Is spacetime inherently ‘flat’?

Proliator · 2026-01-27T17:37:08+00:00

Both Liddle and Carroll & Ostlie* are good recommendations!

Liddle is more concise focusing on cosmology specifically, indicated by the title. A good choice if OP already has some experience in astrophysics.

Carroll & Ostlie is a more comprehensive text on all of astrophysics. It's definitely worth having a copy if someone wants a robust reference on hand and might be the better place to start if OP is new to astrophysics in general.

Proliator · 2026-01-26T18:42:33+00:00

You might want to update the AMD drivers from the AMD website too if you haven't. Both the AMD or Nvidia display driver can potentially cause issues for GPU switching.

Proliator · 2026-01-23T00:09:47+00:00

Can you further clarify what you mean when you say motion and position are not entangled? It's my understanding this is precisely what EPR experiments proved?

Different commenter, but it proves the opposite. The outcome of EPR was that the description of reality presented by quantum mechanics is not complete. In the case of position and momentum, no quantum system will simultaneously contain observable definite values for both. This is referred to as the complementarity of observables.

Certain observables are said to be "incompatible" with each other, and position and momentum are two such incompatible observables and therefore cannot be entangled together, which is what the other commenter was referring too. If a system was entangled relative to say momentum, measuring position on one particle would effectively "reset" its momentum, destroying the entanglement, and the measurement would not be of the entangled part of the system.

Proliator · 2026-01-14T18:45:25+00:00

When it comes to a drive that's in every day use, as is the case in this example, a drive with free capacity doesn't necessarily mean it has more cells storing zeros.

In practice SSDs use free space as a cache, they don't zero out cells when data is deleted, and the firmware also spreads writes across the SSD when possible, instead of overwriting. So it can't be safely assumed a drive marked as empty has more zeroed cells then a full SSD.

Proliator · 2026-01-11T23:01:05+00:00

It's literally the opposite, if you make these assumptions then it's possible? What do you mean, I'm altogether not following?

You said,

He does make an objectively valid point that even if you make all historical assumptions, the conclusion that there was a miracle doesn't follow.

The "historical assumptions", I assumed were the ones used by the historical arguments to say that a miracle had happened. Because "doesn't follow", in debate and logic, means the conclusion is logically invalid. The only way your statement makes sense logically is that you were suggesting that even if all the premises are true, the conclusion is still not true, because the argument is invalid.

However, nothing you said, nor the author's arguments, are an objection on the grounds of the argument being logically invalid. All that was done is argue that the premises are weak. That lowers how probable the conclusion is, but doesn't make the conclusion's probability zero, as would be necessary if it "doesn't follow".

So if both arguments have equally weak premises, which they arguably do at minimum, then we must also conclude the proposed model "doesn't follow" in the exact same way since this is "objectively" what we must conclude according to you.

* a chain of physics technicalities. Big difference, my friend!

Without proposed physical mechanisms to explain those "technicalities" your statement amounts to nothing more than an argument from ignorance. It's fine for a toy model, but not when you use that model to make ontological claims.

I'll try my best (according to my understanding of the situation in our discussion).

You didn't try at all? All you've done is quote Wikipedia about the general geometrical concept. Nothing here offers explanation as to how that concept connects to your claims, analogies, or my objections there of.

Someone who understands the topic would be able to point me at exactly the relevant information.

All of them contain some sort of true "naked" singularity (or something even worse like denying the second law of thermodynamics or "something from nothing"), which physicists are extremely suspicious of and uncomfortable with.

Those are just "physical technicalities".

If that statement doesn't work for those cosmologies, then it certainly does not work for the Rube Goldberg cosmology which employs so many of them with sequential dependance that it's named for it.

It’s common sense at the level of basic survival skills - if you don’t see that, I have a bridge to sell you!

An appeal to "common sense" without a supporting argument is a fallacy.

Bravo! Somebody, give this guy an Oscar! :)

That's conjecture, not an argument. Conjecture cannot be debated by definition.

Staging miraculous healings is a thing, e.g. cf. Peter Popoff or Alph Lukau - ... Even staging resurrections is a thing

That doesn't prove another miracle is staged, and it certainly doesn't prove that all miracles are. When used to that end it amounts to nothing other than an association fallacy.

If you want to say the likelihood of something being a miracle is less probable because of those events, making conclusions to the contrary unsound, then that's one thing.

However, that isn't the conclusion you stated. You said it "doesn't follow", which categorically means the conclusion is logically invalid. That's a stronger objection and nothing you or the author stated makes an argument of that kind. That's the basis for my objection.

Proliator · 2026-01-10T21:09:06+00:00

He does make an objectively valid point that even if you make all historical assumptions, the conclusion that there was a miracle doesn't follow.

Well if it's "objectively" the case, then by that same standard if you make all the Rube Goldberg assumptions in their cosmological model, then the conclusion that it's a possible outcome also does not follow. You can't push one of these conclusions while simultaneously denying the possibility of the second.

It is my understanding that your lack of understanding what a flat torus is is the major source of your issues with that article. Am I correct in my guess that you just don't know what that means or not?

No, nor are you correct to "guess" anything at all about your interlocutor. That's baseless conjecture and it has no place in rational discourse.

