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#1600 by Mulletron on 15 Sep, 2017 14:22
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My thinking about G isn't unmotivated. This appears to be happening, and in a predictable way. The question is, why? This is worth time and effort. Such a small deviation. Perhaps it's possible to have large deviations? Are we already and just don't understand it? Definitely worth exploring. Interesting comments in the phys.org article about planetary orbital resonances.
https://www.richarddawkins.net/2015/04/why-do-measurements-of-the-gravitational-constant-vary-so-much/
https://m.phys.org/news/2015-04-gravitational-constant-vary.html -
#1601 by meberbs on 15 Sep, 2017 14:32
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This is basically just saying the emDrive doesn't work which is not what anyone understood your original post to mean. Because if this is what is happening there is no way for the emDrive to be a useful thruster (it would rapidly build up positive charge and stop working). There are plenty of ways for the result through now to be explained by experimental errors, however I do not see how it could be functioning as an electron gun. What Bob Wood's posted has its own problems (photons are in the category "boson" and producing massive particles would take too much energy to be useful), but is is very different than what you said in that it is intended to describe a mechanism by which the emDrive would actually be useful.So are you endorsing Shawyer's "theory" here? Because he is the only one who claims the emDrive doesn't need new physics. The countless problems with Shawyer's claims have been thoroughly discussed here.
No, I'm saying no new science or violation of existing science is needed to describe the observations. (Didn't I say that?) There's plenty of theories about what's happening, not just Shawyer's, from dismissal to explanation to claims of new science or heresy. I mentioned it's half-century old science in a new wrapper. Specifically, my money's on it being an exceedingly inefficient electron gun. Bob makes a good argument along similar lines which I've quoted below.How can this (emphasis mine):
Propylox's first statement is wrong. In GR gravitational effects only propagate at the speed of light. This was one of the original reasons it was obvious that a new theory of gravity (GR) was needed after special relativity was developed.According to current theories, gravity is instantaneous - if the Sun blinked out of existence we'd fly off our orbit immediately while light continued shining for ~8min.
be compatible with:But a sudden change in localized mass, and the distortion of spacetime it creates, would propagate at a defined rate.
as the (almost) circular motion of planets around the Sun is due to spacetime being bent by the presence of our star?
In this thought experiment, if spacetime is still deformed locally around the Earth for several minutes after the disparition of the Sun, why would the Earth "immediately fly off its orbit" despite the gravitational potential making its motion circular has not gone yet?As to the merits of the so-called EM Drive; Groundbreaking stuff [/sarcasm] that designers of in-space transmitters should be aware of to avoid unwanted thrust, but really nothing but a parlor trick for the uneducated with zero practical, use - just like maglev trains or a Jacob's ladder.
While I agree that the emDrive likely doesn't work, it is incredibly unhelpful of you to call it "for the uneducated," just after you demonstrated your lack of education about general relativity, and in the same breath as ignoring that maglevs have been tested and are under construction -
#1602 by flux_capacitor on 15 Sep, 2017 14:38
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How can this (emphasis mine):
Propylox's first statement is wrong. In GR gravitational effects only propagate at the speed of light. This was one of the original reasons it was obvious that a new theory of gravity (GR) was needed after special relativity was developed.According to current theories, gravity is instantaneous - if the Sun blinked out of existence we'd fly off our orbit immediately while light continued shining for ~8min.
be compatible with:But a sudden change in localized mass, and the distortion of spacetime it creates, would propagate at a defined rate.
as the (almost) circular motion of planets around the Sun is due to spacetime being bent by the presence of our star?
In this thought experiment, if spacetime is still deformed locally around the Earth for several minutes after the disparition of the Sun, why would the Earth "immediately fly off its orbit" despite the gravitational potential making its motion circular has not gone yet?
That's why I thought, thanks. Maybe Propylox mistaken "the speed of gravity" (so to speak) which is the propagation speed of gravitational waves and "spacetime distortion ripples" limited to c vs inertial reaction forces, which are instantaneous (a difference Dr Woodward insists on).
