On August 21, the total solar eclipse will race across the continental US for the first time in 99 years.
Nearly anyone in the country can see the moon take a bite out of the sun during the epic event, weather permitting. Those in the path of totality can also watch the sun's bright disk vanish.
However, it won't be safe to look directly at the sun during the partial eclipse, as this can damage your eyes or even blind you. And that's why online retailers are selling out of protective eclipse glasses and experiencing frustrating shipping delays.
The good news is that you don't need special glasses to see a partial eclipse. In fact, everything you need to safely and clearly watch the eclipse is probably in one or two kitchen drawers — or, failing that, the palm of your hand.
The trick is a pinhole camera, which exploits a property of light called diffraction to bend and magnify light. In this case, that's the eclipsing sun.
A pinhole camera won't let you look directly at the sun — but in some ways, that's better, because a crowd of people can gather around your setup to watch, point at, and discuss its projected image.
Pinhole cameras can get pretty advanced with darkened boxes and tripods, but NASA's Jet Propulsion Laboratory has instructions for an incredibly simple version that you can build in a few minutes.
Grab some scissors, tin foil, a piece of thick card stock (or paper), tape, and a needle. Cut a hole in the middle of one sheet of card stock, tape the edges of a tin foil section over it, then carefully pierce the center of the foil with the needle — presto, you've made a pinhole camera.