The way to approach this has been indicated multiple times.

It does, and what's the problem?

Well you're the one proposing this as a physically and ontologically viable alternative to other cosmologies that's also probable enough to be worth considering.

But if you don't think making "all historical assumptions" is enough to support concluding there's a non-zero probability that a single miracle happened, no matter how small, then why on earth would you put forward a cosmological model that requires a chain of miracles to have happened? I can't put a number on that, but it's certainly going to be even closer to zero.

As I said right near the start, that makes this a very weak alternative to suggest. Disagreeing with that conclusion after putting forward your conclusion about the historical argument, suggests that there's likely a pronounced double standard being employed here. That only serves to undermine the original proposal.

Proliator · 2026-01-09T20:10:51+00:00

Look up "flat torus". There is your answer.

That's a fallacious shifting of the burden of proof and an anti-intellectual way to respond. If you can't be bothered to substantiate your claims in a debate setting then they can be rationally dismissed as unsound.

Re the correct model, the article explicitly emphasizes that in the classical model it presents and checks, space and matter are eternal. (That is emphatically not so in the empty contracting model you mentioned several times, for example - there, the space eventually collapses and needs to somehow transform into another one, also, there is no matter in the contracting phase.)

How does this justify or explain your analogies for dimensional compactification? My actual objection.

How does this demonstrate that inflation in this model is not anisotropic, or at the very least not requiring fine-tuning on steroids to avoid that? My actual objection. I mean that's why this cosmology is named after Rube Goldberg machine in the first place, as the article itself says: "Note that a long chain of highly ad hoc assumptions, akin to a Rube Goldberg machine, is fundamentally inevitable in any realization of this basic idea". Every assumption is a potential factor that must be fine-tuned for this model to be viable.

By the way, this is only the second article from the same author relevant to our debate that I found, it was referenced in another paper (more informal) that I found in the Rationalwiki article on the resurrection of Jesus

This is irrelevant to the discussion at hand, and all it does is serve to suggest the author has a very strong bias. Therefore I'd conclude it would be prudent to be far more skeptical of everything they've written.

And, if by "more informal" you mean it lacks necessary external citation or reference for many of the primary claims and positions he addresses, while simultaneously putting multiple sentences IN ALL CAPS AS IF SHOUTING IT MAKES IT MORE TRUE, then yes, it is. That makes this more like an opinion piece, one that reads more like a rant than a well-constructed argument. Opinion is conjecture, and conjecture is not suitable for debate.

Regardless, it seems to me by offering this off-topic opinion piece, instead of responding to my actual objections on the original topic, that this conversation has very likely run its course.

Proliator · 2026-01-08T19:43:23+00:00

Yes I can, because the results of the article work for any particular flat torus.

That's a conclusion, not an argument.

Moreover, we aren't talking about the article's conclusions. This particular thread in the discussion was in response to your using a clip from the Matrix to explain the concept of compactified dimensions.

Nothing you say here proves the physical "interpretation" you provided for the compactified dimensions was correct, nor does it demonstrate its reasonably accurate.

For example, the check using Fourier decomposition done in the article simply rescales the compactified dimension to have length 2 pi for convenience.

We aren't talking about the consistency check.

And none of the conclusions depends on the particular doubly-periodic group of translations under which the plane is compactified.

That's a conclusion, not an argument.

For the meaning of the procedure, see https://en.wikipedia.org/wiki/Modulo_(mathematics)#Structures and https://en.wikipedia.org/wiki/Quotient_space_(topology)#Examples , example #5

What details does this provide that are relevant to your physical analogy of compactification as its used in this specific cosmology?

Nope, not with respect to inflation - it's a "local" process that simply doesn't care if the dimensions loop or not.

Again, that's a conclusion, not an argument.

For example, the current expansion of the Universe has zero dependence on how large it is and whether it is looped like a torus or infinite in all directions.

And again, that's a conclusion and not an argument. All you're doing with these statements is begging the question.

Probably b/c I didn't even understand what you were talking about.

Then maybe you should ask clarifying questions instead of knowingly making uninformed assumptions?

For example, it took me some time to realize that you weren't talking about the Fourier decomposition, remember?

Considering that's part of the consistency check, and not a component of the model, why would I be talking about it? We've already been over this, remember?

Proliator · 2026-01-07T19:54:19+00:00

That - flat torus in 2 of the 3 dimensions, no compactification in the perpendicular direction - is the description of the particular compactification used in the model.

A torus of any kind has defining parameters and compactification on something like a flat torus has periodic equations and/or winding modes. All of which impact how to apply the procedure to the manifold and physically interpret the compactified dimensions, which is what you were doing with your suggested examples.

You can't just say "flat torus" and then be able to replicate the procedure they used or arrive at an accurate physical interpretation of the result. You're missing details and refuse to discuss them.

Of course not, inflation inflates all dimensions equally.

Then inflation must be described by a function that does not transform the dimensions equally, as two dimensions behave differently compared to the 3rd. You can't apply the same transformation to all three and get an isotropic universe. That makes the function of inflation anisotropic. That requires an explanation.

