Slashdot Mirror
"Dark Flow" Outside Observable Universe
DynaSoar writes "NASA astrophysicists have discovered what they claim is something outside the observable universe exerting an effect on the observable. The material is pulling clusters of galaxies towards a region of space known not to contain sufficient matter to create the effect. They can only speculate on what the material is and how space might differ there: 'In these regions, space-time might be very different, and likely doesn't contain stars and galaxies (which only formed because of the particular density pattern of mass in our bubble). It could include giant, massive structures much larger than anything in our own observable universe. These structures are what researchers suspect are tugging on the galaxy clusters, causing the dark flow.'"
Now I feel even smaller than I did yesterday. Good job, science!
Since no one reads TFA anyway, and since you clearly didn't:
The universe is thought to have formed about 13.7 billion years ago. So even if light started travelling toward us immediately after the Big Bang, the farthest it could ever get is 13.7 billion light-years in distance. There may be parts of the universe that are farther away (we can't know how big the whole universe is), but we can't see farther than light could travel over the entire age of the universe.
And then:
A theory called inflation posits that the universe we see is just a small bubble of space-time that got rapidly expanded after the Big Bang. There could be other parts of the cosmos beyond this bubble that we cannot see. In these regions, space-time might be very different, and likely doesn't contain stars and galaxies (which only formed because of the particular density pattern of mass in our bubble). It could include giant, massive structures much larger than anything in our own observable universe. These structures are what researchers suspect are tugging on the galaxy clusters, causing the dark flow.
Finally, on a side note, years of watching slashdot paid off in a truly interesting story!
An old-timer with old-timey ideas.
Years of watching slashdot paid off in a truly interesting story
Yes and the editors missed the once-in-a-lifetime opportunity to run it under the heading "NASA SCIENTISTS DISCOVER GOD." Damn!
Better to be despised for too anxious apprehensions, than ruined by too confident a security. --Edmund Burke
But I'd say if lots of really big things are being affected, then there could be a bigger thing out there.
It's a theory I know. I'd like to call it Cen's Big Fucking Thing theory, it's a big ball of stuff, chairs, signs, tanks, gravel and so on, literally sucking the universe dry of interesting stuff. A universal suck, maybe even a multiversal suck mechanism. Either way, I'm pretty sure we'll not see it coming.
Task Mangler
I'm actually pretty excited at this news. Granted, my understanding of astrophysics is limited to Hawking books and guests of George Noory (kidding, kind of). But I look forward to anything that seems to pin down the concept of 'dark matter'.
Dark matter to me has always smacked of a Victorian Era flimflam artist talking about the aether. And I don't care how dapper Mortimer T. Snerd is dressed, I'm not drinking his dark matter kool-aid until I can get a better explination for it than 'its invisible, supermassive, unobservable, and so totally there'. If you can't explain it to me, the interested layman, you may need to put your theory back in the crucible o' truth. Its probably not done yet.
-=Bang Bang=-
Somebody remind Professor Farnsworth not to point the smelloscope at the dark flow. He passed out last time.
> NASA astrophysicists have discovered what they claim is something outside the observable universe exerting an effect on the observable.
The third episode of Brian Greene's "Elegant Universe" documentary miniseries on PBS said that while matter is confined to the known dimensions, its possible that gravity isn't and so can move through dimensions. The example they feel is that we could possibly detect the gravity of 'something' in another Universe by its gravity, even though we could never actually touch it. Wonder if this is it?
http://www.pbs.org/wgbh/nova/elegant/
The Dark Matter in US is pulling a ball busting amount of money away from tax payers to Large Banks.
In this area of Universe known as Capitol Hill and White House, the normal laws of space-time continumm is suspended so that banks which screw up your money get your money to bail out themselves.
"Doing what i can, with what i have." ~ Burt Gummer
" If the known universe is expanding outward, that means that it has to have someplace to go, right?
Or am I just high right now?"
I'd say it's a little of both.
SIG: TAKE OFF EVERY 'CAPTAIN'!!
Suddenly, the predicted "end of the universe" models look a little dusty.
