How big are most meteoroids? How fast do they travel?
The majority of visible meteors are caused by particles ranging in size from about that of a small pebble down to a grain of sand, and generally weigh less than 1-2 grams. Those of asteroid origin can be composed of dense stony or metallic material (the minority) while those of cometary origin (the majority) have low densities and are composed of a “fluffy” conglomerate of material, frequently called a “dustball.” The brilliant flash of light from a meteor is not caused so much by the meteoroid’s mass, but by its high level of kinetic energy as it collides with the atmosphere. Meteors enter the atmosphere at speeds ranging from 11 km/sec (25,000 mph), to 72 km/sec (160,000 mph!). When the meteoroid collides with air molecules, its high level of kinetic energy rapidly ionizes and excites a long, thin column of atmospheric atoms along the meteoroid’s path, creating a flash of light visible from the ground below. This column, or meteor trail, is usually less than 1 meter in diameter, but
