Salt can be found in almost every kitchen in the world. But how did this seemingly simple ingredient become the world's favourite flavour enhancer?

This week, Crowdscience sets out to uncover why these tiny crystals have such a powerful effect on us. We explore the magic behind this tiny mineral that has shaped our tongues, our culture, and our cravings.

Our investigation begins with CrowdScience listener George, who heard from a friend that if he added a few grains of salt to his morning coffee, he could make it taste less bitter. Following some light investigation at his local coffee chain, he began wondering why salt make things taste more delicious.

To try and find an answer, presenter Anand Jagatia heads to a salt mine in Austria with Daniel Bradner, an archaeologist from the Natural History Museum of Vienna. The mine is 200 kilometres from the sea, so where does all the salt come from?

In London, UK, we meet Adriana Cavita, a chef who helps us explore how salt transforms what we eat:  sharpening aromas, softening harsh flavours, and boosting sweetness.

We explore the receptors inside our mouth with taste expert Courtney Wilson from the University of Colorado School of Medicine in the US, to find out how we detect whether there’s too much or too little salt in our food.   

And we meet Joel Geerling, Associate Professor of Neurology at the University of Iowa, US, who’s been looking inside the brain to try and work out why we crave salt. He’s discovered an incredible system that’s highly engineered to give us an appetite for salt. Could it be the answer to George’s question?

Presenter: Anand Jagatia

Producer: Robbie Wojciechowski

Editor: Ben Motley

(Photo: Measuring Teaspoon of Sea Salt with Vibrant Colors - stock photo JannHuizenga via Getty Images)

Is the world sitting on a ticking time bomb? CrowdScience listener Christel recently watched a documentary about a volcanic eruption in 536 AD that left her native Sweden under a cloud of ash for three years. It got her thinking, do we know when this could happen again?

With more than 300 volcanoes – and 24 of them listed as currently active – the Philippines is a country where trying to predict eruptions has huge real world consequences.

Presenter Anand Jagatia travels to Manila to meet the scientists at PHIVOLCS, the Philippine Institute of Volcanology and Seismology, including the head of their Volcano Monitoring and Eruption Prediction Division, Mariton Antonia Bornas, to find out how they try to predict volcanic activity in the country and help make sure communities are evacuated out of harm’s way.

He travels with the team to Taal volcano, which experienced violent eruptions in 2020 and has been active again this year, to visit the observatory monitoring for signs of future activity and to hike to the main crater of the volcano with resident volcanologist Paolo Reniva.

He also speaks to Dr George Cooper from Cardiff University in the UK about what makes a volcano a supervolcano, and to ask the all important question of if we know when this will happen again.

Presenter: Anand Jagatia

Producer: Dan Welsh

Editor: Ben Motley

(Photo: Smoke Emitting From Volcanic Mountain Against Sky - stock photo -EyeEm Mobile GmbH via Getty Images)

Listener Bart in Australia sees invasive species in his area almost every day – rabbits, foxes, and cats. They were transplanted to Australia from Europe more than 100 years ago, but seem to be thriving in their new home.

This got him wondering: how are they going to evolve, now that they are in a new habitat? Can we predict what future evolution will look like based on what we already know?

To find out, Marnie Chesterton visits Sandy Ingelby at the Australian Museum, who manages the mammal collection. She shows Marnie how indigenous Australian animals have evolved to suit where they live.

On the island of Tasmania, Marnie meets the famous Tasmanian Devil and keeper Jono Thomas. Andy Flies from the University of Tasmania explains how the devil is evolving in real-time in response to a health crisis.

So what might the invasive species in Bart’s backyard look like over the next 100 years? We’ll find out, with a little bit of help from palaeontologist Matt McCurry and millions of murderous toads.

Presenter: Marnie Chesterton

Producer: Margaret Sessa-Hawkins

Editor: Ben Motley

(Photo: Wild rabbit- stock photo Credit: John Porter via Getty Images)

CrowdScience listener Po wants to know whether AI could one day replace all human jobs. And while he requests that CrowdScience continues to be hosted by people, it made presenters Caroline Steel and Anand Jagatia wonder – could an AI really present this show?

To find out more about how AI models work and what they’re capable of, Caroline Steel speaks to AI journalist Alex Hern from The Economist. She creates an AI version of herself with Nicky Birch, Innovation Lead for the BBC’s generative AI program, and hears how the BBC is attempting to navigate the ethical use of this new technology.

Anand Jagatia speaks to phonetician Prof James Kirby about how synthetic AI voices have become so convincing, as well as why they still sound slightly unnatural. And Anand and Caroline ponder whether there could ever be a place for AI presenters on the airwaves.

