OT:Tempted to get this book

[Jack Simth]

narf poit chez BOOM said:
If light has mass and goes at lightspeed, how come we're not all squished?
Best answer I can think of is that light ignores that rule and simply exerts force according to it's mass. What that might mean, I don't know.

It's been a while since I've taken physics but ....
Light has 0 rest mass, and thus 0 rest energy. However, it travels at the speed of light. The equation for the energy (mass, energy; essentially the same thing in modern physics) of an object is something like E = sqrt(1/(1-(v^2/c^2)))mc^2. For light, m = 0, but v = c. The equation then translates to
E = sqrt(1/(1-(c^2/c^2)))(0)c^2
= sqrt(1/(1-1))(0)
= sqrt(1/0)(0)
= (1/0)(0)
= (0/0)
Which is mathamatically undefined. However, the universe comes up with an answer! It's a particular constant over the wavelength of the light, for any given photon (there's something similar for the inertia of the photon). Fortunately, it's a VERY SMALL constant, so it takes a LOT of photons to have any measureable impact when they hit you.