Huge Hole Found in the Universe

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Buzz Bloom
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Summary:

This is from an article in space.com by by Robert Roy Britt August 23, 2007.
The hole is nearly a billion light-years across. This one is mostly devoid of stars, gas and other normal matter, and it's also strangely empty of the mysterious "dark matter" that permeates the cosmos.
Other space voids have been found before, but nothing on this scale.
https://www.space.com/4271-huge-hole-universe.html

I would much appreciate any links cited to more information about this hole, especially more recent information. I would also appreciate any information to clarify the following questions.

How much baryonic matter is actually present (taking into account “mostly devoid”)?

Is is mostly hydrogen gas, i.e., either atomic H or H2?

How is this measured?

How it is possible to ascertain the amount (or absence) of dark matter present (taking into account that the presence of dark matter is usually calculated by the pattern of orbits of baryonic matter in a galaxy)?

How big are other space voids (presumably having no stars)?

How far away from Earth are these other voids?

ADDED:
The link at the top. I apologize for forgetting to put it in. I blame it on a senior moment. Thank you @phinds for reminding me.
 
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  • #2
phinds
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Summary:: This is from an article in space.com by by Robert Roy Britt August 23, 2007.
Buzz, you've been here long enough to know that a SPECIFIC citation is expected.

Also, I think I remember fairly recent discussion(s) here on PF about voids so you might try a forum search
 
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  • #3
Vanadium 50
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Buzz, here is what you do.

You get the article by Britt. You then go to your favorite search engine and plug in relevant words from the article: Rudnick, Williams, VLA, Astrophysical Journal. I used Google, and the 2nd link was the paper in question.
 
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  • #4
Buzz Bloom
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You get the article by Britt. You then go to your favorite search engine and plug in relevant words from the article: Rudnick, Williams, VLA, Astrophysical Journal. I used Google, and the 2nd link was the paper in question.
Hi Van:

I do appreciate your help, but I have had some currently unsolved problems. I have tried using both Google and Firefox with several search lists:
Rudnick, Williams, VLA, Astrophysical Journal,​
Astrophysical Journal Rudnick Brown Williams, and​
Astrophysical Journal Rudnick Brown Williams billion light-years.​
The only result that was even partially useful was finding several times
I can find nothing at this site for searching for an author or a topic. There was a button for selecting a particular volume. I assumed that the year of publication would be 2007, so I tried the first 2007 issue:
Vol 654, 2007.​
When I clicked on "GO", I got the following options.
Latest issues
° Number 2, January 2007
° Number 1, January 2007
I clicked on "Number 1", and I got a list of 53 article titles, each with a list of authors. Unfortunately I was unable to find any way to automatically search for an author on the page. The normal search of Firefox or Google for text on a page failed to work.

I confess I gave up. It seems to me to be too difficult to visually search each issue for the year 2007, article by article, and author by author.

Do have any suggestions?

ADDED
BTW: I did find a paper on a different topic that interests me.

Regards,
Buzz
 
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  • #6
Buzz Bloom
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Anyone who didn't get https://iopscience.iop.org/article/10.1086/522222 raise their hands.
Hi Van:

Thank you very much for the link. I confess I have not read it carefully yet, but I have scanned through it, and I find it to be likely that it is much over my head, and I will not be able to find in it any understandable answers to the questions I included in post #1. I also did not find any clear understandable support for several statements made in the SPACE.COM article:
1. The hole is nearly a billion light-years across.​
2. Rather, this one is mostly devoid of stars, gas and other normal matter, and it's also strangely empty of the mysterious "dark matter" that permeates the cosmos.​
3. "Although our surprising results need independent confirmation, the slightly colder temperature of the CMB in this region appears to be caused by a huge hole devoid of nearly all matter roughly 6 to 10 billion light-years from Earth," Rudnick said.​
It is of course possible some of these statements are based on material from earlier referenced articles.

Regards,
Buzz
 
  • #7
Ibix
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[edit by mod to remove response to misinformation]

@Buzz Bloom - on large scales, inhomogeneities in matter density can cause a redshift variation due to something called the "integrated Sachs-Wolfe effect". Essentially, due to cosmological expansion light doesn't lose the same energy climbing out of an over-dense region as it gains falling into it, and you can see a slight change in the redshift as a result. The abstract of the IOP Science paper Vanadium 50 linked says that they can explain the observed redshift variation in this portion of the sky if there's a very nearly completely empty space, but that's highly improbable.
 
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  • #8
russ_watters
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Thread re-opened after cleanup of misinformation and responses to it.
 
