The Perseid meteor shower is building toward its peak. Tonight, you might see a few of its streaks of light, although the Moon will drown out all but the brightest of them. But even the ones you do see through the moonlight can’t compare to a meteor that blazed across the sky 50 years ago. It was visible during broad daylight. The fireball was first seen over Utah, during the afternoon of May 10th, 1972. Thousands watched it race across the sky. It vanished from sight over Alberta, Canada. Two people made home movies of it. And a spy satellite designed to look for nuclear test firings on Earth followed it for about two minutes. The fireball was a small asteroid — a ball of rock and metal anywhere from 10 to 45 feet in diameter — that was being vaporized by friction with the atmosphere. It dropped to an altitude of just 35 miles. But it hit the atmosphere at a shallow angle, so it skipped back into space like a rock skipping across a pond. If the asteroid had taken dead aim at Earth, it
