FLASHBACK: Einstein was right: space and time bend:

[paddoboy]

It's hard to believe that it has been 16 years since GP-B was launched, so putting beyond any reasonable doubt the fact that massive objects with angular momentum, drag the spacetime around with them. Another confirmation of GR;


https://www.theguardian.com/science/2007/apr/15/spaceexploration.universe

Einstein was right: space and time bend
This article is more than 13 years old
Ninety years after he expounded his famous theory, a $700m Nasa probe has proved that the universe behaves as he said. Now the race is on to show that the other half of relativity also works.

Under his name in the Oxford English Dictionary is the simple definition: genius. Yet for decades physicists have been asking the question: did Albert Einstein get it wrong? After half a century, seven cancellations and $700m, a mission to test his theory about the universe has finally confirmed that the man was a mastermind - or at least half proved it.

But this - what is referred to as the 'geodetic' effect - is only half of the theory. The other, 'frame-dragging', stated that as the world spins it drags the fabric of the universe behind it.

Francis Everitt, the Stanford University professor who has devoted his life to investigating Einstein's theory of relativity, told scientists at the American Physical Society it would be another eight months before he could measure the 'frame-dragging' effect precisely.

The early results from Gravity Probe B, one of Nasa's most complicated satellites, confirmed yesterday 'to a precision of better than 1 per cent' the assertion Einstein made 90 years ago - that an object such as the Earth does indeed distort the fabric of space and time.

more at link.....

extract:
Thus the planets orbiting the Sun are not being pulled by the Sun; they are following the curved space-time deformation caused by the Sun. The reason the planets never fall into the Sun is because of the speed at which they are travelling.

According to the theory, matter and energy distort space-time, curving it around themselves. 'Frame dragging' theoretically occurs when the rotation of a large body 'twists' nearby space and time. It is this second part of Einstein's theory that the Nasa mission has yet to corroborate.
MORE AT LINK.....

 

[paddoboy]

The most amazing thing about this successful probe was the incredible tolerances obtained with the manufacture of the gyroscopes.

https://einstein.stanford.edu/
The Extraordinary Technologies of GP-B
To test Einstein's theory of general relativity, Gravity Probe B must measure two minuscule angles with spinning gyroscopes, floating in space. While the concept of Gravity Probe B is relatively simple, carrying out the experiment required some of the most accurate and sophisticated technology ever developed. In fact, scientists and engineers from Stanford, Lockheed Martin, and NASA had to invent over a dozen totally new technologies in order to meet GP-B’s near-zero constraints, because much of the technology required simply did not exist when the experiment was first suggested in late 1959 - early 1960. Einstein, himself once a patent clerk, would have enjoyed reviewing these extraordinary technologies. This section describes the technologies of the four systems that comprise the heart of the GP-B experiment.



World's Most Perfect Gyroscopes


To measure the minuscule angles predicted by Einstein’s theory, the GP-B team needed to build a near-perfect gyroscope—one whose spin axis would not drift away from its starting point by more than one hundred-billionth of a degree each hour that it was spinning. By comparison, the spin-axis drift in the most sophisticated Earth-based gyroscopes, found in high-tech aircraft and nuclear submarines, is seven orders of magnitude (more than ten million times) greater than GP-B could allow.

Gyro Rotors
Three physical characteristics of any gyroscope can cause its spin axis to drift, independently of the general relativity precession predicted by Einstein’s theory:

1. An imbalance in mass or density distribution inside the gyroscope
2. An uneven, asymmetrical surface on the outside of the gyroscope
3. Friction between the bearings and axle of the gyroscope.

This meant that a GP-B gyroscope rotor had to be perfectly balanced and homogenous inside, had to be free from any bearings or supports, and had to operate in a vacuum of only a few molecules. After years of work and the invention of new technologies and processes for polishing, measuring sphericity, and coating, the result was a homogenous 1.5-inch sphere of pure fused quartz, polished to within a few atomic layers of perfectly smooth. In fact, the GP-B gyro rotors are now listed in the Guinness Database of World Records as being the roundest objects ever manufactured, topped in sphericity only by neutron stars.

