On Thu, 23 Jun 2005 08:57:07 +1000, "Mike Kreuzer"
>OK, out of all this, this is the bit I still don't get. Maybe I didn't go
>the day this was explained in high school or something, but isn't momentum =
>mass * velocity? So no mass, no momentum?
But photons _don't_ have zero mass. They have zero _rest mass_. But they
are never at rest. Their actual mass is not defined, but is real and
positive (photons have energy, and that is the best way to work with the
mass equivalence). Consequently they have momentum.
Chris L Peterson