Finite Big Bang, Infinite universe? [Archive]

Cuetek

Mar31-08, 11:34 PM

ETA: I do find these assumption ripe for theoretical and possibly empirical questioning. They are however empirically consistent thus far.

Surely the Big Bang under the current tenets of the cosmological principle is perfectly consistent for a region at least 1,000,000 times the dia of the visible universe (based on the CMB uniformity) without modification. But for 1,000,000,000 times the vis. u.? Maybe not; For 1,000,000,000^^2 times?... Who among us seriously thinks that we won't need to modify the theory of relativity in some fashion over the next 1000 years?

As far as relativity goes, any characterization of "super-regional" material dispositions surrounding us at vast distances beyond the ultimate extent of the Big Bang would themselves presumably exhibit the same internal tensor relationship between matter and space that the Big Bang does as well as collectively exhibiting these relationships inter-structurally over whatever interstitial spans exist at such scales. We could expand into such immense interstices and perhaps be only very slightly tugged (acceleration of our local expansion profile) by the influences of such hypothetical structures, all without unduly disturbing the overall tensor relationships.

The thing that I feel behooves us to presume the extension of the material hierarchy is that it predisposes us to look for diversity beyond our current data set that has always been the case. Every time we humans have tried to devise a complete description of the cosmos we find there is a larger structure beyond the range of our instrumentation that each time reconfirms the hierarchy. Yet even though the previous cosmology always turns out to be a hierarchical subordinate of the following cosmology, we still try to terminate the hierarchy each time. Why not anticipate this process?

Formalizing the notion that there will always be more diversity beyond the limits of our examinations is the better strategy even if the hierarchy does terminate at some point. That is, if there are only two more tiers of ever larger structures beyond the Big Bang, we will be better off always searching for the next discovery and being surprised just once when the search is over, rather than falsely presuming an end to the hierarchy and having to be stubbornly convinced two more times before the search ends. It's just an efficiency thing, of course. The data will take us where it takes us, no matter what. But why not expedite the process?

MeJennifer

Apr1-08, 07:44 AM

Cuetek

Apr1-08, 12:51 PM

Who makes the claim the the Big Bang is a finite structure?

I do.

-<[{( Speculation Alert!)}]>-

I base my presumption of the Bayesian probability that the unbroken material hierarchy we see across 40 orders of spatial magnitude continues beyond the Big Bang. I presume the cosmological principle to apply out to many millions of times the diameter of the visible universe and the Big Bang to range far beyond that, but neither to abide indefinitely. It seems purely philosophical, but it addresses a certain psychological pathology we humans have always suffered at the limits of our understanding.

Basically this theory limits the first two axioms of the cosmological principal --(1) the homogeneous and (2) isotropic universe)-- by suggesting the following two axioms as more universal:

1) The Finite Rule: All material phenomena are finite in extent and constituent to a larger structures.

2) The Plurality Principal: All material phenomena are multiply manifest.

(numerical justification: http://www.thegodofreason.com/rules-of-discovery.pdf)

If the Big Bang were just a million times the diameter of the visible universe then we would only see one part per million difference in the homogeneity of the visible universe from one side of the sky to the other. (WMAP data only goes to about 25 parts per million resolution.)

This video poses a rationale for the above two rules:
http://www.youtube.com/watch?v=ILvjLMoyRm0

This video offers an improvement of the Cosmological Principle:
http://www.youtube.com/watch?v=H1aFTl-9I9Q

And this video is a speculation on how we might imagine the large scale
structure of the Big Bang under the constraints of the two rules:
http://www.youtube.com/watch?v=PzMAbGoDeC4

cristo

Apr1-08, 01:20 PM

I do.

-<[{( Crackpot Alert!)}]>-

Erm... labelling your post with "crackpot alert" is not a good start. Have your read the PF rules (http://www.physicsforums.com/showthread.php?t=5374)?

Cuetek

Apr1-08, 01:33 PM

Erm... labelling your post with "crackpot alert" is not a good start. Have your read the PF rules (http://www.physicsforums.com/showthread.php?t=5374)?

Yeah, Cristo, I've read 'em, and that's kinda why I prefaced the balance of my post. The rules say that I should discuss with informed people as to the prevailing technical realities before I post. I started this thread in order to do exactly that. As the thread developes I am inevitably prodded for further explanation of why I might be asking my original question. So, for those uninterested in my more speculative points, I warn them off with the alert. Is that a bad thing?

my_wan

Apr1-08, 07:43 PM

I do.

-<[{( Crackpot Alert!)}]>-

I could take that as a -<[{( Speculation Alert!)}]>- iif (yes 2 i's) your rants had a thread of empirical content. I will not even let the official advisor's here get away with overstating the veracity of certain standard model claims. Why then would I give some claim from left field any consideration whatsoever. Especially one that purports to derive legitimacy from argument alone.

My personal experience when trying to actually give such ideas a fair trial is objections that it simply must be that way. Followed often by accusations of ignorance. Capernicus even prefaced his questions with such accusations. So I'll not bother.

marcus

Apr1-08, 08:39 PM

What is wrong with the idea that the Big Bang is a finite structure a million or more times the diameter of the visible universe, and the universe surrounds it in the same way that the visible universe surround the Milky Way?

-Cuetek

When I say "in the same way that the visible universe surrounds the Milky Way" I mean that fairly literally, like the Big Bang eventually dissipates entirely at some distant point and gives way to relatively empty space for some arbitrary span whereupon some other disposition of matter is encountered. Does inflation theory allow for at least the possibility of this type of material disposition?

I base my presumption of the Bayesian probability that the unbroken material hierarchy we see across 40 orders of spatial magnitude continues beyond the Big Bang. I presume the cosmological principle to apply out to many millions of times the diameter of the visible universe and the Big Bang to range far beyond that, but neither to abide indefinitely. It seems purely philosophical, but it addresses a certain psychological pathology we humans have always suffered at the limits of our understanding.

Basically this theory limits the first two axioms of the cosmological principal --(1) the homogeneous and (2) isotropic universe)-- by suggesting the following two axioms as more universal:

1) The Finite Rule: All material phenomena are finite in extent and constituent to a larger structures.

2) The Plurality Principal: All material phenomena are multiply manifest.

It sounds to me like it doesn't belong here at PF Cosmology subforum.

Empirical science depends on theorists restricting themselves to making predictive theories. Theories that predict new phenomenal (not already predicted by previously established theory) so that they can be tested.

It is not about imagining the universe in emotionally satisfying ways, or whatever else, it is about making quantitative predictions. And at this subforum we only deal with mainstream theories of this sort. Models of the universe that appear in peer-review professional publications. We don't dream up our own models, because we are interested in learning about and studying mainstream cosmology models. Typically the focus here is on the prevailing consensus LambdaCDM model.

I think this thread will probably be locked, or moved somewhere like Philosophy. I don't know what to advise you to do. Obviously you are pushing your website with your writings and visuals about the way you fantasize the universe. It is not appropriate to do that here. I don't know where it would be appropriate for you to go.

I think the big gap in what you are talking about is you don't have any equations describing gravity, that is, describing the dynamics of spacetime geometry. You are proposing a picture of the geometry of the universe but it seems kind of vague and unmathematical. In conventional mainstream cosmology we SEE the universe evolving geometrically and that evolution is related to our best understanding of gravity. The cosmological model is based on General Relativity (which has been tested). The universe is laid out the way it is and behaves the way it does because it obeys the equation of GR.
So there are all sorts of checks and interrelated things that you can test.

Cuetek

Apr2-08, 09:55 AM

It sounds to me like it doesn't belong here at PF Cosmology subforum.

Empirical science depends on theorists restricting themselves to making predictive theories. Theories that predict new phenomenal (not already predicted by previously established theory) so that they can be tested.

It is not about imagining the universe in emotionally satisfying ways, or whatever else, it is about making quantitative predictions.

Why does this not count as an empirical examination?

http://www.thegodofreason.com/rules-of-discovery.pdf

I only ask that you are equally diligent in restricting yourselves to my predictive theory and not "imagining the universe in emotionally satisfying ways."

My prediction is that the probability is 99% that the homogeneity of the Big Bang will dissipate and give way to a larger structure made up at least in part by other Big Bang structures.

The most obvious test of this theory would be to examine the WMAP data for a faint dipole. Such a dipole would only show up in the WMAP data if the Big Bang was in the neighborhood of 100,000 times (or less) the size of the visible universe. Based on the relative sizes of other scalar successions (say star system to galaxy) it would likely be much larger.

How is this not empirical?

my_wan

Apr2-08, 03:01 PM

I actually read the paper.. You did say predictions, oh well. In the conclusions it admits that the assignment of priors is subjective and therefore more qualitative than quantitative.

Your first prediction stated here requires a few billion years to be a prediction. Your dipole prediction assumes an upside down picture of what is being observed. It is the past we are observing. In fact I see nothing in the dipole thinking that is not supporting the standard model.

Now you quoted marcus, "imagining the universe in emotionally satisfying ways", and turned it into a characterization of those supporting the standard model. The realities are that this model started out hotly debated and mostly rejected until new information kept strengthening it. Even so, if it could be knocked off its pedestal I and many thousands of others would fight to do it first. Your accusation is nothing more than a red herring.

You had your say, it's time to end it....

Wallace

Apr2-08, 04:32 PM

Why does this not count as an empirical examination?

http://www.thegodofreason.com/rules-of-discovery.pdf

I only ask that you are equally diligent in restricting yourselves to my predictive theory and not "imagining the universe in emotionally satisfying ways."

My prediction is that the probability is 99% that the homogeneity of the Big Bang will dissipate and give way to a larger structure made up at least in part by other Big Bang structures.

The most obvious test of this theory would be to examine the WMAP data for a faint dipole. Such a dipole would only show up in the WMAP data if the Big Bang was in the neighborhood of 100,000 times (or less) the size of the visible universe. Based on the relative sizes of other scalar successions (say star system to galaxy) it would likely be much larger.

How is this not empirical?

We can already measure much more than you seem to realise or give credit for. Inflation predicts a particular power spectrum (or equivalently, correlation function) that describes the density field of the Universe. These statistical measures describe the amount of structure present on any given length scale. We can test these predictions against the density field seen in the CMB, and the theory passes with flying colours. We can also test it by observing the correlation function of the density field of galaxies from galaxy surveys and also the density field of dark matter through weak gravitational lensing surveys. These are less 'clean' measurements that the CMB however that do find a correlation function in agreement with the theory. This gives us confidence, empirically, that the theory has some merit.

Now, the theory doesn't cut off at the length scales corresponding to the largest lengths scales we could ever observe but instead makes definite predictions about what kind of structure is likely to be present in 'super horizon sized' perturbations (meaning structures larger than the observable Universe). We obviously cannot directly test this, however since it is a prediction from a theory that we can test at other scales we can have some (but not complete) confidence in it. The prediction is that on those large scales the perturbation amplitude is quite small, so we would not expect that the Universe outside of the observable chunk would be much different from the part we can see.

You seem to be enamored with Bayesian statistics, this is good, cosmologist now use Bayesian statistics almost exclusively since data is at a premium and we wish to make the best guess we can when things are not always obvious 'to the eye' in noisy data. But don't forget that the essence of Bayes's theorem is that your state of knowledge is always updated based on new evidence. If your theory does not include all the current evidence, including the observations that the amplitude of the correlation function reduces as lengths scales increase (so would be expected to be even smaller on super horizon scales), then it cannot be considered to be a 'Bayesian Cosmology'.

Still, I don't want to come across as being too harsh, it's great to toss different possibilities around, but the current cosmology theories weren't just dreamed up at the Pub one afternoon, they are the result of many years of theoretical and observational work by many people. Therefore it's hard to come up with something new that does a better job of explaining the data. I'm sure eventually that will happen, I suspect at least a few aspects of our current theories will eventually be drastically altered, but it's only by considering all of what we know that we can achieve any next step.

Cuetek

Apr2-08, 07:18 PM

Now, the theory doesn't cut off at the length scales corresponding to the largest lengths scales we could ever observe but instead makes definite predictions about what kind of structure is likely to be present in 'super horizon sized' perturbations (meaning structures larger than the observable Universe). We obviously cannot directly test this, however since it is a prediction from a theory that we can test at other scales we can have some (but not complete) confidence in it. The prediction is that on those large scales the perturbation amplitude is quite small, so we would not expect that the Universe outside of the observable chunk would be much different from the part we can see.

Thanks Wallace for being patient with me. I didn't post this stuff to insult people. I just wanted some responses like yours telling me how exactly my views are naive in light of the conventional wisdom. This definitely gives me something to work with. I've searched some of your terminology and and found some papers I need to try and understand. Thanks again.

Wallace

Apr2-08, 07:38 PM

Another useful term to look for is 'scale of homogeneity', I think that might get you quickly to the heart of the matter.

Cuetek

Apr2-08, 07:55 PM

Now you quoted marcus, "imagining the universe in emotionally satisfying ways", and turned it into a characterization of those supporting the standard model.

If the slight was good enough for Marcus to characterize the presumption that the Big Bang may be finite as feel-good idiocy on my part, then it's good enough for me to put back to him for being so dismissive of my wanting peoples honest reaction.

I'm not refuting the standard model. I'm saying that the effort to make any model a complete and sufficient description of everything is precisely where that model will ultimately be found weakest. If this idea is cause for disdain and derision, knock yourself out.

Cuetek

Apr2-08, 07:58 PM

Another useful term to look for is 'scale of homogeneity', I think that might get you quickly to the heart of the matter.

Oh yeah, that's it. Thanks again.

Cuetek

Aug4-08, 11:23 AM

Another useful term to look for is 'scale of homogeneity', I think that might get you quickly to the heart of the matter.

Well, gentlemen, (and MeJennifer) after carefully examining these articles on the scale of homogeneity, I don't think they are as conclusive as a few of you might imagine. I looked at some of these papers and they fall into two general categories to extend the homogeneity beyond the range of the visible universe. One category uses the recession data and another uses the CMB data.

One typical article in support of the cosmological principle is Martinez’s "Searching for the Scale of Homogeneity:"

http://www.ingentaconnect.com/content/bsc/mnr/1998/00000298/00000004/art00024

Using the red shift recession data, it claims "no hope for unbounded fractal distributions," which basically supports a total projection of the visible homogeneity. However, he bases his presumption on the two point correlation function which is dependent on the fair sample hypothesis which is itself a derivative of the cosmological principle. This is like saying, if the universe were homogeneous then it could be modeled like this and since the model is so beautifully compliant with respect to relativity then it is undoubtedly true.

