Sorry if I misunderstood you. Yes the astronomical red shift is indeed caused by the stretching of space. But that doesn't matter to the speed of light. The speed of light is the same for any observer at any time or any place. The stretching of space (astronomical red shift[asr]) doesn't cause the speed to change, just the wavelength. Assume the following line represents the wave packet of a photon as it leaves the source at time t0.
----------------
Then at time t1 at a point in space so that the asr is 2.0 (.5?), that is the time interval between the emission and observation is far enough that the distance has doubled. Now the wave packet will look something like this.
- - - - - - - - - - - - - - - - -
Well, I hope that is about the right length. The second wave packet should be twice the first one.
Anyway, the speed doesn't have to change, the wave is just spread over a greater distance.
The best I can say about the internal clock of the photon is that it doesn't matter. The following is a top of the head discussion, and may not be completely right. I hope it will cover the situation adequately.
The photon exists from the time of emission to the time of absorption with no notice of the passage of time. It seems to me that the photon itself doesn't change when it is red shifted. Only our observation of it changes. And if I think any more about it I can see getting myself all wrapped up in words that don't really mean anything. The basic thing about this is that time has no meaning to the photon. It isn't like the neutrinos which can oscillate between the 3 forms if they aren't traveling at the speed of light.
Bill Gill
