Our Moon sits at almost precisely the Sun’s apparent size, which is an accident, and totality exists because of it. Here is what that accident produces: a stretch of Egyptian desert where the shadow will hold for six minutes and twenty-three seconds in 2027, a simulator that runs the same geometry on Phobos and Io and shows you what you’d have instead, and a collection of the cheap cardboard people have held up at the sun since 1793.