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Errors in big bang data ?

  1. Jun 15, 2010 #1

    wolram

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    http://www.sciencedaily.com/releases/2010/06/100613212708.htm

    ScienceDaily (June 14, 2010) — New research by astronomers in the Physics Department at Durham University suggests that the conventional wisdom about the content of the Universe may be wrong.

    Although at the bottom of the page he says (standard model may survive).
     
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  3. Jun 15, 2010 #2

    bapowell

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    Re: Errors in bib bang data ?

    This appears to be a criticism of the techniques used by the WMAP team to perform beam smoothing. The claim is that the technique used might adversely effect the resolution of the CMB measurements, widening the errors. If this does turn out to be the case (I would personally be interested in hearing what the WMAP science team has to say about it before making a conclusion), then the result would be that the error bars on the temperature spectrum of the CMB would widen, allowing more different kinds of models to be in agreement with data. The old standard model would certainly survive: if it fits the data now with smaller error bars, it will still fit it if these error bars widen (unless they do so in some asymmetric fashion). We should stay tuned and see what comes of this.
     
  4. Jun 15, 2010 #3

    nicksauce

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    Re: Errors in bib bang data ?

    While it would be very interesting if wmap's accuracy was different than previously thought, the reaction to this I've seen on the internet has been "OMG dark matter and dark energy don't exist anymore", and it is very annoying. The press releases given by the authors aren't helping either. This is interesting, but it is also important to separate fact from fiction.
     
  5. Jun 15, 2010 #4

    bapowell

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    Re: Errors in bib bang data ?

    Yes, I think it's very important to stress that there is no reason to expect that models that fit current data won't, for some reason, fit the same data with larger errors. Of course, the data could get so bad that you no longer need CDM or dark energy to fit CMB data (that would be hard to imagine), but even then, we have complementary astrophysical data that still supports these models.
     
  6. Jun 15, 2010 #5

    George Jones

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    Re: Errors in bib bang data ?

    Were the press releases written by the authors, or by PR people at the university?
     
  7. Jun 15, 2010 #6

    nicksauce

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    Re: Errors in bib bang data ?

    Well,

    This seems like an overstatement of the case. For all they know, the constraints could change hardly at all. I think they should wait until wmap data is analyzed with a revised error estimate before making a statement like this.
     
  8. Jun 16, 2010 #7

    Chalnoth

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    I sincerely doubt it'd make much of any difference, as most of the effects of the beam smoothing would be on the third harmonic peak, where with WMAP the dark energy signal is primarily at very low mulipoles and at the first harmonic peak, while the dark matter signal is primarily from the ratio of the first and second harmonic peaks.

    Improving the beam smoothing in WMAP data would slightly improve the error estimates and values, but I don't buy for an instant that it would significantly change any conclusions about dark matter or dark energy. The most it might potentially do is change the constraints on some of the inflation parameters, but then that was at the limit of detection with WMAP anyway.
     
    Last edited: Jun 16, 2010
  9. Jun 16, 2010 #8

    Chronos

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    I think dark matter is safe for now. There is plenty of other evidence that gives it legs aside from WMAP.
     
  10. Jun 16, 2010 #9
    If you read Shanks' other papers, he questions the scientific validity of cosmological constant tuning, inflation, dark matter, and dark energy. The evidence at this point in time is indicating dark matter will not survive.

    I believe his comment means he believes some version of the big bang theory will survive (i.e. he is not challenging the foundation of the theory) and in the specific case of his paper concerning the CMB calculation he is also appropriately and politely leaving himself a way out if his paper is challenged and shown to be incorrect.
     
  11. Jun 16, 2010 #10

    Chalnoth

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    Yeah, sounds like he's off his rocker. Dark matter, in particular, is strongly evidenced by a wide body of mutually-corroborating evidence. Yes, there are a small number of cosmologists/astrophysicists who continue to claim that dark matter is bunk, and a slightly larger number who rail against dark energy. A few of the ones who rail against dark energy (such as Rocky Kolb) are, in my opinion, quite good scientists. But most of the rest, and especially those who are fighting dark matter, seem to me to have gone the way of Halton Arp and Fred Hoyle.

    I really don't understand why it happens, but for some reason many formerly very good scientists occasionally turn crackpot. At this point, the evidence for dark matter, for instance, is just far too strong. Especially when the primary arguments against it (and against dark energy) are not evidence-based but philosophical.

