"Gravity," said Dirk with a slightly dismissive shrug, "yes, there was that as well, I suppose. Though that, of course, was merely a discovery. It was there to be discovered."

He took a penny out of his pocket and tossed it casually on to the pebbles that ran alongside the paved pathway.

"You see?" he said, "They even keep it on at weekends. Someone was bound to notice sooner or later."

Douglas Adams