This approach constitutes the same potentially true but ultimately false presumptions we have always made when characterizing the universe beyond the data at hand. We always make the presumption that the data we have is sufficient to explain "everything." This is what the cosmological principle is doing for us in modern cosmology. It makes an infinite universe compliant to a finite data set. But historically, the universe has always proven to be more diverse than is possible to determine from any finite local data set.

You may be surprised to find that there are also articles that do not explicitly support a totally homogeneous universe. Take Patricia Castro’s "Scale of Homogeneity from WMAP" which states:

http://arxiv.org/abs/astro-ph/0309320

"We review the physics of the Grishchuck-Zel'dovich effect which describes the impact of large amplitude, super-horizon gravitational field fluctuations on the Cosmic Microwave Background anisotropy power spectrum. Using the latest determination of the spectrum by WMAP, we infer a lower limit on the present length-scale of such fluctuations of 3927 times the cosmological particle horizon (at the 95% confidence level)."

Attacking the problem from a lower limit perspective is a far better strategy than presuming homogeneity and trying to indicate the absence of an upper limit. This approach addresses only what we can be confident in with respect to the local data rather than trying to corroborate an impossible thesis with a potential to range infinitely beyond the local data set.

If we were living on an electron of a hydrogen atom in the middle of the ocean, we would be perfectly justified in presuming the universe was made entirely of water molecules, and all our calculations would work perfectly, but we would still be wrong. All I'm saying is that a Bayesian examination across the widest possible spectrum of the existing data (the hierarchical structure of of the known material universe from quarks to galaxy clusters and across the history of scientific investigation) says that the universe is hierarchical and not homogeneous across all scales and that whenever we try to terminate that hierarchy is precisely where our theories have historically proven weakest. And the CP is that point of weakest presumption in modern cosmology.

For people to get upset to the point of indignation over the suggestion that the Big Bang may ultimately be a finite phenomenon is more an artifact of psychology than of science. The universe is not ours to claim total understanding beyond a reasonable projection of the data to a statistically relevant degree. That it is possible for the cosmological principle to be true is not the same thing as being inevitable.

-Mike

marcus

Aug4-08, 01:24 PM

If the slight was good enough for Marcus to characterize the presumption that the Big Bang may be finite as feel-good idiocy on my part, .

I did not. You were not being slighted. You must not have understood. I have often discussed the possibility that standard cosmology is spatially finite, in the sense of finite spatial volume. Several of us have (I am not alone in my interest in that case.) Several threads here at the forum about this.

By itself, bigbang finiteness is hardly a revolutionary idea :smile: there is even some data supporting it (not conclusive though).

For people to get upset to the point of indignation over the suggestion that the Big Bang may ultimately be a finite phenomenon ...

Again I think you must have misunderstood the point of others' comment. I don't see anyone who responded to you acting upset or indignant at all!

It's a general observation which bears repeating that we have to distinguish between universe models that are supported in detail by data, and make quantitative predictions so they can be tested by practical observations, on the one hand, versus, on the other hand, concepts that appeal to somebody's imagination and are proposed without some currently feasible method of testing.

If you want to call the latter "feel-good idiocy" well, those are your words and it is your perogative. But I wouldn't choose such language. Practical testability of scientific theories is a serious point and, as I say, bears repeating----no one should take offense at the reminder.

Cuetek

Aug6-08, 07:28 PM

I did not. You were not being slighted. You must not have understood.

The thread you quote form was between my_wan and myself. His exchange with me was far more contentious than yours. That he involved excerpts from your exchange with me is unfortunate in that they got tainted.

I have often discussed the possibility that standard cosmology is spatially finite, in the sense of finite spatial volume. Several of us have (I am not alone in my interest in that case.) Several threads here at the forum about this.

By itself, bigbang finiteness is hardly a revolutionary idea :smile: there is even some data supporting it (not conclusive though).

That would be the finite but unbounded model which fails in my estimate in the same manner that the infinite Big Bang model fails. Any model that serves as a complete structural description of physical reality is a psychological presumption and not a model that takes into consideration all the data. The data says we live in a material hierarchy.

The bulk of physical reality has repeatedly proven to be hierarchical even though we repeatedly try to terminate that hierarchy every time we devise some new theory by devising one that can be a potentially "complete" model. If we admit that the hierarchy is more likely, that means that we can never know the full extent of the structure. Using all scales that we have ever comprehensively examined is a more complete template for predicting the nature of the mega-scaled universe, than is taking the largest physical behavior we can see and devising some model that could exist as we always have in the past (crystal sphere, island universe, big bang)

I say that the Big Bang is a finite structure (of at least a million times the diameter of the particle horizon and probably much more) that is in turn constituent to a greater structure just like every other physical phenomenon ever examined. The expansion of spacetime could easily be the relaxation of the curvature of space from the cataclysmic reversal of a cosmic scaled black hole that belched up our local universe (or wormhole punched by a massive black hole as Hawking proposed).

Again I think you must have misunderstood the point of others' comment. I don't see anyone who responded to you acting upset or indignant at all!

My_wan was fairly indignant to the point of saying that I should stop posting He said: "You had your say, it's time to end it."

It's a general observation which bears repeating that we have to distinguish between universe models that are supported in detail by data, and make quantitative predictions so they can be tested by practical observations, on the one hand, versus, on the other hand, concepts that appeal to somebody's imagination and are proposed without some currently feasible method of testing.

If you want to call the latter "feel-good idiocy" well, those are your words and it is your perogative. But I wouldn't choose such language. Practical testability of scientific theories is a serious point and, as I say, bears repeating----no one should take offense at the reminder.

Both can be feel good idiocy. Certainly the scientific method is far less prone to such characterization, but not immune from it. The three tenets of the cosmological principle are ultimately impossible to corroborate, they are only disprovable.

I say that the bulk of the evidence for what exists in the mega-scales beyond the particle horizon lies in the 40 orders of magnitude of hierarchical consistency, not in the single order of magnitude at the scale of homogeneity of galactic clustering. Put yourself on an electron in the middle of the ocean and you would swear that the homogeneity of water molecules was absolute by all practical observations at larger scales. But you would be wrong. The material hierarchy of the subatomics in your local nucleus would continue beyond the ocean in the form a the planets etc.

-Mike

MeJennifer

Aug6-08, 08:18 PM

Another reason I can think of why knowledgeble people might want to stay away from the phrase "expansion of space" is that FRW universes have zero Weyl curvature. In fact they only have Ricci curvature and Ricci cuvature does not even apply to vacuum regions.

BoomBoom

Aug7-08, 09:14 AM

navneet023

Aug7-08, 11:18 PM

well...i wanted to ask one thing...everybody's saying that the expanding universe is like a inflating balloon...wid galaxies nd everyting as points on the the balloon...can u tell me wats inside of the baloon....??

one more thing i'd like to ask .... like where is our universe expanding...where...where is it placed.....where was the super dense super hot infinitely unstable point placed from which everyting came out....?

Plz...I know m sounding like an idiot...but i thought the same wen i was asking myself these questions.....

Cuetek

Aug8-08, 10:22 AM

I say that the bulk of the evidence for what exists in the mega-scales beyond the particle horizon lies in the 40 orders of magnitude of hierarchical consistency, not in the single order of magnitude at the scale of homogeneity of galactic clustering.

The trouble with this is that, even if it were true, it would be beyond our observational threshold. So to assume this is the case is idle speculation, just as assuming it is not the case is also speculation.

It makes logical sense to me, but without any evidence, science doesn't have anything to say about it....as it shouldn't.

To say that we have no evidence about it is not exactly true. We have generally the same type of evidence we use to establish the cosmological principle. That is we either project the two orders of magnitude (one order was a little skimpy) of the homogeneity we see at the largest scale out indefinitely or we project the 40 orders of magnitude of the material hierarchy out indefinitely. If the cosmological principle is good science, so is the the hierarchical principle.

That one of those projections allows a very specific field for us to project makes it seem more "reasonable" but there is actually less data to support it (2 orders of magnitude). That the other projection is conceptually vague the instant it begins to diverge from the homogeneity we presume in the first projection makes it no less accurate as far a projections go. That is to say, in both cases we are talking about the unknown, but not without any evidence.

The only real difference it should make in science is in what we expect to find. If we expect to find homogeneity we won't look very hard for any faint asymmetries in the CMB and recession data. And we should look just as hard for inhomogeneity as we do for homogeneity (the bulk of publications on the subject are looking for homogeneity).

We devise all sorts of expectations and calculations based on the cosmological principle that work out fine. But just because we can make an idealized model of a homogeneous universe that works mathematically, is not sufficient to rely on it beyond the range of data at hand. This is true for either case, but, if you don't look for another possibility, you're not likely to find it and the truth is, in a thousand years from now, we will have found all manner of things that weren't like we thought they'd be.

You might have the tendency to look at it as a purely philosophical question since we are talking about the nature of the universe beyond our ability to confirm. But the fact is, we have a much more extensive field of evidence in the material hierarchy than we do in the homogeneity of the galactic clustering and the cosmological principle is not considered to be merely philosophical. This makes the hierarchical principle at least as compatible with the scientific method as is the cosmological principle.

-Mike

BoomBoom

Aug8-08, 10:56 AM

But just because we can make an idealized model of a homogeneous universe that works mathematically, is not sufficient to rely on it beyond the range of data at hand. This is true for either case, ...

I agree. I think there are alot of assumptions out there that are accepted as fact, and I feel like science should be a little more skeptical about things we have no evidence of. I like caveats such as the universe "could be" like this instead of saying it "is" like this in cases where there remains an element of doubt and a lack of visual evidence.

That said though, if the universe is as you suggest, would this be a possible explanation for dark energy? If there was a whole lot more matter out there beyond our expanding "local" universe, would the gentle tug of it's gravity be enough to explain DE?

Cuetek

Aug8-08, 01:09 PM

well...i wanted to ask one thing...everybody's saying that the expanding universe is like a inflating balloon...wid galaxies nd everyting as points on the the balloon...can u tell me wats inside of the baloon....??

It's just an analogy, the whole balloon thing. It's a two dimensional representation (the skin of the balloon) of a three dimensional issue (visible universe). The inside of the balloon is not part of the analogy. A better analogy is the raisin cake analogy where as you cook the dough the whole cake expands with each of the raisins getting further and further away from each other.

one more thing i'd like to ask .... like where is our universe expanding...where...where is it placed.....where was the super dense super hot infinitely unstable point placed from which everyting came out....?

Plz...I know m sounding like an idiot...but i thought the same wen i was asking myself these questions.....

Not at all, navneet (at least not to me). I'm not really sure why the cosmological principle was adopted, but it was, and since it was adopted the only way a perfectly homogeneous universe could expand was if all of it was expanding equally. If this was the case then, even if the universe is infinite, it started out as both infinite and as a cosmic egg singularity. In which case, there was no prior context to this process. It started out both infinitely dense, yet infinitely vast in the instant of it's initiation. If it's not infinite then it's a closed universe that curves back on itself at some staggering volume, "outside" of which there is no existence.

Sounds totally whacky right? I think so too, although a great deal of math has been dedicated to describing just such a universe. But I have a more pedestrian model that might make sense to you, even if most of the other members of the Physics Forum will disagree strongly with it's tenets.

Since all material phenomena that we have comprehensively examined are finite in extent and constituent to larger structures I contend that the Big Bang is ultimately a finite phenomenon itself in a much larger surrounding materially hierarchical context just like the rest of everything else we ever discovered proved to be. And since black holes and the Big Bang are the only two phenomena that are associated with singularities, I suggest that the Big Bang is an enormous black hole that went kablewy.

If you were to examine a 13 billion light year wide section of a trillion trillion light year wide exploded black hole you might realistically expect to see everything around you appear to be heading away from everything else. Yet, ultimately it would be expanding "into" the surrounding context just like you imagine an expanding phenomenon to behave.

And since every physical phenomenon we ever comprehensively examined proved to be only one example of a class of similar phenomena, I would say that the surrounding context into which we are expanding might well be expected to have other really big black holes scattered about as well as some small fraction of them getting ready to go kablewy. Collectively (along with perhaps other similar scaled elements) these black holes might be expected to form even larger structures in an ongoing hierarchical universe that we will never be able to fully explore, much less characterize.

Such a universe would virtually eliminate the ability for us to ever understand and model it. It would be permanently beyond our ability to fully fathom (just like it always has been). This inability to comprehensively describe the universe is psychologically challenging for science to admit, but it is almost inevitably true as the history of science clearly indicates. It is, however, easier for me, personally, to imagine such a universe than to imagine the Big Bang as currently characterized.

-Mike

Cuetek

Aug8-08, 06:32 PM

I like caveats such as the universe "could be" like this instead of saying it "is" like this in cases where there remains an element of doubt and a lack of visual evidence.

That said though, if the universe is as you suggest, would this be a possible explanation for dark energy? If there was a whole lot more matter out there beyond our expanding "local" universe, would the gentle tug of it's gravity be enough to explain DE?

Dark energy to me is more probably a product of our misinterpreting vast scale circumstances that affect our local disposition. Dark energy is not as certain a theory as, say, relativity, and as such, to me it belongs in the category you suggest above with an element of doubt formerly associated with it.

I am a Bayesian. I use Bayesian logic in suggesting that the full scale material hierarchy is a better template than the single scaled homogeneity. If the material hierarchy persists then there must also persist a hierarchy of forces beyond the four we know to organize the ongoing structures. Dark energy to me seems to be a good candidate for the small scale emergence of the next force in line that exerts after gravity in the direction of larger scales.

But I also think that there are so many potential scenarios involving normal gravity like enormous gravity waves or proximity of large background gravity fields (black holes) at vast scales that may even serve explain the acceleration of the expansion as an artifact of our transition through these background circumstances. At any rate, I think science doesn't pay enough attention to the possibilities of diversity at larger scales in addressing issues like DM and DE.

-Mike

mysearch

Aug9-08, 04:32 AM

Hi, it is not my intention to divert this thread, but some of the previous posts seem to be touching on the general state-of-play of cosmology. I think many newcomers to cosmology, like myself, are initially seeking to gain some general understanding as to what aspects of the standard model are supported by verified science and what might be more honestly classified as speculation, although mathematical hypothesis might be the preferred term.

In fairness to the mainstream, this situation is often compounded by the myriad of ideas from `free-thinkers`, which while I would not like to see suppressed in this forum, must ultimately substantiate their views by the same rigor expected of mainstream science. If not, an already confused situation simply becomes ever more confused via yet more unsupported speculation.

