General Relativity (and Einstein) - needs an ether? or not?

[Celeritas]

These are but two of hundreds if not thousands of such websites claiming some kind of flaw or error in SR or GR or the MMx. It would likely take a dozen people working full-time to debunk them - some are trivially easy to debunk, others require the investment of a lot of time and effort (mostly to 'get inside the head' of the author). Physicists at universities throughout the world get unsolicited emails, letters, and calls by the dozen, every year, from folk variously referencing this sort of material (curious, belligerent, respectful, angry, ... the emotions that accompany these run the whole gamut).

If any of these folk have actually found something, then by all means encourage them to write a paper and submit for publication in a relevant peer-reviewed journal (in fact a good, quick test of the likely quality of these sites you can find so easily is whether the author has published papers relevant to the claim, and provides links to such papers; if not, then it's probably not worth your time reading any further).

This kind of response constantly confuses me but, everyone is entitled to their opinion. It seems as if the status quo of scientific thought is in perpetual momentum towards its established doctrines with blinders and every claim outside of that realm takes "too much time" or, someone is angry et al. The author DID submit the article for publication and it was rejected. That does not = wrong. Your second paragraph seems entirely jaded as the submission of papers to "relevant peer-reviewd journals" would have the effect of imposing a guilty or innocent verdict from an obviously tainted jury pool. This link was on this BAUT forum website and its filled with Aether related material for purchase. I guess its okay to make $$ off of scientific nonsense while we drum it into obscurity??

So to the point: No. There is no ether needed in GR nor SR. Physics deals with the components of the universe, the forces and results of said forces as they interact upon one another and said components. The end.

Do excuse the the thread irrelavent links as i have not yet mastered the art of topic specitivity. However the link realted to your above muse I thought relevant owing to what i felt was the need, to some degree, of showing that there may have been an attempt to verify the existance of an Aether before discussing it. I think its called 'Balance'?

Would all such attempts to show some degree of scientific inquiry into those things which run contrary to the ruling consensus meet with such condemnation?

I would appreciate any Aether relevant links that you, or the mainstream, think would be ... 'justified' in this regard enabling us to be about the business of debating something valid. In other words:

If there exist no peer reviewed relevant Aether Theories to the satisfaction of sceintific mainstream why posit the question that heads the thread? For without same this thread ponders something which, to science, does not exist.

[Nereid]

This kind of response constantly confuses me but, everyone is entitled to their opinion.

Looks like we have some common ground then (I'm confused about your confusion). Likely this will take us OT, and so it may be a good idea to open a new thread (in General Science, perhaps).

It seems as if the status quo of scientific thought is in perpetual momentum towards its established doctrines with blinders

Well, as you say, everyone is entitled to their opinion.

Mine happens to be something like the words after "if" are almost certainly guarranteed to generate a very spirited response from nearly every professional scientist who takes the trouble to read it (unless, that is, they've grown jaded with having tried to deal with such apparent ignorance).

But let's not get emotional about this, how about we examine the claim, and see what merits it has, shall we?

and every claim outside of that realm takes "too much time" or, someone is angry et al. The author DID submit the article for publication.

Which one (you provided three links - the third relates to material already the subject of several published papers)?

Your paragraph sentence seems entirely jaded as the submission of papers to "relevant peer-reviewd journals" would have the effect of imposing a guilty or innocent verdict from an obviously tainted jury pool.

As has been said many times before, the scientific process is not an 'American Idol' popularity contest.

Nor is it a "we assume all ideas are equal until proven otherwise". The peer-review process for technical publications is what it is. Is there a better way to 'do' science? By all means, let's hear some suggestions!

This link was on this BAUT forum website and its filled with Aether related material for purchase. I guess its okay to make $$ off of scientific nonsense while we drum it into obscurity??

Would you mind saying a bit more about this please? Was it an ad? Or something else?

So to the point: No. There is no ether needed in GR nor SR. Physics deals with the components of the universe, the forces and results of said forces as they interact upon one another and said components. The end.

Do excuse the the thread irrelavent links as i have not yet mastered the art of topic specitivity. However the link realted to your above muse I thought relevant owing to what i felt was the need, to some degree, of showing that there may have been an attempt to verify the existance of an Aether before discussing it. I think its called 'Balance'?

