What is termed a "falling star" is actually a meteor. Meteors are caused by little bits of space debris the size of large sand grains or small pebbles, called meteoroids. Countless numbers of them orbit the Sun like tiny planets. When one strikes the Earth's upper atmosphere -- at speeds of many kilometers per second -- air friction vaporizes it in a white-hot streak. The word meteor refers to this streak of light. Very rarely does a piece of a meteoroid survive to fall all the way to the ground. Then it's called a meteorite. On a clear, dark night far from city light pollution, you can see several meteors per hour on average. But at certain times of year the numbers increase. When the Earth passes through a stream of meteoroids traveling together through space, we get a meteor shower.

Most meteor showers repeat on about the same date year after year -- every time the Earth goes through the same place in its orbit. Other showers are less predictable, producing fine displays in some years and practically nothing in others. There are two famous meteor showers that typically produce frequent sightings over several nights. The LEONID meteor shower occurs in November, and the Perseid meteor shower in August.