Why does it always seem like the elevator is going down when you need to go up? Is it really true that 0.99999 . . . with an infinite number of 9s after the decimal point, is equal to 1? What do tea leaves and river erosion have in common, per Albert Einstein? Does seeing a bed of red flowers help prove that all ravens are black? Can we make sense of a phrase like "this statement is unprovable"?