Big Bang: Discovering the Reasons Behind Its Occurrence

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The discussion centers on the origins of the Big Bang, with participants debating whether it requires a cause or purpose. Some argue that the Big Bang is a quantum event without a need for causation, while others suggest it may stem from a larger system reaching a critical point. The conversation also touches on the subjective nature of meaning and purpose, asserting that these concepts do not apply to scientific inquiries about the universe's origins. Critics emphasize that subjective judgments cannot dictate reality, and that asking for the purpose of the Big Bang is an invalid question. Ultimately, the consensus leans towards the idea that while scientific understanding of the Big Bang is incomplete, attributing purpose or meaning is a subjective endeavor rather than an empirical one.
  • #61
Chalnoth said:
I don't think it was a silly statement at all. It may have been a bit short and poorly-explained, but I don't think it was silly.

Every field of science has had a period of "growing pains" where people were just settling into the field and learning how things work. Lots of bad ideas abounded and it took time to expunge them with experimental data. But once that initial period of "growing pains" passed, as happened with cosmology some time ago, I'm not aware of a single instance of an evidence-supported theory being widely-held as true that was overturned.

There are some important qualifiers there, of course, and you may argue that those qualifiers are invalid/inconsistent, but I have seen you present nothing that makes that case.

So cosmology is fine and just needs a little tweaking? Isn't that what they said about epicycles? Again a case where math tried to trump reason.
 
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  • #62
AC130Nav said:
So cosmology is fine and just needs a little tweaking? Isn't that what they said about epicycles? Again a case where math tried to trump reason.
People have been making this sort of accusation for some time about dark matter and dark energy in particular. But I have been quite confused as to why they think the situation is in any way reasonable.

To take the example of epicycles, for instance, there were some massive conceptual problems. The first one is that when the observations became more and more precise, more and more epicycles had to be added to make them work. To contrast this with dark matter, the simplest model for dark matter, a perfectly collisionless, zero-temperature massive particle, has passed with flying colors every observation that it so far would have impacted. There are potential issues where our understanding of the physics in question is otherwise poor (such as the centers of galaxies), but in every case where the physics is relatively well-controlled, where we have a reasonably good handle on the systematic errors, this simplest model of dark matter works fantastically.

Of course, for theoretical reasons we don't expect any real dark matter to actually have zero temperature or be perfectly collisionless. And we hope to one day be able to exploit these non-idealities in order to determine more explicitly the nature of dark matter. But there most definitely hasn't been a need to continually add new properties to dark matter to explain observations.

With dark energy you might have more of a point, but there I'm starting to think that our original assumption that the cosmological constant just had to be zero was based on faulty thinking. Since we actually have no indication from theory that this parameter should have been zero, we should have expected a non-zero value, and thus should, had we paid attention to our equations, have expected to at some point observe some accelerated expansion.

Edit: I'm also confused that when claiming that we can be pretty sure dark matter is a WIMP, and dark energy is the cosmological constant, that this is equated to "everything being okay" with cosmology. No, not at all. Provided you are talking in terms of knowing everything about cosmology, just knowing that dark matter is some sort of WIMP doesn't in any way say what dark matter actually is, it just narrows down the possibilities. Stating that dark energy is actually the cosmological constant doesn't in any way say why it takes this particular value, something which definitely would require new physics to explain. It just narrows the focus to what sorts of new physics we should be looking for. Observational cosmology is by no means close to finished, but we have answered some questions.
 
  • #63
Chalnoth said:
And this would impact upon my point how? Obviously before Hubble, there was no observational cosmology, so there could be no science-based conclusion on whether or not the universe was static.

Is it not better to take that observational cosmology started from Galileo? He was the first one to use a telescope for that purpose. In that case, static universe can be taken as a science-based conclusion of the past.The expanding universe of ours may be a part of still bigger static entity, the Ensemble containing the multiverses. Or, being static can be a concept of the future also.
 
