5 Things You Probably Didn't Know About Solar Eclipses

(Image: NASA's Scientific Visualization Studio)

1. Earth is the only planet in our solar system from which you can witness a perfect total solar eclipse. A curious coincidence makes it possible: The sun is 400 times the diameter of our moon, but it's also 400 times farther away from us—so both bodies appear to be the same size in the sky, and the moon perfectly covers the sun.  If the moon were closer, it would block out both the sun and its corona; farther away and it would not cover the sun completely. No other planet has the right-sized moon.

2. To produce a total eclipse, the sun, moon, and Earth need to line up in a straight line. Astronomers call this “syzygy.”

3. During an eclipse the moon’s shadow races faster than the speed of sound across the Earth— more than 1,200 miles per hour.

4. Solar and lunar eclipses happen in pairs (sometimes even trios!). The total solar eclipse on August 21 will be preceded by a partial lunar eclipse on August 7.

5. If you stood in one place and waited to see a total solar eclipse, you could wait for 300 years or more. The last total solar eclipse visible from the continental U.S. was in 1979; the next won't be until 2024.

Join us from anywhere in the world to see this amazing phenomenon live stream online and via our mobile app. The Exploratorium's webcast team is traveling to Oregon and Wyoming to bring you this upcoming astronomical event.