The spherical rotors are the heart of each GP-B gyroscope. They were carved out of pure quartz blocks, grown in Brazil and then fused (baked) and refined in a laboratory in Germany. The interior composition of each gyro rotor is homogeneous to within two parts in a million. On its surface, each gyroscope rotor is less than three ten-millionths of an inch from perfect sphericity. This means that every point on the surface of the rotor is the exact same distance from the center of the rotor to within 3x10-7 inches.

much more......

 

[Michael 345]

This means that every point on the surface of the rotor is the exact same distance from the center of the rotor to within 3x10-7 inches.

I had marble like that

 

[paddoboy]

In fact, the GP-B gyro rotors are now listed in the Guinness Database of World Records as being the roundest objects ever manufactured, topped in sphericity only by neutron stars.
.

The blue highlighted section is worth considering, particularly with regards to gravity being the universally recognised dominant force.
With regards to the "Guinness Database of World Records as being the roundest objects ever manufactured"
https://einstein.stanford.edu/MISSION/mission6.html#awards

 

[paddoboy]

While GP-B certainly validated the Lense Thirring effect to great accuracies and precisions, it wasn't the first time that this frame dragging was evident. It was first verified in 1998 with the "GRACE" and the Lageos 1 and 11 Satellites...The following is the detailed discovery and verification of this frame dragging.

https://www.nasa.gov/vision/earth/lookingatearth/earth_drag.html

As World Turns it Drags Time and Space
10.21.04


An international team of NASA and university researchers has dramatically improved the accuracy of the first direct evidence that the Earth drags space and time around itself as it rotates. The measurements used the latest gravity models obtained from NASA's GRACE mission.

Image above: The Grace Satellite's Orbit - This image shows the orbit track of the twin GRACE satellites. In one month its track will densely cover the entire globe. The shaded part of the image is night time. The un-shaded is daytime. The names on the image are ground stations from where scientists talk to the satellite. Credit: Univ. of Texas, GRACE Science Data System

The researchers first measured the "Lense-Thirring Effect," predicted in 1918 using Einstein's theory of general relativity, in 1998 by precisely observing shifts in the orbits of two Earth-orbiting laser-ranging satellites. The team used additional observations of the same satellites, combined with a more accurate model of the Earth's gravity field, to yield the new measurement of the Lense-Thirring Effect.

The team was led by Dr. Ignazio Ciufolini of the University of Lecce, Italy, and Dr. Erricos C. Pavlis of the Joint Center for Earth System Technology, a research collaboration between NASA's Goddard Space Flight Center, Greenbelt, Md., and the University of Maryland Baltimore County.

"Our measurement agrees 99 percent with what is predicted by general relativity, which is within our margin of error of plus or minus five percent," said Pavlis. "This is a significant improvement over our 1998 measurement, which had an error margin of plus or minus 20 percent using the best gravitational model available at the time."

Image above: Gravity's Complex Picture and Lageos Satelllite - The relief indicates the deviation of the true gravitational field from that of a perfect spheroid with uniform mass distribution. Red is higher deviation, blue is lower deviation. INSET: The LAGEOS satellite provided the data to test the Einstein theory. The GRACE mission provided the underlying gravitational data. Click on image to enlarge. Credit: Artwork by F. Ricci (Univ. of Roma, "La Sapienza") and I. Ciufolini (Univ. of Lecce), Earth model courtesy of GFZ-Potsdam, Germany.

The researchers observed the orbits of the Laser Geodynamics Satellite I (LAGEOS I), a NASA spacecraft, and LAGEOS II, a joint NASA/Italian Space Agency (ASI) spacecraft.

The research, reported in the journal Nature, is the most accurate direct measurement to date of the Lense-Thirring Effect--a bizarre effect of general relativity, which predicts a rotating mass will drag space around it. The Lense-Thirring Effect is also known as frame dragging.

Frame dragging is like what happens if a bowling ball spins in a thick fluid such as molasses. As the ball spins, it pulls the molasses around itself. Anything stuck in the molasses will also move around the ball. Similarly, as the Earth rotates, it pulls space-time in its vicinity around itself. This will shift the orbits of satellites near Earth.

