I've just replied to a thread about time dilation and something occurred to me. No matter how fast you travel, light will always appear to travel at 300,000kps(ish). Think about 3 photons travelling in the same direction 1 behind the other. Would the photon at the back percieve the 2 in front as travelling away from it at light speed? And would the 1 in front percieve the other 2 as falling behind at 300,000kps? But the poor little bugger in the middle would get horribly confused because both of the others would seem to be receding at 300,000kps (and that's faster than Neil's hair is receding!)

In the 2 twins case where 1 zips off on a journey at relativistic speeds, he will return having aged less than the twin who remains stationary. Therefore, from the perspective of the stationary twin time has passed more slowly for the twim who zipped off. The faster the moving twin travels, the less time will have passed for him relative to the other. Taking that to extremes, if the 1st twin had travelled at light speed then no time at all would have passed for him from the perspective of the 2nd twin; he would reappear an instant after leaving. Does this effect have something to do with my question about photons?

And this raises another question. If an object travelling at light speed appears to a stationary observer to travel any distance instantaneously, why does light take so long to reach us? Surely photons would appear to travel instantaneously too. WAAAAA my brain hurts again!

Any help appreciated.