Observe how they moved and changed in ancient times when light left them.

Dear Jerry,

once their light has arrived at our location we will be able to detect it, but shouldn't we also expect some specific observable effects due to gravitational potential originating from those sources? This apparently complies with independent suggestions by Ernst Mach and James C. Keith in order to explain the occurence of inertial respectively drag forces that become observable on accelerating masses.

"independent suggestions by Ernst Mach and James C. Keith"

Here are some original statements:

Ernst Mach (from Wikipedia: "Machsches Prinzip"): "Der Versuch Newton’s mit dem rotirenden Wassergefäss lehrt nur, dass die Relativdrehung des Wassers gegen die Gefässwände keine merklichen Centrifugalkräfte weckt, dass dieselben aber durch die Relativdrehung gegen die Masse der Erde und die übrigen Himmelskörper geweckt werden." - English translation (DeepL): "Newton's experiment with the rotating water vessel only teaches that the relative rotation of the water against the walls of the vessel does not generate any noticeable centrifugal forces, but that the relative rotation against the earth's mass and the other celestial bodies awakens these forces."

James C. Keith (on page 11 of above cited paper, see below): "It is as if entire reaction force on the universe, a universe which cannot itself react to forces and torques inertially, acted back on the freely spinning mass system causing a real slowing down."

Mach's Principle: See link below.

http://blog.alexander-unzicker.com/?p=92

In standard general relativity, the local inertial frame is determined by all the matter present - those nearby as well as those very distant. Hence, at a given location, the difference between a static frame and a local inertial frame can reveal some aspect of distant matter. 

"the difference between a static frame and a local inertial frame"

Dear Patrick,

should the "static frame" be attributed to "very distant matter" ? If so, how do you suggest the presence of such a static frame can be detected? That's essentially my question.

Dear Johan,

  Since the gravitational effect of distant matter is expected to be much weaker than the effects of nearby massive objects, actual detection of a signal pertaining to distant matter effect is extremely difficult. But one can consider the following thought experiment: If one deploys a clock A orbiting at a distance of 70 kilo-parsec from the centre of Milky Way, then its rate of ticking will be governed by the total gravitational potential at its location (and also its speed). If we know accurately the potential due to the Milky Way alone then we can compare A's ticks with a clock B  static on Earth. Of course, we have to know accurately the total gravitational potential  at B's location (which will be dominated by the Earth and Milky Way's gravity). The difference in the rate perhaps will quantify the effect of distant matter. Best wishes.---Patrick

"Since the gravitational effect of distant matter is expected to be much weaker than the effects of nearby massive objects"

Dear Patrick,

from where do you take the above expectation? J.C. Keith on page 23 of his above cited paper obviously states the contrary: "Interactions with large external masses as the sun or galaxy depend on the value of k' = 2GM/Rc2 multiplied by (46), and are small fractions (10-8, 10-6) of the effect (46)." This of course makes sense in view of Mach's principle suggesting inertia to result from interaction with the total universe rather than with a few nearby objects.

Dear Johan,

  My argument is based on standard general relativity and not Mach Principle inspired gravity theories like that of Brans-Dicke or Hoyle-Narlikar. Local inertial frame is determined more due to nearby mass distribution, e.g.  a freely falling frame near the surface of the Earth is determined more by Earth's mass and much less due to distant galaxies. Such views have already been discussed in Weinberg's classic 1972 book on general relativity. Best wishes.----Patrick  

"a freely falling frame near the surface of the Earth is determined more by Earth's mass and much less due to distant galaxies."

Dear Patrick,

that's right, of course, when considering M/R2 proportional forces. These, however, are  of short-range type, while Keith is rather considering long-range terms of type GM/Rc2. Please have a serious look at Keith's paper where, on page 3, he states: "If M is so remote that forces of 1/R2 and higher order are negligible compared with those of 1/R order, GM/R can be taken as virtually constant in space and time over the extent of a small rotating body."

As far as I understand Keith, he doesn't expect static forces from interaction with remote masses but rather dynamic effects that will unveal only on accelerating bodies.

