Discovery

The smaller the thing you look at, the bigger the microscope you need to use. That’s why the circular Large Hadron Collider at CERN, where they discovered the Higgs boson is 27 kilometres long, and its detectors tens of metres across. But to dig deeper still into the secrets of the Universe, they’re already talking about another machine 4 times bigger, to be built by the middle of the century. Roland Pease asks if it’s worth it.Image: CMS Beampipe removal LS2 2019 (Credit: Maximilien Brice/CERN)

Episode 2: Lost in the DarkPhysics is getting a good understanding of atoms, but embarrassingly they’re only a minor part of the Universe. Far more of it is made of something heavy and dark, so-called dark matter. The scientists who discovered the Higgs boson ten years ago thought they’d also create dark matter in the underground atom smasher at CERN. But they haven’t seen it yet. Roland Pease joins them as they redouble their efforts at the upgraded Large Hadron Collider, and travels to Boulby Underground Laboratory inside Britain's deepest mine, where subterranean telescopes hope to see dark matter streaming through the Galaxy.Image: CMS Beampipe removal LS2 2019 (Credit: Maximilien Brice/CERN)

The machine that discovered the Higgs Boson 10 years ago is about to restart after a massive upgrade, to dig deeper into the heart of matter and the nature of the Universe.Roland Pease returns to CERN’s 27-kilometre Large Hadron Collider (LHC) dug deeper under the Swiss-French border to meet the scientists wondering why the Universe is the way it is. He hears why the Nobel-prize winning discovery of the “Higgs Particle” remains a cornerstone of the current understanding of the nature of matter; why the search for “dark matter” – 25% of the cosmos - is proving to be so hard; and CERN’s plans for an atom smasher 4 times as big to be running by the middle of the century.Image: CMS Beampipe removal LS2 2019 (Credit: Maximilien Brice/CERN)

Ant-loving professor, Adam Hart, shares his passion for leaf cutting ants with Jim Al Khalili. Why do they put leaves in piles for other ants to pick up?Talking at the Hay Festival, Adam describes the experiments he designed to test the intelligence of the hive mind. When does a waggle dance become a tremble dance? And how do the honey bees know when this moment should be?We like the phrase ‘as busy as a bee’. In fact, bees spend a lot of time doing nothing at all, a sensible strategy from the point of view of natural selection.And where does Adam stand on insect burgers?Producer: Anna Buckley

When a person with severe anorexia nervosa refuses food, the very treatment they need to survive, is that refusal carefully considered and rational, as it can appear to those around them? Or is it really the illness that’s causing them to say ‘no’?This is one of the thorny ethical dilemmas that Jacinta Tan has wrestled with over the course of her career. She is deeply curious about the mind, and has spent hundreds of hours sitting with people with anorexia nervosa, not persuading them to eat, rather listening to them talk about what’s going on in their minds and how the illness influences their decisions.These rich internal worlds, that she has revealed, shape her work as a Child and Adolescent Psychiatrist at Oxford Health NHS Foundation Trust, where she treats people with eating disorders. The views of those with the condition and their families have been central to the recent government reviews of the Eating Disorder Services that she led in Scotland and Wales.These conditions can be hugely challenging to treat. Jacinta Tan tells Jim al-Khalili how it's the art of medicine, as much as the science, that helps people recover.Producer: Beth Eastwood

Pete Smith is very down to earth. Not least because he’s interested in soil and the vital role it plays in helping us to feed the world, mitigate climate change and maintain a rich diversity of species on planet earth. He was born in a pub and failed the 11+ exam (designed to identify bright children just like him) but he became a distinguished professor nonetheless. Tackling climate change in isolation is a mistake, he says. We need to consider all the challenges facing humanity and identify strategies that deliver benefits on all fronts: food security, bio-diversity and human development goals. He tells Jim Al-Khalili about his life and work and the urgent need for our degraded peat bogs to be restored. Peat bogs that have been drained (for grazing or to plant trees) add to our carbon emissions. Healthy peat bogs, however, are carbon sinks. Producer: Anna Buckley

The world is full of colour! But, listener Maya Crocombe wonders ‘how do we see colour and why are some people colour blind?’Dr Rutherford and professor Fry set out to understand how special light-sensitive cells in our eyes start the process of colour perception, why people sometimes have very different experiences of colour and whether, in the end, colour is really just ‘in our heads’.Dr Gabriele Jordan from Newcastle University explains why lots of men struggle to discriminate between certain colours and why there were lots of complaints from colour-blind viewers when Wales played Ireland at rugby.Professor Anya Hurlbert, also from Newcastle University, tackles the most divisive of internet images: The Dress! Did you see it as blue-black or yellow-gold? Anya explains why people see it so differently, and why our ability to compensate for available light is so useful.To see the Dunstanborough Castle illusion as described in the episode, check out the Gallery on this page and also on the Discovery homepage.