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  • #9
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Curious, back to the OP. Wikipedia has the Bootes Void as the largest known void with a diameter of 330M LY
https://en.wikipedia.org/wiki/Boötes_void

This would be 3x larger if confirmed. I would assume the other known voids similarly void of dark matter? It would seem logical
 
  • #10
russ_watters
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Curious, back to the OP. Wikipedia has the Bootes Void as the largest known void with a diameter of 330M LY
https://en.wikipedia.org/wiki/Boötes_void

This would be 3x larger if confirmed. I would assume the other known voids similarly void of dark matter? It would seem logical
Not a direct reply, but note that the article/discovery in the OP is 13 years old.
 
  • #11
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Not a direct reply, but note that the article/discovery in the OP is 13 years old.
Saw that, and there is a Wikipedia article on it where it still appears unconfirmed

https://en.wikipedia.org/wiki/CMB_cold_spot

Although someone offered this explanation:

A controversial claim by Laura Mersini-Houghton is that it could be the imprint of another universe beyond our own, caused by quantum entanglement between universes before they were separated by cosmic inflation.[3] Laura Mersini-Houghton said, "Standard cosmology cannot explain such a giant cosmic hole" and made the remarkable hypothesis that the WMAP cold spot is "… the unmistakable imprint of another universe beyond the edge of our own."
 
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  • #12
Ibix
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Curious, back to the OP. Wikipedia has the Bootes Void as the largest known void with a diameter of 330M LY
https://en.wikipedia.org/wiki/Boötes_void

This would be 3x larger if confirmed. I would assume the other known voids similarly void of dark matter? It would seem logical
Worth noting that Wikipedia's list of voids has quite a few larger than Bootes.

I don't know the answer to your question either, but it occurs to me that if there was significant dark matter in a void it would be unlikely to form. As I understand it, voids (of any size) form because over-dense regions contract under their own gravity leaving under-dense regions growing. If a void is full of dark matter then it isn't under-dense and there is less of a mechanism driving the surrounding visible matter to collapse, and the not-actually-under-dense region won't grow. I could be wrong, though.
 
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  • #13
davenn
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2. Rather, this one is mostly devoid of stars, gas and other normal matter, and it's also strangely empty of the mysterious "dark matter" that permeates the cosmos.
That isnt strange, As BWV said "logical" and as @Drakkith said in another thread on voids
"if it had dark matter in it ( the void) then there would, because of gravitational attraction, also be normal matter"
 
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  • #14
Buzz Bloom
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That isnt strange
Hi Dave:

What I find strange is not that there might not be dark matter present, but I do not know of any possible way in which this can be observed. I am guessing you might be saying that the conclusion about dark matter might be a conjecture based on some model which projects that the presence of dark matter would imply that a greater amount of baryonic matter would be present than that which is observed. I also get that the paper says that baryonic matter is mostly not present. What I have not found in the paper (so far) is a specific number related to the actual baryonic density in the hole. As I mentioned in post #6, this absent information may possibly be in some of the referenced papers.

BTW: I vaguely remember reading recently about a mechanism for dark matter to create some (most? all?) of the primordial matter density perturbations. I do not recall reading anywhere any mechanism for dark matter to vacate a large void.

Regards,
Buzz
 
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  • #15
Ibix
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What I find strange is not that there might not be dark matter present, but I do not know of any possible way in which this can be observed.
The integrated Sachs-Wolfe effect is what the paper linked by Vanadium 50 says is what they used. See post #7.
 
  • #16
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A controversial claim by Laura Mersini-Houghton is that it could be the imprint of another universe beyond our own, caused by quantum entanglement between universes before they were separated by cosmic inflation.[3] Laura Mersini-Houghton said, "Standard cosmology cannot explain such a giant cosmic hole" and made the remarkable hypothesis that the WMAP cold spot is "… the unmistakable imprint of another universe beyond the edge of our own."
Hi BWV:

I am wondering if you might know (perhaps based on seeing various posts by monitors) if this claim (or similar claims that are not scientifically testable) is considered by PFs to be a part of science.

Regards,
Buzz
 
  • #17
Buzz Bloom
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The integrated Sachs-Wolfe effect
Hi Ibix:

I am confused by the following from
It occurs when the Universe is dominated in its energy density by something other than matter. If the Universe is dominated by radiation, or by dark energy, though, those potentials do evolve, subtly changing the energy of photons passing through them.​
This puts a limit on when this phenomenon happens. Since the discussion is about events after decoupling, radiation is irrelevant. If dark energy is cause of the phenomenon, how does it work to make dark matter to be not present?

Regards,
Buzz
 
  • #18
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Hi BWV:

I am wondering if you might know (perhaps based on seeing various posts by monitors) if this claim (or similar claims that are not scientifically testable) is considered by PFs to be a part of science.

