The book discusses many of today's challenges, including the biggest threat to the planet (an "asteroid collision", like the one that wiped out the dinosaurs 66 million years ago ... "we have no defense" against that), climate change ("a rise in ocean temperature would melt the ice caps and cause the release of large amounts of carbon dioxide ... [making] our climate like that of Venus with a temperature of 250 Coulomb "), the threat of nuclear war ("at some point in the next 1,000 years, nuclear war or environmental calamity will 'cripple Earth'"), nuclear power ("that would give us clean energy with no pollution or global warming"), the development of artificial intelligence (AI) ("in the future AI could develop a will of its own, a will that is in conflict with ours") and humans ("a genetically-modified race of superhumans, say with greater memory and disease resistance, would imperil the others").