Theory of Everything?

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41

I guess I’m a little lost as to why if something is correct for the most part, and new information comes in that can correct some small errors that were known about for years, why would the only recourse be to classify it as incorrect and invalid except as an “approximation” when all that is required to remedy things is to incorporate a few additional formulas to correct the minor errors?

To me that’s sort of like when keeping financial records, if there are some small errors, rejecting all of those records and setting up new records completely from scratch again instead of the more reasonable approach of retaining the current records and just correcting the minor errors.

However, I do have another angle to approach this from. I wonder what would happen if the current GTR was predicated on an assumption of absolute time, space, and simultaneity, and gravity as a force rather than a spacetime continuum? Would that even be possible? Like I said, I have no problems with the equations. It’s the explanations and assumptions that I have issue with.

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I don’t understand how you can be so arrogant that despite claiming to not know physics,

You think it is easy to do what professional physicists cannot do for over 100 years. Do you think that physicists never tried incorporating corrections to Newtonian forces? We tried many ways to do it, and it doesn’t work, and it was proven that to get all the predictions of general relativity into a Newtonian form we need to add infinite number of terms - taking infinite time and effort. Not “incorporate a few additional formulas” as you think is required.

Yes, please look at Tests of general relativity - Wikipedia for an incomplete list of all the observations that has to be incorporated to Newtonian mechanics to get it correct.

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I don’t mean to sound arrogant. However, sometimes it seems to me there is quite a bit of ambiguity among scientist when it comes to making distinctions between things like explanation and description. And I recognize I’m no expert, nor have I ever claimed to be.

But I do think I can distinguish between what’s reasonable and what’s not. All I ask for in a dialogue is for others to respond in ways that directly address the issues I raise with as little ambiguity as possible. I’m more than happy to concede points when I’m given a reasonable explanation that I find persuasive.

If that weren’t the case I wouldn’t see any point in taking part in a discussion in the first place. My main goal is to gain a better understanding of things, and that by necessity involves, among other things, being willing to admit when I’m wrong.

But my nature is to think about and explore things as deeply as I can. And I think it’s important to consider not only the epistemic, but also the ontological side of an issue. Call that being stubborn or arrogant if you like, but that’s the way I approach things.

Of course I don’t. I know I don’t have any training in physics that would allow me to do such. But it does seem to me that some of the philosophical baggage from the past is possibly hindering science.

So I’m just asking questions to probe around and see if such might be the case. That seems inline with how science is suppose to operate as far as being open to considering the alternatives. Or maybe there’s something wrong with how I’m going about it?

Thanks for that link. I’m finding a lot of useful information in it. Just for information’s sake, would replacing Einstein’s assumptions and explanations in any way affect the equations of GR and SR? I can’t see how in principle it would, but since I’m not a physicist I can’t really say one way or another.

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Most, maybe all of the questions you are asking are addressed in the Norton lectures, the link above was just one of an extensive series.

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Oh, OK. Thanks. Could you point me to where exactly it addresses my last question?

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No you cannot. Not without training in physics. Your intuition is useless here.

Depends on which assumptions. That there is no absolute space and time? This will absolutely change the equations of GR. To wit, there is no Lorentz aether or preferred frame theory that reproduces GR.

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47

I totally agree with you when it comes to doing the actual physics. But when I’m talking about distinguishing what’s reasonable I’m not talking specifically about equations or any other of the technical aspects in physics.

I’m talking about the reasoning process involved, in this case in particular about the metaphysics, which is what making assumptions about absolute space, time, and simultaneity amounts to.

And from what I can tell, taking the position that they don’t exist to it’s logical conclusion is to say that nothing is real, including science. And that, to me, is what I would consider an unreasonable conclusion.

So I totally understand that when it comes to the actual physics I’m in way over my head. But my point is that, to me it’s obvious that there’s a problem with the underlying assumptions.

And I’m just attempting to get an idea of how changing those assumptions affects the actual physics itself. And I’m aware that it may be beyond what I can comprehend when it comes to putting the two together. But I figure it’s at least worth giving it a shot.

Oh. Maybe I’m confused, but as I understand it the assumptions in question are ontological in nature. Equations are simply descriptions that, when confirmed, are meant to align with observations, are they not?

As far as I know, equations don’t have anything to say about ontology, they are simply descriptive, not prescriptive. So how can it be that changing from one ontological assumption to another affects a mathematical equation?

The observations don’t change, right? So why would the equations need to change? For example, assuming absolutes of space, time and simultaneity doesn’t affect the equation in GR that corrects the problem with Mercury’s orbit does it?

If so, is there a way to explain that in terms that a lay person would understand? If not, is it possible to present an instance of an equation that demonstrates in a way a lay person would understand of why the equation would have to change? Or is it maybe the observations that call into question assumptions of absoluteness?

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You seem to be saying that the “actual physics” should not inform your assumptions, but your assumptions should inform your “actual physics”.

