Curious Cases

"What makes things sharp? Why are thinner knives sharper? What happens on the molecular level when you cut something?" All these questions came from Joshua Schwartz in New York City.The ability to create sharp tools allowed us to fashion clothing, make shelters and hunt for food, all essential for the development of human civilisation, according to materials scientist Mark Miodownik.We hear from IBM scientist Chris Lutz, who has used one of the sharpest blades in the world to slice up individual atoms.Plus palaeoarchaeologist Becky Wragg Sykes reveals the sharpest natural object in the world, a volcanic glass used by the Aztecs called obsidian.Presenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin.

"What is the tiniest dinosaur?" asks younger listener Ellie Cook, aged 11. Today's hunt takes us from the discovery of dinosaurs right up to the present day, which is being hailed as a 'golden age' for palaeontology. One new species of dinosaur is currently being unearthed on average every single week. But what's the smallest dino? And what can size reveal about the life of extinct animals?Hannah goes underground at the Natural History Museum to look through their vaults in search of the tiniest dinosaur with palaeontologist Susie Maidment.Meanwhile Adam chats to dinosaur expert Steve Brusatte from Edinburgh University about why size really does matter, especially when it comes to fossils.Presenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin.

The second instalment in our double bill on the science of sex, answering this question from Robert Turner, a Curio from Leeds: "Why do we only have two sexes?"Drs Rutherford and Fry look for anomalies in the animal kingdom that go beyond the traditional mechanics of human reproduction. Biologist and author Carin Bondar describes some of the wild and somewhat disturbing ways other animals like to do it. Take the hermaphrodite sea slug who races to stab its penis into its partner's brain during sex, or the female redback spider who loves to indulge in a spot of post-coital cannibalism.But the greatest number of different sexes is found in the world of fungi. Some species can have hundreds of distinct mating types. Fungal ecologist Lynne Boddy explains how mushrooms have sex and why on earth they need so many polygamous partners.Presenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin.

"Why do we only have two sexes and are there any anomalies in the animal kingdom?" asks Robert Turner from Leeds. From reptilian virgin births to hermaphrodite sea slugs, over the next two episodes Drs Rutherford and Fry examine the weird ways other creatures reproduce.In this first instalment, they tackle what's been called 'the hardest problem in evolutionary biology' - why does sex exist? Why aren't we all one single sex that clone ourselves to produce offspring? It makes perfect evolutionary sense - you could pass on all of your genes and don't need to bother finding a partner.Hannah visits London Zoo to meet a fierce komodo dragon named Ganas, the result of a virgin birth. And Adam meets some tiny bdelloid rotifers, microscopic worm-like females who have survived for 50 million years by cloning themselves.You can send your questions in to curiouscases@bbc.co.ukPresenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin.

"The other day I was watching the James Bond film Goldfinger. He boasts a laser powerful enough to project a spot on the Moon. Is this possible? If so, just how powerful would such a laser need to be?" This curious question was sent to curiouscases@bbc.co.uk by Eddie Griffith from Hinckley in Leicestershire.Adam visits one of the most powerful lasers in the world, the Gemini Super Intense Laser at the aptly named Rutherford Appleton Laboratory in Didcot, Oxfordshire. Plasma physicist Ceri Brenner gives him a quick zap, whilst explaining what would happen if they attempted to shoot their quadrillion watt laser at the Moon.Hannah talks to Tom Murphy from the University of California San Diego, who fires lasers at the Moon for a living. However, unlike Goldfinger, he's not using his Moon Laser for crime, he's using it for science.Presenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin.

"Are machines better than humans at identifying faces?" asks the excellently named Carl Vandal.Today's Face Off leads our intrepid detectives to investigate why we see Jesus on toast, Hitler in houses and Kate Middleton on a jelly bean.Face perception psychologist Rob Jenkins from the University of York explains why we're so good at spotting familiar faces, like celebrities. Plus, Franziska Knolle from the University of Cambridge discusses her face recognition study involving Barack Obama and a group of highly-trained sheep.But are we outwitted by artificial intelligence when it comes to face ID? BBC technology correspondent Rory Cellan-Jones gives us the low-down on the pros and cons of current technology.Presenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin.

"We often read that the fastest thing in the Universe is the speed of light. Why do we have this limitation and can anything possibly be faster?" Ali Alshareef from Qatif in Saudia Arabia emailed curiouscases@bbc.co.uk with this puzzling problem.The team grapples with Einstein's Special Theory of Relativity, with help from cosmologist Andrew Pontzen and a British train, travelling somewhat slower than the speed of light.Plus physicist and presenter Jim Al-Khalili describes how he nearly lost his boxer shorts in a daring bet concerning the speed of subatomic particles.Send your questions for consideration to: curiouscases@bbc.co.ukPresenters: Adam Rutherford, Hannah Fry Producer: Michelle Martin.

"Why don't children like vegetables?" asks Penny Young from Croydon, and every parent ever.This week Rutherford and Fry dig into the science of taste and discover that there may be more to this question than meets the eye. Children and adults have a different taste experience when they eat the same foods. When you're young, foods can taste saltier and more bitter. What's more, as Jackie Blisset, Professor of Childhood Eating Behaviour explains, there are even evolutionary reasons why toddlers avoid vegetables.For most children it's a phase, but a minority of adults are also labelled as fussy eaters. According to food psychologist Linda Bartoshuk, they are probably what's known as 'supertasters'. Supertasters live in a neon taste world where vegetables are more bitter, and chillies are unbearably hot.Adam sets out on a quest to find potential supertasters in the Radio 4 offices. First stop, the Today programme where Nick Robinson and Sarah Montague become his experimental guinea pigs, with surprising results.Send your questions for consideration to: curiouscases@bbc.co.ukPresenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin.

"Why don't thousands of bats in a cave get confused? How do they differentiate their own location echoes from those of other bats?" This puzzling problem was sent in to curiouscases@bbc.co.uk by Tim Beard from Hamburg in Germany.Since ecolocation was first discovered, this question has perplexed biologists. Hannah turns bat detective to try and track down these elusive creatures at The Queen Elizabeth Olympic Park in East London. This is where zoologist Kate Jones from University College London is using a network of smart sensors to find, identify and track wild bats.John Ratcliffe from Toronto University chats bats and sonar with Adam to try and locate the answer. It's an unlikely tale involving gruesome early experiments, cunning electric fish and some surprising bat maths.Send your Curious Cases for consideration to: curiouscases@bbc.co.ukPresenters: Adam Rutherford, Hannah Fry Producer: Michelle Martin.

"Why do we dream and why do we repeat dreams?" asks Mila O'Dea, aged 9, from Panama.Hannah and Adam delve into the science of sleep. From a pioneering experiment on rapid eye movement sleep, to a brand new 'dream signature' found in the brain, they discover how scientists are investigating our hidden dreamworld.Featuring sociologist Bill Domhoff from the University of California Santa Cruz, sleep psychologist Mark Blagrove from the University of Swansea, and neurologist Francesca Siclari from the University of Lausanne.Presenters: Adam Rutherford, Hannah Fry Producer: Michelle Martin.