"Dark Flow" Outside Observable Universe 583
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.'"
Great! (Score:4, Funny)
Re:Great! (Score:5, Funny)
Re: (Score:2, Funny)
Medicine giveth and science taketh away.
Re:Great! (Score:5, Insightful)
i think it's kinda cool. the idea that there are even more massive structures out there than what's in our observable universe is really quite mind-boggling. but without stars and galaxies i wonder what kind of emergent structures or phenomena could exist beyond our observable bubble.
i'm guessing it's probably not possible for biological life to form in such a radically different environment, but then again maybe i just lack the imagination to conceive of such possibilities. it seems like within our observable universe for any biological life to evolve it must follow certain patterns dictated by the laws of physics/chemistry. but if space-time in these regions is so different from our observable universe then who knows? our level of consciousness compared to what exists out there might be like comparing an amoeba with a blue whale. even the time scales experienced by other life forms could be drastically different from ours. entire civilizations could spring forth and flicker out of existence all in the blink of an eye.
but since we can't even observe what is out there maybe this is all pointless speculation.
Re: (Score:3, Funny)
As pointless as observing something outside the observable universe — thus, there is no need to worry.
CC.
Re:Great! (Score:4, Interesting)
I would agree that if there is life, it is certainly not life as we know it.
But IMO the fundamental thing needed for life is an energy flow. Possibly you also need a state of matter corresponding to what we regard as solid i.e. one in which components tend to stay put without needing to expend energy. Given those two components, and enough time, I think that something that we could tentatively call life will emerge, occasionally, anywhere. How long it will take to get past the bacterial level is a much more complex question.
Re:Great! (Score:5, Insightful)
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... bacteria that thrives in nuclear reactors and in boiling water.
Most extremophiles are archaea [wikipedia.org] rather than bacteria.
Re: (Score:3, Interesting)
To which all I can say is http://www.eastoftheweb.com/short-stories/UBooks/TheyMade.shtml [eastoftheweb.com]
Re:Great! (Score:5, Insightful)
It's contradictory anyway. If we're seeing something influenced by it, then we ARE observing it. That's what observation MEAN.
If you're "watching" something, you're really interpreting electrical signals generated by your retina in response to chemical reactions triggered by photons, nothing "direct" about it whatsoever.
So saying we're seeing something being influenced by something outside the observable universe is nonsense.
I think you're misinterpreting... (Score:5, Informative)
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.
Re:I think you're misinterpreting... (Score:4, Informative)
That is wrong I am afraid.
Nothing and that includes information can travel above the speed of light neither directly nor indirectly.
Yes, it it possible for something at the edge of our observable universe to be affected by something outside our observable universe right now.
But we do not (and cannot) observe what happens at the edge right now, but rather when light left that place heading in our direction a very long time ago.
So in effect we are seeing what happened at the edge in the past. This also means that the light from anything capable of affecting that part of the universe at that time would also by now had time to reach us and so we would be able to see it.
The summary is (as usual) a bit misleading.
What the article is suggesting is not that something outside the observable universe is affecting something else inside it right now and that we can see the effect but not the cause, but rather that something influenced a part of the universe around the time of the great inflation shortly after the big bang.
At that time those parts of the universe would have been close enough together that they could have affected each other. The inflation stage which was an extremely fast expansion of time and space itself has since moved some parts (in fact probably most of it) outside our observable universe so we cannot see this part.
What they see is something having a great speed due to an earlier influence by something we cannot see now, not that it is still being accelerated because that would have been a violation of the speed of light.
I hope I am not to unclear on this but English is not my first language so I find it a bit hard to explain any clearer.
Re: (Score:3, Informative)
Your analogy is flawed, since speed of light does not play a role in it, while it does with this observable-object-influenced-by-object-outside-our-lightcone situation. For the information about the unobservable object to be able to travel to us, it must be within our lightcone, otherwise it would entail information travelling faster than light.
Re:I think you're misinterpreting... (Score:5, Informative)
Yes, it would. Gravity works at lightspeed also, so any gravitic effect on an observable object must be detectable at the observer, making the influencing object "observable".
Likewise, any other effect that we know of, all of which are limited to lightspeed. The only way that something outside the observable universe could affect something inside the observable universe and be seen by something else inside the observable universe is if the laws of physics that we know and love are basically a steaming pile of horse apples.
Re: (Score:3, Insightful)
Well, let's set aside for a moment the fact that we have not yet measured the speed of gravity accurately enough to tell if it is equal, above, or below the speed of light. We'll just assume it's equal.
