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So, if it turns out not be, the scale at which we're viewing it simply isn't large enough? This is a semantic problem with the word 'enough'. Anything will X when you do enough Y, and if it doesn't X, that only means you need to Y more. Is there no formal definition which avoids this problem?
TittilateMyTasteBuds ( talk) 10:09, 15 February 2020 (UTC)
-- Logical Gentleman ( talk) 05:06, 30 July 2016 (UTC)
What observations and axioms support this. Hackwrench 18:08, 1 November 2005 (UTC)
This is true and there is more to it. The distribution of matter (galaxies and clusters) , dark matter, dark energy all seem homogeneous and isotropic. In fact, we can put some limit on the inhomogeneity and anisotropy of the universe on the large scales and we find out that it is agreeing very well with the cosmological principle. But we cannot ignore the tiny possibility that the cosmological principle is not 100% true, but we might never detect the slight variations. There is also a lot of theoretical arguments in favor of the cosmological principle. I don't want to go into the details but let's say that it is very hard to invent a successful model of our universe in which the cosmological principle is not respected. Basically, all work on cosmology (with FRW cosmological models at least) uses equations which were derived assuming the cosmological principle. So I'd say there is very good support in favor of the Cosmological Principle. (F.G. - McGill - Physics) —Preceding unsigned comment added by 74.56.206.181 ( talk) 15:50, 18 November 2007
i've deleted the section on "inhomogeneities" because it misinterprets the substance of the specific paper cited (which i've read): for example, in the concluding paragraph, the authors speculate about the implications of their findings for areas of the universe outside their observational sample and offer "tilt" as a pervasive structural feature of the universe *as a whole*, a claim which requires the cosmological principle to assert! the two points that were omitted or misappreciated in the earlier version of this wikipedia article are that (1) the cosmological principle is in one respect a *distributional* assumption about structure (isotropy) and a *validity* assumption about observational location (homgeneity); and (2) the cosmological principle is not violated by any gross anomaly, such as a "really big hole", unless this constitutes evidence of something novel or inexplicable in terms of smaller similar structures or known physical laws. perhaps the problem that is missed by previous writers is that the cosmological principle is a double edged sword, serving as a presumption that we can extend known physical laws to all phenomena, and as a "null hypothesis" that highlights events we *cannot* explain as the points deserving more intensive inquiry -- inquiry based on the working assumption that the events are explicable in terms of known physical laws. Macevoy ( talk) 16:28, 8 January 2010 (UTC)
OK, I'll bite: Under what logic does the Cosmological principle disprove the Anthropic principle? Do sources exist for such claims? ---- Jasonuhl 21:26, 13 October 2005 (UTC)
I agree that this needs to be expanded. I think more needs to be said or this part removed. It seems to be that the Cosmological principle is a statement about averages over cosmological distances (as the article indicates) while humanity exists on an entirely negligible length-scale. It is not obvious to me how the two should be compared or where a contradiction exists. Threepounds 06:42, 26 November 2005 (UTC)
I found a link in Timeline of cosmology that said Milne "formalized" this cosmological principle. While I agree that he did, I don't think that the gist of his argument is well presented here. For instance, Milne did not like the idea of a finite universe, nor did he like the idea of expanding space.
Milne says in Relativity, Gravitation, and World Structure "I am well aware that some mathematicians believe that such difficulties are at once swept awy if we use the concept of 'curved space.' I have examined such attempts at explanation with the greatest care, and I have found that in all cases the proposed explanations break down at some point. Two-dimensional analogies with hypothetical inhabitants on the surface of a sphere fail as soon as we recall that a survey of the astronomical universe is made by taking a photograph with a telescope and camera, and that, for a telescope of arbitrarily large light-gathering power, either the number of nebulae that can be counted is finite and therefore contains one faintest and so presumably most distant member, or it is infinite, in which case either the same nebula is photographed as an infinite number of separate spots or the total number of actual nebulae in existence is infinite. The latter will be our eventual conclusion. Here I am only concerned to argue that the phrase 'curvature of space' used in connexion with astronomical photographs merely involves a mist of mysticism. Such photographs can always be interpreted in flat space, and then the assumption of a finite number of density-maxima inevitably leads to some kind of accessible edge of the universe."