This said, the purpose of this post was to get the opinion of an article, which I hope is not considered too tangential to the current discussion that I recently came across as I continue my own reading into the issues surrounding cosmology. I have included an extracts from the article and a link to the full article below. At face value, the comments seem quite negative, but the author Dr. Richard Lieu seems to be a respected professor of physics at the University of Alabama. However, rather than just accepting his comments, I would be interested in the opinions of some of the members of this forum, especially those working in this field, who may want to respond to this article:

http://arxiv.org/PS_cache/arxiv/pdf/0705/0705.2462v1.pdf
Abstract: Astronomy can never be a hard-core physics discipline, because the Universe offers no control experiment, i.e. with no independent checks it is bound to be highly ambiguous and degenerate. Thus e.g. while superluminal motion can be explained by Special Relativity, data on the former can never on their own be used to establish the latter. This is why traditionally astrophysicists have been content with (and proud of) their ability to use known physical laws and processes established in the laboratory to explain celestial phenomena. Cosmology is not even astrophysics: all the principal assumptions in this field are unverified (or unverifiable) in the laboratory, and researchers are quite comfortable with inventing unknowns to explain the unknown. How then could, after fifty years of failed attempt in finding dark matter, the fields of dark matter and now dark energy have become such lofty priorities in astronomy funding, to the detriment of all other branches of astronomy?

Conclusion: Cosmologists should not pretend to be mainstream physicists, because there is only one irreproducible Universe and control experiments are impossible. The claim to overwhelming evidence in support of dark energy and dark matter is an act of exaggeration which involves heavy selection of evidence and an inconsiderate attitude towards alternative models with fewer (or no) dark components. When all evidence are taken into account, it is by no means clear that LCDM wins by such leaps and bounds.

Cuetek

Aug9-08, 12:06 PM

Hi, it is not my intention to divert this thread, but some of the previous posts seem to be touching on the general state-of-play of cosmology.

I guess I started this thread and IMHO your contribution is spot on. I am woefully lacking in the mathematical chops sufficient to assert some of my more intuitive conclusions. Having some credentialed commentary inserted into the discussion to formalize some of the intrinsic uncertainties involved in modern cosmology is exactly what this thread needs.

Later -Mike

yuiop

Aug9-08, 06:17 PM

By itself, bigbang finiteness is hardly a revolutionary idea :smile: there is even some data supporting it (not conclusive though).

The latest data suggests Omega is about 1.02 suggesting a closed universe but there is sufficient error despite billionds of dollars spent on reasearch that a universe with Omega exactly =1.00 and flat is not excluded. As I understand it Omega =1.00 implies an infinite universe and Omega >1.00 implies a finite universe. What I want to ask here is if the cosmological constant changes that interpretation? Does a cosmological constant of greater than zero suggest a universe with total Omega less than 1.00 can be finite or vice versa?

marcus

Aug9-08, 06:32 PM

...As I understand it Omega =1.00 implies an infinite universe and Omega >1.00 implies a [spatially] finite universe.

I agree. I think your understanding is right. I put in the word spatial to make it clear.

What I want to ask here is if the [positive] cosmological constant changes that interpretation?

No it doesn't AFAIK. The cosmological constant we see evidence of, and most people mean when they say that, is positive. so for clarity I put that in. It doesn't change the spatial finiteness or infiniteness.

If Omega > 1 then it's spatial finite and even if you put in Lambda it is still spatial finite.

If Omega = 1 then it's spatial infinite and even if you put in Lambda it is still infinite.

Same for Omega < 1.

marcus

Aug9-08, 06:41 PM

The latest data suggests Omega is about 1.02 suggesting a closed universe...

reference to latest WMAP data here:
http://physicsforums.com/showthread.php?p=1636651#post1636651

95 percent confidence interval for Omega using WMAP5 + SN + BAO
is [0.9929, 1.0181]

That's on page 6 of the WMAP5 paper reporting implications for cosmology. If you just base it on WMAP data you get something about the same as that. This just happens to be what you get if you include the other two datasets.
BAO (baryon acoustic oscillation data) depends on galaxy surveys and SN is supernovae.

On page 4, figure 2, of the same paper they give a lower bound for the radius of curvature of space, assuming it is a 3-sphere, that is the 3D analog of the surface of a balloon. the estimate is 104 billion lightyears.

that is the radius of the balloon-analog is AT LEAST that much. so you can figure the circumference that corresponds to 104 billion and it is at least that.
and you can calculate the 3D volume and it is at least that volume---at the present moment.

the formula for the 3D volume of a 3-sphere is 20 x R3 where R is the radius of curvature. we don't assume an extra dimension in which the R exists as a real distance, it is just a quantity describing the overall average curvature. 20 is meant as the rough value of twice pi-square.

I think if you asked for a 70 percent confidence interval you would get something entirely > 1. Probably centered around 1.01 and something like
[1.004, 1.016] just guessing. They published something like that with the WMAP3 data a couple of years ago. But this time, with the WMAP5 data, they only gave this 95 percent interval that spills over a little bit into Omega < 1.

yuiop

Aug9-08, 11:10 PM

Please take a look at this image (http://www.astro.ucla.edu/~wright/triptych-SNe-CMB-BO-H0-75.gif) from this Ned Wright webpage (http://www.astro.ucla.edu/~wright/sne_cosmology.html).

In the text Ned states "Clearly if one assumes the Universe is flat the supernovae favor w = -1.3 which leads to a "Big Rip". But if one looks only at the concordance between the four datasets, the standard flat ΛCDM model with w = -1 is preferred."

To me, there is no concordance between the supernova data and the other 3 datasets. I have attached a modifed version of ned's image which I have converted to black and white, enlarged and added coloured centrelines for each dataset to make the concordances clear. If you look at the rightmost image with w=-1.3 then there is a very good coincidence of 3 out of 4 of the datasets if we ignore the supernova data. No adjustment of the equation of state parameter w can make the supernova data coincide with the other data and trying to make it match makes the other 3 data sets diverge. It surprises me that that Ned chose the centre picture with w=-1 as the best fit and his choice seems to be based on a desire to choose a fit that is on the flat Omega=1 line. I have highlighted the coincidence point in the w-3 image with a white and red dot. Why doesn't anyone else mention what a bad fit the supernova data is with the data from other sources?
The best fit in my opinion is the Omega>1 and w= -1.3. If you look at this image (http://www.astro.ucla.edu/~wright/Wm-Wv-wMAP5yr-wSNe.gif) from the same webpage which is based on 2008 data it can be seen that that the Supernova data by itself puts Omega in the 1.3 range which is miles away from the flat universe line.

marcus

Aug10-08, 08:12 AM

Please take a look at this image (http://www.astro.ucla.edu/~wright/triptych-SNe-CMB-BO-H0-75.gif) from this Ned Wright webpage (http://www.astro.ucla.edu/~wright/sne_cosmology.html). ...

that page is interesting several ways. Thanks for mentioning it, Kev. I understand that the plots you focus on come right at the end and are concerned with the DE equation of state. Should one think of it simply as w = - 1, or contemplate some other possibility like w = -1.3?

You also distrust the alleged concordance among CMB+BAO+SNe, where it looks like the first two agree all right but SNe is out of line.

I can see what you are talking about, but my reaction is (you might say) more conservative.

What I see happening with the Ned Wright page is more than just asking about w, the EOS.
He is looking at the Kowalski etal (April 2008) paper. And he isn't satisfied with it because he doesnt think they considered enough different cases. So he re-analyzes their SNe data. He rebins it. He adds new cases and plots different color solid and broken curves.

I went back and looked at the Kowalski etal 2008 paper that was Ned Wright's starting point
=========================

I can't give you a single clear response, but I did notice something in Kowalski etal TABLE 6 on PAGE 23. Instead of just assuming flat Omega = 1 as they usually do, they included a BEST FIT case allowing Omega to not be exactly equal to one.
and they got a best fit of Omega = 1.009
with a range of about [1.00, 1.02]
This is best fit for all the datasets: SNe + BAO + CMB.

What I see Ned Wright doing, on the page you linked, is primarily trying more cases where Omega is allowed to be > 1. He augments Kowalski etal analysis to be more openminded. The central figure on the page---the one he appends all those tables to---is called "332 SNe SCP Union Catalog"
Where he says "The dashed magenta curve is the best closed dark energy dominated fit to the supernova data alone."

To me the dashed magenta looks like better fit than the solid magenta and I think that is one of the ideas that Ned Wright is getting across with that figure.

Particularly since for the case z = 1.55 the sigma, shown by the vertical uncertainty bar, is so large that hitting the centerdot means relatively little.
I pay more attention to the nearly exact hits at z = 1.275 and z = 1.367, with much smaller sigma. The table right after the figure duplicates the information so we know what numbers he is plotting. food for thought.

danda22

Apr15-09, 08:10 AM

Who makes the claim the the Big Bang is a finite structure?

hmm ok i realise this has probably already been answered in full. but as far as i know all experts have claimed that the big bang was just one giant explosion. how is it possible. for something that is infinite. to explode? infinite.. encompassing all.. if it exploded... O.o that is mind boggling........... the big bang must of been finite. which therefore means that. the universe must also be finite.. even though it is increasing in size by the second

Cuetek

Apr20-09, 03:42 PM

how is it possible. for something that is infinite. to explode? infinite.. encompassing all.. if it exploded... O.o that is mind boggling........... the big bang must of been finite. which therefore means that. the universe must also be finite.. even though it is increasing in size by the second

The definitive and probably final answer is, no one knows. Right now, it is debated that the universe may be finite but unbounded like a three-D equivalent of the surface of a sphere (some takers, but not so many lately) or infinite and homogeneous (a great deal of reasonably conditional concurrence).

Using math that conforms to the tenets of the cosmological principal and relativity, these two theses are considered the totality of the options to within what I imagine to be at least a 99% certainty among most physicists. Talk to any one of them long enough about the inherent difficulty of conclusive data with respect to the presumptions of the cosmological principal, and that confidence level will generally drop to somewhere between 98% and 50% as evidenced by the progression of the first two-thirds of this thread.

As stated earlier in the thread, I feel that the current version of the Big Bang is an idealized model of how an expanding universe would behave if the cosmological principal were true. But the cosmological principle is more likely a coping mechanism to make the balance of the unobservable universe conform to what we can see of it, rather than a valid projection of the physical continuum. I feel that the expanding profile of the mutually receding galaxy groups (the evidence for the Big Bang) will ultimately prove to be both finite in extent and multiply manifest (other Big Bangs out there) just like every physical structure or behavior ever observed.

Every physical behavior or structure ever observed proved to be both finite in extent (finite rule) and multiply manifest (plurality principle). From quarks to molecules to flatworms to physicists to supernovae to galaxy clusters, whatever physical phenomenon you care to identify, you can find both it's spatial limits as well as other examples of it scattered about the universe. The same will almost certainly be determined to be the case for the phenomenon of the Big Bang, provided the species survives it's social adolescence long enough to develop the necessary technology.

-Mike

marcus

Apr20-09, 05:57 PM

but as far as i know all experts have claimed that the big bang was just one giant explosion.

No expert has claimed that the big bang was just one giant explosion. Someone who said that would necessarily be ignorant, and not an expert.
The explosion idea is probably the most common mistake that uninformed people make.

The common misconceptions about the big bang were described in the Scientific American of March 2005 in an article by Lineweaver and Davis. The explosion misconception was one of those which they tried to kill off.

It would be good if you would read the SciAm article. I always keep a link to it in my sig. It is the princeton.edu link in small print at the end of the post. The Princeton astro department uses the article in their intro astro course.

marcus

Apr20-09, 06:13 PM

Who makes the claim the the Big Bang is a finite structure?

I do.

-<[{( Crackpot Alert!)}]>-

Erm... labelling your post with "crackpot alert" is not a good start. Have your read the PF rules (http://www.physicsforums.com/showthread.php?t=5374)?

Cuetek later changed the word "crackpot" to "speculation". Whatever you call it, it is idiosyncratic and way off the mainstream to argue that the big bang had to be a finite volume.

Our first job is to understand the standard cosmo model and what it says. The standard model fits the data extremely well and you have to have some solid reasons to go against it.

There is nothing in the standard model which says that the state around the start of expansion had to be finite volume. Expansion could have begun with an infinite volume. It was not an explosion (that is a common pop-sci misconception).

The standard LCDM (lambda cold dark matter) allows for at least two cases---expansion could have begun with a finite volume (e.g. boundaryless like a 3D hypersphere) or it could have begun with an infinite volume (e.g. boundaryless like Euclidean 3D space).
Observationally it may be possible to distinguish between these two cases in the future, so we will be able to infer which. Meanwhile, until more precision data, two versions of LCDM.

Cuetek

Apr26-09, 09:09 PM

Bringing up the crackpot comment for good measure, eh? Be that as it may.
The standard LCDM (lambda cold dark matter) allows for at least two cases---expansion could have begun with a finite volume (e.g. boundaryless like a 3D hypersphere) or it could have begun with an infinite volume (e.g. boundaryless like Euclidean 3D space).

Historically speaking, all cosmological explanations about the nature of the universe beyond observable space are found to be incorrect due to the discovery of unsuspected diversity that lies beyond. The sequence of those corrections as time goes by is as follows: What ever describes the universe as a complete model is corrected as only locally relevant by the discovery of further structural diversity at greater and greater scales. You may say what you like about how your idealized model may suffice under it's own presumptions, but don't be surprised when the universe diverges from your presumption.
Observationally it may be possible to distinguish between these two cases in the future, so we will be able to infer which. Meanwhile, until more precision data, two versions of LCDM.

If history is any indication, neither will prove to be more than a regional descriptor of a hierarchically diverse universe. Humans like to imagine some complete and sufficient description of the universe. That's a fools ploy. The universe always has more to offer beyond our current view. Taking that inevitability formally into consideration is the smart perspective. Expecting the conventional wisdom to change dramatically is always a better bet than thinking it to be pretty much accurate with only a few details to sort out. Those details tend to hide whole schools of thought.

Sure, the Big Bang will be the predominant effect for many thousands of times the diameter of the particle horizon. But if history holds true, the Big Bang will eventually dissipate, terminate and give way to larger structures as has always been the case.

-Mike

yuiop

Apr27-09, 12:40 AM

If the big bang happened everywhere at the same time, then the problem I have with an initially infinite universe, is how was such an event synchronised? An initially infinite universe would require infinitely fast signals to coordinate a simultaneous start time everywhere and that would require a hitherto unknown FTL signalling mechanism. The requirement for the big bang to start everywhere simultaneously is a requirement that comes from the constraint that the universe is homogenous on large scales.

