Dark Flow

[neufer]

The high recessional velocities we infer from redshift measurements caused primarily by relativistic time dilation:

That isn't my understanding. When the photons we observe as the CMB were emitted, their sources had a low velocity with respect to our location. In the past 13+ billion years, the Universe between us has expanded, which has increased the wavelength of these photons while they were in flight. This redshift is the product of cosmological redshift, not relativistic redshift (that's my interpretation, anyway).

I think this is basically a semantics difference.

By virtually stationary I am referring to the overall translation motion not the expansion motion.
In other words, the (presumably) 0.002c translation motion vector of the CBR has virtually no effect on its 0.9999983c expansion motion vector.

I didn't know there were any measurements or estimates for translational motion of the CMB. Are you talking about what we'd see perpendicular to our apparent local motion? If so, there's is no need to invoke relativistic effects to explain the lack of apparent motion; we are simply moving too slowly with respect to the distance. We can't even see translational motion in the nearest galaxies, let alone things at cosmological distances.

Rightly or wrongly, I am extrapolating from the observed "dark flow" to the entire visible universe. I don't see how a perturbation from outside of the visible universe can selectively influence portions of the visible universe without affecting it all pretty much the same.

Our own motion vis-a-vis the bath of microwave radiation in which we are embedded is explicitly determined by the increase in CBMR radiation in the direction we are going. A large portion of that motion appears to be due to the "overall motion vector of the universe" vis-a-vis that same bath of microwave radiation which is slowly teased out using the kinematic Sunyaev-Zel'dovich effect.

At least, that's how I am interpreting it.

Not me. I don't think there is any real concept of the overall motion of the Universe. All we can see is our own motion with respect to the CMB, which doesn't seem to have anything to do with the Universe as a whole, just our little observable bubble.

So you would restrict the observed "dark flow" to "just our little observable bubble"?

[neufer]

Any body remember back in the days when the end of the known Universe was the outer edges of our milky way?

There's nobody alive who remembers that far back.

Have you checked with our Resident Geezer: orin stepanek?

[alter-ego]

''Kashlinsky speculates that the dark flow extends "all the way across the visible universe," or about 47 billion light-years, which would fit with the notion that the clusters are being pulled by matter that lies beyond known horizons''.

Some clarification here.
First, the "Visible Universe" is limited to ~13.7Gly. However the co-moving distance is ~47Gly (radius). The co-moving distance is the size NOW of the Visible Universe. The Cosmic Microwave Background defines the photon boundary, if you will, of our "bubble". Even though the current size/diameter of the Universe calculated (Standard Model) to be ~95Gly, we cannot "see" anything beyond 13.7Gly. Also, the Dark Flow region has been identified out to ~2.5Gly, NOT the whole visible universe. So there's a ways to go still.

Second, unless we have two "bubbles" colliding (this is just a comment to elude to a point, I don't believe any theory allows for this kind of multi-verse collision), anything "outside" our Visible Universe (i.e. BEFORE the Big Bang), is FOREVER outside our visible universe. HOWEVER, the idea of motion imparted to matter visible to us within our "bubble" IS possible. I think of it this way, and I think it was stated earlier, every location within our bubble, has it's own bubble, and visible horizon. A conglomeration of mass could be visible to another far-away location, and therefore with the light cone for that observer. So that observer can be affected, and we see that obersver, so therefore we see the gravitational effects on that observer.

With that said, given we can only see ~1% of all the energy (normal mass that's visible), I think more data is needed to rule out the source of this large-scale motion is NOT in our observable Universe. There's another 26% of matter out there (25 times more than visible matter) that we can only indirectly "see" by weak lensing surveys. Unfortunately, the best one to-date (Hubble data) does not cover the Dark Flow region, but it does extend the matter / Dark Energy model out to ~13Gly! This is a beatiful bit of work and suggests that there is no reason to expect any regions of VERY large, locally contained mass concentrations. A similar survey in the Dark Flow region would be illuminating.

So the idea of matter motion ebb and flow being driven by regions outside our visible Universe is possible without breaking and laws of physics. Just as Ort Cloud or Kuiper Belt Objects can be pertubed by passer-by objects and change their orbits about the Sun, our visible Universe is much the same.

[bystander]

Some clarification here.