  • #64
finiter said:
Is it not better to take that observational cosmology started from Galileo? He was the first one to use a telescope for that purpose. In that case, static universe can be taken as a science-based conclusion of the past.The expanding universe of ours may be a part of still bigger static entity, the Ensemble containing the multiverses. Or, being static can be a concept of the future also.
That would have been astronomy. Modern cosmology didn't really start until we had an inkling that our universe extended beyond our own galaxy, which was what Hubble's observations showed.

Yes, in a way cosmology was what Galileo was dealing with, but that was only because at the time, they thought our universe was smaller than our own solar system turned out to be! Modern cosmology didn't really start until we started to get hints as to the true extent of our universe.
 
  • #65
Chalnoth said:
To take the example of epicycles, for instance, there were some massive conceptual problems. The first one is that when the observations became more and more precise, more and more epicycles had to be added to make them work.

To make the analogy between Ptolemaic Cosmology and Modern Cosmology more precise you only need to substitute ad hoc modifications for epicycles in the second sentence above. The ad hoc modifications of MC would be Inflation, Dark Matter and Dark Energy all three of which have been added to compensate for predictive failures of the model.

Also analogous is the failure of MC to reexamine it's underlying premises as a consequence of those predictive failures. PC was premised on an Earth centric cosmology with all extraterrestial objects orbiting the Earth in perfect circles.

MC is premised on the existence of a Universe, meaning the existence of a singular space-time reference frame encompassing all of the observable and unobservable cosmos and a corollary assumption that the observed cosmological red-shift is the product of a recessional velocity.

Chalnoth said:
...the simplest model for dark matter, a perfectly collisionless, zero-temperature massive particle, has passed with flying colors every observation that it so far would have impacted.

This is hardly surprising since Dark Matter is by design without interactive properties other than the gravitational (and otherwise unobservable) mass necessary to bring the MC model into conformance with observation.
 
  • #66
budrap said:
To make the analogy between Ptolemaic Cosmology and Modern Cosmology more precise you only need to substitute ad hoc modifications for epicycles in the second sentence above. The ad hoc modifications of MC would be Inflation, Dark Matter and Dark Energy all three of which have been added to compensate for predictive failures of the model.
By this logic, anything that we ever learn that is new would be just another epicycle.

For dark matter and inflation in particular, they were each proposed as a potential solution to a particular puzzle. Dark matter was initially proposed because galaxy clusters appeared to be far, far more massive than could be explained by their stars. Inflation was initially proposed to solve the flatness and homogeneity problems inherent in the big bang theory. Each made very specific predictions about future observations, predictions that could, in principle, have turned out some other way, but were nevertheless borne out by observations.

This is the exact opposite of epicycles, because the simplest version of the original idea has been continually borne out by observation (for inflation, that's chaotic inflation, for dark matter, that's cold, collisionless massive particles).

Dark energy is rather more difficult, just because it's an extremely weak effect. However, our best test of this that we know of so far will come in the relatively near future with weak lensing observations that measure the growth of structure (that is, how quickly the universe becomes more clumpy). This sort of observation turns out to be very sensitive to the nature of dark energy. It's also a difficult observation to do correctly, so we should expect it to take a little while to hammer out all of the systematic errors.

budrap said:
This is hardly surprising since Dark Matter is by design without interactive properties other than the gravitational (and otherwise unobservable) mass necessary to bring the MC model into conformance with observation.
Nobody expects dark matter to be completely collisionless. Many models of dark matter, for instance, interact with the weak nuclear force in the same way that neutrinos do. It just turns out to be rather difficult to rule out any particular model. Fortunately, however, current dark matter searches are actually starting to rule out some significant regions of parameter space. Perhaps in a few years we'll get lucky. We'll see.
 
  • #67
Chalnoth said:
By this logic, anything that we ever learn that is new would be just another epicycle.

No, what we learn when the model fails is that it is inadequate. It is the ad hoc hypothesis that is "just another epicycle". This doesn't make the hypothesis necessarily wrong but unless the model's underlying premises are simultaneously reexamined to see if they are still sound in the light of new data then there is always the danger that the MC model will suffer the same fate as the Ptolemaic - wrong for a millenium but still capable of cranking out a right answer.

