And today, a total eclipse will be visible from coast to coast across the continental United States for the first time in 99 years. Total eclipses are rare celestial events in which the moon moves perfectly in between the Earth and the sun. For more than an hour today, the eclipse will be visible from Portland, Oregon, to the coast of South Carolina, and thousands of people are flocking to areas across the U.S. to get the best view of the event—although people should not look directly at the sun without special glasses. The next solar eclipse visible from the continental U.S. will be in 2024.