Had the idea , maybe someone can make some sense of it- is it possible that a photon's mass imposes it's speed? I know that photons come in different energies, and that is the main problem with the above idea. When a photon has more energy (and hence mass) it actually becomes smaller, so it should travel more slowly if my vision is correct. . . Is there any characteristic of a photon that doesn't differ with wavelength?? Another idea that struck me is relativistic length-contraction. A photon with a higher energy has a shorter wavelength than one with a lower energy... perhaps the two ideas are related, and perhaps they make sense Now, there seems to be evidence against this. http://www.sciencedaily.com/releases/2009/10/091028153447.htm "This measurement eliminates any approach to a new theory of gravity that predicts a strong energy-dependent change in the speed of light, The photons were launched on their pan-galactic marathon during a short gamma-ray burst, an outpouring of radiation likely generated by the collision of two neutron stars, the densest known objects in the universe. A neutron star is created when a massive star collapses in on itself in an explosion called a supernova. The neutron star forms in the core as matter is compressed to the point where it is typically about 10 miles in diameter, yet contains more mass than our sun. When two such dense objects collide, the energy released in a gamma-ray burst can be millions of times brighter than the entire Milky Way, albeit only briefly. The burst (designated GRB 090510) that sent the two photons on their way lasted 2.1 seconds."
Against my better judgement I'm going to answer this. I'm sure you've had this explained to you in the past but photons don't have a mass. The energy of a photon depends on it's momentum, not it's mass. Just because it's got momentum doesn't mean it's got mass either. The crux of this is that if the photon did have a mass it wouldn't be able to travel at c. This is something we can measure in experiments, and we find that the photon does indeed travel at c, so any notion that the photon has mass is simply wrong.
Yes I have, and it got sent to the cesspool, despite being a very valid question. They call it 'frothy nature of the quantum world' I call it a self imposed speed limit.. whatever Please Register or Log in to view the hidden image! actually the principle on which i base my assumption is quite different than what they propose in their experiment, but it still goes to show all photons move at the same velocity. "if the photon did have a mass it wouldn't be able to travel at c" I have a hunch that lack of oscillation in the direction of travel is another part of it. The TEM wave oscillates only perpendicular to the direction in which it travels.
This is true enough. Massless particles only have two polarisation degrees of freedom, while massive ones have 3 (vector particles anyway). Actually the photon could have a mass, but it would have to be extremely tiny Please Register or Log in to view the hidden image!.
It's lack of mass imposes it's speed. Any massless thing moves at the speed of light. This has been settled for 80 years, why are you asking again about this? This is unrelated (mostly) to what you are asking. General relativity and special relativity, which are proven to be the correct theories describing nature, are based on the assumption that light moves with a constant speed. Now, we know that GR breaks down at some point i.e. inside a black hole), which means that we might suspect that one finds a slight energy dependence in the speed of light. Indeed, you can calculate what that deviation should look like, based on very general considerations. The consequence is that very high energy photons, from very far away, have velocities which are slightly dependent on their energies, and so arrive at slightly different times. If you actually measure such photons, though, you find no such correlation, which means that whatever fundamental theory you have must somehow incorporate the constancy of the speed of light. Such a conclusion says something very deep about the nature of quantum gravity. Somehow, the constancy of the speed of light is NOT an emergent phenomenon---it is a remnant of the fundamental theory. It may seem like it doesn't matter, but this result constrains VERY tightly the types of theories one can consider when doing quantum gravity. In particular, the constancy of the speed of light is the result that one would expect from string theory, but other theories (like loop quantum gravity or causal dynamical triangulations) generically predict that we should see some change in the speed of light. As far as i know, getting that deviation from the speed of light to avoid this experimental constraint is not easy, but I don't follow those fields too closely.
What other massless particles are there? Can you calculate the difference in velocity ? I assert that the more energetic photon did travel more slowly, but only in the immediate vicinity of the originating galaxy and the immediate vicinity of our galaxy.. if you could give me the difference it should be easy to check.
