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BBC World Service


We take your questions about life, Earth and the universe to researchers hunting for answers at the frontiers of knowledge.


CrowdScience

Crowdscience listener Ryosuke grew up in Japan, and spent his childhood summers catching cicadas in the park. For people in Japan, the sound of their chirping signals the first true summer day. But until they emerge, these enigmatic insects live underground - often for many years. Ryosuke wants to know how they know the time is right, and CrowdScience is on the case. 

Presenter Anand Jagatia pieces together the story of the species, and meets the small but dedicated group of academics worldwide who’ve been able to study them. 

In a field near Girona, Spain, he meets a scientist who’s spent the last twenty years counting them. How will a temperature probe help us work out when they might emerge, and what are they doing underground for so many years anyway? 

In nearby Barcelona, another scientist cuts open the stem of a tomato plant and Anand watches as the sap flows out. Could this be a clue to how cicadas sense what’s going on above ground? 

And he meets a cicada breeder in the US who has discovered a link between the life cycle of cicadas and the fruiting of a peach tree. Armed with that knowledge, can you really make time move faster for tree and insect alike? 

Presenter: Anand Jagatia 

Producer: Robbie Wojciechowski 

Editor: Ben Motley

(Photo:Cicada on Hosta Leaf - stock photo Credit: KenWiedemann via Getty Images)

How do cicadas know what season it is?

CrowdScience listener Limbikani in Zambia is always being told he has his Dad’s laugh, so he set us the challenge of trying to find out whether a laugh can be passed down in our genes or if it’s something we learn from our environment. 

Presenter Caroline Steel steps into the world of one of the world’s greatest laughter experts, Professor Sophie Scott, neuroscientist at University College London. In her office stuffed with memorabilia of a life filled with fun, they discuss how the shape of our bodies could play a role in how we laugh. 

Also joining the fun is Dr Gil Greengross, evolutionary psychologist at Aberystwyth University in Wales, UK. Gil tells us how Charles Darwin was the first person to question how laughter evolved. 

Caroline also speaks to Dr Nancy Segal, Professor of Developmental Psychology and Director of the Twin Studies Center at California State University, Fullerton. Nancy is an expert in studies that demonstrate the role of nature vs nurture in how who we are and how we behave. She tells the story of the ‘Giggle Twins’, who were separated at birth but found they laughed identically when they met three decades later. 

So does that mean that we really do inherit our laughs from our parents? 

Presenter: Caroline Steel 

Producer: Tom Bonnett 

Editor: Ben Motley 

Credit: The sound of rats laughing (slowed down so that our ears can detect the ultrasound) is courtesy of Dr. Jaak Panksepp

(Photo: Father and son on yellow background- stock photo Credit: Georgijevic via Getty Images)

Did I inherit my laugh?

In 2025, the crack team of intrepid presenters here on CrowdScience have been on some incredible adventures. They’ve wondered whether water is wet, and gone a hunt for a missing tangerine. They’ve wondered why animals swallow rocks, imagined what would happen if the earth spun backwards and pondered whether atoms are immortal. 

But, as the year draws to a close, Anand Jagatia is wondering… have they REALLY been paying attention? Time to put them to the test! 

In this special programme, Anand gathers the other four presenters into a studio together – Caroline, Alex, Marnie and Chhavi, for an end-of-year quiz – and you can join in at home! 

Presenters: Anand Jagatia, Caroline Steel, Alex Lathbridge, Marnie Chesterton and Chhavi Sachdev 

Producer: Emily Knight 

Editor: Ben Motley

(Photo: CrowdScience presenters in the studio with purple background Credit: BBC)

The CrowdScience quiz of the year

When some people are wandering around in shorts and a t-shirt, others are wrapped up in warm coats and jumpers. How come our responses to cold weather are so different? 

People have been living in cold environments for thousands of years. So why do some of us struggle with the cold more than others, and what, if any, adaptations have our bodies made to cope in freezing temperatures? 

