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Where does your claim that photons don't move come from? Very simply, the Sun is 8 minutes from the Earth. The photon is most definitely moving from the Sun to
by sahil50 5y ago
Where does your claim that photons don't move come from? Very simply, the Sun is 8 minutes from the Earth. The photon is most definitely moving from the Sun to the Earth.
- krastanov 5y agoThey are talking about "intervals" in 3+1 dimensional space time. To explain it rigorously, one needs to define a few terms like "metric" or "light cone". One defining property of the photon is that its space-time interval between any two events in its history is zero. You can think of it as the dual of the fact that a clock moving at the speed of light would be completely stopped.
- Filligree 5y agoIntervals are the square of the distance, so not quite, but… yes. There’s a tendency to treat spacetime intervals as something abstract and possibly metaphysical, because we can’t see or touch them, and they work counterintuitively. They’re actually the opposite. Our normal experience of 3D space is what is unphysical; the (square root of the) spacetime interval is simply distance, measured in meters. Or seconds, of course. The literal, physical distance between an absorption and emission event is always zero. Reality is non-Euclidean. The Manhattan distance is larger than the actual distance, which is usually true anyway. Well, I suspect I just spent a lot of words telling you something you already knew, so I’ll leave off with a book recommendation. Dichronauts, by Greg Egan. Between that and the Clockwork Rocket trilogy, I don’t know a better way to inculcate an intuition for special relativity. One is set in a 2+2 spacetime; the other in 4+0. The differences are instructive.
- krastanov 5y agoThis made me laugh given that, actually, Greg Egan is by far my favorite author. But I also think you are going way too far by saying that our normal 3D space is what is unphysical. The fact that our everyday reality is the limit of a more interesting reality when some parameter becomes small, does not make it any less real, for any reasonable definition of "real".
- Filligree 5y agoWell, it's certainly consistent. And for the most part you're right; it's just light that gets hard to understand from this perspective. Unfortunately photon behaviour is fairly important...
- Godel_unicode 5y agoBriefly, from special relativity. As something approaches the speed of light, time slows down for it. At the speed of light (through vacuum) time stops, and in that reference frame there is no such thing as distance.
- sahil50 5y agoThoughts on gravitational lensing point above? From the photon's point of view, it is experiencing changes through time and space.
- Godel_unicode 5y agoThat point misses (or rather ignores) the larger point. Ignoring special relativity because you think Einstein was "lost in the notation" is an extraordinary claim for which no extraordinary proof exists.
- sahil50 5y agoNever said that. I'm solid on speed of light as a max, gravitational lensing, gravitational redshift, and all the real world measurements that are in total sync with relativity. The point is that I think claims like "distance doesn't exist" is the kind of thinking that comes from people lost in notation.
- programmer_dude 5y agoIt's 8 minutes for an "external" observer. Physicists say the photon itself does not experience time or space.
- sahil50 5y agoThe photon does experience change over time and space. Take gravitational lensing by the Sun. The photons that we see from behind the Sun, are definitely affected by the Sun. From the photon's point of view, it is experiencing changes through time and space. Thoughts?
- ithinkso 5y agoNot from the photon's point of view. It is emitted and absorbed immediately. The distance traveled (in 4d spacetime) of a photon is always 0, no matter (pun intended) what's in between or what you observe.
- sahil50 5y agoI don't think it is true to say that "it is emitted and absorbed immediately", because there is a very real difference from a photon going from the Sun to the Earth, to a photon going from the Sun to Jupiter. I know the theory the view you're saying comes from, and the weight it has in academia, but it always struck me as useless. And that whoever came up with it was lost in notation.
- ithinkso 5y ago>because there is a very real difference from a photon going from the Sun to the Earth, to a photon going from the Sun to Jupiter. Not from the photon's point of view. This is very crucial and it is not because of notation or maths. The real difference is from your point of view. I know it's counter-intuitive but that's different from being useless. Sun->Earth or Sun->Jupiter is a small beer. It is the same for photons from the CMB being recorded. For them, they have been emitted and absorbed at the same instant and experienced no passage of time or distance traveled