Ask him what time it is
You’ll see what I mean
You’ll learn all about how clocks are made
All the stages there have been.
From medieval candles
Through sundials and Swiss jewels
To Caesium atoms decaying in somewhat random fashion

He may just mention the odd dissertation  Regarding the possible application
Of quantum physics to GPS
As a kindness.

You may catch your train…or a less interesting one

In the next half life.