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No Shadow From the Big Bang? 178

Posted by samzenpus
from the four-more-weeks-of-winter dept.
ultracool writes "In a finding sure to cause controversy, scientists at The University of Alabama in Huntsville (UAH) found a lack of evidence of shadows from "nearby" clusters of galaxies using new, highly accurate measurements of the cosmic microwave background (WMAP). Other groups have previously reported seeing this type of shadows in the microwave background. Those studies, however, did not use data from WMAP, which was designed and built specifically to study the cosmic microwave background."
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No Shadow From the Big Bang?

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  • The Vorlons were found travelling through Minbari space.
    • by smeghead (23355)
      I don't know why but I read that as Vogons travelling through Minmatar space.

      Too much eve for me maybe...
  • Maybe there are mini-big bangs going on. Maybe there wasn't one large one. Maybe, just maybe, there are bangs in the void of space which create our galaxies. Then, this would simply explain where our radiation comes from, the galaxies themselves, always radiating.

    (I'm sleepy. I hope I didn't mess that up too badly with poor grammar.)
    • Re: (Score:3, Funny)

      I hope I didn't mess that up too badly with poor grammar.

      No, it was the "not having any clue what the Big Bang theory is in the first place" where you went wrong.

  • How can the big bang cast a shadow if there's nothing outside thereof on which to cast it? Now that you've centered yourself, you're sure to win that corporate mini-golf tournament.
    • Re:Existensial? (Score:5, Informative)

      by arun_s (877518) on Thursday September 07, 2006 @05:06AM (#16058000) Homepage Journal
      How can the big bang cast a shadow if there's nothing outside thereof on which to cast it?

      Shadows require light, an object and an observer. The 'observer' is us here at the earth. The 'object' is this (from TFA):

      Galaxy clusters are the largest organized structures in the universe.[snip] The gravity created at the center of some clusters traps gas that is hot enough to emit X-rays.
      This gas is also hot enough to lose its electrons (or ionize), filling millions of cubic light years of space inside the galactic clusters with swarming clouds of free electrons. It is these free electrons which bump into and interact with individual photons of microwave radiation, deflecting them away from their original paths and creating the shadowing effect. This shadowing effect was first predicted in 1969 by the Russian scientists Rashid Sunyaev and Yakov Zel'dovich.


      And the 'light' is the background microwave radiation, until now assumed to be from the edges of the universe, beyond these clusters.
  • by Capt'n Hector (650760) on Thursday September 07, 2006 @05:00AM (#16057990)
    How do we know that the ±0.0001 K (or whatever it is exactly) fluctuations in the CMB isn't just from nearby galaxies? How do we know it is truly background information? No subtraction algorithm is THAT perfect.
    • Great question. In the case of instruments I've used to measure radiation backgrou it comes from measurements deep in caves that shield almost all cosmic radiation and have very low terrestrial radiation levels to get a true "dark" level. As far as knowning how good your subtraction algorithm is, you can use statistics to make claims about the performance of estimates.
  • by Anonymous Coward
    What happens when you mix dark energy with dark matter?
    • by tanveer1979 (530624) on Thursday September 07, 2006 @05:28AM (#16058053) Homepage Journal
      What happens when you mix dark energy with dark matter?

      A B-Grade Sci-fi thriller

      • by Omicron32 (646469)
        I award you my "Comment of the Month" award. You don't get anything except a vague sense of self-satisfaction that you made someone laugh, very hard.
      • by ultranova (717540)

        What happens when you mix dark energy with dark matter?

        A B-Grade Sci-fi thriller

        Or a typical 3D game.

      • by kerrle (810808)
        I would have said a B-grade vampire soap opera.
    • by ultranova (717540)

      What happens when you mix dark energy with dark matter?

      You get a voidstone, which can be used to make a sphere of annihilation. There's plenty of them in the Negative Energy/Material Plane.

      Alternatively, you could use the inspiration to make a "moody" 3D shooter - I'm eagerly waiting for "Bleak Blakness of the Dark Side of the Lightless Shadows of the Coal Mine of Insufficient Lightning". They've promised it's going to have not a single pixel brighter than RGB(0,0,0) - no wonder it requires a GeForce

  • by Nuffsaid (855987) on Thursday September 07, 2006 @05:39AM (#16058085)
    It is easy to form a layman idea about the geometry involved in this phenomenon. A wrong idea, that is. The article's drawing shows a galaxy cluster between us and a distant wall of light, casting a shadow cone. It is rather intuitive that the "wall of light" is actually part of a sphere surrounding us in every direction, with a radius of 13.7 billion light years. The sphere is actually a magnified image of the Universe as it was some time after the Big Bang, when it cooled down to the temperature required for the emission of the observed microwave radiation. And it is magnified not by some optical effect, but by the expansion of space itself. If you were in the cluster's position you would continue to see yourself at the center of such a sphere with radiation coming from all directions. Actually, this would be true for any place in the Universe. Add the fact that things move, light travels at a finite speed, and that the "wall of light" was essentially "here" 13.7 billion years ago, when the light was emitted. Throw in all the relativistic factors required on such scales, and what seemed like a simple geometry problem becomes a job for expert astronomers, not for me.

