As the planet faces unprecedented human-caused global heating, heads of government are meeting in Turkey for the next fortnight for the latest round of climate talks. Madeleine Finlay tells co-host Ian Sample why these negotiations are so critical and what the chances are of meaningful change.

As the nights draw in, many of us can experience low mood. But for a small proportion of people a more intense depression develops through the winter months. It’s a phenomenon that since the 1980s has been labelled seasonal affective disorder, or Sad, and can be debilitating for sufferers. To find out more about the latest scientific understanding of Sad, Ian Sample speaks to Russell Foster, professor of circadian neuroscience at the University of Oxford. He explains what scientists think the mechanism for the condition could be and what the evidence says about the best way to tackle it.

In the UK and Ireland, Samaritans can be contacted on freephone 116 123. In the US, you can call or text the 988 Suicide & Crisis Lifeline at 988 or chat at 988lifeline.org. In Australia, the crisis support service Lifeline is 13 11 14. Other international helplines can be found at befrienders.org

Social media is awash with claims iron deficiency can be identified in the mirror by dark circles, breaking hair and dry skin. But is ‘ferritin face’ real? Madeleine Finlay tells Ian Sample why so many of us struggle to keep our iron levels up, how we can actually diagnose low iron and the best way to correct a deficiency, with help from Hal Drakesmith, a professor of iron biology at Oxford University, and advice from Dr Sue Pavord, a consultant haematologist at Oxford university hospitals and associate senior lecturer in clinical medicine at St Edmund Hall.

When the water in Flint, Michigan, became contaminated with dangerous levels of lead, Dr Siddhartha Roy, then a third year PhD student, was part of the team of scientists who publicly contradicted state and federal claims that it was safe. He became a local hero until a new piece of research challenged the idea that children in Flint had been left permanently brain damaged by the crisis. His adherence to the evidence, no matter who it offended, has earned him the 2026 Maddox prize, which recognises individuals who stand up for science and evidence, despite challenges or hostility. He tells Ian Sample how he reflects on his experience in Flint, and why he lost friends as a result of his work there

As one of the world’s leading forensic anthropologists, Dame Sue Black has acted as an expert witness in a myriad of high-profile criminal cases. Her work has taken her from the lab to active war zones and the aftermath of natural disasters to identify victims’ bodies. Speaking to Ian Sample, the professor explains why standing up in front of a judge and jury has been one of the more terrifying parts of her career, the reputational risk of presenting evidence in court and what the future of forensic science could look like

You Can See Everything, a documentary about the disgraced biotech company founder Elizabeth Holmes, has enjoyed a record-breaking opening in the US. It is a testament to how fascinated we remain by the convicted fraudster, but what is behind the enduring appeal? US technology editor Blake Montgomery tells Madeleine Finlay why Holmes continues to fascinate us, and reflects on whether the Theranos scandal has had a permanent impact on Silicon Valley

Clip: You Can See Everything, A24

‘You can’t make this stuff up’: why we remain fascinated by Elizabeth Holmes

Workers have always been monitored by their bosses, first through output targets, and then via computer software labelled ‘bossware’. But AI is transforming the capabilities of these systems, processing huge volumes of data to provide minute-by-minute accounts of activity, and productivity. To find out more, Ian Sample hears from UK technology editor Robert Booth. He explains which sectors are adopting this approach, why they are doing it, and how it could end up being counterproductive.

As diet trends proliferate on social media, it can be hard to work out which are backed by science and which should be ignored. From paleo to keto, raw food to intermittent fasting, each attracts a tribe of ardent followers. Now Daniel Lieberman, professor of biological sciences at Harvard University, has written a book to try to cut through the noise. In Fed Up, he uses his background as an evolutionary anthropologist to scrutinise the evidence, turning himself into a guinea pig in the process and trying various diets. In this podcast, he tells Ian Sample which one has remained part of his routine

As diet trends proliferate on social media, it can be hard to work out which are backed by science and which should be ignored. From paleo to keto, raw food to intermittent fasting, each attracts a tribe of ardent followers. Now Daniel Lieberman, professor of biological sciences at Harvard University, has written a book to try to cut through the noise. In Fed Up, he uses his background as an evolutionary anthropologist to scrutinise the evidence, turning himself into a guinea pig in the process and trying various diets. In this podcast, he tells Ian Sample which one has remained part of his routine

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For decades physicists have been puzzling over the enigma of dark matter. We think it makes up 85% of the matter in the universe, but the mysterious substance cannot be seen or detected, and we know about it mainly through observations of the gravitational effects it has on other things. But now scientists believe they may be a step closer to detecting it. Science editor Ian Sample explains to Madeleine Finlay why, if confirmed, the finding could completely transform our understanding of the universe. And Dr Samuel Erikson, senior research associate at the University of Bristol, and first author of the research paper, explains how the finding has been received in the physics community

In this age of crisis, technology is pulling us apart. At its best, journalism can bring us together again.

Written and read by the Guardian editor-in-chief Katharine Viner