Carlos Frenk, Eugenia Cheng, Jim Al-Khalili and Louisa Preston debate time and space with presenter Rana Mitter and an audience at Radio 3's Free Thinking Festival at Sage Gateshead.

We can measure time passing but what actually is it? What do scientists mean when they suggest that time is an illusion. Can time exist in a black hole? Is everyone’s experience of time subjective? What is the connection between time and space? How does maths help us understand the universe?

Professor Carlos Frenk is founding Director of the Institute for Computational Cosmology at Durham University and the winner of the Gold Medal of the Royal Astronomical Society in 2014.

Dr Eugenia Cheng is Scientist in Residence at the School of the Art Institute of Chicago and an Honorary Fellow of the University of Sheffield. She is trilingual, a concert-level classical pianist and the author of Beyond Infinity: An Expedition To The Outer Limits Of The Mathematical Universe.

Jim Al-Khalili is Professor of Physics at the University of Surrey and presenter of BBC Radio 4’s The Life Scientific and TV documentaries. His books include Paradox: the Nine Greatest Enigmas in Science, Black Holes, Wormholes and Time Machines and Quantum: a Guide for the Perplexed.

Dr Louisa Preston is a UK Space Agency Aurora Research Fellow. An astrobiologist, planetary geologist and author, she is based at Birkbeck, University of London. Her first book is Goldilocks and the Water Bears: the Search for Life in the Universe.

Producer: Torquil MacLeod