In a four-part series, our podcast “Babbage” pulls back the curtain on the vast scientific infrastructure that America has created to build, maintain and upgrade its nuclear weapons. From the turn of the 20th century, a scientific-mystery story about the ingredients of matter led to a world-changing (and second-world-war-ending) bomb. Nuclear weapons have been central to geopolitical power ever since. Now America is seeking to modernise its stockpile and, in doing so, its scientists are pushing the frontiers of extreme physics, materials science and computing.