In this book, at least, Milne eventually concluded that the universe was not finite in terms of number of nebulae. He did not conclude that space was curved. JDoolin 16:27, 27 August 2006 (UTC)
I never read that book but I wanted to point out one thing. If you assume no big bang and an eternal universe, then you can assume that a large enough telescope could possibly measure an infinite number of nebulae. But if there is a big bang, then you cannot see further than the light travel-time since the big bang so you will always get a finite number of nebulae no matter how big your telescope is. This explanation had a name I cannot recall and was figured out long ago. Anyway, I guess this was already obvious and that this book is contemplating the possiblity of no big-bang. —Preceding unsigned comment added by 74.56.206.181 ( talk) 15:57, 18 November 2007
Sorry I forgot I had posted to this discussion. Milne's model is a model with a big bang which actually is a Big Bang. An infinite amount of matter exploding from a point, the majority of which expands outward at the speed of light. The shrapnel in the middle forms the galaxies of the observable universe. The expanding surface is a time-dilated shell we would see the inner part of and call the CMBR. You can actually see further than the speed of light times the age of the universe in such an environment, if you take into account acceleration and Lorentz Transformations, changing reference frames etc. The Milne Model is an infinite mass model. Not, contrary to popular belief, a zero mass model. ( JDoolin ( talk) 01:21, 1 August 2010 (UTC))
Guys, this doesn't read at all well for someone not well versed in cosmology/physics. I imagine it is quite complex but is it possible to be expresed in more simple terms, or at least to explain the concept a little better? Some parts of it read almost like the article was created with the intention of being as obscure as possible. :-) Diliff | (Talk) (Contribs) 23:47, 21 August 2007 (UTC)
"The universerve is the same everywhere" does not make anything clearer. It just states you assume the reader to be an imbicil. 192.114.175.2 12:06, 6 September 2007 (UTC)
i agree with the initial complaint. i've edited the lede to clarify the essential point of the cosmological principle; the previous version fetishized homogeneity and isotropy into incomprehensibility. i've also deleted the section "a different view", since the issues of extrapolation it describes are not at issue in the cosmological principle (which is a principle of interpretation of evidence, not a principle of knowing what we can't see), and because the two sources cited in that section are both textbooks in the social sciences, not in astonomy or cosmology. Macevoy ( talk) 19:08, 9 January 2010 (UTC)
I propose that Perfect Cosmological Principle should be merged into this article as a new section, since it's a simple extension of the subject discussed here and there's not much more to add to the other article that wouldn't be repeating this article. Cosmo0 21:20, 22 September 2007 (UTC)
These two concepts should not be merged or confused. The Cosmological Principle is what we commonly refer to and is consistent with the standard model of cosmology (big bang, inflation, dark energy, etc...). The Perfect Cosmological Principle is a weird concept which contradicts this standard model. For instance, there cannot be a big bang if the universe never changes in time. The Perfect Cosmological Principle is somewhat along the lines of Einstein's original view of a static universe. Even if some strange theories might be able to fit in the Perfect Cosmological Principle, it remains an unproved principle unlike the Cosmological Principle which seems to apply very well to our universe. I hope it is now clear that these two concepts should not be merged together and it should even be emphasized that they are very different. I hope this helps. Sorry this is my first post on Wikipedia so I don't know the format and stuff. ( F.G. - McGill - Physics )—Preceding unsigned comment added by 74.56.206.181 ( talk) 15:40, 18 November 2007
I don't get it. An isotropic fractal is an oxymoron then, or am I missing something? (it's not unlikely that I am) -- Extremophile 19:25, 8 October 2007 (UTC)
There is a big hole in the sky! Although you can't see it with the naked eye it actually covers almost 3 degrees of the sky, and to put that into perspective the full Moon covers about half a degree! Until recently no-one was sure how big or far away this void was but the latest calculations suggest it is 900 million light-years across and 8,000 million light-years away. So can we still say the universe is homogeneous and isotropic? Is the Big bang theory still true?
24 November 2007
IN AUGUST, radio astronomers announced that they had found an enormous hole in the universe. Nearly a billion light years across, the void lies in the constellation Eridanus and has far fewer stars, gas and galaxies than usual. It is bigger than anyone imagined possible and is beyond the present understanding of cosmology. What could cause such a gaping hole?
— Preceding unsigned comment added by 202.42.202.67 ( talk) 06:39, 30 November 2007
What do you mean by aymtotically homogeneous? How big must the hole be before we can abandon the idea that the universe is homogeneous and isotropic? —Preceding unsigned comment added by 202.42.202.67 ( talk) 02:10, 3 December 2007 (UTC)
Huge misconceptions are being bandied about here!