Now that I've given it some post coffee thought, you are, of course, correct. My error was that I was considering the light con
Re: (Score:3, Interesting)
If the speed of gravity is equal to the speed of light, no measurement no matter how precise will ever tell us if the former is equal, above, or below the latter. The error bars will always include above c and below c, even if they're incredibly small.
Our indirect measurements indicate that the speed of gravity is the speed of light, to within about 1% accuracy.
Re: (Score:3, Informative)
According to our current understanding of physics, the situation you describe can't actually occur. It is impossible for two pieces of matter to be moving apart at c. If we were
Re:I think you're misinterpreting... (Score:4, Informative)
Because gravity works at the speed of light.
If gravity from B left there at some time in the past, and reached A, it then continued past A toward O.
Light from A went from A to O.
Light and gravity move at the same speed, so, the light from A reaches us at the same time as the gravity from B.
Therefore, B is within the "observable universe".
In order for the above to not work, some part of the process above must include "faster than light". Which, so far as current physics is concerned, isn't part of the picture.
Stupid stalker (Score:3, Informative)
Is someone following me around modding my stuff overrated? I wouldn't have minded if they had actually modded the factual parent post to which I referred up, or the incorrect ancestor +5 post down. As it is, they're just hiding the truth.
CrimsonAvenger, modded at 2 (the parent in my MOD PARENT UP comment), has it completely right. Warrax, modded at 5 Informative, has it completely wrong.
"Information can't travel faster than the speed of light" means just what it says. The impossibility of detecting chan
Re:I think you're misinterpreting... (Score:4, Informative)
Both of those are assumptions. If they were true, there wouldn't be a logical explaination for tachyons.
Who cares if there's a logical explanation for tachyons, since we don't have evidence for any?
Anyway, even if tachyons existed you'd never actually observe anything traveling faster than light; see this FAQ [ucr.edu].
In other dimensions things DO move faster then light.
Says who? In any relativistic quantum field theory or string theory, c is the limit in any dimension.
Furthermore, the speed of gravity is much greater then c.
van Flandern's website is a bunch of crackpot nonsense. He was pretty notorious on Usenet for years. He misapplies perturbation theory; if you apply his same arguments to electromagnetism, you "conclude" that light travels faster than light too (see here [arxiv.org]). In fact, you can rigorously prove in general relativity that the speed of gravity cannot exceed c (see here [arxiv.org], assuming that the gravitational waves aren't produced by weird things like negative mass). The 1993 Nobel prize in physics was awarded, in part, for an observational determination of the speed of gravity. (You can deduce it by the rate at which gravitational energy is radiated by orbiting bodies.) The measurements indicate that the speed of gravity is c, to within a few percent accuracy.
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Re:Great! (Score:4, Insightful)
Humans are insignificant for the terms of the universe, but we at least strive to understand it.
We haven't yet fully understood the universe, and even if we do it's so large that it's hard to fathom the span of it.
And did the universe really exist before the big bang or was it created by the big bang? How can one prove something that is hypothetical if we don't have something to measure it against?
Anyway - it is possible that what attracts matter is nothing more than an inert part of matter - or more specific a black hole that currently is invisible because it has consumed all matter near itself a long time ago.
The Big Bang wasn't a "perfect" explosion, and if it had been we wouldn't have had the distribution of galaxies that we have - it would have been a cloud of gas. And since we haven't had a perfect explosion it is possible that the black hole was created at a very early stage of our universe.
But who knows in reality?
I'm no astronomer (Score:5, Funny)
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.
Re: (Score:3, Funny)
Re: (Score:3, Funny)
Yes, a big bagless vacuum cleaner. In my theory I'll outline to time of the apocalypse, or as I call it, Dyson time.
Flimflammery (Score:5, Insightful)
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.
Re: (Score:2, Insightful)
'Can be understood by an interested layman' is definitely the wrong metric for measuring scientific advancement.
That being said, the aether & dark matter/energy analogy is something I have been thinking about as well. It _does_ feel like a crutch for current theories. Or someone figures out where this stuff hides in the next 24 hours. Who knows :)
Re:Flimflammery (Score:5, Interesting)
But I look forward to anything that seems to pin down the concept of 'dark matter'.
This new theory isn't an alternative to dark matter.
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'.
You believe neutrinos exist, right? How hard is it to believe that there's something else like a neutrino out there, but heavier?
