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If time slows down the closer you get to the speed of light, does it follow that time does not exist for photons. Do photons - even if they travel across billions of light years of space - arrive at the same time as they are created? And if this is so, does this not explain the peculiarities of the double-slit experiment?

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  • $\begingroup$ Please identify exactly which double-slit phenomenon you're referring to. $\endgroup$ – Carl Witthoft Aug 3 '18 at 14:29
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    $\begingroup$ Electrons also show interference pattens passing through a double slit, and they do not travel at c. $\endgroup$ – James K Aug 3 '18 at 14:32
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    $\begingroup$ I'm voting to close this question as off-topic because this a pure physics question with no astronomy $\endgroup$ – James K Aug 3 '18 at 14:33
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    $\begingroup$ A pure physics question and I'd suggest you start reading at Would Time Freeze if you could travel at the speed of light ? on Physics SE. $\endgroup$ – StephenG Aug 3 '18 at 15:12
  • $\begingroup$ This is on the hot network. Shame it needs to be closed. $\endgroup$ – Sir Cumference Aug 3 '18 at 18:08
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Time does not exist for photons. Quoting Wikipedia's somewhat unnecessarily technical page:

In relativity, proper time along a timelike world line is defined as the time as measured by a clock following that line.

The proper time between any two points along any photon's path in empty space is zero. So the photon "experiences" no passage of time.

It's not very clear to me how this could explain the double-slit experiment. Proper Time is an entirely relativistic concept, whereas the double slit results are not explained by relativity, but are explained by Quantum Mechanics.

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  • $\begingroup$ Why not stick with the wave-like method of explaining Double-Slit? Or are you referring to the more recent experiments showing a single photon going thru both, or even different quantum numbers going thru different slits? $\endgroup$ – Carl Witthoft Aug 3 '18 at 14:28
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  • $\begingroup$ Mark, the photon doesn't take zero time to traverse from point A to point B. During that traversal I can put an asteroid in its way. It's the same for you if you're travelling at 99.99999999999% of the speed of light. You won't be aware of me putting that asteroid in your way. But BLAM! and everybody else will. Then everybody else will concur that time did exist for you, even if you weren't aware of it. $\endgroup$ – John Duffield Aug 4 '18 at 14:35
  • $\begingroup$ @John Duffield: I didn't say that the photon takes zero time to traverse its path. I said the proper time along the path is zero, which is quite a different thing. Proper time essentially is the time a clock moving along a path in spacetime records as elapsed. It is not what an outside observer experiences, which is what you're speaking of. You can see that the zero time experienced by a photon is the limit of the time experienced by a spaceship as the ship approaches lightspeed. The faster the ship goes, the less time is experienced onboard, asymptoting to zero at lightspeed. $\endgroup$ – Mark Olson Aug 4 '18 at 14:57
  • $\begingroup$ You also said time does not exist for photons, but it does. Ditto for those people on the ship. They might experience no time, but it still takes them 4 years to get to Alpha Centauri. That's if I don't put an asteroid in their way. Time exists for them even though they don't experience any. So that's a -1 from me I'm afraid. $\endgroup$ – John Duffield Aug 4 '18 at 15:10

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