Dear Johan,

 Sure, I will read the paper. Best wishes.---Patrick

The paper has been published in 1963, well before today's high precision gyroscopes and atomic clocks, and better understanding how to use General Relativity (for example for GPS).   One can bet that many papers about Mach's principle have been published in between, discussing similar questions.

As non-expert in the topic I would first check the literature since then.  On Google I did not find any citation of this paper, but mention of 6 citations for the first part.

"On Google I did not find any citation of this paper, but mention of 6 citations for the first part."

Dear Daniel,

the second part has been cited at least as many times in well appreciated scientific journals as the first one even if you won't find respective counts on Google. Apart from that, quoting in general presupposes prior reading with the aim of understanding.

I believe I've shared the following thought experiment on RG before, but it seems to me it refutes Mach's Principle on a conceptual level:

Imagine a spacecraft coasting on a uniform path relative to the "fixed stars" which comes under the influence of a stellar object nearby and begins to deviate toward it, while continuing in uniform motion by the evidence of free-floating objects inside. In order to maintain the original course a thruster is fired, and inertial effects are experienced onboard as the craft accelerates just enough to counter the influence of the local gravitational field, in order to maintain the intended course.

Note that inertia is experienced only when maintaining the craft's relationship with the distant masses, not when deviating.

Ciufolini and Wheeler describe in their first chapter of their book, "Gravitation and Inertia" the effect of distant matter vs. the immediate vicinity of earth on frame dragging. They define the voting power as the mass of Earth (in cm) divided by its radius, yielding 0.69 x 10-9.  This gravitomagnetism effect has been recently measured and reanalyzed to agree very well with GR. They quantify the contribution at large as the mass there divided by the distance from there to here.  It is pointed out that although one can use the Friedman model to calculate the total mass the initial value problem imposes a difficulty on how to calculate distance (at what time etc?)

Adopting the fuzzy average of a three sphere model they end up with the poor man model for inertia whose radius is 4.5 x 1028 cm. This radius contains 100% of the mass of the universe at ~6 x 1056 gr or 4.5 x 1028 cm. We see that the voting power of the out there is 9 order of magnitudes larger than the here.  Indeed multiplying Earth's voting power by its rate of turn gives an effect of 330 milliarcsec per year. Does this explain Inertia?

"Note that inertia is experienced only when maintaining the craft's relationship with the distant masses, not when deviating."

Dear James,

nice idea, such an image, for getting things clear, yet I doubt that it really applies to the situation discussed here. The presence of essentially "flat" M/R dependent background fields originating from remote sources should in no way preclude the occurence of forces due to superimposed M/R2 dependent gradient fields originating from nearby sources.

a different explanation to the Inertia which would rely on the equivalence principle would come from the local vacuum via the Unruh effect

a different explanation to the Inertia which would rely on the equivalence principle would come from the local vacuum via the Unruh effect

"They quantify the contribution at large as the mass there divided by the distance from there to here."

Dear Asher,

that's exactly what Keith states on page 3 of his above cited paper: "If M is so remote that forces of 1/R2 and higher order are negligible compared with those of 1/R order, GM/R can be taken as virtually constant in space and time over the extent of a small rotating body."

The following contribution has been exported as "off topic" from a parallel discussion on gravitational waves:

Dear Zbigniew,

As we know from Newton, Einstein and observation, gravitational potential Vgrav ~ GM/R is doing something noticeable to space. Only its local gradient in case of our sun is capable of holding heavy planets on closed orbits. As I learn from Keith's paper (cited above) gravitational potential of our sun is only about one part in 108 of the local accumulated contributions (Vgrav)local = G*Σ(Mi /Ri )universe from remote masses Mi of the universe. The latter due to large distances Ri of sources Mi doesnt't provide sufficient gradient for generation of local static gravitational forces. On the other hand, it shouldn't be excluded that the huge amount of gravitational potential from remote sources will have some noticeable effect on moving bodies like, in particular, the occurence of inertial forces on accelerating bodies, as already suggested in late 19th century by Ernst Mach, or limitation of propagation speed and other “material“ properties of local space that might be attributed to what is called “(a)ether“.

