# GR aether

1. Nov 16, 2005

### Jonny_trigonometry

General Relativity IS an aether theory. The meaning of this claim is simple, the only way to resolve the problem of forces felt by rotation is to referance space-time as an aether that things move through. This is not the same aether as was thought of in the early 1900's whoose sole purpose was to mediate the propogation of light, but has a small differnace. It doesn't resist mass moving through it at constant velocity, but does resist matter moving through it at changing velocities. Newton argued that the only way to resolve the forces felt by rotation was to referance each object to an absolute space, but we know better today, and referance an absolute space-time (which can be expressed as absolute, ie. Lorentz invariant). Mach argued that the forces felt by rotating objects arises from all the matter that surrounds them. Rather than referancing matter to space, he referanced matter to matter. Since GR claims that there is no absolute rest, there is no absolute rest frame to referance an object's rotation relative to it, but there is such a thing as absolute space-time, and the use of this idea resolves the "forces felt by a rotating object" problem. To get even more in depth, space-time is affected by the presence of matter, and so there will be a configuration of matter that makes space-time rotate in some local area in the universe relative to some other local area. This forces us to claim that the "forces felt by a rotating object" problem is resolved by GR in a hybrid of Mach's and Newton's resolution, that only in a local neighborhood, space-time is absolute and can be referanced to determine the rotation of a body in that local space, but it is determined by the local effect of matter on that local space. Is this an acceptable argument?

going further: SR states that light emitted by a moving body moves independantly of the object moving through space. It still looks like it's moving through space at c when measured from a moving body, but that's because the moving body is lorentz transformed relative to the absolute space-time which is determined by the local bodies in the area. We can tell something is moving relative to us because of the local matter around us, when you see a car drive by, it is moving relative to you, but more importantly, it feels accalarations when it changes velocity, not you. Therefore there is a local absolute space-time that you are in, determined by the majority of the matter around you, and things that accelerate linearly or rotate relative to that aether feel forces internally (as long as thier mass is miniscule relative to the local mass determining the configuration of local space-time). Photons move independantly of the speed of the car moving on a highway, they move at c through absolute space-time, and the car is lorentz transformed relative to local absolute space-time. So in this respect, we can go back to the early 1900's and say that light does travel through an aether, the local absolute space-time, which is determined by the majority of the local mass. In a way, gravity is the aether of light. It makes me wonder, if there is no local gravity (theoretically, no situation like this can exist in the universe), can light travel locally?

Last edited: Nov 16, 2005
2. Nov 18, 2005

### pervect

Staff Emeritus
Rather than to say that GR is an "aether theory", or to say that "space is absolute", I prefer to say that acceleration is absolute and velocity is relative.

I think this is more precise, and less likely to be misinterpreted as a throwback to some pre-relativitic ideas.

Other than this issue of preferred wording, I *think* I for the most part agree with what you've written.

Rotation is a form of acceleration (because of centrifugal and coriolis accelerations) - thus rotation is absolute, too.

Another way of saying the same thing is that we can build instruments to measure linear acceleration (accelerometers) and rotation (gyroscopes or laser gyroscopes) without reference to any other body, (relative to "space", if you prefer), but we can only measure the relative velocity of one body with reference to another (we can't measure the velocity of a body with respect to "space").

Another subtle point which I think you've mentioned - in Newtonian theories, the fixed stars define a coordinate system which is non-rotating for all observers. In GR, observers near a rotating black hole will observe that the fixed stars are not quite fixed. Gravity probe B will be testing this "frame-dragging" result of GR.

3. Nov 18, 2005

### turbo

This was one of Einstein's most compelling arguments for the existence of a real ether with dynamical properties (see Saunder's translation of Einstein's 1924 paper "On the Ether" - chapter 1 of "The Philosopy of Vacuum")

The referencing of a body to all the other massive bodies in the universe was a clever kludge by Mach to avoid appealing to an ether. It implied instantaneous action-at-a-distance, however, which Einstein forcefully rejected in the 1924 paper referenced above, and also in his 1920 address upon accepting the appointment to Extraordinary Professor at the U. of Leyden.

Perfectly acceptable. Inertia and gravitation are the result of the interaction of matter with the GR ether (space-time, vacuum, etc) in which it is embedded. These forces are emergent and are not fundamental or attributable to the matter absent the ether in which it resides. Centrifugal forces cannot arise unless the rotating body rotates with respect to something real AND local.

