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Saturday, November 22, 2014

Astronomers are Finally Starting to Question an Absurd Assumption

Posted by jlwile on January 17, 2013

The black circles in this figure represent the 73 quazars that make up the largest structure in the observed universe. The red crosses represent the 34 quazars that make up another massive structure. (Image is from reference 3.)

One of the more absurd assumptions that is routinely made in astronomy is called the cosmological principle. One way to phrase the principle is:

Viewed on a large enough scale, the properties of the universe are the same no matter where you are.

However, observations have never supported this assumption. Instead, the observable universe seems incredibly “lumpy,” with huge structures separated by vast areas devoid of structures. Nevertheless, cosmologists have doggedly taken the cosmological principle as their starting assumption when it comes to developing models of the universe, despite the fact that observations don’t support it.

Indeed, the cosmological principle is a necessary starting point for the Big Bang, which most, but certainly not all, astronomers think is a good description of the origin and development of the universe. As Paul Fleisher says in his book, The Big Bang:1

The cosmological principle is the central idea of the Big Bang theory. This rule says the universe is homogeneous and isotropic at very large scales.

Even if we go away from the Big Bang model, the vast majority of models that attempt to describe the universe start with the assumption that the cosmological principle is valid. There are some models that do not start with that assumption, but they are few and far between.2

I have always been skeptical of the cosmological principle, simply because it isn’t supported by observation. The universe doesn’t look homogeneous at all. Instead, it looks really “lumpy.” Nevertheless, when I read the scientific literature, the cosmological principle seems to be considered a fact in almost all of the astronomy-related papers.

It looks like that might be starting to change.

Roger G. Clowes and his colleagues report on their observation of what they call the Huge-LQG.3 It is a collection of 73 quasars, which are thought to be very bright, active centers of distant galaxies. It is thought that the properties of quasars are best explained by the presence of a supermassive black hole, whose mass is in excess of a billion times the mass of our sun. Obviously, that’s a lot of mass, and it is thought to be an integral part of any quasar.

So quasars are incredibly massive structures. While other large groups of quasars (known as LQGs) have been found, they generally consist of 5-40 members. In the figure at the top of this post, for example, the red crosses represent a LQG known as the Clowes & Campusano LQG, or CCLQG. It consists of 34 quasars lumped together. The group of quasars that were discovered by Clowes and his colleagues in this report is represented by the black circles in the figure. It is more than twice as big as the CCLQG, containing 73 quasars! That’s why they call it the Huge-LQG. It is a huge large quasar group. The fact that astronomers have to put “huge” and “large” together to describe this group of quasars gives you an idea of how big it really is!

Now, of course, the fact that it is big is very interesting. Indeed, its longest dimension is 1200 Megaparsecs or 4 billion light years across. However, the really interesting part is that this structure is so big that it causes the authors to question the cosmological principle. In their article, they discuss the calculations of Jaswant K. Yadav and his colleagues, which say that the cosmological principle predicts that no structure in the universe should exceed a size of about 370 Megaparsecs.4 Not only does the Huge-LQG significantly exceed that size, it seems to be in very close proximity to the CCLQG, indicating that this region of space is incredibly “lumpy” compared to other regions of space. Here’s how the authors put it:

In summary, the Huge-LQG presents an interesting potential challenge to the assumption of homogeneity in the cosmological principle. Its proximity to the CCLQG at the same redshift adds to that challenge.

I hope that what I read in this paper represents a trend. Rather than taking the cosmological principle as a blind assumption, astronomers should evaluate it in light of the data. Right now, the data strongly argue against the cosmological principle, which should tell you something about any model (like the Big Bang) that requires its assumption.

REFERENCES

1. Paul Fleisher, The Big Bang, Twenty-First Century Books 2006, p. 44
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2. Andersson, Lars and Coley, Alan, “Inhomogeneous cosmological models and averaging in cosmology: overview,” Classical and Quantum Gravity 28(16):160301, 2011. (available online)
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3. Roger G. Clowes, Kathryn A. Harris, Srinivasan Raghunathan, Luis E. Campusano, Ilona K. Söchting, and Matthew J. Graham, “A structure in the early Universe at z ∼ 1.3 that exceeds the homogeneity scale of the R-W concordance cosmology,” Monthly Notices of the Royal Astronomical Society doi:10.1093/mnras/sts497, 2013
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4. Jaswant K. Yadav, J. S. Bagla, and Nishikanta Khandai, “Fractal dimension as a measure of the scale of homogeneity,” Monthly Notices of the Royal Astronomical Society doi:10.1111/j.1365-2966.2010.16612.x, 2010
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Comments

14 Responses to “Astronomers are Finally Starting to Question an Absurd Assumption”
  1. Seth says:

    That’s incredible, thanks for sharing!
    If more evidence shows this fact, it would change the most basic assumptions in physics.