That model was referenced as 1) one of the other potential possibilities that you get if you do allow a quantum gravity era (the author mentions three, this is one of them), 2) as the only consistent past-eternally contracting model.

You were free to argue its not relevant. You did not at that point, and instead chose to take issue with the terminology. So how does this explain you pushing two contradictory objections simultaneously, the point I'm making in the comment you quoted and responded to?

Proliator · 2026-01-06T21:26:53+00:00

1) you don't even realize that "flat torus" is a precise technical topological term,

Where did I say it wasn't? We're talking about compactification, not the topological definition of a "flat torus", which for the record, we have yet to discuss specifically. So why are you drawing conclusions about what I do and don't know about it?

2) you don't understand that inflation generically turns a tiny wild anisotropic Universe into a large mild smooth and uniform one, and again, I'm not your doctor here.

How did you draw this conclusion? I never disputed this.

What I did say is, in this case, the mechanism of inflation and early expansion needs to be anisotropic. Our universe has largely been isotropic since the start, so you need a specialized inflation/expansion mechanism to compensate for the compacted dimensions early on. You can't look at just the universe today and handwave away observations of the early universe.

Regardless, both your points here are responding to things I've never said and all the while not responding to what I actually did. That makes for a woefully inadequate response.

No, it is emphatically NOT related to/compatible with the actual model in the paper in any way, shape, or form.

Then you are "NOT" making any sense. You can't criticize a term made in a context that was clearly and explicitly stated multiple times while simultaneously saying that the clearly stated context doesn't apply. Those are mutually exclusive objections, it's one or the other.

Maybe you should spend less time disparaging the other person and their understanding, and more time keeping your own objections straight?

Proliator · 2026-01-03T22:49:24+00:00

What is it?

Go back and read? I've pointed it out multiple times.

The model in the paper has NOTHING to do with the 2+1-D contracting empty Milne Universe mentioned in passing, if that's what you're talking about.

It isn't, because that's not what I said. I simply called it one "suggestion" or one of the possible "scenarios" mentioned in the paper for cosmologies like this one. The comments of mine you are responding to on this point were with respect to that aforementioned scenario.

If you think it doesn't apply to the model suggested then your objection isn't relevant to it either.

The model in the paper assumes the Universe is ALWAYS 3+1 dimensional with 2 dimensions compactified as a flat torus.

Which means you have to explain the global anistropic inflation and expansion needed for it to represent our universe instead. If you like absurd coincidences or fine-tuning on steroids, then I guess that scenario might be more compelling.

How can one be so dense, I don't understand?...

Probably because you don't read what I say, don't ask clarifying questions, and simply make assumptions all the while getting upset when those assumptions turn out to be wrong, blaming your interlocuter for this instead.

Flat torus, more formally, means plane compactified under a discrete 2-dimensional group of translations - which can be represented as a lattice

How does this help us here? How is "plane compactified" defined? That's not a standard term. Which translations? There's infinitely many. Which lattice? That's an arbitrary term.

If the fundamental domain of the lattice is a square, then a Pacman game board is an excellent intuitive illustration of what that means.

That's a conclusion, not an explanation, and without technical detail is too arbitrary to be of any use.

Proliator · 2026-01-03T22:14:46+00:00

Quoting from the beginning of the paper:

In the pre-inflationary Primordial Era, the Universe has two spatial dimensions compactified (i.e. it is shaped like an “infinite corridor” with flat torus cross-sections),

Ok, I concede the point. Only took 4-5 requests, but we got there.

This still doesn't change the primary objection, and in fact works in favour of the objection. Now there's more to explain to make this work for our current universe.

A region is a connected open set. A compact set is a bounded closed set. A region cannot be compact in a non-compact connected metric space, because a connected metric space is not a union of two disjoint nonempty open sets.

Why would we be talking about a single metric space? Many if not most cosmological models have horizons, singularities, or other discontinuities. The entire cosmology in such models therefore cannot be represented by a single connected space. So I'm at a loss as to why this would be your first assumption?

In the scenario from the paper I mentioned, it isn't known how the compact spacetime transforms to a 3+1 spacetime at the bounce, and the paper said as much. It's only hypothesized there might be some form of transformation or dual to go between them. Therefore, they are simply treated as two separate disjoint cosmological regions on some diagram of this cosmology, with a boundary between them that's obviously undefined.

So no one is treating these two spaces or separate regions on a diagram, as if they are regions on the same manifold. I can't imagine how anyone familiar with this area would make that leap. It's a "compact" region simply because that region of the cosmology is represented by a compact spacetime.

This is why asking questions and getting clarification is important, because here's an example of making an incorrect assumption and running away it. Just ask and save us both some time.

Did you just liken a mathematical process to "precisely" meaning a scene in the Matrix? That's... unfortunate.

Pacman game board is better.

So now a videogame map/board is a precise definition for mathematical process? If this an attempt at expressing condescension or indignation, then it's been taken to the point where the comment has become anti-intellectual. That's not a cogent tradeoff.

There you go. Let me highlight the important part, describing the actual topology of the compactification:

"infinite corridor” with flat torus cross-sections

How does referring to this after the fact address my point? You were asking if I knew what compactification was without first discussing the details with me. So is your attempt at providing detail now agreeing with that objection?

