Things do fall from the heavens. Unfortunately, in the writer’s experience, not a lot of pennies. Instead, we get meteors that streak briefly across the sky, meteorites that survive the downward journey through the atmosphere, and, just occasionally, something bigger. An asteroid. Not that all of the objects in the main belt of asteroids are big—many are, like the meteors that vanish in a flash when they meet air for the first time, just grains of dust. Ceres, the biggest, is a round object, a dwarf planet. We don’t have to worry about Ceres; it travels in its own stable orbit and it’s not coming this way. Others present a hazard, or a potential danger, and collisions happen. The last big collision we know of happened more than a hundred years ago in the vast forests of Siberia, where there are few people. The next one? Scientists are watching a few of the rogue objects out there, to assess the likelihood of a crash. Unfortunately, precision regarding location of any big event is hard to achieve, not least because the spin of the Earth makes timing critical. Just a few minutes can make the different between a big splash in the ocean or destruction of a city.