    Here is the basic, basic problem: when cosmologists cite the evidence of dark matter, they don't cite any one, single discovery. They cite a wide array of mutually-corroborating pieces of evidence. Those arguing against it typically point at this one little discovery over here, or that one over there, and then proceed to use a very weak argument in an attempt to show that it doesn't work. The rest of us just say, "Yeah, not only is that a weak argument, but we've also got this and this and that and that over there."

    It doesn't help that the stated reasons for arguing against dark matter and dark energy are ridiculous in the first place.
     
  12. Jun 18, 2010 #11
    Let’s backup and summarize. What do we agree on? What are the different logical possibilities?

    This is a summary of the Sawangwit and Shanks paper.

    http://www.sciencedaily.com/releases/2010/06/100613212708.htm

    This a link to a specialists forum where another specialist in CMB interpretation discusses the Sawangwit and Shanks paper with Sawangwit and Shanks and other CMB specialists.

    http://telescoper.wordpress.com/2010/06/14/cosmology-on-its-beam-ends/

    Read and think about what the authors and other specialists are saying.

    (This is a link to the two Sawangwit and Shanks papers.)

    http://arxiv.org/PS_cache/arxiv/pdf/0912/0912.0524v2.pdf

    http://arxiv.org/PS_cache/arxiv/pdf/1006/1006.1270v1.pdf

    The CMB specialists are stating there is evidence as the original WMAP team knew what resultant they wanted to match the dark matter and dark energy ΛCDM predicted curve they used observations of Jupiter rather than a distant object to calibrate their data.

    (The specialists noted that in past when everyone thought a theory was correct data was interpreted to support the theory in question. When it became evident the theory in question was incorrect, people found errors in the original assumptions and analysis. i.e. Scientists are human and will from time to time unknowingly curve fit the analysis to fit the prediction.)

    If one uses a distance object (Sawangwit and Shanks used multiple distance objects) the resultant is roughly 30% less which no longer supports the existence of dark matter and dark energy. The specialists are stating that the CMB resultant with the beam correction, no longer supports the existence of dark matter and dark energy.

    One more time. No longer supports the existence of dark matter and dark energy. Is that statement correct? Yes or no?

    What do we know and what do we not know?

    There are a number of anomalous observations that require a physical explanation. I believe we all agree. Yes or no? (For example, the anomalous rotational velocities of spiral galaxies.)

    That fact does not mean dark matter and dark energy exist. Dark matter and dark energy are hypothesized physical entities. Anomalous observations that require a physical explanation cannot be used as support for the existence of dark matter and dark energy. Dark matter and dark energy are called dark matter and dark energy as they are placeholders for a physical mechanism to explain the observations.

    Logical proof of the existence of dark matter and dark energy requires specific observational data than can only be explained by dark matter and dark energy. What has been found is that observational data of galaxies does agree with dark matter predictions. If someone disagrees with that statement they need to provide specific observational data and papers that specifically supports the existence of dark matter and dark energy.

    The statement that there is plenty of other evidence to support the existence of dark matter and dark energy is an empty statement without proof. There is nothing to discuss, refute, or defend.

    My point is Sawangwit and Shanks’ finding, the Zenon (the most sensitive dark matter detection device every made.) negative finding for direct detection of dark matter, the spiral galaxy morphological observational disagreement between prediction and observation, the spiral galaxy rotational disagreement between prediction and observation, the number of satellite galaxies disagreement between prediction and observation indicates that the field must now start looking at other explanations for what is observed than dark matter and dark energy.

    It is very possible now based on analysis and observation that dark matter and dark energy does not exist.

    If dark matter and dark energy does not exist, the anomalous observations still requires a physical explanation.
     
    Last edited: Jun 18, 2010
  13. Jun 18, 2010 #12

    Chalnoth

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    Er, with WMAP's smallest beam size at 13 arc minutes, and with Jupiter having an angular size of about half an arc minute, a 30% overestimation of the beam size due to Jupiter not being a perfect point source isn't really plausible.

    And besides, as I've stated previously, it wouldn't change the WMAP results in the way suggested anyway.

    That statement is completely wrong.
     
