During the Great American Total Solar Eclipse on Aug. 21, millions of people will gaze at the sun to see the moon slowly pass in front of it, blocking out the light. But those who aren't careful risk doing some nasty damage to their eyes.
You've probably been told that it isn't safe to stare at the sun and that watching a solar eclipse without proper eye protection can make you go blind. That's because the light from the sun is so intense that it can literally burn your eyeballs — even during a solar eclipse, when part of the sun's disk is still visible.
Even the tiniest sliver of a crescent sun peeking out from behind the moon emits enough light to scorch your eyes, Ralph Chou, professor emeritus at the School of Optometry & Vision Science at the University of Waterloo in Canada, told Space.com. "I have seen instances where the patient has eventually shown up with crescents burned into the back of the eye, and you can almost tell exactly when they looked." [How to View a Solar Eclipse Without Damaging Your Eyes ]