Q-reeus
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Posts posted by Q-reeus
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12 minutes ago, Strange said:
So your main point is that:
QuoteOn 11/29/2018 at 9:22 PM, Q-reeus said:GR is an inconsistent hodgepodge where ad hoc procedures give the appearance of a coherent whole.
Then the thread appears to be in the right place.
No. That was merely an overall opinion, excised by you and without any greater context, not a specific line of argument (which WAS given in various posts in various ways). OBVIOUSLY.
12 minutes ago, Strange said:Which is why you said absolutely nothing at all about it.
I'll add a bit more. Down to -1 as of this post. Now have a much better idea of the general climate here at ScienceForums, and what tactics are typically employed by some. Have a nice day.
12 minutes ago, Strange said:0 -
32 minutes ago, Strange said:
Report the post with your question and maybe someone will tell you. Or maybe not.
Whoever made the decision to move this thread here obviously has monitored it beforehand. Moving it was a public act. I'll wait some and see if I get a publically viewable response here in this thread. If none comes, then further action my part would be pretty pointless. Silence is a message in itself.
32 minutes ago, Strange said:And the point of that claims is, what, exactly?
Yet again? Combine for instance my very first post this thread with the last main para in this post (dammit, why no post numbering here?):
https://www.scienceforums.net/topic/117191-doubts-about-gr-split-from-exclusive-grave-doubts-over-ligo’s-discovery-of-gravitational-waves/?do=findComment&comment=1083090
Or last part this post:
https://www.scienceforums.net/topic/117191-doubts-about-gr-split-from-exclusive-grave-doubts-over-ligo’s-discovery-of-gravitational-waves/?do=findComment&comment=1082944
Various other posts have covered it, but how many ways of pointing out the same basic issue is needed?0 -
42 minutes ago, Strange said:
I don't know.
I stopped following this thread because I have no idea what your point is. You seem to be saying that GR is wrong (in a very roundabout and incoherent way) in which case, Speculations is the right place for it.
If you want to clarify what your point is exactly and then report that post, perhaps it would be reconsidered.
After all the posts so far, best you can figure is I seem to be saying sort of incoherently that GR is wrong somehow?
Wow. Then this thread has evidently run it's course. Given I have imo spelled out perfectly well enough what ails GR re 'gravity' gravitates' or rather not, and how that then conflicts with the assumed always valid stress-energy-momentum continuity relation. Enough of repeating myself on that, to no good effect here.But I still expect an answer as to who had a hand in booting it here, and exactly on what grounds. I have made my case on that much quite clear. And expect nothing less back from those involved in it being in Speculations.
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Quote
Speculations Forum Rules
The Speculations forum is provided for those who like to hypothesize new ideas in science. To enrich our discussions above the level of Wild Ass Guesswork (WAG) and give as much meaning as possible to such speculations, we do have some special rules to follow:
Speculations must be backed up by evidence or some sort of proof. If your speculation is untestable, or you don't give us evidence (or a prediction that is testable), your thread will be moved to the Trash Can. If you expect any scientific input, you need to provide a case that science can measure.
Be civil. As wrong as someone might be, there is no reason to insult them, and there's no reason to get angry if someone points out the flaws in your theory, either.
Keep it in the Speculations forum. Don't try to use your pet theory to answer questions in the mainstream science forums, and don't hijack other threads to advertise your new theory.The movement of a thread into (or out of) Speculations is ultimately at the discretion of moderators, and will be determined on a case by case basis.
Which above quoted is what one (currently) reads when pressing on link https://www.scienceforums.net/forum/29-speculations/#elForumRules
[Edit: Oh well, turns out copying and pasting 'direct link' to Speculations Forum Rules only results in Speculations main page. One has to then click on that 'direct link' to bring up the Forum Rules box. So weird.]
Hmm... I will ask again - who had a hand in booting this thread from Physics/Astronomy and Cosmology, to Speculations?
What exactly is the notional objective criteria for doing so, in light of above reproduced Forum Rules re Speculations sub-forum? Where is there any hint of a hypothesized 'new idea/theory' being promoted, as opposed to what is obviously true to me - a straight out disagrement over the basic character and implications of an established theory, namely classical GR? That other theories were incidentally and occasionally referred to in passing, but never promoted as 'fact' or made a focus, seems also too obvious to deny.
Or do I simply have to meekly accept that 'discretion of moderators' is the be all and end all of this decision?0 -
1 hour ago, Conjurer said:
The expansion of space or dark energy hasn't been shown to be conserved with anything in physics. If energy conservation of dark energy was even going to be remotely possible, then things should lose energy when dark energy is added to the system. If things didn't lose energy from dark energy, then dark energy would be free energy. If it isn't free energy, then things would naturally lose energy from it occurring. The problem is that there is no theory that links dark energy with other energy in a system.
Wrong. For instance Philip Gibbs is well known as arguing a zero-energy universe that includes all forms of matter-energy including so-called DE:
https://www.quora.com/How-is-the-zero-energy-universe-hypothesis-compatible-with-the-accelerating-universe/answer/Philip-Gibbs-1?share=10 -
16 minutes ago, beecee said:
Why your obsession with the other forum and your manufactured lies? Unlike you, I do learn...and I learn from the experts and professionals....certainly not from those at the level of conspiracy nuts.
You learned from me over there, having made the fool error of hanging onto Schneibster's coat-tails, thinking he was an 'authority figure'. Until his exposed ignorance, of both SR and GR, which I had a major part in revealing, led to his crashing and burning. But of course you'd rather forget such things. I don't.
