If you miss this morning’s eclipse, there’s always another one. It might not be a solar eclipse, and it might not be visible from your location. But every year, four or five eclipses are visible from somewhere on Earth.

The next one comes up in two weeks — a partial lunar eclipse. It’ll be visible from a good bit of the world, but not much of the United States. The next great eclipse will roll around on April 8th — a total solar eclipse that will track across the U.S.

Eclipses occur thanks to the relative motions of Earth, Sun, and Moon. When the geometry is right, the Moon passes directly between Earth and the Sun, creating a solar eclipse. And when the Moon is on the opposite side of our planet, it can pass through the shadow of Earth, creating a lunar eclipse.

But total solar eclipses are doomed. Right now, the Moon and Sun appear almost exactly the same size in our sky. But when the Moon is a little farther from Earth than average, it’s not big enough to black out the Sun. That leaves a ring of sunlight around the Moon — an annular eclipse like today’s.

But the Moon is moving away from Earth at about an inch and a half per year. Over the next half a billion years or so, that will add up. The Moon will move so far that it will never be big enough to cover the Sun. Total solar eclipses will disappear — replaced by ever-brighter annular eclipses as the Moon recedes into the distance.
 

Script by Damond Benningfield

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