russ_watters wrote(regarding Einstein's choices re. MM):

I cannot get into his head. I can only go by what his biographer said. In any case, the point is he had choices and made one of at least 2 valid choices.


The aether has not been disproven, and is coming back: dark matter, dark energy, space foam, granularity of space, quintessence, etc. (Going back to Einstein see below for Tegmark).

The dogma was helio vs. geocentrism. I showed quotes of a number of scientists who out of hand rejected even the possibility of geocentrism. This is not a proof, simply an illustration.

Plausibility by what criteria? Is the universe as big as you believe? How do you know? Is there controversy re. redshifts (yes). We cannot see beyond the sphere, and though Tegmark's belief is plausible relative (used loosely) to currently held theories, it is not porven. A simple example is the belief that the stars appear to rotate becuase the earth is rotating. If Geocentrism turns out to be correct, this will have turned out to be (nice grammar) one of those statements of faith in a theory, which appeared correct, but was not. The observation will have not changed.

By aether, people are usually referring to the luminiferous aether that was invoked so that light waves would have something to propagate through. (Hence the M&M experiment, etc.) I don't see any of the above being an indication that a luminiferous aether is coming back.

Anybody else, any thoughts?

Earthquakes, like the recent one, are often claimed to be a disproof of geocentrism.

The usual explanation for earthquakes is that they are due to to stress build-up along cracks in the Earth. When the stress reaches breaking point, the earthquake happens and the spin of the Earth is affected.

But by the Advanced Potential model and Einstein, cause and effect can be reversed, and earthquakes can be said to be due to stresses and strains within the rotating universe which causes a corresponding strain build-up in the earth.

Once the strain snaps, the Earth slips and the earthquake happens (usually along a weak point like a fault), and the universe adjusts its rotation rate accordingly!

I have this bridge that is the center of the universe. It happens to span the East River. I'd be glad to part with it for a reasonable sum.

Just think: YOU could own the center of the universe!

Welcome to the BABB, BTW.

PS: Once you reopen the bridge, expect a lot of Canes traffic, since word's gotten out that there's a tree growing in Brooklyn.

__________________
A person's name, or a mark representing it, as signed personally or by deputy, as in subscribing a letter or other document.

Agreed.
Absolutely not. The two scenarios given have the washing thrown to the edge by centrifugal force. Neither has a centrifugal force induced on a stationery object by virtue of the objects spinning around it, which is what would be required to make it Machian in the sense they argue for, and which has only ever been acheived theoretically with the Lense Thirring effect, which is a strictly GR result which has been shown to exist, and is currently being tested by gravity probe B. In short, there is no existant theory that can explain the apparent centrifugal forces on a stationary earth except GR, which says that there is no meaning to the question "what is the real stationary center of the universe". As usual, the Geocentric claim is a misrepresentation of convential science.

Yes, but these corresponding Geocentrists tell the same lies about conventional physics, like the one about conservation of angular momentum means that everything must spin the same way, for instance. If they are ever going to be taken seriously by anybody other than just their ignorant followers then they must, at the very least , honestly represent the theories they oppose rather than continue to construct and share ridiculous strawmen with which to bamboozle their ignorant followers.

__________________
There are 10 types of people in the world. Those who understand ternary, those who don't, and those waiting for a bus.
If logic doesn't work, then surely it does.

Cause and effect cannot be reversed in relativity. If you think differently give a link to mainstream physicist's paper which says it can.

Even if the stress on the earth could be described as stresses in the universe, when the earth does "snap" how does this information get communicated to the entire universe instantaneously without violating relativity?

__________________
There are 10 types of people in the world. Those who understand ternary, those who don't, and those waiting for a bus.
If logic doesn't work, then surely it does.

This is not the same thing as the classical luminiferous aether. Spacetime is not a propagating medium for light.

Actually, the controversy wrt redshift-distance relation is minimal and fringe.

