Hey guys this question is a bit basic but I always get caught up on the idea, I'm not in school for physics so I don't really have a prof to ask and most of the internet always skips ahead of this. Say I am in an inertial frame travelling close to C speed, the only thing I see is a photon in-front of me. In this reference frame I couldn't distinguish between my velocity being close to C or me just being at rest, so how in this reference frame do I come to the conclusion that the speed of that photon is = c and not just a few m/s? I'm assuming this has to do with time dilation but I don't know how to visualize that in this scenario. Thanks for the help!