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Space Science

200,000 Elliptical Galaxies Point the Same Way 448

Posted by kdawson
from the axis-of-opportunity dept.
KentuckyFC sends us to arXiv, as is his wont, for a paper (abstract; PDF preprint) making the claim that 200,000 elliptical galaxies are aligned in the same direction; the signal for this alignment stands out at 13 standard deviations. This axis is the same as the controversial alignment found in the cosmic microwave background by the WMAP spacecraft.
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200,000 Elliptical Galaxies Point the Same Way

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  • by FuzzyDaddy (584528) on Thursday August 30, 2007 @11:28AM (#20412805) Journal

    They all point outwards from the centre of the universe.

    Me.

    Actually, this has already been observed. [wikipedia.org]
  • galaxyzoo.org (Score:5, Informative)

    by Kartoffel (30238) on Thursday August 30, 2007 @11:28AM (#20412813)
    It's been posted before, but if this sort of thing interests you, get over to Galaxy Zoo and help them classify galaxies.
  • Um, no they don't (Score:2, Informative)

    by Normal_Deviate (807129) on Thursday August 30, 2007 @11:32AM (#20412869)
    The sample is 200,000 eliptical galaxies, and they showed a statistical tendency to point in a preferred direction. They most certainly do *not* all point the same way.
  • by massivefoot (922746) on Thursday August 30, 2007 @11:39AM (#20412983)
    I think we're confusing two slightly different terms here. If they all point the same way it is most definitely not "isotropic," as there is clearly something different about that direction. If, however, as you move through the galaxy you find that the direction the galaxies are locally pointing does not change, it's still "homogeneous."
  • Re:Why? (Score:5, Informative)

    by Anonymous Coward on Thursday August 30, 2007 @11:46AM (#20413095)
    From the paper:

    "A discussion of possible causes for these alignments is beyond the scope of this paper. "

    i.e. We don't know....
  • Re:A grain of salt (Score:2, Informative)

    by exp(pi*sqrt(163)) (613870) on Thursday August 30, 2007 @11:48AM (#20413127) Journal
    > First, he assumes that all elliptical galaxies have a point-of-view from which they appear circular. So let's consider the alternative: elliptical galaxies are actually elliptical but they have their ellipses aligned in just such a way that from Earth they could be construed as being circles with a strong preference to align towards a particular axis. Does that not sound a little ridiculous to you? There are times when having a flawed methodology makes your results sronger - not weaker. This is one of those cases.
  • Re:A grain of salt (Score:5, Informative)

    by bperkins (12056) on Thursday August 30, 2007 @11:54AM (#20413207) Homepage Journal
    > First, he assumes that all elliptical galaxies have a point-of-view from which they appear circular.

    All ellipses have a point of view where they project as a circle. Are you saying that his elliptical galaxies aren't elliptical? Even if they weren't, how would that create a selection bias?

    > He doesn't give much real discussion to the error in the measurements, which is significant.

    How would "error in the measurements" cause a selection to a particular orientation?

    Random error wouldn't move the average, just make the distribution wider. In fact random error ought to make the distribution more isotropic.

  • by at_18 (224304) on Thursday August 30, 2007 @11:57AM (#20413245) Journal
    Now if these 200,000 galaxies are all in a particular region of the universe, THAT would be explosive news, but, unless I completely misread the article, this isn't the case.

    It is the case. They were specially selected to be close to us (redshift < 0.20). I suspect these 200,000 galaxies are a fairly significant fraction of all the galaxies near us.
    Of course, they are close to us because more distant galaxies would be too difficult to investigate, but this doesn't change the fact that they are all in the same particular region of the universe.

  • Re:Why? (Score:3, Informative)

    by Shag (3737) on Thursday August 30, 2007 @11:59AM (#20413273) Homepage
    The researchers I work with are interested in targets at z=0.03-0.08, which they consider "nearby." (Their targets aren't galaxies.)

    That's 400 million to 1 billion light years.

    Right around the corner.

    z=0.20 is sufficiently distant that the restaurants don't even deliver.
  • by BlueStraggler (765543) on Thursday August 30, 2007 @12:00PM (#20413293)
    My reading of the abstract is that he looked at a sample size of 200,000, and found a 13-SD bias to one direction in that sample size.
  • Re:Why Not? (Score:5, Informative)

    by mlewan (747328) on Thursday August 30, 2007 @12:12PM (#20413513) Homepage Journal
    "If things started out as a big bang, on some scale, we will find a "center" of the universe. "

    I thought that was not the case. The big bang started in a point, but a point that is equally far from every other point in the universe, so there is no "centre". It is not a very intuitive statement, but that is what I understood from some article or other on the subject.