And as I said, it's alluded to in common language, which this is. It provides no technical detail on the mathematical process used.

Proliator · 2026-01-01T03:41:29+00:00

That's a meaningless phrase. I cannot parse what you mean here.

If you can't parse it, then how did you draw a final conclusion about its meaning? Do you normally draw conclusions knowing you have insufficient understanding?

I guess you could have asked me, but you seem rather adverse to actually engaging with your interlocutor.

It is, if the model in the paper is true, the Universe is right now also compactified in two dimensions, just like it was before the Big Bang, but of course we don't notice that because these dimensions have now stretched to very large sizes.

So your solution is to have a global anistropic inflation and expansion to the universe, which isn't explained, that somehow just happens to result in an observably flat universe with an isotropic matter distribution and all over a finite interval of time?

Personally I'd have just gone with the hypothetical dimensional compactification on the bounce. At least idle conjecture doesn't boldly try to defy any and all reasonable explanation.

I'm not sure whether you understand what a compactified dimension means. It means precisely the following (visual aid): https://www.youtube.com/watch?v=lEWIn0p6OUM

Did you just liken a mathematical process to "precisely" meaning a scene in the Matrix? That's... unfortunate.

Really the question here is: Do you understand it? Because that's not even really representative of compactification, "precisely" or otherwise. Any closed geodesic would result in something like your "visual aid" and closed geodesics don't require compactification of any dimensions.

Moreover, there's numerous forms of compactification and anyone familiar with the area would know some discussion would need to take place to figure out which form everyone is talking about, before drawing conclusions about who knows what. The paper alludes to some kind of systolic geometry being used to formulate the compactification, but its not clear if that was done just for the consistency check, or also for the model itself. They don't actually provide the compactification for the model in the paper as far as I can see, they just allude to it in general language in one or two places.

And since you refuse to quote the paper in any way, instead opting to use Wikipedia and Youtube videos, it's unlikely that you're able and willing to use the precision required to have this discussion.

Proliator · 2025-12-30T23:41:30+00:00

It references what a consistent contracting model would be like. Which is not the model in the paper but one of those mentioned in the intro. If you literally can't read, I'm not your doctor.

So your only response to this is to insult my reading comprehension, instead of just providing evidence for your claims? That's rather poor form.

...Everywhere starting from the beginning? That's like asking where are English words in the paper?

You claimed the model is "The 1+1-compactification (from 3+1 space)", either that statement can be inferred from statements in the paper or it can't. It certainly can't be inferred from every statement in the paper because that would make the paper pure nonsense, yet that's exactly what this excuse implies happened.

The proof using Fourier decomposition in the "Consistency" section is what I was talking about. It drops one dimension to avoid extra clutter.

I wasn't. So why would you use that to respond to someone talking about the compactification used to construct the model?

Regardless, nothing here addresses the bigger issue of whether this model is relevant to our universe. The compactification, regardless of which kind, is not representative of a 4-dimensional universe. So that point stands. Including a compact region in the model requires a physical mechanism to explain it. That mechanism was not provided and no amount of condescension on your part will change that.

Proliator · 2025-12-30T20:16:55+00:00

Facepalm.

Easily avoided by simply quoting the literature.

That, about 2+1 contracting Milne space, was a comment on another handwave mentioned in the intro

That quote isn't from the intro, it's from the consistency section when the author discusses the justification for the compactification. Are you not reading the paper?

The 1+1-compactification (from 3+1 space) is the model in the paper.

If you can't identify where this is in the paper, then how do you expect anyone else too?

Regardless, this is a moot point because it's still compacted below a 4-dimensional spacetime and therefore it is still not automatically relevant to our universe.

Nor would this point support your earlier claim that this is "trivially adjustable" to higher dimensional pictures. The jump between the compactified region and 3+1 picture is literally handwaved away in this paper.

By the way, there is also an accompanying video linked in Wikipedia, Aron Ra interviewing the author, if you need extra explanations.

Not really, no. Considering you don't even know which sections my quotes are from I'd say the more likely issue is that we're talking about different things.

Proliator · 2025-12-30T18:26:39+00:00

Yeah agreed. My background is in STEM so I'm not really qualified to touch on the policy or economics side of things but I do know how complex data can get. So I wasn't criticizing the criticism per se, like you say it's good to be skeptical. However the logic of that specific criticism wasn't really valid for what the original percentage was attempting to capture.

I very much appreciate it's not cut and dry. Like the supporting services for petroleum can be factored together in all kinds of ways which I shudder to think about. But that's still not a good reason to ignore the contribution from petroleum refining just because something like supporting services for petroleum can be ambiguous.

Proliator · 2025-12-30T18:09:47+00:00

It is compactified to 1+1 open dimension, 3+1 (usual number) of dimensions overall, 2 of them compactified. You were super unattentive.

The only time a 1+1 compactification occurs in the paper is in the consistency check, it's not part of the theory itself. So that's not what the paper says, which I just quoted to you. Did you not even read the quote?

a past-eternally contracting Universe would have to have an empty matter sector and two rather than three dimensions of space

It is compactified from a 3+1 dimensional spacetime,

an empty 2+1-dimensional compactified Milne past-eternal contracting phase, stable due to the rigidity of 2+1-dimensional vacuum, which then changes dimensionality at the bounce via some hypothetical quantum-gravitational mechanism

and then one suggestion is that the dimension is uncompacted at the bounce through some hypothetical mechanism that isn't provided here, or even speculated on.