Like the Earth centric perfect circles of Ptolemy the "Universe" as a singular container of the cosmos is a vestigal concept from deep in our cultural history. It desperately needs to be reconsidered.
 
  • #68
Chalnoth said:
Nobody expects dark matter to be completely collisionless. Many models of dark matter, for instance, interact with the weak nuclear force in the same way that neutrinos do. It just turns out to be rather difficult to rule out any particular model. Fortunately, however, current dark matter searches are actually starting to rule out some significant regions of parameter space. Perhaps in a few years we'll get lucky. We'll see.

At least we get decent answers from you--not true in other portions of the Physics Forum where the current dogma is viciously defended.

However, I do not see how anything with mass (unlike the poster to whom you responded) could fail to to have collisions. Mass implies a gravitational field, and this is what collisions are about not surfaces.

Question: I have read that the "expansion" of the universe has been found not to be uniform. (I put it in quotes not because I don't believe in it, but because I don't think that's the right word--more like rapid decompression in aeronautical terms). Is it uniform at all distances from us?
 
  • #69
AC130Nav said:
However, I do not see how anything with mass (unlike the poster to whom you responded) could fail to to have collisions. Mass implies a gravitational field, and this is what collisions are about not surfaces.
Collisions among matter which we are familiar with are driven by the electromagnetic force, not the gravitational force. Basically, when atoms get squeezed together, the electrostatic repulsion of the electrons prevents too much compression, or the atoms passing through one another, even though atoms are mostly empty space.

We already have a relatively familiar particle, after all, that has mass, interacts gravitationally, and yet passes through matter all the time: the neutrino. Neutrinos don't have enough mass to explain dark matter, but we expect that whatever particle actually makes up the dark matter would turn out to be much like the neutrino in its interactions, just with more mass.

AC130Nav said:
Question: I have read that the "expansion" of the universe has been found not to be uniform. (I put it in quotes not because I don't believe in it, but because I don't think that's the right word--more like rapid decompression in aeronautical terms). Is it uniform at all distances from us?
The expansion of our universe is quite uniform to within experimental tests. Here's one measure using supernovae as a test:
http://www.pnas.org/content/101/1/8/F3.expansion

This diagram, termed a "Hubble diagram", which is a diagram of velocity vs. distance, shows a linear relationship out to about 650Mpc, or a little over 2 billion light years. That's pretty uniform. We also have measures that go even further out, but this is one that I found quickly and felt it was good enough to drive the point home.
 
  • #70
budrap said:
No, what we learn when the model fails is that it is inadequate. It is the ad hoc hypothesis that is "just another epicycle".
But the accusation of inflation, dark matter, and dark energy being "ad hoc" is entirely specious. Yes, they were each initially proposed as a possible explanation for a particular inadequacy in the model. If you'll look at the history, there were a number of competing models for each of these things. But those competing explanations have been knocked out one by one by subsequent observations, and now only inflation, dark matter, and dark energy have survived (though granted, modified gravity still remains a possibility for the explanation of the accelerated expansion, it isn't looking good for that possibility).

You might wish to claim that maybe there is some explanation that we haven't thought of yet, but that isn't science. One of the primary driving forces of scientific work stems around simple practicality. You can't do work on, "maybe it's something we haven't thought of yet," as you have to have a specific idea to at least get started. If you have a specific idea of an alternative, then great! Work on it! Flesh it out! See if it is self consistent, see if it is consistent with past observations, see if it provides testable predictions for future observations.

But don't just stand on the sidelines and say, "Yeah, I think it's something else." That isn't science.
 
  • #71
Chalnoth said:
You can't do work on, "maybe it's something we haven't thought of yet," as you have to have a specific idea to at least get started. If you have a specific idea of an alternative, then great! Work on it! Flesh it out! See if it is self consistent, see if it is consistent with past observations, see if it provides testable predictions for future observations.

Cold energy, where temperature go below 0K, I think, could explain a black hole. I don't know whether anybody else have made such a suggestion earlier. Can you confirm? However, I have been working on that for some time.
 
