Subject: What is a 'Jiffy'

In Charles Pellegrino's book "Return to Sodom and Gomorrah"(22), he says a 
Jiffy is "The travel time of a beam of light across the diameter of a 
proton."  However, I can not find confirmation of this anywhere.  In 
various dictionaries, a jiffy is defined as a brief moment or something 
along those lines.  I'm inclined to not doubt Mr. Pellegrino, but have been 
unable to confirm this anywhere that I've looked.

Re: What is a 'Jiffy'