During the Cold War, Tucson was ringed by hardened underground silos holding Titan 2 missiles, all armed with nuclear warheads. The 18 silos were operated from 1963 to the early 1980s by the 390th ...

These chunky rocks and ice balls are the remnants of the formation of the universe. Here’s what you need to know about them—and whether they are a serious risk. Comet Neowise streaks through the night ...