By now, the science is settled: Wearing a mask is the easiest, least intrusive way to slow the spread of the novel coronavirus. Understanding why isn’t hard, but it’s not always intuitive, either. If you are looking for a handy explainer, try this YouTube video from It’s Okay to Be Smart.
Viruses can be difficult to understand because they’re invisible to the naked eye, traveling inside water droplets on unseen air currents. With a technique called schlieren imaging, though, we can see these air currents, and that’s what It’s Okay to Be Smart uses to demonstrate how masks work.
The science behind schlieren imaging is a little complicated, involving a spherical mirror bending light in subtly different ways to reveal differences in density that would otherwise be invisible. It’s important to note that this doesn’t let us see viruses—they’re too small for that—but it does let us see how air flows when we exhale.
Using a combination of slow motion and schlieren imaging, the video reveals what a cough looks like with and without a mask. The differences are striking. The unmasked cough creates a massive plume of potentially virus-laden air, traveling much farther than you’d expect—about 2 meters, which is why social distancing means staying outside that zone.
A mask does two things: First, it captures much of the droplets expelled when you cough, sneeze, or breathe; second, any that aren’t captured have their momentum blunted, keeping them from traveling very far. That means less chance of infection for people around you. The bottom line is that masks work—and this is a good video showing you exactly why.
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