No worries; this is a discussion forum ... if posts get OT, we'll find a way to continue the discussion somewhere else.

For any reader who may be still confused, I started this thread with the express purpose of having a discussion on whether some kind of ether (or aether) is part of Einstein's GR (not SR, there's nothing to discuss there - three is no ether), and also what Einstein himself felt about ethers and GR.

This thread was explicitly limited (per my intent) to that narrow scope. Whether there is (or is not) an 'ether' (or 'aether'), in any other theory, or supported by any observations or experiments may be interesting, but out of scope of this thread.

Would all such attempts to show some degree of scientific inquiry into those things which run contrary to the ruling consensus meet with such condemnation?

Of course not. And the vast literature on topics like this provide a strong case that, in practice, research into the nature of space and time is being pursued aggressively (as it has since before Einstein published his Theory of General Relativity).

Oh, and I'm not sure what the 'ruling' (as in 'ruling consensus') means - could you clarify please?

I would appreciate any Aether relevant links that you, or the mainstream, think would be ... 'justified' in this regard enabling us to be about the business of debating something valid. In other words:

If there exist no peer reviewed relevant Aether Theories to the satisfaction of sceintific mainstream why posit the question that heads the thread? For without same this thread ponders something which, to science, does not exist.

Already addressed - perhaps the OP was not worded clearly enough?

Or perhaps not; a review paper on "Aether Theories" would have to have, near its beginning, a definition of terms, and a scope statement (something like 'in this paper, we will limit discussion to the following: {list}'). One aspect that I am interested to get into the open is the extent to which there is confusion over the core term ('ether' or 'aether') - as has already been pointed out, LQG may very well be 'an (a)ether theory', or it may be the antithesis of such a theory. Sure, few (if any) authors of LQG papers would use the term, but with a different perspective?

[Ken G]

Yes, definition is crucial. From my point of view, an ether exists if and only if there are two different velocities that appear in experimental results involving two particles in relative motion-- the relative speed of the particles, and some other speed that may be interpreted as the relative speed of the "ether". If there is only one relevant speed, the relative speed of the particles, that may explain all experimental results, then there is no ether. Note that there may still be (and are) other parameters that matter, such as the temperature of the vacuum and its gravitational state (i.e., curvature), which may be attributable to the space. We already know this. But if not a velocity, then how is there an ether? The other numbers, including temperature and gravity, can be attributed to the space itself as a kind of intermediary, or shortcut, for describing deeper processes involving virtual particles in the vacuum. Those deeper processes exist, we already know that too, and if you want you may call it an ether. But to make connection with the traditional meaning of the word, you would have to have a velocity appear in there too. We are free to adopt any definition we like, I've offered mine. Other posters in this thread might want to offer the definition they are using, or progress cannot continue.

[Sam5]

Einstein was being consistent with his creation. What GR has to say about this is that the motion of an astronomical body creates a distortion in the curvature of spacetime, which moves outward in all directions at the speed of light. Note, however, that the propagation of a distortion in the curvature of spacetime IS NOT the same thing as the propagation of a gravitational force, or even less so, the propagation of a gravitational wave. For the latter to occur, the astronomical body we are talking about would have to radiate it.

As far as I can tell, there are two ways to look at this, but I don’t know which one is correct.

For the “radiated” way, let’s consider a small magnet and let’s say the magnet “radiates” a magnetic field that follows the magnet through space. So, we move the small magnet around our room and when it comes close to small pieces of iron, they move, in reaction to the magnetic field that is moving through the room with the magnet.

For the “distorted space” way of thinking about a field, we can place a small round ball under a tight smooth bed sheet. That causes a lump in the bed sheet and the bump extends out a few inches. Then we move the ball and the lump moves under the sheet, but without the sheet moving (except up and down with the lump). So this would illustrate a “non-radiated” field which is a “distortion” in “space”. This “distortion” moves with the ball but the ball is not “radiating” the distortion.

So regarding gravity (or a magnetic or electric field) which is it? Are the fields “radiated” by the object, or do all three fields represent three different kinds of “distortion” of space? Personally, I don’t know.

[Ken G]

I think the reason you don't know is that nobody does. It sounds like you are talking about uniting GR (so words like "curvature" and "metrics") with a field theory for gravity (so words like "graviton"), which in turn would be conducive to treatments like quantum mechanics. So you are talking about uniting gravity and quantum mechanics, and this has never been done.