  • #72
finiter said:
Cold energy, where temperature go below 0K, I think, could explain a black hole. I don't know whether anybody else have made such a suggestion earlier. Can you confirm? However, I have been working on that for some time.
Temperature can't go below zero. Temperatures that are numerically below zero turn out to act, thermodynamically, as temperatures that are hotter than positive infinity.
 
  • #73
[
Chalnoth said:
But the accusation of inflation, dark matter, and dark energy being "ad hoc" is entirely specious. Yes, they were each initially proposed as a possible explanation for a particular inadequacy in the model.

These two sentences are mutually contradictory, like claiming to be a God-fearing atheist.

Chalnoth said:
You might wish to claim that maybe there is some explanation that we haven't thought of yet, but that isn't science. One of the primary driving forces of scientific work stems around simple practicality. You can't do work on, "maybe it's something we haven't thought of yet," as you have to have a specific idea to at least get started. If you have a specific idea of an alternative, then great! Work on it! Flesh it out! See if it is self consistent, see if it is consistent with past observations, see if it provides testable predictions for future observations.

But don't just stand on the sidelines and say, "Yeah, I think it's something else." That isn't science.

The objection I raised was not vague I thought but very specific. Let me restate:

1. As with the Ptolemaic model the proponents of the Modern Cosmological model only patch the existing model when it encounters a predictive failure.

2. In and of itself this is not wrong just inadequate. Whenever a model fails it's fundamental assumptions should be re-evaulated in light of that failure. If a model fails repeatedly the imperative to re-evaluate should become evermore scientifically compelling.

3. The specific underlying assumption of the MC model that I feel is most in need of re-examination is that there exists a singular "Universe" which encompasses all of the observable and unobservable cosmos. This concept of "Universe" has never been scientifically vetted, only assumed. It appears to be a vestigal cultural concept much like the the Earth centric perfect circles of Ptolemy.

If you choose not to address these points that is certainly your perogative. If you wish to argue them please do. But please, spare the strawman arguments. Thanks.
 
  • #74
budrap said:
These two sentences are mutually contradictory, like claiming to be a God-fearing atheist.
The key point is initially. If people had said they were true only based upon the initial evidence, yes, I might agree with you.

budrap said:
2. In and of itself this is not wrong just inadequate. Whenever a model fails it's fundamental assumptions should be re-evaulated in light of that failure.
The funny thing is that you think this hasn't actually been done.

budrap said:
3. The specific underlying assumption of the MC model that I feel is most in need of re-examination is that there exists a singular "Universe" which encompasses all of the observable and unobservable cosmos. This concept of "Universe" has never been scientifically vetted, only assumed. It appears to be a vestigal cultural concept much like the the Earth centric perfect circles of Ptolemy.
While I happen to agree with that this is often speciously assumed, it in no way places doubt upon these three models. This is, by large, a separate issue related to how we go about determining whether a particular model is likely or unlikely, but it doesn't really effect the observational evidence in favor of inflation, dark matter, and dark energy.
 
  • #75
Chalnoth said:
The funny thing is that you think this hasn't actually been done.
The funny thing is that you seem to be agreeing that it hasn't actually been done with respect to the concept of "Universe" here:
Chalnoth said:
While I happen to agree with that this is often speciously assumed, it in no way places doubt upon these three models. This is, by large, a separate issue related to how we go about determining whether a particular model is likely or unlikely, but it doesn't really effect the observational evidence in favor of inflation, dark matter, and dark energy.

As far as I can see there is only one model (Modern Cosmological) with three patches (Inflation, Dark Matter, Dark Energy) required by predictive failures of the MC and there is no direct observational evidence for any of them nor is there likely to be any time soon. The best that can be said is that there are no contradictory observations.

The interesting thing about a cosmology devoid of a singular all encompassing "Universe" is that both Inflation and Dark Energy would be irrelevant in the same way that epicycles became irrelevant after Copernicus/Kepler. Dark Matter might still be an interesting hypothesis depending on whether or not the new model directly clarified the gravitational issues DE seeks to address.
 
  • #76
budrap said:
The interesting thing about a cosmology devoid of a singular all encompassing "Universe" is that both Inflation and Dark Energy would be irrelevant in the same way that epicycles became irrelevant after Copernicus/Kepler.