Dark matter-like particles have been predicted for decades. Within the Standard Model, there's the axion which is supposed to solve the strong CP problem in QCD. In the supersymmetric extension of the Standard Model, there is the neutralino. In fact, most theories beyond the Standard Model naturally require some heavy scalar particle which could be a dark matter candidate.
Modifying gravity doesn't appear to consistently explain all the gravitational behavior we observe. The other alternative is modifying the source of gravity, i.e. there's something out there we can't see for some reason. And that does account for the gravitational behavior we observe.
Re: (Score:3, Insightful)
Modifying gravity doesn't appear to consistently explain all the gravitational behavior we observe.
In fact, it actually *can't*. Once again, I cite the Bullet Cluster [wikipedia.org] and MACS J0025 [newswise.com] results. As this researcher [umd.edu] put it, "Nevertheless, the most straightforward interpretation is that there is indeed unseen mass.", and "It does add something new, and that is that whatever that mass is, it is not collisional." Incidentally, his position is that CDM is still not the answer, and that the real solution is a combi
Smelloscope (Score:4, Funny)
Gravity Leech (Score:5, Interesting)
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/ [pbs.org]
In other news... (Score:5, Funny)
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.
Hmmmmm.... (Score:2, Funny)
I have a bad feeling about this.
The plot thickens (Score:4, Interesting)
bah (Score:2, Insightful)
The universe is mmuch more complex than the average scientist lets on.
Re:bah (Score:5, Insightful)
Re: (Score:3, Insightful)
Absolutely wrong. [...] A in philosophy, F in science.
And PhD stands for Doctor of Philosophy. Science is examined at the philosophical level by those at the top, and they recognize that
( scientist~=layman <= Total Possible Knowledge )
if they earned their Doctorates the hard way.
Re: (Score:3, Insightful)
Decades ago, university courses tying beliefs to science were given - I seem to recall one relating Zen Buddhism to physics.
I think it's altruistic to believe that science is examined at the philosophical level by those at the top unless you could be more specific. I hobnob with a large number of Ph.D.s, majority physicists, definitely from best schools, definitely came up the hard way. Of those, and admittedly speaking from my experiences - but maintaining that is direct experience - the ones that map ph
Entropy (Score:2)
ermmm... (Score:4, Interesting)
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Re:ermmm... (Score:4, Insightful)
Re:ermmm... (Score:5, Insightful)
Re: (Score:3, Insightful)
Yep you're right, but *I think* they're talking about a different horizon to the one you're thinking of (the summary doesn't make this clear).
The furthest back we can see is the CMBR, due to the Universe being opaque any earlier on. This opacity creates a horizon at a slightly shorter distance than the horizon you would get due to the fact that light/changes in gravity fields propagate at c.
The abstract (linked below) mentions that they suspect it is gravitational influences from beyond the CMBR barrier (bu
Re:ermmm... (Score:4, Insightful)
Re:ermmm... (Score:4, Informative)
Yes but by the time those other ships were able to report to you the ships that they see that you can't, you can see those other ships, too.
Re: (Score:3, Interesting)
My understanding (and I'm most likely 100% wrong) is that imagine the Big Bang didn't create everything in the universe. Instead it just created everything we can see. There exists stuff beyond our eyesight that's existed since before the big bang. We can't see it because light from stars has yet to travel to it, bounce off it and then travel back to us.
Like everything else in the universe, this invisible matter could still have mass which exerts a force much like stuff does within the visible universe.
Why
Re:ermmm... (Score:5, Informative)
Imagine points A-B-C to be gravitationally bound. Because of metric expansion, space between A-B and B-C expands. This can cause A to move away from C at larger than lightspeed. Since space between B-C only expanded half of A--C, B will be withing light distance from C and thus visible by observers on C. Light from A can reach B, but it will never reach C. By the time it would, space between B and C will have expanded so much that observers from C will no longer see B.
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Think of it like this: they *expect* to see a certain red-shift from something at 6 billion light-years:
William James Sidis (Score:3, Interesting)
Reminds me of some writing by William James Sidis [wikipedia.org], published in 1925.
William James Sidis, The Animate and the Inanimate [sidis.net]
Preprint Versions of the Papers (Score:5, Informative)
More general version (ApJL)
http://xxx.lanl.gov/abs/0809.3734 [lanl.gov]
More technical version (ApJ)
http://xxx.lanl.gov/abs/0809.3733 [lanl.gov]
Re:Preprint Versions of the Papers (Score:4, Interesting)
Either I'm confused or the write up and author of the space.com article are just confusing. Granted, I'm not a physicist but it seems to me that the papers are saying something very different from the write up and the article say. Instead of some mysterious new force from outside the universe, the two papers are based on an analysis of the Cold Dark Matter theory which has been around for some time.