  • Re:A grain of salt (Score:5, Informative)

    by Bazman (4849) on Thursday August 30, 2007 @12:19PM (#20413601) Journal
    His "random computer generated results" test is what we statisticians call a 'Monte-Carlo' test. Its perfectly valid, given the assumptions he is working under.

    Suppose you throw 10 possibly biased dice and score 50 in total (where the average score would be 30).

    You then get 10 definitely fair dice and throw them 100 times, counting the total each time. If these trials only score 50 or more once, then the chances of your possibly biased dice being fair are 1 in 99. That's pretty much what he's done.

    With dice its possible to compute the probability exactly without doing the trials, since the behaviour of uniform probabilities (ie even chance of scoring 1 to 6) are well known and easy to compute. But if you have a situation of elliptical galaxies and their apparent projection on a sphere viewed from the earth then I suspect the computations may be harder...

  • by Anonymous Coward on Thursday August 30, 2007 @12:46PM (#20414021)
    Let's note that:

    1) This guy is a high-energy physicist, not an astronomer.

    2) He has two published articles on extragalactic astronomy, both from the early 90s, which have picked up a grand total of 4 citations.

    3) He has put up 3 papers on the arXiv in the last few months, all on this subject. None of them are stated to have been submitted for review, and indeed they are not in the style of any of the major relevant journals.

    Yeah, yeah, ad hominem and all that. I'll read it more carefully later if I have time (but I'm a bit busy writing a paper of my own, like, for submission and peer review and all that). He does appear to enjoy abusing statistics, both here and in his earlier papers.

    I just kinda think that Slashdot could report on all the many scientific discoveries that are actually likely to be true, rather than grand claims based on a couple of preprints by someone with little experience in the field.
  • by pretygrrl (465212) on Thursday August 30, 2007 @12:55PM (#20414127) Journal
    did a quick search, looks like this is the author: http://front.math.ucdavis.edu/author/M.Longo [ucdavis.edu]
    PhD physics, teaches U of MI
    another quick search of the article, and doesn't look like he mentions "Fingers of God" or Doppler at all. Outside the scope of the paper?
    i really wish people would stop w. the dumb ass soviet russia overlords bs
    perhaps that way, i could actually weed thru and see what the physicists have to to say on this.
  • Re:Why? (Score:4, Informative)

    by B'Trey (111263) on Thursday August 30, 2007 @12:56PM (#20414137)
    Your first thought was correct. You'd feel centrifugal force (actually centripetal force - centrifugal force [wikipedia.org] is actually a convenient fiction) only because of the mass outside the top which you're spinning in relation to. Unless there's a metauniverse outside the universe which influences this one in some fashion, and this universe is spinning relative to that one, then talking about the angular momentum of the universe seems as though it should be nonsensical.
  • by JeanPaulBob (585149) on Thursday August 30, 2007 @01:14PM (#20414411)
    ...well, I have a MS in Physics, anyway. Well, Applied Physics. In semiconductors. Anyway...

    I think another poster said it a bit more intuitively, that the point is now smeared out everywhere. That sounds roughly right to me.

    Another thing to realize is that the Big Bang doesn't mean that an explosion happened in a single point in empty space, and then everything expanded outward. It's that space itself was compressed down into a single point, and then expanded. There was nothing outside the Big Bang for it to expand out into. Every point in the universe was infinitely closer together. All the energy was really close together--really dense--so it was really hot. Then as things got less dense, the temperature decreased. In one sense, everywhere is the center of the Big Bang.

