I can't imagine such a world. Would we still be able to use our eyes ? Light is such a fundamental part of our reality that reality without it seems impossible. Not a line of thought I wish to pursue.suppose,there is an world where information can travel only through the sound, light still exist, but can not carry any information.
but here we calculating all masses and other things with the help of 'relativity with speed of light'. if information can not travel with 'c' then what are the transformation equations?The question as posed is very difficult to answer. Light carries information and there are tons of experiments that show it or that use that fact. We would have to go back to each of those experiments, change the results and then come up with a new theory that explains all of those imagined results.
Here is a different question which would not contradict any previous experiments, but should get to your underlying concern:
The mass of the photon is believed to be zero, but that is something that cannot be established experimentally. All you can do is put an upper bound on the mass. So, let's say that the next experiment to measure the mass of a photon detects a small (consistent with previous experiments) but non zero mass? Then light would not travel at c nor would the information carried by light.
Is that a suitable substitute?
The Lorentz transform would remain unchanged. The invariant speed c is a property of spacetime, not just a property of light. In that sense calling c "the speed of light" is a historical misnomer.if information can not travel with 'c' then what are the transformation equations?
i think the limitation of 'energy range' can be explain asI understand the question sanjibghosh, and the answer is yes, as long as the sublight speed barrier (speed of sound in your example) is a true upper bound on speed, as opposed to an approximate upper bound i.e. only holds or some range of energies.
Even in the latter case we have the mainstream treatment of phonons on a lattice which will satisfy approximate lorentz symmetry, where the speed of light is literally replaced with the speed of sound in the material. This can be found in most modern condensed matter books.
I'm very happy with sanjibghoshian(!!!.. ) transformation.but i do not understand clearly,so can you tell me some sources where it was discussed.
I am not sure that Dale fully grasped one aspect of the question. It's no surprise because as I said, it is difficult to conceive of a situation where the maximum speed of information is lower than the speed of light.There are two main formulations of SR: the traditional two-postulate formulation and the modern Minkowski geometry formulation. In the two-postulate formulation all that would be necessary to adapt it is that the second postulate would need to refer to "the invariant speed" rather than to "the speed of light". For the Minkowski geometric formulation all that would be needed is to draw the worldlines of light pulses at a less than a 45 degree angle. No changes to the Lorentz transform would be necessary for either formulation.
I have no problem concieving of an information-less tachyon. In fact it is easier than one that carries information since you avoid all of the nasty causality problems. However, it is contrary to an enormous amount of evidence to consider that light does not carry information, which is why I re-posed the question as I did. I think my re-framing of the question is physically reasonable and still addresses his root concern.I am not sure that Dale fully grasped one aspect of the question. It's no surprise because as I said, it is difficult to conceive of a situation where the maximum speed of information is lower than the speed of light.
The invariant speed is the speed which is the same in all inertial reference frames. I.e. it is the speed "c" in the Lorentz transform. The invariant speed is a feature of spacetime, and is not directly a feature of either light or information. The invariant speed is equal to the speed at which light propagates to current experimental precision, but future experiments could concievably determine that light propagates at a slightly different speed without any impact on the Lorentz transform.What is "the invariant speed"? I'm not being silly (I hope) but pointing out that the definition in terms of the original question will have to be such that light can go faster than it. For the Minkowski space explanation, remember again that in the original question information travels at less than the speed of light, not light slower than the speed of information.