Watching a Big Bang Theory rerun last night with Bob Newhart as the boys' childhood hero, Professor Proton. (Bob may be 85, but he is hilarious. My DH had never seen him in anything, and was blown away by how funny he is). Anyway, the professor is doing his kids' science show for Leonard, Sheldon and Penny. Along with Penny, I was amazed by the potato clock. I know it's a staple science demo, but I had no idea how it worked - I had to have DH explain it to me, and I'm still not sure I understand it.