First, the "Visible Universe" is limited to ~13.7Gly. However the co-moving distance is ~47Gly (radius). The co-moving distance is the size NOW of the Visible Universe. The Cosmic Microwave Background defines the photon boundary, if you will, of our "bubble". Even though the current size/diameter of the Universe calculated (Standard Model) to be ~95Gly, we cannot "see" anything beyond 13.7Gly. Also, the Dark Flow region has been identified out to ~2.5Gly, NOT the whole visible universe. So there's a ways to go still.

The age of the universe is 13.7 Gyrs, that is the absolute limit on the time light has had to reach us. This determines the size of the observable universe, which is 47.5 Gly in radius. As you noted, the CMBR defines the photon boundary, so the visible universe is somewhat smaller than the observable universe. This is not a limit on the size of the entire universe. As Chris has stated, every point in the universe is the center of it's observable universe, so what ever caused the perturbation could very easily be outside what is now our visible universe.

[astrolabe]

Hello alter-ego,

Second, unless we have two "bubbles" colliding (this is just a comment to elude to a point, I don't believe any theory allows for this kind of multi-verse collision), anything "outside" our Visible Universe (i.e. BEFORE the Big Bang),

I have a hard time thinking that anything outside the visible/observable Universe is "BEFORE the Big Bang".

[astrolabe]

Hello All,

Don't quite know what happened, somehow got logged as "Guest". I owe it to alter-ego to own up as the commentor in the previous post.

[alter-ego]

Hello alter-ego,

Second, unless we have two "bubbles" colliding (this is just a comment to elude to a point, I don't believe any theory allows for this kind of multi-verse collision), anything "outside" our Visible Universe (i.e. BEFORE the Big Bang),

I have a hard time thinking that anything outside the visible/observable Universe is "BEFORE the Big Bang".

Hi astrolabe,
No doubt I agree with you. That comment reflects my speculation, and my way of grasping bubble universes. You are right, from our perspective, talking about time before the Big Bang makes no sense. But if we try to discuss / allow different observable horizons and stuff outside these horizons, we must open up the concept of time being relative to the observer, that includes the possibility that each observer has his own Big Bang. Let's say we have two observers that have non-overlapping Observable Horizons. Each most likely will have a Big Bang - I know we do, so why not for another observer? For each observer, nothing exists before their Big Bang. All this falls apart when we define and absolute Big Bang for all observers and which happens at the same absolute time. I think this is reminiscent of historical evolution of astronomy - everything begins as a universe centered on us and our experiences. That is the natural thing to do. My statement is meant to suggest that the Big Bang is only unique to us.

Now, to me, this view seems to create "bubble" universes in terms of observable horizons existing in the same space-time environment, i.e. I don't think I'm talking brane theory here where 10 dimensions (?) are employed. Maybe in the concept I'm discussing, one might put all these observation bubbles into one "Super" Universe where we just accept there are regions we won't ever see, but if we could just get over there a few billion light years, we could see new stuff. For this kind of Super Universe to exist, it seems logical our visible would be "flat". I believe data supports a flat model to 2%, which means the "size" of the "entire Universe" would be "closed" at about 50 times bigger than what we see now, and as the curvature parameter => Zero, the Universe size potential => Infinity. This in my mind is at least consistent with independent (non-overlapping) "bubble" universes. The minute we consider "inflation" as real, and Dark Energy (or Gamma) that can apparently separate matter arbitrarily fast (matter is just along for the ride, no local velocity required!), then the idea of bubble universes becomes tenable.

I hope this discussion sheds some insight into my thoughts. I'm honestly not intending to spout garbage, but I know in trying to frame ideas simply, there is likely to be a lot of room for improvement.

[astrolabe]

Hello alter-ego

Thanks for your clarification. Once again I've been on a chess hiatus in an effort to refloat a chess opening which was in the hopper after an on-again-off-again success history. It's probably still in the hopper but an up-coming tournament may tell the story better. During my absence from this fine Forum I still managed to read every post carefully and yours have been intelligent to say the least. I referred to your comment sort of toungue-in-cheek as I was sure you didn't propose time before the BB. The bubble Universe idea is as large as the Universe itself and requires not a small amount of thought to organize ideas in the expediently sized framework of your post. Well done. I'm humbled to have encountered you as the first member of this Forum in my return.

