Book excerpt: We live in a world positively teeming with threats and apocalyptic scenarios. Many of them are familiar: terrorism, deadly viruses, global warming and war, but many others most of us can't even imagine: self-replicating nanobots that can devour an entire planet, high-energy experiments that threaten to suck the Earth into a mini black hole, and even super-sophisticated scientific contraptions that can put an end to the entire universe.