Can you provide a reference to a publication in a reasonably current peer-reviewed journal, or possibly on arxiv.org, that proposes or uses such a cosmology? (Note that arxiv.org carries less weight because it is not peer-reviewed.)

I'd like to remind participants in this thread about the Physics Forum rules which are accessible by clicking the "Rules" link at the top of every page here, in particular the section Overly Speculative Posts. It is not part of the mission of PF to promote challenges to currently generally-accepted theories based on pure speculation. If a viewpoint is in fact part of current scientific discussion, as reflected in professional literature, even if it is a minority viewpoint, then it's OK to discuss here. If it's an outdated viewpoint that is not supported by current evidence, then it's not appropriate to harp on it here, just as we don't support promotion of classical luminiferous-aether theories against relativity.
 
  • #77
budrap said:
The funny thing is that you seem to be agreeing that it hasn't actually been done with respect to the concept of "Universe" here:
Huh? No, a number of people have looked into a variety of possibilities of what may lie beyond our observable universe. But these have very little bearing on dark matter, dark energy, and inflation, which are invoked to explain observations within our own observable universe. I think that the opposition to many such ideas is a bit too vociferous myself, but that doesn't mean the investigations aren't being carried out.

What is clear, though, is that you're extremely off-base. Investigations into what may or may not occur beyond our cosmological horizon has very little bearing on inflation, dark matter, and dark energy. There are some model selection arguments that depend upon what occurs outside of our cosmological horizon, but there is no way in which what occurs beyond our cosmological horizon can possibly do away with these models.

The only somewhat reasonable alternative explanations to these models today lie in modifications to gravity. Today we've ruled out the possibility of observational artifacts accounting for dark matter/dark energy. So it just becomes a question of whether we understand the matter content of our universe, or whether we understand gravity (since gravitational measurements are the only situation in which these discrepancies arise). As of today, nobody has yet produced a compelling modification of gravity to explain either dark matter or dark energy.

As for inflation, the horizon problem essentially proves that it or something like it must necessarily have occurred. The only reasonable alternative to inflation so far is the ekpyrotic model.
 
  • #78
jtbell said:
Can you provide a reference to a publication in a reasonably current peer-reviewed journal, or possibly on arxiv.org, that proposes or uses such a cosmology? (Note that arxiv.org carries less weight because it is not peer-reviewed.)
Hm, this is a peculiar request. My point is precisely that the merits of the singular Universe concept that undergirds the currently accepted cosmological model have never been scientifically evaluated. Therefore it is highly unlikely that there would be a paper proposing an alternative to this unacknowledged and unexamined a priori assumption that the cosmos is comprised of a singular reference frame such that it may be considered a singular entity or Universe.

The very fact that you are obviously unaware of any such an alternative cosmology is illustrative of my point. None exists because none has ever been considered. I don't see how that disqualifies my comments under the rules you mention unless you wish to dismiss them simply on the grounds that they are novel. Hopefully the bar for Overly Speculative Posts is not quite that low.
 
  • #79
Chalnoth said:
Huh? No, a number of people have looked into a variety of possibilities of what may lie beyond our observable universe. But these have very little bearing on dark matter, dark energy, and inflation, which are invoked to explain observations within our own observable universe. I think that the opposition to many such ideas is a bit too vociferous myself, but that doesn't mean the investigations aren't being carried out.

What is clear, though, is that you're extremely off-base. Investigations into what may or may not occur beyond our cosmological horizon has very little bearing on inflation, dark matter, and dark energy. There are some model selection arguments that depend upon what occurs outside of our cosmological horizon, but there is no way in which what occurs beyond our cosmological horizon can possibly do away with these models.

I guess I am not expressing myself very clearly. I at no point meant to imply knowledge of or a theory about what lies beyond the cosmological horizon. What I am attempting to convey is the idea that the cosmos we observe may not be all or part of a singular entity commonly called the Universe. Put another way I am simply stating that the question of whether or not there exists a universal space-time reference frame needs to given a proper scientific evaluation. As of now its existence is merely an a priori feature of the MC model.

