On December 14, 2020, a camera onboard a satellite recorded something that looked like a brown blob streaking across South America. The video was so unexpected it might have been mistaken for a technological glitch. Individuals on the ground witnessed something more striking: a total solar eclipse, or a daytime blackout triggered by the moon blocking the sun and throwing its shadow on Earth.
Though total solar eclipses happen relatively frequently—about once every 18 months—seeing them is lucky. The strange overlap occurs during parts of the moon’s orbit when it is close enough to seem proportional to the sun from the perspective of someone on Earth. The brown blob captured from space is a time-lapse video of photographs of the shadow of the moon as the eclipse moved across our planet’s surface—stretching from the equatorial Pacific to the South Atlantic and passing through southern Argentina and Chile.
The moon’s path elongates by about an inch and a half every year, however. As it stretches away from Earth, the moon will eventually appear too small in the sky to cover up the sun. In about 600 million years, total eclipses will stop. The temporary nature of these alignments makes all their recordings valuable, even when the perspective makes what feels like a boundary-breaking moment—shocking darkness in the middle of the day—seem small.