On Friday the 13th (yes, really) of April 2029, Earth will avoid an apocalyptic event by an astronomical hair’s breadth as the asteroid Apophis, streaks by. It will come closer to Earth than the Moon — much closer in fact. It will come between us and the satellites that bring us radio, television and military intelligence. Apophis is named after an Egyptian god of chaos and evil. If it were to hit Earth, chaos would be the least of our trouble. It’s 1,000 feet across, the size of a football stadium, and it’s going 69,000 miles an hour. Apophis won’t...