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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

Listener Jude in Canada wants to know why some animals are black and white. Why do zebras risk being so stripy? Why do pandas have such distinct marking? And do they have something in common? 
 
Presenter Caroline visits Pairi Daiza, a zoo in Belgium. Together with her guide for the day, Johan Vreys, she looks at these weird and wonderful animals up close. First, she visits three zebras having breakfast. Ecologist Martin How from the University of Bristol explains his ingenious experiment involving horses with zebra blankets. Next on the tour is the giant panda which, according to Prof Tim Caro from the University of Bristol, looks at the way it does to camouflage in snowy forests in China. But there are many more animals to see, and many more reasons to be monochrome, including the penguin and its tuxedo-like colouration. Hannah Rowland, senior lecturer at the University of Liverpool explains that it might have more than just a single function. It turns out, scientific answers aren’t always black and white. 

Presenter: Caroline Steel 
Producer: Florian Bohr 
Editor: Ben Motley

(Photo: The zebra was running gracefully running in the green water. Credit: Surasak Suwanmake/Getty Images)

Why are some animals black and white?

Sometimes in science, when you try to answer one question it sparks even more questions. 

The CrowdScience inbox is a bulging example of that. We get tons of new questions every week and many of those are following up on episodes we’ve made. Sometimes you want us to go deeper into part of the answer, or sometimes a subject intrigues you so much that it inspires further questions about it. 

In this episode presenter Caroline Steel is on a mission to answer some of those questions. 

The CrowdScience episode How do fish survive in the deep ocean? led listener Ivor to wonder what sort of vision deep sea fish might have. On hand to answer that is Professor Lars Schmitz, Kravis Professor of Integrated Sciences: Biology, at Claremont McKenna College in the USA 

Sticking with vision, we also tackle a question inspired by the CrowdScience episode Do we all see the same colour? For years listener Catarina has wondered why her eyes appear to change colour. Professor Pirro Hysi, ophthalmologist at the University of Pittsburgh, sheds some light on that subject. 

In India, Rakesh listened to the CrowdScience episode Will the Earth ever lose its moon? and wondered about Jupiter’s many moons. The European Space Agency’s Ines Belgacem is working on a new mission to study Jupiter’s moons. She explains which of the giant planet’s ninety seven moons are ones for Rakesh to watch. 

We also hear how the episode Why can’t my dog live as long as me? caught the attention of listener Lisa... and her cat. She had us falling in love with the long history of falling cats and the scientists who study them. Caroline is joined by Professor Greg Gbur, physicist at the University of North Carolina, Charlotte in the USA and author of Falling Felines and Fundamental Physics. 

Could this episode of follow up questions lead to an episode investigating the follow up questions to these follow up questions? Have a listen and, who knows, maybe you’ll find yourself inspired to email crowdscience@bbc.co.uk 

Presenter: Caroline Steel 

Producer: Tom Bonnett 

Editor: Ben Motley

(Photo: Innovation and new ideas lightbulb concept with Question Mark - stock photo Credit: Olemedia via Getty Images)

Answers to even more questions

CrowdScience listener David is a bird whisperer. 

On his family farm in Guinea, he would mimic the call of the black-headed weaver. He could replicate it so well that the birds would fly in close, curious to find out who was calling. David has been wondering if he was actually communicating with the weaver. 

In the foothills of the Austrian Alps is a research hotspot with a curious history. It was here that a scientist first began studying birds in their natural environment. That work continues today with Andrew Katsis from the University of Vienna, who knows the local flock of greylag geese by name. His research shows that animals aren’t just anonymous members of a group, they have personalities, relationships, and the ability to recognise one another. 

But what else do birds know? Thomas Bugnyar, professor of social behaviour and animal cognition, spends his time trying to get inside the mind of ravens. His work suggests they can understand their surroundings, make rational decisions, and even solve complex problems. 

Plus, we meet Ellie, a cockatoo with the ability to use a touchscreen computer to “talk.” She has a working vocabulary of more than 1,500 words. And when she presses a button, it would appear she is not just pecking at random, she is choosing purposefully, responding in ways that suggest birds may not only understand us, but communicate back. 