The cosmological principle is completely unscientific. That doesn't mean it's wrong or useless, but it's an assumption based on weak circumstantial evidence. Not only is the cosmological principle unscientific, but it's impossible to give enough evidence for it to remove reasonable doubt about it. This is because "large scale" has no upper bound in definition: if the universe is larger than the observable universe, good luck "proving" anything about the unobservable parts of the universe. Even if the universe ends up smaller than the observable universe, the principle is too vague to "prove."
As for this specific scientific development, many voids and superfilaments (strings of superclusters of galaxies) have been found before. It's not as if scientists are suddenly "baffled" at this just because the press imagine they are. The superstructure of the universe is little understood, but for example CDM theory doesn't do a bad job at explaining it.
67.171.43.170 ( talk) 02:02, 30 September 2008 (UTC)
DECEMBER 2013- A new bigger structure was discovered, namely the Hercules-Corona Borealis Great Wall. It's 10 billion light-years across. Can this structure challenge the cosmological principle? == Johndric Valdez ( talk) 02:17, 20 December 2013 (UTC)==
Spring Back ( talk) 05:25, 24 September 2008 (UTC)
The article should present how the principle emerged into cosmological physics, including opposition and criticism. __ meco ( talk) 10:58, 2 May 2010 (UTC)
as described here http://phys.org/news/2013-03-planck-reveals-universe.html
and discussed in 2008 here
http://blogs.discovermagazine.com/cosmicvariance/2008/07/17/a-new-cmb-anomaly/
basically the Planck data has confirmed the CMB anisotropy first seen in the WMAP data, but now in very fine detail. There is an axis to the Universe, and in one direction the contrast of background temperature variations is higher than in the other direction. It's very close to the ecliptic.
This data throws a wrench in the Cosmological principle. the " uniformity of conclusions drawn from observation" is not the same, and we know it now. Far in one direction the Universe is different than far in the other direction. signed: jmdugan 66.109.99.16 ( talk) 02:52, 25 March 2013 (UTC)
I added the Planck results using well researched and accepted references, and tied it back to the WMAP and COBE results. Copi et. al., and others were waiting for confirmation or denial of the correlations from Planck, and confirmation is what they got. Wyattmj ( talk) 16:01, 10 April 2013 (UTC)
The criticism seems a bit disingenuous since the cosmological principle is just an assumption not something that has ever been considered a fact. Is the opinions of Popper really relevant in an article about cosmology? 85.230.137.182 ( talk) 16:32, 27 February 2014 (UTC)
3.26 ly/pc x 6,500 Mpc = 21.2 Gly. Article says 11.1 Gly. See article on "parsec". — Preceding unsigned comment added by 198.111.167.50 ( talk) 23:03, 27 October 2014 (UTC)
There is some material in the lead that is both incorrect and out of place:
This is followed by a discussion about upper limits on variations in the fine structure constant. This is just plain wrong. The cosmological principle certainly *does* refer to physical structure. What the author of this material is talking about is referred to as local position invariance (LPI), which is closely related to the equivalence principle. There is nothing inherently cosmological about LPI; it can be tested on both laboratory scales and cosmological scales. You can have LPI without the cosmological principle. I'm going to remove this incorrect material from the lead.-- 76.169.116.244 ( talk) 23:29, 10 May 2015 (UTC)
The Universe is expanding at a superluminal rate if we compare afar regions. This superluminal mean distance will shrink to point expansion everywhere, the omni-singularity or Big Bang. Big Bang is default space at the ultimate apex of decohesion, thus there is no need to transform any quantum information so that will get homogeneous. There is only one form of "default space", and it always explodes Big Bang way. Homogeneity is derived via superlumic defaulting spacetime (apex of decohesion fills the gaps expansion created because absolute decohesion among the universal components is not allowed). — Preceding unsigned comment added by 2A02:587:410E:8300:5C60:852E:2E99:DF75 ( talk) 02:57, 24 February 2016 (UTC)
The article has quotes like:
That sound like just homogeneity though, doesn't it.
