They warn us of approaching storms. They allow us to make emergency phone calls on mobile phones. They're the digital conveyor belt for global commerce. They help police and ambulances reach their destinations when every minute counts. And the Pentagon relies on them to provide U.S. forces with intelligence, communications and targeting information. Satellites, it seems, have become our lifelines. Still, it's easy to take satellites for granted -- easy, that is, until the People's Liberation Army crashes a missile into one of China's aging meteorological satellites, as it did last month. It was a crude show of strength, which...