# Special relativity and photon dimensionality

1. Apr 24, 2012

### Aziza

according to length contraction, L=Lp√(1-v^2/c^2), where Lp is proper length as measured by observer at rest with respect to the two ends of the object. So the length of objects moving relative to us we measure as less than the length the observer at rest measures.
Applying this to light itself, if you plug in c for v, you get zero, so does this mean that a photon necessarily has no dimensionality to it as viewed in our reference frame? And does this mean that in its own reference frame, the photon does possibly actually have some length/width/etc?

2. Apr 24, 2012

### phinds

A photon doesn't HAVE a reference frame.

3. Apr 24, 2012

### Aziza

sorry i didnt mean reference frame, bad wording. I guess I just mean that if you travel along with a photon such that the photon is stationary to you, will the photon have a length/width/etc? I am basically confused about how we can say light is also particle if that particle has no dimensions

4. Apr 24, 2012

### elfmotat

That's what phinds was saying: you can't travel along with a photon so that it appears stationary. Light travels at c in every frame, which means you can't possibly find a frame in which it is stationary.

5. Apr 24, 2012

### Aziza

ohh i see right right. ok but still, lets say light itself measures its own proper length. Since in all frames, light moves at same speed of light, then in all frames we would say light has no length. But this does not mean proper length of photon is zero. right or no?

6. Apr 24, 2012

### phinds

You (or a photon) can only measure length in a reference frame. A photon doesn't HAVE a reference frame, so your question is meaningless.

7. Apr 24, 2012

### Aziza

oh...so basically there is no way to apply special relativity to light itself to get any meaningful results?
also however im still curious, does photon have any known dimensionality to it?

8. Apr 24, 2012

### phinds

Now that's a reasonable question. I THINK, and I'm not an expert here, is that you have to say no because although it acts like a particle in some experiments, it's basically a wave and you can't hit a photon with a photon. Obviously a photon DOES hit other things, but that's because THEY have size.