While total solar eclipses happen about once every 18 months somewhere on Earth, the Aug. 21, 2017, eclipse was rare in its long path over land. The total eclipse lasted about 90 minutes, from the time it first reached the Oregon coast to when it left the North American mainland in South Carolina. This long, uninterrupted path over land provided scientists with a rare chance to investigate the sun and its influence on Earth in ways that aren’t usually possible.