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lmm comments on Stupid Questions Thread - January 2014 - Less Wrong
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On the Neil Degrasse Tyson Q&A on reddit, someone asked: "Since time slows relative to the speed of light, does this mean that photons are essentially not moving through time at all?"
Tyson responded "yes. Precisely. Which means ----- are you seated?Photons have no ticking time at all, which means, as far as they are concerned, they are absorbed the instant they are emitted, even if the distance traveled is across the universe itself."
Is this true? I find it confusing. Does this mean that a photon emitted at location A at t0 is absorbed at location B at t0, such that it's at two places at once? In what sense does the photon 'travel' then? Or is the thought that the distance traveled, as well as the time, goes to zero?
In the photon's own subjective experience? Yes. (Not that that's possible, so this statement might not make sense). But as another commenter said, certainly the limit of this statement is true: as your speed moving from point A to point B approaches the speed of light, the subjective time you experience between the time when you're at A and the time when you're at B approaches 0. And the distance does indeed shrink, due to the Lorentz length contraction.
It travels in the sense that an external observer observes it in different places at different times. For a subjective observer on the photon... I don't know. No time passes, and the universe shrinks to a flat plane. Maybe the takeaway here is just that observers can't reach the speed of light.