Curious Cases

Is there a point in space where the Sun could heat a burrito perfectly? asks Will. The doctors tackle this and a plethora of other conundrums from the Curious Cases inbox.Featuring expert answers from: Astrophysicist Samaya Nissanke Cosmologist Andrew Pontzen Cognitive neuroscientist Sophie Scott Presenters: Hannah Fry & Adam RutherfordProducer: Jen WhyntieFirst broadcast on BBC Radio 4 in July 2020.

‘Today I learnt that tigons and ligers are what you get when lions and tigers interbreed?!’ surprised listener Jamz G tells the doctors. ‘What determines whether species can interbreed?’ Geneticist Aoife McLysaght studies molecular evolution. She explains the modern definition of a species, built on ideas from Aristotle, Linnaeus and Darwin: a species is a group of organisms capable of interbreeding to produce fertile offspring. Hybrids – such as ligons and tigers – are usually infertile, because their common ancestors long ago diverged into the lions and tigers we know today. However, this definition isn’t absolute, and there are many ways a new species can be formed.Hybrids also offer rich study subjects for scientists. Mathematical biologist Kit Yates discusses why he’s been reading research papers about hebras and zorses (horse x zebra) as their patterns offer insights into how cells spread and develop into organisms, building on a prediction made by codebreaking mathematician Alan Turing.And it turns out that these hybrids are even more intriguing. As speciation and evolution expert Joana Meier explains, hybrids are not always infertile. Hybridisation can lead to successful new species arising, such as in Lake Victoria’s cichlid fish, who it seems have been having a wild evolutionary party for the last 15,000 years. And the picture gets even murkier when we discover that modern genetics reveals our human ancestors successfully mated with Neanderthals. Presenters: Hannah Fry & Adam RutherfordProducer: Jen WhyntieFirst broadcast on BBC Radio 4 in July 2020.

Everyone knows about the Big Bang being the beginning of the universe and time - but when and how is it going to end? ask brothers Raffie and Xe from Rome. For this series, with lockdown learning in mind, Drs Rutherford and Fry are investigating scientific mysteries for students of all ages. The doctors sift science from philosophy to find out.Cosmologist Jo Dunkley studies the origins and evolution of the universe. She explains how astrophysical ideas and techniques have evolved to tell us what we now know about our galaxy and far beyond, from the elegant parallax technique to standard candles. This particular distance measure, which uses stars of a known brightness to work out how far away other objects in the universe are, was discovered by American astronomer Henrietta Swan Leavitt in 1912, who worked at the Harvard University as one of several “computers” – women who processed and calculated data and made significant contributions to astronomy.Curious Cases’ universal guru Andrew Pontzen puts this into context. Because the universe is so enormous, it turns out that these measurements are just the first steps on the cosmic distance ladder – a suite of tools that astrophysicists use to determine distances to celestial objects. Scientists know that objects are moving away from us because the wavelengths of light from them get stretched and appear redder in our telescopes – the so-called red shift effect. But having a handle on the distances to and between those objects allows cosmologists to monitor what’s happening to them over time. And it turns out that not only are they getting further apart, indicating that the universe is expanding, but that this process is accelerating. So what might happen in the end? Expansion and then collapse – a big crunch? Expansion into the void – a big freeze, or a big rip? Or what if there is more than one universe – might a new one bubble up with totally different laws of physics that would cause our own to cease existing? It turns out that when dealing with predictions for something involving infinite space and time, the possibilities are largely limited by human imagination alone. Ideas are where science starts, but experiments are required to build evidence confirming or rejecting them as fact. The doctors discuss how gravitational wave detectors and quantum computers might one day provide this.Presenters: Hannah Fry & Adam Rutherford Producer: Jen WhyntieFirst broadcast on BBC Radio 4 in June 2020.

"What’s the point of wasps?" asks listener Andrew, who is fed up with being pestered. For this series, with lockdown learning in mind, Drs Rutherford and Fry are investigating scientific mysteries for students of all ages. Do wasps do anything to justify their presence as a picnic menace?Ecologist Seirian Sumner researches social wasp behaviour and champions their existence. Not only do yellow jacket wasps perform important ecological services as generalist pest controllers of aphids, caterpillars and flies in the UK, they have complex societies and may even perform pollination services, making them more like their better-loved bee cousins than many might think.However, much remains unknown about wasps’ contribution to our ecosystem. Seirian works with entomologist Adam Hart, and together they run The Big Wasp Survey each summer, a citizen science project dedicated to find out more about UK wasp species and their populations. Prof. Hart sets up an experimental picnic with Dr Rutherford to try and attract some native wasps, and discusses why they are so maligned. But in some parts of the world UK wasp species have become a major problem. Just after World War II, having unwittingly chosen some aircraft parts destined for New Zealand as their overwintering home, some wasp queens woke up in the city of Hamilton. With no natural predators or competitors, they quickly established a growing population. Fast forward to today, and by late summer the biomass of wasps becomes greater than all the birds, rodents and stoats in the southern island’s honeydew beech forests. Multiyear nests have been discovered that are over three metres tall and contain millions of wasps. Researcher Bob Brown is digging into wasp nests back in the UK to discover which species keep wasps in check here, and whether they might work as biological control.This causes the doctors to ponder the problems of humans moving species around the planet. Accidental or even well-meaning introductions all too often become invasive. As climate change and urbanisation accelerate, wasps may become more helpful in some ways and more harmful in others.Presenters: Hannah Fry, Adam Rutherford Producer: Jen WhyntieFirst broadcast on BBC Radio 4 in 2020.