[turbo-1]

I think the reason you don't know is that nobody does. It sounds like you are talking about uniting GR (so words like "curvature" and "metrics") with a field theory for gravity (so words like "graviton"), which in turn would be conducive to treatments like quantum mechanics. So you are talking about uniting gravity and quantum mechanics, and this has never been done.

It has never been done, but it could be possible if the GR ether is envisioned as a polarizable medium occupying Euclidean space. This would remove the necessity for spacetime curvature, leading to a gravitational theory that could be compatible with quantum mechanics.

[RussT]

It sounds like Einstein's concept of an aether was quite a bit different than the conventional view before Michelson-Morley. But you won't get dark matter from it, the properties of dark matter cannot be attributed to space itself (or we would not need both dark matter and dark energy).

Let me try this a slightly different way.

Ken, would you then say that this is an impossibility?

NARRATOR: Randall tried to calculate how gravity could leak from our membrane Universe into empty space, but she couldn't make it work. Then she heard the theory that there might be another membrane in the eleventh dimension. Now she had a really strange thought. What if gravity wasn't leaking from our Universe but to it? What if it came from that other universe? On that membrane, or brane, gravity would be as strong as the other forces, but by the time it reached us it would only be a faint signal. Now when she reworked her calculations everything fitted exactly. End.

[Ken G]

All I can say is it hasn't worked so far, but some think that it will work someday, using ideas similar to the last two posts. I'll wait and see.

[Celestial Mechanic]

The Ether Dialogues (Part One--You Spell AEther, I Spell Ether, Let's Call the Whole Thing Off)

CM: "Thank you for stopping by again!"

BH: "What's on your mind this time?"

CM: "Well, this time it's ether."

DB: "I'll just have coffee, thank you."

CM: "No, not that kind!" "I mean the kind that supports waves, like light waves."

BH: "But that's so-oo 19th century, surely no one believes in that anymore!"

CM: "No, a lot of people still do. Our daily experiences with waves conditions us this way. I mean, look at some of the waves we experience daily: sound waves in air, surface waves on water, or seismic waves (hopefully not daily!) in earth. So why not light and matter?"

DB: "Well, no experiment has ever been able to detect this 'luminiferous ether'. Michelson-Morley came up empty-handed, attempts to save appearances by 'dragging' or 'entraining' the ether near the Earth are contradicted by stellar aberration. clj4 can catalog all the various proposals for preserving ether and all the experiments that have shot each and every one of them down. You're not backsliding, are you?"

CM: "Moi? Never! In fact, my view is rather radical. Remember my dialogues with Virginia and sometimes Jimmy K. concerning the existence of the universe?"

BH: "Very entertaining, yes."

CM: "Well, I'm serious, I do think that the Universe is just one big, possibly infinite, Feynman diagram. In this diagram there are only edges which represent particles and nodes which represent interactions where particles are destroyed and created. This graph does not exist in some space; that's just a limitation of our imagination. Only the graph exists. And all of the various particles need no assistance from some medium in order to propagate from their creation event to their destruction event."

BH: "But what about spacetime? Doesn't that exist?"

CM: "Strictly speaking, no. What does exist are properties or attributes of the particles, such as four-momentum, angular momentum, 'charges' of various sorts. And it is possible to assign coordinates to the events. Of course we can't assign them arbitrarily; the possible coordinates for an event depend on the momenta of the incoming particles and the coordinates of the points where these particles were created. Spacetime is not an arena where Feynman diagrams live; it is a result of the way that the graph is put together. All of the things that we associate with spacetime, such as the metric tensor and the connection and various mathematical entities derived from them are emergent properties of this graph."

BH: "Of course, I did my work with fiber bundles, so to me there is a spacetime that serves as the base manifold of the bundle, and our various internal 'phases' are fibers erected on this."

CM: "But do you need an ether to propagate your particles through this fiber bundle manifold?"

BH: "Actually, no."

CM: "Although I tend to speak of four space-time dimensions most of the time, I'm not committed to that number of dimensions. The momenta and coordinates can have any dimensionality; ten or eleven will do just fine."

