"Like the red star that from his flaming hair shakes down disease, pestilence and war."

That's Homer's description of a comet, and it reflects the view shared by our ancestors, that what appeared to be flaming stars were harbingers of doom. I'm Jim Metzner, and this is the Pulse of the Planet. Well today we know that comets are balls of ice and debris, and they are still viewed on earth with awe and some uncertainty. Edwin Krupp is the director of the Griffith Observatory in Los Angeles.

Comets appear out of nowhere, they look different than anything else. You know when they're bright, you see them streaming this tail behind it. You watch the comet move across the background stars, unlike the orderly motion of the moon or the sun, or the planets. So very early on, people regarded comets as a sign, or in fact, the actual agent of trouble. As time has gone on, and our knowledge of the physical universe has evolved, we've gotten a better physical understanding of comets. But it hasn't necessarily changed the way people talk about them. I mean, we have the majority of the population today perfectly happy to see comet Hale Bopp and yet there are segments of the population that still say, "That comet was a signal of the troubles of our time." Well, they've been omens of disaster for thousands of years, for some folks they're gonna be omens of disaster for the future. People who are paying attention however will get much better pleasure from comets. First, they're gorgeous, unexpected - a delightful surprise. Second, rather than being omens of the future, they are in fact messages of the past. These are primordial pieces or our solar system. These comets as we study them now, tell us how this whole local neighborhood came into being. They're one of the most valuable things we can look at.

Pulse of the Planet is made possible in part by Virginia Tech, inventing the future through a hands-on approach to education and research.