In short, it would seem that an initially infinite universe requires faster than light communication or rejection of large scale homogenous principle.

Cuetek

Apr28-09, 10:47 AM

In short, it would seem that an initially infinite universe requires faster than light communication or rejection of large scale homogenous principle.
Yeah, Kev, the idealized notion of either an infinitely vast, infinitely dense continuum or a finite yet enormous singularity as the cosmic "starting point" has always been the boogy man behind modern cosmic reasoning.

To imagine that such neat arrangements of the entire context of reality are anywhere close to being true descriptors is not only difficult to comprehend under current theoretical knowledge, it is historically "the man behind the curtain" of all future expansion of astrophysical understanding.

In that all material phenomenon ever examined have proven to be finite, multiply manifest, and constituent to a larger contexts (both material and temporal) so too will the Big Bang be found to be a very large, but finite phenomenon in an indefinitely diverse surrounding context. In that the black hole is the only astronomical object other than the Big Bang to which we attribute singularity, that the black hole is the destination for all matter, plus the notion that a black hole can get as large as necessary to contain whatever amounts to a Big Bang's worth of matter, it is far more likely that the Big Bang is some normal stage of a black hole's life cycle than the complete and sufficient descriptor of all reality we like to imagine it to be.

Imagining ourselves instead to be on the surface of an electron in an expanding plasma field of an early stage Supernova gives us a fairly plausible allegorical context for our current foolishness. The universe always has another hierarchical context waiting in the wings. Even after 2000 years of this same sequence of discoveries, we still try to define what we see at any given time as a complete model when time and again we are shown the truth of the matter. The universe is bigger and more involved that we can see from here. Period. That is the field of evidence at hand. That's what the historical data unequivocally indicates. We think we are smart, but we are only theoretical giants. We are psychological dwarfs.

-Mike

Havanyani

Dec26-09, 06:23 PM

You may coin this as my Principle: "Infinite space is not capable of objective existence". Where in an infinite space can you place anything? An infinite space has no frame of reference for anything it may contain. But spacetime can grow towards infinity in that the Universe may continue to expand indefinitely. Still, that will never make it infinite. A sphere or a ring may be unbounded, but that is not infinite. We know its area or its circumference, respectively.

I have read a lot about the volume of the universe and how it is finite and unbounded et cetera. How does one resolve the problem of space-time interconvertibility? Is the volume of the universe measured in cubic light years (distance) or in Giga years (time). The beginning of the universe is about 14 billion light years away (a measure of distance), yet it occurred 14 billion years ago (time). The boundary limit of the universe is made up of the Beginning, the Big Bang, which is all around us, 14 billion light years away. We cannot go farther than the beginning in our attempts to measure its diameter. Looking yonder is really looking inwards. We are trapped in this thing.

twofish-quant

Dec27-09, 01:00 AM

The only real difference it should make in science is in what we expect to find. If we expect to find homogeneity we won't look very hard for any faint asymmetries in the CMB and recession data. And we should look just as hard for inhomogeneity as we do for homogeneity (the bulk of publications on the subject are looking for homogeneity).

The tests are similar, and the fact that people haven't found inhomogeneity isn't for lack of trying. Also I'm not expecting anything, but as a theorist, I'd be *MUCH* more interested in signs of inhomogeneity.

If there is a specific measurement for inhomogenity that you think should be used but hasn't, then that's worth a paper.

But just because we can make an idealized model of a homogeneous universe that works mathematically, is not sufficient to rely on it beyond the range of data at hand.

Actually it is. You make an idealized model of the universe and then you look at the data to see how it breaks. It's really obvious for example that the universe *isn't* homogeneous at small scales, and thing get put in as corrections to the model. If you want to introduce deviations at large scales, it's not hard to put those in also.

The current state of play is that it's likely that the length scale at which things are homogenous is much larger than anything that we can easily observe. Also there is an interesting theoretical reason for this. If the big bang started out very inhomogenous, cosmic inflation is going to smooth things out so that any inhomogenity is going to be at length scales that we can't observe (which was a *big* problem with BB models in the 1970's).

If it was the situation that the assumption of homogenity *was* causing some sort of observational blind spot, then this would cause a problem, but I don't see any reason to think that is the case.

Also assumptions are assumptions. Just because I assume something doesn't mean I believe it.

twofish-quant

Dec27-09, 11:18 AM

Every physical behavior or structure ever observed proved to be both finite in extent (finite rule) and multiply manifest (plurality principle).

That may be because if there are lots of copies of something, you are more likely to find one. The trouble with "principles" is that while they may be good ad-hoc rules for making guesses for what direction to head toward while you are stumbling in the dark, it doesn't lead to particularly good physics.

From quarks to molecules to flatworms to physicists to supernovae to galaxy clusters, whatever physical phenomenon you care to identify, you can find both it's spatial limits as well as other examples of it scattered about the universe.

But that's because you are looking only for things with multiple examples. To give an example of a phenonmenon with no spatial limits or other examples of it scattered about the universe, let me present the bankruptcy of Lehman and the near collapse of AIG. This is not a spatially limited phenonmenon. Lehman never went bankrupt in the history of the universe and never well again. To give another example, the industrial revolution or the computer revolution are non-spatial things that never happened before.

One reason that astrophysics and cosmology is useful in finance is that in finance you have to deal with a lot of "one-off" phenonmenon that aren't exactly like anything that has ever happened before or anything that will ever happen again.

twofish-quant

Dec27-09, 11:56 AM

Using the red shift recession data, it claims "no hope for unbounded fractal distributions," which basically supports a total projection of the visible homogeneity. However, he bases his presumption on the two point correlation function which is dependent on the fair sample hypothesis which is itself a derivative of the cosmological principle.

It really isn't. It's saying that the universe cannot have a certain type of homogeneity. Again, there is a difference between I can show that X is false, and I cannot rule out that X is true or not. It turns out with the current data you *can* rule out certain fractal distributions of the universe.

This approach constitutes the same potentially true but ultimately false presumptions we have always made when characterizing the universe beyond the data at hand. We always make the presumption that the data we have is sufficient to explain "everything."

No we don't. We have data. We try to figure out as much from the data as we can. Using the data we have we can usually rule out certain scenarios. Also, there are some theoretical reasons to question the cosmological principle, and there are some people that really have some attachment to the anthropic principle.

If we were living on an electron of a hydrogen atom in the middle of the ocean, we would be perfectly justified in presuming the universe was made entirely of water molecules, and all our calculations would work perfectly, but we would still be wrong.

Or we could be right, or it may not matter. A lot of equations in physics are of the form "assume a spherical cow". You make an assumption that may be wrong, or you make an assumption that you *KNOW* is wrong, so that you can do a calculation and figure out something about the situation you are looking at.

For most cosmological calculations it turns out that it doesn't *matter* what the super-large scale structure of the universe is, so you can assume that everything is the same, since that lets you do a computation and it greatly simplifies the math.

All I'm saying is that a Bayesian examination across the widest possible spectrum of the existing data (the hierarchical structure of of the known material universe from quarks to galaxy clusters and across the history of scientific investigation) says that the universe is hierarchical and not homogeneous across all scales and that whenever we try to terminate that hierarchy is precisely where our theories have historically proven weakest.

And I'm arguing that this notion is completely flawed because you are taking data from a known region and extrapolating it to an unknown region. Sometimes you have to look in the mirror and just say *I DON'T KNOW* and my experience is that you are better off is you just say *I DON'T KNOW* than to assume that you do know something you don't.

The other issues here is that the hierarchy does terminate. Electrons are point objects, and the Heisenberg uncertainty principle basically says that there is no structure below the quark scale.

And the CP is that point of weakest presumption in modern cosmology.

Maybe, but the cosmological principle is a rule of thumb, and it's something that shouldn't be taken too seriously. If you ask a random sample of cosmologists and ask them about the super-large scale structure of the universe, you'll get a diverse set of answers which basically boil down to "I don't know."

Also the fact that the universe is more or less homogenous at certain scales is an observational result, not a theoretical assumption. It's actually something that caused all sorts of problems in the 1970's which were fixed by inflation. The idea behind inflation is that because of inflation, we have homogenity at very large scales because any inhomogenous before inflation were washed out when the universe expanded extremely rapidly.

For people to get upset to the point of indignation over the suggestion that the Big Bang may ultimately be a finite phenomenon is more an artifact of psychology than of science.

It's not. It's more frustration when people come up with strawman arguments.

Also, no one is going to get annoyed if you *suggest* that the BB is a finite phenonmenon. A lot of annoyance comes in if you *insist* that the BB is a finite phenonmenon, because to justify that you have to use arguments that are basically outside the realm of science. If you come up and argue that the big bang *may be* a small part of a larger whole, that's not controversial at all. It's when you come up and say that the BB *is* that way, that you cause problems since you are trying to justify this by arguments that are philosophical rather than scientific.

People do get very touchy about distinguishing what the data says and what it doesn't because there is an effort to prevent "religious wars." If you look at the data, you can come to some consensus about what it says and what it doesn't. If you start going beyond the data and start making guesses based on quasi-religious principles, there isn't any way of resolving disputes. Personally, being a Buddhist, I have some totally nutty ideas on the ultra-large scale structure of the universe (i.e. that after one dies one ends up reincarnated in some other part of the cosmos), but unless I have data, that stuff stays out when I put on my physicist hat.

That it is possible for the cosmological principle to be true is not the same thing as being inevitable.

And I don't think that anyone in the field thinks otherwise. One thing about cosmological is that the cosmological principle has undergone some severe hits in the last decade to the point that there are people that seriously suggest that we ought to abandon it as a rule of thumb.

twofish-quant

Dec27-09, 12:18 PM

To imagine that such neat arrangements of the entire context of reality are anywhere close to being true descriptors is not only difficult to comprehend under current theoretical knowledge, it is historically "the man behind the curtain" of all future expansion of astrophysical understanding.

But if you have to do a calculation based on available data, you remove any complexity. It's the old joke "assume a spherical cow". Of I have to do a calculation and I don't know the shape of a cow, I assume that it's a sphere, because with that assumption I get results which I can compare with observations. If I stop everything and don't guess at a shape, I don't end up with any theoretical results that I can compare with observations.

In order to get to the truth of the situation, you have to make calculations based on assumptions that could be false or sometimes that you *know* are false. If you want me to make a quick calculation of the gravitational pull of a cow, my first calculation will assume the cow is spherical even though I know that the cow isn't.

Similarly, the FRW metric starts with the (manifestly incorrect) assumption that the universe is perfectly homogenous (which it isn't).

In that all material phenomenon ever examined have proven to be finite, multiply manifest, and constituent to a larger contexts (both material and temporal) so too will the Big Bang be found to be a very large, but finite phenomenon in an indefinitely diverse surrounding context.

That's a *huge* philosophical assumption, and one that I personally find untrue. One thing that you quickly figure out when you study supernova and galaxies and stars, is that each one is unique. There is no supernova that was exactly like 1987A and there never will be again. There is no object in the universe which is exactly like the moon.

Now to gain some sort of understanding of what is going on, you do try to classify and analogize, but you do find out that astronomical objects are unique once you see them clearly.

The other thing is that "we've never see this before, therefore it can't happen" is something that doesn't work for me. I work on Wall Street and the idea that the future will be anything like the past is something that will get yourself bankrupted if you take it seriously enough. One-off phenonomenon *routinely* happen.

It so happens that the methods of analysis used in physics work best when you have multiple similar objects (which is why you end up with a mess when you apply them to social sciences), but if you spend all your time looking at blue objects, you can't conclude that everything in the world is blue.

Imagining ourselves instead to be on the surface of an electron in an expanding plasma field of an early stage Supernova gives us a fairly plausible allegorical context for our current foolishness.

Science doesn't work through allegories.

The universe is bigger and more involved that we can see from here. Period. That is the field of evidence at hand. That's what the historical data unequivocally indicates. We think we are smart, but we are only theoretical giants. We are psychological dwarfs.

I see things very differently because I've been in finance and as the old saying goes "past experience is no guarantee of future results." Just because you've *never* seen something happen before, doesn't mean that it can't happen. So how do you deal with things that have *never* happened. Well.... Thinking about that is why I like my job (and why banks hire astrophysicists).

I really think you are punching a strawman since you are criticizing people for beliefs that most of them don't hold. All I'm saying is that when presented with a lack of evidence, the logical thing to do is to say "I don't know." I can guess, but I really don't know. It's really important to distinguish from what you *know* to what you are merely guessing about, since thinking that you know something that you don't tends to blind you to incoming data.

I don't see why that's particularly controversial.

Cuetek

Dec27-09, 01:52 PM

twofish-quant

Dec27-09, 07:51 PM

Once again, the cosmological principle is based on taking the symmetry seen at a single scale and projecting it however necessary to devise an ostensibly complete and sufficient model of the cosmos that by definition requires terminating the material hierarchy of the universe.

I'm not interested in making complete and sufficient models of the cosmos. My interest is to create models which summarize the essence of a physical process, which means removing anything that isn't essential to the model. If I want to calculate helium abundances in the BB, I start with the assumption, and possibly wildly incorrect assumption that the universe is homogeneous, since if I don't I'm not going to get any predictions out. It turns out that if I make that assumption I get out good helium numbers so that the actual reality of the situation is close enough to my assumptions that I can use them to get helium numbers.

In turns out that in some situations (quantum field theory) my assumptions lead to internal self-contradictions, which I have to deal with. It turns out that in assuming that the universe is infinite, there aren't any theoretical contradictions. At that point I look for differences in observations, and there aren't any. Which means that when I run my models, I can assume that the universe is infinite, and that will give me good enough numbers for the things that I happen to be interested in.

The sum of the data is unambiguously in favor of a hierarchical universe extending in both directions of scale beyond our detection.

No it's not. Heisenberg uncertainty theorem puts a lower limit on structure. As far as upper limits, there is no evidence of any hierarchy outside of the observable universe. That's not to say that there isn't. It's just to say that people have looked for it, and we haven't found anything.

You cannot rationally refute the finite rule or the plurality principle.

If I can't rationally refute it, then we are having a theological argument rather than a scientific one. This is the big problem that I have with your insistence that the universe *has* to work in a certain way. You are making some philosophical assumptions about how the universe works. That's fine. If it gives you a research program, its wonderful, but what I'm telling you is that science doesn't work this way because it *can't* work this way.

It turns out that different people have different philosophical assumptions so if you try to piece together how the universe works that way, you end up with "religious wars." People insisting that their philosophical assumptions are correct and privileged. You have some assumptions about how the world works that I just don't hold, and we try to have this discussion without observational evidence, we are just going to get nowhere.

