A total solar eclipse will be visible across the US on Monday, August 21. Shannon Schmoll, director of the Abrams Planetarium at Michigan State University, explains why and how it happens, and what we can learn from an eclipse.
A solar eclipse happens, on average, a couple times a year. The moon passes between the Earth and sun every 29 days, a time we call the "new moon" – when the moon is not visible in Earth’s nighttime sky. However, the moon’s orbit and the sun’s path in our sky don’t match up exactly, so at most of those new moon events, the moon appears above or below the sun.