"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.'"

Comments

Gravity Leech

[CuteSteveJobs]

> 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 plot thickens

[sleeponthemic]

Suddenly, the predicted "end of the universe" models look a little dusty.

ermmm...

[dexmachina]

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...

Re:ermmm...

[aussie_a]

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 have we never seen it then? Well perhaps as everything in the visible universe expands, it also pushes back the stuff outside the visible universe.

We can know one thing about this stuff though. It doesn't contain any stars for the simple reason that we would have seen the light travel from it.

NOW this answers a question I've had for a very long time, which is "why did the big bang happen?" which would be "because the matter in the universe formed together tight enough and in such a way as to create the big bang" which means there could have been other big bangs in the universe which means we might one day (millenia from now) see light from another big bang.

However it does raise yet another question "what created all the stuff that exists outside the visible universe?" and before someone says god I then ask "What created god?"

Re:Since looking farther = further in time

[Big Nothing]

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.

William James Sidis

[solferino]

Reminds me of some writing by William James Sidis, published in 1925.

Our previous consideration on the production of radiant energy from the stars indicates that such production of radiant energy is only possible where the second law of thermodynamics is followed, that is, in a positive section of the universe. In a negative section of the universe the reverse process must take place; namely, space is full of radiant energy, presumably produced in the positive section of space, and the stars use this radiant energy to build up a higher level of heat. All radiant energy in that section of space would tend to be absorbed by the stars, which would thus constitute perfectly black bodies; and very little radiant energy would be produced in that section of space, but would mostly come from beyond the boundary surface. What little radiant energy would be produced in the negative section of space would be pseudo-teleologically directed only towards stars which have enough activity to absorb it, and no radiant energy, or almost none, would actually leave the negative section of space. The peculiarity of the boundary surface between the positive and negative sections of space, then, is, that practically all light that crosses it, crosses it in one direction, namely, from the positive side to the negative side. If we were on the positive side, as seems to be the case, then we could not see beyond such surface, though we might easily have gravitational or other evidence of bodies existing beyond that surface.

Furthermore, just as in the positive section of space, light is given out uniformly in all directions, so, in the negative section, light must be absorbed by a star equally from all directions. Thus, to any star in the negative section, light must come in about the same amount from all directions; and, since most of this light comes from the positive sections, it follows that the negative sections must be completely surrounded by positive sections and must therefore be finite in all directions. By reversing this (since we have seen that all physical laws are reversible), it follows that any positive section must also be finite in all directions, and be completely surrounded by negative sections. We thus find the universe to be made up of a number of what we may call bricks, alternately positive and negative, all of approximately the same volume; a sort of three-dimensional checkerboard, the positive spaces counting as white (giving out light), and the negative spaces as black (absorbing light).

Thus what we see is simply the white space that we are in. The surrounding black spaces are invisible, and in addition, absorb the light from the white spaces beyond, so that even those cannot be seen, and, if we judge from the distribution of light in the sky, we get an idea merely of the size and shape of our special white space.

William James Sidis, The Animate and the Inanimate

Gravity

[Anonymous Coward]

Excuse my ignorance but isn't the speed of gravity about the same as the speed of light?

They claim they can't "see" whats causing this because light from there hasn't reached us yet, yet the gravity waves from the "dark object" have reached the region of space where this "dark flow" is. So can't they calculate when we should be seeing the first light from that "dark object"?

If it even emits light... IMO it seems to be a farflung theory, still intresting though.

Does this imply FTL?

[Excelcia]

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.

Re:Does this imply FTL?

[49152]

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:Since looking farther = further in time

[Antique Geekmeister]

No, our universe could be a black hole. In that case, the boundary or "bubble" has a much stronger meaning, and it could make more sense to talk about material 'outside' our universe.

Re:Preprint Versions of the Papers

[IHateEverybody]

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:I'm no astronomer

[Anonymous Coward]

Is it possible that the Big Fucking Thing is in fact a humongously gigantic Dyson sphere?

In many fictional accounts, the Dyson sphere concept is most often interpreted as an artificial hollow sphere of matter around a star .. Such a shell would have no net gravitational interaction with its englobed sun (see Shell theorem), and could drift in relation to the central star. If such movements went uncorrected, they could eventually result in a collision between the sphere and the star - most likely with disastrous results.

Replace 'star' and 'sun' with 'observable universe bubble' and the science is just astounding!

Re:Great!

[AlecC]

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.

Doesn't make much sense to me

[CTachyon]

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.

Re:Since looking farther = further in time

[AngelofDeath-02]

To my knowledge, this isn't possible because nothing can travel faster than the speed of light.

To expand on that, Information cannot travel faster than the speed of light either, which means neither can gravitational forces, or ... well, anything else we're aware of.

Unless of course, you're implying that our limit of perception isn't the limit of the speed of light, but something else.

Re:Silly trend in science

[budgenator]

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.

Re:Flimflammery

[Ambitwistor]

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:Preprint Versions of the Papers

[Ambitwistor]

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: the authors are hoping that matter outside the other side of the observable universe has left its gravitational imprint on matter near the boundary.

Re:I think you're misinterpreting...

[Ambitwistor]

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.

God's address

[idlehanz]

Now we know where He lives.

Re:Great!

[AlecC]

To which all I can say is http://www.eastoftheweb.com/short-stories/UBooks/TheyMade.shtml