<P> A meteor, known colloquially as a shooting star or falling star, is the visible passage of a glowing meteoroid, micrometeoroid, comet or asteroid through Earth's atmosphere, after being heated to incandescence by collisions with air molecules in the upper atmosphere, creating a streak of light via its rapid motion and sometimes also by shedding glowing material in its wake . Although a meteor may seem to be a few thousand feet from the Earth, meteors typically occur in the mesosphere at altitudes from 76 to 100 km (45 to 60 mi). The root word meteor comes from the Greek meteōros, meaning "high in the air". </P> <P> Millions of meteors occur in Earth's atmosphere daily . Most meteoroids that cause meteors are about the size of a grain of sand, i.e. they are usually millimeter - sized or smaller . Meteoroid sizes can be calculated from their mass and density which, in turn, can be estimated from the observed meteor trajectory in the upper atmosphere . Meteors may occur in showers, which arise when Earth passes through a stream of debris left by a comet, or as "random" or "sporadic" meteors, not associated with a specific stream of space debris . A number of specific meteors have been observed, largely by members of the public and largely by accident, but with enough detail that orbits of the meteoroids producing the meteors have been calculated . All of the orbits passed through the asteroid belt . The atmospheric velocities of meteors result from the movement of Earth around the Sun at about 30 km / s (18 miles / second), the orbital speeds of meteoroids, and the gravity well of Earth . </P> <P> Meteors become visible between about 75 to 120 km (45 to 75 mi) above Earth . They usually disintegrate at altitudes of 50 to 95 km (30 to 60 mi). Meteors have roughly a fifty percent chance of a daylight (or near daylight) collision with Earth . Most meteors are, however, observed at night, when darkness allows fainter objects to be recognized . For bodies with a size scale larger than 10 cm to several meters meteor visibility is due to the atmospheric ram pressure (not friction) that heats the meteoroid so that it glows and creates a shining trail of gases and melted meteoroid particles . The gases include vaporised meteoroid material and atmospheric gases that heat up when the meteoroid passes through the atmosphere . Most meteors glow for about a second . </P> <P> Although meteors have been known since ancient times, they were not known to be an astronomical phenomenon until early in the nineteenth century . Prior to that, they were seen in the West as an atmospheric phenomenon, like lightning, and were not connected with strange stories of rocks falling from the sky . In 1807, Yale University chemistry professor Benjamin Silliman investigated a meteorite that fell in Weston, Connecticut . Silliman believed the meteor had a cosmic origin, but meteors did not attract much attention from astronomers until the spectacular meteor storm of November 1833 . People all across the eastern United States saw thousands of meteors, radiating from a single point in the sky . Astute observers noticed that the radiant, as the point is now called, moved with the stars, staying in the constellation Leo . </P>

How far away can you see a meteor