The coronavirus is teaching us a lot.
We’re learning more about our wives, husbands, children, or roommates as we are cooped up with them all day. Every day. We’re learning more about our neighbors as we look out the rear window to see what they do in their yards, on their balconies, or with their drapes open.
And we’re learning some math concepts, such as “exponential growth,” as we try to follow the spread of the virus.
Regular people, even the slightly nerdy who like to follow statistics, are used to things either going up and down or growing roughly linearly. The president’s poll numbers go up some days and down some days, as does your team’s winning percentage (remember sports?). Your slugger’s home run total climbs one at a time, and a few dozen homes are built into your town each year, so that you can say what the “pace of growth” is.
We’re growing by 60 homes per year. At this pace, Pete Alonso will hit 52 home runs …
But viruses don’t spread in this mathematically intuitive way, and so people are trying to wrap their minds around a mathematical reality that maybe they grasped for a couple of months in high school math but that doesn’t come naturally to our brains.
That’s why searches for the phrase “exponential growth” hit an all-time high in March, with about 50% more searches for it than the previous all-time high.
It’s the nature of viruses to spread exponentially. If every person who has the virus infects two other people (the low-end estimate for the coronavirus), then one case will make two new cases, and those two new cases will each make two new cases, which will each make two new cases.
Thus, the number of cases, or even new cases, doesn’t grow at some pace like home runs or wins, but it doubles at some pace. Thus, the United States went from 100 cases on March 2, to more than 200 on March 5, to more than 400 on March 7, to almost 800 by March 9, to 1,600 on March 12. The doubling every two or three days has continued, creating a line that looks like hockey stick.
Math professors are publishing videos explaining exponential growth. One such video, published March 8, has 5 million views.
This added math knowledge is no cause for celebration, of course, as it portends massive quantities of death and illness. Our new knowledge of exponential growth will be a lesson we wish we never had to learn.