Chalnoth said:
So it just becomes a question of whether we understand the matter content of our universe...

Therein lies the problem sir, you assume the existence of a "Universe" where none in fact may exist.
 
  • #80
budrap said:
I guess I am not expressing myself very clearly...
Therein lies the problem sir, you assume the existence of a "Universe" where none in fact may exist.

Haven't got a clue what you're saying.

At first I thought you were a multiverse type; now I think you're a nihilist. That last doesn't belong here but might explain why you make no sense.
 
  • #81
budrap said:
Therein lies the problem sir, you assume the existence of a "Universe" where none in fact may exist.

AC130Nav is correct. This is the Cosmology Forum; the universe exists here by definition.

Philosophy Forum is two doors over. You may deny existence there.
 
  • #82
DaveC426913 said:
AC130Nav is correct. This is the Cosmology Forum; the universe exists here by definition.

Philosophy Forum is two doors over. You may deny existence there.

Yes, this is the Cosmology Forum but it is not the existence of the cosmos (or anything else that can be empirically demonstrated) that I am questioning. What I do question is the assumption that the cosmos is possessed of a universal space-time reference frame which consequently renders it a "Universe" or singular entity. It is my contention that said assumption is unsupported by any empirical evidence.

If you wish disagree then produce the empirical evidence that supports the assumption of a universal space-time reference frame. Scientifically speaking you can't just insert it "by definition" except as hypothesis and if it's only a hypothesis then it must be subject to review or discussion.

If the distinction I am drawing between the cosmos and its characterization as a singular "Universe" is lost on you perhaps you should avoid discussions of matters that tax your ability to think and stick to comedy. But just to be clear here, I don't object to your disagreeing with me, only please offer scientific objections not quasi-religious arguments from authority. That is not the way of science.
 
  • #83
budrap said:
Yes, this is the Cosmology Forum but it is not the existence of the cosmos (or anything else that can be empirically demonstrated) that I am questioning. What I do question is the assumption that the cosmos is possessed of a universal space-time reference frame which consequently renders it a "Universe" or singular entity. It is my contention that said assumption is unsupported by any empirical evidence.

If you wish disagree then produce the empirical evidence that supports the assumption of a universal space-time reference frame. Scientifically speaking you can't just insert it "by definition" except as hypothesis and if it's only a hypothesis then it must be subject to review or discussion.

If the distinction I am drawing between the cosmos and its characterization as a singular "Universe" is lost on you perhaps you should avoid discussions of matters that tax your ability to think and stick to comedy. But just to be clear here, I don't object to your disagreeing with me, only please offer scientific objections not quasi-religious arguments from authority. That is not the way of science.

Actually there are good arguments against "quasi-religious arguments from authority," but your nonsense is giving them a bad name.

Let me be specific in one regard, "produce the empirical evidence that supports the assumption of a universal space-time reference frame." I'm not sure that's part of the current theories (I like it though, as long as 4 dimensions is not the limit). But it has nothing to do with science, which is restricted to what can be demonstrated. It is not that ONLY four dimensions must be demonstrated, but that AT LEAST four dimensions must be demonstrated (more to be proven by experiment).
 
  • #84
Passionflower said:
Now if you use for instance a Fermi normal coordinate chart in curved spacetime or simply a rest frame in Cartesian coordinates in flat space you can use time (which is then proper time) on one axis so it looks like it is a separate dimension. But just by using such a charts does not make it a dimension.

There is a distinction between the manifold and a choordinate chart and it is a mistake to assume that any of the dimensions of the manifold is time.

according to the einstine picture of space and time any thing having a mass can curve the space time fabric but since time is not a spatial dimension how can it be curved by any body??
 
  • #85
FizixFreak said:
according to the einstine picture of space and time any thing having a mass can curve the space time fabric but since time is not a spatial dimension how can it be curved by any body??


You answered your own question.

As you said, mass curves spacetime (not just space). A massive object curves all 4 dimensions.
 
