That's always a hard story to explain right, because how does one go about retelling the hardships of billions of people counter imposed against the thought that the only way to save humanity was to cull the herd? Does she start introducing the scientist both responsible for the death of the world, and the existence of the few survivors who'd managed to make it this far? Clarke's just going to take it in stride that she doesn't have to explain nuclear bombs to a man literally made out of metal and circuitry, but that's been a sticking point for a lot of people on board thus far.

"The first time, an A.I. got hold of the launch code for every nuclear weapon on Earth, and fired them simultaneously."