The last term of the Drake equation is a term for the lifetime of a civilization capable of sending radio waves into space. If it's a century or two, this would provide the answer to Fermi's paradox, "Where are the aliens?" Answer: they drank bleach. https://twitter.com/CNN/status/1253649913155670019

If you don't know what the Drake Equation is, you're missing a master class in "back of the envelope" order-of-magnitude thinking. To me, this is one of the most under-recognized and under-appreciated methods of science.

https://en.wikipedia.org/wiki/Drake_equation