  14. Jun 18, 2010 #13

    bapowell

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    A couple things worth pointing out. 1) Sawangwit and Shanks make no mention about what their results mean for dark matter/dark energy. This appears to be purely sensationalist hype generated by the pop-science media. People who make such claims lack an understanding of how cosmological parameters are derived from cosmological data. 2) No, it doesn't support that. At least nobody's shown this. With regards to the statement you quote, "If true this could mean that the ripples are significantly smaller, which could imply that dark matter and dark energy are not present after all.", I don't even know what that means. The effect of dark energy on the CMB has to do with the position of the first acoustic peak and the increase in power at low-l. Neither of these observations should be directly effected by making the "ripples smaller". The effect of DM is more directly related to the peaks -- in particular, the relative amplitudes of the 1st and 2nd peaks; and so of course there's a chance that the conclusions we draw from the CMB with regards to DM might be affected! We should absolutely investigate this! But nobody's done that yet, so we should cool it. Lastly, why is everyone acting like the only piece of scientific evidence for DM/DE comes from the CMB? It doesn't. If the CMB didn't exist, our evidence for DM/DE would weaken, but there are other astrophysical sources. This is a classic case of cherry-picking the data that supports the point. That's bad science and people should be called out on it.

    Wait...so you're using semantics to discount the physical validity of the concepts of dark matter and dark energy? I don't follow. Of course DM/DE are hypothetical entities -- all such physical explanations for a collection of phenomena are hypotheses until sufficient data accumulates to accept them into a theory. The underlying physics from which DM/DE arise is not fully understood -- hence the funny language. However, the hypothesis that particulate dark matter exists (a suggestion pretty well founded in modest extensions of the standard model of particle physics, and well accommodated as a cold thermal relic in the early universe) is reasonably well motivated. So far, its predictions agree well with cosmological observations. Will such a hypothesis stand up to all observations?? Probably not -- few do. Nobody should be claiming we have all the answers, we don't. As for dark energy, the proposition that vacuum energy gravitates is a reasonable hypothesis. The observational consequences of such a hypothesis are well supported by data (SN data, ISW, flat universe).

    Sorry, but that's not how science works. Physics is an empirical science, and as such, we don't have the luxury of formulating 'logical proofs' of phenomena. Surely you know that science as a framework is not meant to prove things. In science, one should propose a hypothesis and work out its predictions. These predictions should be matched against data. Competing hypotheses should be compared. At the end of the day, all we can do is make inferences, and choose the model that is statistically favored by the data. If there are other theories that compete with DM/DE, they should be (and are) considered.


    Does the act of citing these additional sources of evidence constitute 'proof'? There are plenty.

    These should be investigated. But is dark matter not capable of being adjusted to accommodate these new findings? How statistically relevant are these new findings anyway (compared to, say, CMB and LSS data)? That's important. Also, what do any of the things you listed have to do with dark energy? Just because they share the word "dark" doesn't mean that the possible refutation of one has anything to do with the other.

    Maybe. So let's do the analysis.

    Yes, and science will march on.
     
  15. Jun 18, 2010 #14

    Chalnoth

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    I doubt it. Basically, these sorts of issues tend to fix things in the low signal-to-noise regime, which would likely mean a fix on the amplitude of the third acoustic peak, which wouldn't significantly impact the dark matter results.

    The fundamental reason why they tend to fix things in the low signal-to-noise regime is because in the high signal-to-noise regime multiple cross-checks of the results are available, and WMAP has consistently and repeatedly passed these cross-checks (edit: well, not always. Every once in a while somebody finds an issue, but it's always turned out to be relatively minor).
     
  16. Jun 18, 2010 #15

    bapowell

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    Thanks Chalnoth, apologies. By the way...shouldn't BAO data serve as a valuable cross-check here? I mean...the ripples are there too...in like...the exact same places.
     
  17. Jun 18, 2010 #16

    Chalnoth

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    Well, BAO isn't my field of expertise, but my suspicion is that no, it wouldn't, because a modification of the beam would change the amplitudes of the peaks, not their positions, while from what I understand the BAO data is most sensitive as a measurement of the position, not the amplitude.

    Anyway, as I said previously, I think the most significant changes would be in the measured values of inflation parameters such as the spectral index.

    Edit, small caveat: changing the amplitudes of peaks will, in general, slightly adjust their positions, but usually much less than the change in amplitude itself.
     
  18. Jun 18, 2010 #17
    If you could site a paper that has proof of dark matter and dark energy, then we will have something to discuss.

