Talk:Mach's principle

This article needs much improvement
This article needs to be entirely rewritten to For now I have just added a few citations---CH (talk) 04:22, 18 August 2005 (UTC)
 * take account of the fact that many distinct ideas have been called "Mach's principle", leading to much confusion in the literature,
 * give an accurate account of how these are/are not validated in gtr and other major theories,
 * give pointers to the most useful references in the literature, especially recent volumes/reviews.

agree - but of course the scope is still aimed at Physicists and wikipedia becomes irrelevant for the masses. — Preceding unsigned comment added by 130.76.64.118 (talk) 21:48, 27 October 2011 (UTC)

I just wrote a German Article (de:Machsches Prinzip) on this subject. It might be better or worse than this version. Maybe it could be a pointer. And thanks for comments on same. -- 217.230.58.97 08:08, 19 August 2006 (UTC)


 * The second paragraph "The idea is that the local motion of a rotating reference frame is determined by the large scale distribution of matter, as exemplified by this anecdote:..." is not really correct. Rotating reference frames were a key motivation for Mach and Einstein, but Mach's principle is not limited to rotating frames. Actually, since the term "Mach's principle" was (as stated correctly) coined by Einstein, and all the subsequent literature is related to it, it might be good to paraphrase Einstein's definition. The original definition by Einstein (in German) is from his 1918 paper on GR [Einstein, A.: Prinzipielles zur allgemeinen Relativitätstheorie. Ann. Phys. 55, 241–244 (1918)] and can be found translated in several secondary references, e.g. the section by C. Hoefer in Ch.1 of Barbour & Pfister (eds.) "Mach's principle" (ref. 6), in particular p.77: "Mach's principle: The G-field is without remainder determined by the masses of the bodies. Since mass and energy are, according to the results of the special theory of relativity, the same, and since energy is formally described by the symmetric energy tensor T_{\mu\nu}, this therefore entails that the G-field be conditioned and determined by the energy tensor." [G-field=gravitational field=metric tensor]. I would suggest to correct the relevant sentence by writing something in the style of: "The idea is that the geometry of the universe, and hence the definition of inertial reference frames, is determined by its mass distribution. As Einstein himself put it: The gravitational field is without remainder determined by the masses of the bodies. [cite ref. Einstein 1918 mentioned above]." A key issue and crucial motivation for both Mach and Einstein was the question of absolute and relative rotation, as exemplified by the following anecdote..." (although honestly I am not convinced that this anecdote is very much to the point, and sounds pretty much like "original inspiration" of whoever wrote this - I have certainly not seen it being mentioned anywhere in the literature on Mach's principle). Imtg5102 (talk) 08:22, 14 April 2012 (UTC)


 * I'm pleased to see that the above comment gives a precise reference for the original coinage of the term by Einstein. I was specifically looking for this, and frustrated not to find it in the article itself.  At present it just states that Einstein coined the term in 1918.  It would be useful for someone who knows the Wiki ropes to insert a reference into the article.109.148.240.238 (talk) 20:58, 19 February 2020 (UTC)

I agree, eg need a better mach qoute or this should be expanded, because it is very unclear what is being refreed to here, (what principles, how do they result in the same way?), "[The] investigator must feel the need of... knowledge of the immediate connections, say, of the masses of the universe. There will hover before him as an ideal insight into the principles of the whole matter, from which accelerated and inertial motions will result in the same way." — Preceding unsigned comment added by 65.29.166.232 (talk) 19:56, 15 July 2022 (UTC)

Misattribution?
The article is currently very confused about whether the quote is due to Einstein or Mach himself. In fact I think it is probably due to Born! Whoever wrote this, please fix! TIA ---CH 21:33, 24 December 2005 (UTC)


 * Seems to me that this problem is solved and so this remark can be removed. Imtg5102 (talk) 08:22, 14 April 2012 (UTC)


 * Actually, I am trying to find the quote referenced by note n. 6 both in the main English translation and in the original German text... but I am utterly unable to find it. It seems like it ether comes form Einstein or from an unofficial translation of Mach.151.61.65.209 (talk) 13:37, 30 March 2021 (UTC)

Some Clarification
The central idea here is that a particle at a point P experiences two effects from a particle O at the origin. The first of these is a force which is proportional to the product of their masses, and inversely proportional to the square of the distance between them, and acts opposite to the position vector from O tp P. The second of these is proportional to the product of their masses and directly proportional to their relative acceleration, and acts opposite to the acceleration vector of P relative to O, regardless of the distance between them. Rather than defining inertial mass and gravitational mass and constants for each, we define the unit of force by F = MA and absorb everything else in to a single gravitational constant G in the formula for gravitational attraction.

The principle of Equivalence, which says that gravitational and inertial mass are equivalent then becomes the notion that the trajectory of a particle under gravitational influence is independent of composition, and GR satisfies this because the trajectories are geodesics, and don't depend on what the body is made of.