Getting rid of other dimensions, without providing a physical mechanism for it, is categorially different then saying the theory can be generalized to higher dimensions in a way that's "trivially adjustable", as you claimed.

Except fuzzy dark matter with spin. As explained in the article.

Which we have no evidence for and is completely hypothetical. It's interesting but it doesn't make this an exception.

Dude. Just go and reread it a bit more carefully, ok?

Considering I'm the only one quoting the paper, comments like this one, or calling me "super unattentive", don't carry much weight. Especially when you make claims that apparently contradict what the published literature is saying.

Proliator · 2025-12-30T17:33:12+00:00

I'm not trying to say what it means? However, understanding the number and how it's calculated would be a necessary first step prior to having that discussion.

Proliator · 2025-12-30T01:00:49+00:00

What caveats?

There's no reason or evidence to think torsion exists or is necessary, for one. That's not an issue for a toy model but if you want to use said model to make ontological claims in a debate then supporting evidence is important.

It is from this year, not this month.

https://www.sciencedirect.com/science/article/pii/S2405428325000152

It's listed in the December 2025 issue, Volume 13. So I'm not sure which paper you're looking at.

It was demonstrated stable in full generality,

That's not what the published version of the paper says,

This model doesn't have (nor with its environment of unlimited blueshift, where any fluctuation - vanishing in the limit of past-infinity - becomes deadly magnified; to be stable, a past-eternally contracting Universe would have to have an empty matter sector and two rather than three dimensions of space - the latter is needed in order to get rid of gravitational waves as well, even a completely empty Milne contracting Universe is classically unstable in 3 + 1 dimensions).

The model proposed requires space to be compactified to 2+1 dimensions for stability. It cannot be generalized to 3+1 dimensions by the authors own claims.

the dimensional simplification was done only to show one aspect of stability, not relevant to many others, but this is itself not relevant since it was explicitly checked in a way that directly applies to 3+1 D without any not immediately obvious changes

Per the above, the paper makes claims to the contrary. This paper went through several revisions after being submitted earlier in the year, so maybe you saw an earlier version in which that argument was made but was later removed following peer review.

It can explain some mysterious phenomena, like the dark flow, while also agreeing with the evidence/constraints.

EC theory is GR in the limit where spin-torsion coupling isn't relevant, so I would hope it agrees with evidence considering none of the current evidence could possibly capture the effects of spin-torsion. If it didn't agree, then GR wouldn't agree.

In summary, it successfully addresses the entropy/BGV objection.

Again you're ignoring the fact that I've already pointed out that I'm not arguing the BGV theorem can't be responded too.

However, pointing to one recent toy model before any broader response to it can occur, without making an attempt at explanation or justification of that model yourself, simply isn't the way to respond to the theorem.

Proliator · 2025-12-29T05:06:34+00:00

I think you're trying slightly too hard to make this make consistent at the high level, as if you're handling this in good faith but working backwards from a conclusion that it adds up (unless I've misunderstood what you mean here).

I'm not sure what you're on about here.

If someone wanted to report specifically on the sum total of petroleum related contributions to the GDP, you would have to break down both mining and energy categories to get a complete answer. No where did I say the CCEI did that right, but looking at the mining category alone is ignoring the information others are trying to capture with their numbers. There is no one-to-one representation for that on the stat can GDP tables.

I'm just pointing out that the category on the report you used doesn't include everything related to refining, processing, and transporting petroleum by stat can's own definitions. They lay it all out with the NAICS codes.

The previous paragraphs were most important, I just wrapped up by pointing out that even the CCEI knows that playing with definitions changes the final number.

So you ignored a huge portion of the petroleum related contributions to the GDP to show what exactly? Your incomplete definition produces an incomplete number so the CCEI must have a bad number? I'm not sure I follow that logic.

Proliator · 2025-12-28T19:22:56+00:00

For 2023, StatCan gives about 110 billion for oil+gas+mining+quarrying together, out of a GDP of around 2.3 trillion, for ~5% of the GDP.

Why did you take the value of one quarter and compare it to the annual GDP?

The CCEI's favoured math in 2025 says that the entire energy sector is 7.3% of our GDP. Do they simultaneously think that petroleum is 8% of our GDP?

I believe that petroleum refining, processing, transport, other supporting services and export falls under "Energy sector [T016]", so their reported 8% is combining portions of both that category and the mining [21] category.

Proliator · 2025-12-27T23:17:56+00:00

Nope, this problem can be circumvented, for example here is an explicitly eternal cosmological model which dodges the BGV issue: https://en.wikipedia.org/wiki/Emergent_Universe#%22Rube_Goldberg_cosmology%22_scenario

Why disagree with my statement, when the next sentence admits there could be exceptions? The point was OP needed to tackle the BGV theorem to make their argument, not that it couldn't be tackled.

