Well done Socratus! You have brought us back, at least close to the point where Gan set things in motion.
With regard to your questions, I would suggest trying to think of time as a static entity, through which we are moving. In that way, time does not have to change from being “frozen” to being variable, any more than space has to change when we start to move about.
Only in the frame of reference of an observer does time appear to change. True, relativity tells us that an observer in motion relative to something else can with equal validity consider herself to be moving, or the “something else” to be moving, but in the case where the “something else” is time that may make no more sense than Einstein’s alleged question: “Does Oxford stop at this train?”
A photon travelling through a vacuum must, as you say, be stationary in time. However, if it passes, for example, through the Earth’s atmosphere it slows slightly, thereby experiencing some passage through time in its F of R, but time remains unchanged.
I would argue that time does not depend on either speed or mass. Only an observer’s perception of time is altered by these things, and then only in his F or R.
Here’s a question though. The photon in a vacuum must be at every point on its journey at the same time. If it is going from A to B, it must be at B at the same time that it leaves A. Now suppose that between A and B it passes through the Earth’s atmosphere which slows it down slightly, so it experiences a passage through time, thus delaying its arrival at B. Now we have a situation in which the photon is at A and B, in its F of R, at the same time; but it also arrives at B shortly after leaving A, also in its own F of R. What is more, this situation is not improved if we reason that we cannot know anything about what the photon does on its way between A and B. How can it arrive in one place at two different times in its own F of R?