Presenter: Caroline Steel 
Producer: Minnie Harrop and Harrison Lewis 
Series producer: Ben Motley

(Photo: Close up of Greylag goose with blue background Credit: Harrison Lewis, BBC)

Do birds understand us?

CrowdScience listener Kerry started thinking about his sentimental attachment to his possessions when he began sorting through an old trunk, full of objects from his past. He wants to know why we get so attached to things that often have no use anymore and why it’s so hard to give them away. 

Anand Jagatia investigates why the objects we accumulate during our lives mean so much to us. 

He talks to psychologists Mary Dozier and Melissa Norberg and finds out that our possessions offer stability and comfort from the earliest age. That keepsake you brought home from your holiday may also stir memories about days gone by - and that’s one reason why we may find it hard to part with the things we own, because they help us to access our emotions. And the items we collect through our lives can come to represent our identity too. 

Anand visits the Museum of Broken Relationships in Zagreb, Croatia, where people from all over the world have donated possessions from relationships that ended, whether romantic or family, and discovers that sentimental attachment is universal. 

Presenter Anand Jagatia 

Producers Jo Glanville and Imaan Moin 

Editor Ben Motley

(Photo: Memories box in book shelf - Credit: Jan Hakan Dahlstrom via Getty Images)

Why am I so sentimental?

Milk: drink a lot of it and we’ll grow big and tall with strong bones. That’s what many people are told as children, but just how true is this accepted wisdom? CrowdScience listener JJ in Singapore is sceptical. He wants to live a healthy life for as long as possible, and he’s wondering whether drinking cow’s milk will help or hinder him on this mission. 

All mammals produce milk, and our mother’s milk is our very first drink as babies. So what actually is the white stuff? Mary Fewtrell, professor of paediatric nutrition at UCL, gives presenter Chhavi Sachdev the lowdown on just how fundamental breastmilk is to us all.
But are we meant to continue drinking milk from other animals once we grow up? This behaviour of ours is rare among mammals… so Christina Warinner, professor of evolutionary biology at Harvard University, tells us when in our history cow’s milk entered our diet, and how we even came to be able to digest it. 

And is there any truth in the accepted wisdom that cow’s milk will give us stronger bones? Karl Michaelsson, professor of medical epidemiology at Uppsala University, has researched just this – and the answer isn’t what you’d expect. Karl helps Chhavi sift through the complex evidence to see whether milk is actually any good for us.

Presenter: Chhavi Sachdev
Producer: Sophie Ormiston
Editor: Ben Motley

(Photo:Lady milking cow, Nadiad, Gujarat, India)

Will drinking milk help me live longer?

What will remain of us hundreds of millions of years from now? And how can we be so certain that we are the first technologically advanced species on Earth?

These unsettling questions have been haunting listener Steve. If fossils can be lost to deep time through erosion and subduction into the Earth’s mantle, how would anyone — or anything — ever know that we had been here? And if an earlier species had built a civilization that rose and fell, would we even be able to find traces of it?

To investigate, CrowdScience presenter Caroline Steel speaks to the scientists trying to answer these questions, while producer Sam Baker goes fossil hunting on the Jurassic Coast in the UK. 

Caroline speaks with astrophysicist Adam Frank at the University of Rochester in the US, who along with NASA scientist Gavin Schmidt developed the Silurian hypothesis – the idea that if an advanced species had existed deep in Earth’s past, they might have vanished without leaving a trace. 

But palaeontologists Jan Zalasiewicz and Sarah Gabbott from the University of Leicester in the UK argue that humans are already leaving an indelible mark in the form the chemical and material fingerprints we’re pressing into Earth’s crust. They contend that the ‘technofossils’ we are producing will last a very long time indeed.

Along the way, Caroline and producer Sam discover just how rare fossils really are, how even the tiniest particles of pollution will give us away to far-future explorers, and why car parks might be our ultimate legacy. What they find is at once unsettling and oddly comforting: humanity could be fleeting, but our impact probably won’t be.