In any case, the degree to which a body resists accceleration relative to "everything else" is caused by the inertial interaction between that body and everything else in the Universe. In a universe without other matter, there would be no accelerated frames, and no inertial forces, because there would be no other material you could say you were accelerated relative to. If the universe had half the matter in it, inertial forces would be half as strong.

This interpretation is perfectly consistant with General Relativity. If someone subjects you to sudden acceleration, you will feel inertial forces. If you stand still, and someone subjects everything else in the universe to sudden acceleration, you will feel equivalent tidal forces from "mass at a distance." These are both descriptions of the same physics.

If you look at weak-field General Relativity, which is equivalent to Newtonian mechanics, you can see that the inertial interaction between matter in a region and the rest of the universe is modified by the second time derivative of mass-energy in the region. This means that inertial shielding occurs when the rate at which energy flows in or out of a region is time-varying. Sciama showed in 1953 that inertia could be understood as a gravitational effect in linearized General Relativity. James Woodward of California State University at Fullerton showed in 1991 that there was also a time-dependent term in addition to the acceleration-dependent term we associate with ordinary inertia. His paper is "Measurements of a Machian Transient Mass Fluctuation" and can be found in the 1991 Foundations of Physics Letters, Vol 4, pp. 407-423. Woodward showed that an object with a time-varying energy density will have a non-trivial variation in its inertial mass which depends on the second time derivative of the energy.

The canonical experiment to test Mach's Principle is to fasten a capacitor to a piezoelectric transducer, and drive the capacitor with alternating current, while driving the transducer at twice the frequency, phased so that the transducer pulls the capacitor in the same direction with maximum force during the two points in the cycle where the second time derivative of the energy flow in and out of the capacitor is maximized. This should result in some non-symmetrical acceleration of the whole contraption if inertial shielding is occurring at certain points in the capacitor's charge/discharge cycle.

Experiments continue to be done on such apparatus, including one for NASA's Breakthrough Propulsion Project. Whether real results have been achieved or not is currently a subject of debate in the scientific community.

So that's Mach's principle in a nutshell. Inertia is the result of a particle's interaction with all other matter in the universe. It's not incompatible with General Relativity, and it's not necessary to drag in scalar-tensor theories like Dicke-Brans-Jordan to incorporate it into ones understanding of gravitation.Hermitian 08:18, 12 January 2006 (UTC)


 * Tom Peters inserted the following comment after the paragraph in Hermitians comment which ends "These are both descriptions of the same physics". I moved Peters's comment to this location to help keep the attributions clear. ---CH 22:50, 1 February 2006 (UTC)
 * In another sense, the GTR is in direct opposition to Mach's principle. In Mach's universe, you cannot have a complete description of a body if you do not know the dynamics of everything else in the universe.  In contrast, the GTR is a gauge theory which deals with a strictly local field.  Fundamentally, it is hopeless to do physics with Mach's principle.  The GTR saves the science of physics because you can give a complete description from local observations.  In that sense the principle of relativity is a theory ABOUT physics rather than a theory OF physics. Tom Peters 20:28, 1 February 2006 (UTC)


 * Hermitian, you seem to be one of those commentators who believe with passionate conviction that he understands what "Mach's principle" [sic] really is and what role it plays in gravitation physics. Unfortunately, perusal of the literature soon shows that as a rule such commentators violently disagree with one another, and often do not even acknowlege the existence of alternative viewpoints.  Such bibliographic oversights, in addition to internal inconsistencies and frequently loose reasoning, tends to make such statements appear based more upon stubborness and even ignorance than upon sound reasoning.  In my view, the wisest thing one can say in a brief comment is this: it seems that no-one has yet proposed a "Mach principle" which is either fully well-defined in curved spacetimes, or fully acceptable to other researchers.


 * "Loose reasoning": you are not alone, unfortunately, in appealing without comment to noncovariant concepts, as if this requires no explanation in the context of curved spacetimes. For example, you mentioned "distance" above without any explanation of what definition of "distance" you have in mind or why this definition should be considered to be physically preferred to all others!  According to Kate you have been an irregular contributor to the Wikipedia since April 2005, but in case you haven't studied the policy guidelines in detail, please note for future reference that in such a controversial context as a discussion of "Mach principles", writing "Sciama showed" rather than "Sciama argued", while acceptable in a talk page such as this, would probably not be considered sufficiently NPOV for a Wikipedia article.