The coordinate dependent observations of Earth being a non-inertial reference frame are very difficult to ignore. Although it is possible to transform any reference frame into a frame following a geodesic in GR, you don't do that because you aren't in freefall. In other words, the Earth is necessarily, in the context of GR, not the prefered frame. In order for geocentrism to be correct, GR must be entirely incorrect since the prefered mathematics to calculate is to consider frames where accelerations are due only to geometrically depedent formulations (i.e. gravity).

That's a misuse of the term "preferred"--you're using it with two different meanings. There are no preferred frames in general relativity, but scientists often prefer one frame or the other. That's two different forms of preference.

Astronomy says:

Nor is spacetime an aether. GR (and SR) jettisoned aether and posit an absoulte vacuum. It is intresting that GR's postualted absolute vacuum turns out to have a finite electrical resistance (sounds like an aether with some EM interaction not an absolute vacuum). Quantum mechanics, string theory, etc., need an aether. GR and QM are not in agreement. Either both are wrong or one is right.

If there is an aether, then it could be a conduit for light in some manner.

I don't think that they do require an absolute vacuum. For example QED, has SR built into it (even classical EM has SR built into it, as the magnetic field is effectively what you get when you apply a Lorentz boost to electrostatics.)
Why does light need something to act as a conduit for it? An electron doesn't, so why should a photon? People got hung up on an aether because of the wave character of light. When particles exhibit wavelike properties, then why should the photon be singled out for special treatment?

There is a preference in terms of mathematics. It's not just scientists that see this.

The inertial frame is preferred because the mathematics is much simpler.

I'm not saying that it is special, just preferred.

QM does not require an aether at all. This is just plain not true.

But "preferred frame" is referring to physics, not mathematics. General relativity says there is no preferred frame.

Not necessarily. When you are actually doing GR you transfer into the preferred frame to do your calculations (whichever preferred frame that is). Yes, people call it the "preferred" frame.

As I said before, that is two different meanings for the word "preferred"

When general relativity says there is no preferred frame, that does not mean that engineers won't prefer one over the other.

Mainly a wording problem, but I've always heard it said that there is no "absolute" reference frame in relativity -- preference being a personal matter.

ATP is going to killfile me for this, but I think that an inertial frame is preferred over a non-inertial one in GR. Although the laws of physics can be formulated in such that they work in either, in an intertial one the warping of spacetime is due to matter, in a non-inertial one we have to assume a changing gravitational field with no cause - I fire my boosters and I don't move, it's just the whole universe that instantly accelerates towards me and in so doing bends spacetime around me so that I just happen to feel like I'm moving - nah.

__________________
There are 10 types of people in the world. Those who understand ternary, those who don't, and those waiting for a bus.
If logic doesn't work, then surely it does.

Google on +"preferred frame"+"relativity"
Killfile? Naw. I love inertial frames.
Nah?

My point is there are easier frames to use, and they might be personally preferred, but that is a different meaning of the word "preferred" than when it is said that "there are no preferred frames in general relativity." I see where Astronomy is not even familiar with the second usage, but if you go back through the thread, you'll find where other posters have mixed the two usages. That's all I was pointing out.

It's easy to come to erroneous conclusions when you make deductions based upon similar (or in this case identical) words that don't mean the same thing.

I prefer to be precise in language. "Absolute" frame is more precise than "preferred" frame because preference is a personal matter.

Special relativity removed the concept of the aether as a "preferred frame" saying that the aether didn't exist. However, that doesn't get rid of the concept that someone might prefer a reference frame.

Again, this is mostly a wording issue, but it's alright to claim that it is preferable to look at the universe from a reference frame that relies on the most mudane geometrical perspective.



You might clean up the statement a bit and say that general relativity does not physically distinguish between frames.

No, I'm familiar with the usage. I just think it's not a good word to use because it misses the point.

Indeed.

I should point out that "preferred frame" is an aether word and was dispensed of in special relativity as being a statement in the absolute sense. However, SR works for differentially constructed inertial frames meaning that any attempt to look at invariants still has a preference involved. GR does not overthrow this. That's why I claim that a wording of "absolute frame" is more to my liking.

