Jerry Stuckle wrote:

snip

I understand it has no rest math. But where does the mass come from?
There has to be mass to exert pressure. Does the mass just appear from
nowhere? I doubt it...

This is rather circular, but...

It comes from the energy of the photon and the energy of the photon
comes from whatever created the photon.

Specificially it come from the energy-momnetum relation.

See:

http://en.wikipedia.org/wiki/Mass_in_special_relativity

Look at the paragraph labled: The relativistic energy-momentum equation.

One way to look at it is that relativistic mass is not a real mass but
an effect that is equivelant to a mass.

If you really want to have something to wonder about, read up on tachyon
fields and imaginary mass:

http://en.wikipedia.org/wiki/Tachyonic_field


--
Jim Pennino