The explanation of isotropy given is:
How do we get there from 'the same physical laws apply throughout'? That's not the obvious reading of that phrase. -- 174.116.141.16 ( talk) 12:23, 27 September 2016 (UTC)
In other words, the flux or change in any of the universes physical properties is equal to zero. TittilateMyTasteBuds ( talk) 09:57, 15 February 2020 (UTC)
This is written under the criticism heading: "In September 2016, however, studies of the expansion of the Universe that have used data taken by the Planck mission show it to be highly isotropical, reinforcing the cosmological principle."
However my understanding of the referenced paper was that if homogeneity is assumed, the we can say that the universe is very likley (121,000:1) expanding in an isotropic way. — Preceding unsigned comment added by Dextrion ( talk • contribs) 19:57, 30 October 2016 (UTC)
There are 2 paragraphs here about the results of the Planck mission that seem to contradict:
I read this as: The Planck data showed lots of anisotropies that cannot be ignored, suggesting a potential rethink regarding the Cosmological constant.
I read this as: The Planck data showed lots of isotropy, so there's no need to rethink the Cosmological constant.
The second paragraph starts with "however", implying that it contradicts, but supersedes, the points presented just before it about large observed structures. Yet I don't understand how these things are related. If there are these large structures, how come the Planck mission didn't pick them up as well? Perhaps the Planck mission was measuring a different thing. In that case, why should the Planck data override the existence of these structures?
It sounds like the second sentence is just given as a convenient conclusion to tie up the loose ends introduced by the "Inconsistencies" section.
Perhaps the paragraphs can be brought together, using something like "The Planck data showed mostly a lot of uniformity, though it did find some discrepancies". Spur ( talk) 20:11, 24 May 2017 (UTC)
Please add information on these two papers (or their subjects along with information on related papers) to section "Inconsistencies":
Here is what I added to the article 2020 in science:
- Scientists publish a study which suggests that the Universe is no longer expanding at the same rate in all directions and that therefore the widely accepted isotropy hypothesis might be wrong. While previous studies already suggested this, the study is the first to examine galaxy clusters in X-rays and, according to Norbert Schartel, has a much greater significance. Beyond the potential cosmological implications, it shows that studies which assume perfect isotropy in the properties of galaxy clusters and their scaling relations can produce strongly biased results. [1] [2]
- Scientists report verifying measurements 2011-2014 of what seem to be discrepancies in four measurements of the fine-structure constant, a basic physical constant used to measure electromagnetism between charged particles, which indicates that there might be directionality with varying natural constants in the Universe which would have implications for theories on the emergence of habitability of the Universe and be at odds with the widely accepted theory of constant natural laws and the standard model of cosmology which is based on an isotropic Universe. [3] [4] [5] [6]
Also see Fine-structure constant#Is the fine-structure constant actually constant?
-- Prototyperspective ( talk) 14:24, 23 May 2020 (UTC)
In the section above, Looks like this one is on its way out, the quoted article uses the abbreviation CMB, but it is in parentheses and is immediately preceded by the phrase it abbreviates. Our encyclopedia article omits what seems to me to be a common courtesy, for the first use of an abbreviation to be in parentheses, immediately following the phrase it abbreviates. Would such a well-defined appearance of the abbreviation, rather than just throwing the abbreviation into the text as in our encyclopedia article, be a violation of some Wikipedia stylistic tic with which I am unfamiliar?
As a convenience to you, I quote the referenced section, where the preferred usage (at any rate, my preferred usage) appears in a quotation from a journal article:
There is a significant problem in the phrasing of some of these claims, and the choice of references. The reality is that these claims are all controversial, but many of them are just listed as factual. Other sections use rather partial language instead of a neutral tone, for example:
"The European Space Agency (the governing body of the Planck Mission) has concluded that these anisotropies are, in fact, statistically significant and can no longer be ignored."
The source says nothing about "ignored", this is very unscientific language. The sources cited in the CMB dipole section are particularly biased, the article doesn't weight this discussion at all or even hint that these claims may be controversial. There are no papers cited on the other side of the argument, several studies have been able to recover the amplitude of the kinematic dipole. This section is entirely one sided, but it does not reflect the state of the field today. The other issue is that all of these references are primary sources. LazyAstronomer ( talk) LazyAstronomer ( talk) 10:06, 27 July 2023 (UTC)
The section "Violations of homogeneity" includes a list of "violations" but such primary evidence is not encyclopedic. The list is de facto synthetic original research WP:SYNTH. The section should have secondary references reviewing and analyzing the individual claims. Johnjbarton ( talk) 17:42, 15 January 2024 (UTC)
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So, if it turns out not be, the scale at which we're viewing it simply isn't large enough? This is a semantic problem with the word 'enough'. Anything will X when you do enough Y, and if it doesn't X, that only means you need to Y more. Is there no formal definition which avoids this problem?
