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Lyt når som helst, hvor som helst 

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 Paul from Uganda is fascinated by military uniforms. The outfits of so many different armies, from different countries all around the world, often look remarkably similar – mottled shades of olive green camouflage. 

Where did it come from? How does it work as camouflage? And what inspired it?

Alex Lathbridge delves into the science, the history and the future of camouflage.

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’s the oldest light we’ve 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 describes himself as “a kid in a sweet shop” when it comes to physics, and that enthusiasm comes in handy, because 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. In a sense, she’s pretty much a time traveller. 

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? 

“If we knew what light is, that might be an easier question to answer,” says Miles Padgett at the University of Glasgow, who has spent his career trying to pin it down. As Anand discovers, physics can be more philosophical than you might expect. 

From redshifted galaxies at the edge of the observable universe to exotic materials that can slow light to walking pace, CrowdScience explores whether we can catch light, how it changes over time, and why truly understanding it remains one of physics’ most stubborn challenges. 

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

(Image: 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. More distant galaxies are smaller, down to being mere dots, while closer galaxies are larger and some appear to be glowing. Red and orange galaxies contain more dust or more stellar activity Credit:ESA/Webb, NASA & CSA, G. Östlin, P. G. Perez-Gonzalez, J. Melinder, the JADES Collaboration, M. Zamani (ESA/Webb))

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 via 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?

What comes to mind when you imagine the future of humanity? Could a computer make your mind more efficient? Enhance your cognition? Or cure a disorder you've been grappling with all your life? CrowdScience listener Mariana from Mexico hopes that one day technology will be able to help improve our brains. 

Presenter Alex Lathbridge seeks out some of these brain boosters, exploring emerging technologies in deep brain stimulation at City St George’s University of London in the UK. Professor Francesca Morgante and Dr Lucia Ricciard explain how they’re using technology to treat Parkinson’s. 

And could brain technology help with even the most enigmatic elements of our minds? Dr Robert Hampson at Wake Forest University in the USA takes us through his research in restoring memory impairment. 

Along the way we interrogate the ethical implications of the breakneck speed of progress in brain augmentation research with researcher Anders Sandberg from the Institute of Future Studies in Sweden. 

Presenter: Alex Lathbridge 
Producer: Emily Bird 
Series Producer: Ben Motley

Could technology improve our brains?

The epic space story of a sci-fi dream that changed spaceflight forever. Told by the Nasa astronauts and team who made it happen. Our multi-award-winning podcast is back, hosted by space scientist Maggie Aderin-Pocock. She tells the story of triumph and tragedy - of a dream that revolutionised modern space travel forever.

You can listen to the trailer here. To hear episodes, search for 13 Minutes Presents: The Space Shuttle, wherever you get your BBC podcasts. 
 
13 Minutes Presents: The Space Shuttle is a BBC Audio Science Unit production for the BBC World Service. 
 
Theme music by Hans Zimmer and Christian Lundberg, and produced by Russell Emanuel, for Bleeding Fingers Music. 
 
Archive: 
Mission audio and oral histories, Nasa History Office.

Trailer: 13 Minutes Presents: The Space Shuttle

Your whole life is governed by spin. The rotation of our planet tells you when to wake up, and Earth’s orbit around the Sun is the reason why some of us dig out a jumper for half the year and a t-shirt for the rest. But what if that all changed? 
 
That’s exactly what 8-year-old Geronimo in Ecuador wants to know. He and his dad, Fabian, have got themselves dizzy trying to figure out what would happen if the Earth stopped spinning, or better yet, started spinning in the opposite direction. Would everyone fly off into space? Would school be at night? Eager for answers, they decided to ask CrowdScience. 

Presenter Anand Jagatia embarks on an interstellar journey, blasting off with the celestial origins of spin itself. Astronomer Amy Bonsor from the University of Cambridge in the UK explains how Earth’s rotation began, with collapsing clouds of gas, planetary pile-ups and crushing gravitational force. 

At Keele Observatory, things get apocalyptic. Anand meets astronomer Jacco van Loon, who explains what would happen if Geronimo somehow waved a magic wand and brought Earth’s rotation to a halt. With months of unbroken daylight or darkness, devastating storms and even the loss of the Earth’s magnetic shield, it’s like the script of a disaster movie. 

Wave that magic wand again and we imagine a world where the Earth not only stops... but starts spinning the other way. Meteorologist Joao Basso from the University of Leipzig in Germany walks us through a mind-bending 2018 study that tells us the surprising things that would happen to the global climate. 

Presenter: Anand Jagatia 
Producer: Harrison Lewis 
Series Producer: Ben Motley

What if the Earth spun backwards?

Here's a conundrum that has captivated scientists: when Earth formed 4.5 billion years ago, our planet was essentially a ball of molten rock. Any water that might have been present during the planet's formation would surely have boiled away immediately. Yet today, water covers about 70% of Earth's surface. 

So where did all this water come from? And more intriguingly, when did it arrive? Listener Bill in the USA wants to know, and Presenter Caroline Steel is after answers. 

Assistant Professor Muhammad Abdul Latif is an early earth physicist at United Arab Emirates University. He explains how his modelling has helped us to understand when water first appeared in our universe. 