The article is also confusing when it talks about the "known universe." The Inflationary Theory of the origin of the universe says that early on in its existence, the universe underwent a drastically fast expansion. When physicists talk about the "observable universe," they are referring to the idea that Inflation caused parts of the universe to expand so rapidly that their light cannot reach us in the age of the universe. Now those regions are still part of our universe, we just can't see them because they are "over the horizon" so to speak like a ship on the ocean which disappears from view once it gets so far away from shore that the Earth curves away from our field of vision.
In fact this last point appears to be the most interesting part of the papers if I understand them correctly. The papers suggest that it is possible to peak over the horizon and get an idea of what the universe looks like beyond the limits of what we can see with our telescopes. Like the mast of a ship peaking out from the edge of the horizon, clusters of galaxies that we could not see otherwise can be detected by carefully measuring the effects of their gravity on regions of the universe that we can see.
Re: (Score:3, Interesting)
Instead of some mysterious new force from outside the universe, the two papers are based on an analysis of the Cold Dark Matter theory which has been around for some time.
Read the papers again. The first paper doesn't mention dark matter at all: it's talking about "pre-inflationary remnants" outside our cosmological horizon (observable universe). The second paper is talking about the same thing, although it does mention dark matter (to note that other than the peculiar flow, the matter behaves according to the CDM model).
Your description of the observable universe is right, but I don't think it conflicts with what the article says. You're also right about the last point:
weird news = good news (Score:2)
As opposed to things like the LHC (which is cool, granted), where the best you can hope for is that it finds something different than what they expect by Standard Theory, the field of astrophysics is almost scary in the weirdne
It's Obvious (Score:5, Funny)
Wow, lets just add another hypothical entity (Score:2, Insightful)
What NASA really meant to say was, "Shit, we just found something else that does not fit our current model of the universe. Lets just make some stuff up and call it a new discovery"
Maybe this time people will wake up.....probably not.
http://bigbangneverhappened.org/ [bigbangneverhappened.org]
Re: (Score:2)
Promote space research, privatize NASA.
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.
Re:Wow, lets just add another hypothical entity (Score:5, Funny)
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".
Great Attractor (Score:2)
The Great Attractor [wikipedia.org] is another mistery. Entire galaxies are pulled toward it where there is nothing just empty space.
Passing the boundary (Score:2)
Didn't Star Trek and Babylon 5 deal with this already?
I forgot to say..... (Score:5, Informative)
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).
It could be ANYTHING (Score:3, Insightful)
To paraphrase David Hume: There is no reason to believe that the laws of physics have always been what they are today at all points in space and at all points in time. While it is well within reason, and quite likely, that the Universe follows neat patterns quite specifically, when one runs into really odd data that doesn't fit into your tidy boxes it might be time to rethink things. Dark matter/flow/energy or whatever the new buzzwords scientists come up with are stop gap measures meant to really say, "we haven't the foggiest idea what's going on, but it doesn't quite add up".
Does this imply FTL? (Score:3, Interesting)
Re:Does this imply FTL? (Score:4, Interesting)
True.
However the radius of the observable universe increases with time.
The time it took for light to travel from these distant galaxies should equal the additional time it will take for light from the cause of the movement to travel from the galaxies to us.
This means that if we can see the action we should also be able to see the cause.
Information cannot travel faster than light neither directly nor indirectly.
The only explanation I can see is that this speed (or flow) was caused by a gravitational tug that happened around the time of inflation.
But if this is the case we should not register any current (or rather at the time we see now light departed from the galaxies toward us) acceleration of these distant galaxies apart from what can be expected from the general expansion of the universe.
Re: (Score:3, Informative)
As someone else pointed out this is exactly what the article is talking about.
Something influenced these galaxies around the time of inflation to give them a very high speed. Since then inflation has moved that something outside our observable universe (or lightcone if you will).
But what I was answering to was the claim that someone somehow was able to see something being influenced by something else outside our observable universe. I fail to see how this could be correct even considering inflation or the c
Super.... (Score:3, Insightful)
Doesn't make much sense to me (Score:5, Interesting)
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 [wikipedia.org] (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.
