"Tell me what time is," said Harrigan one late summer afternoon in a Madison Street bar. "I'd like to know." "A dimension," I answered. "Everybody knows that." "All right, granted. I know space is a dimension and you can move forward or back in space. And, of course, you keep on aging all the time." "Elementary," I said. "But what happens if you can move backward or forward in time? Do you age or get younger, or do you keep the status quo?" "I'm not an authority on time, Tex. Do you know anyone