The measurement is extremely challenging to make because other factors, like changes in the density of the Earth's upper atmosphere, have a much greater effect on satellite orbits than the Lense-Thirring Effect. Additionally, the Earth's gravitational field is not uniform. For example, the mass of a mountain range can tug on a satellite, slightly altering its orbit. The previous measurement was much less accurate than the current work, due to inaccuracies in the gravitational model available at the time.

Image above: ILRS Network Map - This is the map of international laser ranging network stations that collected the LAGEOS satellite data, which were used for this experiment. Click on image to enlarge. Credit: International Laser Ranging Service, Central Bureau/NASA


Data from NASA's Gravity Recovery and Climate Experiment (GRACE) mission allowed for a vast improvement in the accuracy of new models, which made this new result possible. The measurements required the use of an extremely accurate model of the Earth's gravitational field, called EIGEN-GRACE02S, which became available only recently, based on an analysis of GRACE data. The model was developed at the GeoForschungs Zentrum Potsdam, Germany, by a group who are co-principal investigators of the GRACE mission along with the Center for Space Research of the University of Texas at Austin.

"We found the plane of the orbits of LAGEOS I and II were shifted about six feet (two meters) per year in the direction of the Earth's rotation," Pavlis said. "Even if the gravitational model errors are off by two or three times the officially quoted values, our measurement is still accurate to 10 percent or better." Future measurements by Gravity Probe B, a NASA spacecraft launched in 2004, should reduce this error margin to less than one percent. This promises to tell researchers much more about the physics involved.

The team analyzed an 11-year period of laser ranging data from the LAGEOS satellites from 1993 to 2003, using a method devised by Ciufolini a decade ago. The new research around Earth is the first direct measurement of this phenomenon at the five to 10 percent level. It has recently been observed around distant celestial objects with intense gravitational fields, such as black holes and neutron stars.

LAGEOS II, launched in 1992, and LAGEOS I, launched in 1976, are passive satellites dedicated exclusively to laser ranging. Round-trip travel time of laser pulses sent to the satellite from ranging stations on Earth are recorded, enabling scientists to precisely determine the distances between the Earth stations and the satellites. Another NASA mission, Gravity Probe B GP-B), will also make a measurement of the frame-dragging (Lense-Thirring) effect, although with ten times better accuracy than the current LAGEOS result. It will also provide the most accurate measure to date of the warpage of space-time caused by the Earth's mass.



Krishna Ramanujan
Goddard Space Flight Center

 

[paddoboy]

I believe the previous article and the fact that frame dragging was evidenced in the 1990's, and the fact that still the efforts and technological know how, still saw the construction, implementation and launch of GP-B, simply to further the validation of frame dragging, albeit at much higher tolerances.

 

[paddoboy]

So then, we have shown and listed the observational data that shows spacetime does bend, warp, twist, in the presence of matter, yet the question is still asked, is spacetime real. My answer to that is pretty well known here..."A multi dimensional framework within which we locate events and describe the relationships between them in terms of three spatial coordinates and time. The concept of spacetime follows from the observation that the speed of light is invariant. Spacetime allows a description of reality that is common for all observers in the universe, regardless of their relative motion. Intervals of space and time considered separately are not the same for all observers." So yes, I see it as real. But I thought I would get a more reputable professional thought on the matter after some resounding nonsensical nonsense in the fringes....Notable phrases have been highlighted by me.......
https://www.quora.com/Is-spacetime-a-real-thing-or-just-a-mere-concept
Question:Is spacetime a real "thing" or just a mere concept?
Vesselin Petkov, PhDs Physics & Philosophy Theoretical Physics & Philosophy of Science, Concordia University, Montreal (1997)
Answered November 15, 2017 · Upvoted by Braxton Boren, M. Phil. in Physics, University of Cambridge
This is another deep question whose answer is neither easy nor trivial. This question (and its implications) is a major research project at the Minkowski Institute. There are two reasons for that: first, because it was Hermann Minkowski (Einstein's mathematics professor) who discovered the spacetime structure of the world (Henri Poincaré, who publish the result, before Minkowski, that the Lorentz transformations are rotations in a four-dimensional space with time as the fourth dimension, believed that that space was merely a convenient mathematical space); second, I think avoiding to face the issue of the reality of spacetime might turn out to be the main reason for no breakthrough in fundamental physics (as revolutionary as the theory of relativity and quantum mechanics) in the last several decades.