As for supposed 'manufactured lies' - what lies exactly? Either put up or shut up. And btw, your repeated reference to extraneous issues SHOULD count as violation of forum rules - I would expect anyway. Let's see if any mods pick you up on that repeated abuse.
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Could someone in the know tell me who exactly had a hand in having this forked thread booted to Speculations?
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25 minutes ago, beecee said:
Bingo! Or to put that more simply, a photon has no rest frame so we are unable to speak of how the universe is observed from that pseudo frame.
Bingo huh. Yet over at that other forum, your understanding was as for studiot's earlier here. And I was the one to straighten YOU out then. Well at least that much you have retained here.
Incidentally, too late to edit it now, but I should have wrote '...universe of zero longitudinal thickness.' in my last post So this post affords that chance to 'edit it'.
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8 minutes ago, beecee said:
I do not believe if that did happen it would change your skewered view of GR, and GW's one little bit.
Not sure how many times now you have threatened that you are done.....
Again, let me repeat myself and as I have asked you here and elsewhere, with regards to your crusade, if you believe the errors and misinterpretations of your generally unsupported claim, then write up a professional paper, in a professional manner, for professional peer review. But Hey! wait! All the professional peer reviewers would be like the experts here and simply recalcitrant to your hypothetical unevidenced ideas, correct?
Stop trying to tell me what do - GR fanboy. Remember - this is a FORUM. People are free to post thoughts as they see fit. You don't even understand SR let alone anything significant in GR. As evidenced many times at that other site.
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10 hours ago, swansont said:
Interesting you did not point to the introduction, where you can find
The most important complication we must deal with is that the Einstein equations are non-linear. Physically this is because the source of gravity is mass-energy; but the gravitational field carries potential energy. Thus gravity can be its own source: nonlinearity.
This is based on your claim that gravity is not a source of gravity. But two sources you have provided, and other sources other people have provided, say the opposite.
So I need to repeat - nonlinearity is NOT equivalent to 'gravity gravitates'! What you are suggesting is that PeterDonis's clear exposition of why gravity does NOT gravitate in classical GR is wrong, and further that he continually contradicts himself. Not in that particular exposition. Later, he does fall into the trap of using a common pseudo tensor type approach that as I have said, skirts that 'gravity does not gravitate in classical GR' finding. And yes that then does lead to self-contradictory predictions. Which is what I have picked up on here.
That such skirting the basics in EFE's is very widespread in GR community gives it a weight of authority you and others here evidently find compelling. That's imo at heart a sociological issue not actual physics.10 hours ago, MigL said:Speaking of cherry picking...
Did you read the part where he mentions special 'interpretation' of the Einstein Field Equations ?
The simple fact that there are no gravitational terms on the stress-energy side of the equations does not mean that there is no contribution to the curvature metric ( right side ).
The curvature side is gravity, and the generally accepted interpretation is that it contributes to itself.
Otherwise, as he also explains, there could not be vacuum solutions.You are quibbling over the INTERPRETATION of the model used to describe the reality.
Certainly there can be no quibbling over the actual reality.So you say. See my reply to swansont last
post. (Oh gawd, this system insists on merging my posts - even when I logged out, then back in again to try and beat that feature!)If perchance there is someone else here at ScienceForums who understands GR and would like to make a fresh contribution, I would likely engage. Otherwise, it's very clear where the current lot of posters each stand. In my view, it's a pointless time-wasting exercise to keep up this circular circus act. I'll cut and paste my very brief position, from last post of mine:
A brief recap. In say a binary merger -> GW's. The two supposedly mutually compatible GR relations div T_μν = 0, and R_μν = 0 (in vacuo), are not. I tire of repeating why. It's all been written earlier. Retention here is atrocious probably owing to innate faith in GR. Hence an unwillingness to seriously countenance anything casting doubt on it. Especially if it's simple, basic in character.
That's it. I'm done with going in circles on this. Let's stop this not-so-merry-go-round now.
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4 hours ago, studiot said:
Have you never heard of a hypothetical thought experiment?
If not then just calculate (do the transformation - you do dance?) from the photon's point of view.
There can be no such thing as 'a photon's pov' i.e. 'in the rest frame of a photon'. The more you try and catch up to a photon i.e. head in it's direction of propagation, the more it redshifts in energy. In accordance with E = hf. Ignoring even that regardless of one's boost in that direction, it's still moving at c relative to you, the photon would redshift out of existence in the hypothetical sci-fi case you also 'caught up' and thus also moved at c. It's notional wavelength goes to infinity. An infinitely diffuse, zero energy phantom. In a universe of zero lateral extent. Bizarre enough? Got it?
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1 hour ago, swansont said:
But here’s the punch line: as a massless, spin-two field, gravity not only couples to all the other “matter” fields; it also couples to *itself*. Its field equation, both in the quantum version *and* in its classical limit, the EFE, is nonlinear. At the quantum level, this means gravitons (the quantum particles associated with the massless, spin-two field) interact with other gravitons. At the classical level, it means that, since the EFE is nonlinear, curvature can be present even when the “source” on the RHS of the EFE is zero, i.e., there can be vacuum solutions of the EFE that have curvature present. (Schwarzschild spacetime is an obvious example.) In other words, on this view, the answer to our question is “yes”: gravity *does* gravitate!
It’s important to note that there is no contradiction between the two answers we have just described. “Gravity” in the two answers means two different things: gravity as a massless, spin-two field (either quantum or classical) does gravitate (the field interacts with itself), but gravity as a tensor satisfying the Bianchi identity doesn’t gravitate, because there is nothing “left over”, once the Bianchi identity is satisfied, to contribute to the source on the RHS of the EFE.