Not much I can do about that. The term "preferred frame," in the sense that you disagree with, appears* in the bible of relativity, Gravitation, by Misner, Thorne, and Wheeler. I don't see any reason to not use it--but I will object when people say general relativity allows preferred frames, rather than saying "personally preferred frames". There's a big difference.

*e.g., p.1083, "In general relativity, the geometry of curved spacetime picks out no preferred coordinate frames", and p.1093, "general relativity and Dicke-Brans-Jordan are conservative theories with no preferred-frame effects." Those are the first two instances referenced in the index.

I've seen people used prefered frame in both senses as really the term is open to disambigution.

The principle of gneral covraiancy states that the laws of nature do not prefer any frame, however this doens't mean that there aren't some frames which will naturally be prefered by us.

milli, you need to be reminded that scientific literature is not dogma. Ad Verecundiams don't cut it, either re published texts or self-referential. Everything is open to question, whether you think so or not. There are no "bibles" in science.

__________________
A person's name, or a mark representing it, as signed personally or by deputy, as in subscribing a letter or other document.

That's my point
In the phrase "naturally be prefered", the "naturally" is disambiguating the "prefered".
No, I don't think so.
This is not an issue of dogma--it's one of usage. I provided a google search that also established usage earlier, but Gravitation should hold some weight.

That nicely illustrates the fact that you do.

Ah, more word games. Now I remember why I left this circular thread some time ago.

__________________
A person's name, or a mark representing it, as signed personally or by deputy, as in subscribing a letter or other document.

I am aware that scientific literature is not dogma

Yes it is a fudge, but clearly there are in many situations frames that we will choose to examine the situation which are much easier to perform calculations in and are more 'intutive' to use.

I wouldn't call it a fudge. It is clear that there are frames which are easier to use--and in almost all cases, we use approximations to the physics even then. But that does not have implications as far as general relativity is concerned.

Both nice example that illustrates my point. The geometry of curved spacetime indeed picks out no preferred coordinate frames. To do that, you have to appeal to other matters (for example, mathematical ease of calculations). And it is true that there are no "preferred-frame" effect in GR or DBJ. The fact is that this is a proof offered by special relativity and is more basic than either of these.

I stand by my contention that it's okay to have a preferred reference frame -- GR allows it. I prefer the frame of the CMB, for example.

It's true that it is something of semantics to argue whether the Earth could be considered a preferred reference frame. I argue that there is no way it can be since it is more complicated from the perspective of ease of mathematical computation, for example. However, it is entirely subjective and some people may prefer more complicated for religious reasons, for example.

And I entirely agree with you there, when we say GR has no preferred frame we don't mean that we cannont have preferences, we mean that fundimentally it is just a choice of convenience, like me measuring distances from my house to the tube stations here in London rather than from yours, or the moon.

But what I still don't get is why you all keep saying that GR has no preferred frame. I agree that GR allows us to describe physics in a frame independant way, and that is pretty mind blowing, but I still don't get how you can say that a frame where all spacetime curvature is a function of matter is just a superficial coordinate change from one where we have to introduce curvature with no related matter. That difference seems quite profound to me.

I think that the interpretation of "all frames being equally good for formulating the laws of physics" has been taken too far. I have never heard a satisfactory answer to the question of what causes the universe to instanly start rotating about my head when I decide to roll over, and therefore cause it to do do, if I insist that my head is stationary. That is the implication of the statement that all frames are equally valid.

__________________
There are 10 types of people in the world. Those who understand ternary, those who don't, and those waiting for a bus.
If logic doesn't work, then surely it does.

Proof of what?
As I said before, that's using the term "preferred" in a way different than it is normally used in the context of general relativity. Potentially confusing--whether you like the term or not, its use has been established.
I argue, in the context of general relativity, the ECEF (earth centered earth fixed) frame cannot be considered a preferred frame either--but only because there are no preferred frames in general relativity. It has nothing to do with semantics or personal preferences.
"You all" meaning Misner, Thorne, and Wheeler? Or just me?

The reason I say it is because they do. I'm still working on convincing myself.