 * I take it that you are not a gravitation physics newbie, but for the benefit of others, a good place to begin reading about this thorny topic might be Section D.2 of Lawrence Sklar's book Space, Time, and Spacetime. However, this is only the tip of vast iceberg. ---CH 23:29, 1 February 2006 (UTC)


 * One other thing: you wrote weak-field General Relativity ... is equivalent to Newtonian mechanics. You should know better than that!  ---CH 23:31, 1 February 2006 (UTC)


 * To address your points in order.  First of all, the notion that GR being a gauge theory is incompatible with Mach's principle's non-covariant terminology of instantaneous "mass at a distance" is misguided.  Electromagnetism is a gauge theory as well, and one can choose a representation in which the electrostatic force propagates instantaneously, even through the notion of something happening instantaneously at all points in space is horribly un-covariant and anathema to correct relativistic thinking.  Your perceived incompatibilty is a similar one of terminology and not one of physics.
 * I suppose that reformatting led you to attribute the remark on gauge theories to Hillman, but I brought that up. However, that is not my point, nor do I care much about instantaneous action.  Mach's principle, like formulated on the main page, works from a "holistic" view that everything depends on everything else.  My point is that it is impossible to even start doing physics from such a concept because prescience of the whole universe is impossible.  In contrast, the TGR can describe things locally. Tom Peters 11:43, 7 February 2006 (UTC)


 * Everything DOES depend on everything else. The net motion of "mass at a distance" determines the asymptotic boundary conditions far away from you.  A solution of GR subject to these boundary conditions determines your local geometry, which in turn determines the "forces" particles in your vicinity experience.  The example given in the article, that GR doesn't explain the forces on a rotating earth if one picks a frame in which the earth stands still, and distant mass rotates around the earth, is just plain wrong.  The entire idea behind GR is that the physics works with arbitrary coordinates.Hermitian 18:21, 7 February 2006 (UTC)


 * Fine, but in GRT you can take the local field for granted (or as an observational entity) without knowing in detail what generates it. Also there is a time lag: stuff beyond your light cone|observational horizon have had no effect (yet).  I suspect that Mach's principle does not allow such local treatment.  I fully agree with the "entire idea", but as a precept for doing physics: you should formulate your laws of physics in such a way that they are independent of the particular coordinate system you choose. Tom Peters 12:29, 8 February 2006 (UTC)


 * Your argument that claiming to "understand" Mach's principle indicates passionate conviction, rather than good physics, is a claim once made of GR as well, decades ago when it was perceived as much more arcane and understood by only a small number of people on the planet. Nowdays, we can teach much of it to undergraduates.


 * I am attempting to give a quick non-technical overview of stuff that wasn't covered in an article which doesn't really do a good job of describing Mach's principle. Going on and on about obtuse math on families of spacelike surfaces, while covariant, would not lend clarity to this explanation vis a vis the commonly used English terms for various things, like distance.


 * I think it is appropriate to use "showed" in lieu of "argued" for purely mathematical derivations that are not in dispute. One would not say that someone "argued" that quadratic equations are solved by the well-known formula most people can easily derive, as if there was an opposite point of view that needed to be presented.  Sciama's ability to do tensor calculus correctly, and derive results from the equations of GR, is not in doubt.  "Argued" is probably appropriate for Woodward's results, which have yet to be widely accepted.


 * For a quick non-technical overview of what's happened since Mach articulated his principle, I think equating linearized GR with Newtonian gravitation is perfectly acceptable.


 * Hermitian 08:53, 7 February 2006 (UTC)

Hermitian, I am finding this very difficult to follow because the attributions have become so munged, despite my efforts. Please, everyone, try to insert your comments at the bottom, and format all your paragraphs consistently to match your signature. This should make it much easier to see at a glance who wrote what. I would certainly not agree that hyperslices are irrelevant or constitute "obtuse math"! This is a key point: much of the incredible confusion in the literature (and discussions like these) is entirely preventable (and unenlightening, hence a waste of everyone's time) because commentators were too lazy (or ignorant) to make their thinking precise. You absolutely do need to use the language of mathematics because, for example, much of the "controversy" arises from various parties confusing mathematically distinct notions of things like "rotation" which are central to discussing Mach's ideas and suggested applications. In general, WikiProject GTR is trying to raise the bar (while also trying to make all these articles easier for technically challenged readers to get something useful from!), but in this case, there is a very strong case to be made for the neccessity of not trying to "save" readers from exposure to any higher mathematics.

I am glad that you do know that linearized GR =/= Newtonian gravitation. ---CH 02:59, 11 February 2006 (UTC)

Students beware
I extensively edit the August 2005 version of this article and had been monitoring it for bad edits, but I am leaving the WP and am now abandoning this article to its fate.

Just wanted to provide notice that I am only responsible (in part) for the last version I edited; see User:Hillman/Archive. I emphatically do not vouch for anything you might see in more recent versions.

Be aware that Mach principles (see the arXiv eprint by Hermann Bondi for the plurality of Mach principles), is one of the most contentious topics in gravitation physics. Unfortunately, several WP editors have attempted in the past to slant this and related articles to present their own idiosyncractic view as the only view, or have suppressed the fact that this topic is highly controversial (or have simply unbalanced coverage by presenting far more information about their particular view than about the dozens of alternative views).