I will use part of my answer to another question because I think its place is precisely here.

Minkowski, who introduced and developed the physics of (flat) spacetime, explained in his 1908 lecture Space and Time that spacetime represents a real four-dimensional world (Minkowski called it die Welt, i.e., the world).

Let me stress it as strongly as possible - Minkowski's arguments that the world is four-dimensional with time as the fourth dimension, when closely examined look indeed irrefutable, because the experiments that confirmed the kinematical relativistic effects would be impossible if those arguments were wrong and spacetime was nothing more than a mathematical space - see "The world is four-dimensional - Hermann Minkowski's irrefutable proof".

Einstein's initial reaction to Minkowski's view of spacetime and the associated with it four-dimensional physics (also introduced by Minkowski) was not quite favourable: "Since the mathematicians have invaded the relativity theory, I do not understand it myself any more."

However, later Einstein adopted not only Minkowski's spacetime physics (which was crucial for Einstein's revolutionary theory of gravitation as curvature of spacetime), but also Minkowski's world view as evident from Einstein's letter of condolences to the widow of his longtime friend Besso: "Now Besso has departed from this strange world a little ahead of me. That means nothing. People like us, who believe in physics, know that the distinction between past, present and future is only a stubbornly persistent illusion."

For those who wonder how we could perceive that time flows, if all events of spacetime are not objectively divided into past, present and future since they exist equally, here is Hermann Weyl's explanation (which does raise the question of the nature of consciousness, but nevertheless it is the only meaningful explanation):

"The objective world merely exists, it does not happen; as a whole it has no history. Only before the eye of the consciousness climbing up in the world line of my body, a section of this world "comes to life" and moves past it as a spatial image engaged in temporal transformation."
:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::

I have selected what I see as the best answer to that question. There are quite a few other answers, which all bar one [that one answer fails to give any credentials] agree more or less with the answer I quoted.

 

[paddoboy]

Here is that irrefutable proof of the reality of spacetime.......

http://www.minkowskiinstitute.org/MinkowskiProof.html
The world is four-dimensional - Hermann Minkowski's irrefutable proof:

Note 1: The main reason for using the expression "irrefutable proof" is that experiments would be impossible if it were wrong - see below.
Note 2: The strong formulation of this piece of foundational knowledge ("irrefutable proof") might look to some colleagues not sufficiently "politically correct." Although the reason for choosing this formulation seems quite transparent - to invite and even provoke colleagues to challenge the proposed piece of foundational knowledge - it is worth saying two more things:

• The other reason for using the expression "irrefutable proof" (in addition to the main reason - experiments would be impossible if it were wrong) is that for over 100 years Minkowski's arguments for taking seriously the spacetime structure of the world (discovered by him) have been merely ignored, which is truly inexplicable because we all know that if we have an argument particularly in science and especially one having potentially huge implications for fundamental physics and for an adequate view of the world, we face it, not ignore it (what is presently adopted is only Minkowski's four-dimensional mathematical formalism of spacetime, but not the reality of what this formalism represents*). So, we should ask ourselves explicitly: ``Shall we do our best to try to resolve the issue of the reality of spacetime, firmly on the basis of the relativistic experimental evidence, or its resolution should be left to the next generations?
  
  
  
• Here it is worth reminding that misusing "political correctness" in science might have far reaching consequences - as serious as even hampering the advancement of fundamental physics (clearly, "political correctness" has nothing to do with the defining features of civilized discussions - politeness and mutual respect). There has been a growing concern among physicists that some kind of "political correctness" might have something to do with recent attempts to argue that experimental verification is not always necessary for accepting a physical theory (?!) (see, for example: Scientific method: Defend the integrity of physics).

* What appears to be a real problem in physics is that some physicists regard physical theories as nothing more than mere descriptions (which ultimately implies that they do not represent anything in the external world) and therefore issues such as the reality of spacetime are regarded as belonging to philosophy?! That is hardly physics at its best because it is only physics that can adequately address and determine the dimensionality of the world.


much more at link.......

 

[Xelasnave.1947]

Here is that irrefutable proof of the reality of spacetime.......

