It was a dark and stormy night. A secret message arrived addressed to Rutherford & Fry from a mysterious woman called Heidi Daugh, who demanded to know: "Why do people like to be scared? For example, going on scary amusement park rides and watching horror movies that make you jump.” What followed was an investigation, which would test our intrepid duo to their very limits. They explore the history of horror, starting with its literary origins in the Gothic fiction classic 'The Castle of Otranto'. Adam challenges Hannah to watch a horror film without hiding behind a cushion. She quizzes horror scholar Mathias Clasen to find out why some people love the feeling of terror, whilst it leaves other cold. Sociologist Margee Kerr and psychologist Claudia Hammond are also on hand to explore why scary movies are so powerful and popular. Then Rutherford and Fry investigate the more physical side of fear, when they delve into the history of roller coasters to investigate why we enjoy being scared. Never ones to shy away from a challenge, the pair attempt to channel their inner adrenaline junkies with a trip on one the UK's scariest roller coasters at Thorpe Park. David Poeppel from New York University studies the science of screaming, and we discover what makes screams uniquely terrifying. Plus, psychologist and broadcaster Claudia Hammond describes some early experiments which tested how fear affects our body. This episode is a remake of two earlier broadcast episodes. If you have any Curious Cases for the team to investigate please email [email protected] Producers: Fiona Roberts & Michelle Martin Presenter: Adam Rutherford & Hannah Fry

Why are some people left-handed, whereas the majority are right handed? Rutherford and Fry revisit The Sinister Hand episodes to further investigate handedness in humans and animals. They considered cockatoos, chimpanzees and Hannah's dog, Molly, to discover that humans are unique, with just one in ten of us being left-handed. They ask if there is an evolutionary reason for just 10% of the human population being southpaws Hannah talks to primatologist Prof Linda Marchant from Miami University about Neanderthal teeth and termite fishing. Adam consults handedness expert Prof Chris McManus from University College London. He's been trying to track down the genes responsible for whether we're right or left handed. And what about left-handed brains or eyes or molecules? Prof Andrea Sella explains handedness, or chirality, at the molecular scale and why when we consider Thalidomide, something seemingly so trivial can be extremely important. They also explore the left-handed brain. Some researchers point to a link between left-handedness and impairments like autism or dyslexia. Others claim that lefties are more creative and artistic. So what's the truth? The team consults Professors Sophie Scott, Chris McManus and Dorothy Bishop to find out. This episode is an updated version of two earlier broadcast episodes. If you have any Curious Cases for the team to investigate please email [email protected] Producers: Fiona Roberts & Michelle Martin Presenter: Adam Rutherford & Hannah Fry A BBC Audio Science Unit production for BBC Radio 4

The doctors continue their investigation into gravity, and answer Peter Fraser’s question: is dark matter a proper theory or just a fudge to fit existing 'proper' theories to otherwise inexplicable observations? Whilst scientists are pretty convinced our understanding of gravity is largely correct, there are still some significant gaps. Namely, given the way galaxies are observed to behave, around 85% of the matter that they think should be in our universe is missing. So where – and, as importantly, what – is it? Cosmologist Andrew Pontzen introduces the evidence from our observations of the cosmic microwave background, light leftover from the Big Bang, which indicate that dark matter exists. However, this evidence alone is not enough for science. Physicist Chamkaur Ghag is trying to find particles of dark matter here on Earth. Unsurprisingly, no-one is quite sure where these critters are hiding in the particle zoo of protons, neutrons, electrons, quarks, bosons, muons and the rest – or even what they look like. One theory suggests a weakly interacting massive particle, or WIMP, may be the dark matter minibeast. Hundreds of thousands of these could be flying through our fingertips every second. To tell whether they’re there, Cham and hundreds of scientists are building detectors, huge vats of liquid xenon in underground caverns. Bond villain-esque lairs don’t come cheap, and listener Peter’s query is valid – what if dark matter goes the same way as the aether, an all-permeating (and ultimately non-existent) material that was hypothesised to carry light through the vacuum of space? Astrophysicist Katy Clough reiterates that experiments are the way to test predictions. Building a picture of how gravity works continues to take many people enormous effort, but this is the scientific process. Presenters: Hannah Fry & Adam Rutherford Producer: Jen Whyntie A BBC Audio Science Unit production for BBC Radio 4

The doctors investigate a millennia-old query, as listener Emma in New Zealand asks, ‘How does gravity pull us?’. People have been thinking about how gravity works for a very long time. Way longer than when that particular apple almost certainly didn’t fall on the head of Isaac Newton. Cosmologist Andrew Pontzen begins guiding us through our journey by taking us back to the almost entirely incorrect writings of ancient Greeks. We then fast forward past Galileo and Newton, and throw in an extra dimension. Using an all-too-believable analogy where some merry cyclists suddenly ride into a meteor crater, astrophysicist Katy Clough tells us how Einstein’s spacetime works. Limitations of analogies accepted, this explains some of the observations that didn’t fit with Newton’s workings alone. But there are other snags with our understanding of gravity, both at the very small quantum scale and the very large galactic scale. Physicist Chamkaur Ghag introduces what scientists think may account for some of these issues: The mysterious dark matter. Presenters: Hannah Fry & Adam Rutherford Producer: Jen Whyntie A BBC Audio Science Unit production for BBC Radio 4

Psychologist and presenter of All in the Mind, Claudia Hammond wrote the book ‘Time Warped – Unlocking the Mysteries of Time Perception’. She explains how emotion and memory are big factors in how time is perceived. She stresses how time can stretch and squeeze depending on whether you are looking backwards or forwards. And she explains how lockdown has warped time in different ways for different people. Professor David Eagleman, from Baylor College of Medicine in Houston, conducted a very famous experiment on time dilation, to see whether time slows down when you are very frightened. He wanted to see whether people actually have increased time resolution during a terrifying moment, and tested whether his students actually see in slow motion when they leapt off a tall building (in a safe manner). Professor Marc Whitman is a neurologist who has spent his career looking for the clock in our brains. He says that time is dealt with in many parts of the brain, with some parts dealing with different durations, from milliseconds to decades. Katya Rubia is Professor of Cognitive Neuroscience at Kings College London and is an expert on time perception in children with ADHD. She links the impulsiveness of children with Attention Deficit Hyperactivity Disorder to problems with time perception and has found that the pre frontal lobe, which is key for perceiving time is both functionally and structurally different in children with the disorder, which means that time goes much slower for them. This goes some way to explain their impatience and inability to sit still. Produced by - Fiona Roberts Presented by – Hannah Fry and Adam Rutherford A BBC Audio Science Unit Production