Good luck in your search for information, regardless!---CH 01:57, 1 July 2006 (UTC)

Mach's Principle v. Mach Principle
Mach's principle is a particular statement—the content of which is, unfortunately, very vague. On the other hand, a Mach principle is any statement (hopefully less vague) which either is, or pursues the spirit of the original Mach's principle.

"A Mach principle" is syntactically and semantically distinct from "Mach's principle". The class of principles qualifying as Mach principles deserves its own page, as does the historically important and distinct Mach's principle. Thus, I have killed the redirect on Mach principle and put some distinct and (hopefully) useful information on that page. I think it is very useful to have one page dedicated to the history of this notion, and one to the jungle of statements which have actual scientific value. MOBle 01:11, 24 August 2006 (UTC)


 * As I am not a native English speaker I do not understand in full what "Mach principle" in fact means in this context. I wrote both articles for sl WP from English versions and named second term as "Machian principle" (Slovene machovsko načelo) in similarity to Euclidean space (evklidski prostor) (in contrast to Euclid's lemma (Evklidova lema) or Euclid number (Evklidovo število)) and such - but I am not sure if this naming is correct. Are terms "Mach" and "Machian" in this case equivalent? --xJaM 14:19, 12 October 2006 (UTC)


 * The difference in meaning is only very subtle, so it's mostly just an issue of style. I think I might actually prefer "Machian principle" slightly, but others had already used "a Mach principle", so I figured we should stick with that, here.  I'm not committed one way or the other for the English, and I guess you should use whatever sounds best in Slovene.  My only concern was to clarify the distinction between history and science/philosophy.  --MOBle 17:49, 12 October 2006 (UTC)


 * I see. I understand your concern for the distinction. Here I also see one difference between English and Slovene in one another example: a term Galilean transformation is in Slovene in fact named Galilei('s) transformation (Galilejeva transformacija and not galilejevska ~). Further on Lorentz transformation in English is not called Lorentzian. Perhaps I didn't choose the best example, because "Galilean" here might in fact mean "Galilei('s)", but also it can be one speciality in English. --xJaM 11:15, 13 October 2006 (UTC)


 * I would like to say that I would have personally found it extremely helpful to find the material under Mach principle on Mach's principle and I therefore support the merge. 1Z (talk) 13:24, 4 January 2011 (UTC)


 * Regardless of syntactical or semantical concerns, wikipedia should reflect the common habits of professional literature on Mach/Mach's/Machian principle. To my knowledge, there is NOT A SINGLE of the dozens of academic articles and books on Mach('s) principle that makes a distinction between Mach principle, Mach's principle or a Machian principle, and the preferred term (actually the ONLY ONE used in the professional literature, as far as I know) is "Mach's principle", since this was the original term coined by Einstein. For example, Julian Barbour, the leading expert on the subject and editor of the standard book "Mach's principle" (cited as ref.6 in the "Mach's principle" article), systematically refers to "Mach's principle", even when he explicitly reformulates it within the contect of his own theories (see his recent "The Definition of Mach's Principle", Foundations of Physics 40 (2010) 1263-1284; http://arxiv.org/abs/arXiv:1007.3368). Even the article by Bondi and Samuel which is cited in the "Mach principle" article as the main inspiration to distinguish between "Mach principles" as opposed to "Mach's principle" actually does not use the term "Mach principle" but only "Mach's principle". This distinction is therefore confusing, contrary to established standards and should, IMHO, be removed (i.e.: the article "Mach principle" should disappear). The paragraph "Examples" from "Mach principle" could be integrated into the article on "Mach's principle". Imtg5102 (talk) 07:17, 14 April 2012 (UTC)

Removed paragraph
Archelon removed the following paragraph:

It is very easy to understand that we need some metrical system which consist of mutually related parameters (or observables) and to pin somehow one end of such proportions to some datum-point. This process is very well visualised in crystalization process when we have some initial place in the space where crystalization starts (this place can be called as a datum-point of crystalization). And the rest of the system is affected and obeys some rules created at that initial datum-point.

(It had apparently persisted for about a week). The paragraph is not claimed to be nonsensical, though it is worded a bit obscurely; but it makes no sense in the context where it was inserted. Archelon 00:23, 18 February 2007 (UTC)

'Disputed Science'
Is there general agreement that this 'Pseudoscience Infobox' is appropriate here? Certainly at least some Mach principles do not fall under the heading of pseudoscience, disputed though all of them may be. Archelon 00:27, 18 February 2007 (UTC)

'Mach's Holographic Principle"
There is a great preprint on the arxiv "Mach's Holographic Principle" by Khoury and Parikh (http://arxiv.org/abs/hep-th/0612117). There Mach's principle is taken to mean the idea that inertia is determined entirely by the matter content in the universe.