Mathematician Hannah Fry and geneticist Adam Rutherford investigate your everyday science queries. Today, they get stuck into two questions about tides. Lynn Godson wants to know why isn’t high tide at the same time at all points around the coast? Whilst Tim Mosedale asks, could we ever harness tidal power commercially? Did you think tides are caused by the pull of the Moon? And that they come in and out twice a day? Well, yes, that’s true but it turns out there’s so much more to it than that, especially here in the UK, which has the second largest tidal range in the world at the Severn Estuary near Bristol, coming in at an average of 15 metres (50ft in old money). But why should high and low tide times be so different even in places that are relatively close to each other?The answer partly lies in something called bathymetry (which has more to do with baths than you might think – well basins at any rate). As for harnessing sea power, there are some ambitious projects currently in development and predictions that wave and tidal could make up as much as 15 percent of the UK’s energy needs in future. But how realistic is this and how do you ensure that your power generators can survive the rigours of the ocean – storms, saltwater and all those pesky barnacles?To help answer these queries, Hannah and Adam are joined by Physicist and Oceanographer, Helen Czerski and Professor Deborah Greaves OBE, who heads up the COAST lab at the University of Plymouth which studies marine renewable energy technologies.

Today The Evidence goes green as Claudia Hammond and her panel of experts discuss plant power, how nature and the natural environment affect our mental health.Produced in collaboration with Wellcome Collection and recorded in front of a live audience in the Reading Room at Wellcome Collection in London, the programme addresses that widely-held view, even intuition, that plants and nature directly impact on our emotional wellbeing. As always, Claudia and her panel of experts are interested in the evidence behind such beliefs, and as they reveal, proving this link scientifically, is fiendishly difficult. The evidence base is growing (especially studies which show being in nature improves your mood) and there is much emerging research which gives tantalising glimpses into exactly which elements in nature could help to produce that green feel-good factor (and which elements can actually make us feel worse).On stage, a 25 year old semi-professional footballer shares how he first put his hands in the soil after the Grenfell Tower fire in North Kensington in London five years ago, when 72 people lost their lives and left his community traumatised. Tayshan tells Claudia that nature saved him, and many others, as they planted seeds, re-claimed spaces and built new gardens in the aftermath of the tragedy. All children and young people, he says, should have access to the healing power of nature and he calls on the horticultural establishment to open its doors much wider to enable this to happen.Beth Collier too, believes that nature should be a meaningful part of everyday life for all. The connection with nature, she says, is fundamental to healing mental distress. A psychotherapist and ethnographer, Beth founded Wild in the City to encourage those who live in urban environments, especially people of colour, to re-connect with nature. Claudia’s other guests are Kathy Willis, former Director of Science at the Royal Botanic Gardens, Kew, now Professor of Biodiversity at the University of Oxford and author of a soon-to-be-published book called Prescribing Nature and Birgitta Gatersleben, Professor of Environmental Psychology at the University of Surrey and a leading researcher studying the relationship between the natural environment and human wellbeing.Produced by: Fiona Hill and Maria Simons Studio Engineers: Duncan Hannant and Emma Harth (Photo: Footpath through a forest Credit: Nik Taylor/UCG/Universal Images Group/Getty Images)

Why does human hair go grey and is it ever possible for it to go white overnight from shock? Hannah and Adam explore why hair goes grey, how much stressful life events and a lack of sleep can speed up the process. They hear from the pilot whose hair turned white after a flight where all 4 of his engines failed after flying through a volcanic ash cloud - was the shock responsible? They also uncover new research which has shown it's possible for greying hair to return to its natural colour and ask if this finding could be exploited to uncover a cosmetic way to reverse hair greying?