    This is also why distant galaxies can be receding away from us faster than the speed of light. Because expansion doesn't mean that galaxies are moving through space. (In relativity, nothing can move through space faster than c.) Instead, the distance between us is increasing as space itself expands. (You can visualize that as making two marks with a pen on a deflated balloon, and then blowing up the balloon. The two marks don't move on the balloon, but they do get further apart.)
  • Why would it (Score:5, Informative)

    by Moraelin (679338) on Thursday August 30, 2007 @01:18PM (#20414449) Journal
    IANAAP either, but I see it like this: imagine you have 4 spinning tops in the corners of a square. (The spinning tops are the galaxies.) The square itself doesn't spin, but the round things in the corners do. If all 4 rotate in the same direction, the system has a decidedly non-zero angular momentum, namely the sum of the 4. You can also easily find a frame of reference (e.g., centered the centre of the square and with the X and Y axes aligned with the side of the square) that doesn't rotate, and measure everything relative to it.

    Or if it makes it easier to imagine, think of the science gag of having a very fast spinning flywheel in a suitcase. Ask someone to carry it for you, or leave it around and see if anyone tries to steal it. (Though these days it'll more likely be the blown up by the SWAT or whatever equivalent your country has.) If the suitcase is horizontal (lying on the side), someone's going to have a beast of a time trying to pick it up. Or if it's standing, they'll have a beast of a time taking a corner with it. Though the suitcase (universe) doesn't rotate, the flywheel (galaxy) in it does, and the angular momentum of it all is very much non-zero.

    Now think of a suitcase with 4 flywheels in it, or 200,000 little flywheels. The suitcase itself doesn't rotate, the centres of the wheels don't rotate around anything, but the total system has a total angular momentum. Anyone trying to mess with that piece of luggage is in for a bit of surprise.
  • Re:Why? (Score:4, Informative)

    by Maury Markowitz (452832) on Thursday August 30, 2007 @01:20PM (#20414473) Homepage
    > but how can the entire Universe's angular momentum be non-zero?

    Excellent question. So excellent that it led to an entire alternate model of gravity. A trip to the wiki is always useful: Brans-Dicke theory

    So, anyone want to put odds on dark matter going the way of the cublical atom in, say, ten years?

    Maury
  • by willijar (99554) on Thursday August 30, 2007 @01:41PM (#20414727)
    Energy is a scalar not a vector - no direction. Flow of energy (power) has a direction.
  • Re:Why Not? (Score:5, Informative)

    by Maury Markowitz (452832) on Thursday August 30, 2007 @01:49PM (#20414831) Homepage
    > If things started out as a big bang, on some scale,
    > we will find a "center" of the universe.

    But understanding why this is so is what makes all of this fun.

    Remember that modern metric theories, of which General Relativity is just one, posit that the universe is four dimensional. Three space dimensions and one time dimension make up a four dimensional "spacetime". Unless you have seen an explaination of exactly what this means, it's just words, like "the universe is gizifa". This can lead to misunderstandings.

    I'll try to explain what this means, using a model I'm sure you've seen before, but likely poorly explained. Consider a balloon, partially inflated. The surface of the balloon, the "skin", is effectively a two dimensional object. The balloon as a whole is three dimensional. You have a two dimensional surface enclosing a three dimensional volume. Still with me?

    The reason we use this model is because it is very similar to our model of the universe. In this model everything you see around you, the three dimensional world, is the "surface" of a larger four dimensional construct. Just as the skin of a balloon is a 2D surface of a 3D space, everything you see around you is in the 3D skin of a 4D space. Still with me?

    Consider the balloon again. Critically, there is no "center" to the surface. Where is the middle of the surface of a sphere? Where is the middle of the surface of the Earth? The question itself is just "wrong". In the case of the Earth we arbitrarily decided to draw lines on it in certain placed, latitude and longitude. You could do the same with a balloon, make the neck the "north pole" for instance. By the same token we could have chosen some other coordinate system entirely, let's put the "west pole" in Ecuador!

    There is a point of the balloon as a whole that can be thought of as the center, through. Its in the space "below" the surface that's filled with air. The same is true of the Earth, the center is down below us, about 6400 km away. But, critically, that point does not lie on the surface.

    Now one more thing to consider. Draw some dots on the outside of the balloon. Label one of them "milky way". Now start inflating the balloon. You'll notice that the dots will move away from each other as you inflate them. In fact, from the point of view of the "milky way", all the other dots are moving away from it. But the same is true of all the other dots too. No matter which one you pick to observe, you'll see that everything moves away from it. And that's because, for lack of a better way to put it, space itself is getting bigger. In fact, the dots aren't really moving at all relative to their original locations on the surface of the balloon, their real motion is along a line drawn into the middle of the volume, that "real center".