I'm not sure what your actual overall position is. But, see above.
The only logical way to interpret that first passage that doesn't conflict with the later one is to realize PeterDonis is being a bit loose with language.
'Curvature present' need not imply such curvature is itself a source of gravitation. Weyl curvature is source free but is nevertheless a type of curvature. It's only Weyl curvature that exists in exterior Schwarzschild solution. It's non-linear in character but not thereby a violation of R_μν = 0 (in vacuo) - the Ricci curvature is zero there.QuoteIs sounds like that because of the way he explained it. The "nothing left over part" and that equations being nonlinear.
So it can be neglected at lower values. I don't see why that's a big deal here.
You complain that something isn't present, although it is, and also note that in most cases it's too small to account for. I don't understand what your actual objection is.
'It' i.e. gravity gravitating is not present at all within classical GR! As above covered, and indeed the point made in almost every other post I have made here. Why confuse things by adding in speculative considerations of a speculative quantized version of GR in its high energy regime?
QuoteWhere is the prediction wrong? How would this be evidence against GR?
You mentioned this, but have not actually explained why it's allegedly a problem.
But I have, beginning with the very first post here.
A brief recap. In say a binary merger -> GW's. The two supposedly mutually compatible GR relations div T_μν = 0, and R_μν = 0 (in vacuo), are not. I tire of repeating why. It's all been written earlier. Retention here is atrocious probably owing to innate faith in GR. Hence an unwillingness to seriously countenance anything casting doubt on it. Especially if it's simple, basic in character.
PS - I note my score has gone from +2 to +3 and back to 0. Pissed someone off. Too bad. Unlike one here in particular, I don't covet such approval rating tokens.
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3 hours ago, MigL said:
From your own link ( to the other Physics Forums ), this is what PeterDonis said...
"At the quantum level, this means gravitons (the quantum particles associated with the massless, spin-two field) interact with other gravitons. At the classical level, it means that, since the EFE is nonlinear, curvature can be present even when the “source” on the RHS of the EFE is zero, i.e., there can be vacuum solutions of the EFE that have curvature present. (Schwarzschild spacetime is an obvious example.) In other words, on this view, the answer to our question is “yes”: gravity *does* gravitate!"
Maybe you should read what you link to.
Sigh !Who's wasting whose time here ?
Reference https://www.physicsforums.com/insights/does-gravity-gravitate/
Nice try at cherry picking there MigL. Omitted from above quoted are these two preceding paras:
QuoteHilbert’s answer (and Einstein’s, when he saw Hilbert’s work) was basically that the action SG is the simplest possible action for gravity that is not trivial. However, in the late 1950’s and early 1960’s, a different approach was developed, based on trying to treat gravity as “just another quantum field”, like the electromagnetic field and all the other fields that were then being studied. I won’t go into too much detail about this, but the upshot was that the quantum field theory of a massless, spin-two field on a flat spacetime background, when made self-consistent, turns out to have as its classical limit the Einstein-Hilbert action SG ! (The “massless, spin-two” part comes from the fact that only a massless field can give rise to a long-range interaction, which gravity is, and only a spin-two field can give rise to an interaction which is always attractive *and* couples to all the other known “matter” fields.)
In other words, on the “gravity as just another quantum field” view, classical GR is just a low-energy effective field theory; it is what you get when gravity is too weak for its quantum nature to show up. (Don’t be misled by that “too weak”, btw; in the sense of the term used here, gravity is “too weak” at, and well inside, the horizon of a stellar-mass black hole.) Which means that the way we wrote the action, and hence the EFE, above is just the natural way to write the classical limit of a theory with gravity present along with other fields.
So, real message there is any actual 'gravitons gravitate' theoretically kicks in perceptibly only at enormous energy densities where classical gravity is assumed to fail to an appreciable extent. We are no longer in the strictly classical GR energy regime. Do try and be more careful to provide full context next time.
The summary part:
QuoteIt’s important to note that there is no contradiction between the two answers we have just described. “Gravity” in the two answers means two different things: gravity as a massless, spin-two field (either quantum or classical) does gravitate (the field interacts with itself), but gravity as a tensor satisfying the Bianchi identity doesn’t gravitate, because there is nothing “left over”, once the Bianchi identity is satisfied, to contribute to the source on the RHS of the EFE.
To sum up what we’ve said so far: we’ve talked about two possible ways to answer our title question, and they lead to opposite answers:
(1) In order to ensure conservation of the source, the complete Einstein tensor, including *all* contributions from gravity, must appear on the LHS of the EFE; there is nothing left over to contribute to the “source” on the RHS of the EFE. So in this sense, gravity does *not* gravitate.
(2) Viewed as a quantum field, gravity is a massless, spin-two field, and the classical limit of the quantum theory of such a field is standard GR (based on the Einstein-Hilbert action for gravity). But this field interacts with itself; its field equation, at both the quantum and classical levels, is nonlinear. So in this sense, gravity *does* gravitate.
Only (1) is relevant here - my repeated point you have chosen to ignore twice now. Which in itself is I suppose a subtle message.
Another message is your failure to address the plain significance of that single expression R_μν = 0.
Here, again, reproduced from earlier post addressed to you:
QuoteOK, one last stab, from a slightly different but equivalent perspective. See single simple expression under 1.6 here:
www.pas.rochester.edu/~rajeev/phy413/Grav13.pdf
Please - actually THINK about it some....Let me make it real clear what that single equation means. Every in vacuo gravitational field in classical GR regime is not a source for more gravity i.e. specifically gravity does not gravitate. It covers e.g. inspiral of 'BH's' and subsequent GW emissions of any strength. That there is iirc notionally observational evidence of reduced final merged mass consistent with calculated energy-momentum loss in GW's can be taken as evidence against GR and supporting theories where gravity does gravitate as an inherent feature of that theory. I have mentioned this earlier but it goes in one collective ear and out the other.