Dear Johan K. Fremerey,

Yes, I'm attaching a recent book by Dr. Jeremy Dunning-Davies and myself addressing gravitational theory together with three supporting papers for your interest.

God Bless,

Dennis P. Allen Jr., PhD

Dear Dennis,

(1) After first having examined the "supporting papers", see my comments below, I'm pretty sure that these do not tell anything about gravitational interaction but rather describe common vibrational interference respectively gasdynamic effects excited by a rotating disk and transfered to nearby mounted sensing disks or screens. I don't see any relation between experiments and theoretical considerations as pointed out by V.N.Samokhvalov. As I'm not a theoretical physicist I cannot give any valuable comments on the gravitational theories involved.

(2) The Samohvalov interaction-of-spinning-masses experiment describes quite common dynamic behaviour of disk-and-shaft type rotor systems with no hint towards gravitational interaction.

(3) The Morgan experiment apparently demonstrates the effect of air turbulences excited by the fast spinning wheel, which I guess should be many orders of magnitude larger than any possible gravitational effects.

(4) The author in continuation of his previous investigations apparently is excited by his mass dynamic interation theory so that he completely forgets about clear investigation of mechanical vibration coupling between his rotating and screen disks.

Dear Johan,

As to the Morgan experiment, one would expect the driven of the two discs to turn slowly in the same direction as the accelerating driver disc since the air is slightly viscous.

The main point of the Part 2 of Dr. Jeremy Dunning-Davies and my book was that there exist two fields that are basically related as electric and magnetic fields are in the Maxwell equations; and so then one would expect to have gravitational-inertial waves in analogy to electromagnetic waves ... and so also have inertial induction in analogy with magnetic induction as well. But you do not seem to have even realized this basic point. Is English not your native language?

God Bless,

Denny

"turn slowly in the same direction as the accelerating driver disc"

Dear Dennis,

we should expect the sensing disk to turn along the direction of the air stream excited by the driver disk. With the whole setup adjusted to perfect rotational symmetry there may be no net effect on the sensing disk, while any deviation from symmetry may result in a net effect in either forward or backward sense as related to the driver disk spin direction. In the Morgan experiment I have been missing systematic investigation along this direction.

"inertial induction in analogy with magnetic induction"

I'm much a fan of Thierry De Mees's papers on basis of the Heaviside theory and stunning support by astronomical observations. I think that Thierry might be interested in your work and would be able to provide expert comments.

"gravitational-inertial waves in analogy to electromagnetic waves"

"Gravitationaldynamic" effects I think should rather be expected to become effective on high speed rotating systems such as proposed by J.C. Keith, see related references at the entry of the present discussion. Perhaps some theoretical physicist will be able to link your theoretical findings with the ones proposed by J.C. Keith?

Dear Yohan,

Many thanks for the reply. I completely agree that further experimental work needs to be done along the lines of the Morgan experiment, but the fact that the sensing disc moved in the opposite direction as the driving disc when rapidly accelerating but rather moved in the same direction when rapidly decelerating lends strong evidence of a "Lenz law" type inertial effect here. However, nowadays, no such experimental work can be expected to be published because only those scientists who don't care if their careers are "over" dare attempt to publish any such data that runs counter to the current scientific paradigm due to extremely toxic scientific political correctness.

And, yes, I have sent Jeremy's and my book to Thierry De Mees, but he seems only to be interested in the gravitational part of the theory that we consider to only be half of the story with inertial effects being the other half.

And also thanks for mentioning of the work of J.C. Keith. I will have to look into his work. But gravitational dynamical effects are so very small that it's quite difficult to verify them in small devices in the lab; only cosmic considerations are large enough (such as the "gravity probe" experiments).