    I have sited papers that shows observed spiral galaxy morphology does not agree with dark matter predictions, that observed spiral galaxy radial velocity profile does not agree with dark matter predictions, and that the observed number of satellite galaxies does not agree with dark matter predictions. Three strikes and you are out?

    I have sited the xenon paper that notes the most sensitive dark matter detection experiment has not detected dark matter.

    The scientific observations and analysis in published papers does not support the existence of dark matter. If you have any specific data and analysis that supports dark matter start a thread. I would be interested in discussing it.

    Anomalous observations that currently do not have an explanation does not proof dark matter exists and is that it is the cause of the anomalous observations. The papers I have sited show dark matter is logically not the cause, in the thread "Dark Matter, On the Ropes?" in the astrophysics section.

    That is how science works.

    People come up with hypothesis and then test the hypothesis against its predictions. When the hypothesis fails against multiple predictions, which is what has happened in this case, it is back to drawing board.
     
  19. Jun 18, 2010 #18

    bapowell

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    Are you seriously suggesting that there are no studies that support the existence of dark matter? People in this thread and elsewhere all over this forum have discussed these additional pieces of evidence at length. If you wish to learn about them, you simply need to go and look. I addressed the individual pieces of evidence that you list here...any thoughts on what I wrote? You do not appear to be approaching this problem with an open mind, since you are deliberately neglecting data that supports dark matter. I think you should admit that you probably have a personal, not necessarily scientifically derived, aversion to dark matter, and it really appears to be clouding your judgment. As a result, I don't think there's much point in continuing a scientific discussion on these topics.

    And again, science can't prove things. And again, you keep bringing up observations that disagree with current models of dark matter -- you haven't mentioned a single contention with dark energy, yet you keep including it in the discussion. So as not waste my time listing all the sources of evidence for DM/DE, I'll list one and see how you digest it: how about the SN1a data from Riess et al http://arxiv.org/abs/astro-ph/9805201 and Perlmutter et al http://arxiv.org/abs/astro-ph/9812133 .

    EDIT: Also, your rail against dark matter has really taken us far away from the intent of the thread, which was to discuss the findings of Sawangwit and Shanks. I think that has been satisfactorily addressed by people in this thread.
     
    Last edited by a moderator: Apr 25, 2017
  20. Jun 18, 2010 #19

    Chalnoth

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    Wow. Just wow. Dark matter, in particular, is strongly supported by a wide body of evidence. Studies of galaxy clusters, the CMB, and baryon acoustic oscillations are particularly telling. Discrepancies in much more complex systems, such as individual galaxies, are more likely telling us something interesting about galaxies themselves instead of about dark matter. Larger systems tend to be less sensitive to these complexities, and are thus much better evidence for dark matter.

    Dark energy is less well-evidenced, but the alternative explanations are getting increasingly ridiculous.
     
  21. Jun 18, 2010 #20
    There are two paper sited in your comment to support the existence of dark matter and dark energy.

    One paper that has observational data the universe is accelerating. Yes the universe is is accelerating however that does not prove dark energy is the cause.

    The second paper, is somewhat better. It is a 1998 paper that uses supernova data to support the total amount of energy and mass in the standard model. That does not prove dark energy or dark matter exist.

    Subsequent papers on supernova analysis has questioned the accuracy of the supernova explosion that is used for the standard candle.

    Now back to the Shanks' paper.

    I noticed no one was commented on the discussion by the authors and the specialists themselves on this subject. They appear to be senior scientists with many years experience in the field. Name calling and adjectives does not prove a point.

    http://telescoper.wordpress.com/2010/06/14/cosmology-on-its-beam-ends/

    The Shanks' paper shows problems in the CMB interpretation which removes the last pillar that was purported to support dark matter.

    Believe whatever you want. Understanding the cosmological problems that are and are not solved is a fundamental part of what the practice of science is. (i.e.That is why Shanks' wrote the paper.)

    Think of the issue in another way. What is or is not correct does not change. If dark matter does not exist, cosmology is on hold until observation data and analysis in papers such as Shanks, and the papers noted in Dark Matter, On the Ropes? are written.

    20 years ago people did not know that the xenon experiment would give negative detection for dark matter, that observed spiral galaxy morphology does not agree with dark matter predictions, that spiral rotational velocity does not agree with dark matter predictions, that the number of observed satellite galaxies does not agree with dark matter predictions.

    Let's wait for new data and new papers to discuss.
     
    Last edited by a moderator: Apr 25, 2017
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