The early earth was not a water-friendly place - a hellscape of molten rock, volcanic eruptions and constant bombardments from comets and asteroids, with high levels of solar radiation. These conditions would have evaporated the water. And according to Professor Richard Greenwood at Open University, our earth’s molten iron core would have been a ball of rust if there had been water in the proto-earth mix. 

So if the water hasn’t always been here, where did it come from? 

At the Natural History Museum in London, Professor Sara Russell has been comparing the isotopic "fingerprint" of Earth's water with water found in the asteroid Bennu, captured and brought back by the recent Osiris Rex NASA mission. It’s a good match for earth’s water, but could it really be the answer to our question? 

Presenter: Caroline Steel 
Producer: Marnie Chesterton 
Editor: Ben Motley

(Image: Man overlooking the sea from cliff top. Credit: Gary Yeowell via Getty Images)

Where did Earth’s water come from?

Listener Dickson Mukisa from Uganda has been gazing up at the stars. But he’s not making wishes. He wants to know whether we can harness their energy, in the same way we do with our OWN star – the sun. After all, they may seem small and twinkly to us, but each one is a gigantic flaming ball of energy, with a power outputs averaging around 40 quadrillion kilowatt-hours per year – EACH! With somewhere between 100 and 400 BILLION stars in our own galaxy alone, that’s a lot of power! Can we get ‘solar power’ from stars that are such a long way away from earth? And what might we use it for? 

Alex Lathbridge heads to the University College London Observatory, to peer through the eyepiece of an enormous telescope and see some stars for himself. Professor Steve Fossey explains just how much of the light energy of the stars reaches us on earth. In other words, how BRIGHT they are. 

Once the starlight reaches earth of course, we have to capture it. Could traditional solar panels do the job? Alex meets Professor Henry Snaith from the University of Oxford, to find out about the future of photovoltaic technology, and why it could all be heading out to space. 

Once in space, things start getting weird! What if we made an enormous fleet of solar panels, and put them all into orbit around a star, soaking up every last drop of that precious energy? That might sound like science fiction, but the idea has been around for decades. It’s called a Dyson Sphere, or Dyson Swarm. Swedish researcher at the Insitute for Future Studies, Anders Sandberg explains how we might be able to build one around a neighbouring star... in around 10,000 years or so. 

But maybe it’s not all about light. Finally, Alex explores the mysterious, invisible energy of the ‘solar wind’, with Pekka Janhunen, Finnish physicist and inventor of the “E-Sail”, which might be able to harness the power of the stellar wind, too. 

Presenter: Alex Lathbridge 
Producer: Emily Knight 
Series Producer: Ben Motley

(Image: Astronomer looking at the starry skies with a telescope. Credit: m-gucci via Getty Images)

Can we harness solar energy from other stars?

No one really cares that CrowdScience listener Sam has a younger brother, but they do care about his sister. In fact, they’re fascinated by her. That’s because Sam and his sister are fraternal twins. 

He’s been wondering all his life why he’s treated differently. Could it be cultural? Twins have long appeared in classical mythology, revered literature, and playful comedies—captivating artists and audiences alike across time and continents. Or is there something more scientific behind our fascination? Why are twins special? 

Anand Jagatia investigates with Karen Dillon from Blackburn College in the USA, who says it’s more complicated. Over the years we have created stereotypes of who and what twins are. Our perception has been warped by history and pop culture. As an identical twin herself, she knows firsthand how stereotypes can shape a twin’s identity. 

Philosopher Helena De Bres from Wellesley College in the USA believes these stereotypes play on human anxieties. Their similarities and differences are derived from their biology, maybe our genes have more of an influence over our personalities and behaviours than we like to think? 

And Nancy Segal agrees, Director of the Twin Studies Centre at California State University in the USA. She has spent her career studying twins. She’s found that nearly every trait, whether it be behavioural or physiological, has a genetic component to it. 

Anand is sure to leave you thinking that Sam, his sister and all the other twins across the globe, really are special! 

Presenter: Anand Jagatia 
Producer: Harrison Lewis 
Series Editor: Ben Motley 

(Image: Twin girls (8-10) wearing matching coats and pigtails. Credit: Jade Albert Studio, Inc via Getty Images)

Why are twins special?

Swapping dairy milk for a plant-based milk is a growing trend that promises environmental benefits. But what is the best milk considering both our health and the planet’s? Scottish listener Nancy asks CrowdScience to unpick the pros and cons of plant-based milks. Presenter Graihagh Jackson digs into the research and finds that if the whole world were willing to swap dairy for soy, we would free up a land mass the size of Australia and reduce greenhouse gas emissions dramatically. So in theory the planet would be happier – but would we? Milk is packed with calcium and other nutrients that we humans need in our diet. And the ability to digest the sugar in dairy called ‘lactose’ is, according to evolutionary geneticist Mark Thomas, the most advantageous genetic mutation in human history. So can we live without it?
 
Presenter: Graihagh Jackson
Producer: Louisa Field

(Image: A family enjoying milk at breakfast. Credit: Getty Images)

Which milk is best for me and the planet?

Lyt når som helst, hvor som helst

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