Water is wet. The sky is blue. The sun is bright. Okay, no, but the sun is really bright. Really, really bright.
“Even when 99 percent of the sun is blocked out by the moon, the amount of light is still 10,000 times stronger than a full moon,” says Alex Young, the associate director for science in the heliophysics division of NASA’s Goddard Space Flight Center. “So even when there’s 1 percent of the sun still visible, it’s still too bright.”
Too bright for human eyes, that is. People are generally pretty good at not staring directly at the sun for this reason. It’s when most of the sun is blocked out, like during an eclipse, that things get a bit dicey. And this is why, during the partial phases of an eclipse—just before and after the sun appears to be almost totally blotted out—you should never look directly at it. And it’s why, with a rare solar eclipse approaching in the United States on August 21, there’s suddenly a cottage industry around eclipse safety goggles.
“We call them safe solar-viewing glasses,” Young told me. “They’ve at least existed for most of the 21st century. You need them to safely observe an un-eclipsed or partially eclipsed sun directly.”
If you search a retail website like Amazon for “eclipse” these days, you’ll be inundated by eclipse-related eyewear. That includes unsafe knockoffs, NASA warns. NASA is now recommending only using eclipse glasses that have been manufactured by four U.S. companies: American Paper Optics, Rainbow Symphony, Thousand Oaks Optical, and TSE 17.