Cosmologists and physicists do share a minimal set of philosophical assumptions that allows people to communicate, but it has to be a very minimal set. You are stating a set of assumption, and if I say, I just don't accept those, then we are at an impass. Your only response would be that I'm somehow irrational, but I don't *seem* irrational.

[All observable material structures have proven over time to be finite in extent and constituent to larger structures. All observable phenomena have proven over time to be multiply manifest. Presuming the data accumulated across all scales as more significant than the data from any single scale is clearly the more rational approach.

And I say no it isn't. But we are having a theological discussion here, and not a scientific one. This is the type of discussions theologians have all the time. It's the type of discussion that physicists avoid if at all possible, and there is no reason I can see to bring up this discussion since we are talking about things that are observationally unfalsifible. Now if we did have observations that could resolve this, then it again would be a pointless discussion since we just look at the observations.

We are no more the center of the scalar universe than we are at the center of the spatial universe.

People that support the anthropic principle would disagree with that statement.

It's time to accept the high probability that all human knowledge is more realistically viewed as a set of local relationships in an indefinitely vast, ongoing hierarchical continuum.

At extremely large scales this is a theological discussion. At small scales it isn't because Heisenberg wipes out any hierarchical structure that occurs below the level of quarks and electrons. Unless there is something very seriously wrong with the way we understand QM, there is no structure smaller than quarks and electrons.

DevilsAvocado

Dec27-09, 11:49 PM

The sum of the data is unambiguously in favor of a hierarchical universe extending in both directions of scale beyond our detection.

I’m only a layman and absolutely not a mathematician, but your 'scientific proof' (numerical justification) seems very strange... even to me.

http://www.thegodofreason.com/rules-of-discovery.pdf
p(E|Fm) = The probability of finding evidence E (the existence of smaller objects collectively assembled within the current object) assuming that phenomenon Fm (all objects being finite and multiply constituent of a larger object) is true. This value is necessarily (tautologically) 1 or true.

Says who!? This is not numerical justification. This is recursive justification – My theory is correct and therefore it’s true. (or you could say its tautological guessing)

(Objection #2; Does Bayes' theorem really allow 1 for true and 0 for false? Division by zero is always hard work...?)
So we take one of the smallest object we can currently detect (the neutron) that we know contains yet smaller objects (quarks) ...

Recursive justification again. Why not start with a quark like the electron (that is clearly detected by my old TV). In this case p(E|Fm) is surely not 1 or true.

But I’m going to be nice, and let you have p(E|Fm) = 1 with the following complaint:
p(E|~Fm) = The probability of evidence E (the existence of smaller objects collectively assembled in the current object) being true presuming that our hypothesis Fm (all objects are finite constituents of larger objects) is not true. We will assign p(E|~Fm) = 0.5 generously allowing that the hierarchical evidence we see in all matter observed so far has an equal chance of being some how unrelated contrary to our hypothesis.

Ehhh... excuse me, but this Boolean algebra is probably turning Bayes in his grave. If p(E|Fm) = 1/true then p(E|~Fm) must be = 0/false! This value cannot be picked by 'generosity'!?

True = 1
False = 0
Not True = False
Not False = True

Let’s run Bayes' theorem with the correct values:
p(Fm|E) = \frac{1 * 0.5}{(1 * 0.5) + (0 * 0.5)}\,

p(Fm|E) = 1

The calculated Bayesian probability of neutrons being finite constitutes of yet larger objects is overwhelmingly true... and the proceeding sequence to bigger objects will be a joke...

Sorry Cuetek, but this playing with words, statistics and probability doesn’t work. To me, it looks like a crackpot theory.

twofish-quant

Dec28-09, 08:20 AM

Anytime you mention the word "God" then we are having a theological or philosophical discussion. It's fine to discuss theology or philosophy, but my point is that we are not discussing physics.

The problem with Bayesian arguments is that you have to specify your prior probabilities, and if people with radically different prior probabilities you aren't going to get anywhere.

DevilsAvocado

Dec28-09, 09:01 AM

... The problem with Bayesian arguments is that you have to specify your prior probabilities ...

Agree. It’s not healthy science when you provide the illusion of objectivity – "for neutrality’s sake we start with a 50/50 split between Fm and ~Fm" – when the whole thing is a mathematical setup to promote Cuetek’s most subjective and not verified ideas, omitting crucial facts about the elementary particles (quarks) as the fundamental constituent of matter.

I do think it’s a stimulating 'philosophical idea', but cannot understand why Cuetek has to wrap it in bogus math. It spoils all the fun...

And I do see severe problems in the "hierarchical universe extending in both directions". The quantum-world is not that easy to handle... and it hasn’t anything to do with the tininess of things...

twofish-quant

Dec28-09, 09:01 AM

The two problems here are there is that priors are subjective and also you are using a different P(E|p) at each step. It's an interesting argument which physicists can and often do talk about over drinks at conferences or it might be something you could put into a paragraph at the front of a journal article, but it's nothing that would survive any sort of peer review to be publishable in a physics journal since the argument is not a physics argument. It's extremely weak, and part of the problem is that I don't think OP realizes how weak the argument really is.

twofish-quant

Dec28-09, 09:22 AM

Agree. It’s not healthy science when you provide the illusion of objectivity

Personally, I think that objectivity is overrated. There's a huge amount of subjectivity in physics, and for the most part you deal with it by having people with different subjective views look at the same data. That's why data is so important since data creates a common pool of reality that people can look at. WIthout data, you quickly get into "religious wars" that cannot be resolved.

omitting crucial facts about that the elementary particles (quarks) as the fundamental constituent of matter.

Or omitting the fact that many physicists just don't agree about his characterization of the facts. Now it is possible to deal with this by marking someone as irrational. If someone absolutely insists that the universe is 6000 years old, then they just can't do good cosmology. Period. So you *can* argue that someone's philosophical assumptions place them outside the bounds of science.

Except that's not going to work for me. Whatever philosophical beliefs I have, they certainly are compatible with doing physics and cosmology.

And I do see severe problems in the "hierarchical universe extending in both directions". The quantum-world is not that easy to handle... and it hasn’t anything to do with the tininess of things...

The only problem that I have is that it doesn't fit the data at small scales. As a tool for thinking up new ideas and for solving problems, symmetry principles are wonderful. Sometimes you invoke a symmetry principle and you "get lucky" and you catch the fish. A lot of times, you don't. For example, if you invoke the principle that the universe must look the same through space and time, you end up with the steady-state theory, which is beautiful, elegant, and wrong. If you invoke symmetry to grade-Lie algebras, you end up with supersymmetry, which is also beautiful and elegant and predicts a bizillion particles that people haven't found. Then there is Bode's law.

So I really have no problem with people using symmetry principles as "artistic inspiration." I *do* have big, big problems (and so to most people in physics) with using them as "ground truth."

DevilsAvocado

Dec28-09, 09:35 AM

... I don't think OP realizes how weak the argument really is.

Agree again. On a quick look at the 'mathematical proof', it looks pretty 'serious' (especially to a layman like me).

But if you scrutinize what OP is really saying, the bottomline is:

I have looked at neutrons, atoms, planets, stars, galaxies, cluster and Big Bang. My theory works on these objects, and I know that the Bayesian Theorem (that just calculates probabilities) can help me to promote the idea that these relations also continues at the 'next level' – even if it has absolutely nothing to do with the physical reality.

If the topic was Bayesian spam filtering – the idea would be absolutely great, and would most probably work.

In the real physical world, this means nothing.

DevilsAvocado

Dec28-09, 10:14 AM

Personally, I think that objectivity is overrated.
...
So I really have no problem with people using symmetry principles as "artistic inspiration." I *do* have big, big problems (and so to most people in physics) with using them as "ground truth."

In 1905 the formula E=mc2 was probably looked upon as Einstein's most subjective perspective on the world of matter and energy. Or to quote 'the father of nuclear physics', Ernest Rutherford in 1930:

"Anyone who expects a source of power from the transformation of the atom is talking moonshine."

In 1945 the 'moonshine' got pretty harsh...

Wild and stimulating (philosophical) ideas is fun & cool – if it’s presented as that, and not as the "ground truth".

I love Max Tegmark and his Multiverse.

Cuetek

Dec28-09, 08:02 PM

I'm not interested in making complete and sufficient models of the cosmos. My interest is to create models which summarize the essence of a physical process, which means removing anything that isn't essential to the model.

By not formally assuming the higher probability that the Big Bang is a finite phenomenon in a much larger, materially hierarchical context, you assume the Big Bang is unaffected by larger forces of scale. Your peers talk in terms of the universe being flat or convex when such curvature is almost certainly regional. Your peers talk in terms of the universe's fate from expansion, when such fate is more probably a function of structures you have yet to characterize. This is the more probable disposition. Just like the Copernican model was found to be under the larger influence of the Galactic "island universe" model the Big Bang will be subject to the hierarchical disposition at a greater scale.

I can assume that the universe is infinite, and that will give me good enough numbers for the things that I happen to be interested in.

Infinite is fine, but only in terms of an infinite context within which a hierarchical material disposition is assumed, at least with respect to what to expect in the near term for the next evolution of scale, until the data shows definitively *otherwise.* Which it has not over the entire history of our investigations even though we terminated the hierarchy every time we ever made a new cosmology. It's time to break that bad habit.

No it's not. Heisenberg uncertainty theorem puts a lower limit on structure.

It does no such thing. The only lower limit is one assumed at the plank length and that leaves enormous room for further infinitesimal hierarchy. To think that we have a good idea of what all is happening in the material world at the scale of the quark is overzealous at best.

As far as upper limits, there is no evidence of any hierarchy outside of the observable universe. That's not to say that there isn't. It's just to say that people have looked for it, and we haven't found anything.

No evidence? The entire balance of all the universe we have examined is hierarchical, not homogeneous. All the evidence indicates a very high probability that it continues hierarchically, not homogeneously. Only the narrow focus on a local homogeneity indicates otherwise and the universe is full of local areas of homogeneity that blows the doors off of the galactic level symmetry.

The symmetry you see in the galactic distribution in the visible universe is not anywhere close to say the symmetry at the atomic level of a single drop of water made of trillions of molecules, now put that drop in an ocean. Now THAT's some serious homogeneity.

Oh, sure, you may presume a limited range of homogeneity based on one scale of galactic observations, but not infinite. Even an ocean of trillions upon trillions of molecules of symmetry eventually ends just like every other material structure or phenomenon EVER OBSERVED.

If I can't rationally refute it, then we are having a theological argument rather than a scientific one.

When I say you can't rationally refute the finite rule or plurality principle, it is because they are true for every material phenomenon ever observed, not because they are theological. You can't rationally refute the probability of a coin toss coming up heads at roughly 50% because it's true, not because it's religious.

This is the big problem that I have with your insistence that the universe *has* to work in a certain way. You are making some philosophical assumptions about how the universe works. That's fine. If it gives you a research program, its wonderful, but what I'm telling you is that science doesn't work this way because it *can't* work this way.

I'm not saying it "has" to. I'm saying it is far and away more probable. It's not philosophical either. You are the one being philosophical by insisting that the homogeneous symmetry at one scale is more important than the hierarchical symmetry across all observable scales, even across those which show far more staggeringly enormous ranges of homogeneity than the one you call your "evidence."

It turns out that different people have different philosophical assumptions so if you try to piece together how the universe works that way, you end up with "religious wars." People insisting that their philosophical assumptions are correct and privileged. You have some assumptions about how the world works that I just don't hold, and we try to have this discussion without observational evidence, we are just going to get nowhere.

You are the one being philosophical by your insistence that one scale of evidence is more significant than all scales of evidence. But, I actually sympathize with your position. It is really difficult to realize the assumptions that are being made if everyone has been making them for a long time. Agreement is a very compelling social force. Religions get almost all their enormous social power from just such long held unwarrented agreement.

Cosmologists and physicists do share a minimal set of philosophical assumptions that allows people to communicate, but it has to be a very minimal set. You are stating a set of assumption, and if I say, I just don't accept those, then we are at an impass. Your only response would be that I'm somehow irrational, but I don't *seem* irrational.

I'm content with you feeling that we have come to an impasse.

Now if we did have observations that could resolve this, then it again would be a pointless discussion since we just look at the observations.

The observations are as follows. Every material phenomenon that humans have ever observed have proven to be finite in extent and multiply manifest. All of them. The only phenomenon that has not been proven to be finite or multiply manifest is the expanding profile of the galaxy cluster's which imply the Big Bang. But only because we have yet to devise the instrument that will finally show where it ends. We can't see all of it, so it cannot count as evidence of an exception to the finite rule and plurality principle.

Ask yourself, how do we usually find out that something we thought was the biggest object in the universe, turned out not to be? We find a way to see far enough that we see evidence of another example of what we thought the largest object, and collectively *those* objects form the next thing we call the largest object. See a trend here?

The evidence for presuming a hierarchical universe is substantial, in both historical and scientific terms.

-Cuetek

DevilsAvocado

Dec28-09, 08:31 PM

... To think that we have a good idea of what all is happening in the material world at the scale of the quark is overzealous at best ...

Would you dare to say that to the 9 billion dollar budget guys at LHC Cern?? :biggrin:

Chronos

Dec29-09, 01:18 AM

You need to run bayesian statistics using multiple assumptions to derive boundaries.

twofish-quant

Dec29-09, 09:50 AM

By not formally assuming the higher probability that the Big Bang is a finite phenomenon in a much larger, materially hierarchical context, you assume the Big Bang is unaffected by larger forces of scale.

Absolutely. Then you do calculations, test that assumption against observations, and for the observations we can do, those assumptions seem to work. There are some "smoking gun" things that would lead people to reconsider that assumption, but right now we haven't found them.

It's like assuming a flat earth. For a lot of things, assuming that the earth is flat works pretty well. For some things it works very badly. If you start out by assuming a flat earth, and then things don't make sense, then you change your assumptions. Also some assumptions that people make are clearly false, but useful. The standard models of the big bang assume that the universe is totally homogenous, which is clearly false. I'm staring at a computer screen which is different from the air around it, and the standard models of the cosmology just classify both as "baryonic matter" which are evenly distributed.

Your peers talk in terms of the universe being flat or convex when such curvature is almost certainly regional.

Since we have no data, saying whether something is regional or global is something that we can't say. However one of the cool facts about differential geometry is that it doesn't matter. Any smooth geometry can be approximated by a flat surface. If a flat surface assumption breaks down, then you can approximate things with a simple curvature. Now it's possible that if you look at large enough scales, that will break down, but at that point you are pushing observations past their limits.