DB: "Do either of you actually do calculations in more than four dimensions?"

CM: "Seldom. The few times I actually do these calculations I perform them in four dimensions with the usual Feynman trace rules and everything."

BH: "Same here. We really don't know yet what those extra dimensions are and how they're curled up."

CM: "String/M-Theory gives us hundreds of choices right now."

DB: "But if we don't need an ether, why do we have waves?"

CM: "That's the $106,000 question, isn't it?"

DB: "But couldn't spacetime itself be the ether?"

CM: "OK, let's suppose that spacetime is that ether. The expansion and contraction of that space would be the long sought-after gravitational waves. But how does this ether also support the matter waves moving through it? And here I'm counting photons and other gauge bosons as matter. Wait a minute, I have an idea, but it is a rather strange one."

To be continued...

[Celestial Mechanic]

The Ether Dialogues (Part Two--Phonons)

CM: "Let's steal a page from solid-state physics. Imagine a crystalline solid. The individual atoms are constrained to small oscillations about their equilibrium positions. It is possible to excite collective vibrations of large numbers of particles. These vibrations are called 'phonons'. Let us imagine that the Universe is filled with particles at the ridiculous density of 10⁹³ kg/m³. All of the matter and radiation that we are familiar with is nothing but phonons in this extremely dense crystalline solid."

BH: "Haven't I seen this idea here somewhere before?"

CM: "Yes, let's give credit where credit is due. Dunash/Yul/The Poster of a Thousand Sock Puppets/etc. proposed something like this. His purpose was to hold everything else in the universe in (almost) lock-step as it spun around the Earth every day. Of course to me geocentrism with a 'g' is just a coordinate transformation and nothing more. Geocentrism with a 'G' is bad science and nothing more.

CM: "But now I must put on my WWNA bracelet and ask myself a few tough questions."

DB: "What is WWNA?"

CM: "You remember WWJD?"

DB: "Yes, 'What Would Jesus Do?' "

CM: "Well, WWNA is 'What Would Nereid Ask?' What are the toughest questions that he could possibly ask about this theory? How can I answer them? Can I answer them? A few such questions already occur to me:

CM: "1: Are all of your particles in the 'crystal' identical? Are they bosons or fermions? Any other attributes that these ultimate elementary particles or 'ultrafundamental' particles carry?

CM: "2: To have the density that they do these particles would have to each have masses on the order of the Planck mass and separation equal to the Planck distance. Is this correct?

CM: "3: All the phonons I've ever heard about behave like bosons. How do you get fermions out of this theory?

CM: "4: What about charges? How can moving waves made up of collective motions of some ultrafundamental particles carry charges such as electric charge or color charge that these ultrafundamental particles probably don't carry?

CM: "5: Can this ether be detected? Especially, can we detect our motion with respect to this ether, which was where we came in?"

BH: "Can you answer any of these questions?"

CM: "Well, this just occurred to my fetid imagination only today (2006 Feb 17); I can only answer number two and that answer is in the affirmative. My knowledge of solid-state is not even at the level of nodding acquaintance; I really should read up on this!"

DB: "But this is getting into ATM territory, isn't it?"

CM: "I suppose, so I will close this dialogue and not discuss this idea until I know a bit more about phonons. And in its own thread, if ever. I only mention this idea here as a possible way of defining a sensible ether according to the concepts of twenty-first century physics."

[the_bullet]

In relation to this thread could someone put me straight on something please ?. If space is defined by the relationships between matter,energy, events etc. then what would happen in a universe with just 2 particles ?. If one particle accelerated away from the other would it experience a force, would both feel a force, or neither ?. With only each other as reference how could you tell which was accelerating in relation to the other ?.Thanks...

[Ken G]

Or another way to put the question is, if the two particles were orbiting each other like a binary star system, how would they know? This is an especially dicey problem if the binding force for the orbit is gravity, since then both objects are still just in free fall and might seem to behave as if their was no gravity and no orbit. But the difference would be the tidal forces due to the way gravity changes with position. If all you really had were two particles and nothing else, there would be no way to carry out experiments to see if there were any tidal forces, so in that case, you really could not distinguish between an orbit or being stationary. But that's not a very interesting universe-- in ours, you conduct experiments to probe the tidal effects. Or if one of the objects has a rocket engine, you look for evidence that the rocket engine gets turned on. If you want to get deeper into it, look up "Mach's principle", though I don't think that's actually viewed as a principle any more. Maybe we need a thread on that....