Presenters: Caroline Steel and Anand Jagatia

Producer: Anand Jagatia

Additional production: Lorna Stewart

Editor: Ben Motley

(Photo: Mirror image of presenter Caroline holding microphone Credit: BBC)

CrowdScience listener Doug has been experimenting with holding his wireless garage key to his chin. Why? Because he's testing a strange trick of physics. The range of a key can apparently double when held against your head rather just being held in your hand. Could this really be true, and if so why? Presenter Caroline Steel goes on a wavy journey of self-experimentation with antennas. She follows the story of Doug as he wanders the streets of Calgary in Alberta, Canada testing the key on his head from different distances and even testing it on his dog Maura’s head. To understand the physics behind all this, Caroline meets Dr Lina Mohjazi, Lecturer of Autonomous Systems and Connectivity at the University of Glasgow and Guy Vandenbosch, Professor of Electromagnetic Radiation at KU Leuven University in Leuven, Belgium. Presenter: Caroline Steel Producer: Tom Bonnett Editor: Ben Motley

(Photo: Hand holding a car key remote in front of a red car - stock photo Credit: vadishzainer via Getty Images)

CrowdScience listener Kassy in India wants to know if there’s any science to support the practice of ‘manifesting’ – the idea that you can make your wishes come true just by writing down your goals and sending your dreams out to the universe. Is it just a wacky belief or can it be backed up by research?

Caroline Steel looks at the evidence to see if manifesting works. She talks to researcher Lucas Dixon in Australia, who has found that people who believe in manifesting are more likely to take risky financial decisions or end up bankrupt.

She meets neuroscientist Sabina Brennan in Ireland who argues that psychology has already proven that our thoughts and beliefs shape our reality, through cognitive behavioural therapy for example. So there is evidence to show that some of the techniques in manifesting can work.

Caroline also talks to psychologist Gabriele Oettingen in the US, whose research has demonstrated that just thinking about our wishes actually decreases our energy and makes it less likely that we’ll achieve our goals. She’s come up with her own method for increasing the likelihood of success.

And Caroline tries out a manifesting technique for herself. Can it help her realise her dreams?

Presenter: Caroline Steel Producer: Jo Glanville

Editor: Ben Motley

(Photo: Enthusiastic brunette girl celebrating- stock photo Credit: Mix and Match Studio / 500px via Getty Images)

CrowdScience listener Ndanusa in Ghana, is gazing up at the stars, and wondering. Big philosophical questions, like… what keeps our universe in balance?

From our perspective here on earth, the universe seems like a vast, harmonious system, perpetuating eternally without change. But Ndanusa knows a thing or two about the stars, and he knows that they use up hydrogen as they burn, and release helium. And he’s wondering, is there something out there which does the opposite? Something that uses up helium, and produces hydrogen, to keep the universe in perfect, chemical equilibrium?

His question makes sense! Here on earth for example, animals use up oxygen and produce carbon dioxide, and plants do the opposite. A perfect cycle of production and consumption which (at least in theory), keeps our planet in perfect balance. Could the same kind of system be in place in the wider expanse of the universe?

His intriguing question leads presenter Alex Lathbridge on a journey into the blackness of deep space, the ancient origins of our universe, and the complex physics of the stars. He pops into the Ghana Radio Astronomy Observatory, just outside Accra, where astrophysicist Dr Proven Adzri helps him peer into the earliest few seconds of our universe, and find out what set the stars burning. And at Kwame Nkrumah University of Science and Technology, Dr Linus Labik talks him through what’s going on at the atomic level. And in the deep blackness of the night, up above the tree canopy of Kakum National Park, he takes a peek at the stars for himself. Local guides Chris and Kwabena explain how much meaning there is behind the stars in the night sky.

Presenter: Alex Lathbridge

Producer: Emily Knight

Editor: Ben Motley

(Photo: Large orange and purple exploding orb - stock photo Credit: Soubrette via Getty Images)

Australia’s Great Barrier Reef is one of the richest and most complex natural ecosystems on earth, and it’s home to over 600 species of coral – marine animals that are most closely related to jellyfish.

But the coral is under threat, with climate change, ocean acidification and marine heatwaves endangering the reef and the many iconic animals that depend on it. CrowdScience listener Felix, aged 9, wants to know what we’re doing to protect it, and presenter Caroline Steel is on the case.

In this special edition of CrowdScience, we follow scientists from Australia’s Institute of Marine Science as they attempt to restore the reef with baby corals that they’ve nurtured in experimental tanks at their Sea Simulator facility on the country’s northeast coast.

This experiment kicked off in December, as the researchers recreated the annual mass coral spawning event in controlled conditions, manipulating temperature, pH, light, and nutrients to breed coral baby that they can then use to reseed damaged sections of reef.

After loading up a lorry full of corals and waving it goodbye, Caroline heads north for a rendezvous at dawn, as the corals are loaded onto a boat in Cairns. She travels across the coral sea with marine biologists from AIMS, and is on hand as the corals are introduced to their new home in the ocean.

This is just the beginning - a proof of principle. In future years, the scientists are hoping to reseed heat-tolerant corals, and to scale up and automate this work. But even then, is the scale of the problem too big? Can we restore a reef area the size of Japan, or is it too late?