The common objections general relativity being Machian, it is argued within, essentially boil down to the fact that one, in solving GR's field equations, is allowed to select initia data for the induced metric and extrinsic curvature completely independently of the matter on the initial surface/boundary. Therefore, the geometry (given by the metric) defines inertia (acceleration is defined with respect to the geodesics of the spacetime). However, in GR this geometry is determined not just by the matter (via the Einstein field equations) but also by arbitrarily chosen initial conditions. A process of replacing the initial conditions by boundary matter so that inertia is determined entirely by matter content, is described. HaludzaHaludza 10:44, 20 April 2007 (UTC)

'Disputed Science???'
I see no reason to describe this subject as pseudoscience. What justification is proposed for the pseudoscience box.

Martin Hogbin (talk) 20:25, 17 January 2008 (UTC)

'Disputed Science???'
I propose to delete the pseudoscience box.

Martin Hogbin (talk) 09:18, 18 January 2008 (UTC)

Foucault’s pendulum
Why would Foucault’s pendulum oscillate inside a thick rotating sphere? Oscillation is driven by gravitation, and gravitation inside the sphere cancels out, doesn’t it? --Yecril (talk) 20:12, 19 October 2009 (UTC)

particles
I wonder how this principle can have a meaning with actual quantum gravity and origin of inertia in particle physics, and wht about locality, GR is very very local. (To me this problem looks the same as current induction in electromagnetism). An experiment in GR can be made locally, and the centrifugal force depends on the speed of spining that can be experienced locally, and so with or without mass it is always the same locally. Where relative motion to define centrifugal force must appear is between particles which are part of the spining body. Could a single particle spining in an empty universe exist? I see no objection in a classical universe, the spining particle would create radiation because there are not only gravity!!!! the particle should have an energy lost in radiation,(excepted if the universe is closed, radiation could come back). But what is the meaning for a single point particle that doesn't radiate and has really not any spatial extension? It doesn't mean a lot I guess. Now my point is in particle physics we use the higgs to generate mass, and it is local, it doen't need far stars, I will search for link between graviton and higgs, a friend of mine had already talked to me about that, I hope I asked myself too in vague terms before, BUT a priori the higgs are not graviton, and even if they were we don't need far stars to generate inertia. More, in a quantum universe, with quantum fields, a single particle can't exist, then there exist always a relative motion and then relative relative motion => accelerations, I didn't say it was why we need quantum, but quantum field theory looks to be a "relation" theory (or interaction), that's what we need no? like it is wrote in the article.

So far stars are far.Klinfran (talk) 01:48, 8 January 2010 (UTC)

Answer
space existence cannot be imagined,no body in this world can exactly say how the space came into existence.Time and space are in same dimension. — Preceding unsigned comment added by 123.201.131.2 (talk) 06:09, 22 February 2019 (UTC)

"You are standing in a field looking at the stars. Your arms are resting freely at your side, and you see that the distant stars are not moving. Now start spinning. The stars are whirling around you and your arms are pulled away from your body. Why should your arms be pulled away when the stars are whirling? Why should they be dangling freely when the stars don't move?"

It's a balance between electrical forces that hold your body's atoms together through mechanisms such as hydrogen bonds, Van Der Waals forces, covalent bonds, ionic bonds, etc.. Storage of energy occurs in the tension and compression of materials relative to their "relaxed" state. Just because such a feeling is persistent does not mean that it is connected to the stars.

Doing work on a particle will change its inertial frame as a result of a force and a displacement. Forces and displacements occur through the relative motion with respect to field potentials. Such field potentials are tied directly to the very objects in which they interact. Therefore, the account for the amount of energy gain or lost by a particle is in direct connection with its motion relative to the field potentials of other particles. In other words, the work done on one particle by others is what determines the position and velocity of a particle at any given time.

Only the local forces play a role in determining the work done on a short term basis. However, to account for the kinetic energy of the particle relative to the spinning body, whose motion is relative to a larger spinning body, whose motion too is relative to a much larger spinning body, you must consider the distant forces that were involved to account for the complete motion of this particle relative to the mass of the universe.

Ultimately, you end up with the rule where all the work done a particle, since the history of its formation, is done relative to the inertial frame of the particle at the time of its creation (possibly through the conversion of electromagnetic wave energy into that particle).siNkarma86—Expert Sectioneer of Wikipedia undefined 23:30, 26 March 2011 (UTC)


 * g, vague, unclear, not logical proression to conclusion Juror1 (talk) 15:13, 16 June 2017 (UTC)

Rewrite or omit last two paragraphs (starting with "Initial Value Problem").
As an interested non-physicist (student of Berkeley, Kant and Hegel) I found most of the article comprehensible and stimulating. But the last two paragraphs descend into incomprehensible gobbledygook, either willfully ("This section reserved for members only") or (more likely) because the author was unsure what point he or she was actually trying to make. Please revise or omit.66.108.110.211 (talk) 09:20, 12 June 2011 (UTC)

The Spinning Bucket paradox
I have deleted that section for several reasons. Firstly it was completely unreferenced. The title is not that most commonly used for the general subject; it is usually called Newton's bucket. The resolution referred to some specific assumptions about GR. It is in the wrong place, it would better form part of the history of the subject.

