Stuck in Minnesota for Monday's eclipse?
Don't despair: There's a way to track the historic event, while learning some astronomy, that works best in places that are outside the "path of totality." It's called an eclipse sundial, and you can make one with just a sheet of paper and an index card.
The instrument is the brainchild of Bill Gottesman, a Vermont physician who began making sundials when he retired from medicine a few years ago. Gottesman has made about 45 sundials, by his count, with several in public use at sites such as the University of Maryland and the National Renewable Energy Laboratory in Colorado.
Although humans have used sundials for centuries, Gottesman thinks his is the first in history that uses an eclipse to tell time. It's built on the principle that the obscured sun will cast a crescent image, with the crescent appearing to rotate as the moon moves across the solar surface.
To see how it works and make your own, visit Gottesman's website, eclipsesundial.com.