"I don't know how I'm going to say it so you'll understand, but time is just as much a dimension as length and breadth." He frowned. He wanted to talk about Wells's Time Machine but he knew that'd be no use -- these folks didn't read that sort of thing. "If the earth had settled down, we'd have been lower. If it had settled to one side, we'd have been moved one way or another, but as it's settled back in the Fourth Dimension, we're going back in time."
"We're in a runaway skyscraper, bound for some time back before the discovery of America!"