Comets, Meteors, and Asteroids

Comets are small bodies that orbit the sun. For at least part of their orbit, they have an atmosphere, a tail, or both. The nucleus of a comet is made up of rock, ice, and gas; the comet's tail and atmosphere are created by the sun's radiation acting on its nucleus.

Because of their unusual shape and sudden appearances, ancient civilizations often interpreted comets as warnings or signs of great news. Aristotle was among those who believed comets were atmospheric phenomena, and he also suggested that comets were signs related to weather, a view that kept fear of comets alive for centuries. As soon as printing was widespread, every appearance of a comet was followed by pamphlets with titles such...