I record my sleeptalking
The speed of light is also the maximum speed of causation...if these "super structures" are outside the observable universe, how in the hell are they affecting anything within the observable universe? If they can exert causal influence on these galaxies, and the light from these galaxies has time to reach us... I could be wrong but I feel like someone, somewhere, is seriously contradicting themselves. Maybe those string theorists can tell us if its possible there's cosmic string tied between the galaxies and a giant tug boat in hyperspace...
What bugs me is that this "bubble" of the known universe really isn't a bubble at all, it's just the physical limit of our ability to observe; we have no means of determining the extent of this "bubble". Therefore, claiming that there could be "giant, massive structures much larger than anything in our own observable universe" just outside this bubble seems somewhat... convenient.
While I agree that this is one of the more interesting stories on slashdot in years, there are many aspects of contemporary cosmological theories that I remain highly skeptical of.
SIG: TAKE OFF EVERY 'CAPTAIN'!!
Don't tell anyone, but when contrasting known information against an infinite cosmos...the average scientist is basically as clueless as the rest of us.
-=Bang Bang=-
There are preprints of the two relevant papers on astro-ph.
More general version (ApJL)
http://xxx.lanl.gov/abs/0809.3734
More technical version (ApJ)
http://xxx.lanl.gov/abs/0809.3733
It's God
Spelling and Grammar errors have been added to this post for your enjoyment
I'd intended to add this to the summary, but forgot.
TFA has a very nice, if brief, explication on the "universe" vs. "observable universe". Too many people (science and science writing pros among them) make assertions about the former when they should specify the latter.
Go ahead and read it, it's only a space.com article (ie. very short).
"I may be synthetic, but I'm not stupid." -- Bishop 341-B
And there are aspects of many contemporary theories (and lesser recognized works) that are equally skeptical of, and orthogonal to, each other. I personally don't know enough GR to talk confidently about why this is not exciting, but if it does turn out to be exciting, expect some very well written and insightful roundups here:
www.cosmicvariance.com
Small note: I have found Sean Carrol's [and team] work on the internet to be some of the most accessible stuff available from brilliant minds in science today. Of course, every time you read something dumbed down mathematically (even if only slightly), you end up hating yourself for not spending the time instead on understanding the 3 years worth of adv.math courses you need to really grasp what is happening. But the upside is that you can spend 15 minutes reading some well written summary by people like these, and end up getting a fairly good idea of the issue at hand all the same. Kudos to science "bloggers" (esp world-leading academics) everywhere. You make the internet suck a lot less.
If we are observing far-away galaxies being affected by the stuff too far away for us to observe directly, maybe we are observing the stuff outside our bubble indirectly? This visibility can be transitive?
Also, maybe we can also "observe" the stuff outside our bubble via the effects of "spooky action at a distance"?
Fuck systemd. Fuck Redhat. Fuck Soylent, too. Wait, scratch the last one.
Ok, here's a question for you. The "observable universe" isn't just the observable universe for us, it is that for the whole universe. Nowhere in the universe that is observable to us can you go and observe beyond 13.7 billion light years. We're all in the same boat. However, in the area of the universe that is being affected by this phenomena, they must be able to observe what is causing it. Elsewise, it couldn't be affecting them. There is nothing that can affect me that is unobservable. You can't be so far away that you are beyond my observation range and yet still affect me, unless you are exerting FTL influence on me. So, if this is truly an influence from beyond the visible universe, then that would seem to me to imply FTL.
Your reasoning is trapped by trying to imagine the universe as some defined boundary expanding. It's the same reasoning that images the Big Bang as an explosion in space.
The bang wasn't an explosion in spacetime, it was an explosion of spacetime. The expansion of space just means that the metric which measures distance between two points that stay at the same location changes. As time passes, two points which stay at the same location on some hypothetical reference grid will first measure one foot apart, then two, then five, etc. They aren't going anywhere, they're being carried along on space itself.
"Also, maybe we can also "observe" the stuff outside our bubble via the effects of "spooky action at a distance"?"