    I was really excited when I read this, I read a lot of science literature and this is the first time I’ve come across this, definitively a shock. I guess this (once again) it proves how little we really know.

  2. jlwile says:

    I am glad you enjoyed the article, Seth. I agree – it shows how little we really know!

  3. JLAfan2001 says:

    Dr. Wile
    Can you tell me if this affects the fine-tuning argument for God’s existence? If the laws of physics are affected, would this mean that we may find that the cosmological constants aren’t fine-tuned for life after all?
    I’m also very confused about what this means for the origin of the universe. If the steady-state theory has been ruled out and the big bang theory is in jeopardy, then how did the universe get here? It either started at some point or it’s always been here. Wouldn’t this greatly diminish the Kalam cosmological argument that William Lane Craig likes so much?
    This discovery seems to have the potential of putting the creation of the universe in trouble or am I just reading it wrong?

  4. jlwile says:

    JLAfan, I do think you are misreading the implications. First, the Big Bang is not what tells us the universe had a beginning. The expansion of the universe tells us that. Regardless of whether or not the Big Bang is true, we know that the universe is expanding. Since we know that, there are just a few options: (1) Expansion until the end, (2) a point at which gravity pulls back and brings the universe back to its starting point to start the process over and over again, (3) the steady state view. Numbers (2) and (3) are inconsistent with a lot of known physics, and they are the ones that allow for an eternal universe. Since (1) is the only option that is consistent with known physics, we know that the universe cannot be eternal and thus had to have a beginning. This is independent of the Big Bang. Thus, the rise or fall of the Big Bang has little to do with whether or not the universe had a beginning.

    Second, some aspects of the fine-tuning argument are connected to the Big Bang, but most are not. So if the Big Bang is wrong, some of the parameters that look to be fine-tuned might not be. Most of them, however, would still need fine-tuning. Of course, whatever theory replaces the Big Bang would probably have its own parameters that needed fine-tuning, so it is always possible that if the Big Bang is wrong, there would be more fine-tuning parameters.

  5. Blake Reas says:

    Very interesting article. I am interested in cosmological arguments for theism, and I never really liked the scientific arguments that Craig uses. He always makes the caveats that the philosophical arguments are the strong parts of his case, but I still think that people will always put more stock in what science “says” than deductive arguments (not that I think they are right), and that seems to me unfortunate, because if the Big Bang model ever did get overturned I think many would think that cosmological arguments are no good, which just isn’t true. Anyway, thanks for posting this.

  6. jlwile says:

    Thanks for your comment, Blake. I suspect that Dr. Craig thinks his philosophical arguments are stronger because he is a philosopher. I agree with you; the scientific arguments are the stronger arguments. As I say in the “about” section of this blog, it is hard for me to fathom anyone who has scientific training and does not believe in God.

  7. Jacob says:

    While you bring up some good points (our cosmological model is far from complete), you do so in a very skewed way. It seems you have some sort of confirmation bias afflicting your viewpoint.

    //One of the more absurd assumptions that is routinely made in astronomy is called the cosmological principle..//

    Immediately, you start off by claiming that one of the tenets of most cosmological models, a tenet that is backed up by empirical data, is “absurd.” This tenet is, as you rightly describe, is based on the universe being largely isotropic and homogeneous at great scales.

    With the findings of WMAP, the universe was shown to be isotropic to an astounding degree (anisotropy of less than 1/100,000). Also, we have a generalized distribution of radio galaxies. The diffusion of most light is also the same. The evidence is very convincing. Do you dispute the findings of WMAP or COBE?

    Homogeneity is a bit more difficult to measure and be sure of, but it has been proven to a reasonable degree. Whenever we pan out, there really isn’t that much clumpiness. however discovering one structure bigger than that does NOT automatically count as violating the cosmological principle – the structure can be the result of 2-3 smaller structures that by ‘random chance’ have been moving in the ‘right direction’ so as to come together without any initial help from gravity.
    While this structure is very interesting and may challenge some of the limits we have set on homogeneity, it in no way overturns the CP or shows that the CP is an “absurd” principle. It is used in any model of spacetime expansion from a singular point.

    I would like it if you would particularly point out what was wrong with what I have presented above.

    Cheers,
    Jacob

  8. jlwile says:

    Thanks for your comment, Jacob. I will have to disagree with you. The cosmological principle is not backed up by empirical data. In fact, it is contradicted by most empirical data, which is why it is absurd. When we look at the universe, no matter what scale we choose, the visible universe just doesn’t look homogeneous.