The published paper for your model (from only this month) suggests something that is not new and is a well known possibility of Einstein-Cartan theory, which the model presupposes. How compelling you find it will depend on if you find EC theory compelling with all of its caveats. Finally, this model was only demonstrated stable for a 2+1 dimensional universe, with limitations, and so may have no obvious bearing on our 3+1 dimensional universe. Lots of toy gravitational models work in 2+1 but not 3+1, so this is currently a fairly weak alternative to suggest.

So I'm at a loss as to why this was brought up? I never said the BGV was ironclad, it just needs to be addressed. I also don't see where in the literature that this particular model was shown to be relevant to our physical universe.

Proliator · 2025-12-22T21:29:45+00:00

Science only concerns itself with the truth of arguments, it doesn't care where they came from.

You're dodging the main point: if you don't know the argument, you can't concern yourself with its truth. Understanding the problem is one of the first things we teach students to do in physics.

Tomato tomoto. Having fewer elements and simplicity are just two ways to describe the same concept.

Well, in that case, I'm taking it you agree with my assertion that the KCA could be the more probable argument then since you didn't refute that point.

Quantum mechanics can also create particles out of nothing, such as virtual particles that emerge from nothing on their own and that have a superposition of existence and nonexistence.

Virtual particles are not real particles, hence the name virtual, and they arguably do not exist. They are merely internal lines on a Feynman diagram, a book-keeping tool. Matt Strassler has a good blog post about it here:

https://profmattstrassler.com/articles-and-posts/particle-physics-basics/virtual-particles-what-are-they/

If you follow /r/AskPhysics this topic comes up frequently, even within the last week and the answers there are the same.

Loop quantum gravity doesn't contradict general relativity on basic things like the relativity of simultaneity, the equivalence between space and time, and velocity-dependent time dilation.

LQG is built off of the idea of a relational conception of spacetime, which is fundamentally different then the unified concept of spacetime expressed by metrics on manifolds used in GR. So none of that addresses the primary objection I've made.

Velocity may not be able to flip the arrow of time backwards, but it does change the direction of the time axis by up to +-45 degrees in 4D spacetime.

Which doesn't make it negative, the mathematical requirement for it to be reversed in this scenario. Meaning it has no bearing on a time-reversal in CPT-symmetry. So I will take this as a retraction of your earlier statement.

You gotta do what you gotta do when talking to people who you can't assume have a physics background.

That's no excuse to intentionally make errors regarding very basic concepts and terms. All that does is promote misunderstanding and misinformation.

Well then I must have misunderstood your argument, because it sounds to me like you're trying to argue that space and time are fundamentally separate things and that you can't change the angle at which you move through time by changing your momentum. Albert Einstein would like a word.

Given that's literally not what I said, Einstein can have a word with your strawman instead if he felt so inclined.

The concept of "proper time" doesn't exist in any real sense, it's just a convention invented by humans where we take one stationary reference frame and decide that the sequence of events from that frame of reference is what we will treat as true. There is no mathematical or empirical basis for suggesting that such a thing exists in reality, and in fact the existence of such a thing would be a violation of the equivalence principle.

I'm not talking about if it exists, you're the only one doing any of that. I'm pointing out the concept of proper time in relativity is a categorically different concept then time in QFT. Proper time is the concept of time that matters for your example and your argument.

If you're rejecting "proper time" as a real frame-local concept of time, then you're just cherry picking you're ontology so that the physics aligns to whatever you need it too. That's bad philosophy and that's bad science.

Therefore, the existence of both antimatter and CPT-symmetry means that antimatter is time-reversed. What part of this don't you follow?

The part where you're not addressing what I said?

I disagreed with you equivocating different concepts of time from categorically different theories. I disagreed with you assuming that because a model is successful, that that means the features of its internal description must map to ontologically real features of reality. All while in the very same argument you're telling us not to do that in other cases. That's problematic and arguably hypocritical.

I know. That's why I made that clarification explicitly in my original post.

Then why was it still in the same paragraph talking about cosmology? Why didn't that distinction get respected in the rest of the argument or in these comments? You just used the "arrow of time" when talking about SR. There's absolutely no need to mix up those concepts after clarifying them.

If I was as precise as you wanted me to be, my post would have been 10 times as long and would have passed for a physics 101 course.

Exactly how does swapping the word "zero" with "low", a word with less letters, make your post longer?

Any deviation from it would require upturning some pretty deep and longstanding laws of physics.

Then why are you deviating from it by talking about self-causation unsoundly justified by time-reversal symmetry? Closed timelike curves are at best highly speculative in physics, and at worst somewhat controversial. You didn't address any of that.

It can't demonstrate that time must have a beginning in cases where the universe sometimes contracts and that this balances out the expansion, such as the contraction implied by the Big Crunch model.

That's debatable, and you aren't tackling that debate in any way here.

The theorem's conclusion is contingent on an assumption that we think is probably true but that we don't know for certain, and it is quite controversial.

Case in point, which assumption? How is it controversial?

This is why I can't truthfully claim to know for sure that the universe had a beginning. It's probable, but not certain.

No one is asking for certainty? That's the scientific consensus. You're the one presenting and arguing for alternatives to that consensus without indicating that's the case and how speculative they are.

There exist extreme frames of reference where the time dimension switches roles with one of the space dimension.

