Author Topic: CMB Cold Spot likely not a super void  (Read 1218 times)

Offline Star One

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CMB Cold Spot likely not a super void
« on: 04/26/2017 09:44 AM »
It appears that the cold spot found in the CMB data is likely not a super void further study has discovered leaving the door open for more exotic explanations. But how you would prove any other kind of explanation for it is beyond me especially as it appears to be just as likely blind random chance.

Quote
In their new work, the Durham team presented the results of a comprehensive survey of the redshifts of 7,000 galaxies, harvested 300 at a time using a spectrograph deployed on the Anglo-Australian Telescope. From this higher fidelity dataset, Mackenzie and Shanks see no evidence of a supervoid capable of explaining the Cold Spot within the standard theory.

The researchers instead found that the Cold Spot region, before now thought to be underpopulated with galaxies, is split into smaller voids, surrounded by clusters of galaxies. This 'soap bubble' structure is much like the rest of the universe, illustrated in Figure 2 by the visual similarity between the galaxy distributions in the Cold Spot area and a control field elsewhere.

Mackenzie commented: "The voids we have detected cannot explain the Cold Spot under standard cosmology. There is the possibility that some non-standard model could be proposed to link the two in the future but our data place powerful constraints on any attempt to do that."

If there really is no supervoid that can explain the Cold Spot, simulations of the standard model of the universe give odds of 1 in 50 that the Cold Spot arose by chance.

Shanks added: "This means we can't entirely rule out that the Spot is caused by an unlikely fluctuation explained by the standard model. But if that isn't the answer, then there are more exotic explanations.

'Perhaps the most exciting of these is that the Cold Spot was caused by a collision between our universe and another bubble universe. If further, more detailed, analysis of CMB data proves this to be the case then the Cold Spot might be taken as the first evidence for the multiverse - and billions of other universes may exist like our own."

https://m.phys.org/news/2017-04-survey-hints-exotic-cold.html

Here's the paper.

https://arxiv.org/abs/1704.03814
« Last Edit: 04/26/2017 09:59 AM by Star One »

Offline Star One

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Re: CMB Cold Spot likely not a super void
« Reply #1 on: 05/18/2017 09:55 AM »
I didn't realise that the theory of it colliding with another universe was actually a testable idea. But according to this article it is.

Quote
If Shanks and Mackenzie are correct then an alternative explanation for the cold spot must now be found. Simulations have shown that a random, non-Gaussian quantum fluctuation in the CMB has a 1 in 50 chance of creating the cold spot, but other, more exotic possibilities may also come into play. Among them is the idea that the cold spot is where our universe is bumping into another universe created by eternal inflation. This would produce an identifiable polarization signal in the cold spot. Data from the European Space Agency's Planck spacecraft that might prove or disprove this have yet to be fully analysed. If the polarization signal is there, however, then a collision with another universe would "become the most plausible explanation, believe it or not”, according to Shanks.

http://physicsworld.com/cws/article/news/2017/apr/26/competing-claims-over-cause-of-cosmic-cold-spot

Offline Ben the Space Brit

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Re: CMB Cold Spot likely not a super void
« Reply #2 on: 05/18/2017 12:53 PM »
I've been aware of at least the theory of inter-universal collisions since I read a book on M-Theory about 20 years back. However, the fact that they may have proof that it has happened in observable history is enough to make me feel a little twitchy!
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Offline RonM

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Re: CMB Cold Spot likely not a super void
« Reply #3 on: 05/18/2017 02:33 PM »
I've been aware of at least the theory of inter-universal collisions since I read a book on M-Theory about 20 years back. However, the fact that they may have proof that it has happened in observable history is enough to make me feel a little twitchy!

If the collision theory is true, it would be a great moment for M-Theory. While I appreciate and admire all the work that has gone into the various forms of String Theory, there still has not been a single prediction verified by experiment, making it more philosophy than physics. That's the problem with a top down approach as opposed to building up based on experimental results.

