Perseid Meteors 
One of the year's best meteor showers is building up to its peak tomorrow night. And the Moon will be out of the way, so it won't interfere with the late-night fireworks.
The Perseid meteor shower is spawned by Comet Swift-Tuttle. As it orbits the Sun, this big "dirty snowball" sheds tiny grains of rock and dust. Over time, the particles spread out along the comet's orbital path. Earth flies through this path every August, sweeping up some of the dust grains. They plunge into our atmosphere at more than a hundred thousand miles an hour. They vaporize as the streaks of light known as meteors.
Most of the meteors are faint -- you need to get away from city lights to see them. But a few can be bright enough to see from just about anywhere. They leave glowing trails that are visible for several seconds.
The Perseids will be at their best late tomorrow night, although a few outliers can be visible for a few days before and after the peak. At their peak, you might see a few dozen meteors per hour. And the Moon sets by mid-evening, so it'll leave dark skies for the shower.
The meteors all appear to "rain" into the sky from the direction of the constellation Perseus -- hence the name "Perseids." But the meteors can streak across any part of the sky, so you don't have to look toward Perseus to see them. Just find a dark but safe viewing location, and then watch the sky for the fireworks.
More about the Perseids tomorrow.
Script by Damond Benningfield, Copyright 2010