Your peers talk in terms of the universe's fate from expansion, when such fate is more probably a function of structures you have yet to characterize. This is the more probable disposition. Just like the Copernican model was found to be under the larger influence of the Galactic "island universe" model the Big Bang will be subject to the hierarchical disposition at a greater scale.

You are making theological statements that are not supported by data. As I mentioned there is nothing particularly wrong with that as long as you realize that you are going past the available data. Ultimately, the problem is that you look at things, and you think "everything supports infinite hierarchy" whereas the astrophysical objects that I study tend not to have "infinite hierarchies." One example is the Kormogarov cascade. It turns out that turbulence is self-similar across a huge range of scales, but the hierarchy cuts out at extremely large scales and extremely small ones. The other thing to point out is that space is mostly nothing. If you look at the sky, you see mostly nothing.

Infinite is fine, but only in terms of an infinite context within which a hierarchical material disposition is assumed, at least with respect to what to expect in the near term for the next evolution of scale, until the data shows definitively *otherwise.*

The problem is that if you try to create this sort of cosmology you end up with something that just doesn't fit the data. Any cosmology that assumes larger structures at this point just ends up being either irrelevant or inconsistent with the data. If you assume a self-similar fractal distribution of galaxies, you end up with galaxy distributions that just don't match what we see.

Which it has not over the entire history of our investigations even though we terminated the hierarchy every time we ever made a new cosmology. It's time to break that bad habit.

Saying "I don't know" is not a bad habit. I think it's a good habit. If you can't see distant galaxies, you can't assume that anything is or is not there.

The only lower limit is one assumed at the plank length and that leaves enormous room for further infinitesimal hierarchy.

No it doesn't. The problem is that if you have something that is localized in space, then it's momentum becomes non-localized, and that means that any hierarchy gets washed out. Unless there is something basically wrong with our understanding of Heisenberg, then there are no new structures between the scales that we can see and planck's length. Once you get to planck's length, then quantum mechanics and GR become inconsistent, so there is new physics at smaller scales.

Also quantum mechanics imposes a lot of information limits. One electron is exactly the same as any other electron which means that there is no internal structure that you can use to mark an electron. The trouble with assuming structure is that you run into the Gibbs paradox. Basically the behavior of gases depends on the statistics of quantum mechanical structure. If there was structure, then gases would behave differently, because you could distribute energy across more states.

To think that we have a good idea of what all is happening in the material world at the scale of the quark is overzealous at best.

Actually, we *do* have a pretty good idea of what happens at the scale of quarks.

No evidence? The entire balance of all the universe we have examined is hierarchical, not homogeneous.

And I look at the universe, and it looks pretty homogenous to me. Unless you can come up some reason why I'm irrational, you have to take that into account.

All the evidence indicates a very high probability that it continues hierarchically, not homogeneously.

I think you aren't familiar with the cosmological evidence. The models that cosmologists use *assume* that the universe is homogenous with things like stars and subway trains being "irrelevant corrections." People make this assumption, because it happens to give answers that fit observations. Now you can assume otherwise, but there is no reason to do so.

Oh, sure, you may presume a limited range of homogeneity based on one scale of galactic observations, but not infinite. Even an ocean of trillions upon trillions of molecules of symmetry eventually ends just like every other material structure or phenomenon EVER OBSERVED.

You are making philosophical arguments and not scientific ones. Also most physicists are aware of some blind spots. If you have something happen that is a one off event with no symmetry, then its something that will likely get ignored by physicists because there's no way of analyzing it.

One reason I look at things differently is that I study supernova. Every supernova that has ever happened is different from any other supernova that has every happened. You classify and analyze, but if you have something that is really, really different, it's going to get ignored.

When I say you can't rationally refute the finite rule or plurality principle, it is because they are true for every material phenomenon ever observed, not because they are theological.

And I say it's not true. Supernova 1987A was different from every other supernova that happened. The electric and gravitational field that an electron produces is not limited by space. Also the term "material phenomenon" is a interesting dodge, since it's not clear to me what is material and what isn't. Is light material? What about energy? What about money?

Look, you are on a bulletin board with people that have a lot of experience looking at astrophysical phenomenon, and no one other than you seems to think that the finite rule or the plurality principle is something that is an intrinsic characteristic of the universe. Unless, you want to argue that we are all irrational, then this means that those ideas are at least debatable.

You can't rationally refute the probability of a coin toss coming up heads at roughly 50% because it's true, not because it's religious.

I flip the coin. I've seen coins that *don't* come up heads 50% of the time.

I'm not saying it "has" to. I'm saying it is far and away more probable.

And I'm saying that it's a bad idea to assign probabilities to things that you know nothing about, whether it's the big bang or the odds of a failure of a major investment bank. Part of the reason this matters is that it impacts my day job. I'm very, very skeptical of assigning a single number to a one off event, since this really killed people when Lehman Brothers happened.

So if you can't assign a probability to a one time event, then how do you manage it? Not sure, but I get paid to think about stuff like that. The problem is when you say "this is more probable" what do you mean? The answer that I've come up with is that with one time events, "probability" is a measure of psychological certainty, which may have nothing to do with the physical situation or likelihood of the event. That definition of probability very, very nicely models things like credit default swaps (i.e. the probability is how likely the market thinks that Lehman will default which is a psychological measure that may have nothing to do with the likelihood that Lehman will actually default).

But if you use that definition of probability, then it tells you nothing about the real world (which is great since if there is a difference between psychological probability and physical probability, you can make tons of money).

It's not philosophical either. You are the one being philosophical by insisting that the homogeneous symmetry at one scale is more important than the hierarchical symmetry across all observable scales, even across those which show far more staggeringly enormous ranges of homogeneity than the one you call your "evidence."

One problem here is that you really can't avoid being philosophical, because ultimately you have to come up with some basic rules for evaluating evidence. What is truth? How do you evaluate data?

Something that should be very obvious by now is that the rules you are using to establish truth are very, very different from the ones that most physicists are using, which is the point that I'm trying to make to you.

But, I actually sympathize with your position. It is really difficult to realize the assumptions that are being made if everyone has been making them for a long time. Agreement is a very compelling social force. Religions get almost all their enormous social power from just such long held unwarrented agreement.

You have to make some assumptions about the world, but the thing that physicists (and for that matter Catholic theologians) try to do is to be explicit about those assumptions. What I'm trying to tell you is that the assumptions you are making and the arguments that you are trying to establish, simply will not hold water among most cosmologists.

It's useful to talk to people with radically different assumptions about how the world works, because then you figure out how you are seeing the world and why. Something that should be obvious to you is that if you are trying to create a moral or ethical code around science, you are likely to get nowhere. Science is all about doubt, and getting up in front of people and saying "I just don't know."

The observations are as follows. Every material phenomenon that humans have ever observed have proven to be finite in extent and multiply manifest. All of them.

You keep saying that and I say that's not true.

The only phenomenon that has not been proven to be finite or multiply manifest is the expanding profile of the galaxy cluster's which imply the Big Bang.

Supernova 1987A, the collapse of Lehman Brothers, the electric field of the electron. Electric fields are not finite. Supernova 1987A and the collapse of Lehman Brothers are not multiply manifest. There are things that are finite and multiple manifest, but as far as "all phenomenon" that's not true, and that's not even close. Most of the things I study *aren't* multiply manifest or finite, and I think that's true for physicists in general, which is why no one seems to be agreeing with you.

Ask yourself, how do we usually find out that something we thought was the biggest object in the universe, turned out not to be? We find a way to see far enough that we see evidence of another example of what we thought the largest object, and collectively *those* objects form the next thing we call the largest object. See a trend here?

House prices between 2001 and 2005 were going up radically. See a trend here?

twofish-quant

Dec29-09, 10:42 AM

If you want to explain my philosophy of truth. Truth=survival. If you jump off a 100 story building, you aren't going to leave too many descendants. If you jump off a five story building, you break some bones and learn never to do that again. Over time (i.e. hundreds of millions of years), organisms become programmed to look for truth.

This matters with modeling, because in the last year the world just took an economic jump off a five story building, and so people have concluded that it's not a good idea to do that again. A lot of the problems involved taking models that were perfectly good for one domain and applying it where there was no data to support them. People took models of collaterialized default obligations that work beautifully with junk bonds and applied them to mortgage securities, which was a really really bad idea. (The basic problem is that when say an electronics factory goes bust, then the odds are that the concrete factory next to it still works. If one subprime mortgage goes bad, then chances are that all of the subprime mortgages in the world are also going bad at the same time.)

A lot of what I do involves thinking about probability and correlations, and there are some arguments that you use that get you punched in the gut by reality and some arguments that don't, and the probability arguments that the OP are using are a bit too much like the probability arguments that people used to justify a lot of the CDO non-sense. Certainty will get you killed in the markets. If you can model interest rates with 70% certainty, you are going to be a billionaire. The thing is that most people can't and the one's that seem to usually just got lucky.

It's actually curious but the mathematics of finance resemble a lot the mathematics of general relativity. There is a lot of modelling surfaces and curvative.

Cuetek

Dec29-09, 10:51 AM

Agree again. On a quick look at the 'mathematical proof', it looks pretty 'serious' (especially to a layman like me).

As a layman maybe you should stay away from the math. Bayes theorem is a probability theorem. Probability theorems by definition cannot be proof of anything. Hope this helps.

But if you scrutinize what OP is really saying, the bottomline is:

I have looked at neutrons, atoms, planets, stars, galaxies, cluster and Big Bang. My theory works on these objects, and I know that the Bayesian Theorem (that just calculates probabilities) can help me to promote the idea that these relations also continues at the 'next level' – even if it has absolutely nothing to do with the physical reality.

Good lord, listen to yourself. You are saying that the rest of the examined universe has "absolutely nothing to do" with predicting the nature of the part of it that lies just beyond our view. Good luck with that philosophy.

-Cuetek

Cuetek

Dec29-09, 11:45 AM

[I]Absolutely. Then you do calculations, test that assumption against observations, and for the observations we can do, those assumptions seem to work.

I have. It's a high probability based on both the widely extant structure of the universe and the history of our discovery of it.

Since we have no data, saying whether something is regional or global is something that we can't say.

We have plenty of data. I use that data (the visible universe) to predict that we should look not for homogeneity but for differentiation (a dipole in the CMB for example).

You are making theological statements that are not supported by data.

Wrong. We are both projecting the visible data beyond our view. You with the cosmological principle and me with the hierachical principal. Mine is more extensive than yours is all.

As I mentioned there is nothing particularly wrong with that as long as you realize that you are going past the available data.

The cosmological principle goes past it as well. Apples and apples.

Ultimately, the problem is that you look at things, and you think "everything supports infinite hierarchy" whereas the astrophysical objects that I study tend not to have "infinite hierarchies."

Wrong. I only say that we should presume hierarchical diversity instead of homogeneity in the neear term. The new data will tell the tale (probably just like it has in the past showing us more and more of the hierarchy).

The problem is that if you try to create this sort of cosmology you end up with something that just doesn't fit the data. Any cosmology that assumes larger structures at this point just ends up being either irrelevant or inconsistent with the data. If you assume a self-similar fractal distribution of galaxies, you end up with galaxy distributions that just don't match what we see.

The homogeneity has only been measuered (WMAP) to a fine enough degree to assume a homogeneity for about 5000 times the diameter of the particle horizon (14 bil Lt Yr.) Anything beyond that, the distribution could begin to change up or down and we'd have no way of knowing.

Saying "I don't know" is not a bad habit. I think it's a good habit. If you can't see distant galaxies, you can't assume that anything is or is not there.

But the cosmological principle doesn't say that does it?

No it doesn't. The problem is that if you have something that is localized in space, then it's momentum becomes non-localized, and that means that any hierarchy gets washed out. Unless there is something basically wrong with our understanding of Heisenberg, then there are no new structures between the scales that we can see and planck's length. Once you get to planck's length, then quantum mechanics and GR become inconsistent, so there is new physics at smaller scales.

Also quantum mechanics imposes a lot of information limits. One electron is exactly the same as any other electron which means that there is no internal structure that you can use to mark an electron. The trouble with assuming structure is that you run into the Gibbs paradox. Basically the behavior of gases depends on the statistics of quantum mechanical structure. If there was structure, then gases would behave differently, because you could distribute energy across more states.

Translating what is giong on at infinitesimal levels seems to be very enigmatic. Nonetheless, quarks make nutrons make atoms make molecules, etc etc. hierarchy.

Actually, we *do* have a pretty good idea of what happens at the scale of quarks.

Sure we do.

(schnype) Ran out of time. Got to go to work.

House prices between 2001 and 2005 were going up radically. See a trend here?

Yes the trend went up. But the larger trend shows that house prices went up and down a lot. That's why I use all the scales of the universe rather than just one. See the trend here?

-Cuetek

DevilsAvocado

Dec29-09, 03:05 PM

You need to run bayesian statistics using multiple assumptions to derive boundaries.

Agree. And most of all – you need not to exclude things that doesn’t fit the 'predefined' theory, like quarks.

twofish-quant

Dec29-09, 03:55 PM

I have. It's a high probability based on both the widely extant structure of the universe and the history of our discovery of it.

However the fact that your arguments and probabilities seem to be unconvincing to people that work in cosmology and astrophysics should at least give you some cause for concern. In particular, unless you want to conclude that most astrophysicists are irrational, you do have to admit that rational people can at least debate and disagree with the principles that you suggest.

They may be self-evidently true to you, but they aren't to me, and they don't seem to be self-evidently true to most of the people in the field that have commented on this thread.

Part of the reason I don't want to go past the data, is that we are already making a ton of crazy assumptions and suppositions in our cosmological models of the universe. There's no point that I can see in adding anything that the data doesn't absolutely force you to make.

Wrong. We are both projecting the visible data beyond our view. You with the cosmological principle and me with the hierachical principal. Mine is more extensive than yours is all.

No I'm not. I'm saying that we can't make many statements about the ultra large scale structure of the universe. The assumption of a homogenous universe is something like a spherical cow or a flat earth. It's a guess that seems to give the right numbers, but it may be totally wrong for the problems I'm interested in, and it's obviously wrong for some of the one's that I'm not. The standard big bang model assumes that the earth and sun do not exist, and that the whole universe is filled with a homogenous gas.

It's a workable model. Whether it's the ultimate truth or not is anyone's guess, but I'm a physicist. I'm in the numerical modeling business and not the ultimate truth business.