Well, then when we 'observe' this stuff, WE will have on our conscience whether the cat is dead or alive. :-)
But we still may never find out which one; which bubble^Wbox was/is in?
All joking aside, this is very interesting data to work with.
I can imagine a lot of theories to change/be scrapped/ be rewritten here in the near future.
I am really excited about this! (but somewhat befuddled-[I am not a physicist, much less an astrophysicist!]Astrophysics is a serious hobby for me) I hope some good info comes with further research.
That should open new 'doorways' and expand our understanding.
I don't think I can imagine all of the ramifications of this, but it strikes me as: 'Holy Cow, Batman...that cow lit her fart and flew over the moon!!!'
No doubt, this is the most exciting thing to happen with astrophysics (for me) in the past several years. The questions are ENDLESS!!!!!
Who knows 'what doors will open' for us, and the potential to find out what possible uses could arise from this.
P.S. I wish I knew enough to actually correctly answer your questions, but this news seems to sprout far more questions than can be accurately answered at this time.
Oh, and BTW, my head asplodes!!
Down With Slashdot BETA!!! I've been around the corner and seen the oliphant; you can only abuse me from your perspecti
Seriously guys, the place is a red-taped bureaucracy waste. They're too busy running background checks on people in non-sensitive jobs to do research.
This just screams, "I got fired from my NASA cleaning job for using meth".
Let's start with a recap of some statements that are true under current physical theories: (1) space itself is expanding (Hubble Expansion); (2) early in the history of the universe, the expansion of space was faster than the speed of light (Inflationary Big Bang theory); (3) nothing can exceed the speed of light, not even gravity or information (Special and General Relativity); and (4) we are confined our "observable universe": a bubble 92 billion light-years in diameter (General Relativity plus Inflationary Big Bang theory — 13.7 billion light-years, plus inflation, plus 13.7 billion years of Hubble expansion).
Given these facts, neither gravity nor information from outside our observable universe can enter it.
Sure, parts of what we currently consider the observable universe might, in their own relativistic timeline, be "currently" experiencing a gravitational tug from parts of the universe that we can't currently observe, even in principle. However, if that is true, then either (a) such observable places will exit our field of observation before we observe that gravitational tug (i.e. the universe will expand faster than light), or (b) such unobservable places exerting a gravitational tug will enter our field of observation before we see the tug on things we can currently see (i.e. the universe will expand slower than light).
There's no way that information could take a roundabout path to us and arrive faster than information traveling in a straight line (or, more correctly in GR, a geodesic). Think about it: if light/gravity/information cannot travel directly to us, because the direct path is too long and too slow, how could it travel indirectly to us? The indirect path is, by definition, longer and slower than the direct path.
I suppose that, if a large mass was once observable but now is not (i.e. it tugged on some galaxies, then inflation happened), the theory in the article might make a certain amount of sense. But the timescale of inflation (fractions of a second after the Big Bang) doesn't really leave a lot of time for that to happen. It sounds much more plausible to my ears that either (a) there is a previously-undiscovered conglomeration of dark matter in that direction, but it still lies within our observable bubble; or (b) the galaxies in question are at high velocity but no longer accelerating, indicating leftover momentum from an ejection, collision, or some other high-energy event in the early universe.
OTOH, I'm no physicist, so maybe I'm missing something, or maybe the actual theory being promoted makes more sense than Space.com's rather awful writeup.
Range Voting: preference intensity matters
by definition, expansion of space is Imperial, not metric.
MP3 Search Engine
the word "observable". AFAIUI, in this case it means directly observable. Given an expanding universe -- since nothing can travel faster than light (and c is finite) and the universe has a finite age there is a limit to how far you can "see" in any direction from any given vantage point (see "horizon problem"). However, you might still be able to see an object at the very edge of "your" observable universe being influenced by something beyond your particular observation horizon -- that is, you can tell that it is being influenced by something and that it's not being influenced by something inside horizon. So essentially very talking about indirect observation here.
HAND.
we have no means of determining the extent of this "bubble".
Effectively, we can: we can't see past the surface of last scattering where the cosmic microwave background radiation originates.