By the way I've just stumbled upon this 2016 speech of Dr Woodward answering basic questions to laymen, who answers at 1:18:40 a question I asked to Rodal a few days ago:Quote from: Jim WoodwardYou're trying to do what everybody tries to do in this. Since Einstein invented general relativity, there have been a long string of physicists who will come along and try to reinterpret general relativity as a locally gauge invariant relativistic quantum field theory: it's called quantum gravity. You here have been hearing for decades now, nobody's figured out quantum gravity. The reason why they haven't figure out quantum gravity may well be because there isn't any quantum gravity… because
gravity IS the thing in which quantum mechanics exists, and it is not itself quantizable.
Stuff about the EmDrive earlier in the video, at 23m53s. -
#1603 by Rodal on 15 Sep, 2017 15:27
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One of the main reasons for string theory and the search of a unified field theory of general relativity and quantum field theory is due to essential problems that general relativity by itself cannot deal with, for example: what happens at the center of a black hole (general relativity cannot explain this, as it gives a singularity), the black hole information paradox (https://en.wikipedia.org/wiki/Black_hole_information_paradox ) and other important issues that occur in black holes.
Similar criticisms taking place against attempts to solve this problem were present at the time that Einstein presented his theory. For example this is what Tesla reportedly had to say about Einstein's theory and its early followers:
Similar criticism as nowadays erected against string theory: "it is just a mathematical theory." Of course, any attempt to explain what happens inside a black hole (dealing with the the singularity, or the information paradox, for example) will remain "mathematical" until such things can be tested experimentally.
Gravitational waves themselves were considered by Eddington "to travel at the speed of thought" and Einstein himself went back and forth as to whether they were real. It took 100 years for mankind to prove the reality of gravitational waves. It will take generations to be able to experimentally prove the issues that string (M)theory is attempting to tackle.
Black holes is another example, as Einstein himself at times expressed the view that they were a mathematical abomination that could not be real.
By the way, concerning Ernst Mach opinions, this is what Mach himself reportedly had to say about Einstein's theory of relativity and about the existence of atoms !
:
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#1604 by Star One on 15 Sep, 2017 15:32
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New article from IBT.
EmDrive: China claims to have built 'Impossible Engine' that needs no fuelQuoteHuffPost citing a video by China's Central Television state broadcaster (CCTV) reported that the China Academy of Space Technology (CAST) has successfully built a working model.
The CCTV video claimed that not only did a CAST team led by Dr Chen Yue build a fully functioning and working model of this engine but also come up with their own version of the machine.
According to the HuffPost report, Dr Yue's team was able to produce 1.2 millinewtons per kilowatt thrust in vacuum.QuoteAs there is no official announcement from either CAST or the Chinese government on this achievement, so there is no real way to tell if the claims are valid or not.
http://www.ibtimes.co.uk/emdrive-china-claims-have-built-impossible-engine-that-needs-no-fuel-1639524 -
#1605 by WarpTech on 15 Sep, 2017 15:57
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What it implies to me supports what I said years ago; there is a transient affect as the cavity is charging. Once it reaches steady state, there is no thrust.
Hi WT,
Cavity charge time is 5x cavity TC being TC = Q / 2 Pi Freq.
For a 2.45GHz 50k Q the cavity fill time is 162usec.
For Jamie's 5k cavity that reduces to 16.2usec.
Don't see how Jamie's result relates to a 16.2usec cavity fill time.
WarpTech is there something else you have in mind when you say "cavity charging"?
The time derivative of the power dissipation.
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#1606 by flux_capacitor on 15 Sep, 2017 15:59
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One of the main reasons for string theory and the search of a unified field theory of general relativity and quantum field theory is due to essential problems that general relativity by itself cannot deal with, for example: what happens at the center of a black hole (general relativity cannot explain this, as it gives a singularity), the black hole information paradox (https://en.wikipedia.org/wiki/Black_hole_information_paradox ) and other important issues that occur in black holes.
Similar criticisms taking place against attempts to solve this problem were present at the time that Einstein presented his theory. For example this is what Tesla reportedly had to say about Einstein's theory and its early followers:
Similar criticism as nowadays erected against string theory: "it is just a mathematical theory." Of course, any attempt to explain what happens inside a black hole (dealing with the the singularity, or the information paradox, for example) will remain "mathematical" until such things can be tested experimentally.