    My favourite explanation is that light and dark travel at different speeds...

    • by greg_barton (5551) *
      My favourite explanation is that light and dark travel at different speeds...

      You mean like a wave propagates through a medium, but the particles in the medium don't need to travel along with the wave? So, darkness is the wave and light is the medium?
  • by maxwell demon (590494) on Thursday September 07, 2006 @05:41AM (#16058091) Journal
    As a physicist (but no cosmologist or astrophysicist), I'm surprised that shadowing was expected. As far as I understood the article, the shadowing effect is expected not due to absorption/inelastic scattering (where I could understand the shadow effect), but due to elastic scattering (the photons just change their direction).

    Now it is obvious that the number of photons reaching us from behind is reduced by the elastic scattering process. However one of the basic properties of the cosmic background radiation is that is is nearly isotropic. And that means there should be an about equal amount of radiation scattered into our direction which would not have reached us otherwise.

    So is there anything I'm missing?
    • by hweimer (709734) on Thursday September 07, 2006 @07:08AM (#16058252) Homepage
      As far as I understood the article, the shadowing effect is expected not due to absorption/inelastic scattering (where I could understand the shadow effect), but due to elastic scattering (the photons just change their direction).

      The article is probably a bit misleading. The Sunyaev-Zel'dovich effect [uchicago.edu] seems to come from inelastic Compton scattering. This leads to a distortion of the original blackbody spectrum of the CMBR. The term "shadow" merely comes from the observation that at lower frequencies there are less photons being detected since they are shifted to higher frequencies.
      • Thanks for the link. So basically what I missed was that the heat does more than just providing electrons to scatter from, it also provides the scattered photons with extra energy on average.
    • Re: (Score:2, Interesting)

      by aadvancedGIR (959466)
      IANAP, but I would tend to consider the lack of shadow as a proof for the big bang, not against.
      If this radiation comes from the big bang, then it comes from every direction and this cluster of galaxies is as much the center of the universe as the earth itself. OTOH, having a "bright" and a "dark" side of this cluster would indicate that this radiation has a located source and therefore would invalidate the big bang theory.

      Of course, there are tons of effects I don't know or don't unerstand, so please expla
      • by ultranova (717540)

        IANAP, but I would tend to consider the lack of shadow as a proof for the big bang, not against. If this radiation comes from the big bang, then it comes from every direction and this cluster of galaxies is as much the center of the universe as the earth itself. OTOH, having a "bright" and a "dark" side of this cluster would indicate that this radiation has a located source and therefore would invalidate the big bang theory.

        Ambient Occlusion [wikipedia.org]. If there is light that seems to originate from every point (

  • by yeOldeSkeptic (547343) on Thursday September 07, 2006 @06:07AM (#16058145)

    A little shadow anomaly isn't going to seriously dent the Big Bang theory. There is so much evidence for the Big Bang and predictions based on it have been observed that it will take more than a little inconsistency to make the theory suspect. You need something more substantial than shadows to expect a rehauling of the Big Bang.

    Remember that there were serious questions about the applicability of Newtonian Dynamics on a large scale too when it was determined that galaxies could not have kept their structure if calculations were based on ND only. However, rather than modify ND, scientists chose to posit an unseen dark matter just to save ND. As it turns out, there is indeed dark matter!

    Don't sound the death knell on the big bang yet.

    • A little shadow anomaly isn't going to seriously dent the Big Bang theory. There is so much evidence for the Big Bang and predictions based on it have been observed that it will take more than a little inconsistency to make the theory suspect. You need something more substantial than shadows to expect a rehauling of the Big Bang.

      No, I wouldn't expect and overhaul of, or gross changes to, the Big Bang theory - but when a prediction made by the theory fails to pan out, it needs to be explained. Maybe the th

  • by dltaylor (7510) on Thursday September 07, 2006 @06:42AM (#16058208)
    The theory, if I understand it, is that since the CMB and the energy from the nebula should have taken the same time to reach from where they were then to where we are now, and assuming that the CMB was not somehow generated "in front of or "at" nebula (which we currently deduce from its very red-shifted frequency and distribution), then we should see the nebula's emissions, but not the same strength of CMB that is measured from the "background" at very small angular displacements from the nebula.

