Crowdscience solves a range of listeners’ cosmic mysteries, from the reason we only ever see one side of the moon, to why planets spin, and discover the answer can be found in the formation of the solar system. We talk to astronomer Dr Carolin Crawford to understand how stars are made, and investigate the art of astronomy with journalist Jo Marchant, hearing how the ancient Greeks came up with a zodiac long before the invention of a telescope, revealing an intimate relationship between humans and the night sky.

Presenter: Marnie Chesterton

Producer: Marijke Peters

[Image: The Solar System. Credit: Getty Images]

Why am I embarrassed to be naked? Chumbuzzo in Zambia wonders. And what would happen if we ditched our clothes and embraced nudity? Presenter Anand Jagatia and Producer Caroline Steel spend the day naked with other naturists to see if they can shift their embarrassment.

Maybe there are good evolutionary reasons to cover up or perhaps we are contributing to inequality and negative body image by hiding our real selves? Marnie Chesterton explores different cultural attitudes to nudity and finds out about the science behind embarrassment. Clothes optional.

Presented by Marnie Chesterton. Produced by Caroline Steel for the BBC World Service

Many of us willingly subject ourselves to pain and irritation by eating chilli. CrowdScience listener Tina wonders what’s driving this apparent masochism: why does ‘feeling the burn’ make so many of us feel so good?

It’s just one of several tasty questions we tuck into in this episode. Also on the menu is stew: why does it taste better the next day? Listener Helen’s local delicacy is Welsh cawl, a meat and vegetable concoction. Tradition dictates it should be eaten the day after it’s made, but is there any science behind this?

And we finish the meal with cheese. Listener Leander asks what makes some cheeses blue, some hard and crumbly, and some run all over your fridge. How is milk transformed into such radically different end products?

Presented by Marnie Chesterton and Alex Lathbridge

Produced by Cathy Edwards, Marnie Chesterton and Alex Lathbridge for the BBC World Service.

[Photo:Woman eating red Chilli Pepper. Credit: Getty Images]

What does science say about controlling urination, and other bodily functions? We tackle three queries about peeing triggers, pooing positions and missing sweat. This episode CrowdScience presenter Marnie Chesterton poses some of the best listener follow-up questions that have landed in our inbox to a panel of experts.

Listener Samuel in Ghana is wondering why watery sounds seem to induce urination. Producer Melanie Brown heads out to survey whether this is the case for individuals in an actual crowd at a public fountain in London. And urologist and trustee of the International Continence Society Marcus Drake talks Marnie through how he uses the sound of running water during his work as a hospital doctor helping patients with common but distressing peeing issues, and the limitations of research into this question.

And he’s not the only listener who wants us to dig deeper into topics we’ve explored on the show before. Anna in Tokyo also got in touch after hearing our show about toilets, to ask if there is a toilet design that is most ‘natural’ for our health. Gastroenterologist Anton Emmanuel explains why small changes in people’s posture whilst pooing can have a significant impact on their quality of life.

Finally, listeners Stelle, James and Joel emailed [email protected] after hearing Marnie investigate hyperhidrosis: Sweating too much. They and their relatives experience the opposite:

If you’re one of the millions of people who used lockdown to try something new like baking sourdough bread, you may well be wondering what’s happening chemically inside your loaf, especially if the end result keeps changing. Well, you’re not alone. Listeners Soheil and Sean are both keen bakers but want to know more about the thing that makes bread rise: yeast. What is yeast? Where does it come from and can you catch it? And how hard is it to ‘make’ yourself? Soon after lockdown took effect, commercial supplies of the stuff disappeared from supermarket shelves across the globe.

The shortage also affected brewers the world over. A big fan of yeast in most of its forms, Marnie Chesterton took on the challenge of creating her own. She talks to the brewers who hunt rare strains to create the perfect beer, and hears from the biologist who says these amazing microbes, used for thousands of years, could be used to make food production more sustainable. And she discovers how this simple ingredient could be instrumental in the fight against climate change.

Presented by Marnie Chesterton and Produced by Marijke Peters for the BBC World Service.

Squelching into the science of slime, Chhavi Sachdev seeks to find out why it took so long for listener Helen Tyson to remove slime from her fingers, after she picked up a tiny slug while gardening.

This unfortunate and hugely repulsive experience set Helen to wonder what it is about the structure of slug slime that makes it gloopy, so she sent Chhavi to meet with slug slime expert Professor Andrew Smith who reveals how the complex molecular structure of this pervasive fluid makes it so difficult to scrub off.