That clear statement R_μν = 0 (in vacuo) is routinely skirted in practice via 'creative accounting' as mentioned way back. GR is an inconsistent hodgepodge where ad hoc procedures give the appearance of a coherent whole. But I get the message. Folks here have an unfailing trust in the rightness of GR, and that's that.
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1 hour ago, beecee said:
Given that I simply follow the scientific method, and latest science news, given that I am giving reputable links from reputable experts, who you as an amateur chose to be in conflict with, given that like the vast majority, I see the mainstream as the best explanation by far, given that it is you being contrary and quite arrogant as per your reply to Migl and others, given that you are known to dabble in conspiracies on that other forum you keep raising, given all that, I can safely say that I never chose to be a "winner" as you put it....simply letting you know that any alternative to GR and any incumbent model, will by necessity and rightly so, need to run the gauntlet. Nothing as yet has succeeded. Will something overtake GR? probably, one day, but it certainly is not going to do it by someone running a crusade on two or more forums, irrespective of his or her interpretations. Call me a fan boy, call me a science cheer leader, call me what you like, on this current issue, I'll stand by the incumbent until professionally invalidated in the professional way by a professional.
http://www.staff.science.uu.nl/~hooft101/gravitating_misconceptions.html
The above probably applies every day on every science forum, when some upstart or smarty that believes he can or has invalidated GR and/or Einstein. I mean knocking over the crowning ultimate top position will most certainly gain the notoriety or otherwise that these individuals seek for whatever reasons and/or whatever agenda.
from the link.....
Examples of the claims that professional scientists regularly encounter are:
- "Einstein’s equations for gravity are incorrect",
- "Einstein’s equivalence principle is incorrect or not correctly understood",
- "Black holes do not exist",
- "Einstein’s equations have no dynamical solutions",
- "Gravitational waves do not exist",
- "The Standard Model is wrong",
- "The Big Bang never occurred; Hubble's Law for the cosmic red shift is being mis-understood",
- "Cosmic background radiation does not exist",and the list goes on and on and on...........
As do you. Always having to have the last word. And - see my last post.
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5 hours ago, MigL said:
The requirement for both, a classical theory of gravity, and a quantum field theory of gravity is that it is self-coupling.
For a classical theory, like GR, stress-energy produces curvature in space-time, either static or travelling ( as in GWs ). This curvature of space-time is also a stress-energy and so, contributes to further curvature. IE gravity gravitates.
And you have made that (admittedly very widespread) assertion without looking through all that was previously posted in particular by myself?! Why should I bother further here.
OK, one last stab, from a slightly different but equivalent perspective. See single simple expression under 1.6 here:
www.pas.rochester.edu/~rajeev/phy413/Grav13.pdf
Please - actually THINK about it some. If you cannot see a direct contradiction to what you wrote above, then forget it. I will have totally wasted time and effort trying to get through to anyone here. Testament imo to just how effective has the GR brigade been in presenting it as an internally consistent 'perfect' classical theory of gravity.5 hours ago, MigL said:In a quantum field theory, which is the only place you would expect to find gravitons, self-coupling means gravitons interact with gravitons. IE gravity gravitates.
Again, you did not read my earlier remarks on that? You know, where I wrote to leave it out as we are really focusing on classical gravity. Sigh.
5 hours ago, MigL said:What exactly is the problem ?
Sigh
5 hours ago, beecee said:Don't take it too hard...that is the least of your technical errors of judgement.
I'll keep repeating it as you have done nothing, nor said anything to dispatch it as you claim. Still it looks good for the record. Your highlighted part of my statement was simply referring to flat spacetime....in other words other then spacetime that isn't curved, warped, waved or twisted in the presence of mass, thereby exhibiting gravity, which irrefutably shows that gravity is simply the geometry of spacetime.
Erroneous in your opinion, which has already been shown to be in error. All my sources are reputable including the Professor t'Hooft, a Nobel prize recipient I might add. And of course there was more then one authority supporting my position, and no, I certainly do not remember any reply inferring the authoritive position as not fully consistent.
Quote mining?? The link with the full text is there for all to read, and always is in any point I make. Obviously you don't subscribe to your "show of hands" particularly when that show of hands disputes and/or disagrees with your made up interpretation of GR, gravitational waves, etc, that happens to be supported by an isolated minority of hands.
Any appeal to authority that is appeal to authority educated and qualified in the relevant discipline under discussion, is admirable appeal to authority and totally justified, in attempting to facilitate your own understanding and the areas where you are simply wrong...and of course, most definitely yes, also to facilitate my own understanding. The usual inferences you are noted for are simply sour grapes and excuses.
My memories are pretty good for an old bloke, and once again, the bulk of references, and authoritative statements from experts and reputable links, supported the fact that gravity being non linear, means that gravity makes gravity.
Particularly authoritative figures that just happen to refute your own amateurish opinions. While thinking things through for ones self, is an admirable quality, it is not quite as admirable to make veiled inferences and accusations about science being recalcitrant and stubbornly dishonest, when your limited ability lacking the expertise and professionalism, happens to be in conflict with the well held and justified mainstream position.
Excuse me for laughing, but really, you must be getting desperate. My devotion as you sarcastically put it, is simply adhering and appreciating the scientific methodology, and dismissing the conspiracy nonsense in this regard that you seem obviously taken with....I mean really, it's near as stupid and foolish as the nuts that push the 9/11 and Moon Landing nonsensical conspiracies.
