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> If you are having difficulty grasping this
I don't think I am. Compare my longer comment in this thread <https://news.ycombinator.com/item?id=32462046> which makes reference to Wald's standard textbook. It's not just Wald - any standard textbook will agree. I can give you chapter references for practically any of them if you like.
What I was wondering was how you reconcile the difference in time at a RADAR station when receiving photons bounced off targets at different spatial distances with, quoting you, "the photons do not travel any distance and they do so in zero time".
Surely time passes at the RADAR transceiver? Otherwise, wouldn't we get instant returns back from the Moon and Venus, instead of having to wait seconds to minutes?
A broader question might be, "is there a 'best' clock for analyzing a RADAR detection, and if so, which clock?".
Finally, you might want to wonder if an in-flight photon changes spin states or frequency. Doesn't a RADAR photon bouncing off a moving target (or returning to a moving transceiver) undergo a doppler shift, and thus change of frequency? How do police RADAR guns work if photons do not feel time?
It strikes me that you didn't care to answer my earlier RADAR questions at all among your five paragraphs in reply. If you don't care to do so, or you don't want think about any of this, that's fine. But I think you should take care in judging how much or how little anyone on hackernews might know about relativity, or what ideas about sci-fi-like-concepts they might entertain.
From the frame of reference of a transmitted photon, the transmission is instantaneous, and the spatial distance traveled is zero.
From our perspective, it is a different story. If you are having difficulty grasping this, perhaps you are thinking that photons are like tennis balls but with a very high velocity. Perhaps you even entertain the sci-fi notion of faster than light travel.
However, speed of light in a vacuum is a much more fundamental limit than an inherent velocity limit of some particle.
It is essentially the default propagation speed of all physical information. Interaction of light with matter causes absorption and re-emission of photons, which causes light to both slow down in a medium and pick up some information about whatever it went through.