The only other known massless particle is the gluon. The graviton, when it's discovered will also be massless.
I can't calculate it personally, but I will post papers where it's done. Either way, you have to find something which is consistent with experiments thus far, and I'd assume some gravity dependent contribution (like you're talking about) is ruled out by precision GR tests. You can't just postulate that something is different, and then wave your hands and hope that people listen to you. You have to calculate it first, and then show why it's not already ruled out. This latter step is one I'd assume you ignore completely.
Of course you can, its just less likely people will listen to you Please Register or Log in to view the hidden image! I will look for the papers as well, starting with the one which the article is about- http://www.nature.com/nature/journal/vaop/ncurrent/pdf/nature08574.pdf
Why would the "more energetic photon" start travelling more slowly and then speed up? It's still the more energetic photon, isn't it?
Supposedly its got to do with the 'size' of the photon as it travels through 'quantum froth'. I guess what they mean by 'frothy nature of the quantum world' is quantum fluctuations. A less energetic photon has a longer wavelength and so it is bigger. If it was being influenced by these microscopic fluctuations these interactions would be more balanced than those acting on a much smaller photon - where the random nature of the fluctuations would be more noticeable. The probability that the various components of quantum fluctuation cancel themselves out would be lower and so would have more effect... but this is just my understanding. It seems that this shouldn't make much of a difference on enormous scales, where time would still smooth out these effects. Anyhow, I can't tell you how it works, but I've still got my hunch Please Register or Log in to view the hidden image! This is a cool explanation- http://www.nasa.gov/multimedia/nasa...t&_tnimage=398055main_einsteins_comic_100.jpg
The relevant number is \(\xi\), which is defined as \(\xi \equiv M_{QG}/M_{Pl}\) The limit you linked to isn't as good as I thought, with \(\xi \sim 1.2\), but it is the most up to date one. This says that, if there ARE effects due to a changing speed of light, they have to come into play above the planck mass. Naively, one would think that (if the effect were real), the scale should be BELOW the Planck mass. But this is just a naive expectation.
Um.. what exactly are the units ? I'm guessing M is mass while Q .. is .. and G is.. while the Pl might be planck length?
This may not be a good source since they "find no evidence for violation" .. unless they were comparing their results to this hypothesis
\(M_{QG}\) Is the relevant scale of new physics IF violations to c = constant are found. \(M_{Pl}\) is the scale where we typically expect quantum gravity effects to become important. The bound is that \(\frac{M_{QG}}{M_{Pl}} > 1.2\) Suppose there IS new physics which violates c = constant. Then the scale of that new physics is larger than the planck scale. Since we typically expect new physics at the planck scale based on simple dimensional arguments, the fact that the new physics scale (\(M_{QG}\)) is greater than the planck scale seems like it would be hard (though not impossible, I'm sure) to explain otherwise. Now you are neglecting the reference because it disagrees with your belief that the speed of light changes somehow. (Note I chose very carefully the word `belief'.) The paper makes a hypothesis about violations to c = constant, that is consistent with all other observations thusfar. Your hypothesis (that the speed of light changes based on local energy densities) is likely wrong for some obvious reason.
I looked at the paper and Figure 1 makes it very hard to argue that photons travel at different speeds in the whole universe.. perhaps einstein was right and light does always moves at c. The fact that the peaks line up very neatly almost rule out mere chance. So if there is some kind of Lorentz violation it must be localized around energy densities - ones that would be found around our universe and around the originating universe - with a whole lot of smooth sailing in between. "Now you are neglecting the reference because it disagrees with your belief that the speed of light changes somehow. (Note I chose very carefully the word `belief'.)" It is the point of their study that such violations do not occur, so they have a very good reason to adhere to the school of thought that would agree with them. This school is the dominant one and it surely has plenty of publications in it. Your counterargument could be that the papers they are quoting are the very first papers that hypothesized the 'energy-dependent change in the speed of light'. Otherwise they could simply be rebukes of this hypothesis. I don't know and I don't feel like digging. Is this effect hypothesized to be related to quantum fluctuations?