    I don’t dispute the findings of WMAP or COBE. However, they don’t back up the cosmological principle. For example, back in 2010, Copi and colleagues discussed large-scale anomalies in the maps of temperature anisotropies in the cosmic microwave background. In addition, Rossmanith and colleagues recently showed a violation of statistical isotropy in the cosmic microwave background.

    However, let’s assume those problems get ironed out (pun intended!). Even if the cosmic microwave background is isotropic, Barrett and Clarkson showed that this isn’t enough to support the cosmological principle, as some inhomogeneous models can produce a smooth cosmic microwave background.

    I agree that finding one structure bigger than the Yadav limit doesn’t show the cosmological principle is absurd. Astronomical observations have already done that. These data just add to the pile. You can try to explain around the Huge-LQG by hoping that smaller structures “just happened” to be moving in the right direction so as to come together, but that’s not enough. As the authors note, it’s not just the Huge-LQG. It’s also the fact that it is found in proximity to another large structure, the CCLQG. Thus, there is a very lumpy region out there, which violates the cosmological principle.

    Of course, the paper lists several other violations of the cosmological principle, such as large inhomogeneities in the distribution of superclusters, Gpc-scale correlations of galaxies, cosmic flows on approximately Gpc scales, and the fact that the polarization vectors of quasars are correlated on Gpc scales. The cosmological principle is pleasing, to be sure. It is just not reasonable based on the observational data that we have.

  9. Antonio says:

    Well a question and a comment. Question First – Jay I am curious how you completely divide the big bang from an expanding universe as if one is thrown out the other still stands (not disputing it just never heard that point of view before). I always saw them as tied together. The big bang dissenting page you link to quite often is suggestive of alternate explanations for things like redshift etc. So If the big bang is in trouble then wouldn’t the idea of an expanding universe also be challenged? What evidence would you see as still holding up beyond any reasonable dispute?

    and to Blake’s observation I think Craig’s Kalaam cosmological argument at least is far from just being philosophical. Its perfectly within scientific observation that everything that begins has a cause. It IS what science says its just not what unbelieving scientists say.

  10. jlwile says:

    Thanks for your question and comment Antonio. I think the main thing you have to understand is that the Big Bang is only one specific way in which the universe can expand. The Big Bang says that the universe is expanding without any geometry at all. It is expanding equally everywhere. That’s not the kind of expansion we are used to experiencing. The expansion we see happening every day has a geometry – usually spherical. If you assume that the universe is expanding spherically rather than without a geometry, you no longer have a Big Bang cosmology. Indeed, young-earth creationists use a spherically-expanding universe in their cosmology. As this article notes, another fundamental assumption of the Big Bang is a homogeneous universe. However, there are models that posit an inhomogeneous expanding universe. So in the end, the Big Bang is a specific model of universal expansion. Change some assumptions, and you can still have an expanding universe without the Big Bang.

    Do I think that universal expansion is beyond any reasonable dispute? Not at all. I think the preponderance of the evidence points to an expanding universe, but I wouldn’t be surprised if one of the alternative explanations ends up being more consistent with the data. That’s another thing you have to understand about astrophysics. All of science is tentative, but astrophysics is especially tentative, because we are trying to understand the entire universe from the vantage point of our little corner of it. That’s really hard to do!

    I would agree with you that The Kalaam cosmological argument is consistent with what science says about the universe.

  11. Antonio says:

    Thanks Jay,

    I will have to dig into that link. More fun reading :)

  12. Jason says:

    Still trying to get my head around this Dr Wile, apologies. Please bear with me as I try to understand the logic behind this article.

    The evidence seems to point to our universe having a beginning. Scientists have accepted the big bang model to explain these events prior to and after this “beginning”.

    If the big bang theory were to be proven wrong, this wouldn’t imply our universe had no beginning just that our understanding of how it started etc is flawed?

    Is this correct?

    It was always my understanding that the big bang theory was the basis with which we knew our universe had a beginning?

  13. jlwile says:

    No problem, Jason. You are correct that if the Big Bang were proven wrong, it wouldn’t in any way imply that the universe had no beginning. It would just mean the Big Bang isn’t the proper description of the way the universe began and subsequently developed. There are other cosmological models that require the universe to have a beginning but are inconsistent with the Big Bang. The one I linked in my reply to Antonio is an example.

    No, the Big Bang is not the basis of the idea that the universe had a beginning. It is simply one model that is consistent with the universe having a beginning.

  14. Jason says:

    As always I appreciate your time and clarification Dr Wile, thank you.

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