Comets have fascinated people for millennia, but until 1994 no one had ever had the chance to witness firsthand the destructive power of this enigmatic celestial wanderer. The string of explosions was awesome, yet the discovery that comets can wreak havoc would not have come as a surprise to our distant ancestors.

People of widely different cultures have long regarded comets with fear and dread. The unheralded, unpredictable appearances of these ephemeral celestial visitors were believed to be omens of disaster for rulers, realms, and entire populations. Comets were thought to be a premonition of a great catastrophe such as a plague, war, famine or floods. Halley's Comet made an appearance in 1066, in which King Harold II was crushed by William the Conqueror and was attributed to the comet’s appearance.

Not every comet shows all these features. Some never reveal a nucleus, but only a coma, while others display just a starlike nucleus. In the latter case they resemble asteroids, the miniplanets that orbit the Sun mainly between the paths of Mars and Jupiter. Many faint comets never develop a tail but come and go merely as ghostly comas.

Comets in the past have been described in such terms as 'brilliant,' 'awesome,' 'spectacular,' or 'splendid,' so it might seem puzzling that most people alive today have never seen one. But even so-called great comets are usually not all that bright. The tail of a typical comet has roughly the same surface brightness as the Milky Way—or even a lower brightness—and the head is not much brighter. Even a first-quarter or last-quarter Moon will wash out much of the show. In addition, most people nowadays live in or near cities and towns where electric lights illuminate the night sky and smog dims the view.