In 2134 B.C., two Chinese court astrologers took some unscheduled time off in order to get loaded. As a result, they failed to predict the solar eclipse of Oct. 22 that year—and the emperor had them beheaded.
Today, thankfully, the prediction of solar eclipses is an exact science and far less fraught with risk of decapitation. It’s a sure thing that on Aug. 21, the moon’s shadow will darken the skies over a wide swath of North America, with the band of totality sweeping from Oregon to South Carolina. It’s the first total solar eclipse viewable from the continental U.S. since 1979, and the first viewable coast to coast since 1918.
You won’t lose your head, but it’s important to take some simple precautions to protect your eyes during an eclipse—you should never look at the sun with naked eyes, even when it’s occluded by the moon. The video above, from the California Academy of Sciences, provides historical context, the background science, and tips for safe viewing of this summer’s grand celestial event.
The academy is also looking for citizen scientists to help with a program documenting how animals respond to the eclipse.
The Aug. 21 eclipse is actually just one of a series of 77 solar eclipses occurring every 18 years and 11 days, known as the Saros Series 145. It began with the eclipse on Jan. 4, 1639. And while this summer’s eclipse will only darken the skies for two minutes and 40 seconds, some of the later eclipses in the series will more than double that. Eclipse No. 48 in the series, for instance, will carve a shadowy path across the southeastern United States and treat skygazers to a full six minutes and 59 seconds of daytime darkness. Make sure you reserve a prime viewing spot for June 2, 2486 now.