The year’s celestial highlight now starts its parade through the predawn sky. It’s Hale-Bopp, visible to the naked eye low in the northeast. More than any other denizens of the cosmos, comets cause astronomers to gobble down antacid tablets. With just a few observations, we can know precisely where a comet will be and how fast it’ll move. But the appearances of the comet, unlike those of Neptune or the vice president, are unpredictable. This lends comets intrigue and charm. It also drives the experts bonkers.