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If the Moon’s orbit around Earth were aligned just a little differently, human history might have played out a little differently, too. That’s because eclipses of the Sun and Moon have played pivotal roles in some historical events.
Lunar eclipses occur when the Moon passes through Earth’s shadow, while solar eclipses occur when the Moon crosses in front of the Sun, blocking it from view.
But the Moon’s orbit is tilted with respect to Earth’s orbit around the Sun. So most months, the Moon, Sun, and Earth don’t line up properly to cause an eclipse. The geometry is right only a few times per year, so any given location on Earth sees a total lunar eclipse every year or so, and a total solar eclipse every few decades.
Because eclipses are rare, they were hard to predict — and that made them scary. In 413 BC, for example, the army of Athens suffered a major defeat when it delayed retreating after a lunar eclipse. And two millennia later, Christopher Columbus and his men avoided starvation when Columbus accurately predicted another eclipse, causing hostile natives in the New World to bring them food.
If the Moon’s orbit were perfectly aligned with the Sun, though, then eclipses would be so common that they would have attracted far less concern — perhaps changing the course of history.
An eclipse will darken the Moon tomorrow night. A nearby star and planet will help make it an unforgettable experience — which we’ll talk about tomorrow.
Script by Damond Benningfield, Copyright 2014