[the_bullet]

Thanks Ken. I wasn't sure whether to start this as a new thread or not since it seems related to the ether debate. If, as Mach said, that acceleration was relative to background stars, what would happen in a universe with only 2 particles. I know this doesn't describe our universe, but aren't many fundamental problems researched or argued using such examples ?.Maybe such universes are impossible or extremely improbably because any universe has to contain fields such as Higgs etc and this may provide a referential background of sorts.

[the_bullet]

After further research it seems accelerating a particle in a 2 particle universe has no meaning, as distance in such a universe could only be defined after adding a third particle.

[Ken G]

I think it's OK to imagine a two particle universe as a test case. Then the only meaningful thing in such a universe is a single thing-- the vector arrow that goes from one particle to the other, which has a length and a direction. (Let the particles be distinguishable, we're not doing quantum mechanics here.) The way I see it, in various reference frames that vector can be moving and rotating all over the map, arbitrarily, and there's no problem-- ficticious forces appear to explain the behavior. But you can still tell the inertial frames, since in those frames, any acceleration of that vector is explainable in terms of forces with a physical origin, not coordinate forces.

[turbo-1]

Einstein took the simplification to another level, as well. He said imagine a single material body that is rotating. The various parts of that body will experience centrifugal forces due to the rotation. That said, with respect to what is the single body rotating? According to him, that what is the ether of GR, and the effects of gravitation, inertia, centrifugal effects, etc are all entirely local, with no action-at-a-distance.

[Ken G]

But one must be careful not to infer a causal connection that isn't there. What I mean is, I think it would be dubious to say that because you are rotating with respect to an ether, you see centrifugal forces. Rather, the causality proceeds the other way-- you see centrifugal forces, so you infer you are in a rotating frame. There is no need to ascribe any physical meaning a priori to the ether-- you have to measure the tidal effects first, as there is no other way to gain access to that information. Physics is, after all, an empirical science, not one dealing with angels on pins.

[turbo-1]

Einstein was quite explicit, though.

But on the other hand there is a weighty argument to be adduced in favour of the ether hypothesis. To deny the ether is ultimately to assume that empty space has no physical qualities whatever. The fundamental facts of mechanics do not harmonize with this view. For the mechanical behaviour of a corporeal system hovering freely in empty space depends not only on relative positions (distances) and relative velocities, but also on its state of rotation, which physically may be taken as a characteristic not appertaining to the system in itself. In order to be able to look upon the rotation of the system, at least formally, as something real, Newton objectivises space. Since he classes his absolute space together with real things, for him rotation relative to an absolute space is also something real. Newton might no less well have called his absolute space ``Ether''; what is essential is merely that besides observable objects, another thing, which is not perceptible, inust be looked upon as real, to enable acceleration or rotation to be looked upon as something real.

It is true that Mach tried to avoid having to accept as real something which is not observable by endeavouring to substitute in inechanics a mean acceleration with reference to the totality of the masses in the universe in place of an acceleration with reference to absolute space. But inertial resistance opposed to relative acceleration of distant masses presupposes action at a distance; and as the modern physicist does not believe that he may accept this action at a distance, he comes back once inore, if he follows Mach, to the ether, which has to serve as medium for the effects of inertia. But this conception of the ether to which we are led by Mach's way of thinking differs essentially from the ether as conceived by Newton, by Fresnel, and by Lorentz. Mach's ether not only conditions the behaviour of inert masses, but is also conditioned in its state by them.

The fact that centrifugal effects arise in a rotating body, the material points of which do not change their distances from one another, shows that this ether is not supposed a phantasy of the Newtonian theory, but that there corresponds to the concept a certain reality in nature.

A reference frame is an abstraction - Einstein was searching for the underlying nature of the vacuum, and he required that the vacuum have real physical characteristics that can be effected by the matter embedded in it.

[Ken G]

But I've seen quotes by Einstein in the 30's where he said that the whole ether concept was a really bad idea! (Help me out here, George.) But what is being said in the Einstein quote is not different from what I was saying, in that we are both saying there is something "real" about rotation-- it shows up in the observations. What I hear Einstein as saying is that if you want to explain what is real about rotation, you must objectify space itself. What I'm saying is, why explain it, it just is. We don't try to explain what mass or energy is, or why they exert gravity. They just do.