As per the thread I started re V4 gravity, and the other thread that discussion has taken place on, as per aLIGO and other reputable scientific people and orginisations, now considering and working through any possible anomalies with either the GR interpretations or that of the many alternative hypotheticals, all this shows your veiled accusations and conspiracy claims, as nothing but sheer nonsense and excuses when one is not achieving what his or her agenda dictates.
If as you say, gravity is not simply geometry of spacetime, and if as you say gravity is not non linear, and if as you say gravity does not make gravity, and if as you claim V G4 is superior to GR, why not simply take the time, and write up a scientific paper for peer review and possible publishing if successful? I believe we/I have given enough evidence to show that if what you claim is superior, and if what you claim is correct, then in time, your model will be embraced and you will be in line for the Nobel.
I never participated in that forum, but isn't it the one where you were banned? Anyway you keep referring to "that other forum" and I suggest to you that this is vastly different and far better, and the reason why I am here. So lets conduct ourselves in accordance with the far better rules and regulations here, without any references to that questionable other place, literally open to any and all nonsensical claims and conspiracies.
Given you are simply a GR fanboy with no real grasp of the issues, it's not worth my while responding to each irrelevant point you make. Feel free to consider yourself 'the winner'. That's what matters to you, is it not? I well recall your enthusiasm for keeping arguments going non-stop back in that other forum. Bye bye.
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1 hour ago, Strange said:
The waves are oscillations in the respective field, surely.
See my reply below.
1 hour ago, Strange said:As he says, not a material medium. So nothing like sound waves. I can’t see much difference between his characterisation of spacetime and, say, the electromagnetic field.
As per your above comment, and below, you are mixing up quantum concepts - QFT's electromagnetic field, with classical - EM waves as critters propagating in a distinctly different entity namely classical vacuum. I like to compare apples to apples.
1 hour ago, Strange said:(Sorry if I missed some of the points you have made, but it is almost impossible to read your posts, as they are all mixed up with quotes from other people)
Thanks to swansont's tip last post, I now know to double press Enter key for a clean separation. I had thought using supplied " quote function was sufficient. It certainly seems sufficient in my browser view - a clear vertical bar distinguishes that quoted from my response. So sorry if that was still confusing for you and swansont.
1 hour ago, Strange said:So, like light waves in the electromagnetic field then?
See above. Classical paradigm vs QFT paradigm. Best not mixed up imo.
1 hour ago, Strange said:That sounds as if you are saying GR is inconsistent with GR, so I must have misunderstood.
If you had followed my general drift that statement is more or less accurate. GR is inherently self-contradictory imo. For reasons given ad nauseum. But I refer you to the last main para in response to swansont last post of mine. Take it or leave it. Preferably leave it. When there is clear ideological commitment at play, it becomes time wasting and farcical to go on and on with intent to only point score and/or deliberately misrepresent/undermine the other side's position. Hope that is not actually happening here but looks it to me. Cheers.
29 minutes ago, swansont said:It's your comparison. Air is made up of molecules.
And? Is air an elastic medium? Does it support shear waves (umm...no) which are the nearest analog to GR's transverse GW's? Nitpicking irrelevant diversions here?
29 minutes ago, swansont said:Sorry, where did I say photons?
My bad. Still, we do tend to think these days of EM waves as a bunch of coherent photons, no? But that goes against my admonition to keep classical and quantum concepts separated. OK.
29 minutes ago, swansont said:I said electromagnetic waves. No medium is required. It's the fluctuation of a field.
Rrrright. And this gets back to the matter of GW's gravitating or not how exactly? Maybe if we just referred to what the standard EFE's has to say, analogues can be dispensed with.
29 minutes ago, swansont said:I am too vague? It's your reference. And in it he says that this applies both quantum mechanically and classically (as it must)
Yes too vague. Like right there. Please - actually quote specific passages, preferably in proper context.
29 minutes ago, swansont said:And yet you pointed to a reference that says that this is not so.
Have I? Please, again, actually quote where and how exactly. Bearing in mind my actual overall position.
29 minutes ago, swansont said:It says that there is a source term, which does not include gravity, which yields the curvature, and all of the effects of gravity self-interacting is included in the curvature (owing to the nonlinear nature of the equation). It sounds to me like it's set up that way so you don't double-count the effect of the curvature on itself.
It may sound like it to you. To me the situation is as explained by PeterDonis - there is no room for gravity gravitating in standard GR's standard EFE's. Period. Want to keep this up? Play a game of attrition? If so, you 'win'. Right here and now. If otoh there is still genuine misunderstanding at play, it's still a case of 'this will never end happily for both sides'. So - Good night, again.
29 minutes ago, swansont said:0 -
1 hour ago, swansont said:
Yes. What in GR is analogous to atoms and molecules?
Incorrect comparison. 'Atoms and molecules' would be appropriate analog to a quantized extension of GR - so-called quantum gravity aka quantized spacetime, with GR as 'emergent' classical limit. Instead, stick to what should be the obvious appropriate analog to classical GR spacetime - a continuum elastic 'medium'.
QuoteWhy? That poses obvious shortcomings to any analogy.
So explain how your example of photons propagating in vacuum, better captures the essence of GR's picture of GW's as purely propagating ripples OF spacetime WITHIN spacetime, than acoustic wave analogy does. All analogies have limitations. Some are better for the intended purpose than others.
QuoteLooks to me that he's saying that gravity is not included as a source term in the EFE.
we write the EFE the way we do in order to ensure automatic conservation of the “source”, and that way of writing the EFE requires the “source” to only include fields other than gravity.