Liz Bentley, Chief Executive of the Royal Meteorological society, explains the science of weather prediction. Mark Miodownik discusses the technique of cloud seeding for inducing rainfall, but highlights its unreliable results. The podcast explores the challenges of verifying the effectiveness of cloud seeding and delves into the political implications of manipulating the weather. Additionally, it examines desertification and advancements in desalination technology. Nature versus nurture is also contemplated.

"Why do our tummies rumble - and when they do, does it always mean we are hungry?" asks listener James, aged 12. For this series, with lockdown learning in mind, Drs Rutherford and Fry are investigating scientific mysteries for students of all ages. To get to the bottom of this noisy problem, the doctors tune in to our guts.Geneticist Giles Yeo studies food intake and obesity. He explains the wavy workings of our digestive system, and how those audible rumbles are a sign that digestion is taking place – a phenomenon thought to be onomatopoeically named 'borborygmi' by the ancient Greeks, and explored further in the gruesome 19th century experiments of surgeon William Beaumont. However, tuning in to the gut’s sounds can tell us more than whether we need a snack. Family doctor Margaret McCartney takes us through the process of how and why she and her medical colleagues may use a stethoscope to listen to your abdomen for both particular noises and silence. Microbiologist Barry Marshall has taken medical listening one step further in his Noisy Guts Project. Inspired by microphones used to listen for termites hiding in walls, the Nobel Prize-winning scientist is trialling an acoustic belt, which could be worn to help diagnose and treat Irritable Bowel Syndrome.Presenters: Hannah Fry, Adam Rutherford Producer: Jen WhyntieFirst broadcast on BBC Radio 4 in 2020.

"What are wormholes and do they really exist?" asks Manlee-Fidel Spence, aged 12. In this exotic episode, the doctors investigate how wormholes would work. Cosmologist Andrew Pontzen explains why wormholes could allow you to travel through time as well as space. And physicist Jim AlKhalili outlines the infinite problems this could generate.When it comes to wormholes and time travel, many science fiction stories have married solid science and successful storytelling, as Jennifer Oullette describes, but others really have defied the laws of physics. Jim also reveals why some quantum physicists now think that wormholes could be everywhere. But don't expect to jump back to 1955 any time soon.Presenters: Hannah Fry, Adam Rutherford Producer: Michelle MartinFirst broadcast on BBC Radio 4 in 2020.

Two cold callers feature in this episode. Jennifer Langston from Ontario in Canada sent this message to curiouscases@bbc.co.uk:"My husband has just taken up cold water swimming and he'll swim in temperatures as low as 6 degrees Celsius. I worry that it's too cold for him, but he claims that 'swimming in cold water is good for you', which drives me bonkers. Can you tell us if there is any scientific proof behind this?”Adam takes a trip to his local lido and asks the locals why they get a kick out of a chilly winter dip. Meanwhile, Hannah calls the Antarctic to talk to meteorologist Richard Warren about the perils of a frozen beard.Our second cold caller, Sarah Dudley, asks why women get cold feet in bed. Thermal physiologist Heather Massey is on hand with the answer.But when it comes to the natural world, other animals are masters of sub-zero living. Frozen Planet producer Kathryn Jeffs, from the BBC's Natural History Unit, explains why polar bears are perfectly designed for the Arctic. And we discover why Paddington Bear is better suited to Peru.Presenters: Hannah Fry, Adam Rutherford Producer: Michelle MartinFirst broadcast on BBC Radio 4 in 2020.

“I suppose a cold is called a cold because we catch it in the winter," writes Alison Evans from St Albans. "But why is it that we get more colds in winter than in the summer?”This week's Cold Case is all about the common cold, a set of symptoms caused by hundreds of different strains of cold and flu viruses. Adam uncovers the stinky history of infectious disease with medical historian Claire Jones.Virologists Jonathan Ball and Wendy Barclay describe how spiky viruses lock on to our cells, but why many of the symptoms of a common cold are due to our own body's overreaction. Plus, we delve into the science of sneezing with nose doctor Carl Philpott.Presenters: Adam Rutherford, Hannah Fry Producer: Michelle Martin

"My question is about something I became aware of at a young age," explains Samantha Richter from Cambridgeshire."I was sitting on the carpet at school, being read a story by the teacher. My hair felt as though it was standing on end as waves of a tingly sensation washed over my head. I subsequently found certain scenes in films had this effect, when actors were talking softly, or someone was having their hair brushed.""Then, a few years ago, I discovered that there is a name for the tingles, it's called ASMR. My question is, what is ASMR, and why do we experience it?"In this episode, we explore the world of Autonomous Sensory Meridian Response. It's a trend which has risen quickly on YouTube, with devoted subscribers following their favourite 'ASMRtists' whose videos receive millions of plays.Hannah speaks to Dr Nick Davis, who published the very first research paper on the phenomenon in 2015. And Adam is put to the test by Dr Giulia Poerio, to see if he is susceptible to the sensation of ASMR. Are there any proven benefits for devoted fans, or is it just a YouTube fad?We've concocted our very own Curious recordings so you can find out if your brain begins to tingle. You'll find them in our normal podstream, where you can enjoy Adam and Hannah crafting a very ASMRy cocktail for your listening pleasure.Presenters: Hannah Fry, Adam Rutherford Producer: Michelle MartinFirst broadcast on BBC Radio 4 in 2020.