I intend to add more material to this article, including Newton's bucket, taken almost exclusively from the book "Mach's principle from Newton's bucket to quantum gravity". I think it is OK to do that, the book consists mainly of a number of papers by experts in the subject and is by far the most comprehensive reference work on the subject. Martin Hogbin (talk) 13:09, 12 March 2014 (UTC)

Mach's vs Mach
There are two separate pages! Will bring in the few lines from there. No point in two spellings, except confusion. A tensor a day... (talk) 14:42, 24 November 2015 (UTC)

Oh Mach oh Mach...
Now that I have read this page, I see so many problems in it. By the way, the idea was mentioned in the NY Times today, and the page is in a very sad state. Will try a few fixes, but it is mostly throw away material in this page now. A tensor a day... (talk) 14:42, 24 November 2015 (UTC)


 * Wow. What a mess. Good luck with the pruning. Remember that everything is saved in the history, so you can be quite WP:BOLD in doing so. -- The Anome (talk) 15:01, 24 November 2015 (UTC)


 * I will try to be bold after my tears have dried following my reading of this page. Even key items like the famous paper which relates to the letter of Einstein to Felix Pirani mentioned in the NY Times article are not in this page now. Will try to delete some material and add a better, but necessarily shorter, summary for now.  A tensor a day... (talk) 15:36, 24 November 2015 (UTC)

Assessment comment
Substituted at 22:44, 29 April 2016 (UTC)

einstein's letter to Mach
FYI, the book Misner Thorne Wheeler contains a facsimile of Einsteins letter to Mach. Legible, but its not a terribly good image, though.67.198.37.16 (talk) 23:17, 1 May 2016 (UTC)

On the significance of experimental verification
Newton's bucket and the Michelson-Morley experiment led to lively discussions in the scientific scene of the time around 1900 and in particular inspired Albert Einstein in the development of his general theory of relativity.

Nowadays, experiments in this field have reached dimensions that can only be financed on the basis of globally organized media campaigns. As a result, the pressure to succeed in such experiments is also reaching previously unheard-of dimensions. This can lead, in particular, to a procedure of generating prefabricated "templates" before the actual measurements begin, as has become routine for example in the current search for gravitational waves. When further experiments then substantiate the suspicion that claimed gravitational wave signals originate from inside the experimental setups, this obviously does not affect the public acceptance of gravitational wave detection.

The high-speed rotor experiment proposed by James C. Keith in 1963 and its significance in view of Mach's principle (related section "Experimental Verification" meanwhile deleted from main article) had no chance of being recognised due to lack of public promotion. Jan Fremerey (talk) 10:14, 15 August 2022 (UTC)

Abandoned user draft
Please would an interested editor assess the value of this addition which was made in the abandoned WP:COPYARTICLE (now blanked) User:Christillin/Mach e centrifuga in 2012:


 * Recently a semiquantitative realization of Mach's principle has been obtained, within the framework of an "effective" vector theory of gravitation, as regards both the Coriolis and the centrifugal force.

User:Christillin lists other user drafts which may likewise be worth checking. – Fayenatic  L ondon 14:50, 15 September 2022 (UTC)

"Experimental verification" section
I deleted the whole section because it has been written by the author of three texts used as sources (two are not even scientific papers) which seems to be against more than one Wikipedia rule

The full text I deleted is as follows:

In 1963, based on relativistic theories of gravity, James C. Keith proposed a high-speed rotor experiment suitable for testing the validity of Mach's principle. First laboratory investigations in the early 1970s seem to confirm Keith's predictions.

The text had been written by user @Jan Fremerey who is also the author of documents 2,3 and 4 quoted in above.

Friendly Neighbour (talk) 16:41, 30 May 2023 (UTC)


 * Dear Friendly Neighbour,
 * I don't agree with your action for the following reasons:
 * (1) Mach's Principle is a theoretical concept which still requires experimental verification in order to be accepted worth being recognised and discussed by the science community.
 * (2) The cited paper by J. C. Keith [1] predicts slowing down of a fast spinning steel ball due to gravitational interaction with external masses, see in particular on page 11.
 * (3) The only documented proof of Keith's theory was carried out and published [2] by myself in Physical Review Letters, a refereed scientific journal.
 * (4) Reference [3] is nothing but a more detailed description of the experimental setup and more explicit data that have not been published in reference [2] due to limited space.
 * (5) Reference [4] by explicitely referring to page 11 of ref.[1] just points to the relevance of Keith's theory in view of Mach's Prnciple, a matter that has not been recognised in the previous references.
 * (6) References [3] and [4] are to be understood just as supplementary information to references [1] and [2] for better information of an interested reader of Wikipedia. This information does not require any further proof or status as expected from a refereed publication, but may be welcome for better understanding.
 * Kind regards,
 * Johan K. Fremerey Jan Fremerey (talk) 11:13, 1 June 2023 (UTC)