But then goes on to say that it does, indeed contribute, and it's a matter of how the equations are broken down.
My disagreement is that the conclusion of that article is that gravity does gravitate. IOW, I disagree with your assessment, not with the article.
You are too vague. I have differentiated between his application to classical GR, vs application to gravitons on flat background. What are YOU referring to, and where and how?
Look, the situation is not difficult to grasp. Standard GR as expressed in standard EFE's has NO room for gravity gravitating. Period. That situation is routinely skirted by redefining EFE's in a way doing violence to the originally formulated clear distinction between cause and effect. (Hypothesized quantum gravity extensions of GR involving spin-2 gravitons etc. lies outside that arena.)
Evidently you and most others here are happy with that situation. I am not. Is there any point in extending this obviously fundamental ideological impasse on further? Good night.QuoteA request: please learn how to use the editor.
With the cursor at the end of the material you want to respond to, hit return a few times, and you should get a cursor outside of the quote box. That way, your response is not buried inside of someone else's quote, and can then be more easily quoted and attributed.
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31 minutes ago, Strange said:Quote
Gravitational waves and light waves are both propagating in a field not a medium. (I assume a medium means something material)
If by field you mean a notionally flat background Minkowski 4D spacetime manifold as 'field', I suppose. But then, both GW's and light waves are themselves fields, so what meaning exactly to 'fields propagating within fields'? And I already explained via quote from AE's 1922 Leyden lecture, that one is drawn to the position spacetime itself has to take on some kind of ether/aether 'medium' character. Not a material medium, owing to requirement of Lorentz invariance, but having the similarity of being a disturbance OF that medium - not something else propagating within it. Well that's what GR implies. One that imo cannot be fully consistent with GR's founding definition in EFE's. Unless one thinks non-gravitating GW energy-momentum can be self-consistent with divT_μν = 0 (to repeat yet again).
QuoteAlthough that series of articles start by saying that gravity does not gravitate, it then goes on to explain all the ways in which it can be considered that it does.
See above. The gravity as gravitons on flat background = gravity gravitates argument later there is btw a half-way house to Yilmaz gravity, or, with a radical rejection that gravitons must be spin-2, to Svidzinsky's Vector Gravity. Both the latter theories insist, in different ways, something other than pure spacetime curvature is needed for self-consistency. Again, since you have evidently taken over from swansont in responding, I will ask you to point to any logical error in PeterDonis original article - that part dealing strictly with classical GR. Which is what we are supposed to be dealing with. Yes? If you agree he makes no error there, how is subsequently making GW's self-gravitate also self-consistent? I maintain it is not.
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1 hour ago, swansont said:Quote
That assumes that spacetime is a physical medium, rather than a geometry. That's a huge assumption.
You disagree that acoustic waves as propagating distortions in a medium is a better analogy with GW's than photons propagating through an absolute vacuum? Bare in mind we are here merely asking 'what is the most obvious analog to GW's' - from purely within GR framework? Imposing e.g. Lorentz invariance on any such 'aether' is separate consideration.
How would you reconcile energy momentum in a GW with 'pure geometry' if the latter is nothing more than a way of relating distortions of clocks and rulers? On an historical note, AE himself, on pondering the different implications of GR vs SR, back-pedalled wrt his earlier total dismissal of existence of any kind of aether - see e.g 13th para and further on here:
http://www-history.mcs.st-andrews.ac.uk/Extras/Einstein_ether.html
"More careful reflection teaches us however, that the special theory of relativity does not compel us to deny ether. We may assume the existence of an ether; only we must give up ascribing a definite state of motion to it, i.e. we must by abstraction take from it the last mechanical characteristic which Lorentz had still left it. We shall see later that this point of view, the conceivability of which I shall at once endeavour to make more intelligible by a somewhat halting comparison, is justified by the results of the general theory of relativity."One cannot imo achieve self-consistency within GR's insistence gravitation is pure spacetime curvature. As my previous posts argue.
QuoteIs that a prediction of GR?
See my previous response to beecee - especially link to PeterDonis's Insights article: https://www.physicsforums.com/insights/does-gravity-gravitate/
QuoteThe energy already exists, so why would there be further gravity? The conclusion of the events is that mass is reduced, significantly, and that energy is what is contained in the GWs. So there is no "further gravity" since there is no additional energy.
You have misunderstood my basic argument it seems. Have a closer re-read. What should be conserved, in accordance with divT_μν = 0, is conservation of NET gravitating source - inclusive of GW emissions. I hope we don't go around in circles here.
QuoteDo you have a source that confirms this?
Even if it's the case, I don't see what the self-consistency issue is. There is no conservation of gravity.
See above. In particular, please point out specifically any disagreement you may have with the analysis and finding gravity does not gravitate in that article already linked to:
https://www.physicsforums.com/insights/does-gravity-gravitate/QuoteThen one needs to see where the theories differ and devise an experiment that differentiates the two. Meanwhile, the signals that have been detected by LIGO are consistent with the predictions of GR.
See my contributions in Vector theory of Gravity thread, beginning here:
The matter is currently in dispute and not likely to be resolved real soon.
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2 hours ago, beecee said:Quote
Of course it is, and you have yet to show it isn't, other then denial...
https://en.wikipedia.org/wiki/Self-gravitation"Self-gravity is the gravitational force exerted on a body, or a group of bodies, by the body(ies) that allows it/them to be held together".
Oh my. I made a slight technical error in using 'self' together with gravitating. Try and deal with my clear intended usage instead of pressing a technical definition.
