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