Presenter: Caroline Steel

Producer: Marnie Chesterton

Editor: Ben Motley

(Photo: Orange-lined triggerfish by coral in beautiful blue water - stock photo. Credit: treetstreet/Getty Images)

On a recent kayaking trip, CrowdScience listener Lanier sliced through his right thumb, putting it out of action for a while. This made life difficult, as he couldn’t button his shirt, tie his shoelaces or type efficiently on his smartphone. Missing the use of his thumb made him wonder: since opposable thumbs are so advantageous to those of us who have them, why didn’t they evolve in more species?

Host Marnie Chesterton unpicks the evolution of our own unique thumbs with the help of paleoanthropologist Tracy Kivell, learning how our grip compares to that of other animals. We discover why mammals like horses and dogs have no use for thumbs, and why we humans don’t have opposable big toes.

Meanwhile, at Taronga Zoo in Sydney, Australia, senior keepers Tarryn Williams Clow and Bec Russell-Cook introduce us to two different marsupials. Humphrey the koala has not one but two thumbs on each hand. Why did koalas develop this anatomical quirk when their closest living relative, the wombat, has spade-like digits? Dr Mark Eldridge from the Australian Museum shares his hypothesis.

And what if we, too, had another thumb? Marnie tries on a robotic Third Thumb, built by designer Dani Clode. Dani has collaborated with neuroscientists from the Plasticity Lab at the University of Cambridge. She tells us what the Third Thumb has revealed about the human brain and how we control our digits.

Presented by Marnie Chesterton

Produced by Cathy Edwards and Margaret Sessa Hawkins for the BBC World Service

(Photo: Kung-Fu Koala - stock photo Credit: Alex BOISSY / Getty Images)

Noise cancelling headphones filter out sound waves that we don’t want to hear. Listener Ahmed in Libya loves wearing his and, as he was listening to them, he had a thought: ‘Could we cancel out light waves in a similar way to how noise cancelling headphones do it?’

He sent his question to CrowdScience and now presenter Alex Lathbridge is getting deep into the physics, to find out if light cancelling devices could replace curtains and shutters.

Alex starts at the Ray Dolby Centre in Cambridge in the UK, built to honour Ray Dolby’s invention of noise cancelling technology. In this amazing building he meets Jeremy Baumberg, Professor of Nanophotonics at Cambridge University. With the help of a tuning fork and a laser beams, Jeremy shows Alex that manipulating light is no easy feat.

Undeterred, Alex tracks down Stefan Rotter, Professor of Theoretical Physics at Vienna Technical University in Austria. Stefan and his colleagues around the world have been pushing forward the development of a device called the ‘anti-laser’. Alex and Stefan explore whether this could be the light-cancelling device of Ahmed’s imagination.

And once we've created a light-cancelling device, what do we do with it? Mary Lou Jepsen is an inventor and the founder of health tech firm Openwater. She tells Alex about how she’s using light wave manipulation to open up new possibilities for medical imaging, and even treatment.

This programme includes clips from: Surrounded by Sound: Ray Dolby and the Art of Noise Reduction https://www.bbc.co.uk/programmes/m002bswq CrowdScience: Can we trap light in a box? https://www.bbc.co.uk/programmes/w3cswvwy

Presenter: Alex Lathbridge

Producer: Tom Bonnett

Editor: Ben Motley

(Photo: Eyesight and vision concept - stock photo Credit: J Studios / Getty Images)

CrowdScience listener Griffith in Ghana, isn’t JUST a CrowdScience listener. He’s also a listener to our sister show on the World Service, Unexpected Elements. But he’s noticed something funny.

In the weekly Unexpected Elements multiple-choice quiz, the answer is almost NEVER ‘a’. It’s nearly always ‘b’, or ‘c’. Why is this? When we set the quiz, why are we so reluctant to choose option ‘a’?

His question leads presenter Alex Lathbridge on a journey into the murky depths of our brain, where he discovers the cognitive biases which so often trip us up in games of chance, or probability. Your brain might be a marvellous machine when it comes to figuring out how to understand the world, but sometimes, in the name of efficiency, it takes clever little short-cuts to the answer.

This pragmatic approach to problem solving helps us manage an incredibly complicated world. But occasionally, especially when it comes to mathematics, chance, and probability, it leads us in the wrong direction. With the help of mathematician Kit Yates from the University of Bath in the UK, and some rather stale sweets, Alex will be finding out how to win at games of chance.

Alex also explores the world of gaming, and gambling. Games of chance in which our intuition sometimes lets us down, and makes us choose unwisely. Rachel Croson, Professor of Economics at the University of Minnesota, USA, talks us through how the human brain can work against us.

But can knowledge of those human pitfalls help us to win? Alex hears from Maria Konnikova, who turned her research on the psychology of poker into a successful gambling career. Can we really use maths to beat our brains, and learn how to win more often?

  Presenter Alex Lathbridge

Producer Emily Knight

Editor Ben Motley

(Photo: Close up image of multiple choice question. Credit: BBC)