Q.E.D.

Quod erat demonstrandum is the sign-off to mathematical proofs and formal syllogisms, sort of like the "-30-" at the end of a press release.

I referred earlier to another QED, quantum electrodynamics. Everything I know about that comes from physicist Richard Feynman.

I know of at least one reader who might enjoy watching Feynman lecture about physics. Here's a link to a series of about five hours of lectures that are totally fascinating, at times funny, and generally challenging.

You can get a sense of how preposterously weird this stuff is from the title of Feynman's best-selling book: Surely You're Joking, Mr. Feynman!

And a couple quotations:

If I could explain it to the average person, it wouldn't have been worth the Nobel Prize.

I think I can safely say that no one understands quantum mechanics.

By the way, and in case you were wondering too: As near as I can determine, the use of "-30-" comes from the practice of U.S. civil-war-era telegraphers who would signal the end of a transmission with "XXX," which is thirty, if you read it as Roman numerals.