I often wonder however if it reflects reality..great model but I do wonder about what particles construct space time..I wonder how space and mass communicate..I mean there must be something physical...there must be something like an ether, even though the model does not need it and even if MM tells us there is none.

I suppose a quantum theory of gravity will use particles ... Anyways thanks again for posting this sort of thing I always enjoy it...and you do know I have become very lazy as I now expect if there is anything interesting I will find that you have posted and so I rarely visit say Science Daily as often as I once did.
There are no doubt a lot of people very happy you keep your posts coming.
I would love to be able to discuss science but really not qualified but also there is usually nothing to discuss..it is as laid out so what's to discuss...most times.
Alex

 

[paddoboy]

I often wonder however if it reflects reality..great model but I do wonder about what particles construct space time..I wonder how space and mass communicate..I mean there must be something physical...there must be something like an ether, even though the model does not need it and even if MM tells us there is none.

I suppose a quantum theory of gravity will use particles ... Anyways thanks again for posting this sort of thing I always enjoy it...and you do know I have become very lazy as I now expect if there is anything interesting I will find that you have posted and so I rarely visit say Science Daily as often as I once did.
There are no doubt a lot of people very happy you keep your posts coming.
I would love to be able to discuss science but really not qualified but also there is usually nothing to discuss..it is as laid out so what's to discuss...most times.
Alex

Thanks once again for the appreciation Alex....
Have you checked out the quora link? Some interesting answers and interpretations, and as I said, all basically adding up to the same thing, bar one, who failed to list credentials.

With your ether comment, I would ask, could spacetime itself be inferred as the ether? If one feels the need. Why not, I ask?

 

[Q-reeus]

I believe the previous article and the fact that frame dragging was evidenced in the 1990's, and the fact that still the efforts and technological know how, still saw the construction, implementation and launch of GP-B, simply to further the validation of frame dragging, albeit at much higher tolerances.

The so-called 'frame-dragging' aka Lense-Thirring effect is imo given a much more consistent explanation in terms of gravitomagnetism (more generally, gravitoelectromagnetism or GEM) here:
https://en.wikipedia.org/wiki/Frame-dragging#Effects

The writer correctly points out there should be no 'dragging of space' (and time??? what would that even mean?) observed if a plumb-bob is suspended from a stationary (wrt the distant stars) platform hovering above the equator of a spinning spherical mass. It will point directly towards the gravitational center and not be deflected as would be expected if a 'space dragging gradient' existed in accordance with the 'space as molasses' notion. All the 'dragging of space' effects are explainable as being dynamically induced analogous with electric charge motion in a normal magnetic field.

The problem becomes sharp if the linear counterpart is considered. According to the 'space dragging' interpretation, space should be dragged exterior to and within the interior of a very long cylindrical tube of matter, in uniform rectilinear motion along it's axis of symmetry, wrt to a given inertial frame S. Hence a test mass, held stationary within the tube interior, then released in S, should gradually pick up speed until eventually having the same velocity as the tube. That is the only 'logical' conclusion if 'dragged space' acts like some kind of wind. Yet if true that would undermine the fundamental relativistic axiom of no preferred rest frame. Won't happen according to the gravitomagnetism pov. The released test mass remains stationary. In fact, unlike exterior to the tube, any arbitrary velocities of the test mass is oblivious to the tube relative motion. Only if the tube accelerates along it's relative motion axis would an induction field act to axially accelerate the interior located mass, again in analogy to the EM case E = -∂A∂t.
Experimentally deciding that situation one way or the other may never be possible, but imo without any real doubt the GEM pov is the correct one. That the usual GEM equations:
https://en.wikipedia.org/wiki/Gravitoelectromagnetism
, are only strictly valid in the weak gravity limit is moot.

As for the 'irrefutable proof' given in http://www.minkowskiinstitute.org/MinkowskiProof.html, and linked to in #7 & #8, methinks that author is on a crusade. It's true Einstein fully embraced Minkowski's 4D vision to the extent of being convinced of the ultimate fatalist block-universe position. Where both the past and infinite future is fully and rigidly decided and all just 'there'. Spacetime is 'real' to the extent it successfully provides a mathematical framework that accounts for experiment and observation. The majority position on that which is mine also.