TittilateMyTasteBuds ( talk) 10:09, 15 February 2020 (UTC)
-- Logical Gentleman ( talk) 05:06, 30 July 2016 (UTC)
What observations and axioms support this. Hackwrench 18:08, 1 November 2005 (UTC)
This is true and there is more to it. The distribution of matter (galaxies and clusters) , dark matter, dark energy all seem homogeneous and isotropic. In fact, we can put some limit on the inhomogeneity and anisotropy of the universe on the large scales and we find out that it is agreeing very well with the cosmological principle. But we cannot ignore the tiny possibility that the cosmological principle is not 100% true, but we might never detect the slight variations. There is also a lot of theoretical arguments in favor of the cosmological principle. I don't want to go into the details but let's say that it is very hard to invent a successful model of our universe in which the cosmological principle is not respected. Basically, all work on cosmology (with FRW cosmological models at least) uses equations which were derived assuming the cosmological principle. So I'd say there is very good support in favor of the Cosmological Principle. (F.G. - McGill - Physics) —Preceding unsigned comment added by 74.56.206.181 ( talk) 15:50, 18 November 2007
i've deleted the section on "inhomogeneities" because it misinterprets the substance of the specific paper cited (which i've read): for example, in the concluding paragraph, the authors speculate about the implications of their findings for areas of the universe outside their observational sample and offer "tilt" as a pervasive structural feature of the universe *as a whole*, a claim which requires the cosmological principle to assert! the two points that were omitted or misappreciated in the earlier version of this wikipedia article are that (1) the cosmological principle is in one respect a *distributional* assumption about structure (isotropy) and a *validity* assumption about observational location (homgeneity); and (2) the cosmological principle is not violated by any gross anomaly, such as a "really big hole", unless this constitutes evidence of something novel or inexplicable in terms of smaller similar structures or known physical laws. perhaps the problem that is missed by previous writers is that the cosmological principle is a double edged sword, serving as a presumption that we can extend known physical laws to all phenomena, and as a "null hypothesis" that highlights events we *cannot* explain as the points deserving more intensive inquiry -- inquiry based on the working assumption that the events are explicable in terms of known physical laws. Macevoy ( talk) 16:28, 8 January 2010 (UTC)
OK, I'll bite: Under what logic does the Cosmological principle disprove the Anthropic principle? Do sources exist for such claims? ---- Jasonuhl 21:26, 13 October 2005 (UTC)
I agree that this needs to be expanded. I think more needs to be said or this part removed. It seems to be that the Cosmological principle is a statement about averages over cosmological distances (as the article indicates) while humanity exists on an entirely negligible length-scale. It is not obvious to me how the two should be compared or where a contradiction exists. Threepounds 06:42, 26 November 2005 (UTC)
I found a link in Timeline of cosmology that said Milne "formalized" this cosmological principle. While I agree that he did, I don't think that the gist of his argument is well presented here. For instance, Milne did not like the idea of a finite universe, nor did he like the idea of expanding space.
Milne says in Relativity, Gravitation, and World Structure "I am well aware that some mathematicians believe that such difficulties are at once swept awy if we use the concept of 'curved space.' I have examined such attempts at explanation with the greatest care, and I have found that in all cases the proposed explanations break down at some point. Two-dimensional analogies with hypothetical inhabitants on the surface of a sphere fail as soon as we recall that a survey of the astronomical universe is made by taking a photograph with a telescope and camera, and that, for a telescope of arbitrarily large light-gathering power, either the number of nebulae that can be counted is finite and therefore contains one faintest and so presumably most distant member, or it is infinite, in which case either the same nebula is photographed as an infinite number of separate spots or the total number of actual nebulae in existence is infinite. The latter will be our eventual conclusion. Here I am only concerned to argue that the phrase 'curvature of space' used in connexion with astronomical photographs merely involves a mist of mysticism. Such photographs can always be interpreted in flat space, and then the assumption of a finite number of density-maxima inevitably leads to some kind of accessible edge of the universe."