QuoteAgain gravitational radiation is simply ripples in spacetime and any effect that we feel as gravity is just geometrical spacetime that is curved, warped in the presence of mass/energy, or anything other then flat. So again, the troughs and crests that gravitational radiation exhibits in those ripples, which are caused by astronomical massive asymetric collisions or mergers, affect all other mass that experiences it...as per the aLIGO arms.
You insist on repeating something earlier dispatched as an irrelevancy. And that in red is another meaningless, disjoint statement.
QuoteNo it is synonymous with making gravity and non linearity...In fact GR is said to be non linear.......http://www.einstein-online.info/spotlights/gravity_of_gravity.html "One reason why the physics of general relativity is much more difficult than that of Newton's theory of gravity or the theory of electrodynamicsis a property called non-linearity. In short, gravity can beget further gravity - where gravitational systems are concerned, the whole is not the sum of its parts."
In fact I once argued that point on another forum and had expert E-Mail replies from professionals that also supported that position.
An example imo of an erroneous online source. And as you may recall from that other forum, when I confronted that author he admitted his position was not fully self-consistent.
QuoteAnd other professionals also? No, obviously the non linearity of gravity is as most interpret it, including my above link, not withstanding your take on it.
You always did rely on quote mining and a show of hands as determinant of truth. Which approach and outlook I don't subscribe to.
QuoteAs I have attempted to explain to you in another thread, any new hypothetical must need to run the gauntlet, just as GR has, and while GR matches exactly what we observe, and makes predictions, that are continually verified, as per GW's, then it will always be hard to overthrow, until and unless it is shown to be invalid, or the new kid on the block predicts more.....That's science, that's the scientific methodology, and has far more going for it that any half arsed seemingly conspiracy jibe, or some unnecessary recalcitrance claim, on the part of mainstream and particularly GR.
And if that happens, if, it won't be first announced on forums such as this, or claims by members of I told you so, that was stupidly trotted out when the BICEP2 error came to light, it will be science, and probably aLIGO or VIRGO at the forefront of such science. In the meantime, GR reigns supreme as our model of how the universe plays out.
"I think there was some confusion here because in the discussion it should have been stated clearly what is a linear function of what. Secondly, we are talking of mathematical models of physics; if we add all the dirty side effects nothing is linear anymore. In Maxwell's theory, the em fields are linear functions of the charged sources and currents that are around, but if you take into account that these sources back react, then the combined equations become non-linear.Only in this sense, the question posed is a meaningful one: if we keep the sources and currents fixed, then our mathematical models say that the em fields are linear but the gravity fields are not.In mathematical terms, this can be explained by the fact that the local gauge group in electromagnetism is Abelian (i.e. the effect of two consecutive gauge transformations does not depend on the order) while in gravity it is non-Abelian (the effect of two consecutive curved coordinate transformations does depend on the order). Physically, this means that gravity carries energy and momentum (although this depends on the curved coordinates chosen), so gravity generates gravity, while em fields are electrically neutral.All of this did not require the consideration of quantum mechanics. In ordinary quantum mechanics, what I say above is still valid. But now, even the vacuum has vacuum fluctuations of charged particles and they cause non-linearities in light when you include the back reaction of the vacuum".http://www.staff.science.uu.nl/~hooft101/gravitating_misconceptions.html
Yes one can go on quoting authorities to bolster a particular pov. That is of course just appeal to authority - as substitute for personally having a clear understanding.
You should also recall from that other forum where I linked to someone who gave a somewhat detailed defense for why gravity does NOT gravitate in GR:
https://www.physicsforums.com/insights/does-gravity-gravitate/
Which analysis is imo rigorously logical. And respects the meaning of the very definition of EFE's.
Later in that series he then proceeds to argues that, contrary to what he shows in above linked, GW's can be made to gravitate. By the process of swapping over from LHS to RHS. Which imo is logically inconsistent with his above. Again - I never slavishly follow authority figures.
Best to actually think things through for oneself. If you can of course. Your quasi-religious devotion to GR and its creator is well known in that other forum.
PS - above will suffice to cover your later quote-mining post.-1 -
39 minutes ago, Strange said:
Are you sure? They have energy and so must be a source of gravitation. My understanding is that this self-gravitation is a cause of the non-linearity that makes GR so complex, mathematically.
Strange - what was not clear in my previous posts? You can easily check for yourself that RHS of EFE's, the SET or SEMT, specifically excludes gravitation as source term(s).
To repeat from my last post - that limitation is routinely circumvented via pseudo tensor formulations that of necessity violate the original formulation. Which basically makes a clean statement:
Effect i.e.spacetime curvature (LHS) = cause i.e. non-gravitational stress-energy-momentum density (RHS).
That's a founding physical statement defining GR. Sure mathematically one can move LHS curvature terms to RHS and make them into a source, but doing so violates the foundational physical meaning of the standard formulation. One of necessity, to 'make gravity gravitate' means removing curvature terms from the LHS over to RHS. Requiring source to produce a reduced set of effect - curvature terms. Where is the fundamental coherency in doing that?
As I wrote, it's an inconsistent situation owing to the original aesthetic choice of AE to make gravity to be purely spacetime curvature. I can certainly back my pov via links to other articles, but where has my earlier posting, which this recapitulates, not been clear to you?0 -
31 minutes ago, beecee said:Quote
Of course its relevant...GW's are ripples in spacetime, and the troughs and crests in those ripples affect all mass that experiences it...as per the aLIGO arms.
No, still not relevant to what was at stake. Which is the issue of self-gravitation of GW's or rather lack thereof in GR.
