Some Relativity (was Re: Faster Than Light Travel - Reply)

Allan Goodall writes:
@:) At 05:19 PM 9/14/97 -0700, Donald wrote:
@:) >
@:) >The SCI.ASTRO FAQ page is COOL!! 8-D What these astronomy/physics
@:) >texts don't explain to me...If light has no mass (so it can
@:) >travel at the speed of light), how can anyone feel it?
@:) 
@:) Light has mass. What light doesn't have is a REST MASS.

  There was an argument about this recently on sci.space.  Technically
you are completely correct, however, several list members stressed
that these days they try to talk about momentum rather than mass,
because talking about different kinds of mass is confusing.  So light
has momentum but no mass, and particles have both mass and momentum.
A terminology issue but probably a very good idea (relativity is
confusing enough as it is).

-joachim