CrowdScience listener Anne from the UK is amazed by the warm houses of her neighbours, and wants to know whether her background might have affected her perspective on the cold. 

Caroline Steel investigates, visiting a laboratory in Loughborough University, UK, that pushes the body to the extreme. Dr Matt Maley explains what happens inside our systems to help us survive the plummeting thermostat and how this adaption can vary from person to person. 

But it’s not just biological. Our culture impacts our experience of cold too. CrowdScience heads to Norway to meet the global community on the icy Arctic island of Svalbard. There Caroline meets Associate Professor Gunhild Sætren at the Arctic Safety Centre to find out the important role appropriate clothing plays in being prepared for the chilly weather. 

And we speak to Dr Cara Ocobock at the University of Notre Dame, USA, who tells us about her research comparing Finnish reindeer herders and office workers reactions to cold temperatures. 

Presenter: Caroline Steel 

Producer: Hannah Fisher 

Editor: Ben Motley

(Photo: Woman enjoying winter playing in fresh snow. Credit: Olga Pankova/Getty Images)

How do we adapt to the cold?

Smashing up guitars is a classic rock star activity, but how about drowning them? Seven-year-old listener Cornelius asked CrowdScience to find out what happens if you play a guitar underwater. Could this be the next avant-garde music sensation? 

Host and amateur musician Caroline Steel tackles Cornelius’ question with the help of one increasingly soggy guitar. The UK’s National Physical Laboratory is our first port of call, with a guitar-sized water tank at the ready, and acoustic scientists Dr Freya Malcher and Ben Ford helping tackle our questions. 

Since an acoustic guitar’s sound is amplified by its internal chamber, what happens as that chamber starts to fill with water? How about if the whole guitar - strings, body and all - is submerged? What difference does it make if our ears are listening above or below the water? And can special water-adapted microphones help us explore this unusual question, before our guitar disintegrates? 

Our guitar then heads off on tour to Denmark, where the band Between Music have teased out questions just like these for their underwater music project, Aquasonic. We talk to violinist and Innovative Director Robert Karlsson, and singer Nanna Bech, who also plays a unique subaquatic instrument. With their help, we discover how to get the best out of a submerged guitar, and find out whether other instruments are better suited to the life aquatic. 
 
Presenter: Caroline Steel 
Producers: Cathy Edwards and Florian Bohr 
Editor: Ben Motley 
 
(Photo: Caroline Steel and Nanna Bech in an Aquasonic aquarium playing a guitar)

Can you play the guitar underwater?

Can we turn the world’s deserts green? CrowdScience listener Youcef is captivated by the idea of bringing water back to Earth’s driest landscapes. With sea levels rising and huge stretches of land drying out each year, he wonders whether redirecting seawater inland could offer a solution to both problems. Presenter Alex Lathbridge sets out to investigate starting with a kettle of salty water. 

Alex speaks to scientists about how deserts form, and how human actions like overgrazing can tip a fragile grassland into a barren landscape. He learns how the brightness of bare sand affects local weather, reducing cloud formation and rainfall. Researcher Yan Li reveals how huge solar and wind farms could darken and roughen the Sahara’s surface enough to double its rainfall, potentially kickstarting a self-reinforcing cycle of vegetation and moisture. 

But what about deserts where clouds already drift overhead? In the Atacama, one of the driest places on Earth, geographer Virginia Carter shows how fog harvesting nets can coax litres of fresh water from the air. 

Alex also investigates desalination, where professor Chris Sansom is trying to harness solar power to remove the salt from seawater without burning vast amounts of fossil fuels. It is promising, but can it reduce the impact of rising sea levels? And what do you do with all the salt that’s left over? 

Climate scientist Alan Condron proposes an even wilder idea: towing kilometre-sized icebergs from Antarctica to parched nations. His models show it might be possible, but the logistics verge on science fiction. 