Could we really have missed evidence of an ancient civilization? And what strange clues will we leave behind for whoever, or whatever, comes next? We explore Earth’s geological memory to find out.

Presenter: Caroline Steel
Producer: Sam Baker
Editor: Ben Motley

(Photo: Old phone embedded in concrete layer with defocused landscape background Credit: Petra Richli Via Getty Images)

How long will traces of our civilisation last?

Camouflage isn't just for chameleons! Military forces around the world deck their soldiers out in those distinctive green and brown uniforms, to give them the best chance of staying safe, and remaining undetected. But how do they work? Why do they look so different from country to country? And why do you still see soldiers wearing it in the city, when it can't possibly work as camouflage?
 
These are the questions in the mind of Crowdscience listener Paul, in Uganda. In his home of Kampala he often sees soldiers on patrol. As a botanist, he's fascinated by the nature-inspired designs, and he wants to know how they came to be. So Alex Lathbridge sets off to find out.
 
At Camolab at the University of Bristol, Laszlo Talas talks Alex through the history of battle-dress. There have been some extraordinary designs over the years, some of them quite beautiful in their way, and many with hidden easter eggs printed into the design!
 
In a patch of forest on the outskirts of Prague, Alex gets to try some of the latest gear out for himself. Fully kitted out in ghillie suit, camouflage chaps, face mask and goggles, he tries to disappear into tue background. With the help of 4M Tactical, the company who manufacture a cloak currently in use in Ukraine. It has the power to make you invisible, not just in the visible spectrum, but in the infrared too. With high tech sensors and infrared cameras now a staple of the modern battlefield, clothes like this are becoming essential.
 
Not all camouflage technology belongs to the military. Futuristic clothing company Vollebak in London are using 'the fabrics of the future' to design high tech streetwear for savvy 21st century urban warriors. Founder Steve Tindall shows Alex their prototype Thermal Camo Jacket, which uses hundreds of layers of graphene to give the illusion of heat, or cold. Steve says that hiding in plain sight is less about concealing yourself from human eyes, and more about avoiding the pervasive sensors and constant surveillance that are increasingly a feature of urban living.
 
Meanwhile in Sweden, they're taking the inspiration from chameleons more literally. Hans Karis, deputy research director of the Swedish defence institute FOI, introduces Alex to their Adaptive Camouflage, interwoven with a network of tiny coloured LEDs to change colour at will. It's not on the market yet, but perhaps chameleon soldiers will be a thing of the future.
 
Presented by Alex Lathbridge
Produced by Emily Knight

(Photo: Thermal imaging of people in the woods)

How does camouflage work?

When listener Rob from Devon, UK, heard of a newly detected planet light years away, he was struck by the sheer scale the light must travel to reach us here on Earth. It got him wondering: How long does light last? What is the oldest light we have ever observed? And does light ever die? 

To find out, presenter Anand Jagatia calls on some of the brightest minds in astronomy and physics. 

Astronomer Matthew Middleton from the University of Southampton explains how scientists still struggle to define exactly what light is. What we do know is that light comes in many forms, and choosing the right kind can peel back the cosmic curtain, revealing the universe’s deepest and darkest secrets. That knowledge will prove vital in Anand’s search for the oldest light ever observed. 

At the European Southern Observatory in Chile, staff astronomer Pascale Hibon gives Anand a behind-the-scenes look at the Very Large Telescope, one of the most advanced optical instruments on Earth, perfectly placed under some of the clearest skies on the planet. Light from the objects Pascale studies has often travelled for billions of years, making her images snapshots of the distant past.

If light has crossed the vastness of the universe to reach us, it must be unimaginably ancient. But what will become of it in the far future? Could we trap it and preserve it forever? Miles Padgett at the University of Glasgow, has spent his career trying to pin it down. As Anand discovers, physics can be more philosophical than you might expect. 