[Chris Peterson]

This redshift is the product of cosmological redshift, not relativistic redshift (that's my interpretation, anyway).

I think this is basically a semantics difference.

I wouldn't say that. Relativistic redshift is just a more complete description of Doppler shift. Doppler shift is not a major component of the redshift we observe when measuring distant objects. That is cosmological redshift, and is described by different mathematics and different underlying theory.

Rightly or wrongly, I am extrapolating from the observed "dark flow" to the entire visible universe. I don't see how a perturbation from outside of the visible universe can selectively influence portions of the visible universe without affecting it all pretty much the same.

I don't see the logic there. First of all, some places in our observable Universe may be causally connected to places outside it, while other parts of our observable Universe are causally disconnected from those same places. Second, we aren't seeing anything perturbed by something outside the observable universe. We're seeing something that was perturbed by something that is now outside the observable universe. We can't possibly be seeing something that is currently affected by something outside the observable universe; that would violate causality.

So you would restrict the observed "dark flow" to "just our little observable bubble"?

Not exactly. But I'd restrict our serious discussion of it to what's in the observable universe, since we can't know anything about what's happening outside that.

[Chris Peterson]

'
Evidence Grows for Multiverse. The fact is that this latest discovery puts the final nail in the Big Bang model...

You need to pay more attention to what is and is not highly speculative. There is precious little tangible evidence for multiverses. And most multiverse theories (such as they are) are completely consistent with the Big Bang model. In fact, consistency with the lambda CDM Big Bang model is pretty much required for a multiverse theory to be considered viable.

dark flow extends “all the way across the visible universe,” or about 47 billion light-years.

It may, or it may not. Either way, it doesn't radically affect current cosmological theory. BTW, 47 billion light years is the comoving radius of the observable universe, which means it's half way across.

[alter-ego]

Hello alter-ego

Thanks for your clarification. Once again I've been on a chess hiatus in an effort to refloat a chess opening ....

Hello again, astrolabe,
Back in the day, the risky King's Gambit was a favorite of mine for fiery play. Unfortunately I wasn't good enough to be successful with my equals. I liked the idea of baiting the opponent while he was focused on my King which that gambit is notorious for ...but it was fun!

And I sincerely thank you for your compliment and respect. I don't consider myself forum goer, but this topic drew me in. Thanks again and good luck with that opening.

[wonderboy]

Oh Right.

Here,s some more misquotes
''
Evidence Grows for Multiverse. The fact is that this latest discovery puts the final nail in the Big Bang model, even though the die-hard bangers will refuse to see it. What the evidence reported in the story is showing is that there is enough matter to create a gravity field detectable in the motions of the galaxies we can see from Earth, but the gravity field points to a source well outside the presumed edge of the universe which has been calculated from the observed red shift, which is assumed to be caused solely by relative velocity. But since the prime assumption is that our “banged” universe cannot reach that far, that there simply must be a wholly separate universe out there. Of course, since “universe” means “all that there is”, whatever is out there creating this gravity field is by definition part of this universe, which creates a paradox for the Big Bangers.''
http://www.prisonplanet.com/evidence-gr ... verse.html
http://news.branyvnimani.cz/?article_id=11362

dark flow extends “all the way across the visible universe,” or about 47 billion light-years.

Its everywhere. on the net.

Not necessarily. I've been giving this some serious thought, and I mean serious. I've been trying to think of a theory that would suit this gravitational tug and I believe I have found one. Its a bit far out but I'm going to finish my crude drawings and then post it all here. You can all laugh if you want I don't care. I just enjoy thinkin this stuff up. Plus I think its viable since we don't know everything there is to know about the universe, that much is apparent.

I'll post it in a minute or two

Paul

[wonderboy]

I'm not going to pretend that I know what I'm talking about because I am amateur at best. My mathematics isnt as good as it should be and I only got a standard grade 3 in physics. I am however a philosopher and a thinker and when it comes to space I can run rings around myself for days.

This topic has been annoying me for days, just trying to understand it has been hard enough. Anyway, I think I've come upon a theory, of my own devising, which fits whats happening in our universe. I believe that I am scientifically neutral enough to get past all the hard facts and just think of how something might work. Its now your job to debate the flaws of my theory of which there will probably be many.

