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The hard part for physicists to accept is that the theory requires the speed of light to change. It would be interesting to see how the theory behind the Unruh

by adekok 11y ago

The hard part for physicists to accept is that the theory requires the speed of light to change. It would be interesting to see how the theory behind the Unruh radiation works with "The quantum vacuum as the origin of the speed of light" (http://arxiv.org/abs/1302.6165# http://arxiv.org/abs/1302.6165#) Or also MOND (https://en.wikipedia.org/wiki/Modified_Newtonian_dynamics https://en.wikipedia.org/wiki/Modified_Newtonian_dynamics) Which also has predictions based on very low accelerations. It seems like the theories could be related. (says an ex Nuclear physicist who's now doing computers).

daeken 11y ago
> The hard part for physicists to accept is that the theory requires the speed of light to change. I'm a complete layman here, so I don't understand how the link you shared says that the speed of light is changing; it seems more like a change in the way we define the speed of light. Is that right? If the actual speed of light is to change, how is that possible? We've experimentally verified it up one side and down the other, so this seems like a huuuuuge discovery.
- leblancfg 11y ago
  A large part of theoretical physics is getting to grips with the terminology -- not that you should imply that I'm in any way an expert. I think I'd go with the wording "it seems more like a change in the way we understand the speed of light". From that, it implies that, yes, its definition would change, but it's something much bigger! So yes, this seems like a huge discovery. Pretty much all of our understanding of relativity is based on the fact that c is, well, immutable. Changing the way we understand c means that we'll need to completely change the way we grok the last century of theoretical physics.
- lisivka 11y ago
  Sagnac effect shows that speed of light is not constant and can be changed. [1] http://arxiv.org/pdf/physics/0609222.pdf http://arxiv.org/pdf/physics/0609222.pdf
- empath75 11y ago
  So there's c, which is essentially a conversion factor between space and time, and also happens to be the speed at which massless particles move. If photons happen to not be massless, the speed of light might change, though 'c' wouldn't have to.
awinter-py 11y ago
doesn't refraction also require the speed of light to change? I'm guessing you mean something subtler.
- danbruc 11y ago
  In case of refraction it is a macroscopic illusion. If you look closely enough, you will see photons traveling at the speed of light between atoms, getting absorbed by atoms and reemitted later. The macroscopic speed of light is just the result of absorption and emission probabilities and the microscopic geometry of the material. But there is another layer below but I am less sure about that, it may be (slightly) wrong. In quantum electro dynamics photon take, figuratively spoken, all possible paths from source to detector, also paths that require going slower and faster than the speed of light. All those possible paths interfere with each other and the net result is that the photon seems to move with the speed of light with very high probability. But really take that with a large grain of salt.
  - cperciva 11y ago
    If you look closely enough, you will see photons traveling at the speed of light between atoms, getting absorbed by atoms and reemitted later. That's a story we tell kids who ask too many awkward questions. If it were true we would see sharp changes in the observed speed of light at wavelengths depending on the absorption spectrum of the material in question. My understanding is that the real answer involves photons gaining inertia via coupling with particles in the material they are passing through (cf. Higgs) ... but I'm probably mangling that explanation horribly.
    - danbruc 11y ago
      I shouldn't have written »absorbed by atoms and reemitted later«, that is really a different thing, interacting with the atoms is better. The superposition of all possible paths and interactions results in a wave function that effectively travels slower than the speed of light.
    - wnoise 11y ago

by adekok 11y ago

daeken 11y ago

> The hard part for physicists to accept is that the theory requires the speed of light to change. I'm a complete layman here, so I don't understand how the link you shared says that the speed of light is changing; it seems more like a change in the way we define the speed of light. Is that right? If the actual speed of light is to change, how is that possible? We've experimentally verified it up one side and down the other, so this seems like a huuuuuge discovery.

leblancfg 11y ago
A large part of theoretical physics is getting to grips with the terminology -- not that you should imply that I'm in any way an expert. I think I'd go with the wording "it seems more like a change in the way we understand the speed of light". From that, it implies that, yes, its definition would change, but it's something much bigger! So yes, this seems like a huge discovery. Pretty much all of our understanding of relativity is based on the fact that c is, well, immutable. Changing the way we understand c means that we'll need to completely change the way we grok the last century of theoretical physics.
lisivka 11y ago
Sagnac effect shows that speed of light is not constant and can be changed. [1] http://arxiv.org/pdf/physics/0609222.pdf http://arxiv.org/pdf/physics/0609222.pdf
empath75 11y ago
So there's c, which is essentially a conversion factor between space and time, and also happens to be the speed at which massless particles move. If photons happen to not be massless, the speed of light might change, though 'c' wouldn't have to.

awinter-py 11y ago

doesn't refraction also require the speed of light to change? I'm guessing you mean something subtler.

danbruc 11y ago
In case of refraction it is a macroscopic illusion. If you look closely enough, you will see photons traveling at the speed of light between atoms, getting absorbed by atoms and reemitted later. The macroscopic speed of light is just the result of absorption and emission probabilities and the microscopic geometry of the material. But there is another layer below but I am less sure about that, it may be (slightly) wrong. In quantum electro dynamics photon take, figuratively spoken, all possible paths from source to detector, also paths that require going slower and faster than the speed of light. All those possible paths interfere with each other and the net result is that the photon seems to move with the speed of light with very high probability. But really take that with a large grain of salt.
- cperciva 11y ago
  If you look closely enough, you will see photons traveling at the speed of light between atoms, getting absorbed by atoms and reemitted later. That's a story we tell kids who ask too many awkward questions. If it were true we would see sharp changes in the observed speed of light at wavelengths depending on the absorption spectrum of the material in question. My understanding is that the real answer involves photons gaining inertia via coupling with particles in the material they are passing through (cf. Higgs) ... but I'm probably mangling that explanation horribly.
  - danbruc 11y ago
    I shouldn't have written »absorbed by atoms and reemitted later«, that is really a different thing, interacting with the atoms is better. The superposition of all possible paths and interactions results in a wave function that effectively travels slower than the speed of light.
  - wnoise 11y ago