Presenter: Anand Jagatia 
Producer: Harrison Lewis 
Editor: Ilan Goodman

(Photo: An area of deep space with thousands of galaxies in various shapes and sizes on a black background. Most are circles or ovals, with a few spirals. Credit:G. Östlin, P. G. Perez-Gonzalez, J. Melinder, the Jades collaboration, M. Zamani/ESA/Webb, Nasa and CSA)

How long does light last?

CrowdScience listener Rit, from Pune in India, is staring out of his window at the falling rain. It’s been pouring for four days now, and shows no sign of stopping. The laundry is piling up, all his shoes are wet, and he’s worried about the effect it’s having on the environment, and on agriculture. When it rains like this, the animals suffer, and the crops are destroyed. 

Cloud seeding and Weather Engineering are hot topics right now, and can bring the rain to places that need it. But Rit wants to know whether we can artificially stop the pouring rain, especially in an emergency. Following the devastating floods in Texas, it’s clearly not just a problem for countries with a monsoon season. 

Presenter Chhavi Sachdev is also sitting in a downpour at home in Mumbai. She dons her rain jacket and rubber boots to try and find out whether science can help Rit with his question. From controlling the clouds in India, to bringing rain to the deserts of the UAE, to firing high-powered lasers into the skies above Geneva, we find out what weather engineering is really capable of. 

With thanks to: 

Dr Thara Prabhakaran, from the Indian Institute of Tropical Meteorology 

Alya Al Mazroui, Director of the UAE Research Program for Rain Enhancement Science 

Jean-Pierre Wolf, Applied Physics Department of the University of Geneva 

Presenter: Chhavi Sachdev 
Producer: Emily Knight 
Series Producer: Ben Motley

(Image: Girl carrying umbrella while standing on road against trees during rainfall. Credit: Cavan Images/Getty Images)

Can we stop the rain?

CrowdScience listener Jon started wondering how our teeth are created while he was in the dentist’s chair. It took his mind off the drilling. He wants to know how our teeth are made, what goes into them and how come we only get two sets of teeth when other animals, like sharks, grow thousands of new ones throughout their lives.

Anand Jagatia goes back to prehistoric times to discover how the story of teeth began millions of years ago. Palaeontologist Yara Haridy explains that teeth weren’t designed originally for eating at all, but as a kind of armour on the exoskeletons of fish that was also sensitive to the environment. It turns out that our teeth in fact are part of our evolutionary success story. Biological anthropologist Peter Ungar reveals that we flourished as a species because our teeth are designed to get the maximum energy from our food. 

Anand discovers how teeth can even be grown in a lab when he meets researchers Ana Angelova Volponi and Xuechen Zhang whose team has managed to replicate the environment in which teeth develop. He also talks to Katsu Takahashi who has discovered a method for developing a third set of teeth. It’s a whole new way of creating teeth that will change the way we make them. 

Presenter Anand Jagatia 
Producer Jo Glanville 
Editor Ben Motley 
Studio Manager Bob Nettles 
Production co-ordinator Ishmael Soriano 
Translation, Katsu Takahashi interview Bethan Jones

How are teeth made?

2024 is the biggest election year in history. From Taiwan to India, the USA to Ghana, by the end of the year almost half of the world’s population will have had the chance to choose who governs them.
 
But there are a huge number of possible voting systems – and listener James wants CrowdScience to find out which is the fairest.
 
To do so, we create a fictional country called CrowdLand to try out different electoral systems. Presenter Caroline Steel consults mathematician David McCune and political scientists Eric Linhart and Simon Hix, and we hear from listeners around the world about how they vote in their respective countries. Can we find the perfect voting system for CrowdLand?
 
Contributors:
Prof David McCune, William Jewell College, USA
Prof Eric Linhart, University of Technology Chemnitz, Germany
Prof Simon Hix, European University Institute, Italy
 
Actors:
Charlotte Bloomsbury
Ross Virgo
 
Presenter: Caroline Steel
Producer: Florian Bohr
Editor: Cathy Edwards
Production Co-ordinator: Ishmael Soriano
Studio Manager: Donald MacDonald

(Image: Hand of a person casting a vote into the ballot box during elections, Thailand Credit: boonchai wedmakawand via Getty Images)

What's the fairest voting system?

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