# Quick question about the speed of light.

1. Aug 27, 2010

### agent_509

From what I understand, we can never reach the speed of light because it would require infinite energy, because our momentum would be infinite. But if that is the case, wouldn't light have infinite momentum and therefore infinite energy? Or am I an idiot and 'the speed of light' is just a term that has nothing to do with light?

2. Aug 27, 2010

### Nabeshin

Since light has no "intrinsic", or rest, mass, the same rules do not apply to its energy/momentum as do for massive objects such as electrons, protons, and humans.

The rules applying to light state that its energy is proportional to its frequency, and its momentum has a similar relationship, only with a factor of 1/c:
$$E=\hbar \omega$$
$$p=\frac{ \hbar \omega}{c}$$

3. Aug 27, 2010

### agent_509

okay, I understand now, thanks!