Jagatia for BBC World ServiceThis episode was originally broadcast on 2nd October 2020