Finally, plant scientist Zinnia Gonzalez Carranza warns that greening deserts isn’t just about adding water. Introducing new species, even hardy ones like mesquite, can trigger ecological chaos and harm the very communities who depend on these landscapes. 

Presenter: Alex Lathbridge 
Producer: Sam Baker
Editor: Ben Motley 

(Photo: Palm trees growing in cracked, parched earth and the sun rising behind them. Credit: Danymages/Getty Images)

Can we turn deserts green?

When listener Sakura’s husband came home from his morning walk in Cambridgeshire, UK, he told her about a massive rainbow he’d seen. But when he showed her a picture, she didn’t think it was particularly large. So how big is a rainbow really? Are they always the same size? And if some are bigger than others, is there a limit? 

To find the answers, presenter Marnie Chesterton meets independent rainbow expert Philip Laven in a pitch-black studio to simulate how a rainbow is formed. He demonstrates how they are created by sunlight, reflecting and refracting in millions of little water droplets. 

But what does that mean for their size? Raymond Lee, retired professor from the US Naval academy, says that rainbows are not objects and don’t have a linear size, just a specific angular size that’s relative to the person seeing it. But Marnie doesn’t give up so easily – some rainbows still look bigger than others. 

In her journey to discover other ways to size up a rainbow, Marnie hears from Australian aerial photographer Colin Leonhardt who stunned the world with a beautiful picture. Next, assistant professor Ping Wah Li from The Chinese University of Hong Kong explains why it’s possible to come across more than one rainbow at a time. 

And finally, atmospheric scientist Harald Edens shares another way to consider size, as well as how much he struggles to explain the complexity of rainbows to his four-year old daughter. 

Presenter: Marnie Chesterton 

Producer: Florian Bohr 

Editor: Ben Motley

Photo: Rainbow of Dreams - stock photo stock photo Credit: Laurent Fox via Getty Images)

How big is a rainbow?

Tears of joy, tears of sadness, tears of frustration or tears of pain - humans are thought to be the only animals that cry tears of emotion. CrowdScience listener Lizzy wants to know: why do we cry for emotional reasons? What is its evolutionary benefit? And why do some people cry more than others? 

It turns out that humans cry three types of tear: basal, reflex and emotional. The first kind keeps our eyes nice and lubricated and the second flushes out irritants such as fumes from the pesky onion, but the reasons for emotional tears are a bit harder to pin down. 

Using a specially designed tear collection kit, presenter Caroline Steel collects all three kinds of tears. With them safely stashed in tiny vials, she heads to the Netherlands, to Maurice Mikkers’ Imaginarium of Tears. Looking at her crystallised tears under a microscope will hopefully unveil a mystery or two. 

Marie Bannier-Hélaouët, who grew tear glands for her PhD, explains how the nervous system processes our emotions into tears. But why should we cry for both happiness and sadness, and for so many other emotions in between? Ad Vingerhoets, Professor of Clinical Psychology at Tilburg University, suggests we cry for helplessness - our bodies do not know how to process such intensity of feeling. 

But do these tears bring relief? Lauren Bylsma, Associate Professor of Psychiatry at the University of Pittsburgh, has been studying heart rates during crying episodes to find out. With her help, we also explore if women do in fact cry more than men, and why that might be. 

Presenter: Caroline Steel 

Producer: Eloise Stevens 

Editor: Ben Motley 

Photo: Fisheye woman having a cry - stock photo Credit: sdominick via Getty Images)

Why do we cry?