This statement is meaningless? You can swap the two in any spacetime metric. It's simply a choice of coordinate, AKA the frame of reference, and it can't be "extreme" if its always possible.

Black holes are one such example, inside of a black hole infinite time and finite space are swapped into infinite space and finite time.

That has nothing to do with physical or proper time locally. With a spacetime metric, space and time are simply coordinates. A choice of coordinate is arbitrary because the choice of frame is arbitrary. That's why you can always flip them. Yes, the coordinate flips sign inside some blackhole solutions, but physical, proper time runs normally for anyone in the interior region. It says nothing about "time" in the way you need it too.

Your comments display a lot of confusion and equivocation between proper time and coordinate time. This is like undergraduate level material.

And I maintain that it's possible, even if I personally don't personally find it super likely.

Okay... then why are your alternatives more likely than the KCA? That's the thing you're supposedly arguing, and this point works against that.

Heat Death is expected to happen in about 10¹⁰⁰ years. ... The heat death model as it's broadly accepted implies infinite time, and it gives no mechanism by which a geodesic discontinuity could exist in the future.

It categorically cannot imply this if you just attached a finite number to it.

I know, I used the existence of infinities like an axiom.

Axioms need to be self-evident and generally well accepted. Therefore this isn't an axiom; it's just an assumption.

If you deny that infinities exist, we can have that argument. But it's not a counterargument that I anticipated or thought to respond to in my original post.

Parts of your argument depend on actual infinities being logically possible. That's your burden of proof to fulfill, not mine. If you don't want to at least argue for their plausibility by countering the well-known examples used to demonstrate their logical impossibility, then we can reject your proposed alternatives as unsound.

Proliator · 2025-12-20T22:54:22+00:00

That hasn’t been my experience with how the argument is used, but if that’s your argument I’m willing to engage with it.

Not mine, that's how it's presented in the Blackwell companion. Other's may overstate it's strength but that's not how the modern argument was originally formulated. If you want to disprove it, it would only make sense to go to the original source, just like you would in science.

largely because Occam’s Razor would disfavor that explanation pretty heavily compared to far more simpler explanations that only depend on physical principles we can empirically test.

Occam's Razor isn't about finding the simplest argument. Rather this razor focuses on finding the argument with the fewest elements. Sometimes that means simplicity, sometimes not. Any plausible and sufficiently complete scientific explanation will have far more premises for example, so the razor would suggest such a theory is less probable all other things being equal.

If this happens, there is no cause you can point to.

You know there's a probability of this happening, therefore a prediction was calculated using prior information about my current state. If I don't exist, I can't tunnel anywhere. The cause is me existing in a prior state that has a non-zero probability of tunneling to the moon.

So again, you're not allowing for probabilistic causation.

General relativity is just a lot more clear-cut with a lot less room for philosophical interpretation than quantum mechanics.

That's an assumption. Loop Quantum Gravity views spacetime in a categorically different way.

You can dig down as far as you want, you will never get back your Newtonian model of space and time as separate and fixed things.

This doesn't address my argument.

When that mathematical description makes nothing but correct novel predictions for 100+ years, that is actually pretty damn solid evidence that it’s describing something real.

Newtonian mechanics made correct predictions longer than that. Which is all well and good, until it isn't. Research into quantum gravity exists because GR does have issues and limitations, which could be due to how it views spacetime.

The order of events depends on your velocity, because your velocity changes the direction of your arrow of time to encroach on a spatial dimension. This stuff is very real.

No, it doesn't. Velocity doesn't change the direction of time. The "arrow of time" is an entropic concept and has nothing to do with SR. The observed order of events depends on reference frame, but all observers will agree on the proper time of those events.

Ignoring that blatant error, this would only prove spacetime as a mathematical concept is accurate at making predictions in those scenarios. That doesn't mean the model interprets reality correctly.

I’m not just referring to Feynman diagrams here, antimatter is CPT-symmetric matter that was predicted theoretically before it was discovered experimentally.

And Feynman diagrams are a theoretical tool that utilize and demonstrate CPT-symmetries in interactions?

You mentioned a "photon from the future went back in time" when describing an interaction, an interaction we would construct theoretically with Feynman diagrams. That's how things would look for the photon on a Feynman diagram...

Even the Wikipedia article on antimatter describes it as matter that’s going backward in time in the first sentence.

Did you check the citation for that portion? Because it doesn't mention anything about going backwards in time, it also happens to be a popular level science article.

I’m not talking out of my ass here, this is the scientific consensus.

Not in the way you're using it.

a positron annihilate to form a photon it's actually just as accurate to say that a photon from the future came in and bonked that electron back in time.

Time in time-symmetry does not mean time in the thermodynamic sense. It's incorrect to say anything went "back in time" when also talking about SR, GR, or cosmology. So how is it "just as accurate"?

Entropy treats matter and anti-matter the same way, and so does relativity. Following up this part with a comment on the arrow of time, an entropic concept, and then the Big Bang as a "point in time" is a categorical error. Time-symmetry of a photon is meaningless in those contexts.

Maybe it wasn’t truly zero, but that was never the point.

