"You ever put a full-length mirror on the floor, and then have a dog stand on it?" Trout asked Billy.

"No."

"The dog will look down, and all of a sudden he'll realize there's nothing under him. He thinks he's standing on thin air. He'll jump a mile."

"He will?"

"That's how you looked - as though you all of a sudden realized you were standing on thin air."

Slaughterhouse-Five ~ Kurt Vonnegut