You are ignoring two papers which directly rejected the Keith effect you were trying to prove on theoretical grounds:

 Reinhardt M. and Rosenblum A., 1973, The Nonexistence of a Relativistic Effect Proposed by Keith, Lettere al Nuovo Cimento, 6 (5), 189-191 Frehland E., 1973, Critique of the Gravitational Radiation Damping Effects Calculated by Keith, Lettere al Nuovo Cimento, 7 (12), 490-492 

The former says: We conclude that the effect proposed by KEITH cannot exist, and hence cannot be the explanation for the residual decrease of angular momentum in Fremerey's experiments.

And if you tried to confirm an non-existing effect, how does it test the Mach's Principle?

So quoting just your results is definitely one-sided and misleading as there is no consensus that your measurement did confirm the Mach's Principle in any way.

Friendly Neighbour (talk) 19:36, 1 June 2023 (UTC)


 * Please note that the authors you cite do not consider in any way the central condition for Keith's rotational drag, namely that the spinning rotor consists of a finite number of discrete mass points, see ref. [1] and https://www.researchgate.net/publication/285131494_Laboratory_test_of_gravitational_drag. This condition is obviously satisfied by the spinning steel ball and is what makes Keith's predictions so valuable in terms of experimental verifiability at the laboratory scale. Jan Fremerey (talk) 07:20, 2 June 2023 (UTC)
 * Well the criticism was quite substantial and well argued, especially in the Reihardt and Roseblum paper. First of all, they show that Keith used an obviously wrong theory of gravity to calculate the effect (Birkhoff theory which does not even reduce in weak field limit to Newtonian gravity). Second, even as Keith claimed that a similar effect will be present in General relativity he was obviously wrong because a dipole terms in radiation are not possible. Third, and most important, if the effect existed, it would be visible not only in rotating pairs of pulsars but even "normal" stars and it is not. All this means that the Keith effect as strong as he predicted does not exist unless General Relativity is wrong and rotating stars do not feel the effect unlike laboratory spheres which would be an interesting effect but not necessarily evidence of mach's Principle correctness. Friendly Neighbour (talk) 18:30, 3 June 2023 (UTC)
 * I agree with Friendly Neighbour's edit on WP:COI grounds alone.  Wikipedia is not the place for you to promote your publications.  In compliance with WP:DISCLOSE you should have disclosed your conflict of interest on this page before citing your papers. And WP:primary sources like research papers are not a sufficient support for content on WP, especially if all but one are written by the same person. Wikipedia requires secondary sources like survey articles or textbooks (WP:PSTS). From the papers referenced above it seems this is a controversial theory held by only a few researchers. --ChetvornoTALK 19:20, 3 June 2023 (UTC)
 * I would add that a discussion of the above quoted papers should have place if there was a Wikipedia article on the Keith effect not here because even the connection of the alleged effect and the Mach's Principle seems tenuous. We do not have such an article and probably there will never be one because as @Chetvorno stated it was supported only by a few researchers and has been actually already forgotten (no new papers about it since at least 1980). Friendly Neighbour (talk) 08:52, 4 June 2023 (UTC)
 * That said, I found one paper (unfortunately in Spanish) about the Mexican experiments in 1971-1986 trying to repeat Fremerey's experiment using ultracentrifuges used to separate uranium isotopes (Galindo, Cabrera and Cervantes-Cota, 2013, En busca de los efectos gravitacionales de Birkhoff: la ultracentrifuga transelastica, Revista Mexicana de Fısica E 59, 101–114). I translated the relevant fragments using Google Translate and it is evident they could not repeat Fremerey's results (there is a sentence in the conclusions stating this directly). So I think the only thing we could add to the article is that an alleged effect, allegedly supporting the Mach's Principle has been tested but the early positive results have not been confirmed.
 * By the way, I know of other attempts to confirm experimentally the Mach's Principle but they all failed. We could add a section about this but because they all are pretty old and obscure, I would vote against it. Friendly Neighbour (talk) 09:10, 4 June 2023 (UTC)
 * You obviously did not have a serious look at Keith's paper, nor have the authors you cite, Reinhard and Rosenblum. Otherwise you would have noticed right from the abstract that the drag predicted by Keith is only observable on small rotors, see also my previous quote, since it decreases with increasing radius of the spinning system. Keith, in fact, proposed a 0.1-mm steel sphere for experimental verification. So arguing with rotating systems of celestial dimensions does not really make sense. When the authors argue against Birkhoff's flat spacetime theory of gravity, they obviously did not notice that Keith refers to Birkhoff in the present case mainly for better handling of certain mathematical procedures. Jan Fremerey (talk) 11:54, 4 June 2023 (UTC)