I believe in the big bang. Something happened, and whatever it was created the universe which we live in today. After the big bang however, I believe a superhuge supermassive blackhole was created which is of unfathomabale size. It is this blackhole which I believe powers the universe' motion of the galaxies and objects contained within the Universe.

I cant find out how to post images, so I'm going to explain how this works as best I can.

What you want to do is draw a circle which counts as the blackhole.

Then you want to draw two petals at the top and at the bottom of the circle which are next to each other (there may be more than this in my theory)

What these petals stand for are exit points (emissions from the blackhole) and entry points (where the emissions return back to the blackholes event horizon)

Now the big bang spewed out all the matter of the universe and created a blackhole, the blackhole is so massive that it wants to suck back the material ejected by the big bang. this cause the material to curve left or right depending on the gravitational pull coming from other galaxies and other objects that are nearby.

When emission points get close this can account for gravitational distortions like the dark flow. (possibly)

when the galaxies are round the curve of the petal they are obviously heading towards a black hole and speeding up. which could account for the expansion of the universe etc. Plus not even light can escape a blackhole which would explain how we only have an "observable universe" rather than being unable to see it all.





This is probably complete rot, but I had fun thinking it up. If someone could tell me how to put a damn picture up here it would be greatly appreciated.

Thank you.

[astrolabe]

Hello alter-ego,

This is of course not on topic but FYI the Blackmar-Diemer Gambit and all variations is my particular nut to crack- been at it for 2yrs. now. BTW King's Gambit is sparky, gutsy, and you're right....FUN!!

[astrolabe]

Hello Chris (been a while eh?) and wonderboy (now I understand the moniker),

Just my 2 cent's: Typically in physics there is the phenomenon of fluid states, whether liquid or gas or vapor, to strive for equilibrium. This primarily occurs as a result of pressure gradients such as weather, steam systems, or hydrodynamics (fluids, plasmas etc.) where higher pressure/densities seek to go to lower pressure states in order to equalize. I think you already know where I'm going with this. DE is, ofcourse, within BB theory and could be viewed as a cosmic pressure of a sort and (if so viewed in that context) leads to the possibility that Dark Flow exists because the density within the flow is greater than the region of the universe it is expanding into. Even though Space is mostly empty it is not entirely empty. So one could argue for no beyond-the-known-Universe attractor of some kind. One could also argue the point that the Dark Flow phenom is the result of the Dark-Flow region being LESS dense than the space around it so that it is actually being "squeezed" into a direction in a kind of toothpaste tube effect.

Hey, I've said it before, if anyone can speculate- it's me. In fact I've come to the conclusion that I will NOT be out-speculated!!

[The Code]

This is probably complete rot, but I had fun thinking it up.

Nope, What you wrote was very interesting. Your thinking out of the box. which can be useful when thinking about the universe. I have a similar image in my mind which is also probably not a true picture of the universe. But like you said, you had fun thinking about trying to solve the mysteries of the universe. Your taking part in astronomy. And your enjoying it.



Mark

[Chris Peterson]

DE is, ofcourse, within BB theory and could be viewed as a cosmic pressure of a sort and (if so viewed in that context) leads to the possibility that Dark Flow exists because the density within the flow is greater than the region of the universe it is expanding into.

I think the extremely poor choice of calling this "dark flow" leads to all kinds of ideas that are probably not very appropriate. The terminology makes it seem as if something is actively pulling on this material, but I've seen nothing to suggest this is the case. There are "flows" of material all over the observable universe; this one just happens to be larger than the others, and doesn't have an obvious attractor. But it is pretty easily understood as motion that was set in place very early in the Universe- there is no need for this material to be causally connected with the mass that started it moving (although some of it may be). Neufer's example with the toy car and magnet should make it easy to visualize this interpretation. I like the explanation because it's very parsimonious: simple, feasible, and not requiring any adjustment to our current set of cosmological theories.

[astrolabe]

Hello Chris,

Did I miss something? My quote in your post didn't seem to be reflected in your response as I was proposing the idea that the "Dark Flow", which is to me also an inappropriate term, was not being caused by an unseen attraction but iterated the idea of conditions already existing on "our side" being the culprit instead, which could be as you say primordial indeed. My arguement was based on everyday physics, not the magnet/car concept.

