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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 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?

Cycling is good for our health, good for the planet, and it can be an efficient way of moving around busy cities. But despite all the rational arguments for it, in most cities the number of people who get on their bikes is low.

CrowdScience listener Hans wants to know whether it’s time to change our tactics. Could we persuade more people to cycle if we moved away from focusing on well-intentioned rational arguments and use messages that appeal to our desires and vanity instead? What does the science say? Presenter Caroline Steel is on the case. 

She meets Winnie Sambu from World Bicycle Relief to learn about why people in countries like Kenya to choose the bike to get around. She heads out on a ride with psychologist Professor Ian Walker from the University of Swansea to find out what barriers there might be to persuading people to cycle. 

She also takes a lesson from one of the world’s top cycling nations as she talks to Marie Kåstrup, a cycling campaigns expert who has advised the Danish government on inspiring cycling and sustaining it in the city of Copenhagen. Also in Denmark, Caroline meets behavioural scientist Dr Pelle Guldborg Hansen who shares his experience in the art of persuasion. 

Presenter: Caroline Steel 
Producer: Tom Bonnett 
Series Producer: Ben Motley

How can we persuade more people to cycle?

Was there ever a time when life on earth was peaceful? Free of violence? No predators, no prey, just... vibes? Or has nature always been 'Red in Tooth and Claw'? 

Have we always been eating each other? 

Our listener Scott sent us on a quest to discover the origins of predators and prey, and to find out what all this ‘eat or be eaten’ stuff is really about. 

Taking us back to the very dawn of life on earth, Professor Susannah Porter from the University of Santa Barbara lets Alex peer into an extraordinary world of microscopic warfare. It’s a dog-eat-dog (or, microbe-dissolve-microbe) world, with single celled organisms doing battle with each other. For billions of years, this was life on earth! Tiny, violent, and completely fascinating. 

But what about bigger creatures? More complex ones - animals? Speeding forward several billion years, Alex arrives in the Ediacaran Period – a time of unusual tranquility, where strange, plant-like animals lived in relative peace. At the Natural History Museum in Oxford, UK, palaeontologist Dr Frankie Dunn shows him around. 

So where did real predators come from, then? Alex is joined by Dr Imran Rahman as he ushers in one of the most extraordinary periods in Earth’s history – the magnificently named Cambrian Explosion! Here we find real predators, with teeth, claws, and impressive hunting appendages. Through the fossil record, we can see an arms race developing – as predators get more sophisticated, so does their prey. It’s ON. 

Finally, Alex wonders if our own evolution, shaped as it has been by this predator-prey arms race, might have been very different without the threat of being chomped. Professor Lynne Isbell from the University of California, Davis takes Alex on a trip into our primate past, and tackles one of our most fearsome predators: snakes. 

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

Was there an idyllic time before carnivores?

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

What is the point of menstruation?

Lyt når som helst, hvor som helst

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