Gravitational waves themselves were considered by Eddington "to travel at the speed of thought" and Einstein himself went back and forth as to whether they were real. It took 100 years for mankind to prove the reality of gravitational waves. It will take generations to be able to experimentally prove the issues that string (M)theory is attempting to tackle.
Black holes is another example, as Einstein himself at times expressed the view that they were a mathematical abomination that could not be real.
By the way, concerning Ernst Mach opinions, this is what Mach himself reportedly had to say about Einstein's theory of relativity and about the existence of atoms ! :
There is a singularity at the center of a black hole only if one considers a spherical central geometry for this entity and at the same time allowing r to go negative, i.e. to allow an imaginary portion of spacetime where the element of length becomes purely imaginary through analytic continuation.
I am aware this is not the most common view, as the way David Hilbert interpreted Karl Schwarzschild's solution right after his death in 1916 has become the norm. But Schwarzschild originally chose to keep all lengths as real quantities and dealt with a spherical symmetry for what will later become the black hole, not a central symmetry as understood by Hilbert.
This apparent slight difference is important (not at that time though) because a sphere has both a central and a spherical symmetry, but a torus for example has only a spherical symmetry (not a central one, as a torus has no center).
If you make the correct change of variable in Schwarzschild's solution, you obtain a geometry for the black hole without any central singularity, as the geometry describes an uncontractible hypersurface.
In 2D you can imagine a series of parallel spheres. I don't say "concentric" precisely because there is a sphere with minimal radius r, and no sphere has a radius below that value.
You can parse through theses surfaces by foliation. When you reach the minimum surface (at r = 0) and decide to keep going on (down to r < 0) then r grows again. It means you just have passed through a throat surface and are now evolving in a flat Minkowski space. So the black hole is under this view a bridge of limited spatial extension with no central singularity, linking two Minkowski spaces. An idea Hawking himself recently agitated.
According to this, general relativity is all we need even for the black hole. No quantum mechanics.
You can decide to calculate values for r < 0, it can be done mathematically, but according to the idea above, physically it would mean that your are now just outside the hypersurface, as if you wanted to stick a patch on a tire, but in the vicinity of the wheel axis, where there is no tire.
EDIT: REFERENCES
The fundamental difference between the Schwarzschild solution as considered first by its author Karl Schwarzschild, then by David Hilbert (hence according to what is now improperly named the Schwarzschild solution) was first spotted in the scientific literature by American physicist Leonard Abrams (1924–2001) in 1979 and 1989 in [1] and [2], then more recently by Italian physicist Salvatore Antoci in [3] and [4], plus a few other non scientist persons. A historical and mathematical overview summarizing the problem has been recently presented in [5]. The alternative model known as the "leaking neutron star" has been presented in the second part of that publication, not yet available for download.
Salvator Antoci discovered the discrepancy between the Hilbert and the Schwarzschild solutions as he is the person who first translated Karl Schwarzschild"s first [6] and second [7] 1916 papers (the second one is the "interior solution" in an incompressible perfect fluid sphere) from German to English. This has been done only in December 1999, that is to say 83 years after the publication of the paper!
[1] Abrams, L.S. (November 1979). "Alternative Space-Time for the Point Mass". Physical Review D 20 (10): 2474–2479. doi:10.1103/PhysRevD.20.2474. arXiv:gr-qc/0201044.
[2] Abrams, L. S. (2001). "Black Holes: The Legacy of Hilbert's Error". Canadian Journal of Physics 67 (9): 919–926. doi:10.1139/p89-158. arXiv:gr-qc/0102055.
[3] Antoci, S.; Liebscher, D.-E. (2001). "Reconsidering Schwarzschild’s original solution". Astronomische Nachrichten 322 (2): 137–142. arXiv:gr-qc/0102084.
[4] Antoci, S. (2003). "David Hilbert and the origin of the Schwarzschild solution". Meteorological and Geophysical Fluid Dynamics. Bremen: Wilfried Schröder, Science Edition. arXiv:physics/0310104.