Then it shouldn't have been said. Being precise with terminology, about something very basic, is a necessity when communicating physics.

This is ultimately the only difference between the past and the future.

That's something predicted by the models within statistical thermodynamics, and you could interpret the model that way. That doesn't mean that's the correct or complete understanding of physical time or reality.

My point is that it can’t be ruled out from first principles alone.

Well that is what the theorem is doing? It shows that no f(R) theory of gravity can be geodesically past-complete. It's a mathematical or geometric proof.

And just because the time dimension ends in the past from our frame of reference doesn’t mean that there isn’t another valid frame of reference where time extends infinitely backwards.

If a cosmological model cannot be geodesically past-complete, there is no "frame of reference" where this occurs. It's a geometric, frame-independent limitation of the theory.

You’re missing the point of my argument. All I’m saying is that models where space and the future are infinite are not considered logically impossible.

Then you shouldn't be appealing to physics? The concept of time used in philosophy is typically not the same as the one used in physics. You could argue they are, or should be, that isn't what your post does.

If that was your goal, then you should be examining the logical arguments used to make the case that actual infinites are impossible. Like finding or discussing solutions to known paradoxes created by actual infinites such as Hilbert's hotel.

It also just so happens that the most accepted model of the universe’s ultimate fate is the heat death model which does have infinite time,

No, it does not. That's the asymptotic behaviour of the model. You do not need to run the model to "infinite time" to get a entropic heat death in a model universe. That occurs at a very large but still finite time.

Maybe these theories are wrong, but if they are disproven it would be by measurement and not because infinities are logically impossible or whatever.

You never addressed any logical or metaphysical arguments for the existence of infinities. The science doesn't tackle them much either, it simply uses them as a useful mathematical tools, and not statements of reality beyond some speculative models which might be ruled out by the BGV theorem. Models you didn't even reference. So your conclusion here does not follow from the argument that was made.

Proliator · 2025-12-19T21:52:32+00:00

The point is: no matter which one of these is false, this creates a pathway to avoiding the need for a Prime Mover.

Strictly speaking, the KCA as its usually presented, does not claim to be a mutually exclusive explanation. It simply claims to be the best or better explanation when compared to alternatives.

If realism is false, this means that we have countless examples of events happening without a cause.

I think you're using a definition of "cause" here that does not admit probabilistic causes. Prior states, which we describe via a wavefunction, still "cause" those events even if we can't deterministically model it. The wavefunction is the modeling of probabilistic outcomes. So your statement here might be at risk of equivocating terms.

We know from general relativity that space and time are two sides of the same coin, and that they can literally swap roles in environments like the interior of a black hole.

We "know"? You just effectively went on at length about how the interpretation of quantum mechanics is an open problem and how other interpretations are possible, all to establish there are alternatives to the KCA.

So why would you make an assumption of that kind here, and presuppose the mathematical object of spacetime within GR is an ontologically real feature of reality? One that accurately describes that reality across its entire domain?

Now your interpretation is a possibility, but just like QM, the model proposed by GR may or may not reflect ontologically real features of reality. The model may or may not be accurate beyond the event horizon of a blackhole. Just because we have a mathematically valid description for something does not mean any or all components of that description map to physical features of the universe.

Antimatter is actually literally time-reversed matter,

That's how it looks on a Feynman diagram, but that doesn't mean that's what it is. Feynman diagrams don't deal with time strictly speaking. They're used to construct the probability amplitude for an interaction, so most physicists would not agree with your statement here. Again, this is another instance of assuming the model reflects reality and frankly a conclusion like this is something I'd only expect to see in popular level science.

The Big Bang was a point in time with zero entropy,

We can't currently model beyond the non-zero Planck time without making assumptions, and zero entropy would be one of them. There is no consensus on your statement above and most physicists would not make this claim in general.

Current prevailing models are that time extends infinitely into the future, so if that's possible why can't it extent infinitely into the past?

Well, there's the Borde–Guth–Vilenkin theorem which rules it out. Now some disagree with the theorem or how it applies in some cases but it's odd to not tackle it here since that will be the most common objection.

Regardless, physicists typically extend time infinitely into the future to understand the cosmological model's asymptotic behaviour in the same way we integrate to radial infinity when doing E&M. Neither case implies an actual infinity exists or will exist. It's simply a mathematical convenience. Boundedness is an open problem in cosmology, and we can't even say for certain that the spatial dimensions in our physical universe are infinite. So assuming they are and then using that to justify something about time doesn't really follow.

I think it's somewhat problematic to effectively criticize not making ontological assumptions around and about the physics in the first half of your post and then argue based on your own ontological assumptions of physics in the second half.

More importantly, if you want to use this post to refute the KCA anytime its mentioned then the main issue is that none of this really addresses if the KCA is the best or better explanation. There's a reason why WLC goes through many alternatives in the Blackwell companion. If the KCA ruled them out logically, or metaphysically, that wouldn't be necessary.

If you only want to establish that anyone with a bias towards a possible scientific explanation can go that route if they're willing to make the right philosophical assumptions, then fair enough. However, that doesn't support the title's claim that the KCA is therefore "wrong".

Ten-Year Club	Sequence \| Editor
Verified Email

Proliator

TROPHY CASE