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.

The opportunistic quality to this kind of merchandising—and the wider Zazzle-fication of the web—made me wonder whether eclipse goggles are more festive than functional. After all, the internet-assisted production chain allows for “T-shirts and coffee cups that can be printed with memes the day they go viral,” says Judith Donath, the author of The Social Machine: Designs for Living Online.

Properly manufactured eclipse goggles actually are useful, it turns out, but they still occupy a space made possible by the web: super-targeted merchandise for increasingly niche events. “We are, as a culture, parsing time more finely and more variously,” says Grant McCracken, an anthropologist who writes about the intersection of culture and commerce. “But—happily?—we have a new, more effective way to announce fleeting products that can mark these time ‘slivers.’”

An eclipse is about as slivered as it gets. If you’re smack-dab in the middle of the path of totality, a 70-mile-wide moonshadow that runs from Oregon to South Carolina, the entire thing begins and ends in under three minutes. It’s a bit like New Year’s Eve, which can be boiled down to the last minute of the old year and the first moments of the new one, and which, incidentally, is another occasion for funny-looking glasses.

For those lucky enough to find themselves in the Oregon-to-South-Carolina path of totality, eclipse goggles are only necessary before and after the total eclipse. It’s safe to take them off “only when the moon completely covers the sun’s bright face and it suddenly gets quite dark,” NASA says on its eclipse safety website. “Experience totality, then, as soon as the bright sun begins to reappear, replace your solar viewer to glance at the remaining partial phases.”

A map of the United States showing the path of the August 21, 2017 total solar eclipse. (NASA)

Glasses will be quite helpful for the the vast majority of Americans outside of the path of totality, where the eclipse will remain partial and it will never get completely dark. That said, you don’t need eclipse specs if you want to view the eclipse indirectly—as in, you can still be outside for the event, you just cannot look up. (Seriously, don’t do it. Looking directly at the sun can cause permanent retinal damage, even when it’s painless. NASA has a special website devoted to safe eclipse viewing.) The middle-school-science-class version of an indirect eclipse viewer is a pinhole projector—you can build one with two pieces of paper and a paperclip. This way, you can see a shadow of a crescent-shaped sun on a piece of paper rather than in the sky, all while protecting your eyes. (Shout-out to my sixth-grade science teacher Mrs. Sevareid, who demonstrated this technique for me and my classmates during a partial solar eclipse a couple decades ago.)

For direct observation, however, the DIY route isn’t an option. Regular ole Ray-Bans will not protect your peepers. Even welder’s glass is no good unless it’s at least shade 14 or darker, NASA says. Hence, the special goggles. “These are not sunglasses,” Young says. “I’ve certainly read some really bad bits of misinformation. You can’t—I don’t even know where this came from—but you can’t use old film negative. That’s just completely wrong.”

“These things block out such a huge amount of light they’re hundreds of thousands of times stronger than regular sunglasses,” Young adds. “When you look outside you only see the sun.”

So you wouldn’t want to wear eclipse goggles while, say, driving a car?

“You definitely don’t even want to wear them driving,” Young says. “You don’t even want to wear them walking around.”