[The_Victor]

Photons don't have any mass, doo they? And they still obey the limit

Photons (i.e.light) do have mass. There is an experiment setup that you could buy that looks like a light bulb with a sort of windmill inside of it, that proves it. I'll see if I can find a link.

[Les_Miserables]

I think the experiment you refer to is a demonstration of black surfaces and heat reflection not photon energy/mass but I could be wrong..was once.......

[Pessimist]

I've seeen those, but I was never really certain how they worked.

So you're claiming light has weight?

[Netheron]

The photons have a momentum, not a mass.

Anyway, the windmill/lightbulb doesn't really have much to do with photon momentum, it has more to do with differences in temperature on the vanes and the gas molecules inside the bulb.

[guitar4jesus]

Crooke's Radiometer

[gomaaa]

Photons (i.e.light) do have mass. There is an experiment setup that you could buy that looks like a light bulb with a sort of windmill inside of it, that proves it. I'll see if I can find a link.

I don't think photons have mass, as such, but they do have momentum. Please check me on this, as it's been a while since I've had to use these formulas. Einstein's special relativity equation looks like:

E^2 = p^2 * c^2 + m^2 * c^4

where E=energy, p=momentum, m=mass and c= the speed of light. If you have a motionless particle, set p = 0 and you get

E = m * c^2

which everybody knows. If you have a massless particle, like a photon, set m = 0 and you get:

E = p * c

So photons have mass and can do things like run the little fan inside the light bulb (just like air molecules hitting it would transfer momentum and turn the fan, so do photons), if you ever find the link. I couldn't find it either, but I think I know what you're talking about.

PS. Does anyone know if I can use LaTeX equations when posting to FR? Heck, I'll give it a try:

$E^2 = p^2 c^2 + m^2 c^4$

[furball4paws]

You can buy this home science stuff from Edmund Scientific. They got lots of goodies.

[gocats]

Now wait a minute I was always taught that light i.e. photons had no mass. If they had mass and traveled at the speed of light wouldn't their mass be infinite?