At one time or another, almost everyone has glimpsed a swift little streak of light dashing across the night sky. These sudden celestial visitors are meteors, commonly called falling or shooting stars. Meteors are pieces of space debris that plow into the Earth's atmosphere. Because they arrive at very high speeds — anywhere from 11 to 74 kilometers (7 to 46 miles) per second — they vaporize by air friction in a white-hot streak. Most meteor parents (meteoroids) range in size from sand grains to pebbles. Occasionally, a larger object will survive its descent and fall to Earth — then it's called a meteorite.

A meteor that appears brighter than any of the stars and planets is called a fireball. The sudden appearance and fast motion of a bright meteor produces an illusion of closeness that can fool even well-trained professionals. Airline pilots have swerved to avoid meteors that were actually 160 kilometers (100 miles) away.

Most meteors are seen 80 to 120 kilometers (50 to 75 miles) above the ground. Occasionally, someone will claim to see a fireball land just beyond a tree or a hilltop, but in fact a typical fireball first appears at a height of about 125 kilometers (80 miles) and loses its brightness while still at least 20 kilometers (12 miles) above the ground.

Much more abundant are smaller, everyday meteors. While most look white, some appear blue, green, yellow, orange, or red. One that explodes at the end of its visible flight is called a bolide.