The big difference is that I'm at least willing to consider that the cosmological principle might will be wrong, and it's good for nothing more than "artistic inspiration." The other difference is that I can calculate helium and deuterium abundances, and you can't.

Wrong. I only say that we should presume hierarchical diversity instead of homogeneity in the near term.

Why? It just makes it more difficult to calculate deuterium abundances and galaxy clustering coefficients or think about galaxy formation.

The homogeneity has only been measuered (WMAP) to a fine enough degree to assume a homogeneity for about 5000 times the diameter of the particle horizon (14 bil Lt Yr.) Anything beyond that, the distribution could begin to change up or down and we'd have no way of knowing.

The point of a theorist is to come with observational tests. If you are convinced that the universe is hierarchical, then this is great for "artistic inspiration". Come up with some observational signature for that sort of model. There's a whole industry of people trying to do just that. It's a hard problem.

Suppose the density of the universe suddenly went up or down 6000 times the diameter of the particle horizon. What happens? Is it something we can detect? It is something that we can lobby Congress for to build some instrument that we can detect? What sort of statistics are we looking for?

But the cosmological principle doesn't say that does it?

What I'm trying to get across is what a "principle" means in physics. It's artistic inspiration. Invoking a principle is a start of a conversation and not a resolution to one. The reason for this is that people have invoked principles that turned out to be wrong. Two examples of this are the perfect cosmological principle in the steady-state universe or the static universe principle. You are not going to win an argument in physics by invoking any sort of principle, because so many of them have ended up being just wrong.

DevilsAvocado

Dec29-09, 04:06 PM

As a layman maybe you should stay away from the math. Bayes theorem is a probability theorem. Probability theorems by definition cannot be proof of anything. Hope this helps.

Thanks for the advice and the very friendly attitude! Though I have not yet decided if I will accept your mentorship. It depends on if you can prove your own mathematical status, by explaining your choice of Boolean values in your own "numerical justification" of this very weird 'theory':

p(E|Fm) = 1 (true)
p(E|~Fm) = 0.5 ('half-true' !?)

This is completely nutty and I haven’t decided if you do this on purpose to fit the 'theory' – or you just don’t know what you are doing, and don’t understand the rules of Bayes' Theorem.

The Boolean negation of true is not 'half-true', it’s false (0) and as a 'mathematical grand genius' you should know that.

If you avoid answering this mathematical question, as you did with #50 (http://www.physicsforums.com/showpost.php?p=2507923&postcount=50), I can only come to the conclusion that you are even more a layman than me, and then naturally the 'mentorship' is rejected. Sorry.

DevilsAvocado

Dec29-09, 06:59 PM

As a layman maybe you should stay away from the math. Bayes theorem is a probability theorem. Probability theorems by definition cannot be proof of anything. Hope this helps.

Good lord, listen to yourself. You are saying that the rest of the examined universe has "absolutely nothing to do" with predicting the nature of the part of it that lies just beyond our view. Good luck with that philosophy.

-Cuetek

Maybe it’s a good idea you start listen to yourself. This is getting pretty close to the physics of Fawlty Towers.

Since when is science, physics and cosmology the art of statistically "predicting the nature"!? Running Bayes' Theorem to find a law of nature!? What would the world look like if Einstein worked for years on the solution for something like p(E|mc2)...!? OMG

The key to this is "the part of it that lies just beyond our view". When do you expect to get any data from that just beyond our view? Any measurements? Anything, besides homemade bayesian assumptions...?

This is a play with words and half-rotten math.

Let’s skip the math, and bring it down to (my) hillbilly-level, so we all can join the discussion. Now what you are saying is basically this:

1) A foreigner without maps visits Las Vegas for the first time.
2) He gets bored, and decides to visit Great Basin National Park, and rents a car.
3) After driving 40 km on the very straight U.S. Route 93 highway in Nevada, he gets extremely tired.
http://upload.wikimedia.org/wikipedia/commons/thumb/4/45/US_93_2.jpg/500px-US_93_2.jpg
4) He’s a player and knows how to calculate probabilities. He runs Bayes' Theorem in his head and finds that the odds for the highway to continue like this are very good, 99.6%.
5) He activates the cruise control and falls asleep, feeling safe.
6) 10 km later he crashes at Pahranagat Valley.

Now, when we react on this behavior and don’t want to join the 'bayesian car', you act like a clown and don’t want to hear what we are saying...

"Probability theorems by definition *cannot* be proof of anything."

I absolutely agree.

Cuetek

Dec31-09, 07:27 AM

However the fact that your arguments and probabilities seem to be unconvincing to people that work in cosmology and astrophysics should at least give you some cause for concern. In particular, unless you want to conclude that most astrophysicists are irrational, you do have to admit that rational people can at least debate and disagree with the principles that you suggest.

Well, as arrogant as it seems, I am saying that most astrophysicists are irrational on this one point. I'm saying that this irrationality is due to adherance to an old concept that is imminently understandable, but one that is by it nature is impossible to prove or disprove. I am saying that the more probable presumption is that the hierarchy of the universe will prevail. I am not saying that the cosmological principle is worthless. I am saying that it is only locally relavant.

They may be self-evidently true to you, but they aren't to me, and they don't seem to be self-evidently true to most of the people in the field that have commented on this thread.

Part of the reason I don't want to go past the data, is that we are already making a ton of crazy assumptions and suppositions in our cosmological models of the universe. There's no point that I can see in adding anything that the data doesn't absolutely force you to make.

I totally agree with the "we've already gone too far. But I think such trends are due to lack of data and prior insufficient assumptions that have led to us relying to completely on highly developed math models and not data. Many of those models are based on assumptions like the cosmological principle. It's not that scientists say that they believe the cosmological principle is true, but their research is predominantly based on how the cosmos would behave if it were true. Going back to the data, there is more data that says somewhere out there we will find that the cosmological principle will not longer be useful. If were are going to go too far, we should look at the widest possible interpretation of the data.

Bayes theorem is widely used in cosmology. The cosmological principle is, in fact, Bayesian. You look at the homogenety and imagine it goes much farther. But all Bayesian projections are limit at both ends of the scale. So too, in all probqability, will the hierarchical assumption be found wanting at some scale. But at our current point in history, it is more useful to guide our search for the nature of the universe beyond our instrumentation. More and more we will need to make wider assumptions as the data gets harder and harder to come by.

No I'm not. I'm saying that we can't make many statements about the ultra large scale structure of the universe. The assumption of a homogenous universe is something like a spherical cow or a flat earth. It's a guess that seems to give the right numbers, but it may be totally wrong for the problems I'm interested in, and it's obviously wrong for some of the one's that I'm not. The standard big bang model assumes that the earth and sun do not exist, and that the whole universe is filled with a homogenous gas.

It's a workable model. Whether it's the ultimate truth or not is anyone's guess, but I'm a physicist. I'm in the numerical modeling business and not the ultimate truth business.

You are going to make an assumption one way or the other. Your models are fine, but should be formally limited to some 5000 times the particle horizon. The universe is strange. Think about the boson of gravity. While some bosons are bigger than others. No one in their right would think that a boson could be really big. But if the hierarchical principle is true, the forces that govern the structures at meta scales would have to be bigger and bigger as well.

The weak nuclear is very short range. The strong nuclear acts across a larger range. The electrical force, while theoretically infinite, acts mostly across molecular distances and some larger scales like lightning and even some theoretical cosmic scales. Gravity is clearly the farthest ranging, but near indetectable at molecular scales. So it would be prudent to imaging newer forces emerging at meta scales "above" the vis universe scale.

The boson for those meta scale forces might be huge by quantum standards. What if the graviton was the black hole? What if all matter derived gravity from by induction from being in the grip of a black hole field. If the big bang were a massive black hole most of the matter might still be on one side of us and we may be in an enroumous meta scale gravitational field. Perhaps it is ultimately that field alone which contributes the gravity ehibited by matter in it's grip.

I'm not saying this is how it is, just how a hierarchy might behave at larger scales. If the hierarchy prevails there will be larger forces of scale to organize the structures with additional meta scale explanations. Anything that moves us into such mindsets would be valuable if the hierarcy is true. And I feel the data we do have suggests the hierarchy is far more likely to prevail than is the homogeneity. Call it philosophical if you like, but it's a data-based philosophy and the theorist is going to have to make one or the other assumption. Assuming the CP is limited to 5000+ x the particle horizon makes both assumptions possible. (Actually, make it 50,000+ times the particle horizon, because it's absolutely homogenous out to 5000, so it will most probably remain roughly homogeneous much farther out.)

The big difference is that I'm at least willing to consider that the cosmological principle might will be wrong, and it's good for nothing more than "artistic inspiration." The other difference is that I can calculate helium and deuterium abundances, and you can't.

The CP is perfectly fine for local modeling, like curvature of the regions, just not for modeling the curvature of the "universe".

Why? It just makes it more difficult to calculate deuterium abundances and galaxy clustering coefficients or think about galaxy formation.

The CP is fine for local (5000+ times the particle horizon) calculation. The hierarchical principle should be used with hypothesizing beyond that limit.

The point of a theorist is to come with observational tests. If you are convinced that the universe is hierarchical, then this is great for "artistic inspiration". Come up with some observational signature for that sort of model. There's a whole industry of people trying to do just that. It's a hard problem.

The data will tell the tale sooner later no matter what. I'm just saying what the tale will more probably be in the long run. Such presumption will accelerate the process over waiting for the data to accurately limit the prior presumption.

Suppose the density of the universe suddenly went up or down 6000 times the diameter of the particle horizon. What happens? Is it something we can detect? It is something that we can lobby Congress for to build some instrument that we can detect? What sort of statistics are we looking for?

I've found numerous papers supporting the CP as fact (homogeneity inevitable) and only one paper defining it's limits (homogeneity currently reliable only out to 5000 x particle horizon). As I've suggested looking for a faint dipole in the CMB radiation is the first thing I'd do, or look for one side of the sky to have slightly larger voids etc. But it's what the expectation of inhomogeneity does to the thoerist's mindset that would have the most impact on research.

What I'm trying to get across is what a "principle" means in physics. It's artistic inspiration. Invoking a principle is a start of a conversation and not a resolution to one. The reason for this is that people have invoked principles that turned out to be wrong. Two examples of this are the perfect cosmological principle in the steady-state universe or the static universe principle. You are not going to win an argument in physics by invoking any sort of principle, because so many of them have ended up being just wrong.

I am gratified by the way you describe it above. You didn't sound so equivocal when we first started discussing this. My own grasp as to how to talk about it has improved as well. Peace. -Mike Harmon

Cuetek

Dec31-09, 08:01 AM

p(E|Fm) = 1 (true)
p(E|~Fm) = 0.5 ('half-true' !?)

This is completely nutty and I haven’t decided if you do this on purpose to fit the 'theory' – or you just don’t know what you are doing, and don’t understand the rules of Bayes' Theorem.

The Boolean negation of true is not 'half-true', it’s false (0) and as a 'mathematical grand genius' you should know that.

In Bayes theorem the variables you mention above are necessarily probabilities, not Boolean variables. The allowable values of these varables range inclusively between 0 and 1. If you like you can fudge them all around however you like to make the results come out however you see fit. That's the subjective nature of Bayes probability theorem. The assignment of the variables is the whole deal. I will be glad to debate why I chose the values I did, but you need to bone up on probability theorms first.

twofish-quant

Dec31-09, 10:17 AM

I am saying that the more probable presumption is that the hierarchy of the universe will prevail. I am not saying that the cosmological principle is worthless. I am saying that it is only locally relavant.

What I'm saying is you are basically misinterpreting how astrophysicists think.

1) The cosmological principle is not some sort of dogma, but a guess and a rough rule that allows people to make calculations
2) Without data, it's impossible to make firm statements about whether it is globally true or not. It *is* possible with the current data to say that assuming the cosmological principle allows us to make predictions about the universe that seem to accord with observations.

But I think such trends are due to lack of data and prior insufficient assumptions that have led to us relying to completely on highly developed math models and not data. Many of those models are based on assumptions like the cosmological principle.

Right, because you can then take the model and make predictions about the universe. The point that I'm making is that just because an astrophysicist makes an assumption in a model, doesn't mean that they think that assumption is true. If you want to *disprove* the cosmological principle, then what you need to do is to create a model that *assumes* that the principle is true, show that that model inherently creates results that don't match observations.

The highly developed math is because it is a really, really painful and difficult thing to go from theory to observational test. Suppose you were to assert that the density of the universe falls off very strongly an 2x the observational horizon. Going from that assumption to COBE power spectrum measurements is extremely painful.

It's not that scientists say that they believe the cosmological principle is true, but their research is predominantly based on how the cosmos would behave if it were true.

Which is exactly the approach you need to take if you doubt that it is true. Let's assume that the cosmological principle is false. You predict X. You see X. That tells you absolutely nothing. So let's assume that the cosmological principle is true. You predict X. You see not-X. At this point the cosmological principle is proven wrong.

If you were seeing increases in the power spectrum at higher and higher scales, then we'd have a big problem. If there were systematic differences in the CMB in different parts of the sky, we'd have a big problem. You *assume* something is true, so that you have some idea what to look for in order to prove that it is false.

Your models are fine, but should be formally limited to some 5000 times the particle horizon.

Why? I make statements about what the world looks like 10^6 times the particle horizon and that see if it makes any difference.

The CP is fine for local (5000+ times the particle horizon) calculation. The hierarchical principle should be used with hypothesizing beyond that limit.

Why? What you really need to do is to make a million different hypothesis and then throw them against the wall to see what sticks.

As I've suggested looking for a faint dipole in the CMB radiation is the first thing I'd do, or look for one side of the sky to have slightly larger voids etc.

Which is what people have done.

But it's what the expectation of inhomogeneity does to the thoerist's mindset that would have the most impact on research.

What I'm saying is that I think you are misinterpreting what theorists are doing. Most papers in cosmology have nothing to do with the ultra-large scale structure of the universe, so there people assume the cosmological principle because the math is simpler, and if what you are doing isn't impacted by the ultra-large scale structure of the universe, you want to assume spherical cows and flat earths. Most papers in astrophysics outside of very narrow fields use Newtonian gravity because GR is just a pain to calculate.

If you are *expecting inhomogenity* then you assume homogenity. At that point you write papers invoking the cosmological principle, figure out the implications, and the look for deviations from observations. The problem with create models of inhomogenity is that once you've done that, you've restricted yourself to a particular model, which causes problems if both the CP and the inhomogenous model is wrong.

