I know that the rest frame of the photon is a non inertial reference frame. In that sense obviously the physics will not be Lorentz co-variant and so on. I have the following question Is possible to define a coordinate transformation from an inertial reference frame to the rest frame of a particle traveling at the speed of light? Obviously the coordinate transformation will not be a Lorentz transforms, but maybe another kind of coordinate transformation can do the trick. My idea is that we can use any reference frame to describe the physics. The laws of nature will be Lorentz covariant in any inertial reference frame, however if I do a coordinate transformation from an inertial reference frame to a non inertial reference frame then I can see how the laws will be in this coordinate system. Do you believe that this coordinate transformation can be found? For example, I can imagine the rest frame of the photon as a non inertial reference frame in which all the massive free particles will travel at the speed of light. My problem is to define a coordinate transformation from this reference frame to an inertial reference frame.