CrowdScience listener Marie, in Sweden, has always had difficulty with her sense of time. She often thinks that events that happened years ago took place recently or that a holiday coming up is happening sooner than it is. So she wants to know if time is a sense, like the sense of taste or touch, and if it’s something she can learn. Anand Jagatia talks to scientists who’ve studied time, memory and how our brains process and store the events in our lives to find an answer to Marie’s question. Along the way he discovers why time speeds up as we get older, how our bodies register time passing and how our brains put everything that happens to us in order. Featuring: Dr Marc Wittmann, Institute for Frontier Areas in Psychology and Mental Health in Freiburg, Germany Dr Maï-Carmen Requena-Komuro, former PhD researcher, Dementia Research Centre, University College London Professor György Buzsáki, Neuroscience Institute, New York University Professor Adrian Bejan, Thomas Lord Department of Mechanical Engineering and Materials Science, Duke University Presenter: Anand Jagatia Producer: Jo Glanville Sound Design: Julian Wharton Production Co-ordinator: Jonathan Harris Image credit: Peter Cade/ Stone/ Getty Images

What are the actual chances of finding alien life? The idea of meeting an extra-terrestrial has ignited imaginations for hundreds of years, and it’s also inspired real science: the Search for Extra-Terrestrial Intelligence - or Seti - is an organisation that brings together researchers across the world in pursuit of distant life forms. This same dream is on the mind of listener Andrew in Yorkshire in the UK, who has been looking into the sheer size of the universe, and wants to know: how many stars are there in existence, how many planets, and how many planets that could harbour life? CrowdScience presenter Marnie Chesterton sets off on a space odyssey to answer these questions. She starts at Jodrell Bank Observatory in Cheshire, where University of Manchester astrophysicist Eamonn Kerins tells her the number of stars in the universe, and explains the Drake Equation - the mathematical formula that underpins SETI’s work. It’s a series of seven numbers that combine to give you the probability of making contact with an alien civilisation. The next step after stars is the number of planets; Michelle Kunimoto of MIT, who works on Nasa’s TESS mission, explains the transit technique for finding distant worlds. Supposedly anyone can learn to use this technique, so Michelle puts Marnie to a test of her planet-hunting prowess. Distant planets are a huge leap forward - but not all of them will be hospitable to life. Eamonn breaks down how scientists define a habitable planet, as well as how to determine habitability using telescope observations. Marnie speaks to Mary Angelie Alagao from the National Astronomical Research Institute of Thailand about a cutting-edge piece of optical kit designed to block out the light from stars so you can take direct images of the planets next to them. Finally, it’s time to put everything together and get some actual numbers for listener Andrew - as well ask how long it could take to find proof of alien life. (Photo credit: Mark Garlick/Science Photo Library/Getty Images)

Compared to the entirety of human existence, our history of flying in aeroplanes is very short indeed. So what does this fast form of travel do to bodies that have evolved for land-based living? That's what listener Sofia wants to know after working as a flight attendant for over a decade. What effect does working at 35,000 feet have on one's health? How disruptive to your circadian rhythms is hopping across ten time zones in less than 24 hours? What's happening in our stomachs if a crisp packet blows up to the point of popping as the cabin pressure changes? And why do we feel so darn dehydrated when we get off a plane? Host Caroline Steel not only talks to the experts about everything from swollen ankles to what we should eat and drink on planes, she also records her own journey from London to Australia. She does just about everything wrong along the way, but the experts sort her out with some top tips for her next long-haul flight on how to avoid blood clots and even, how to avoid jet lag all together! While in Australia, Caroline also visits a sleep lab where researchers can simulate jet lag to learn how to improve flight safety and the wellbeing of flight attendants and pilots. Join Caroline on her journey as CrowdScience takes to the skies to find out what frequent flyers need to know when it comes cosmic ionising radiation and what we can all do to make that next flight a little more pleasant. Produced by Sam Baker for the BBC World Service. Featuring: Tony Schiemer, Senior Aviation Medical Officer, Royal Australian Air Force Eileen McNeely, Executive Director, SHINE at Harvard T. H. Chan School of Public Health Tracey Sletten, Senior Lecturer, Turner Inst for Brain & Mental Health, Monash University (Photo: Getty Creative # 1432221653)

How do we hear a sound and immediately know where it’s coming from? That’s the question that CrowdScience listener Chiletso asked himself one day as he heard his son bounce a ball and instantly knew its direction. In this ear-opening episode, presenter Anand Jagatia sets out to discover what makes left, right, up and down, sound so different. First, Anand gets blindfolded, so that Alan Archer-Boyd, former auditory scientist and lead engineer at BBC R&D, can put his sound localisation skills to the test. It turns out that having two ears and pinnae, those flappy bits of cartilage on the side of your head, help a lot. Professor Eric Knudsen shares how the barn owl’s asymmetrical ears allow it to hunt mice, even in complete darkness. And Anand uncovers how far he can push his own spatial hearing. Blind activist and researcher Thomas Tajo teaches him how to echolocate like a bat, and Dr Lore Thaler explains what is going on in the brain of experienced echolocators. If you can, listen on headphones! Presented by Anand Jagatia Produced by Florian Bohr for the BBC World Service Image: Boy with hands at his ears Credit: Silke Woweries/Getty Images

Sweating, nausea, chest pain and shortness of breath sound like the physical symptoms of a heart attack. For about 4% of the world’s population, they are also symptoms of an underdiagnosed condition that can leave sufferers curled in a ball and screaming on the floor. A CrowdScience listener wants to know why humans have panic attacks. Host Marnie Chesterton brings on board an expert co-presenter, novelist Tim Clare, to talk us through the hows and whys. Tim suffered from crippling panic attacks for over a decade. He decided enough was enough and has combed through the scientific literature, using himself as a guinea pig, to see what helped. Anxiety can be a useful sensation, helping you to detect and avoid dangers before they happen. But when that morphs into debilitatingly unpleasant symptoms, or an internal monologue saying “that’ll go badly, best to not leave the house,” something has gone wrong. Together, Tim and Marnie explore what’s going on in the brains of those whose threat circuit is faulty. Dr Oliva Remes, a mental health researcher at the University of Cambridge explains how common panic attacks are, and how they often present. Dr Bonnie Furzer at the University of Western Australia explains how exercise can help. Tim takes a dip to demonstrate how cold water, and the cold shock response can help. Dr Rebecca Taugher at the University of Iowa explains how scientists induce a panic attack in the lab, how she has been a guinea pig and why patient SM, without an amygdala, the brain’s so-called ‘fear-centre,’ could still be given a panic attack in the lab, just by inhaling extra amounts of carbon dioxide. Professor Alexander Shackman from the University of Maryland points out that the science will come so much further when researchers look at a genuine cross-section of the population, rather than focussing on those in educational establishments (easier to study) who often don’t experience panic attacks. PHOTO CREDIT: Woman hyperventilating into paperbag Credit: Peter Dazeley/Getty Images