QuoteWhile already commenting on that, It's interesting to note that gravity/spacetime curvature is non linear, so gravity makes gravity so to speak.
'So to speak'? Umm...actually gravity does NOT make gravity within GR. There is nonlinear interactions but that is not synonymous with 'making more gravity'. Notwithstanding various online articles erroneously claiming otherwise. Here, check out this Wikipedia article re definition of what constitutes source terms in RHS of EFE's:
https://en.wikipedia.org/wiki/Stress–energy_tensor
First para there makes it clear only non-gravitational stress-energy-momentum is a source for gravitation. Later there, the notion of pseudo tensor formulations that claim to give GW's etc a sort of well defined source density are given some space. Fact is any attempt to circumvent the founding definition - that excludes gravitational curvature as source - is actually a sneaky reformulation of GR as something other than 'pure GR'. It's the kind of thing that is inevitable when sticking tenaciously to a theory that has inherent consistency issues.0 -
30 minutes ago, beecee said:Quote
Perhaps he is referring to what could be called a "physical medium"...Spacetime as real as I believe it is, is certainly not physical and certainly is ripples in that same spacetime.
?? Perhaps reword that bit as it makes no coherent sense.
QuoteGravitational waves are spacetime....gravity is geometry...why would geometry of spacetime need to create more geometry. Doesn't make sense to me.
Either you understand my earlier point re lack of universality within GR of stress-energy-momentum as source of gravitation, and it's consequences, or you don't.
QuoteDoesn't make sense to me.
Doesn't have to. Some folks here do understand that there is a supposedly universally valid continuity law within GR, div T_μν = 0. Well that law certainly fails outside of its differential form when GW emissions enter the picture. As per that pointed out earlier.
QuotePlus of course this gravitational wave/radiation that emenates from a particular mass, will affect all other masses that it passes through.eg: the aLIGO arms responsible for the discovery.
And? A moot point not relevant to above.
QuoteAs mentioned previously, that issue is already being looked at by the professionals in that arena, both associated with aLIGO and separated from them, and looked at I would add impartially and fairly. I mean with all the young up and comers in the discipline, who would not like to improve and/or extend on the great man's theory and be in line for a Nobel.
I sure hope it's without any fear or favour. And, once again, I don't have all my eggs in one basket. I consider at this stage Vector Gravity has many points favouring it over GR, but make no firm endorsement of it. Similarly re Yilmaz gravity. The final decider will be Nature. Once all the expected many challenges and criticisms are resolved. How long that will take is anybody's guess.
QuoteGravitons of course are still only hypothetical, so I'm not sure how it can be raised to support any alternate gravity hypothetical.
You obviously fail to grasp the context of my earlier statement on that. Gravitons are a fundamental tenet of that theory, not a hypothesized modification as is the case in GR. Hence that gravitons propagating within a notionally fixed background will self-gravitate is a consistent and inherent feature of that theory. Got that?
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11 hours ago, swansont said:
... Electromagnetic waves do not need a physical medium in order to propagate. Why would gravitational waves? ...
Well within GR paradigm GW's are nothing other than purely spacetime ripples. The better analogy then is one between sound waves and GW's. Both are distortions of a medium, and not something else propagating on top of or through the medium. Anyway there is a logical issue with GR's take on GW's as pure transverse spacetime distortions.
Given GW's carry away energy and momentum, they should also self-gravitate like all other forms of energy-momentum-stress do within GR.
But by definition, the vacuum gravitational field - both static and dynamic i.e. GW's, is NOT a source of further gravity in GR. Hence a self-consistency issue exists - there is an overall loss of gravitating mass when a binary BH or NS merger sheds GW's. That portion converted to GW's no longer gravitates.In some other gravity theories, there is no such dilemma. For instance, Svidzinsky's Vector Theory of Gravity posits GW's are comprised of quanta - gravitons. Propagating on a notionally flat background metric. In that scenario gravitons self-gravitate similar to photons do.
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Doubts about GR (split from Exclusive: Grave doubts over LIGO’s discovery of gravitational waves)
in Speculations
Posted · Edited by Q-reeus
You claim nobody else in a 100 years seems to have noticed that problem with GR. Maybe not voiced in the particular way I have here, but e.g. Sir Arthur Eddington and Nathan Rosen were entirely skeptical of existence of GW's, owing to their 'phantom' nature. From the outset there were critics of certain other features of GR that made no sense to them. Their views, not all relevant but not all misplaced either, were side-lined as a matter of historical fact. One easily derived rigorous result that undermines one of the foundational bases of GR (known by Einstein in 1907 but later abandoned by him on aesthetic grounds), is shown in appendix A here:
https://arxiv.org/abs/1606.01417
Feel free to point out here any flaw in that derivation btw. Or you would rather argue that because the GR community has not accepted that longstanding finding, the finding itself is therefore is ipso facto wrong and not even worth investigating?
I also see you or someone has seen fit to simply vanish a post (maybe others - only noticed this one by chance) of mine formally in p2 here:
https://www.scienceforums.net/topic/117103-no-energy-conservation-in-photon-by-ehf-f↓-in-space-of-expansion/
Now have an idea of the kind of editorial freedom wielded here. And a fair idea who successfully pressed for that particular case of 'post -> poof'.
Regarding the snide remarks and outside issues dragged in, please go back and check who initiated, on several occasions, snide remarks and bringing in of extraneous issues from elsewhere. All before I decided to respond. I'm betting though no official warning notice appears against that member's offending posts. I can live with that kind of thing.
Lastly, if you also persist in characterizing my arguments re GR issues here as above, well nothing more I can see worth adding to change that perception.