# Massless particles and C

1. Dec 15, 2006

I know photons have no mass but are there other particles that have no mass and if so can they travel at the speed of light?

Last edited: Dec 15, 2006
2. Dec 15, 2006

### mathman

Gravitons (yet to be discovered?) and gluons (strong nuclear force carrier) have no mass. Gravitons travel at the speed of light. Gluons (in ordinary circumstances) exist inside nuclei, so they don't travel much.

3. Dec 16, 2006

### rbj

and, if they travel at speed, c, they gotta have no rest mass (which is what we mean by "massless"). photons actually do have mass, namely:

$$m = \frac{E}{c^2} = \frac{h \nu}{c^2}$$

just no "rest mass" a.k.a. "invariant mass".