If you’re in the southern half of the United States, you can look for something a bit unusual in the early evening sky over the next few weeks: the Big Dipper rising. Like all the stars in the northern sky, those of the Big Dipper constantly wheel around the North Star, Polaris, as Earth spins on its axis. The stars of the Dipper are closer to the North Star than most, though, so they make a tight loop around it. From the northern U.S. — cities like Seattle and Minneapolis — Polaris is so high in the sky that the Dipper never sets. It scoots low above the northern horizon, but never quite dips below it. As you head south, though, the North Star drops lower and lower in the sky — and so does the Dipper. From the latitude of Denver, the star at the tip of the Dipper’s handle disappears. And by the time you get as far south as Dallas, almost the entire Dipper scoops below the horizon. Even so, it doesn’t remain out of sight for long. From Dallas, for example, most of the Dipper is below t
