# Proper Length and Photons

1. Jun 5, 2005

### DougBTX2

Hi all,

If I have a length $L_p$ of an object which is at rest in my frame of reference, it will have length $L = L_p (1 - \frac {V^2}{c^2})$ in an inertial reference frame moving with speed $V$ relative to me. If this frame is following a photon at speed $c$, that makes $L = 0$.

If my object is the universe, it seems like my photon thinks it is everywhere at the same time, because the distance to anywhere in its IFR is zero. How does that work?

Douglas

2. Jun 6, 2005

### Meir Achuz

You cannot make a LT to the rest frame of a photon.
A photon does not have a rest frame.
You have given some reasons why.

3. Jun 6, 2005

### James R

"LT" = "Lorentz transformation", by the way.