Regards,
Buzz
If feasible testability was the standard for theoretical physics they wouldn’t they have to shut down the whole ‘Beyond the Standard Model’ forum? Judging from her Wikipedia page , she is a real astrophysicist that has done serious work.
 
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  • #19
Ibix
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If dark energy is cause of the phenomenon, how does it work to make dark matter to be not present?
I think you are misunderstanding. Density variation in matter and dark matter causes there to be large scale gravity wells associated with over-dense areas and gravity whatever-the-opposite-of-wells-is where there are under-dense regions. In a dark energy dominated universe, the way the expansion of the universe works tends to "flatten out" the potentials. So a photon loses less energy as it comes out of a well than it gained going in, leading to a slight blue-shift. For reasons I don't understand (I'd have to track down a detailed mathematical description of the integrated Sachs-Wolfe effect), this frequency shift doesn't happen in a matter dominated universe.

All the paper is saying is that they reckon they can account for the "cold spot" if there's a completely empty region there. Dark energy isn't responsible for making it empty. It's just responsible for a detectable change in photon redshifts when they cross such a region.
 
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  • #20
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Curious what the maximum amount / density of matter (dark or otherwise) needed to show the region as 'empty' if gravitational effects on EM is the only yardstick available. How much dark (as in not emitting light, not as in dark matter) stuff could be in these voids?
 
  • #21
Buzz Bloom
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If feasible testability was the standard for theoretical physics
Hi BWV:

I am thinking that the standard need not be "feasible testability", but rather "in principle possible testability". If no one has any idea about how it might be theoretically possible to test a hypothesis with observation, it seems to me that this is a very serious lack.

For example, at the present time it is not feasible to observe Hawking radiation from a black hole. However, it is theortically likely to become possible when at some distant time in the future the CMB radiation temperature becomes less than the temperature of Hawking radiation.

Regards,
Buzz
 
  • #22
bob012345
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That isnt strange, As BWV said "logical" and as @Drakkith said in another thread on voids
"if it had dark matter in it ( the void) then there would, because of gravitational attraction, also be normal matter"
Doesn't the apparent correlation of the lack of matter to the lack of dark matter also imply that dark matter is not some very exotic particle but probably normal matter such as some form of Hydrogen as some have suggested?

https://www.sciencemag.org/news/2005/02/dark-matter-need-not-apply
 
  • #23
Buzz Bloom
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I think you are misunderstanding.
. . .
Dark energy isn't responsible for making it empty. It's just responsible for a detectable change in photon redshifts when they cross such a region.
Hi Ibix:

I think that this dark energy point is a very good answer to my quote #3 in post #6 from SPACE.COM.
3. "Although our surprising results need independent confirmation, the slightly colder temperature of the CMB in this region appears to be caused by a huge hole devoid of nearly all matter roughly 6 to 10 billion light-years from Earth," Rudnick said.​

You are right about my misunderstanding. I was thinking that my quote #2 was being discussed.
2. Rather, this one is mostly devoid of stars, gas and other normal matter, and it's also strangely empty of the mysterious "dark matter" that permeates the cosmos.​

Regards,
Buzz
 
  • #24
TeethWhitener
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Hi BWV:

I am wondering if you might know (perhaps based on seeing various posts by monitors) if this claim (or similar claims that are not scientifically testable) is considered by PFs to be a part of science.

Regards,
Buzz
Here’s the first of two articles (published in Phys Rev D) dealing with the claims in question:
https://arxiv.org/abs/hep-th/0611223

Edit: the “parallel universes” in question have to do with potential quantum entanglement between a portion of our observable universe and a portion of the unobservable universe beyond the particle horizon. Presumably particles which were entangled in the pre-inflation universe would remain entangled after inflation, even though they would no longer be causally connected.
 
  • #25
Buzz Bloom
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“parallel universes” in question have to do with potential quantum entanglement between a portion of our observable universe and a portion of the unobservable universe
Hi TW:

I guess I misunderstood the language "parallel universe" used by Dr. Houghton, and I thought it to be referring to the multi-universe interpretation of QM. I now see it was intended to mean two distinct portions of our universe (not separate entire universes). One portion contains the mass of our observable universe. The other is some mass not currently in out observable universe, but it was included at an earlier period of time as part of an younger observable universe which also included the mass of what is our current observable universe.

Now that I understand what Dr. Houghton was saying, I still have some reservations about it, which you (or perhaps another PFs participant) might be able to clarify for me. I may be mistaken , but I thought that in the earlier time of our universe when z>9 the dark energy density was much less than mass density, and the volume of an observable universe got larger. For small values of z the observable universe may loose a part of it as the universe expands. If this is correct, how does it fit in with Dr. Houghton's idea?

Regards,
Buzz
 

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