On August 21, 2017, a solar eclipse will be visible across a section the continental United States, coast to coast, for the first time since 1918. A solar eclipse occurs when the Moon passes between the viewer on Earth and the sun, completely—and perfectly—blocking out the full diameter of the sun. During this event, if you are within the path of totality (the shadow of the eclipse), the sky darkens and you will be able to see the solar corona, the extended atmosphere of the