Melvyn Bragg and guests discuss the tantalising idea that there are shortcuts between distant galaxies, somewhere out there in the universe. The idea emerged in the context of Einstein's theories and the challenge has been not so much to prove their unlikely existence as to show why they ought to be impossible. The universe would have to folded back on itself in places, and there would have to be something to make the wormholes and then to keep them open. But is there anywhere in the vast universe like that? Could there be holes that we or more advanced civilisations might travel through, from one galaxy to another and, if not, why not? With Toby Wiseman Professor of Theoretical Physics at Imperial College London Katy Clough Senior Lecturer in Mathematics at Queen Mary, University of London And Andrew Pontzen Professor of Cosmology at Durham University Producer: Simon Tillotson Reading list: Jim Al-Khalili, Black Holes, Wormholes and Time Machines (Taylor & Francis, 1999) Andrew Pontzen, The Universe in a Box: Simulations and the Quest to Code the Cosmos (Riverhead Books, 2023) Claudia de Rham, The Beauty of Falling: A Life in Pursuit of Gravity (Princeton University Press, 2024) Carl Sagan, Contact (Simon and Schuster, 1985) Kip Thorne, Black Holes & Time Warps: Einstein's Outrageous Legacy (W. W. Norton & Company, 1994) Kip Thorne, Science of Interstellar (W. W. Norton & Company, 2014) Matt Visser, Lorentzian Wormholes: From Einstein to Hawking (American Institute of Physics Melville, NY, 1996) In Our Time is a BBC Studios Audio Production