The U.S. says Russia is building a nuclear weapon for space. But how would you prove there’s a warhead inside a satellite 1,200 miles up?

Nuclear explosions in space, conducted by the United States in the 1960s, produced brilliant auroras and knocked out power on Earth. If a similar experiment were carried out in orbit today, we would lose navigation, communications, and weather forecasting for a long time. Space is now densely populated with satellites that would not survive the electromagnetic pulse and particle streams from a nuclear explosion. But U.S. officials are concerned that the Russian military is considering such a ...