On another forum I got dog-piled by a bunch of folks with the faux-patient condescending tones of educators handling a dolt, insisting that the two legs of 120/240v split phase residential mains are 180 degrees out of phase with each other. This has happened more times than I can count, and I had enough of it. So I made this video. Hopefully it can be of use if the topic ever comes up here. Peer review welcome, I've already caught one error and corrected myself.