Melvyn Bragg and guests discuss an atomic particle that's become inseparable from modernity. JJ Thomson discovered the electron 125 years ago, so revealing that atoms, supposedly the smallest things, were made of even smaller things. He pictured them inside an atomic ball like a plum pudding, with others later identifying their place outside the nucleus - and it is their location on the outer limit that has helped scientists learn so much about electrons and with electrons. We can use electrons to reveal the secrets of other particles and, while electricity exists whether we understand electrons or not, the applications of electricity and electrons grow as our knowledge grows. Many questions, though, remain unanswered.With Victoria Martin Professor of Collider Physics at the University of EdinburghHarry Cliff Research Fellow in Particle Physics at the University of CambridgeAndFrank Close Professor Emeritus of Theoretical Physics and Fellow Emeritus at Exeter College at the University of OxfordProducer: Simon Tillotson

In this enlightening discussion, Frank Close, an expert on Klaus Fuchs and author of "Trinity," explores the controversial life of Fuchs, a pivotal figure in Cold War espionage. He delves into Fuchs' motivations for sharing nuclear secrets and the moral dilemmas faced by scientists in the Manhattan Project. Close debates whether Fuchs was a betrayer or a peacemaker, unveiling the intricate balance of loyalty and ethics in his dual allegiance. The conversation also touches on the legacy of espionage and its far-reaching consequences on global security.

Researchers have developed a medical imaging technique which reveals where in the body HIV lies hidden, even when people have their infection well controlled by antiviral drugs. The team at the University of California, San Francisco hope this will lead to better treatments and even cures for HIV. As Timothy Henrich told us, they are also going to use the technique to investigate the notion that Long Covid is caused by the coronavirus persisting deep in the body's tissues.Also in the programme, Roland Pease reports from the vast particle accelerator in Switzerland where the famous Higgs particle was discovered ten years ago. The scientists there are preparing to begin experiments with an upgraded Large Hadron Collider to learn more about the particle and the fundamental nature of the Universe. Roland also talks to Frank Close, physicist and author of 'Elusive' - a new biography of Peter Higgs, a scientist as elusive as the particle named after him.Finally an international team of archaeologists have revised the ancient history of the chicken, with a new programme of radiocarbon dating and analysis of buried bird bones. Humanity's relationship with the bird began much more recently than some researchers have suggested. Naomi Sykes of Exeter University and Greger Larson of Oxford University tell Roland when, where and how the domestication began and how the birds spread from Southeast Asia to the rest of the world.Image: VRCPET body scan reveals HIV's hideouts Credit: Timothy Henrich / University of California, San FranciscoPresenter: Roland Pease Producer: Andrew Luck-Baker

Melvyn Bragg and guests discuss the race to build an atom bomb in the USA during World War Two. Before the war, scientists in Germany had discovered the potential of nuclear fission and scientists in Britain soon argued that this could be used to make an atom bomb, against which there could be no defence other than to own one. The fear among the Allies was that, with its head start, Germany might develop the bomb first and, unmatched, use it on its enemies. The USA took up the challenge in a huge engineering project led by General Groves and Robert Oppenheimer and, once the first bomb had been exploded at Los Alamos in July 1945, it appeared inevitable that the next ones would be used against Japan with devastating results.The image above is of Robert Oppenheimer and General Groves examining the remains of one the bases of the steel test tower, at the atomic bomb Trinity Test site, in September 1945.WithBruce Cameron Reed The Charles A. Dana Professor of Physics Emeritus at Alma College, MichiganCynthia Kelly Founder and President of the Atomic Heritage FoundationAndFrank Close Emeritus Professor of Theoretical Physics at the University of Oxford and a Fellow of Exeter College, OxfordProducer: Simon Tillotson

Physicist Frank Close, Astronomer Jocelyn Bell Burnell, and Physicist Ruth Gregory delve into the mysteries of the vacuum of space. They discuss the historical perspectives, the debunking of the ether concept, the bustling activity within seemingly empty space, uncertainty principles in quantum mechanics, the quantum vacuum's energy fluctuations, and the intriguing force of dark energy driving the universe's expansion.