200,000 Elliptical Galaxies Point the Same Way 448
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.
Re:Centre of the universe (Score:5, Informative)
galaxyzoo.org (Score:5, Informative)
Um, no they don't (Score:2, Informative)
Re:Assumption busting... (Score:3, Informative)
Re:Why? (Score:5, Informative)
"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)
Re:A grain of salt (Score:5, Informative)
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.
Re:I don't see how this matters... (Score:5, Informative)
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)
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.
Re:I don't see how this matters... (Score:4, Informative)
Re:Why Not? (Score:5, Informative)
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)
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...
Before we get too excited (Score:5, Informative)
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.
Re:Centre of the universe (Score:2, Informative)
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)
IAAP (I Am A Physicist), and... (Score:5, Informative)
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)
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)
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
Re:Think on a very basic level... (Score:2, Informative)
Re:Why Not? (Score:5, Informative)
> 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
I didn't mean just mass (Score:3, Informative)
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)
"A discussion of possible causes for these alignments is beyond the scope of this paper. "
Re:Why? (Score:5, Informative)
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)
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)
Re:Why? (Score:3, Informative)