In this book, at least, Milne eventually concluded that the universe was not finite in terms of number of nebulae. He did not conclude that space was curved. JDoolin 16:27, 27 August 2006 (UTC)
I never read that book but I wanted to point out one thing. If you assume no big bang and an eternal universe, then you can assume that a large enough telescope could possibly measure an infinite number of nebulae. But if there is a big bang, then you cannot see further than the light travel-time since the big bang so you will always get a finite number of nebulae no matter how big your telescope is. This explanation had a name I cannot recall and was figured out long ago. Anyway, I guess this was already obvious and that this book is contemplating the possiblity of no big-bang. —Preceding unsigned comment added by 74.56.206.181 ( talk) 15:57, 18 November 2007
Sorry I forgot I had posted to this discussion. Milne's model is a model with a big bang which actually is a Big Bang. An infinite amount of matter exploding from a point, the majority of which expands outward at the speed of light. The shrapnel in the middle forms the galaxies of the observable universe. The expanding surface is a time-dilated shell we would see the inner part of and call the CMBR. You can actually see further than the speed of light times the age of the universe in such an environment, if you take into account acceleration and Lorentz Transformations, changing reference frames etc. The Milne Model is an infinite mass model. Not, contrary to popular belief, a zero mass model. ( JDoolin ( talk) 01:21, 1 August 2010 (UTC))
Guys, this doesn't read at all well for someone not well versed in cosmology/physics. I imagine it is quite complex but is it possible to be expresed in more simple terms, or at least to explain the concept a little better? Some parts of it read almost like the article was created with the intention of being as obscure as possible. :-) Diliff | (Talk) (Contribs) 23:47, 21 August 2007 (UTC)
"The universerve is the same everywhere" does not make anything clearer. It just states you assume the reader to be an imbicil. 192.114.175.2 12:06, 6 September 2007 (UTC)
i agree with the initial complaint. i've edited the lede to clarify the essential point of the cosmological principle; the previous version fetishized homogeneity and isotropy into incomprehensibility. i've also deleted the section "a different view", since the issues of extrapolation it describes are not at issue in the cosmological principle (which is a principle of interpretation of evidence, not a principle of knowing what we can't see), and because the two sources cited in that section are both textbooks in the social sciences, not in astonomy or cosmology. Macevoy ( talk) 19:08, 9 January 2010 (UTC)
I propose that Perfect Cosmological Principle should be merged into this article as a new section, since it's a simple extension of the subject discussed here and there's not much more to add to the other article that wouldn't be repeating this article. Cosmo0 21:20, 22 September 2007 (UTC)
These two concepts should not be merged or confused. The Cosmological Principle is what we commonly refer to and is consistent with the standard model of cosmology (big bang, inflation, dark energy, etc...). The Perfect Cosmological Principle is a weird concept which contradicts this standard model. For instance, there cannot be a big bang if the universe never changes in time. The Perfect Cosmological Principle is somewhat along the lines of Einstein's original view of a static universe. Even if some strange theories might be able to fit in the Perfect Cosmological Principle, it remains an unproved principle unlike the Cosmological Principle which seems to apply very well to our universe. I hope it is now clear that these two concepts should not be merged together and it should even be emphasized that they are very different. I hope this helps. Sorry this is my first post on Wikipedia so I don't know the format and stuff. ( F.G. - McGill - Physics )—Preceding unsigned comment added by 74.56.206.181 ( talk) 15:40, 18 November 2007
I don't get it. An isotropic fractal is an oxymoron then, or am I missing something? (it's not unlikely that I am) -- Extremophile 19:25, 8 October 2007 (UTC)
There is a big hole in the sky! Although you can't see it with the naked eye it actually covers almost 3 degrees of the sky, and to put that into perspective the full Moon covers about half a degree! Until recently no-one was sure how big or far away this void was but the latest calculations suggest it is 900 million light-years across and 8,000 million light-years away. So can we still say the universe is homogeneous and isotropic? Is the Big bang theory still true?
24 November 2007
IN AUGUST, radio astronomers announced that they had found an enormous hole in the universe. Nearly a billion light years across, the void lies in the constellation Eridanus and has far fewer stars, gas and galaxies than usual. It is bigger than anyone imagined possible and is beyond the present understanding of cosmology. What could cause such a gaping hole?
— Preceding unsigned comment added by 202.42.202.67 ( talk) 06:39, 30 November 2007
What do you mean by aymtotically homogeneous? How big must the hole be before we can abandon the idea that the universe is homogeneous and isotropic? —Preceding unsigned comment added by 202.42.202.67 ( talk) 02:10, 3 December 2007 (UTC)
Huge misconceptions are being bandied about here!