[5] Petit, J.-P. (2017) "Mass inversion in a critical neutron star: An alternative to the black hole model – First part" (PDF). 21st annual International Conference on Particle Physics and Cosmology (COSMO-17). Paris: Paris Diderot University.
[6] Schwarzschild, K. (13 January 1916). "Über das Gravitational eines Massenpunktes nach der Einsteinschen Theorie". Sitzungsber. Preuss. Akad. Wiss. Berlin (Phys.-Math.). 189–196
translated in English as:
Antoci, S.; Loinger, A. (12 May 1999). "On the gravitational field of a mass point according to Einstein's theory". arXiv:physics/9905030.
[7] Schwarzschild, K. (24 February 1916). "Über das Gravitationsfeld einer Kugel aus incompressibler Flüssigkeit nach Einsteinsechen Theorie". Sitzungsber. Preuss. Akad. Wiss. Berlin (Phys.-Math.). 424–434
translated in English as:
Antoci, S. (12 May 1999). "On the gravitational field of a sphere of incompressible fluid according to Einstein's theory". arXiv:physics/9912033. -
#1607 by OnlyMe on 15 Sep, 2017 16:02
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It is indeed possible that the dielectric inside the em cavity may emit massive gravitons (a kind of gravitational wave):
http://www.tsijournals.com/articles/directions-for-gravitational--wave-propulsion.pdf
Obviously these gravitons can escape the cavity and provide propulsion.
What's the problem?
WL,
EW data measured:
1.2mN/kW with small end dielectric
3.9mN/kW with NO dielectric
Over 3 times higher specific force was measured without dielectrics inside the cavity. Does that data negate gravitons being involved?
The short answer is no! Because we don't yet know why or what generated the detected force in either case. And this is not intended to suggest that I believe gravitons are involved. Just that we don't have enough information to know what is happening. -
#1608 by as58 on 15 Sep, 2017 16:08
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"Gravity wave" is a misnomer so it's nice you mentioned "space-time ripple", an accurate description. According to current theories, gravity is instantaneous - if the Sun blinked out of existence we'd fly off our orbit immediately while light continued shining for ~8min. But a sudden change in localized mass, and the distortion of spacetime it creates, would propagate at a defined rate. This distortion wave does not transfer momentum, but temporarily effects the distance between objects as it passes them, sometimes enough to draw objects (black holes) together in the same way ripples in a marina can cause boats to harmonize and be drawn together.
You managed to load a lot of wrong in one short paragraph. -
#1609 by Space Ghost 1962 on 15 Sep, 2017 16:09
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According to this, general relativity is all we need even for the black hole. No quantum mechanics.
Mind that for certain dimensions, Cherns Simons works (or doesn't).
You can decide to calculate values for r < 0, it can be done mathematically, but according to the idea above, physically it would mean that your are now just outside the hypersurface, as if you wanted to stick a patch on a tire, but in the vicinity of the wheel axis, where there is no tire.
So the presumptions of foliation topologically matter too. Especially with shearing stress. -
#1610 by Rodal on 15 Sep, 2017 16:25
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...
The problem with the view that
If you make the correct change of variable in Schwarzschild's solution, you obtain a geometry for the black hole without any central singularity, as the geometry describes an uncontractible hypersurface.
In 2D you can imagine a series of parallel spheres. I don't say "concentric" precisely because there is a sphere with minimal radius r, and no sphere has a radius below that value.
You can parse through theses surfaces by foliation. When you reach the minimum surface (at r = 0) and decide to keep going on (down to r < 0) then r grows again. It means you just have passed through a throat surface and are now evolving in a flat Minkowski space. So the black hole is under this view a bridge of limited spatial extension with no central singularity, linking two Minkowski spaces. An idea Hawking himself recently agitated.
