Spacetime Ontology, the Scholarly Debate

[owl]

Imatfaal:

To be clear - that's a no. I understand you have cited experts in earlier sections - but you were claiming a lack of attention to specific arguments, this was one of them that you highlighted - is there no basis for it?

 

That was a 'not on hand immediately', with an "if you insist" I will dig it up. Ok, you insist. Please be patient. I studied it at least five years ago.

I disagree; to claim that uninterest implies a lack of disinterest is a slur - especially when directed at a scientist.

 

Huh? A "lack of disinterest" is interest, not "uninterest." To simplify, again, swansont said that he is not interested in ontology, which this thread is about... like, yet again, "what IS spacetime"... the inquiry/criticism quoted and commented upon in this thread.

Cap 'n R:

 

Nor does an incorrect understanding of the physics of space, time, or spacetime.

 

Asserting that an argument is "incorrect" does not make it incorrect. That would require showing how it is incorrect.

Edited August 9, 2011 by owl

[swansont]

swansont:

 

 

How, again, did you explain what made my argument fallacious? By citing the usual success stories of GR and saying, "GR does."? It was the ontology of spacetime being curved by mass and energy that I was questioning. Is it as mental matrix, a spatiotemporal coordinate system of math/geometry model only being warped or some medium without which masses can not pull on other masses.

 

No, what you asked was

 

Could you give me an example of "how things behave" (say Mercury orbiting the sun... a classic relativity success story) with "spacetime" being curved in contrast to the mutual gravitation between the two bodies without the curved medium, spacetime? What does spacetime curvature add to gravity between them without it?

 

"How things behave" is not ontology. "What does spacetime curvature add to gravity between them without it" is not ontology. I answered THOSE QUESTIONS.

 

I wish I could appeal to a moderator about all of the above, but you are it, and you are not an unbiased, objective scientist in this field of inquiry.

 

Feel free. I am not the only moderator, nor do I act (with rare exception) as one in science/philosophy/politics discussions in which I am involved. If you think I have broken a rule, report the post. Disagreeing with you and pointing out your errors is not an indication of bias or lack of objectivity.

[owl]

Amatfaal,

I could not find the references from many years ago (maybe more like 10 than 5), but here is what I did find plus a final commentary, my own in summary of the missing references.

 

Scientific American

Troubled Probe Upholds Einstein, May 10, 2011

 

(but there is a minority opinion)

 

Others see the complexity of the calculations as a reason to doubt the probe's frame-dragging measurement. "It may be that people repeating this analysis with another working hypothesis on the nature of the systematic errors would get another result," says Ignazio Ciufolini of the University of Salento in Lecce, Italy, who published the results from LAGEOS (I. Ciufolini and E. C. Pavlis Nature 431, 958-960; 2004).

 

PhysForum Science; Hai-Long Zhao's Mass Variance SR Theory:

Article 3. Because real-world mass distribution is inhomogeneous and changes with time, global inertial reference frames do not exist. Instead we have local free-fall reference frames which are the single-body frames...

 

...Because any finite mass or inhomogeneous mass distribution presents gravitational interaction in its neighborhood and affects any measurement ...

 

Article 4. Gravity Probe B involves two reference frames. One is earth and the other is the satellite. In the coordinate description of earth ZFF, the earth gravitational field is Schwarzschild metric form (Lagrangian functional form). Therefore, the geodesic effect and frame-dragging effect concern the angles between the directions of the gyroscopes and the direction of earth ZFF frame. Not the one of guide star.

 

(Note: Just a criticism of a basic assumption of the experiment... another possible source of error.))

 

CNNTech; (standard version of frame dragging verification with my bold and** on the assumed established fact of space and spacetime as a malleable "fabric"... made of what?):

Earth's spin warps space around the planet, according to a new study that confirms a key prediction of Einstein's general theory of relativity.

 

After 11 years of watching the movements of two Earth-orbiting satellites, researchers found each is dragged by about 6 feet (2 meters) every year **because the very fabric of space is twisted by our whirling world.

 

Here's how it works:

 

Any object with mass warps the space-time around it, in much the same way as a heavy object deforms a stretched elastic sheet, explained study leader Ignazio Ciufolini of the Universita di Lecce in Italy.

 

If the object spins, another distortion is introduced, "in the same way as the elastic sheet would be twisted by a spinning heavy wheel on it."

 

If the space around Earth is being frame-dragged, then satellites ought to be caught up in the deformation, scientists reasoned. Imagine how a second object on the elastic sheet would be moved by the scrunching motion created as the sheet is deformed.

 

So here we again have the ubiquitous "elastic (often rubber) sheet" asserted with no thought to or concern about addressing the ontology of what this fabric actually is in the real cosmos.

 

Wikipedia on Frame dragging:

They predicted that the rotation of a massive object would distort spacetime metric, making the orbit of a nearby test particle precess. This does not happen in Newtonian mechanics for which the gravitational field of a body depends only on its mass, not on its rotation.

 

If ‘spacetime' turns out to be a “metric”(just a map) without an ontological referent, as per the decade of ontological study by the ISASS, then another explanation will be required.

Since I can not find the alternative, topographical/density variation explanation I studied many years ago, I will explain it the best I can from memory.