    I need to read the REAL article, since the "Science Daily" was a joke, but, here are some issues with the research as described:

    #1 the universe has no "edge" in any layman's sense of word. We're no more in the middle than some galaxy 8 billion light years away in any direction.

    #2 the CMB is NOT "pointed at" the Earth. It's going in every direction at the same time, including very, very small angles to "straight away" in any direction.

    #3 the WMAP antenna is very good, but it is NOT 100% unidirectional, so it will pick up energy from a very narrow cone, not a line straight away.

    Therefore the WMAP data will rarely show a "shadow" of much change in intensity, since the antenna will pick up significant CMB from off-axis of the line between the Earth and the nebula, even if the nebula is resolved to nearly all of the sample point. For that matter, it could be lensing on- or off-axis causing some of the intensity variation described in the artice.

    The variations in CMB are incredibly small in the first place, and we don't have THAT many significant digits of intensity in the measurement range. We only really detected them when we got WMAP up there. Any additional small variation in CMB co-incident with an ionized nebula is going to be difficult to unambiguously assign to "shadowing", and the even smaller variations of variations from nebula to nebula are very close to the statistical noise values of the original samples.

    As I said, maybe the "Astrophysical Journal" article is better presented, but so far, this doesn't sound well thought-out.
  • Big Bang (Score:2, Funny)

    by ms1234 (211056)
    This is slashdot, readers here have never experienced a big bang.
  • by gsn (989808) on Thursday September 07, 2006 @09:06AM (#16058566)
    For those of you who want to read more on it. I'm currently ploguhing through his paper and and a few others but if anyone of the top knows whether Lieu used sigma8 from the WMAP 3yr results and how he selected clusters and estimated cluster mass... Skimming Lieu's paper his conclusion already claims that it is not inconsistent with previous SZE data for individual clusters. Anyways back to digesting papers.
     
    Linkys

    A primer on the SZE [uchicago.edu]

    [PDF WARNING]
    Their paper on astro-ph [arxiv.org]

    The WMAP 3 year results paper [nasa.gov]

    [/PDF WARNING]

  • "Big Bang", whatever.

    When one tracks an animal or a person, one typically starts from the last known certainty. "It was here, maybe yesterday."

    Why don't we have the same expectations with all this investigation of origins? Why does everyone seem to be starting with some "In the beginning..." belief?

    An investigation of the past from existing evidence should result in an expanding tree of possible causes. "This layer of rock could have been deposited over milions of years or in a single cataclysm

    • Now, I'm feeding a troll, but I think that this one deserves an answer...

      "We say that the speed of light is a constant in all frames of reference. How was that measured? What assumptions did those measurements depend upon?"

      Speed of light was compared on several directions by this (very famous) experiment: Michelson-Morley experiment [wikipedia.org]. It relies on the assumption* that Earth is moving, it may be around the Sun, or just rotating, but moving.

      Now, there is a mechanism for maintaining the pedigree of scient

    • ""Big Bang", whatever. When one tracks an animal or a person, one typically starts from the last known certainty. "It was here, maybe yesterday.""

      The big bang theory started from the observation that all galaxies were "here" yesterday and have moved a bit further away today. It was developed the same way as every other scientific theory...

      Observation => new/modified/stronger theory => prediction => observation, rinse and repeat.

      "I'm not an advocate of Creationism, but they DO make one poin
      • by rdmiller3 (29465)

        "There is a need for a comprehensive, multilingual database of theories, experimental results, and their interdependencies."

        You are free to join the existing "database" by educating yourself as to what science is/isn't.

        That's the same, lame response I always get. "Go read the published material." That's essentially like telling someone to "go read the web without a search engine."

        Digging through yellowing documents and hunting down all their bibliographical references by hand is NOT the best

        • "That's the same, lame response I always get."

          Could it be that it's because it's the correct answer? With apologies to BadAnalogyGuy, it's like asking what is 2+2 and then complaining about the answer being 4 all the time. Science is not a pile of factoids you can just dive into, it is a methodical approach accompanied by a long history and seemingly odd customs.

          "Go read the published material"

          Perhaps you are dyslexic or something, you quote my answer in your post and then (directly under it) you s
  • It seems to me that there should not be shadows from the big bang, because all the bits of interstellar dust should be in thermal equilibrium with the CMB by now, and thus radiate the same microwaves. Unless I've missed something, this would seem to cause galaxies and galaxy clusters not to have shadows.

I'd rather be led to hell than managed to heavan.

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