« on: 19/11/2017 15:16:54 »
Quote from: Demalk
Which makes sense according to Einstein, because they are travelling so fast that they don't experience any time at all. To them all events happen instantaneously. The entire universe, to a photon, is instantaneous.
I don’t think Einstein said that, but opinions are divided; quot sapientes, tot sententiae.
It is fascinating that one physicist can say categorically that photons don’t experience time, but another can say the opposite. The way I understand it goes something like this:
Special relativity provides for an inertial frame for everything that has mass, but it does not cover massless particles such as the photon. Talking of the photon having a frame of reference is, strictly speaking, not scientific. The photon must always be observed as travelling at “c”. It cannot be at rest relative to anything. Of course, one could argue that it must be at rest relative to itself, but that is not a very productive line of reasoning. Science has not actually produced definite proof that the photon cannot be assigned an inertial frame, but to maintain that it does have one is pure speculation, and maintaining that it does not have one seems to be the generally accepted position.
Taking the time dilation equation to its ultimate conclusion may seem a logical thing to do, but it is not supported by special relativity because of the lack of mass of the photon which puts it outside the remit of special relativity. It seems that the best we can say is that we have no way of knowing if photons experience time, or not. Nor do we have any scientifically accredited theory that covers this, nor any way to test the idea experimentally, as no massive object can reach the speed of light, and a clock cannot be fixed to a photon.
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