[Sam5]

Something that´s always bugged me: The MM experiment assumed that when the Earth travelled transversely to the "flow" of the aether a beam of light would deviate to some extent. Good. They found that it does not. But why did they assume that the aether would have any special direction of flow?

Back in the 1880s, when they conducted their experiment, it was thought that the sun and most stars were “fixed” in space and that “the universal ether” was also fixed with the stars. So M-M were looking for a detection of the “ether wind” as the earth moved through the ether it at a speed of 18.6 mps in its orbit around the sun.

So the term “transversely to the "flow" of the aether” would mean perpendicular to the direction of the earth’s motion around the sun. If the beam of light was moving in the same direction to the earth’s motion around the sun, then that would not be “transversely”. Turn the apparatus 90 degrees in either direction and that the beam of light would be moving “transversely” to the direction of the earth’s motion.

They expected an 18.6 mps “ether wind” to be “blowing” over and past their apparatus. But they didn’t find any ether wind. One interpretation is that close to the earth’s surface, the earth “drags” the ether along with it. Another interpretation is that each astronomical body “generates” its own local ether which travels through space with the body.

[the_bullet]

............. We don't try to explain what mass or energy is, or why they exert gravity. They just do.

But I thought (in my laymanesque way)that that was one of the most fundamental questions at hand today, and why many scientists hope next gen' particle accelerators will find the higgs particle. If you have a Higgs field would this then be a frame of reference of sorts for rotation within that field ?

[Ken G]

Fields don't give you reference frames, they exist in any reference frame. All you need to know is how to transform them from frame to frame. What we can know about reality is embedded in the actions of the fields and how they transform, the reference frame itself is never part of reality, at least not in current physics. Who knows, maybe future theories will change that!

[turbo-1]

But I've seen quotes by Einstein in the 30's where he said that the whole ether concept was a really bad idea! (Help me out here, George.) But what is being said in the Einstein quote is not different from what I was saying, in that we are both saying there is something "real" about rotation-- it shows up in the observations. What I hear Einstein as saying is that if you want to explain what is real about rotation, you must objectify space itself. What I'm saying is, why explain it, it just is. We don't try to explain what mass or energy is, or why they exert gravity. They just do.

The problem is (as Einstein realized), if you use the thought experiment to simplify the model to a single rotating body experiencing centrifugal forces, the body has to be rotating relative to something and that something has to be real, with real physical properties. This is fundamental. You may reject this view, but you should be prepared to defend the "spooky action-at-a-distance" that Mach proposed and that Einstein firmly rejected. I wouldn't bet against Einstein on this one.

[Ken G]

The problem is (as Einstein realized), if you use the thought experiment to simplify the model to a single rotating body experiencing centrifugal forces, the body has to be rotating relative to something and that something has to be real, with real physical properties.

Why? This is my whole point, on what basis do you claim that a rotating object must be rotating with respect to something? I say that if we observe ficticious forces in the frame of the object, like cyclone wind swirls, then the object is rotating. Where's the difficulty with this interpretation? I strongly doubt that if the Earth were the only object in all of creation, that we would not have hurricanes (except for all the other problems with not having life, no Sun, etc!).

[turbo-1]

Why? This is my whole point, on what basis do you claim that a rotating object must be rotating with respect to something?

Without a surrounding landscape (fixed or not) by which to observe rotation, an object cannot be said to be rotating. A rotating object in otherwise empty space is indistinguishable from a fixed object. An object in our Universe that is rotating experiences centrifugal forces. With respect to what does the rotation cause the centrifugal effects to arise? Would you subscribe to the Machian view that the forces arise as instantaneous action-at-a-distance with the distant objects distributed all over the Universe? That is an untenable view, if we believe that interactions are subject to some sort of "speed limit". Einstein believed that gravitation, inertia, and centrifugal effects arise from matter's interaction with the local ether.

Sorry I didn't respond sooner - I've been going through a bumpy stretch lately health-wise and have not felt up to posting to any serious threads.

[Ken G]

Without a surrounding landscape (fixed or not) by which to observe rotation, an object cannot be said to be rotating.

