Why Total Solar Eclipses Are So Rare
The solar eclipse that will cross the continental U.S. this Aug. 21 will attract a huge audience — and rightly so. The millions of people who are expected to witness the astronomical event won't show up just because solar eclipses are exceedingly beautiful — they're also exceedingly rare. Here's why.
A solar eclipse occurs when the moon passes completely in front of the sun, casting a shadow that darkens a portion of the Earth.