Yes. The properties of the local ether are determined by the masses embedded in it. If this is true, we should be able to measure the refractive index of the vacuum, and observe that light travels more slowly near a massive body than farther away, where the vacuum is less densified. This has been confirmed by the Pioneer anomaly. EM from the probes returned faster than expected the further they got from the Sun. If we demand that the speed of light in a vacuum is absolute, we would interpret this to mean that both probes are slowing down (unexplained Sunward acceleration) in a very smooth coordinated fashion. Many ideas have been floated to explain this acceleration, each with problems. The simpler explanation is that the probes are moving normally, and that light traverses the vacuum faster where the vacuum is less-densified (farther from the Sun). Thus the shortened EM return times are a direct measurement of the refractive index of the ether of the Solar system, which by extension quantifies the density of the ether. Look up the Scharnhorst effect for a similar example. Scharnhorst proposed to test this effect between the plates of a Casimir device, where the quantum vacuum is rarified by the mechanical exclusion of some wavelengths of the zero-point field. Instead, Pioneer beat him to it, with two laboratory experiements with baselines the radius of our Solar system.

Here is where you lose me. Gravity is an emergent force, resulting from the interaction of bodies of matter with the ether in which they are embedded (think of the quantum vacuum with it's sea of virtual-particle pairs as the GR ether, and refer to Sakharov's statements regarding inertia and gravitation and how they arise from matter's interaction with the quantuum vacuum fields).

Gravity itself is not the ether, but is an emergent force resulting from matter's interaction with the local ether. Light does not need a gravitational field through which to travel - it needs an electromagnetic field through which to travel, and the EM field of the vacuum (Zero-point energy field) fills the bill. With this one clarification, I believe your GR ether model is on firm ground.

With this model, you can interpret gravitational lensing as a purely optical effect - EM waves being refracted by traversing paths through space-time (ether) of varying density. If you follow this path, you will soon consider that light must inevitably lose energy through its encounters with the ether, and will be redshifted in proportion to the average density of the ether it traverses multiplied by the length of the light path. This is a slippery slope that leads ultimately to the rejection of the interpretation of the Hubble distance/redshift relationship as being due to cosmological expansion. Since this redshift= expansion concept is what motivated the Big Bang model in the first place, you should expect lots of resistance from conventional cosmologists to the concept of a GR ether - it has serious implications for the BBT. Some otherwise intelligent and creative physicists will tell you that you are taking Einstein's 1920 Leyden address "too literally", as if Einstein was making a bad joke. When they tell you this (and they will), ask them to read chapter 1 of Saunder's book "The Philosophy of Vacuum", because in that 1924 article (4 years after the Leyden address) Einstein was far more specific and forceful in describing the necessity for a real dynamical ether in GR.

Note: As a nice side-effect, the ether/redshift model neatly trumps Olber's Paradox. EM emitted from objects sufficiently distant from us is redshifted into indetectability. This opens the door for models including an infinite steady-state Universe, if you so desire (I do!).

Last edited: Nov 19, 2005
4. Nov 19, 2005

### Jonny_trigonometry

wow, thanks for the detailed breakdowns of this post. I really appreciate your input Pervect and Turbo-1. I wasn't sure if I wanted to touch the subject of gravity moving at the speed of light, and that is the main reason why absolute space-time is only valid locally, but I guess thats one of the main reasons. I didn't know that this offers the idea of requiring energy to travel in a linear path, and that this could cause red shift... Isn't that a good thing though? How would dark matter fit into this if redshift is caused by the distance traveled in space rather than space-time expanding? It's nice to know that the idea of light not being absolutely constant isn't just my own crack pottery. The way I figure, there is more space that is compactified near a mass than there is further away from it, and time is slower in that space too, so if you could view a light ray as it makes its way through the aether outside all space, you would see it slow down as it moves through space that is more compactified even though it is moving at the same velocity through that space in a local frame in that space. I just gotta ask, is there more space near the center of a black hole than there is in the volume of an average galaxy? At a singularity, could I say that there is more space in that one point than there is in the entire universe, or even claim that there is an equal ammount of space in that point as there is in the universe? (my guess is that anything goes when dealing with these things, since it's kind of like dividing by zero).

5. Oct 18, 2006

### Garth

6. Oct 19, 2006

### yogi

Would you take this so far as to explain the gravitational red shift as being the result of the G field lowering the energy of a photon because it affects the aether density so as to reduce the photon velocity rather than its frequency?

7. Oct 19, 2006

### turbo

I prefer to think of this in terms of classical optics - light as EM waves propagating through transmissive media. If the ether is densified by the presence of embedded matter, it will have a higher refractive index than ether that is very distant from any matter, and light will travel more slowly through it.

http://www.bartleby.com/173/22.html
This is why Einstein spent years trying to determine the nature of the ether (the fabric of space-time) - he knew that the vacuum played a critical role in gravitation, inertia, and light transmission, but was never able to pull it all together. I think that the LQG folks are closer than most.