...Quotethe black hole is under this view a bridge of limited spatial extension with no central singularity, linking two Minkowski spaces
is
1) proving the stability of such a bridge, which appears unstable unless it contains negative mass-energy
2) the existence of another space is reminiscent of bridges in M-theory's multiverse, there is no experimental proof to decide between different theories (because black holes are...black) -
#1611 by flux_capacitor on 15 Sep, 2017 16:35
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The problem with the view that
Quotethe black hole is under this view a bridge of limited spatial extension with no central singularity, linking two Minkowski spaces
is
1) proving the stability of such a bridge, which appears unstable unless it contains negative mass-energy
2) the existence of another space is reminiscent of bridges in M-theory's multiverse, there is no experimental proof to decide between different theories (because black holes are...black)
Sure, it all boils down to allow either:
- an imaginary time and pure imaginary lengths inside the black hole, "beyond the event horizon" (as usually done)
- or consider that the interior of such a solution is physically (and mathematically) real.
PS : You're right this is unstable, and such solution represents a transient, very short, ephemeral bridge in time. -
#1612 by Rodal on 15 Sep, 2017 16:43
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where is the bridge going into? if it comes back into our own Universe, shouldn't it display the other end of the bridge as a white hole? If so why is there no experimental evidence of such white holes (which should be easier to detect than black holes).The problem with the view that
Quotethe black hole is under this view a bridge of limited spatial extension with no central singularity, linking two Minkowski spaces
is
1) proving the stability of such a bridge, which appears unstable unless it contains negative mass-energy
2) the existence of another space is reminiscent of bridges in M-theory's multiverse, there is no experimental proof to decide between different theories (because black holes are...black)
Sure, it all boils down to allow either:
- an imaginary time and pure imaginary lengths inside the black hole, "beyond the event horizon" (as usually done)
- or consider that the interior of such a solution is physically (an mathematically) real.
PS : You're right this is unstable, and such solution represents a transient, very short, ephemeral bridge in time.
If the bridge goes into another brane, then I don't understand why people would be so much against M-theory and its multiverse of different branes and prefer this theory instead, since both seem to agree on bridges to other branes . -
#1613 by WarpTech on 15 Sep, 2017 16:46
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My thinking about G isn't unmotivated. This appears to be happening, and in a predictable way. The question is, why? This is worth time and effort. Such a small deviation. Perhaps it's possible to have large deviations? Are we already and just don't understand it? Definitely worth exploring. Interesting comments in the phys.org article about planetary orbital resonances.
https://www.richarddawkins.net/2015/04/why-do-measurements-of-the-gravitational-constant-vary-so-much/
https://m.phys.org/news/2015-04-gravitational-constant-vary.html
Using dimensional analysis along with how gravity affects M,L,T. The value of G is not a universal constant. In the PV Model of GR, it is G/c4 that is a universal constant.
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#1614 by RotoSequence on 15 Sep, 2017 16:52
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@Rodal: Do the Brane based theories for Supergravity require Supersymmetry?
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#1615 by Rodal on 15 Sep, 2017 16:54
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This issue was also discussed in scalar-tensor theories starting with Brans-Dicke, but all tests up to now have rather confirmed the universality (in spacetime, to other epochs) of G, and very much narrowed the range in which G could be possible to varyMy thinking about G isn't unmotivated. This appears to be happening, and in a predictable way. The question is, why? This is worth time and effort. Such a small deviation. Perhaps it's possible to have large deviations? Are we already and just don't understand it? Definitely worth exploring. Interesting comments in the phys.org article about planetary orbital resonances.
https://www.richarddawkins.net/2015/04/why-do-measurements-of-the-gravitational-constant-vary-so-much/
https://m.phys.org/news/2015-04-gravitational-constant-vary.html
Using dimensional analysis along with how gravity affects M,L,T. The value of G is not a universal constant. In the PV Model of GR, it is G/c4 that is a universal constant. -
#1616 by Rodal on 15 Sep, 2017 16:57
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@Rodal: Do the Brane based theories for Supergravity require Supersymmetry?