The cosmological principle is completely unscientific. That doesn't mean it's wrong or useless, but it's an assumption based on weak circumstantial evidence. Not only is the cosmological principle unscientific, but it's impossible to give enough evidence for it to remove reasonable doubt about it. This is because "large scale" has no upper bound in definition: if the universe is larger than the observable universe, good luck "proving" anything about the unobservable parts of the universe. Even if the universe ends up smaller than the observable universe, the principle is too vague to "prove."
As for this specific scientific development, many voids and superfilaments (strings of superclusters of galaxies) have been found before. It's not as if scientists are suddenly "baffled" at this just because the press imagine they are. The superstructure of the universe is little understood, but for example CDM theory doesn't do a bad job at explaining it.
67.171.43.170 ( talk) 02:02, 30 September 2008 (UTC)
DECEMBER 2013- A new bigger structure was discovered, namely the Hercules-Corona Borealis Great Wall. It's 10 billion light-years across. Can this structure challenge the cosmological principle? == Johndric Valdez ( talk) 02:17, 20 December 2013 (UTC)==
Spring Back ( talk) 05:25, 24 September 2008 (UTC)
The article should present how the principle emerged into cosmological physics, including opposition and criticism. __ meco ( talk) 10:58, 2 May 2010 (UTC)
as described here http://phys.org/news/2013-03-planck-reveals-universe.html
and discussed in 2008 here
http://blogs.discovermagazine.com/cosmicvariance/2008/07/17/a-new-cmb-anomaly/
basically the Planck data has confirmed the CMB anisotropy first seen in the WMAP data, but now in very fine detail. There is an axis to the Universe, and in one direction the contrast of background temperature variations is higher than in the other direction. It's very close to the ecliptic.
This data throws a wrench in the Cosmological principle. the " uniformity of conclusions drawn from observation" is not the same, and we know it now. Far in one direction the Universe is different than far in the other direction. signed: jmdugan 66.109.99.16 ( talk) 02:52, 25 March 2013 (UTC)
I added the Planck results using well researched and accepted references, and tied it back to the WMAP and COBE results. Copi et. al., and others were waiting for confirmation or denial of the correlations from Planck, and confirmation is what they got. Wyattmj ( talk) 16:01, 10 April 2013 (UTC)
The criticism seems a bit disingenuous since the cosmological principle is just an assumption not something that has ever been considered a fact. Is the opinions of Popper really relevant in an article about cosmology? 85.230.137.182 ( talk) 16:32, 27 February 2014 (UTC)
3.26 ly/pc x 6,500 Mpc = 21.2 Gly. Article says 11.1 Gly. See article on "parsec". — Preceding unsigned comment added by 198.111.167.50 ( talk) 23:03, 27 October 2014 (UTC)
There is some material in the lead that is both incorrect and out of place:
This is followed by a discussion about upper limits on variations in the fine structure constant. This is just plain wrong. The cosmological principle certainly *does* refer to physical structure. What the author of this material is talking about is referred to as local position invariance (LPI), which is closely related to the equivalence principle. There is nothing inherently cosmological about LPI; it can be tested on both laboratory scales and cosmological scales. You can have LPI without the cosmological principle. I'm going to remove this incorrect material from the lead.-- 76.169.116.244 ( talk) 23:29, 10 May 2015 (UTC)
The Universe is expanding at a superluminal rate if we compare afar regions. This superluminal mean distance will shrink to point expansion everywhere, the omni-singularity or Big Bang. Big Bang is default space at the ultimate apex of decohesion, thus there is no need to transform any quantum information so that will get homogeneous. There is only one form of "default space", and it always explodes Big Bang way. Homogeneity is derived via superlumic defaulting spacetime (apex of decohesion fills the gaps expansion created because absolute decohesion among the universal components is not allowed). — Preceding unsigned comment added by 2A02:587:410E:8300:5C60:852E:2E99:DF75 ( talk) 02:57, 24 February 2016 (UTC)
The article has quotes like:
That sound like just homogeneity though, doesn't it.
