Can you slow down time by hurtling through space at breakneck speed? Could listener Saskia’s friend - currently one year older - end up the same age as her if he went fast enough? It sounds bananas, but it’s all part of Einstein’s mind-warping theory of relativity.

With expert copilots Professor Sean Carroll and Dr. Katie Clough, Hannah Fry and Dara Ó Briain embark on a cosmic roller coaster through space and time. They uncover why GPS satellites - whizzing around Earth at 14,000 km/h - need to account for time bending, why penthouse dwellers age faster than those on the ground floor, and, most importantly, why clowns on trains might just hold the key to understanding modern physics.

Contributors:

Katy Clough - Research Fellow at Queen Mary University of London Sean Carroll - Professor of Natural Philosophy at Johns Hopkins University Peter Buist - Manager of the Galileo Reference Centre Richard Dyer - PhD student at the University of Cambridge

Producer: Ilan Goodman Executive Producer: Alexandra Feachem A BBC Studios Audio Production