 

[paddoboy]

T
Experimentally deciding that situation one way or the other may never be possible, but imo without any real doubt the GEM pov is the correct one. That the usual GEM equations:
https://en.wikipedia.org/wiki/Gravitoelectromagnetism
, are only strictly valid in the weak gravity limit is moot.

You are entitled to your opinion of course, but I do find it strange that you say being only valid in the weak gravity field is moot.
On my limited understanding of the gravitoelectromagnetism effect, I do find it analogous to GR, GR though seems far more applicable in wider applications. And probably other models also give analogous predictions as GR also, but just as obviously none, imo, surpass GR. Here are some more links......https://en.wikipedia.org/wiki/Gravitoelectromagnetism https://en.wikipedia.org/wiki/Talk:Gravitoelectromagnetism#Dispute

As for the 'irrefutable proof' given in http://www.minkowskiinstitute.org/MinkowskiProof.html, and linked to in #7 & #8, methinks that author is on a crusade.

I find your "crusade"accusation a touch strong, and really only applicable to one or two religious fanatics I have had the pleasure of crossing swords with. We all have our biases though, or agendas for that matter. As an interested amateur party in science, cosmology and associated sciences in particular, my own view is that logically, the vast majority is more certain of being correct and closer to the truth, and couple that with obvious testing and retesting of GR every day, and the fact that many young up and comer science students would dearly love to improve on, or falsify the great man, I find any talk of conspiracy to wrongly maintain the status quo as being very highly unlikely.
By the same token, any potential model claiming improvement on, or invalidating GR, most certainly needs to run the gauntlet so to speak.

It's true Einstein fully embraced Minkowski's 4D vision to the extent of being convinced of the ultimate fatalist block-universe position. Where both the past and infinite future is fully and rigidly decided and all just 'there'. Spacetime is 'real' to the extent it successfully provides a mathematical framework that accounts for experiment and observation. The majority position on that which is mine also.

Nice. Like I have often said to a troll I often cross swords with, something need not be "physical"to be real. I suppose that oft used terminology, "the fabric" of spacetime maybe at fault.
Frame Dragging, gravitational lensing, etc, all attest to that reality of spacetime.

 

[Xelasnave.1947]

Have you checked out the quora link?

Yes I was thinking aloud is all.

With your ether comment, I would ask, could spacetime itself be inferred as the ether?

The answer is yes I expect... it is a model of reality and what reality involves may be beyond a reasonably simple description ...what is in space? There must be much going on ...I find it difficult to imagine ... Still I try.
Alex

 

[Q-reeus]

You are entitled to your opinion of course, but I do find it strange that you say being only valid in the weak gravity field is moot.
On my limited understanding of the gravitoelectromagnetism effect, I do find it analogous to GR, GR though seems far more applicable in wider applications. And probably other models also give analogous predictions as GR also, but just as obviously none, imo, surpass GR. Here are some more links......https://en.wikipedia.org/wiki/Gravitoelectromagnetism https://en.wikipedia.org/wiki/Talk:Gravitoelectromagnetism#Dispute

I find your "crusade"accusation a touch strong, and really only applicable to one or two religious fanatics I have had the pleasure of crossing swords with. We all have our biases though, or agendas for that matter. As an interested amateur party in science, cosmology and associated sciences in particular, my own view is that logically, the vast majority is more certain of being correct and closer to the truth, and couple that with obvious testing and retesting of GR every day, and the fact that many young up and comer science students would dearly love to improve on, or falsify the great man, I find any talk of conspiracy to wrongly maintain the status quo as being very highly unlikely.
By the same token, any potential model claiming improvement on, or invalidating GR, most certainly needs to run the gauntlet so to speak.

Nice. Like I have often said to a troll I often cross swords with, something need not be "physical"to be real. I suppose that oft used terminology, "the fabric" of spacetime maybe at fault.
Frame Dragging, gravitational lensing, etc, all attest to that reality of spacetime.