  • #86
jtbell said:
It is not part of the mission of PF to promote challenges to currently generally-accepted theories based on pure speculation. If a viewpoint is in fact part of current scientific discussion, as reflected in professional literature, even if it is a minority viewpoint, then it's OK to discuss here.

I think that PF does allow questions that may challenge the validity of the generally-accepted theories? Questioning the existing concepts is different from arguing on the basis of an un-accepted theory.
 
  • #87
DaveC426913 said:
You answered your own question.

As you said, mass curves spacetime (not just space). A massive object curves all 4 dimensions.

It might have been better to say (or at least mention) that time slows in the vicinity of a mass and then have given an example (from experimental data).
 
  • #88
budrap said:
What I do question is the assumption that the cosmos is possessed of a universal space-time reference frame which consequently renders it a "Universe" or singular entity. It is my contention that said assumption is unsupported by any empirical evidence.

May I ask what are the consequences if the cosmos does not have a universal space-time reference? I would guess from your dialog you suggest this would imply the cosmos then would not be a single entity, a "Universe", but would rather be somehow "disjointed" or separated in some way. If so, could you explain what that would mean.
 
  • #89
jackmell said:
May I ask what are the consequences if the cosmos does not have a universal space-time reference? I would guess from your dialog you suggest this would imply the cosmos then would not be a single entity, a "Universe", but would rather be somehow "disjointed" or separated in some way. If so, could you explain what that would mean.

What it would mean, I think, is that the early astronomers were correct in their first impression that galaxies are Island Universes. Meaning that galaxies each have their own unique reference frames because they each have unique origins relative to other galaxies. If that is true of course, we should expect to see evidence of galactic formation and evolution as we survey the cosmos. The observations of the astronomer Halton Arp support this view though they are widely ignored since they also cast doubt on the redshift as recessional velocity assumption that is the fundamental basis of the Big Bang model.

There is really nothing that novel in idea that there is no universal spacetime reference frame; it arises directly within the context of Special Relativity. A universal reference frame reappears in discussions of General Relativity, however not as a direct consequence of the theory but is simply imposed as a matter of convenience. If you apply the GR equations to the "Universe" you are inherently invoking a universal reference frame regardless of whether or not one actually exists. That, I think, was Einstein's greatest mistake.
 
  • #90
budrap said:
What it would mean, I think, is that the early astronomers were correct in their first impression that galaxies are Island Universes. Meaning that galaxies each have their own unique reference frames because they each have unique origins relative to other galaxies. If that is true of course, we should expect to see evidence of galactic formation and evolution as we survey the cosmos. The observations of the astronomer Halton Arp support this view though they are widely ignored since they also cast doubt on the redshift as recessional velocity assumption that is the fundamental basis of the Big Bang model.
Halton Arp's views are flatly contradicted by the existence of the CMB. Full stop. Nothing more needs to be said about his views unless he (or somebody else) can demonstrate a thermal distribution for such CMB light stems directly from his model.

Because the best he's been able to do so far is claim that his model predicts a "nearly uniform background light", which I consider a very spotty claim, but in any case there is no expectation of anything like a thermal distribution.

budrap said:
There is really nothing that novel in idea that there is no universal spacetime reference frame; it arises directly within the context of Special Relativity. A universal reference frame reappears in discussions of General Relativity, however not as a direct consequence of the theory but is simply imposed as a matter of convenience. If you apply the GR equations to the "Universe" you are inherently invoking a universal reference frame regardless of whether or not one actually exists. That, I think, was Einstein's greatest mistake.
Huh? This is flatly wrong. General Relativity contains even more freedom in reference frame than special relativity did. One can even do a number of calculations in GR without using any reference frame at all. This is useful, for instance, in demonstrating whether or not any weird features you see in your current equations are just a result of a bad choice of coordinates, or whether they actually exist in the model.

Of course, when it comes to understanding cosmology, it turns out that there exists a very convenient coordinate system (comoving coordinates). This is most certainly not a preferred reference frame, just a convenient one when talking about the expansion of the universe and its effects. In other areas, different coordinates are preferable.
 

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  • · Replies 11 ·
Replies
11
Views
3K