Tsunamis destroy buildings, habitats and danger to everything in its path on land. But how do they affect life under the water? That's what CrowdScience listener Alvyn wants to know, and presenter Anand Jagatia is searching beneath the waves for answers. Anand meets Professor Syamsidik who is learning about how tsuanami waves are formed to help protect against future disasters. He runs the Tsunami and Disaster Mitigation Research Center at Universitas Syiah Kuala, Indonesia. With him at this state-of-the-art lab is Dr David McGovern, expert in ocean and coastal modelling at London South Bank University. David tells Anand how the energy of a tsunami is spread across the entire water column. To explain the forces at play, Anand chats to Professor Emile Okal a seismologist from Northwestern University in the United States. Tsunami wave can move as fast as 800 kilometres an hour but, despite this, out at sea you might not notice it - but can the same be said for marine life? We follow the wave as it nears land and all that force is contracted and begins to show its might. Professor Suchana 'Apple' Chavanich from Chulalongkorn University, Thailand was one of the first people to swim off the Thai coast after the 2004 tsunami and remembers how coral reefs were battered.
In Japan, after the 2011 Tohoku Earthquake and Tsunami as the water retracted it pulled with it tons and tons of debris into the water. The fishing communities of the Sanriku Coast lost almost everything, their equipment was destroyed and the water was heavily polluted. Anand meets Hiroshi Sato who set up the Sanriku Volunteer Divers, a team of people who dragged the debris out of the water. One of them was diver and journalist Bonnie Waycott who tells her story of witnesses the destruction first hand and trying to rescue the fishing industry with Hiroshi. Finally, we learnt that the effect of modern tsunamis carries far further than people might have imagined. On the west coast of the United States Professor Samuel Chan is an expert in invasive species at Oregon State University. He explains how modern infrastructure is contributing to some incredible migrations. Presenter: Anand Jagatia Producer: Tom Bonnett Editor: Ben Motley

Photo: USA, California, Sonoma County, Bodega Bay, tsunami evacuation panel - stock photo Credit: Brigitte MERLE via Getty Images)

Do tsunamis affect marine life?

In your final moments, they say, you may walk down a tunnel of light. You might rise above your body, watching the scene below before passing into another world. Perhaps you’ll be met by glowing figures, see your life flash before your eyes, or feel a deep, unearthly calm. 

These are the stories of people who’ve reached the edge of death and returned. They’re not rare, nor random, and they have a name: near-death experiences. 

CrowdScience listener Steven in Chile first heard of them during a CPR class and wondered, are they fictitious? 

Psychologist Susan Blackmore once had an out-of-body experience as a student in Oxford, UK — floating above herself before soaring over the rooftops and dissolving into the universe. That single moment changed everything. She’s spent her career trying to understand what happened, and she believes such experiences are explainable. 

At the University of Michigan in the US, neuroscientist Professor Jimo Borjigin has done what few have dared: record the dying brain in action. Her studies show that even after the heart stops, the brain can produce powerful surges of coordinated activity, bursts that might explain the lights, the tunnels, and the sense of peace. She believes near-death experiences could become one of science’s most intriguing scientific frontiers for research into consciousness. 

At University College London in the UK, neuroscientist Dr Christopher Timmermann is exploring similar states using psychedelics, pushing the boundaries between self and oblivion to identify what induces a near-death experience and what we can learn about our consciousness along the way. 

Near death experiences, a paranormal mystery or explainable phenomenon? 

Presenter: Caroline Steel 
Producer: Harrison Lewis 
Editor: Ben Motley

(Photo: Gap in the wall - stock photo Credit: peterschreiber.media via Getty Images)

Are near-death experiences real?

Have you ever been out driving and noticed your mind… wandering? CrowdScience listener Sian Gardiner has. When travelling to visit her parents she has to cross a very large, very obvious bridge. But there are times when she finds herself on the other side with no memory of having gone over it. How is that even possible? 
Presenter Geoff Marsh buckles up to find out. He travels through the science of how driving becomes second nature, brakes sharply when he realises he’s not necessarily in conscious control at 70mph, and tries to refocus when he discovers why drivers don’t always see things that are staring them in the face. He also asks what’s happening when our mind drifts away from the road, and what can be done to help drivers pay more attention and reduce accidents. 

Presenter: Geoff Marsh
Producer: Anna Lacey
Sound design: Peregrine Andrews

(Photo: A woman sits in her car, looking through window glass with rain drops. Credit: Getty Images)

Why Do Drivers Zone Out?

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