You might remember learning as a kid that if you see lightning and count the number of seconds until you hear thunder, then for every five seconds it takes, the lightning is one mile away. How good is this estimation really? It turns out that based on simple physics, it is actually pretty good. You can read more at EarthSky at https://earthsky.org/earth/how-far-away-lightning-thunder.

Source: David Selby/Commons Wikimedia