I keep telling people this, and they never believe me: If I'm on an airplane and the guy next to me starts talking, if I want to keep talking I tell him I'm an astronomer, and if I want to sleep I tell him I'm a physicist. Well, now I have independent proof!
Seriously, all astrophysicists discover this independently. The first time we hear someone else say it we're not at all surprised to find out that someone else came to the same conclusion on their own. It's like gravity - lots of people discovered it. I can't wait till someone comes up with So-And-So's Laws of Airplane Boredom that describe WHY. ;)
(And of course, I usually then have to go and spoil things by telling the other person that astronomy doesn't involve looking through telescopes at stars, but instead looking at computers and programming.)