A couple of months ago I discovered the website for the so-named microCOVID project. What’s a microcovid? It’s a unit by which one can estimate risk of contracting covid based on one’s lifestyle - things such as how one travels to work, with how many people, how far apart and so on. One can enter one’s risk apetite and the website will show whether the indicated activities put someone above or below that threshold. It’s still a new project and the science is still imperfect but I’ve learned a bit from it about relative risks.
That website made me think of af few other unusual units (by which I mean non-SI) -derived) that I’ve encountered. The first one that comes to mind (and from which I suspect the microCOVID was named) is the micromort, a measure of mortality risk for certain events, such as travelling (by whatever mode of transport), smoking, skydiving, living in a city etc.
Next up there’s the Helen (with the milli-Helen being the most common multiple), based on the character from Homer’s Iliad, Helen of Troy whose face is said to be so beatiful that it launched a thousand ships.
Another one relevant to the pandemic (or perhaps more to the lockdowns) is the beard-second, which as its name suggests, is how fast the average beard grows in one second. The exact value differs (it’s not an SI unit. afterall) depending on which defintion ones uses, but 5nm and 10nm are the typical values.
There’s a whole load of them on Wikipedia falling into two categories Humorous and Unusual. There’s little point in me reproducing them all here but it makes for a fun distraction - if a foray into metrology is your sort of thing.