Slime is used by all sorts of creatures including the Giant African Land snail, which invaded India by hitching a ride on imported timber. But invasive species biologist Dr TV Sajeev reveals that these snails are themselves giving a lift to another meningitis-causing parasite that can infect people. Chhavi looks for these massive molluscs in her own garden in Mumbai.

Marine biologist Helen Scales describes how animals can use slime for catching food, mating, defence, or even transportation, and Chhavi speaks with Dr Adam Celiz who has been inspired by this slimy adaptability to create a tool that can provide new cells to replace damaged heart cells after a cardiac arrest.

Slugs, snails and even fish keep a variety of useful chemicals in their slime. Some make them taste bitter, and others numb the mouth of predators, but they may also prevent the animals from contracting infections. Dr Sarah Pitt has investigated these compounds in the slimy mucus of a garden snail and discovered an antibiotic that is brand new to science.

Slime is pretty disgusting, but it’s also completely fascinating.

Presented by Chhavi Sachdev

Produced by Rory Galloway

(Photo: Slugs Mating. Credit: Getty Images)

Anyone else had their flight cancelled? The COVID 19 pandemic has had a huge impact on air travel – air traffic in 2020 is expected to be down 50 per cent on last year. But beyond the obvious disruption to business and people’s lives, how might the quieter skies affect our weather and climate?

One curious listener, Jeroen Wijnands, who lives next to Schiphol airport in the Netherlands, noticed how there were fewer clouds and barely any rainfall since the flights dropped off. Could airplanes affect our local weather?

Also, did we learn anything from another occasion when airplanes were grounded, during the post-9/11 shutdown? How will the current period impact our future climate?

Marnie Chesterton investigates this question and discovers some of the surprising effects that grounded aircraft are having: on cloud formation, forecasting and climate change.

Presenter: Marnie Chesterton, Producer: Dom Byrne

[Photo:Commercial airplane parking at the airport. Credit: Getty Images]

Listener Avalon from Australia wants to know why people use conspiracy theories to explain shocking events. Are we more likely to believe conspiracy theories in times of adversity? What purpose do conspiracy theories serve in society?

Marnie Chesterton speaks to the scientists to explain their popularity, even in the face of seemingly irrefutable evidence.

Presented by Marnie Chesterton. Produced by Caroline Steel for the BBC World Service.

Image: All-seeing eye of God inside triangle pyramid. Credit: paseven, Getty Images

These days we’re more acquainted with soap than ever before, as we lather up to help stop the spread of coronavirus. And for CrowdScience listener Sharon, this set off a steady stream of soapy questions: how does soap actually work? How was it discovered in the first place, long before anyone knew anything about germs? Are different things used for washing around the world, and are some soaps better than others?

We set up a CrowdScience home laboratory to explore the soap making process with advice from science-based beauty blogger Dr Michelle Wong, and find out what it is about soap’s chemistry that gives it its germ-fighting superpowers. Soap has been around for at least 4000 years; we compare ancient soap making to modern methods, and hear about some of the soap alternatives used around the world, like the soap berries of India.

And as for the question of whether some soaps are better than others? We discover why antibacterial soaps aren’t necessarily a good idea, and why putting a toy inside a bar of soap might be more important than tweaking its ingredients.

Presented by Marnie Chesterton.

Produced by Cathy Edwards for the BBC World Service.

Image: Child with thoroughly washed hands. Credit: Getty Images.

Think of the oceans and an empty and peaceful expanse relatively untouched by humankind might come to mind. But is this peace an illusion? CrowdScience listener Dani wants to know if the noise of shipping and other human activity on the oceans is impacting on sea life.

To find out, Marnie Chesterton takes a deep dive to learn how marine animals have evolved to use sound; from navigating their environments to finding a mate or hiding from prey. She then speaks to a scientist who is using acoustic observatories to track the many ways human activity - like sonar and shipping - can interfere.

Marnie virtually visits a German lab which tests the ears of beached whales, dolphins and seals from around the world to try and ascertain whether they suffered hearing damage, and what might have caused it. What other smaller creatures are negatively impacted by underwater noise? Marnie learns that acoustic trauma is more widespread than first thought.

As human life continues to expand along ocean waters, what is being done to reduce the impact of sound? Marnie meets some of the designers at the forefront of naval architecture to see how ship design, from propellers to air bubbles and even wind powered vessels can contribute to reducing the racket in the oceans.

Presented by Marnie Chesterton.

Produced by Melanie Brown for the BBC World Service.

Main Image: The front of a humpback whale underneath the sea in Shetland Islands, Scotland, December 2016. Credit: Richard Shucksmith / Barcroft Im / Barcroft Media via Getty Images