Yes, many of the string theories did, most of the early ones did, others do not. There are more theories than physicists (unfortunately this is the truth)
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#1617 by flux_capacitor on 15 Sep, 2017 17:09
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where is the bridge going into? if it comes back into our own Universe, shouldn't it display the other end of the bridge as a white hole? If so why is there no experimental evidence of such white holes (which should be easier to detect than black holes).The problem with the view that
Quotethe black hole is under this view a bridge of limited spatial extension with no central singularity, linking two Minkowski spaces
is
1) proving the stability of such a bridge, which appears unstable unless it contains negative mass-energy
2) the existence of another space is reminiscent of bridges in M-theory's multiverse, there is no experimental proof to decide between different theories (because black holes are...black)
Sure, it all boils down to allow either:
- an imaginary time and pure imaginary lengths inside the black hole, "beyond the event horizon" (as usually done)
- or consider that the interior of such a solution is physically (an mathematically) real.
PS : You're right this is unstable, and such solution represents a transient, very short, ephemeral bridge in time.
If the bridge goes into another brane, then I don't understand why people would be so much against M-theory and its multiverse of different branes and prefer this theory instead, since both seem to agree on bridges to other branes .
As a first approximation, I'd say: a white hole in another spacetime. But since the subsequent theory allowing this alternative black hole model is a bimetric theory of gravity, this is not about parallel universes or multiverse, but two "separate" metrics in the same universe.
So let's say it's more like a "brane theory" in your example but without the brane, superstring, supersymmetry and all the quantum stuff. Only general relativity. That's the main difference.
That said, the topological core idea underneath (throat surface connecting two spaces without central singularity) may be adaptable to brane cosmology.
But in the model I talk about, this is all about GR. And the bimetric gravity (not at all related to "massive gravitons" which are another kind of bimetric theory of gravity) is all about conjugate geometry, a topological concept where a concentration of matter located in a metric induces an (opposite) curvature in its conjugate metric. I illustrated this concept in the following page:
"Mass inversion process through hyperspace transfer: Conjugate curvatures":
http://ayuba.fr/janus/conjugate_curvatures/
with this animation showing in 2D the transient exchange of matter at the center of a destabilized critical neutron star:
In passing this illustration shows how some "negative mass matter" with negative energy (represented in blue) that would be located in a "negative sector" corresponding to the conjugate metric, would in fact not be intrinsically "negative" all. It would simply be some matter of positive mass, but located in another, conjugate metric. Then, the topology makes this matter "of the other side" acting (felt here) as if it had a negative mass. But it is not the case, fundamentally. Same thing for positive mass matter (in yellow) which induces… a negative curvature in its conjugate sector. -
#1618 by WarpTech on 15 Sep, 2017 17:17
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This issue was also discussed in scalar-tensor theories starting with Brans-Dicke, but all tests up to now have rather confirmed the universality (in spacetime, to other epochs) of G, and very much narrowed the range in which G could be possible to varyMy thinking about G isn't unmotivated. This appears to be happening, and in a predictable way. The question is, why? This is worth time and effort. Such a small deviation. Perhaps it's possible to have large deviations? Are we already and just don't understand it? Definitely worth exploring. Interesting comments in the phys.org article about planetary orbital resonances.
https://www.richarddawkins.net/2015/04/why-do-measurements-of-the-gravitational-constant-vary-so-much/
https://m.phys.org/news/2015-04-gravitational-constant-vary.html
Using dimensional analysis along with how gravity affects M,L,T. The value of G is not a universal constant. In the PV Model of GR, it is G/c4 that is a universal constant.
Since I was referring to the PV Model of GR, where we use a refractive index. The "coordinate" speed of light is given by c/K. Force is an invariant so;
c4/G = (c/K)4/(G/K4)
So G is a variable dependent on the refractive index. In the experiments, they use the "local" frame where "c" is a constant and K=1. Under those conditions, they will not measure a change in G either. This is based on dimensional analysis.
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#1619 by Space Ghost 1962 on 15 Sep, 2017 17:24
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Mind also that the nature of phenomena (e.g. "white"/"black" "holes") do not have to be similar in the form of "observable".
(Have had this argument with Witten in lecture.)
(BTW, the recent proof of the balance of positive/negative infinities also impacts this area. In particular, the shift of physical laws potentially shifting dimensions with low energy to inhospitable/"non life" ones also goes away.)
So many ramifications here. Mind also that transients can also "clean up" COE violations/ruptures/extrusions on closure too.
: