Sonny's physics' teacher canceled the class today. As I picked Sonny up from the BART (Bay Area Subway system), we talked about the reason why this could happen. "I think," - said Sonny - "he just had a baby". "Mmm," - I answered - "yep, how often does that happen: a man having a baby?!" Without missing a beat, Sonny quipped: "Yeah, the physics of it!"