While sitting one day in a Caltech seminar room waiting for a talk to
begin, [Michael] Cohen found himself wondering what happens to a
physicist as he ages.  He turned to Feynman, who was next to him, and
asked his mentor, "How will I know when physics passes me by?"
Feynman simply smiled.  It was a beautful spring day and the windows
were open, a gentle breeze blowing outside.  Cohen, who had been
working late the night before, dozed off.  He next felt a nudge in the
ribs.  Waking with a start, he heard Feynman say to him, while
pointing to the open window, "There it goes, Mike.  Kiss it good-bye."

		-- Gino Segrè, "Faust in Copenhagen"