I stumbled on this amazing set of videos: physics legend Hans Bethe giving lectures on theoretical physics to his retirement community neighbors.

It's not as crazy as it sounds - a running joke around Ithaca (where I grew up and where Bethe's university, Cornell, is located) is that one of the top physics departments in the US is at the Kendal retirement community in Ithaca. In spite of the miserable weather, a large number of Cornell professors choose to retire there.

Few people can lecture coherently on quantum theory at age 93 (Bethe's age when he gave these lectures in 1999). Hans Bethe was incredible.