[The Code]

I think the extremely poor choice of calling this "dark flow" leads to all kinds of ideas that are probably not very appropriate. The terminology makes it seem as if something is actively pulling on this material, but I've seen nothing to suggest this is the case.

Chris. You did not know about an 18 billion s/m/b/h till I showed you one. After harry's post. Here are some more misquotes for you to enjoy reading. I Think this Dark Flow is a work on going. I really would not write it off.

http://physicsworld.com/cws/article/news/41984

We are all learning.

Mark

[Chris Peterson]

Did I miss something? My quote in your post didn't seem to be reflected in your response as I was proposing the idea that the "Dark Flow", which is to me also an inappropriate term, was not being caused by an unseen attraction but iterated the idea of conditions already existing on "our side" being the culprit instead, which could be as you say primordial indeed. My arguement was based on everyday physics, not the magnet/car concept.

I just used your comments as an example of what I considered overly complex treatment of the question. But to be more specific, I don't think you can treat galaxies and galaxy clusters as a fluid, with flows caused by density gradients. There is no mechanism for coupling between these objects except gravity, and I can't see any way gravity can make galaxies behave in a fluid-like fashion. But we all know that gravity is attractive, so it's easy to see how a galaxy cluster, dark matter blob, or some other region of high mass could get a region moving. We see that happening now in the observable universe, just on a somewhat smaller scale.

[astrolabe]

Hello Chris,

Thanks and yes, duly noted. I forgot about Occam. As for "getting regions going" (I know semantics can be a problem) I still prefer the term falling especially where BH's are concerned as in energy/matter aquiring a near perfect state of rest. Just one example of less dense high energy (heat) falling to more dense low energy (cold).

[Chris Peterson]

Chris. You did not know about an 18 billion s/m/b/h till I showed you one.

So? I know about supermassive black holes, just hadn't heard about that particular one. I don't really see the relevance- except for being the largest one known, there's nothing special about it. It's just a big black hole.

I Think this Dark Flow is a work on going. I really would not write it off.

How am I writing it off? I'm just pointing out that it doesn't appear to change our understanding of cosmology in a radical way. The whole lambda CDM, inflationary model is substantially unchanged. It might provide some insight into details of the inflationary period, or some clues about parts of the Universe that we can no longer see. All very interesting and useful, but nothing earth shattering or game changing.

I still think "dark" is being overused. It makes great sense for dark matter. It's a questionable choice for dark energy. And it's just wrong for dark flow. People already use "dark energy" and "dark matter" in the same sentence all the time, because the names confuse them into thinking they are related. Another "dark" entity will further confuse the issue. With dark flow, there are no mysterious forces involved. It's just motion of galaxies and galaxy clusters, such as we see all over the Universe, not just in that region.

[The Code]

How am I writing it off?

When you wrote this Chris

There is no need for dark flow (if it exists)

13.7 billion years. No more. The Dark Flow suggests you need more time. We will see.

Mark

[Chris Peterson]

How am I writing it off?

When you wrote this Chris

There is no need for dark flow (if it exists)

Except I didn't say that. What I said was "There is no need for dark flow (if it exists... there remains a good deal of uncertainty about that) to be caused by anything pulling on it. All we seem to be observing is motion, and that requires no forces. The motion could be residual, from long ago. For instance, an area of high mass could have attracted the material early in the Universe- material that is now outside the observable Universe but was not then."

That's very different from the abbreviated quote you provide, and I don't see anything about it that writes off the phenomenon of dark flow.

13.7 billion years. No more. The Dark Flow suggests you need more time.

I don't see anything at all that suggests you need more time. Dark flow is just a tiny motion. We see many things that move much faster. And we see huge regions in motion around mass concentrations. A nearby galaxy cluster could have set the region of clusters associated with dark flow in motion in a very short time- a fraction of a second, even, if it was in the pre-inflationary period.

[The Code]

Well we will see, how it pans out. BTW. Its an absolute privilege, to talk about the subject I am fascinated by, to somebody with such knowledge as you Chris. Thanks.

I am done, with the dark flow, until there is more news on the subject.

Mark