    In the case of the universe the same thing applies. We look out in space and we see that everything is moving away from us. This is surprising if the universe is a 3D space, but complete expected if it's 4D. So where is the center of the universe? It's "down" somewhere. And what is that missing direction? Well we already said it, it's time. So what does that mean?

    That means the center of the universe is a point in time, not space.

    As soon as you really grasp this model you'll see why everyone likes it. For one, it trivially answers lots of different questions:

    1) why is everything moving away from us?
      it's not, everything is just "inflating"
    2) why do we appear to be in the middle?
      its just the way it looks, and it looks the same way everywhere else too
    3) why are we moving apart at all?
      because time is going forward (just look at your watch)

    Hope this helps!

    Maury
  • by Moraelin (679338) on Thursday August 30, 2007 @02:06PM (#20415025) Journal
    I didn't mean just mass, as in, they tend to stay behind unless you push them. I meant angular momentum, as in, they tend to stay pointing in the same direction. That would happen even in a perfect vacuum.

    Well, anyway, the thing with the tops and the briefcase was probably just an unneeded tangent. (I do a lot of those.) The important part is that the total system has a non-zero total angular momentum even if the centres of the tops don't move.

    Of course, the galaxies themselves could still move around each other, or around the centre of mass, or, really, whatever. I don't know enough to rule that out. I'm just saying that even without that, if they're aligned, there _still_ would be a total angular momentum.
  • From TFA (Score:5, Informative)

    by Kozar_The_Malignant (738483) on Thursday August 30, 2007 @02:57PM (#20415705)

    From the paper:

    "A discussion of possible causes for these alignments is beyond the scope of this paper. "

    The sentence abouve is followed by: "R. Buniy et al. (2006) discuss a universe that is not spherically symmetric due to magnetic fields or cosmic defects in the context of the CMB alignments. A large scale cosmic magnetic field acting on protogalaxies in the early stages of galaxy formation seems to provide a possible mechanism for explaining the elliptic and spiral spin alignments and has been proposed as a mechanism for causing the CMB alignments by Campanelli et al. 2006."

    i.e. We don't know....
    i.e. but here a couple of ideas.

  • Re:Why? (Score:5, Informative)

    by Ash Vince (602485) on Thursday August 30, 2007 @03:18PM (#20415939) Journal

    Explaining 'beyond the scope of this paper' _IS_ saying they do not know why.
    Sort of yes.

    Anyone who has done Physics (or any other cutting edge science) to a high enough level will know that this is always true. The maxim I remember was that every answer asks a thousand questions. This is certainly true in terms of the astrophysics of spiral galaxies.

    Nobody even fully understands gravity even though the current understanding was presented by Newton and is known to break down as soon as you apply it to more than one body of approximately equal mass.

    They could have waited until the paper they published didn't leave some nagging great question answered, but they would have been waiting an eternity to publish an infinitely long paper that nobody would have ever been able to finish reading anyway. Since this is impractical, they published what they knew and left it to their successors (or themselves in a few years) to answer why. Even if they had have answered this why they would have found more why's just around the corner the someone could have posted to slashdot anyway.
  • Re:A grain of salt (Score:3, Informative)

    by davecl (233127) on Thursday August 30, 2007 @04:22PM (#20416857)
    > First, he assumes that all elliptical galaxies have a point-of-view from which they appear circular.

    All ellipses have a point of view where they project as a circle. Are you saying that his elliptical galaxies aren't elliptical? Even if they weren't, how would that create a selection bias?


    Actually there's a fair bit of evidence that elliptical galaxies are in fact 'tri-axial' - they have different sizes in all three dimensions, like a rugby ball or an american football that's been squashed slightly. They would thus appear elliptical from any viewing angle.

    (And yes, IAAA).
  • Re:Why? (Score:1, Informative)

    by Anonymous Coward on Thursday August 30, 2007 @04:53PM (#20417297)
    Misquoted and unattributed; good going there.
  • Re:Why? (Score:3, Informative)

    by Jon Erikson (198204) on Friday August 31, 2007 @06:55AM (#20422933)
    The spinning bucket thing is related to Mach's princicple [wikipedia.org], which played a part in Einstein's thinking about the universe... although GR doesn't actually say anything about it.

FORTRAN is a good example of a language which is easier to parse using ad hoc techniques. -- D. Gries [What's good about it? Ed.]

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