The “Newtonian mechanics” referenced above “depends only on its mass, not on its rotation”... so it is supposed.

But the mass of earth attracting satellites like the above famous “probes” is not a steady pull on the satellites. It varies with the proximity of the probes to high mountain ranges and higher/lower densities of the crust ‘sweeping by’ under their orbit.

 

So the variations attributed to a warped but theoretical medium, “spacetime” could be attributed to such variations in gravitational pull as surface variations pass by the probes.

 

Ps: If I do find my original references, I will share them. Meanwhile I would welcome an explanation of why sweeping differences in earth's gravity can not explain 'frame dragging' just as well as an unexplained and controversial concept, 'spacetime', with a twist.

[Iggy]

I have quoted Kelley Ross in this thread on that point, including what “intrinsic vs extrinsic curvature” applied to different “manifoldes” means in the real world, what a fourth spatial dimension might mean (or not), etc.... what spacetime IS, if anything besides a coordinate system for things traveling through space over time.

I've read the blog you're talking about. It calls relativity a "metaphysically elegant theory" and disagrees with all of your objections to intrinsic curvature.

[imatfaal]

Imatfaal:

Huh? A "lack of disinterest" is interest, not "uninterest." To simplify, again, swansont said that he is not interested in ontology, which this thread is about... like, yet again, "what IS spacetime"... the inquiry/criticism quoted and commented upon in this thread.

 

 

btw disinterest DNE uninterest. a "lack of disinterest" is a bias. SonT said he was uninterested. This does not imply a bias.

 

On the frame-dragging - your quotes are interesting and I had read one of them before. But they do not entertain the notion that frame-dragging is a myth caused by the irregularity of the earth - they worry that the irregularity of the earth, poor experimental accuracy, and excess data manipulation have clouded/influenced the results. Scientists doubt things all the time - and positive results are gone through with the finest of fine tooth combs to check and double-check that the results really do confirm the theory. That is what the reputable sources you quoted are doing - they are saying - yeah the results fit but are they really clear enough; that is a world away from positing an alternative theory.

 

For your guidance a reference request on a science board is normally looking for something other than a post on another science board (especially one from a banned member with 17 posts to their name)! http://www.physicsforums.com/showthread.php?t=165052

[owl]

Just for a break from my frame of reference thread and the challenge to the SR's theory of length contraction, here is a riddle based on GR's claim that gravity curves "spacetime." (Background: based on non-Euclidean geometry/cosmology and Minkowski's and Einstein's formulation of 4-D "spacetime.)

 

Do the planets have circular-ish/elliptical orbits around the Sun or do they travel in straight lines through curved "spacetime?" If the latter, describe the posited curved medium, spacetime and explain why the orbits of the planets themselves appear to be curved.

[owl]

IM Egdall; quote from another thread:

To OWL: You ask what curves in spacetime curvature. The word curvature is a

mathematical term. I believe in this context it means warp or change. Per general

relativity, ihe presence of an object's mass/energy, time and space are warped or

changed.

 

For example, a clock runs slower the closer it is to that object. (Here on Earth, a

clock at lower altitude runs a tiny bit slower than a clock at higher altitude.)

This is time warp.

 

And the distance between two points is stetched in the presence of an object.

(Imagine two points separated in space, one above the other. Now place the Earth

just below these two points. The distance between the points as seen from far away

are now a tiny bit longer.) This is space warp....

 

So spaetime curvature is not a philisophical term, it the real warping or changing

of space and time in the presence of mass/energy.

 

I understand that spacetime curvature is a mathematics/physics/relativity phrase. My philosophical (specifically ontological) inquiry has always been about the nature of time, space, and “spacetime” in the ”real world,”, i.e., what IS it, if anything as an existing entity besides the way it is used conceptually in the 4-D coordinate system developed from non-euclidean geometry and cosmology. In other words what are time and space as used in your phrase “time and space are warped or changed.?”

 

To take your example of “time warp” for instance: I understand that clocks run slower in higher gravitational fields (and at higher velocities.) I do not argue with these facts. I argue that time is simply event duration of physical processes, and that the physical process of clocks “ticking” slower in the above cases does not mean that “something” , time has slowed down or “dilated.” Ontology, after all, investigates what “time” IS.

 

Same with space. Ontology asks “What is it?” that is said to be “stretched” (or contracted) in the language of relativity referring to “length contraction?” My longstanding criticism of the latter is based on the philosophy of realism which contends that the cosmos and all its parts have intrinsic, objective properties and distances between objects which do not depend on the frame of reference from which they are observed. (Cosmos would not change with no observers present.)

 

Your example is a bit different, placing the Earth “under” two points (one above the other) in space.

Ontology would require that your “points in space” be some kind of entities to “exist in the real world”, not just as conceptual/virtual loci, "points" in a coordinate system. So they could be space buoys placed at rest relative to each other. A long ruler could be placed between them. This distance will not fluctuate with frame of reference from which it is observed (according to realism), but “placing Earth” under them would introduce gravity and pull them (now objects with mass) both closer together and closer to earth. I can see no case in which the distance between them would be “stretched” by Earth’s presence.

Edited October 21, 2011 by owl