“Knowledge of physical laws can, in some cases, give you the confidence to confront surly people. A few years ago I was having a hot cocoa nightcap at a desert in Pasadena, California. Ordered it with whipped cream, of course. When it arrived at the table, I saw no trace of the stuff. After I told the waiter my cocoa had no whipped cream, he asserted I couldn't see it because it sank to the bottom. But whipped cream has low density, and floats on all liquids that humans consume. So I offered the waiter two possible explanations: either somebody forgot to add the whipped cream to my hot cocoa or the universal laws of physics were different in his restaurant. Unconvinced, he defiantly brought over a dollop of whipped cream to demonstrate his claim. After bobbing once or twice the whipped cream rose to the top, safely afloat.

What better proof do you need of the universality of physical law?”