If you want to kill the CP, you need to absolutely avoid presenting an alternative model, and you need to focus on writing papers that assume the CP is true.

Also you be careful not to extrapolate someone's beliefs from the papers that they write. I don't know whether the CP is correct or not, but I'd certainly be depressed if it where.

Cuetek

Dec31-09, 01:38 PM

What I'm saying is you are basically misinterpreting how astrophysicists think.

1) The cosmological principle is not some sort of dogma, but a guess and a rough rule that allows people to make calculations
2) Without data, it's impossible to make firm statements about whether it is globally true or not. It *is* possible with the current data to say that assuming the cosmological principle allows us to make predictions about the universe that seem to accord with observations.

You are being very circumspect with the above characterization. However, when I hear cosmologist being interviewed, they say without qualification things like "if the universe is convext it will expand forever, if it is flat it will reach a steady state (or something like that) and if it's concave it will recollapse." These are reflexive predictions typical yet presumptuous beyond your above characterization. I say the reflex runs deeper than you think and that it is counter productive to a more realistic view of the proper extent and configuration of the universe.

It's no big deal. The data will tell the tale. But it may take longer.

Right, because you can then take the model and make predictions about the universe. The point that I'm making is that just because an astrophysicist makes an assumption in a model, doesn't mean that they think that assumption is true. If you want to *disprove* the cosmological principle, then what you need to do is to create a model that *assumes* that the principle is true, show that that model inherently creates results that don't match observations.

In essense, that's what I've done. I show a statistical probability that the universe will not conform to the cosmological principle and I make a prediction that the CMB will show evidence of inhomogeneity.

The highly developed math is because it is a really, really painful and difficult thing to go from theory to observational test. Suppose you were to assert that the density of the universe falls off very strongly an 2x the observational horizon. Going from that assumption to COBE power spectrum measurements is extremely painful.

Which is exactly the approach you need to take if you doubt that it is true. Let's assume that the cosmological principle is false. You predict X. You see X. That tells you absolutely nothing. So let's assume that the cosmological principle is true. You predict X. You see not-X. At this point the cosmological principle is proven wrong.

If you were seeing increases in the power spectrum at higher and higher scales, then we'd have a big problem. If there were systematic differences in the CMB in different parts of the sky, we'd have a big problem. You *assume* something is true, so that you have some idea what to look for in order to prove that it is false.

I'm assuming that the universe is more likely hierarchical than homogeous. I predict very slight variations on opposite sides of the sky due to my prediction that they big bang is finite in extent causing a slightly higher CMB temp and material density in the direction of it's "center". That we don't have the data yet is not being debated. My predictions, like many, will have to wait to be confirmed or refuted.

Why? I make statements about what the world looks like 10^6 times the particle horizon and that see if it makes any difference.

It will make no difference to your idealized model, But the farther away you make your characterizations the less coroborable they are. I probably don't really see what you are saying here.

Why? What you really need to do is to make a million different hypothesis and then throw them against the wall to see what sticks.

Well, Ive made one, we'll see if it sticks. May take a while.

Which is what people have done.

I predict they will find what they are looking for. But only a few people are trying very hard to find something contratry to the CP. Most people are trying to confirm it.

What I'm saying is that I think you are misinterpreting what theorists are doing. Most papers in cosmology have nothing to do with the ultra-large scale structure of the universe, so there people assume the cosmological principle because the math is simpler, and if what you are doing isn't impacted by the ultra-large scale structure of the universe, you want to assume spherical cows and flat earths. Most papers in astrophysics outside of very narrow fields use Newtonian gravity because GR is just a pain to calculate.

If you are *expecting inhomogenity* then you assume homogenity. At that point you write papers invoking the cosmological principle, figure out the implications, and the look for deviations from observations. The problem with create models of inhomogenity is that once you've done that, you've restricted yourself to a particular model, which causes problems if both the CP and the inhomogenous model is wrong.

If you want to kill the CP, you need to absolutely avoid presenting an alternative model, and you need to focus on writing papers that assume the CP is true.

Also you be careful not to extrapolate someone's beliefs from the papers that they write. I don't know whether the CP is correct or not, but I'd certainly be depressed if it where.

I don't think I am overestimating how strongly most cosmologists believe that it is perfectly plausible that the universe is intirely homogeneous at the largest visible scales. I know that all good scientists will say that they don't know, but the what they look for in their work is a better indication of what they believe and that is confirmation of the CP for the most part.

I say that there is a strong tendency for all of us to prefer a presumption that makes the whole universe comprehensible under the current data set and assumptions. By making whatever is out there conform to the same disposition as what we can see of it, we have inadvertently limited our conception of the universe in a way that I feel is counter productive to discovering the wider truth.

It'm not refuting anything. I'm only trying to reveal the conceptual downside of CP. It's not an affront to science, but it can seem like an affont to our abilibty to ever know the whole truth. Some people find that more depressing than you find the ultimate implication of the CP.

twofish-quant

Dec31-09, 02:45 PM

However, when I hear cosmologist being interviewed, they say without qualification things like "if the universe is convext it will expand forever, if it is flat it will reach a steady state (or something like that) and if it's concave it will recollapse." These are reflexive predictions typical yet presumptuous beyond your above characterization.

Those statements have nothing to do with the cosmological principle. If it's open, then it will expand forever. If it's closed, it will recollapse. If the universe isn't homogenous, then different parts of it will do different things. It's quite possible for a part of the universe to collapse while the rest expands. It's called a black hole.

I show a statistical probability that the universe will not conform to the cosmological principle and I make a prediction that the CMB will show evidence of inhomogeneity.

But you haven't mentioned what that inhomogeneity will look like. Yes if half the sky is black and the other half is white, then yes its homogenous. But it's also possible for the universe to be wildly inhomogenous, but that fact may not be obvious. In order to find inhomogenity you have to first assume homogenity, make a lot of predictions and then find deviations from that.

I'm assuming that the universe is more likely hierarchical than homogeous.

That's a problem. There are thousands of ways that the CP could be wrong, and if you propose an alternative model, you miss the main point of looking thinking about the CP.

I predict very slight variations on opposite sides of the sky due to my predction that they big bang is finite in extent causing a slightly higher CMB temp and material density in the direction of it's "center". That we don't have the data yet is not being debated.

Actually we do have lots of data, and other than dipoles, there is no measurable difference in CMB temp or material density. You could say that the amount is too small to currently see, but even with the data we have, we can exclude a lot.

And you could be missing the point. It's not hard to come up with inhomogenous models or hierarchical models which *don't* have differences in CMB and material density. We could by share chance be in the middle of the explosion. There could be some big dust cloud that is hiding things. The universe could be inhomogenous at scales much larger than the particle horizon.

My predictions, like many, will have to wait to be confirmed or refuted.

The whole point of a theorist is to come up with predictions that can be confirmed or refuted within a reasonable amount of time. If you can't think of one, then think harder. What detection levels will kill your model? The problem with things is that saying that "there is some hierarchy somewhere" isn't an interesting or useful statement. If we can't see it, you can always push things off to the future, and without perfect knowledge, which we we never have, you can't firm statements.

Now if you have a model that predicts a dropoff in density at 3x the particle horizon then it's dead already. If you have a model that predicts a dropoff in density at 8000x the particle horizon then it's interesting since we'll know within a decade if that's right or not. If you are predicting 10**6x particle horizon, then it's pretty useless.

I remember around 1995, when COBE first started sending out results, when there was a bit of excitement because it was showing that the CMB was smooth. Too smooth. There was a conversation in which someone mentioned that if they don't see any anisotropies in the next two or three months, then we are going to have some serious, serious explaining. But COBE finally saw anisotropies.... Bummer.

Well, Ive made one, we'll see if it sticks. May take a while.

Anything you can to so that you learn something in the next 5 to 10 years? Also suppose we do CMB measurements and find no global deviations to a factor of 10^-5, will that convince you that you are wrong? What about 10^-6, 10^-10, 10^-100000?

I predict they will find what they are looking for. But only a few people are trying very hard to find something contratry to the CP. Most people are trying to confirm it.

What about going in without too many expectations about what you are going to find?

The problem with the cosmological principle is that it can't be confirmed as a universal fact. The only thing that you can say is that the cosmological principle is correct to some limit.

I don't think I am overestimating how strongly most cosmologists believe that it is perfectly plausible that the universe is intirely homogeneous at the largest visible scales.

There is an observations fact that as far as we can tell the universe is homogenous at the largest scales that we can observe, and there aren't any observations that would suggest any deviation from global homogenity. That's just fact. It's *plausible* that the universe is globally homogenous. But there are lots of things that are plausible that aren't true.

I know that all good scientists will say that they don't know, but the what they look for in their work is a better indication of what they believe and that is confirmation of the CP for the most part.

No. You can't confirm the cosmological principle. It's impossible for the reasons that I mentioned above. The only thing that you can do is to refute it. So you work out that the CP says that some number ought to be 4. You do the measurement. If its 3.98, then you work on something else. If its 10, then it's interesting.

The other thing is that astrophysicists have often seen wild things that they didn't expect. No one in 1998 expected the universe to be accelerating.

I say that there is a strong tendency for all of us to prefer a presumption that makes the whole universe comprehensible under the current data set and assumptions.

None of the physicists I know have this point of view. If we understood everything, it would be really, really depressing. There wouldn't be any point in doing theory or observations if we had any clue what was really going on.

It'm not refuting anything.

You should be. The whole point of science is to come up with ideas, and then bash them to pieces.

It's not an affront to science, but it can seem like an affont to our abilibty to ever know the whole truth.

Anyone that wants to learn the WHOLE TRUTH about the universe should stay out of astrophysics.

DevilsAvocado

Jan1-10, 12:38 PM

It'm not refuting anything.

You should be. The whole point of science is to come up with ideas, and then bash them to pieces.

It's not an affront to science, but it can seem like an affont to our abilibty to ever know the whole truth.

Anyone that wants to learn the WHOLE TRUTH about the universe should stay out of astrophysics.

Sorry, can’t help it – but this make me laugh! :rofl:

DevilsAvocado

Jan4-10, 09:55 AM

In Bayes theorem the variables you mention above are necessarily probabilities, not Boolean variables. The allowable values of these varables range inclusively between 0 and 1. If you like you can fudge them all around however you like to make the results come out however you see fit. That's the subjective nature of Bayes probability theorem. The assignment of the variables is the whole deal. I will be glad to debate why I chose the values I did, but you need to bone up on probability theorms first.

On this point, you are right and I’m dead wrong. I apologize and the laughs now are free and all on me. :redface:

(Silly :blushing:) Attempt to save my intellectual a*s.

I thought of this as:
p(E|Fm) = 1
Not(p(E|Fm)) = 0

This is clearly wrong. In this case it is correct though:
p(Fm) = 1
p(~Fm) = 0

or

p(Fm) = 1
Not(p(Fm)) = 0

Since we in this case only have 1 (or 100%) to play with... or what ever...

But, I still say you are cheating. In your paper you write:
On the left hand side of the full equation, the term p(H|E) stands for the probability of hypothesis H being true given the existence of evidence E.

And you do the following assignments:
Probability ( A object being finite, multiply manifest constituent of a larger object | Current object is collectively assembled from smaller objects )

Objection: Where is the evidence proving that if an object is "collectively assembled from smaller objects", it must also be finite??

In your paper you write:
Structural Analysis
Taking the material structure of the universe from quarks to galactic clusters as the evidentiary field we can calculate the probability of both rules of discovery being true for Big Bang as follows:
...
So we take one of the smallest object we can currently detect (the neutron) that we know contains yet smaller objects (quarks)
...

Objection: This is obvious cheating. In your analysis you claim to go all the way from quarks to clusters to prove your theory. But when the calculation starts you skip the quark (since it doesn’t fit your theory) and jump ahead to the neutron!?

When we protests about this, you make up your own world.
To think that we have a good idea of what all is happening in the material world at the scale of the quark is overzealous at best.

Thus dismissing a great part of the scientific establishment and billion dollar budgets:
http://upload.wikimedia.org/wikipedia/commons/thumb/0/00/Standard_Model_of_Elementary_Particles.svg/400px-Standard_Model_of_Elementary_Particles.svg.png
http://i49.tinypic.com/2q9e3ae.jpg

It becomes ridicules when you at the same time claim to found the proof that "the Big Bang phenomenon is constituent to a larger, yet similar finite, structure", and yet admit:
Probability theorems by definition cannot be proof of anything.

Where is your proof??

How many billions of dollars are spent on this overzealous theory??

Cuetek

Feb27-10, 01:24 PM

But you haven't mentioned what that inhomogeneity will look like. Yes if half the sky is black and the other half is white, then yes its homogenous. But it's also possible for the universe to be wildly inhomogenous, but that fact may not be obvious. In order to find inhomogenity you have to first assume homogenity, make a lot of predictions and then find deviations from that.

Like I've said before, the CP is not generally assumed the way you say it is. It is not assumed in order to refute it so much as confirm it. It is widely assumed to be quite true, and most studies by far attempt vigorously to confirm it with all manner of liberal projections of the data using math that is itself derivative of the CP. Only very few accepted studies search for limits on the CP using the data at hand (I site examples of both types of studies in post #19 of this thread).

You defend the presumption of the CP like some kind of essential straw man devised as a foil against the greater truth. That's human nature, not scientific method. The scientific method is to make presumptions that are best supported by the data, and that would be the hierarchical principle.

You can still use the observable homogeneity at large scales as a property to facilitate scientific investigation without having to improbably claim that it prevails absolutely as does the CP. I don't care how many ways you can find to distort some localized relevance in support of the CP, the greater context of the data shows unequivocally from quarks to galaxy clusters that the universe is far more probably hierarchical than homogeneous. Presuming a hierarchical universe does not inhibit the scientific examination the WAMP or group distribution data for adherence or divergence from some baseline homogeneity.

In following the tenets of the scientific method, one should let the predominant data guide the investigation. We are running out of hard data at these distant scales and must rely more and more on inductive reasoning. Theorizing, by definition demands inductive reasoning, and the CP lives only in the narrow confines of deductive thinking.

Mark my words, the homogeneity of the universe will not prevail. It will not be seen in the future as a valuable tool. Rather it will be seen as a philosophical relic that long overstayed it's utility.

Anyone that wants to learn the WHOLE TRUTH about the universe should stay out of astrophysics.

So true. So I guess you better get out of astrophysics, huh? Because only the CP allows humans to believe they can know the whole truth, by allowing the whole universe everywhere to be just like it is here. Conversely the HP would assure us to never know the whole truth of the universe beyond our view. All the best.

-Mike