On August 21, 2017, a total solar eclipse will sweep across the continental United States, marking the first time in nearly 40 years that a total eclipse has been visible there. For millions of Americans, this eclipse represents their first opportunity to view a total solar eclipse.

However, the question has been asked over and over again: Why is the path of the eclipse moving from west to east? Doesn’t the moon move from west to east? The answer is complicated but we break it down for you in this video!