God Bless,

Denny

"But gravitational dynamical effects are so very small that it's quite difficult to verify them in small devices in the lab"

Dear Dennis,

rotational dynamic effects in general steeply increase with rotational frequency. Related effects therefore should preferably be detectable on small rotors, see also reference below. Please note that at the investigated maximum speed of 75 kHz gravitational acceleration at the 2.5 mm experimental ball bearing periphery was about 3x108 m/s2.

Dear Johan,

Many thanks for the reply. Yes, all the papers referenced in your work that is attached are prior to 1986. And I'm not sure of what is meant about the gravitational drag effect of Keith's "does not penetrate the compact matter"; gravitational effects are thought by many (including myself) to penetrate compact matter. Keith might better have also considered inertial induction effects in his work as they are not necessarily at odds with "observations of extraterrestrial objects". But the days when data that scientifically politically incorrect can be mentioned by researchers who are not retired are gone, I'm afraid.

God Bless,

Denny

"gravitational effects are thought by many (including myself) to penetrate compact matter."

Dear Dennis,

thanks for your valuable hint. I should admit that my assumption of Keith's gravitational interaction not to penetrate compact matter appears rather questionable. My assumption at that time was an auxiliary one in order to understand what makes the difference between small rotors and and large ones of astronomic dimensions. When considering "transparency" as a characteristic feature of small rotors this erroneously lead me to the above assumption which certainly requires some sort of revision or replacement.

Maybe you will be able to somehow link Keith's ideas with your concept of "inertial induction" ?

Dear Johan,

Many thanks for the thoughtful reply. Yes, I do think that inertial effects and gravitational effects are tied together as are electric and magnetic effects, and so it might well be possible -- as you point out -- to explain these effects of Keith using some kind of a mixture of gravitational and inertial fields but the inertial effects are thought to be much larger (see the last sentence on page 7 and page 8 of Jeremy's and my Part 2), but we have not as yet succeeded in calculating of one key constant so that we are only just speculating here.

But, as I've said before, where are we to get good data to use to calculate our theory constants when the current scientific political correctness is resulting in the getting rid of anyone in academia who would even attempt to publish data this far away from the current paradigms? And the Keith data involves a small ball magnetically suspended, but then electromagnetic theory enters in; and J.P. Wesley in his 2002 book, "Scientific Physics," points out, for example, that the experimental tool of the Marinov (electric) motor actually works but it is not predicted to work using Maxwell's equations (you may vied this motor running on the Internet). So we are starved for data that is not faked and good theory based upon it!

God Bless,

Denny

"explain these effects of Keith using some kind of a mixture of gravitational and inertial fields but the inertial effects are thought to be much larger"

Dear Dennis,

I think your ideas are pointing at something reasonable and worthwhile of being investigated with accompanying experiments.

What fascinates me with the Keith experiment is the huge centrifugal acceleration of 3x108 m/s2 at the spinning ball which according to Mach's principle should be explained as something resulting from interaction with remote masses of the universe, maybe via the local gravitational potential, and which I suppose should cause at least some minute reaction effect on the ball. On page 11 of his paper, see below, Keith states: "It is as if entire reaction force on the universe, a universe which cannot itself react to forces or torques inertially, acted back on the freely spinning mass system causing a real slowing down."

I fully agree and regret what you state about "political correctness" in science which in fact seems to prevent progress in certain fields of basic significance.

Dear Johan,

Many thanks for the reply. Yes, an acceleration of 3 10^8 m/s^2 is awfully large. But, to my way of thinking, the correct way to approach the problem of explaining inertial induction forces is to first work out the case of non-relativistic velocities. My physics mentor, Dr. Thomas E. Phipps, (Harvard 1951) used to say that second order physics cannot be made right until first order physics is made right, and I wholly agree with this. But, some day, this 3 10^8 acceleration must be explained properly; there's no doubt about this.

God Bless,

Denny

"first work out the case of non-relativistic velocities"

Dear Dennis,

I understand the first order counterpart to the relativistic drag proposed by Keith is the well established acceleration force F = m*a that according to Mach's principle also results from interaction with remote masses of the universe.