Faster than light – but not with spaceships, particles, or transverse wave signals may be possible if spacetime is similar to a slightly viscous fluid. Pressure waves in general relativity may move faster than light.
There have been a few papers written over the years modelling Einstein’s ether as an elastic solid. I have been reading these papers:
So – lots of stuff about the ether as a solid.
A few problems with this approach – you can see one paper coming up with Young’s modulus varying with frequency (McDonald), and others struggling with how to even support transverse waves in this elastic medium. A key measure of a substance is its Poisson’s ratio – which is an elasticity measure. The semi consensus is that this ratio is 1 for the ether, which is not like any normal material (but OK spacetime is not a normal material!).
One thing about materials is that they in general support two kinds of waves ‘P-waves’ (pressure waves) and ‘S-waves’ (shear waves). Choosing Poisson’s ratio as 1 leads to P-waves having a speed of 0! Which is ‘required’ as everyone knows that p-waves can’t exist in general relativity. I agree that p-waves can’t be made in GR using normal matter moving around, but see this paper http://arxiv.org/abs/astro-ph/0309448 to get an idea of how one might generate monopole wave action.
There seems to be a lot of hand waving going on in these papers about thin plates, absolute length scales (Planck length chosen), and more just to get things to work out.
Since I’m an optimist at heart, I decided to look at this from another direction. What if Einstein’s ether was more like a fluid? Fluids have Poisson’s ratio of about 1/2, and only support shear waves if there is viscosity to the fluid. So lets let our fluid have a Poission’s ratio of just shy of 0.5, say one part in 10^14 away from 0.5, and a see what happens.
Here is what happens: Faster than light effects – the fluid of spacetime is extremely incompressible, and has a very small Young’s modulus.
I’ll quote a section of the Tenev-Horstemeyer paper here:
Run the calculations for µ and M, we get µ = Y/3 and M = 10^14 times Y, so the pressure waves in this fluid ether would travel at 10^7 (square root) times faster than c. (There is no experiment or theory describing the viscosity of Einsteins ether at this point, the 10^14 delta is for illustration only).
This huge pressure wave speed would not be seen in experiments as the paragraph points out – all known waves that propagate in real space are transverse. I think that the paper makes the mistake of assuming that because all we have measured are transverse waves, that those are the only kind that exist! Pressure waves in general relativity would be hard to generate it would seem, since one would have to pulsate spacetime.
So how would we generate these monopole waves? If we simply shoot matter on and off a planet, we will generate ‘dragged along’ monopole waves, which would travel at light speed (or less) with the matter.
One way to make superluminal p-waves is of course with the physicists favourite friend, the magic wand. Magic wands have been used in theoretical physics to create extra dimensions, multi-universes, etc. Here I only invoke it to make matter disappear, in a periodic pattern. For a concrete example, assume fundamental particles are varying in mass (imagine some worm hole mechanism) at their Compton frequency. Then we would have these pressure waves at fantastic velocity around them, exchanging information with their surroundings, in a de -Broglie or Madelung way. This would help quantum mechanics emerge from spacetime, something I have been searching for over several decades.
I don’t think that this is a possible idea simply because I wish there to be a way to communicate at velocities above c, or that it helps with a realistic model for quantum mechanics, I also think its a simpler way to look at Einstein’s ether than with the ‘closely packed’ layers of manifolds that the solid models quoted above mostly assume.
It seems that this bulk modulus pressure wave velocity being orders of magnitude faster than c might mean that there is a preferred frame for p-wave speed in the Universe. Lorentez transformations and the constancy of the speed of light measurements would presumably stay the same as they are now, as this fluid would simply be a way to generate the Einstein field equations.
Could a bulk modulus and Poisson’s ratio allowing for super-luminal p-waves replace inflation? One of the big reasons for inflation is that the universe is too smooth – given the paltry speed of light, places far from each other should have different temperatures, etc. https://www.newscientist.com/term/cosmic-inflation/
There are many people who think inflation is a silly crutch.
Here is a new story in Scientific American about ‘strange results’ from Nanograv. Could these be signs of longitudinal gravitational waves? The arXiv papers referenced point out that the observed signal has no quadropole signature, which is part of the ‘weird’ results. https://www.scientificamerican.com/article/galaxy-size-gravitational-wave-detector-hints-at-exotic-physics/
Does Pizzella’s experiment violate causality?
The idea about electromagnetic interactions being
composed of both instantaneous (bound) and retarded (radiation) parts is not new. It was
repeatedly expressed theoretically [3, 4, 5], and electromagnetic superluminal effects were seen
in experiments as well [6, 7, 8].