On the contrary, I asserted that the object may be said to be rotating if
one observes centrifugal and coriolis forces in a frame where the object is stationary. Where is the surrounding landscape there?

A rotating object in otherwise empty space is indistinguishable from a fixed object.

Except for the presence of coriolis and centrifugal terms. Of course, I cannot prove that such terms would be possible for an isolated object, but I see no problem with postulating that it could. Such a postulate eliminates all of the problems that Einstein and Mach are concerned with, in one fell swoop.

An object in our Universe that is rotating experiences centrifugal forces. With respect to what does the rotation cause the centrifugal effects to arise?

Now you are asking a different question, a question about causes. I answered that above by saying, what makes you think you need to explain rotation? It just is. We have no explanation for why particles obey wave mechanics, we simply observe that they do. So why should we explain why there is rotation? It's a fundamental entity, it's a state of matter that we can observe. We also find that it is related to angular momentum, which is conserved for a closed system. What more explanation is required?

Would you subscribe to the Machian view that the forces arise as instantaneous action-at-a-distance with the distant objects distributed all over the Universe?

No, I simply require no cause of rotation at all. I just allow rotation to be, just as I allow particles to be, and it obeys certain rules, just as particles do. What causes these rules to apply? They just do.

Sorry I didn't respond sooner - I've been going through a bumpy stretch lately health-wise and have not felt up to posting to any serious threads.

I hope this means you are feeling better now.

[the_bullet]

Would a rotating body need an external frame of reference ?.Each particle in the "rotating" body would have a slightly different velocity(speed and/or direction), and wouldn't time dilation and length contraction occur with relation to different particles ?.

[Nereid]

At one level, that question is impossible to answer - we have the universe we're in, and no other to compare 'thought experiments' against.

In another respect, answers to questions like this may come if there is a theory which produces (observable) predictions. Or, better, a pair of theories, with differing, testable predictions.

In the case of our universe, rotation is easy to detect, and you don't need to be able to 'see' anything external. For example, you can detect (indeed measure) the rotation of the Earth in a Faraday cage, at the bottom of the deepest ocean trench ... using a ring laser (and, likely, other apparatus).

[Ken G]

Would a rotating body need an external frame of reference ?.Each particle in the "rotating" body would have a slightly different velocity(speed and/or direction), and wouldn't time dilation and length contraction occur with relation to different particles ?.

This question is related to the ficticious force issue. Yes, time is proceeding differently at different places, and there is also length contraction at the periphery, relative to a frame where the Earth is stationary. But if you hold to the Machian view, you say that in the frame of the object, these effects are caused by the gravity of the matter in the rest of the universe, so you still can't say anything special about the state of the Earth itself. But I maintain that even if no such external matter existed anywhere, it would still be possible to observe the time dilation (and more easily, the ficticious forces) of rotation, but that's hard to prove given that we don't have access to that universe! However, we do have access to the laws of physics, and they say that even if you only had one Earth and nothing else anywhere, you could enter an arbitrary rotating reference frame where the Earth is spinning arbitrarily. In that frame, you would have different centrifugal and coriolis forces than you would in the stationary Earth frame, that's just first-year physics. Those different ficticious forces would not be due to the gravity of the Earth, they would be caused by the coordinate transformation itself, nothing that requires a source of gravity. All you would get from the Earth is a tiny Lense-Thirring correction, too small to even consider. So if you don't need gravity to have ficticious forces, what does Einstein's relativity really have to do with this issue?

[turbo-1]

It sounds like Einstein's concept of an aether was quite a bit different than the conventional view before Michelson-Morley. But you won't get dark matter from it, the properties of dark matter cannot be attributed to space itself (or we would not need both dark matter and dark energy).

You might want to look at this thread to see how DM and DE can both be dynamically-balanced aspects of a single field.

http://www.bautforum.com/showthread.php?t=35191

I was reviewing old threads and realized that I may have missed a point in your post. It is often lamented (especially by Sir Roger Penrose, among others) that we have no way of explaining the ~120 OOM too small observed expansive force of the quantum vacuum and the ~120 OOM too small observed gravitational equivalence of that same field. The thread linked above will explain how this can be reconciled. PM me with any questions - I'll be happy to respond.