The explanation of isotropy given is:
How do we get there from 'the same physical laws apply throughout'? That's not the obvious reading of that phrase. -- 174.116.141.16 ( talk) 12:23, 27 September 2016 (UTC)
In other words, the flux or change in any of the universes physical properties is equal to zero. TittilateMyTasteBuds ( talk) 09:57, 15 February 2020 (UTC)
This is written under the criticism heading: "In September 2016, however, studies of the expansion of the Universe that have used data taken by the Planck mission show it to be highly isotropical, reinforcing the cosmological principle."
However my understanding of the referenced paper was that if homogeneity is assumed, the we can say that the universe is very likley (121,000:1) expanding in an isotropic way. — Preceding unsigned comment added by Dextrion ( talk • contribs) 19:57, 30 October 2016 (UTC)
There are 2 paragraphs here about the results of the Planck mission that seem to contradict:
I read this as: The Planck data showed lots of anisotropies that cannot be ignored, suggesting a potential rethink regarding the Cosmological constant.
I read this as: The Planck data showed lots of isotropy, so there's no need to rethink the Cosmological constant.
The second paragraph starts with "however", implying that it contradicts, but supersedes, the points presented just before it about large observed structures. Yet I don't understand how these things are related. If there are these large structures, how come the Planck mission didn't pick them up as well? Perhaps the Planck mission was measuring a different thing. In that case, why should the Planck data override the existence of these structures?
It sounds like the second sentence is just given as a convenient conclusion to tie up the loose ends introduced by the "Inconsistencies" section.
Perhaps the paragraphs can be brought together, using something like "The Planck data showed mostly a lot of uniformity, though it did find some discrepancies". Spur ( talk) 20:11, 24 May 2017 (UTC)
Please add information on these two papers (or their subjects along with information on related papers) to section "Inconsistencies":
Here is what I added to the article 2020 in science:
- Scientists publish a study which suggests that the Universe is no longer expanding at the same rate in all directions and that therefore the widely accepted isotropy hypothesis might be wrong. While previous studies already suggested this, the study is the first to examine galaxy clusters in X-rays and, according to Norbert Schartel, has a much greater significance. Beyond the potential cosmological implications, it shows that studies which assume perfect isotropy in the properties of galaxy clusters and their scaling relations can produce strongly biased results. [1] [2]
- Scientists report verifying measurements 2011-2014 of what seem to be discrepancies in four measurements of the fine-structure constant, a basic physical constant used to measure electromagnetism between charged particles, which indicates that there might be directionality with varying natural constants in the Universe which would have implications for theories on the emergence of habitability of the Universe and be at odds with the widely accepted theory of constant natural laws and the standard model of cosmology which is based on an isotropic Universe. [3] [4] [5] [6]
Also see Fine-structure constant#Is the fine-structure constant actually constant?
-- Prototyperspective ( talk) 14:24, 23 May 2020 (UTC)
In the section above, Looks like this one is on its way out, the quoted article uses the abbreviation CMB, but it is in parentheses and is immediately preceded by the phrase it abbreviates. Our encyclopedia article omits what seems to me to be a common courtesy, for the first use of an abbreviation to be in parentheses, immediately following the phrase it abbreviates. Would such a well-defined appearance of the abbreviation, rather than just throwing the abbreviation into the text as in our encyclopedia article, be a violation of some Wikipedia stylistic tic with which I am unfamiliar?
As a convenience to you, I quote the referenced section, where the preferred usage (at any rate, my preferred usage) appears in a quotation from a journal article:
There is a significant problem in the phrasing of some of these claims, and the choice of references. The reality is that these claims are all controversial, but many of them are just listed as factual. Other sections use rather partial language instead of a neutral tone, for example:
"The European Space Agency (the governing body of the Planck Mission) has concluded that these anisotropies are, in fact, statistically significant and can no longer be ignored."
The source says nothing about "ignored", this is very unscientific language. The sources cited in the CMB dipole section are particularly biased, the article doesn't weight this discussion at all or even hint that these claims may be controversial. There are no papers cited on the other side of the argument, several studies have been able to recover the amplitude of the kinematic dipole. This section is entirely one sided, but it does not reflect the state of the field today. The other issue is that all of these references are primary sources. LazyAstronomer ( talk) LazyAstronomer ( talk) 10:06, 27 July 2023 (UTC)
The section "Violations of homogeneity" includes a list of "violations" but such primary evidence is not encyclopedic. The list is de facto synthetic original research WP:SYNTH. The section should have secondary references reviewing and analyzing the individual claims. Johnjbarton ( talk) 17:42, 15 January 2024 (UTC)