8. Oct 19, 2006

### yogi

I would tend to agree with your philosophy in many respects - it is however contrary to conventional wisdom. The issue of light bending near a large mass is not resolved - there was a good post by pervect on one of the other topics that addressed this question - in other words - does the velocity of the individual photon slow - or does it remain constant but only deviated.

So you would also attribute the slowing of the photon in a medium such as water or glass as being due to local fields (the refractive index would then be a field effect rather than a consequence of delay due to short term capture of the photon by the atoms of the material - a theory frequently advanced on this website. I have argued this point and usually wind up getting a ration of insult from zapper or the likes of some other person that is convinced the subject is closed. I am surprised this topic has not been moved or shut down by the priests that rule these boards. Discussions involving different theories that both explain the experimental results are too quickly dismissed

Regards

Yogi

Last edited: Oct 19, 2006
9. Oct 20, 2006

### turbo

This may not be a "conventional" view, but you must realize that there are mainstream researchers converging on this topic. For instance, the LQG people are looking at ways to define the small-scale structure of space-time (vacuum). If their approach to quantum gravity is to be dynamical, then the essential qualities of space-time (like the scaling of the fine structure - the "density" of space-time, if you will) must vary in accordance with the matter embedded within it. Only rarely will you encounter someone willing to call LQG an etheric theory, but when Fotini Markopoulou says that she expects GLAST to detect frequency-dependent variations in c, the implications are pretty clear.

Last edited: Oct 20, 2006
10. Oct 20, 2006

### MeJennifer

There is no issue to resolve.

The confusion comes when people try to explain the "bending" of light from some flat space coordinate system perspective, something that is utterly useless and confusing in the explanation of GR.

If you would proverbially sit on the back of a photon you would feel no change of direction or speed.
This observed "bending" is simply an effect of spacetime curvature for an outside misguided observer who thinks that spacetime is flat and who limits his understanding to only allow flat spacetime coordinate systems.

Most of the GR confusion comes when people try to "explain" it with Newtonian thinking. Instead of explaining the principle of geodesic motion and the effect that curved spacetime has on outside observers it is "explained" in terms of objects "accelerating" towards the center of gravity and light "bending" and "slowing down" near gravity, things like that.

Take for instance people "explaining" how light is supposed to slow down in a gravitational field.
Consider locations A and B that are 100 miles apart. Now suppose a car goes straight from A to B at 100 miles per hour then it takes an hour of travel time right? Now suppose another car also goes from A to B but taking a windy road also at 100 miles an hour, then obviously it would tak more than one hour right?
Would it be of any help to explain to someone that the car slowed down?
But that is exactly the "explanation" given for light "slowing down" in a gravitational field!

A photon slowing down in material has nothing to do with GR. A photon does not slow down at all in material, instead the photon gets absorbed and then later another photon gets emitted. Its like you always travel 50 miles per hour but you also make frequent stops, your total speed is less than 50 miles per hour due to the stops.

Last edited: Oct 20, 2006
11. Oct 20, 2006

### yogi

If I understand what turbo is saying - the properties of space depend upon conditioning by matter - and a G field is a component (contributor) to the conditioning - there may be other contributions - but ignoring them for the moment - the conditioning of space has an effect upon the velocity of light. If space is so modified by fields - why would it not be modified by the intense fields within a solid or liquid - a photon traveling through a solid must interact with the atoms - or the fields defined by the atoms - If Turbo's premise has any merit in outer space - why should it not be applicable as a theory that explains local refraction in a solid or liquid - now I am not saying whether it is or is not - what I am saying is that once it is shown that the velocity of light depends upon spatial conditioning - the whole idea that atom(s) temporarily capture photons and later release another one, in just the right direction, at just the right time, to maintain wavefront continuity, is challenged

12. Oct 23, 2006

### turbo

In Einstein's later writings (in particular, see "On the Ether" which is chapter 1 of Saunder's book "The Philosophy of Vacuum") he claimed that inertia and gravitation were not fundamental, but were emergent, arising from matter's interaction with the LOCAL field in which it is embedded - he firmly rejected Machian action-at-a-distance. Few physicists or mathematicians delve into Einstein's later works, preferring to treat the mathematical constructs of GR as if they possess an objective reality. Einstein did not share this viewpoint and tried to press GR to a deeper understanding of the behavior modeled by its equations.