Today I’m going to be talking about scale. Specifically, about the important practical difference between tiny stuff and really, really tiny stuff. (Scientists, of course, have a better way of comparing the sizes of things than tiny vs. really, really tiny: the metric system. We’ll get to that.) If your students want to understand why masks are so important, they’re going to need to think about scale. A fun way to start is through this amazing interactive that I used when I was in the classroom — when you move the scale bar at the bottom, it zooms in so you can see a cell (tiny) compared to a bacterium (really tiny) to a virus (really, really tiny).
So why is understanding scale crucial to understanding the importance of masks during the coronavirus pandemic? The take-home message of my April 2020 article “Don’t jump the gun” three months ago was that when science is moving fast, early reports need to be greeted a bit skeptically, since understanding will change over time. In that article, I mentioned masks and—as predicted—our understanding of their utility has indeed changed.
In early April, public health authorities were saying that the public need not wear masks. They didn’t want people to hoard medical-grade masks when they were desperately needed by medical professionals. Furthermore, because of how the virus was believed to spread, masks were not thought to be a very important preventative measure. However, a new concern has recently emerged that has changed the conversation completely. A large group (239 people in 32 countries) of researchers and scientists have argued that COVID-19 is very likely to be spread by airborne transmission and urged the World Health Organization to take a stance on this issue immediately for the safety of all.
Is this information new? Didn’t we already know that COVID-19 could travel in droplets through the air? Well, yes. But the key is what do we mean by droplets, and this is where scale becomes really important.