 * Wikipedia is no place to do original research. We can report only the findings from existing literature and there are two theoretical papers contradicting the existence of the very effect you were looking for and one saying that your result were not reproduced in 15 years of careful experiments.
 * Still, I do not find your claim that Keith claimed the effect can be observable *only* on small rotors anywhere in his paper. Quite contrary, he is talking about gravitational radiation quite stronger than the one predicted by Einstein's General Relativity (1/c3 versus 1/c5). This is in direct contradictions to the results of Hulse and Taylor Jr. for which they received the Nobel Prize in 1993. Keith could not know that but in 2023 it is absolutely obvious that the Keith effect does not exist. Friendly Neighbour (talk) 14:52, 4 June 2023 (UTC)
 * "one saying that your result were not reproduced in 15 years of careful experiments." - The mexican authors, in fact, did not do any serious investigations of the kind we are discussing here. So, of course, they were not able to reproduce my former results.
 * "Still, I do not find your claim that Keith claimed the effect can be observable *only* on small rotors anywhere in his paper." - I apologize for my misleading statement on rotor size. This, in fact, is only implicitly given by maximum rim velocity aω of the spinning rotor due to limited material strength. As the Keith drag is proportional to a3ω4, see abstract, it will increase by reducing a in favour of   ω, see also eq.(48) on page 23 of his paper.
 * "This is in direct contradictions to the results of Hulse and Taylor Jr." - I don't think so as Keith drag is negligible in case of large scale systems. So a3ω4 in case of Hulse-Taylor is 10 orders of magnitude smaller than with the 2.5 mm steel ball of our experiments at 75 kHz rotational frequency. Jan Fremerey (talk) 07:30, 5 June 2023 (UTC)
 * I think this discussion leads to nowhere. So I want to finish it (at least my part in it) with the elephant in the room. If you really managed to detect the Keith effect, you would have proven Einstein's General Relativity to be wrong. It would be the only experimental evidence of that, so far. Also it would be a sure Nobel Prize for you. It did not happen and you know well why. I think the subject is closed at least unless some future papers on it appear. You may promote your results, but please do it elsewhere. Friendly Neighbour (talk) 08:21, 5 June 2023 (UTC)
 * "If you really managed to detect the Keith effect, you would have proven Einstein's General Relativity to be wrong." - What leads you to make this statement? My experimental results rather seem to speak in favour of Einstein, see Fig.2(b) and caption in ref.[2].
 * "I think this discussion leads to nowhere. So I want to finish it (at least my part in it) with the elephant in the room." - Thank you, anyway, for the friendly and substantial discussion on this topic. Jan Fremerey (talk) 11:09, 5 June 2023 (UTC)
 * "If you really managed to detect the Keith effect, you would have proven Einstein's General Relativity to be wrong. It would be the only experimental evidence of that, so far. Also it would be a sure Nobel Prize for you." - If you rate the significance of Keith's experiment at that level, wouldn't you give it a chance of being mentioned in the main article on Machs's principle? Jan Fremerey (talk) 00:15, 7 June 2023 (UTC)
 * Friendly Neighbour: "We can report only the findings from existing literature ..."
 * In view of your above objections, would you accept the following revised version of my deleted contribution entitled "Experimental verification" for publication on the WP main page on "Mach's principle" ?
 * "In 1963, based on relativistic theories of gravity, James C. Keith proposed a high-speed rotor experiment [1] suitable for testing the validity of Mach's principle, see on page 11. First laboratory investigations [2] in the early 1970s seem to confirm Keith's predictions. Unfortunately, the experiments were never repeated or even seriously discussed, probably due to quick objections of certain mainstream theorists [3][4] against Keith's proposal [1] on the basis of not yet fully understood gravitational theories and inappropriate astronomical observations."
 * 1. J. C. Keith, “Gravitational radiation and aberrated centripetal force reactions in relativity theory”, Rev. Mex. Fís., vol. 12, no. 1, pp. 1–25, Jan. 1963
 * 2. J. K. Fremerey, "Significant Deviation of Rotational Decay from Theory at a Reliability in the 10-12 sec-1 Range", Phys. Rev. Lett. 30, 753 (1973)
 * 3. Reinhardt M. and Rosenblum A., 1973, "The Nonexistence of a Relativistic Effect Proposed by Keith", Lettere al Nuovo Cimento, 6 (5), 189-191
 * 4. Frehland E., 1973, "Critique of the Gravitational Radiation Damping Effects Calculated by Keith", Lettere al Nuovo Cimento, 7 (12), 490-492
 * Please note that I have replaced my own references [3] and [4] with published papers you mentioned above. Jan Fremerey (talk) 20:50, 25 June 2023 (UTC)
 * Please note that I have replaced my own references [3] and [4] with published papers you mentioned above. Jan Fremerey (talk) 20:50, 25 June 2023 (UTC)