Today we're talking about two 20th century titans, the physicists J. Robert Oppenheimer and Albert Einstein. Their scientific achievements changed the world, and yet they were sceptical of one another. In the 1930s, Oppenheimer had described Einstein as 'completely cuckoo' - later in his life, Einstein would say that he admired Oppenheimer as a man, but not as a physicist. So why did Einstein feel so uneasy about Oppenheimer's discoveries? And who left the most profound legacy? Dan is joined by Cindy Kelly, founder and President of the Atomic Heritage Foundation, to find out. Produced by James Hickmann and edited by Dougal Patmore. Enjoy unlimited access to award-winning original documentaries that are released weekly and AD-FREE podcasts. Get a subscription for £1 per month for 3 months with code DANSNOW sign up at https://historyhit/subscription/ We'd love to hear from you- what do you want to hear an episode on? You can email the podcast at [email protected]. You can take part in our listener survey here.