To an an external observer it appears that time has stopped for photon. But this relation is reflexive, so for an observer travelling with the photon it appears the universe has stopped everywhere.
Is this right?
Space also gets distorted parallel to the direction of motion, but not perpendicular to it.
Does this mean that for an observer travelling with a photon sees spacetime as a flat plane?
Note 1: I'm using language vividly not literally when I say a photon experiences space and time. Not that I'm against idealist or panpyschist interpretations of matter or energy come to that.
Note 2: Since it's been pointed out that an inertial frame can't be boosted into the frame of a photon and moreover there is no limiting behaviour here – no matter what frame you are boosted into, light will always appear to travel at c. Nevertheless, when an external observer watches a train chasing a photon by gradually increasing its speed, he will note that the train speed is approaching the speed of the photon (but will never match it) and when he looks at the clock inside the train he will not too that it is gradually slowing down (but never actually stops). Using this picture, we can attempt the thought experiment – if not one that can be carried out – of what a world looks like to a photon.
Best Answer
There is no such thing as an observer traveling with a photon. Photons don't have experiences. So there's really no valid answer to this question.