On August 12, a rare total solar eclipse will be visible across a swathe of northern Spain, turning day into night for under two minutes. This is the first total solar eclipse visible from mainland Europe in 20 years, since 2006. The eclipse occurs when the Moon passes directly between the Sun and Earth, casting a narrow shadow. This cosmic event, described by NASA as a "cosmic coincidence," happens because the Sun is about 400 times larger than the Moon but also about 400 times farther away, allowing the Moon to perfectly cover the Sun and reveal its corona.