Why? Your conclusion is not self evident.

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49

It seems you don’t realize how much having no absolute time, space, and simultaneity is baked into the equations of general relativity. You seem to think that the situation is still like SR vs Lorentz Ether Theories, where absolute frames are completely undetectable in principle and amounts to an ontological choice.

Please write down your formulation of how you plan to add absolute time, space, and simultaneity into general relativity rigorously.

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Right. It’s an issue that philosophers argue about. But it doesn’t seem to be a settled issue. In GR and SR, as I understand it, it was dismissed at the time on grounds of verificationism. But most all philosophers agree that verificationism is no longer a valid position. So is there any valid reason why it shouldn’t be back on the table?

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No. Einstein himself did not like verificationism. GR might be one of the most anti-verificationism theory ever created in physics.

Please read my previous post:

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This is where my own understanding of the physics might start to crash against that of actual physicist @PdotdQ…

We’ve discussed this before a while back, so maybe I came away from that thread mistaken - but can’t we just say “neo-Lorentzian GR = GR (restricted to certain solutions) + undetectable foliation into spacelike hypersurfaces”?

There are problems that you’ve pointed out (e.g. extrinsic curvature form is unmotivated from 3d perspective, we don’t know if the restriction to spacelike foliable solutions of GR is physical), but AFAIK it’s still possible in principle?

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The problem is that GR (restricted to certain solutions) is not GR. In particular, there is no way to restrict these set of solutions from an initial data of GR spacetimes, i.e. given a spacetime that is within the restricted list of solutions, the equations of GR will in general move it away to something that is not within the restricted list. In order to keep the spacetimes in the restricted list to remain in the restricted list, we have to modify the equations of GR.

Thereby, GR (restricted to certain solutions) is a non-GR theory, and as a non-GR theory, we can obviously have absolute spacetimes.

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54

Aha, I see! Thank you, that makes sense.

So an A-theorist such as myself is forced to assume that corrections to GR (maybe from a theory of quantum gravity or something) will deviate in such a way as to avoid problematic singularities and such. But as of yet we have no such model, so we can’t say for sure if it’s viable or not.

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Norton’s entire “Einstein for Everyone” course there is excellent.

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I think some sort of local version of A-theory, where the ontologically real “present” is not some simultaneous surface over all the spacetime, but only in a local patch, might be consistent with general relativity. I had some vague ideas about it, but had forgotten it.

Edit: If you are prepared to be a bit of a crackpot, you might also be able to say that the restricted list of spacetimes is EVEN smaller, and consists only of spacetimes that is not only in the restricted list, but also never evolves outside of the restricted list. Such spacetimes do exist, such as the Minkowski spacetime, but this might be too constraining, as it is quite easy to make singularities (especially if you have matter and fields floating around). If one believes in mainstream science (e.g. that LIGO and EHT did find black holes, and that the Universe is described by the FLRW metric), this point of view is already rejected.

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57

Haha. I can recognize that this restriction is pretty ad-hoc and ruled out by observable evidence for black holes, which (especially now with LIGO and EHT) is pretty strong.

I’d have to place my bets on quantum corrections where the behavior deviates from classical behavior to avoid singularities (similar to how pilot-wave theory gives deviations from classical behavior that we can directly compare, thanks to definite particle positions). There’s been at least one toy model of pilot-wave style quantum gravity that explores something like this in the literature.

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That is my bet as well.

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I’ve read that there is disagreement among academics on this. And I’ve also read that Einstein was known to have repeatedly gone back and forth on his position about some issues. Maybe that’s the case here? So if not verificationism, what were his reasons for rejecting Newton’s metaphysical concept of absolute space?

How so?

No I don’t. I still don’t see how an ontological assumption can be “baked” into an equation? What do equations have to do with ontology? That’s pretty puzzling to me. How does that work?

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Because it does not conform to observational evidence.

GR makes an infinite amount of statements that is not experimentally verifiable - thus meaningless according to verificationism. It relies on completely unobservable spacetime manifolds. GR is the first physical theory in which its basic objects, positions on the spacetime is unobservable. More complex objects such as vectors and higher order tensors in GR are also unobservable. The only observable thing in GR are the scalars, the simplest of the tensors.

Absolute spacetime is really just one more unobservable thing in a sea of infinite unobservables that is assumed in GR.

Because having absolute spacetime and simultaneity are not purely metaphysical/ontological, as I mentioned earlier in this thread. I really have no idea why you keep insisting this is the case. This is why I ask you to show me how you mean to write down absolute spacetime and simultaneity into GR rigorously.

What about this: if it is purely metaphysical/ontological, then there is no way adopting them is changing any physical equations, so it will not help you with combining it with quantum mechanics thus with getting a Theory of Everything. In insisting that they are purely metaphysical/ontological, you have shot yourself in the foot, and killed your own idea that spawned this thread:

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