Re:Doesn't make much sense to me (Score:4, Informative)
You should read the abstracts of the articles, since it turns out you're right. From the abstract:
"This flow is difficult to explain by gravitational evolution within the framework of the concordance LCDM model and may be indicative of the tilt exerted across the entire current horizon by far-away pre-inflationary inhomogeneities."
They would, at least, find it less plausible to describe it with a huge mass of dark matter.
Re: (Score:3, Informative)
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.
Yes, that's the idea here: the distant galaxies are still experiencing left-over motion due to a tug from matter long ago, which has by now expanded beyond our ability to see. This is a feature of the accelerating expansion due to inflation. Objects which were once within our causal horizon can be far, far away from it now. All we see is what effects remain from when they were near us.
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.
There was time for objects to gravitationally influence each other, if they were very close. Then they got blown far ap
Re: (Score:2)
yeah, either that, or the fat of the basement dwellers.
Re:Since looking farther = further in time (Score:5, Informative)
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!
Are we alone? (Score:4, Funny)
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!
Re:Are we alone? (Score:5, Funny)
Re:Since looking farther = further in time (Score:5, Interesting)
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.
Re:Since looking farther = further in time (Score:5, Informative)
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.
Re:Since looking farther = further in time (Score:4, Insightful)
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"?
Re:Since looking farther = further in time (Score:4, Informative)
"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!!
Re: (Score:3, Interesting)
Re:Since looking farther = further in time (Score:5, Informative)
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.
Here Be Dragons (Score:4, Insightful)
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".
Re:Since looking farther = further in time (Score:4, Funny)
by definition, expansion of space is Imperial, not metric.
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Turtles all the way down...clearly.
Gerry
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I had heard from LiveScience that someone had been speculating our universe was shaped like a higher dimensional torus. Isn't there a type of hyperdimensional torus with a very small hole that kind of looks like a cushion (the middle one [wikimedia.org])? Maybe that could cause material to flow to a central point while the torus expands.
I don't understand this speculation -- is there any reason to believe that matter is flowing to the center of the universe while it expands? TFA talks about unexplained forces from the region of space beyond the reach of light from the big bang, i.e. the unobservable universe. Although it says space/time probably doesn't work the same there, there's no reason to believe in exotic higher-dimensional structures for the universe unless there's a good reason and empirical evidence to do so.
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It isn't rocket surgery, it is logic. 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?
Ummm....I would say the latter (bold emphasis mine). Then again, it is very easy to confuse rocket surgery and logic.
Re:The Universe goes on Forever (Score:5, Funny)
" 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.
Re:The Universe goes on Forever (Score:5, Insightful)
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.
Re: (Score:3, Insightful)
Would you mind explaining why? The big bang theory does not in any way suggest that we are 'special', and it is not in contradiction with any observations as far as I know.
Re:which space? between galaxies or atoms? (Score:5, Informative)
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.
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Dark + Science = We have no clue what's going on please fund us
Disclosure: I'm a heavy advocate of funding the sciences and a scientist myself. But seriously guys, just admit it if you don't have a clue;)
To put it from my freshman chem course:
If someone talks about:
Yuan-Teller distortion - 50% chance bullshit
Second-Order Yuan-Teller distortion - 100% chance bullshit
Pseudo-Second-Order Yuan-Teller distortion - You are being mocked.
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fail.
Re: (Score:3, Interesting)
I think what is happening is the universe as we know it is a blackhole, basically light gets redshifted to a frequency of 0 eventually, that is an event horizon and has a radius of Hubble's constant / c; the effect is caused structures that are inside the galaxies observable universe, they are 6 Billion light years away, so they can see 6 Billion Light years farther than we can, but are outside our observable universe. Because it is unobservable it is dark to us.
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[/KeanuReeves]
Re: (Score:3, Informative)
Sounds like you don't quite understand the concept of a light cone [wikipedia.org]... Let me simplify your example and see if I understand you:
*Galaxy A is within the Milky Way's observable universe.
*Galaxy B is outside the Milky Way's observable universe, but it's within Galaxy A's observable univ
Re:Punk science (Score:5, Funny)
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.
Re:insufficient data (Score:4, Insightful)
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.
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Once I did that 3 times in a row
You're a WITCH!
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There are huge comment threads here arguing over the same question.
The answer is that their gravitational fields do not now have any effect on our observable universe. They used to. Pre-inflation, they could gravitationally influence us, and we could see them too. (Or we could, except for the fact that the universe was opaque back then.) Now we can't, because they expanded too far away.