Therefore, claiming that there could be "giant, massive structures much larger than anything in our own observable universe" just outside this bubble seems somewhat... convenient.
Well, the chaotic inflationary theory has long predicted such structures should exist at all scales outside the observable universe. Anyway, we see matter near the boundary of the observable universe. There are almost certainly large structures outside the boundary too. We see some of that matter moving in a way it ordinarily wouldn't according to the usual cosmological expansion. It's not that big a leap to hypothesize that it's being pulled by something on the other side of what we can observe.
It's not a small leap, either — obviously it's hard to compile statistics on how these boundary clusters are moving, and thereby infer anything really solid about possible unseen gravitational sources. But it's not completely ad hoc. The explanation involves something that has been suggested by theory in the past for independent reasons, and observationally there don't appear to be any nearby sources of matter that could explain why the motion is so far from the Hubble flow. I suppose you could postulate a bunch of dark matter right near the boundary, but since (as you say) the cosmological horizon isn't some special physical place, but is just the region beyond which light hasn't reached us, that would be weird.
This should be taken with the usual grain of salt: it's a brand new paper and in a year or two could potentially be explained in a much more mundane way. I'd personally give it less than a 50% chance of being right. But it's not a priori ridiculous either. As another poster said, I hope that Cosmic Variance covers the result ... a real expert second opinion would be valuable.
Therefore, claiming that there could be "giant, massive structures much larger than anything in our own observable universe" just outside this bubble seems somewhat... convenient.
"giant, massive structures much larger than anything in our own observable universe" is the new "here be dragons".
You just got troll'd!
Fuck Off Matter
You know, I've been wondering for a long time just exactly what is the secret ingredient in a tall, cool glass of Shut the Fuck Up.
If libertarians are so opposed to effective government, why don't they all move to Somalia?
First, the region that these clusters are supposedly moving towards are pretty close to being in line with the heart of the Milky Way. What this means is that the attractor object may simply be obscured by our own galaxy.
It's not just the lack of an attractor object, it's the unusual velocities.
Second, the motion is not unusually large for superclusters.
They argue otherwise: "If produced by gravitational instability within the concordance LambdaCDM model, the motion would require the local Universe out to ~ 300h^1 Mpc to be atypical at the level of many standard deviations of the model", and argue that even a 100 km/sec motion due to local gravitation alone would be excluded by observations. I confess that I don't know enough cosmology to understand why. Either you expect smaller motions in the earlier universe or else there are additional constraints at work (they mention having to explain why the dipole is approximately constant with depth). I'd have to do more background reading to understand what's going on here, but the point is that they say they have reason to believe that the motion is unusually large.
What really bothers me here is the claim that these bodies are still experiencing forces from the long departed rest of the universe.
I don't think they are. From my reading of the paper, it sounds like this motion is left over from the inflationary phase.
What is happening is that the underlying geometry of space is expanding. Best estimate of the rate of expansion is something like 72 kilometres per second per megaparsec. So if two objects are one million parsecs apart (that's 3.26 million lightyears), then one second later they'll be one million parsecs and 72 kilometres apart.
In addition, objects in that space are free to move within it, and so if they are subject to mechanical forces they'll follow those forces just as normal. So atoms and apples are held together by their internal electromagnetism, and the Solar System by the gravitational attraction between the Sun and the planets. Objects like these drift along with cosmic expansion, but do not themselves expand.
It's only on the cosmic scale that the universal expansion becomes significant. Remember, we're talking kilometres per second per megaparsec - on such a huge scale, forces pulling objects together drop to tiny levels, while the expansion of space becomes greater and greater. The Andromeda Galaxy is only two-thirds of a megaparsec away, and so the cosmic expansion is small compared to the local motion of the galaxies - indeed, we're on a collision course with Andromeda. The largest known object in the Universe, the Great Wall, is maybe a hundred times more distant; on this scale, the cosmic expansion becomes significant. It's really the distance between galactic clusters and superclusters which is being expanded.
Real Daleks don't climb stairs - they level the building.