You don't understand. GEM as used in #11 is not presented as some rival theory to GR, but a (commonly used) way of interpreting it's behavior. I have shown via the linear counterpart that the popularly used notion of 'dragged space' - which you wholeheartedly embrace, is outright inconsistent with the fundamental axiom of no preferred rest frame in relativity.
Instead, matter in relative motion generates a physically real and distinct gravitomagnetic field. Analogous to the EM case of moving charge. And which unlike 'dragged space(time)' notion, is consistent with that fundamental relativistic axiom - no preferred rest frame. 'Moving/dragged space' was shot down way back via Michelson-Morley.

Feel free to email any number of GR authorities and ask for their feedback on my unedited #11 and #14, and reproduce here (with their permission) in full.

 

[paddoboy]

Yes I was thinking aloud is all.

But some interesting answers there.

The answer is yes I expect... it is a model of reality and what reality involves may be beyond a reasonably simple description ...what is in space? There must be much going on ...I find it difficult to imagine ... Still I try.
Alex

Yep, when such reality as observational data showing spacetime to be warping, curving, twisting etc, I fail to understand, any blanket, no it's not real. Like you said, the successful model, models reality or what we see.

 

[paddoboy]

You don't understand. GEM as used in #11 is not presented as some rival theory to GR, but a (commonly used) way of interpreting it's behavior. I have shown via the linear counterpart that the popularly used notion of 'dragged space' - which you wholeheartedly embrace, is outright inconsistent with the fundamental axiom of no preferred rest frame in relativity.
Instead, matter in relative motion generates a physically real and distinct gravitomagnetic field. Analogous to the EM case of moving charge. And which unlike 'dragged space(time)' notion, is consistent with that fundamental relativistic axiom - no preferred rest frame. 'Moving/dragged space' was shot down way back via Michelson-Morley.

Feel free to email any number of GR authorities and ask for their feedback on my unedited #11 and #14, and reproduce here (with their permission) in full.

No, I understood alright. I had another once telling me that another way of interpreting expanding spacetime is "shrinking rulers".

 

[Xelasnave.1947]

What do we find in a cubic metre of space time in the middle of any of our mega voids is something that I wonder about.

I conclude you must find a little piece of everything from everywhere in the universe...well the observable universe...then I think about how the whole thing remains connected...then I fall asleep and dream of falling apples.

Alex

 

[Q-reeus]

But some interesting answers there.

Yep, when such reality as observational data showing spacetime to be warping, curving, twisting etc, I fail to understand, any blanket, no it's not real. Like you said, the successful model, models reality or what we see.

Maybe a good idea if you had started by tightly defining any distinction between 'real' vs 'purely mathematical' nature of spacetime. I have seen too many threads extend for many pages simply because agreed upon and meaningful definitions were never adopted at the outset or subsequently.

 

[Q-reeus]

No, I understood alright. I had another once telling me that another way of interpreting expanding spacetime is "shrinking rulers".

I know who you are referring to and ironically for you that individual believes in an ether theory. Expanding space in the cosmological context has no connection to what is tackled in #11 & #14. Chalk and cheese. You do recall that afaik till this thread you consistently and vehemently rubbished any notion of an ether? Why the change of mind?

Personally, I still consider LET (suitably modified to conform to the cosmological principle) to be conceptually superior to SR, while acknowledging there is no way to detect any underlying (locally) preferred frame. And that's the crucial point of distinction with 'dragged space' notion promoted this thread - the latter implies there are preferred frame effects owing to 'moving space' generated by moving matter. No. Space is not some kind of atmosphere. There is no 'wind' experienced that somehow 'drags objects along' like in a hurricane. GEM pov explains it all consistently.

 

[paddoboy]

I know who you are referring to and ironically for you that individual believes in an ether theory. Expanding space in the cosmological context has no connection to what is tackled in #11 & #14. Chalk and cheese. You do recall that afaik till this thread you consistently and vehemently rubbished any notion of an ether? Why the change of mind?

No actual change of mind, just a passing thought [one I mentioned with that person] as to the possibility of spacetime being inferred as ether. And as I mentioned with Alex.....

With your ether comment, I would ask, could spacetime itself be inferred as the ether? If one feels the need. Why not, I ask?

I don't believe it takes away from the main aspect of GR...while certainly a non physical framework [which I have described with my own definitions] it can still be curved, warped, twisted, waved etc and the same observation that the speed of light is invariant is not comprimised. As far as I can see. But I am still with the status quo.