When imagining a robot, a hard-edged, boxy, humanoid figure may spring to mind. But that is about to change. CrowdScience presenter Alex Lathbridge is on a mission to meet the robots that bend the rules of conventionality. Inspired by how creatures like us have evolved to move, some roboticists are looking to nature to design the next generation of machines. And that means making them softer. But just how soft can a robot really be? Join Alex as he goes on a wild adventure to answer this question from listener Sarah. He begins his quest at the ‘Hello, Robot’ Exhibition at the Vitra Design Museum in Weil am Rhein, Germany to define what a robot actually is. Amelie Klein, the exhibition curator, states anything can be a robot as long as three specific criteria are met (including a cute cuddly baby seal). With this in mind, Alex meets Professor Andrew Conn from the Bristol Robotics Lab who demonstrates how soft materials like rubber are perfect contenders for machine design as they are tough to break and - importantly for our listener’s question - bendy. Alex is then thrown into a world of robots that completely change his idea of what machines are. He is shown how conventionally ‘hard’ machines are being modified with touches of softness to totally upgrade what they can do, including flexible ‘muscles’ for robot skeletons and silicon-joined human-like hands at the Soft Robotics Lab run by Professor Robert Katzschmann at ETH Zurich. He is then introduced to robots that are completely soft. Based on natural structures like elephant trunks and slithering snakes, these designs give robots completely new functions, such as the ability to delicately pick fruit and assist with search and rescue operations after earthquakes. Finally, Alex is presented with the idea that, in the future, a robot could be made of materials that are so soft, no trace of machine would remain after its use... Presenter: Alex Lathbridge Producer: Julia Ravey (Image: RoBoa in action on a rooftop in Zurich. Credit: Julia Ravey)

CrowdScience listener Eric, in New Zealand, has noticed his wisteria growing towards a neighbouring tree. He thinks that it actually knows where it’s going. But how can a plant have a sense of direction? Plants don’t have the advantage of brains or eyes, but that doesn’t seem to stop them from being clever enough to find out from their environment where to move and how to get there – all while being rooted to the spot. Marnie Chesterton visits the Natural History Museum and Kew Gardens in London, home to the largest collection of living plants in the world, to discover how plants make their manoeuvres, and talks to botanists and plant biologists for the latest findings on the mysterious life of climbing plants. Featuring: Dr Mariane Sousa-Baena, School of Integrative Plant Sciences, Cornell University Dr Ilia Leitch, Senior Research Leader, Kew Gardens Tom Freeth, Head of Plant Records, Kew Gardens Dr Silvia Guerra, Neuroscience of Movement Laboratory, Padua University Professor Christian Fankhauser, Centre for Integrative Genomics, Lausanne University Dr Sandra Knapp, Merit Researcher, Natural History Museum

If, like this week’s Crowdscience listener Lili, you’re an avid gymgoer, you may well have wondered where your fat disappears to when you exercise? Well, the short answer is that we convert it to energy that powers a whole range of physical processes, from breathing to walking as well as lying down and doing nothing. But the science behind energy expenditure is a little more complicated than that. Presenter Anand Jagatia pops on an exercise bike to have his metabolism measured, and learns that he may be relying on an entirely different source of fuel as he works up a sweat. But is all that hard work worth the effort it involves? Recent research suggests there's a limit to the number of calories us humans can burn, and that doing physical activity isn’t a sure-fire way to keep trim. Even hunter-gatherers who walk 13,000 steps a day have the same metabolic rate as the average American. So if working out isn't the best way to lose weight, how about harnessing our own fat to tackle the complications of obesity? It used to be thought brown fat was exclusive to babies (and bears) but we now know adults have some of it too, and it seems to play a vital role in combatting a range of chronic diseases including hypertension and diabetes. Presenter: Anand Jagatia Producer: Marijke Peters

Yoga benefits our health in many ways, say the yogis, but which claims are backed up by science? Can yoga actually alleviate depression, fix lower-back pain or even reduce cardiovascular disease? Presenter Marnie Chesterton gets into her Lotus (position) and finds out first-hand at a class. Whilst in warrior one, she discusses the potential physical and mental health benefits of this ancient art of stretching, balance and movement with her class teacher. Returning from mat to studio, Marnie puts some of those claims to experts around the globe. She investigates the evidence to find out whether health boosting properties are the key to yoga's enduring popularity. Pannalists: Rajvi Mehta Prof. Holger Cramer Dr Richard Davidson Presented by Marnie Chesterton Produced by Richard Walker

Why does the thought of giving a talk to an audience fill so many of us with sheer terror? Marnie Chesterton investigates for listener Nhial, who has seen his fellow students in Morocco become panic stricken at the prospect and wants to know the reason for our anxiety. According to one study, 77 per cent of us share that fear. Marnie finds out about the relationship between stress, our brains and our voices from research associate Dr Maria Dietrich at the University Hospital, Bonn University. She talks to Nhial’s tutor, Professor Taoufik Jaafari, at Hassan II University of Casablanca about the challenges facing his students. And she visits the National Theatre in London to get some expert training from Jeannette Nelson, head of voice, who works with some of the world’s leading actors. Could there be an evolutionary explanation for the purpose of public speaking? Is it something we actually need to be good at? Marnie asks evolutionary psychologist Professor Robin Dunbar at Oxford University and gets some surprising answers. She meets psychologist Dr Preethi Premkumar at London South Bank University, who has developed virtual reality therapy with colleagues at Nottingham Trent University, and tries out the treatment herself. Presenter: Marnie Chesterton Producer: Jo Glanville

We generate a huge amount of noise, whether it’s our rumbling roads, pumping parties, or talkative tourists. And the topic of noise also generates a lot of questions from our listeners. In this episode we explore three of them, with the help of acoustic scientist Kurt Fristrup and neuropsychologist Catherine Loveday. Listener Dominique finds it hard to experience even one minute of a natural soundscape without some intrusion of human-made noise. He wonders how noise pollution is affecting both the natural world and us humans. We discuss just how noisy our modern world is, and visit a National Park in California to hear how they’re encouraging more peace and quiet there. Meanwhile Michelle, having witnessed her husband wince in pain at the sound of squeaking takeaway boxes, asks why certain noises are particularly unpleasant or even painful to some people. And finally, Jennifer has a sonic mystery for us to solve: why does the time of day make such a difference to the distant noises reaching her remote home? With contributions from Professor Catherine Loveday, Dr Kurt Fristrup and Mia Monroe. Additional audio courtesy of the U.S. National Park Service/Patrick Myers, Dominique Laloux, Boise State University/Jesse Barber, and KCSU/Asher Korn Presenter: Anand Jagatia Producer: Cathy Edwards Studio Managers: Bob Nettles and Jackie Margerum

From Lawrence of Arabia to Star Wars via tales of intrepid adventurers traversing lonely sand-swept landscapes, deserts have always had a powerful pull on the popular imagination. But if a desert is full of sand, where did all that sand come from in the first place? That is what CrowdScience listener Andy wants to know, so presenter Caroline Steel heads off into the dunes to find out. She begins by finding out what a desert is anyway and whether it is always sandy, as well as tracing the flow of material across the huge, ever-shifting sand seas of the Sahara. From deserts fed by sand from mountains thousands of kilometres away, to dunes migrating across the entire continent of Africa, Caroline discovers how sand has just the right properties to be carried along by the wind. She also explores how the sand in every desert has a unique fingerprint, and finds out how fish bones in the Sahara tell the story of its lush, green past. Contributors: Dr Jo Nield, University of Southampton Dr Andreas Baas, Kings College London Dr Andrea Zerboni, University of Milan Presented by Caroline Steel Produced by Ben Motley for the BBC World Service (Photo: The Sahara desert near Timbuktu, Mali Credit: Jeff Overs)

When falling in love or fancying someone, one emotion can dominate over the rest: jealousy. Some may try to play it cool and act aloof, but seeing - or even thinking - of a romantic partner engaging with others can lead people to act completely out of character. The green-eyed monster can hijack thoughts for days to weeks on end, spending precious energy ruminating on situations that may never arise. So why is it that humans feel jealousy? Do people experience this emotion differently? And are there ways to stop it? CrowdScience presenter Caroline Steel sets about answering these questions from listener Odile in France, who has struggled with all-consuming jealousy in some romantic relationships. She hears about a kind of monkey who get jealous of their own reflection from Professor Karen Bales at University California Davis. A trip to ZSL London Zoo sees more monkeys, but these are more bothered about protecting the vital friendships which aid their survival. Dr Alex Mielke from the University of St Andrews explains how these interactions can give us an insight into why jealousy exists. Some of us get more jealous than others and are more likely to act out of character when the green-eyed monster takes hold. Caroline completes a detailed questionnaire to see how jealous she really is, and gets advice from Julia in South Africa, who is in a polygamous marriage and has had to handle romantic jealousy. The nature-nurture balance of jealousy is untangled by geneticist Dr Laura Wesseldijk from Amsterdam UMC (who reveals some surprising information about the first author on her research paper…) and psychologist Dr Johan Ahlen from the Karolinska Institute rounds off the programme discussing how the future of jealousy management could look like for those who struggle. Presenter: Caroline Steel Producer: Julia Ravey

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]

ow 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 [Image: Family riding bikes. Credit: Getty Images]

Over the past 12 months, CrowdScience has travelled the world, from arctic glacierscapes to equatorial deserts, to answer listeners’ science queries. Sometimes, the team come across tales that don’t quite fit with the quest in hand, but still draw a laugh, or a gasp. In this show, Marnie Chesterton revisits those stories, with members of the CrowdScience crew. Alex the Parrot was a smart bird, with an impressive vocabulary and the ability to count and do basic maths. He was also intimidating and mean to a younger parrot, Griffin, who didn’t have the same grasp of the English language. Scientist Irene Pepperberg shares the consequence of this work-place bullying.  Take a tour of the disaster room at ICPAC, the IGAD Climate Prediction and Applications Centre (ICPAC) based in Nairobi, Kenya. It’s a new building where scientists keep watch for weird new weather and passes that information to 11 East African countries. Viola Otieno is an Earth Observation (EO) Expert and she explained how they track everything from cyclones to clouds of desert locust. Malcolm MacCallum is curator of the Anatomical Museum at Edinburgh University in Scotland, which holds a collection of death masks and skull casts used by the Edinburgh Phrenological Society. Phrenology was a pseudoscience, popular in the 1820s, where individuals attempted to elucidate peoples’ proclivities and personalities by the shape of their heads. We see what the phrenologists had to say about Sir Isaac Newton and the “worst pirate” John Tardy. While recording on Greenland’s icesheet, the CrowdScience team were told by Professor Jason Box about “party ice.” 40,000 year old glacial ice is a superior garnish for your cocktail than normal freezer ice, apparently. This starts a quest for the perfect Arctic cocktail. Presented by Marnie Chesterton  Produced by Marnie Chesterton, featuring producers Florian Bohr, Sam Baker and Ben Motley  (Photo:)

Does your mum’s singing make you cringe with embarrassment? Do your dad’s jokes make you want to scream - and not with laughter? Or maybe you are the parent driving your offspring round the bend with rules and curfews? If so, you are not alone. CrowdScience listener Ilixo, age 11, has been wondering why it is that our parents become so annoying as we become teenagers. Is it something that is changing in his brain or are they actually becoming more annoying as they age? Presenter Marnie Chesterton consults our assembled panel of experts to discuss conflict between parents and their offspring. Developmental psychologist Liane Alampay, from the Ateneo de Manila University, Philippines, describes how the teenage experience varies around the world. Child and educational psychologist Laverne Antrobus in London says the teenage quest for independence is a normal - and necessary - developmental stage for becoming an adult. And Jennifer Lansford, a Research Professor at Duke University who studies parenting and child development, offers insights into the role peers play. Do not despair! - the panel offers tips for how to keep the peace - whether you’re an argumentative adolescent or a provoking parent. Producer: Lorna Stewart (Photo: Teenager putting fingers in ear while parent tries to talk to them. Credit: Getty Images)

CrowdScience listener David was playing snooker in Thailand when he started thinking how such a smooth ball was dependent on the rough green baize of the table to bring it to a stop. Would it be possible to play snooker at all in a completely frictionless universe? Sometimes friction produces heat. Could we ever control it completely? We try to reduce friction in some cases by using lubricants, whilst at other times like braking at a traffic junction we depend upon friction entirely. Anand Jagatia heads to Edinburgh in Scotland, UK, to meet some true masters of this mysterious entity: players of the winter sport Curling. What exactly is friction, and does thinking about it tell us something deeper about the universe? Taking part: Jennifer Dodds, Team GB Olympic Gold medallist Dave Lieth, Head of performance services, British Curling Susan Perkin, Professor of Physical Chemistry, University of Oxford Roger Lewis, Professor of Mechanical Engineering, University of Sheffield Presented by Anand Jagatia Produced by Alex Mansfield With thanks to David for his question. [Image: curling. Credit: Getty Images]

If your home is drafty, filling in holes and cracks can help tackle rising energy bills, and lower your carbon footprint. But is there a limit to how airtight we should make our homes? That’s what CrowdScience listeners Jeff and Angie wondered when weatherproofing their doors and sealing up cracks for the winter. Once every last gap is blocked, will enough air get in for them to breathe properly? How would they know if they’ve gone too far? With Covid-19 making us more aware than ever of the importance of good ventilation, CrowdScience investigates how to make your home cosy and energy-efficient without sacrificing fresh air in the process. And we find out how, in hotter climates, you can carefully tap into your drafts, to reduce energy-intensive air conditioning. With contributions from Kimble Smith, Professor Nicola Carslaw, Dr Iain Walker, Marion Baeli and Dr Yashkumar Shukla. Presented by Marnie Chesterton Produced by Cathy Edwards for the BBC World Service

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 Jagatia Contributors: Dr Anne Templeton, University of Edinburgh Marcel Altenburg, Manchester Metropolitan University Prof John Drury, University of Sussex Archive: 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 Park Presented 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, Greenland Presenter: 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 Service Image: 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 London Presented 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 Service Contributors: 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 Jagatia Contributors: 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 University Sounds: Lions from Karen McComb, emeritus professor at University of Sussex Túngara frogs from Michael Ryan, professor of zoology at University of Texa at Austin Presenter: 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 Brown Interviewees: 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 Institute Presented 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 Arkansas Presented 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 Image credit: 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, Bremen Presented 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 London Presented 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 Jagatia Featuring: 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 Florida Photo: 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 Brown Contributors: 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, NASA Presented 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 Service Image 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

Imagine spending six months of every year living in total shade. That’s what life is like for residents of the Norwegian town of Rjukan, set so low in a valley that they see no direct sunshine at all from October to March. Marnie Chesterton heads there to hear about an ingenious solution: giant mirrors that beam rays down into the town square, where locals gather to feel the reflected heat. The man behind the project was motivated by a need for winter sun – but how much difference does it really make to our health and happiness? That’s the question posed by this week’s Crowdscience listener Michael, who has noticed living in the rainy Australian city of Melbourne is taking its toll. Many pensioners claim sunshine relieves achiness as well as conditions like arthritis but one of the biggest scientific studies found temperature actually has no impact on reported pain levels, while factors like air pressure and humidity may play a role. When it comes to our mood, it seems that spending time outside is more important than feeling the heat and the optimum temperature for wellbeing is around cool 19 degrees centigrade, while excessive warm weather has been linked to an increase in violence and crime. Contributors: Dr Anna Beukenhorst, University of Manchester Professor Oscar Ybarra, University of Illinois Professor Solomon Hsiang, University of California, Berkeley Martin Andersen, artist (Image: Man with smoke coming out of ears. 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 Service Featuring: 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 Jagatia Contributors: 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 Service This episode was originally broadcast on 2nd October 2020

In most cultures, the soundtrack to our lives is one of optimism. We are told to aim for the stars, dream big and believe that tomorrow will definitely be a better day. But why do so many people subscribe to the cult of 'glass half full' when life’s hardships should make any reasonable person a bit more wary? Listener Hannah from Germany - a self-described pessimist - is intrigued as to whether the optimistic way of life is really the best way to be. Taking on the challenge is Marnie Chesterton, who finds out why 80% of the population have an optimism bias and how the ability to hope and take risks may have helped the human species get where it is today. She also meets a man who pushes the optimistic outlook to its very limits - Base jumping world champion, Espen Fadnes. Listener Hannah on the other hand looks into the psychology of pessimism to find out if there are any advantages to her less rose-tinted view on life - and whether the culture we grow up in shapes how realistically we see the world. Producer: Caroline Steel Presentet: Marnie Chesterton Contributors: Espen Fadnes – Freefall professional Tali Sharot – Professor of neuroscience, UCL Julie Norem - Professor of psychology, Wellesley College Jeanne Tsai - Professor of psychology, Stanford (Image: Two arrows, one with a sad smiley and the other with happy smiley, pointing in opposite directions. Credit: Getty Images)

Cats started hanging out with humans thousands of years ago, and nowadays these fluffy, lovable pets are found in many of our homes. But there is no doubt lots of them still have keen hunting instincts - witness all the birds and small mammals they kill each year. CrowdScience listener Rachel started wondering whether her cat Eva could fend for herself while watching her uncoordinated swipes at a toy on a string, and seeing her fall off the sofa. Even though Eva was once a stray, she now lives entirely indoors, and it is hard to imagine her holding her own back on the mean streets. But could this pampered pet recover her survival instincts? Or would she go hungry, or fall foul of other cats or predators? Cat behaviour expert Roger Tabor is on hand with answers. His pioneering ‘cat-navs’ shine a light on what cats get up to inside and outside the home; we meet one of his subjects, a tiny cat with a fierce personality. Roger explains how a cat’s survival toolkit depends on their sex, breed, and above all their early life. Environment matters, too, so in Japan, where Rachel and her pet cat live, we visit a cat shelter to learn about the day-to-day challenges stray cats face. And just how ‘domestic’ are our cats, anyway? How different are they from their wildcat cousins, and how did they come to be our companions in the first place? It turns out beguiling humans might be even more of a survival trick than hunting. Presenter: Melanie Brown Producer: Cathy Edwards Contributors: Roger Tabor – Chartered Biologist and Cat Behaviourist Jamie Baker – Head Keeper, Battersea Park Children’s Zoo Dr Eva-Maria Geigl – Research Director, CNRS (French National Centre for Scientific Research) Susan Roberts and Cheryl Nodhturft-Mori – Japan Cat Network (Image: Cat in Lion costume. Credit: Getty Images)

Concrete is the most widely used substance on earth after water. It’s quite literally the foundation of the modern world, and no wonder - it’s strong, cheap, and mouldable into nearly any shape. But these benefits come at a cost: concrete production is responsible for around 8% of global CO2 emissions - that’s around three times more than the aviation industry. Concrete might not look pretty, but given its carbon footprint, should we be more careful about how we use it? And rather than throwing waste into landfill, could we recycle it instead? That’s what Crowdscience listener Catherine wants to know. To investigate, Marnie Chesterton and Anand Jagatia learn more about what makes concrete such a brilliant and versatile material. It’s down to the chemistry of how cement dries – which, it turns out, is anything but boring. They find out how the stuff is made, and why that produces so much carbon. And they hear about some ingenious projects to repurpose demolition waste – including creating underwater habitats for marine life, and using 3D printers to turn crushed concrete into street furniture. With Prof John Provis, Prof Becky Lunn, Chris LaPorta, Sheryl Lee, Dr Edward Randviir and David Lacy Presented by Marnie Chesterton and Anand Jagatia. Produced by Anand Jagatia for BBC World Service [Image: Discarded Concrete, Credit: Getty Images]

The science is unequivocal: human-made climate change is leading the world into an environmental crisis, and time is running out to prevent permanent damage to ecosystems and make the planet uninhabitable for many of us humans. As communities around the world increasingly experience the devastating effects of global warming, world leaders, policy makers and scientists from all over the globe are attending COP26, the United Nation’s major climate summit in Glasgow, Scotland. Each nation will be frantically negotiating its commitments to tackling emissions - many agree it’s a pivotal moment for the future of humanity. Crowdscience hosts a panel of three experts taking part in the conference, to hear their thoughts on what progress has been made so far. They answer listener questions on rising sea levels, explaining that a temperature rise of more than 1.5 degrees won’t just affect small island nations but will have serious consequences for every country in the world. We hear about an interactive atlas developed by the Intergovernmental Panel on Climate Change (IPCC) that shows the impact of higher temperatures in different regions. And presenter Marnie Chesterton asks about the financial barriers that have prevented many people from traveling to COP26 and discovers why it’s vital that people from the global south have their voices heard. Featuring: Ko Barrett, Vice-chair of the Intergovernmental Panel on Climate Change (IPCC) Dr Saleemul Huq, Director of the International Centre for Climate Change and Development in Bangladesh(ICCCAD) Dr Tara Shine, Director of Change By Degrees Produced by Melanie Brown and Marijke Peters for BBC World Service. [Image: Delegates in the Action Zone at COP26 UN Climate Summit, Glasgow. Credit: Getty Images]

As the world slowly moves away from using fossil fuels for electricity, one tiny Scottish island has proved it’s possible to rely almost entirely on renewables. The inner Hebridean isle of Eigg used to get its power from diesel generators. But in 2008 its residents launched the world’s first electricity system powered by nature, and the Crowdscience team wants to know exactly how they did it, and whether such a model could work in other places with no national grid? Marnie discovers that the community is key to the success of this project, meeting the maintenance men who taught themselves to install equipment and solve any problems themselves, and hearing from residents who’ve changed their habits to use less juice. With the mainland more than an hour away by a once-daily ferry, this kind of resourcefulness is vital. Hydroelectric generators harness the power of running water and are complemented by wind turbines and solar panels on peoples roofs, meeting 95% of Eigg’s energy needs. Now others are learning from this unique experiment and we meet the Malawians who were inspired after visiting Eigg. A solar grid in the village of Sitolo has provided power to thousands of people, and the people who designed it are planning others. Thanks to Eigg residents: Sue Hollands, Maggie Fyfe, Eddie Scott, Bob Wallace, Greg Carr Presented by Marnie Chesterton Produced by Marijke Peters for BBC World Service. This episode of CrowdScience has been edited to correct a factual error Image: Wind turbines on Eigg Credit: Getty Images

"To be or not to be” was never your decision. No one alive today is an “exister” by consent - your parents made that call for you. But who can blame them? Animals are hardwired with strong impulses towards their procreative goals, and we humans, by and large, are no different. But for some conscientious people alive today, this most fundamental of biological impulses is butting up against a rational pessimism about the future... With apocalyptic scenes of natural disasters, rising sea levels and global pandemics causing existential dread and actual suffering, it's understandable that CrowdScience listener Philine Hoven from Austria wrote to us asking for help her make sense of what she sees as the most difficult question she faces - should she have children? In this episode, presenter Geoff Marsh helps Philine to predict what kind of a world her hypothetical child might inhabit, and explores the impact their existence, or indeed non-existence might have on society and the planet. Plus, we'll explore what ‘antinatalism’- a philosophical stance which argues against procreation, can tell us about the moral landscape of the unborn. With Ms Caroline Hickman, Professor Mike Berners-Lee, Professor Noriko Tsuya and Professor David Benatar. Presented and produced by Geoff Marsh for BBC World Service

Philosophers have long pondered the concept of a brain in a jar, hooked up to a simulated world. Though this has largely remained a thought experiment, CrowdScience listener JP wants to know if it might become reality in the not-too-distant future, with advances in stem cell research. In the two decades since stem cell research began, scientists have learned how to use these cells to create the myriad of cell types in our bodies, including those in our brains, offering researchers ways to study neurological injuries and neurodegenerative disorders. Some labs have actually started 3D printing stem cells into sections of brain tissue in order to study specific interactions in the brain. Human brain organoids offer another way to study brain development and diseases from autism to the Zika virus. So, might stem cell research one day lead to a fully-grown human brain, or is that resolutely in the realm of science fiction? If something resembling our brains is on the horizon, is there any chance that it could actually become conscious? And how would we even know if it was? Host Marnie Chesterton takes a peek inside the human brain and speaks with leading scientists in the field, including a philosopher and ethicist who talks about the benefits – and potential pitfalls – of growing human brain models. Along the way, we'll pull apart the science from what still remains (at least for now) fiction. Presented by Marnie Chesterton Produced by Sam Baker for BBC World Service

Snails are a major enemy of gardeners around the world, invading vegetable patches and gobbling prize plants. CrowdScience listener Alexandre reckons he’s removed thousands of them from his garden, which got him wondering: apart from eating his garden to the core, what’s their wider role in nature? Would anyone or anything miss them if they suddenly disappeared? And for that matter, what about other creatures? We all know how complex biodiversity is, but it seems that some animals are more important than others in maintaining the balance of life on earth. Is there anything that could go extinct without having knock-on effects? CrowdScience heads to the Hawaiian mountains, a snail diversity hotspot, to discover the deep value of snails to native ecosystems there. Researchers and conservationists are working together to protect these highly endangered snails, and their natural habitats, from multiple threats. We hear why all snails – even the ones munching Alexandre’s petunias – have their role to play in the natural world, and get to grips with cascading extinctions: how the loss of a single species can trigger unpredictable effects on a whole ecosystem. With contributions from Imogen Cavadino, Dr Norine Yeung, Dr Kenneth Hayes, Dr David Sischo, Jan Kealoha, and Professor Ian Donohue. Presented by Marnie Chesterton Produced by Cathy Edwards for the BBC World Service [Image credit: Getty Images]

In the past 18 months we have heard lots about the human immune system, as we all learn about how our bodies fight off Covid-19 and how the vaccine helps protect us. But this got listener John, in Alberta, Canada, thinking about how trees and plants respond to diseases and threats. Do they have immune systems and if so, how do they work? Do they have memories that mean they can remember diseases or stressful events 5 months, or 5 years down the line, to be better prepared if they encounter the same threats again? Presenter Marnie Chesterton sets out to investigate the inner workings of plants and trees, discovering that plants not only have a sophisticated immune system, but that they can use that immune system to warn their neighbours of an attack. Some researchers are also investigating how we can help plants, especially crops, have better immune systems – whether that’s by vaccination or by editing their genes to make their immune systems more efficient. But some plants, like trees, live for a really long time. How long can they remember any attacks for? Can they pass any of those memories on to their offspring? Crowdscience visits one experimental forest where they are simulating the future CO2 levels of 2050 to understand how trees will react to climate change. Featuring: Professor Jurriaan Ton, University of Sheffield Professor Xinnian Dong, Duke University Dr Estrella Luna-Diez, University of Birmingham Peter Miles, F.A.C.E. Facility Technician, University of Birmingham Presented by Marnie Chesterton and Produced by Hannah Fisher for the BBC World Service. Photo credit: Getty Images

This year has been a weird one for UK gardeners – unpredictable spring temperatures meant flowers failed to bloom and throughout the rainy summer, slugs have been savaging salad crops. But why and when plants blossom is about more than just early cold spells and wet weather, and a listener in California has asked Crowdscience to investigate. Flowering is vital to both plants and us. Without it, they wouldn’t be able to evolve and survive (and we wouldn’t have anything to eat). Anand Jagatia hears that different species have developed different strategies for doing this based on all sorts of things, from where they’re located to how big they are to what kind of insects are around to pollinate them. The famously stinky Titan Arum, or corpse flower, for example, blooms for a single day once every decade or so before collapsing on itself and becoming dormant again. This gives it the best chance of attracting carrion beetles in the steamy Sumatran jungle. But other plants open their petals much more regularly, which is a process regulated by a clever internal clock that can sense daylight and night. It’s even possible to trick some of them into producing flowers out of season. Cold is also a vital step for some brassicas and trees, and scientists are starting to understand the genes involved. But as climate change makes winters in parts of the world warmer and shorter, there are worrying knock on effects for our food supply. Produced by Marijke Peters for BBC World Service. Featuring: Guy Barter, RHS Professor Judy Jernstedt, UC Davis Professor Dame Caroline Dean, John Innes Centre Professor Ove Nilsson, Umea Plant Science Centre (Photo credit: Getty Images)

Look into my eyes. What do you see? Pupil, lens, retina… an intricate set of special tissues and mechanisms all working seamlessly together, so that I can see the world around me. Charles Darwin called the eye an ‘organ of extreme perfection’ and he’s not wrong! But if the eye is so complex and intricate, how did it evolve? One listener, Aloyce from Tanzania, got in touch to pose this difficult question. It’s a question that taxed Darwin himself, but CrowdScience is always up for a challenge! The problem is that eyes weren’t ever designed - they were cobbled together over millions and millions of years, formed gradually by the tweaks and adaptations of evolution. How do you get from the basic detection of light to the wonderful complexity - and diversity – of visual systems we find throughout the animal kingdom? CrowdScience sent Marnie Chesterton on an 800 million year journey to trace how the different elements that make up the human eye gradually came into being; from the emergence of the first light-sensitive proteins to crude eye-cups, from deep sea creatures with simple pinhole eyes to the first light-focusing lenses, all the way to the technicolour detail of the present day. Produced by Ilan Goodman for the BBC World Service. With contributions from: Dr Adam Rutherford, Dr Megan Porter, Professor Dan Nilsson, Dr Samantha Strong (Photo Credit: Getty Images)

Pioneering physicist and inventor Nikolas Tesla dreamt of connecting the world up through wireless communication and power. Despite demonstrating he could transfer power short distances his longer distance experiments were considerably less successful. But CrowdScience listener, George from Ghana, wants to know if now - more than one hundred years after Tesla’s demonstrations - his dream of wireless power is closer to becoming a reality. In countries where rugged landscapes make laying traditional power lines difficult and costly, could wireless electricity help connect those communities who are without mains power? CrowdScience presenter Melanie Brown beams to reporters around the world who visit scientists now using state of the art technology to reimagine Tesla’s dream. Alex Lathbridge is in Ghana and after meeting listener George he gently doorsteps a local electrical engineering lecturer to find out how electricity can ‘jump’ between two coils. Reporter Stacy Knott visits start-up company EMROD in New Zealand who are developing ‘beamable’ electricity. She hears an electric guitar being powered from 36 metres away with no wires and finds out how they are using lasers to make sure they don’t harm any wildlife that might wander into the beam. We then hear how wireless electricity could help fulfil the power demands of a growing electric vehicle market. Reporter John Ryan visits the town of Wenatchee where it has been electrifying its’ bus fleet and putting wireless chargers into the tarmac at bus-stops so that the busses can trickle charge as passengers get on and off. Finally, we ask whether one day, the tangled knot of wires spilling out of our electronic devices will be but a thing of the past. Presented and Produced by Melanie Brown with additional reporting from; Alex Lathbridge, John Ryan and Stacey Knott With contributions from; Prof. Bernard Carlson, Dr Samuel Afoakwa, Ray Simkin, Greg Kushnier, Andy Daga and Richard DeRock (Photo credit: Getty Images)

Our connection to the night sky spans cultures and millennia: observing the stars and planets helped our ancestors navigate the world, tell stories about the constellations, and understand our place in the universe. But these days, for the vast majority of us, seeing the stars is getting harder. 80% of people live under light polluted skies, and in many cities you’re lucky to see a handful of stars at night. This state of affairs is bothering CrowdScience listener and keen stargazer Mo from Salt Lake City in the USA, who wonders if there’s anything we can do about light pollution. Of course, we could simply turn out all the lights, but that’s unrealistic. So what are smarter ways of lighting our communities to preserve our view of the cosmos? Increasingly worried by the effect of artificial lighting on the ability to observe stars, astronomer Dr Jason Pun set up a series of monitoring stations to continuously measure ‘sky glow’. By comparing sky glow across the world, he wants to figure out which approaches work best. One community taking an active approach is the South Downs National Park in South East England, one of a number of Dark Sky Reserves around the word. We visit the park and speak to the Dark Skies Officer there, to find out how people are coming together to turn down their lights and keep the night dark. And it’s not just stargazing that’s threatened by light pollution. Artificial light at night disrupts the circadian rhythms of wildlife. We visit a project in rural Germany looking into the benefits of dark-sky-friendly lighting on insect populations there. With contributions from Dr Jason Pun, Paulina Villalobos, Dan Oakley, Doug Jones, Dr Sibylle Schroer and Sophia Dehn. Presented by Anand Jagatia with additional reporting by Felix Franz Produced by Cathy Edwards [Image credit: Getty Images]

How we sleep is a topic of endless fascination and for some can, ironically be quite exhausting. Modern life has allowed us to invade the night, and those pesky late night work emails, social media and TV all conspire to limit our sleep or simply prevent us from a truly restful night. But if we travel back in time, did our ancestors master sleep any better? No air-con or electric fan for them on hot humid nights, and only smoky fires to keep them warm on cold, snowy nights. What if we go way back into our pre-history, to our ancient human ancestors? No interruption for them from an unwanted work email, however perhaps a ravenous lion gave them more reason for those night time worries. CrowdScience listener Tom asks our sleep deprived presenter Datshiane Navanayagam to investigate how our sleep has changed over history and pre-history. She talks to Professor Russell Foster, Head of the Sleep and Circadian Neuroscience Institute at the University of Oxford and Neanderthal expert Dr Rebecca Wragg Sykes about slumber habits in days of yore, and in doing so, she uncovers some top tips from our ancestors that may give us all a better nights rest. Presented by Datshiane Navanayagam and Produced by Alexandra Feachem (Woman sitting in bed and yawning. Credit: JGI/Jamie Grill/Getty Images)

If you’ve ever fallen over and grazed your skin, maybe you wished it were made of stronger stuff. The tough hide of a rhinoceros or the protective armour of a stag beetle would do a better job. It’s a thought that’s been bothering CrowdScience listener Paul, who points out that our skin also suffers from acne, eczema and hives; it dries out; it bruises. In fact, human hide is so vulnerable that we cover our feet in other animals’ skin and our bodies in clothes just to make life more comfortable. Is this really the pinnacle of evolution? Marnie Chesterton makes the case for the largest, fastest-growing organ, hiding in plain site on our body. Tissue Engineer Professor Sheila MacNeil from Sheffield University explains how skin manages to be breathable yet waterproof; flexible yet stronger than steel; sensitive to touch but protective against pollution and damaging UV. Skin biologist Dr Christina Philippeos from King’s College London explains how our bodies make a scar. Professor Muzlifah Haniffa has developed an atlas of the human skin – a tool to help researchers unravel the mysteries of how different skin cells interact. This atlas should help treat skin diseases in the future. Over in Tanzania’s Regional Dermatology Training Centre in Moshi, Dr Daudi Mavura talks us through a rare but devastating skin disorder called Xeroderma Pigmentosum, or XP. For children with XP, sunlight is dangerous because a mutation in the skin’s DNA repair mechanism means that UV rays can cause lesions and tumours. Our epidermis is already multifunctional but over at Ben May Department of Cancer Research at the University of Chicago, Professor Xaioyang Wu and colleagues are looking at how much more skin could do. Personalised skin grafts may provide living drug patches to help people manage their disease, addiction or even weight. With thanks to Dr Lynne MacTavish from Mankwe Wildlife Reserve in South Africa for describing a rhino’s skin. Produced and presented by Marnie Chesterton. [Image: Young and Old, dry skin Credit: Eric A. Nelson/Getty Images]

Humans are responsible for emitting over 40 billion tonnes of carbon dioxide into the atmosphere every year – and we all know that we need to reduce that figure to prevent devastating climate change. Listener Saugat wonders whether smart technology and artificial intelligence can help us do this more quickly? Green energy will go a long way to tackling the problem, but integrating wind and solar into our current electricity grid is complicated. CrowdScience hears how AI is being used at a wind farm on the island of Orkney to predict periods of high winds, so that excess energy can be turned into hydrogen and stored, then converted back to electricity when there’s greater demand. Digital mirrors are also playing a major role in optimising performance, and scientists say cloud-based “twins” of physical assets like turbines can improve yield by up to 20%, allowing engineers to identify problems via computer without ever having to be on site. Marnie visits an intelligent building in London’s financial district where sensors control everything from air-conditioning to lighting, and machine learning means the building knows which staff will be on which floor at any given time, switching off lifts that are not in use and adjusting ventilation to save on power. Its designer says incorporating this kind of digital technology will help companies achieve net zero more quickly. And in India, more than half the population are involved in agriculture, but the sector is plagued by inefficiency and waste. Tech start-ups have realised there’s potential for growth, and are using drones to monitor crop production and spraying, giving farmers apps which help them decide when and where to fertilise their fields. Produced by Marijke Peters for BBC World Service. Featuring: Professor Srinivasan Keshav, University of Cambridge Matthew Marson, Arcadis Group [Image Credit: Getty Images]

Today, up to 3 billion people around the world play video games, from candy based mobile puzzles to virtual battlegrounds filled with weapons. Many people have turned to gaming during the pandemic as a way of staying connected – but what does science really say about the impact of gaming? Does playing violent video games lead to violence in the real world? Do brain training apps really work? How much gaming is too much – can videogames really be addictive? And how can videogames help us to explore difficult issues like death, grief and loss? Alex Lathbridge and Anand Jagatia look at the evidence and play some games along the way, speaking to psychologists, doctors and game designers about the power of video games to change us - for better or worse. With Adrian Hon, Professor Andrew Przybylski, Professor Pete Etchells, Professor Henrietta Bowden-Jones and Dr Sabine Harrer

Reduce, Reuse, Recycle. It’s a well-known phrase that we all try and follow in our day to day lives. But are our current recycling habits the best they can be? It’s a hot topic at Crowdscience - multiple listeners have contacted Crowdscience with questions about the ins and outs of recycling. We follow one listener’s food waste to a processing plant to investigate whether or not it could be processed in our own homes. But aside from the food waste, what about the containers it comes in? We investigate if food containers really need to be cleaned before we put them in recycling bins, or if that just wastes water. Recycling processes differ all over the world, so we hear from reporter Chhavi Sachdev in Mumbai, India, who follows her plastic waste to find out how plastic sorting and recycling is a whole economy of its own. But new technologies have meant that biodegradable and bioderived plastics are starting to appear in our packaging, and one Crowdscience listener wants to know which is better for the environment – traditional plastic that has been recycled, or bioplastic and compostable alternatives? And looking to the future, could we ever recycle our plastic waste at home and use 3D printers to make useful things out of our own waste? Marnie Chesterton delves into these questions with Circular Economy Project Manager Dr Rhiannon Hunt of Manchester Metropolitan University, to discover the details of recycling and unearth how we can make our own recycling as efficient as possible. With Dave Atkins, reporter Chhavi Sachdev and Dr Rhiannon Hunt. Presented by Marnie Chesterton and Produced by Hannah Fisher for the BBC World Service. [Image credit; Getty Images]

One CrowdScience listener finds herself unconcerned about much of the world’s problems, it leaves her wondering: am I a psychopath? Inspired by a previous episode on empathy, this listener asked is it true that psychopaths don’t empathise and what are the character traits of psychopathy? Marnie Chesterton talks with a diagnosed pro-social psychopath to find out. She also pays a visit to the Netherlands Institute for Neuroscience and gets into an MRI scanner to discover what is happening in her brain when she empathises. Studies suggest around 1 percent of the general population exhibit traits associated with psychopathy and that rises to 3-4 percent in the world of business. But is this really the case? Why is there so much stigma associated with psychopathy and do psychopaths even exist or is it just a convenient term to label those whose emotional range sits outside of the “norm”? Presented by Marnie Chesterton and produced by Caroline Steel for the BBC World Service. Guests: Julia Shaw Jim Fallon Valeria Gazzola Kalliopi Ioumpa [Image credit: Getty Images]

Anyone who has ever taken the Christmas lights out of the cupboard, only to discover they’re hopelessly tangled, will sympathise with this week’s listener Eric. He has a 45m garden hose that always seems to snarl up and snag when he waters his garden, and he wonders what he’s doing wrong? Marnie starts by discovering the important difference between tangles and knots, as she scales a cliff with an experienced climber who explains the way you tie rope is a matter of life and death. Physicists are also fascinated in how string becomes jumbled up and one man has even won an IgNobel award for his work in this field. Doug E Smith discovered that if you put a piece of string in a box then spin it around, its length, thickness and how long you shake the box for, all determine whether it will tie itself up. Not only that, the more the string becomes twisted, the more likely it is to cross over itself and become impossible to untangle. While tangles might be annoying in hair or cables, they’re also a fundamental part of human life. Our DNA is constantly folding itself to fit inside tiny spaces – there are two metres of the stuff inside every cell, where it’s packed down tightly, before it must untangle and duplicate for those cells to divide. It does this with the help of specific enzymes, and when the process goes wrong it leads to cell death. But scientists are also studying molecular tangles that might benefit us humans, and creating nano-sized knots that can be turned into nets or meshes with incredible properties. Producer: Ilan Goodman Presenter: Marnie Chesterton

Standing takes less energy than walking, so why does it feel more tiring? At least, it does for CrowdScience listener Nina. She can march for hours without getting tired, but her legs and feet get achy after just a short time standing still. It’s one of three walking-themed questions CrowdScience is tackling this week. Taking inspiration from our active listeners, Marnie Chesterton walks up a hill with Caroline Williams, author of a new book about why humans are designed to move. We find out how our whole system – body and brain – works better when we’re walking, compared to standing still. We’re probably set up this way because of our evolutionary history: hunting and gathering needed us to be ‘cognitively engaged endurance athletes’. We stop for a break.. but is it true that we shouldn’t sit down to rest during a walk? Our listener Sarah is a keen hillwalker but likes to take the weight off her feet every now and again. Her hillwalking friends disapprove, saying she should rest on her feet. Is this a myth CrowdScience can bust? And finally a question from listener Matteo: is walking or running better for your health? Numerous studies show significant benefits to both forms of exercise, but in the end, the best kind of exercise is the one you’re motivated to do. With Caroline Williams, Dr François-Xavier Li, Professor Dick Greene and Professor Duck-Chul Lee.

Food. For all of us it is a basic necessity and for those lucky enough, it is something we spend a lot of time planning and enjoying. CrowdScience listeners certainly have a lot of food related questions; in this buffet of an episode Marnie Chesterton opens the fridge door to pick the tastiest. Starting with the seemingly simple question of what makes us feel hungry, and ending in outer-space, Marnie investigates flavour, nutrition and digestion. After a year when watching TV has become a core activity for many people stuck in their homes, one listener wants us to find out if eating food whilst watching the TV affects our perception of taste. We then journey to the skies and ask if it is true that food tastes blander on aeroplanes, what does that mean for astronauts’ mealtimes? Back on earth, Marnie explores whether humans are the only animals that season their food. Tuck in your napkins and prepare to feast on a smorgasbord of scientific snacks. Presented by Marnie Chesterton and Produced by Melanie Brown and Hannah Fisher for the BBC World Service. Guests: Professor Charles Spence Dr Kristine Beaulieu Mr. Takashi Funahashi Ruben Meerman Chef Jozef Youseff

It took a while before it was officially recognised as a major symptom of Covid-19, but loss of smell has affected up to 60 percent of people who have had the virus. And for a significant portion, smell continues to be an issue for weeks or months after their recovery. So what’s going on and how can you get your sense of smell back? We tend to think of our sense of smell as something universal – if it smells bad to me, it probably does to you but that is not the case for CrowdScience listener Annabel, who wonders why things other people love to sniff, she finds disgusting. Anand Jagatia investigates the science of smell, gets up close to the world’s smelliest plant and finds out if smell training can help those with long-term issues after Covid. Contributors Ellie Byondin, supervisor of the Princess of Wales Conservatory at London’s Kew Gardens Thomas Hummel, University of Dresden Carl Philpott, from the UK’s Norwich Medical School Sissel Tolaas, artist and smell historian based in Berlin Noam Sobel, Weizmann institute of science Presented by Anand Jagatia and Produced by Marijke Peters for the BBC World Service

Scales don’t come planet-sized, so answering a question from David in Ghana may require some ingenuity, after all, calculating the weight of the Earth is a huge task. Using a set of weighing scales and a 400 year-old equation, Marnie Chesterton attempts to find out just how much the Earth weighs and is it getting heavier or lighter over time? But how would a planet gain or lose mass? Which tips the scales: meteorites falling from space or gases constantly escaping from our atmosphere? And does the answer have any implications for the future of Earth? Could the atmosphere eventually run out? Contributors: Anuradha TK, former project director at ISRO Matt Genge, geologist at Imperial College London Jon Larsen, researcher at the University of Oslo Anjali Tripathi, astrophysicist Ethan Seigel, journalist and astrophysicist Presented by Marnie Chesterton. Produced by Caroline Steel for the BBC World Service. [Image: Earth on scales. Credit: Getty Images]

They say life is sweet. Well that’s certainly the case for CrowdScience listener Trevor in Poland who wonders why he can’t stop reaching for the cookie jar. He grew up drinking fruit juice with added sugar but wonders whether his genes could be as important as his environment when it comes to his sweet tooth, especially since his wife seem to be satisfied with mainly savoury snacks. The World Health Organisation says added sugar should constitute a maximum of 5% of our daily energy intake because it can contribute to diabetes, heart disease and obesity. But that’s tricky when you consider it’s now in everything from salad dressings, to savoury sauces. Manufacturers have been promoting sugar alternatives for decades but recreating the unique taste and feel of it in the mouth are a challenge. Marnie Chesterton gets to try a brand new innovation – a so-called ‘rare’ sugar that has 70 percent of the sweetness but almost none of the calories. In nature, allulose is found in figs, but one producer has discovered a way to make it in the lab. Does it taste as good as it claims? Whilst switching to alternative sugars and sweeteners may reduce the calories, some researchers claim that tasting sweetness, wherever it comes from, can disrupt the body’s mechanism for regulating blood-sugar levels, increasing the risk for conditions like diabetes. Presented by Marnie Chesterton and produced by Marijke Peters for the BBC World Service

It's a topic that's taboo in many cultures, yet it's also something nearly every woman experiences – on average upwards of 400 times throughout her life: menstruation. Responding to a flood of questions from our CrowdScience listeners, Marnie Chesterton seeks to unpack how periods affect women physically, mentally and societally. Why did humans evolve to have periods when fewer than two percent of mammals share our experience of menstrual cycles? Is it really a good use of our limited energy reserves? What can the little Egyptian spiny mouse teach us about PMS symptoms? We hear why periods may reduce the number of faulty embryos that implant and how more menstrual cycles may even increase our chances of developing certain types of cancer. Finally, as the number of periods a woman has over the course of her life has more than quadrupled since the pre-industrial era, Marnie asks: Do we really still need to have them? Contributors: Dr Nadia Bellofiore, Hudson Institute of Medical Research at Monash University Dr Deena Emera, Buck Institute Lameck Kiula, Jambo for Development Sally King, Menstrual Matters & King's College London Dr Diana Mansour, New Croft Centre & Newcastle University Presented by Marnie Chesterton Produced by Sam Baker and Melanie Brown for the BBC World Service

As millions more of us move to live in densely populated cities, we almost inevitably face living in closer proximity to our neighbours. Neighbour noise can certainly be a source of annoyance – but could it even be damaging to our health? Increasing evidence suggests that unwanted noise can cause sleep deprivation, distraction and annoyance, as presenter Anand Jagatia finds out. He discovers that noise annoyance has a small but significant impact on our wider health – including our cardiovascular system – but that annoyance is not necessarily down to sound alone. Factors such as perception of the neighbourhood and relationships with our neighbours also play a part. CrowdScience has examined living with unwanted noises before, and we revisit our trip to the acoustics lab at the University of Salford in Manchester, UK. Here, we meet the researchers and engineers investigating the best ways to make our homes more pleasant for our ears whilst still maintaining the ‘buzz’ of city life. Contributors: Contributors: Professor Charlotte Clark, St George’s University of London Professor Trevor Cox, University of Salford Manchester Professor Bill Davies, University of Salford Manchester Dr Mags Adams, University of Central Lancashire (formerly University of Salford Manchester, at time of recording) Produced by Jen Whyntie and presented by Anand Jagatia for the BBC World Service.

You are a star. Literally. You are a carbon-based life form and those atoms of carbon in the molecules that make up your cells were formed by a nuclear fusion reaction at the heart of long dead stars. That goes for the oxygen in your lungs too. And the red blood cells that carry that oxygen to your tissues? They contain haemoglobin, and nestled at the heart of each molecule is an element (iron) formed by a supernova - the fiery explosion at the death of a star. Your body is a walking, thinking museum of some of the most violent events in the universe. This, as CrowdScience host Marnie Chesterton discovers, isn’t as special as it sounds. All of the stuff on the earth - the elements that make clouds and mountains and mobile phones – they all have an origin story. CrowdScience tells that story, starting with the big bang and ending with physicists, creating new elements in the lab. Find out the age of the elements and the distance they have travelled to make their current home on earth. Interviewees: Dr Dorota Grabowska, Professor Andrea Sella, Dr Chris Pearson, Dr Jacklyn Gates (Photo: Neutron star. Credit: Getty Images)

There are over 400,000 species of plant on earth, they’re on every continent including Antarctica. But humans only regularly eat about 200 species globally, with the vast majority of our nutrition coming from just three species. Many of the fruits, leaves and tubers that other plants grow are packed full of toxins that are poisonous to us, and would make us very ill if we ate them. But could we take out the poisons and create new, edible crops? That’s what CrowdScience listener Marija wants to know. Crowdscience dives into this topic, and uncovers the that many crops are poisonous, and why so few plants are eaten globally. Host Anand Jagatia finds that even the modern scientific processes of crop breeding are very slow. But science can now engineer plants at the genetic level by adding, silencing or removing specific genes. This ‘genetic modification’ is hugely controversial but can be highly effective. Anand finds a man who has spent decades making cotton seeds edible by removing the poisons they naturally produce in their seeds. This GM crop could help fend-off starvation. But sometimes introducing poisons can be as important as removing them, as we find in the genetically modified ‘BT eggplants’ in Bangladesh. The new gene makes the vegetable toxic to a major insect pest, so they are much easier to grow. But GM crops are not the perfect solution. They have problems of gene escape, can increase the use of environmentally damaging herbicide, and can be open to monopolisation. In some countries, particularly in Europe, GM crops are hugely controversial. Anand finds out whether these concerns stand up to science and looks at the counterpoint in developing countries in Africa, South Asia and elsewhere, where local farmers like Patience Koku in Nigeria have little time for some of the concerns around GM, particularly as they see poor harvests, poverty and starvation as the more pressing problems. Contributors: Professor Sandra Knapp, The Natural History Museum in London Professor Julie King, Nottingham University Professor Keerti Rathore, Texas A&M University Dr Yousuf Akhond, Bangladesh Agricultural Research Institute Professor Matthew Cobb, University of Manchester Patience Koku, Nigerian Farmer and member of the Global Farmer’s Network Alliance for Science Produced by Rory Galloway and presented by Anand Jagatia for the BBC World Service. Image: Farmer with Fruits. Credit: Arif Hossain, Farming Future Bangladesh.

Have you taken classes to learn a new sport or musical instrument or a language? It’s hard work! Why is it that as children we effortlessly absorb new skills and we don’t as adults? That’s what 50-something listener Gary Grief wondered about playing guitar. Do you need to play more frequently as an adult to attain the same level of expertise? Does the 10,000-hours theory still apply? Presenter and budding tabla-player Anand Jagatia embarks on a musical journey to discover what neuroscience can tell us about muscle memory and learning. Do musicians and sportsmen share the same challenges? By understanding what’s happening in the brain, can we learn how to learn better? With tabla-teacher Satvinder Sehmbey, neuroscientist Dr Jessica Grahn, viola-player Dr Molly Gebrian and sports scientist Prof Yannis Pitsiladis. Presented by Anand Jagatia Produced by Dom Byrne for the BBC World Service [Image: Adult and Child learning Piano. Credit: Getty Images]