Offline jgoldader

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Re: CMB Cold Spot likely not a super void
« Reply #4 on: 05/18/2017 02:54 PM »
I hate to be the one to say it, but there are likely many explanations, most of which do not involve multiverses.  Theorists are sneaky and clever.  (Nasssty, wicked, tricksy little theoristses....)
« Last Edit: 05/18/2017 02:55 PM by jgoldader »
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Offline Star One

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CMB Cold Spot likely not a super void
« Reply #5 on: 05/18/2017 03:10 PM »
I hate to be the one to say it, but there are likely many explanations, most of which do not involve multiverses.  Theorists are sneaky and clever.  (Nasssty, wicked, tricksy little theoristses....)

Yes but how many them are actually testable in reality? Otherwise the ones that aren't are just words on paper.

This explanation appears to be testable so an answer will be known one way or another?
« Last Edit: 05/18/2017 03:11 PM by Star One »

Offline as58

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Re: CMB Cold Spot likely not a super void
« Reply #6 on: 05/18/2017 08:56 PM »
I hate to be the one to say it, but there are likely many explanations, most of which do not involve multiverses.  Theorists are sneaky and clever.  (Nasssty, wicked, tricksy little theoristses....)

There's indeed a very natural explanation: it's just a random fluctuation that happens to be there. The Cold Spot is not that anomalous.

Offline Star One

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Re: CMB Cold Spot likely not a super void
« Reply #7 on: 05/18/2017 11:22 PM »
I hate to be the one to say it, but there are likely many explanations, most of which do not involve multiverses.  Theorists are sneaky and clever.  (Nasssty, wicked, tricksy little theoristses....)

There's indeed a very natural explanation: it's just a random fluctuation that happens to be there. The Cold Spot is not that anomalous.
They do mention that, but it could still also be something else. Best of course to wait until the Planck analysis is finished rather than jumping to conclusions now.

To me you saying this is really no better than those saying its evidence of the multiverse, both are unsupportable conclusions at this time.

By the way you saying it's not that anomalous seems odd, as if it wasn't anomalous they wouldn't be spending all their time looking into it.
« Last Edit: 05/19/2017 07:38 AM by Star One »

Offline as58

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Re: CMB Cold Spot likely not a super void
« Reply #8 on: 05/19/2017 08:56 AM »
I hate to be the one to say it, but there are likely many explanations, most of which do not involve multiverses.  Theorists are sneaky and clever.  (Nasssty, wicked, tricksy little theoristses....)

There's indeed a very natural explanation: it's just a random fluctuation that happens to be there. The Cold Spot is not that anomalous.
They do mention that, but it could still also be something else. Best of course to wait until the Planck analysis is finished rather than jumping to conclusions now.

To me you saying this is really no better than those saying its evidence of the multiverse, both are unsupportable conclusions at this time.

By the way you saying it's not that anomalous seems odd, as if it wasn't anomalous they wouldn't be spending all their time looking into it.

It is anomalous, but only 'slightly'. As also the Physics World article mentions, an anomalous spot as large and deep is seen in ~1-2 percent of simulations using standard cosmological model. So it's not some one in a million or one in a billion miracle.

Offline Star One

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CMB Cold Spot likely not a super void
« Reply #9 on: 05/19/2017 08:59 AM »
I hate to be the one to say it, but there are likely many explanations, most of which do not involve multiverses.  Theorists are sneaky and clever.  (Nasssty, wicked, tricksy little theoristses....)

There's indeed a very natural explanation: it's just a random fluctuation that happens to be there. The Cold Spot is not that anomalous.
They do mention that, but it could still also be something else. Best of course to wait until the Planck analysis is finished rather than jumping to conclusions now.

To me you saying this is really no better than those saying its evidence of the multiverse, both are unsupportable conclusions at this time.

By the way you saying it's not that anomalous seems odd, as if it wasn't anomalous they wouldn't be spending all their time looking into it.

It is anomalous, but only 'slightly'. As also the Physics World article mentions, an anomalous spot as large and deep is seen in ~1-2 percent of simulations using standard cosmological model. So it's not some one in a million or one in a billion miracle.

Look I get it by now anytime someone comes up with a theory outside the supposed norms of this area you seem to feel duty bound to shoot it down.

I think this quote probably gets to the heart of why some don't seem to like the multiverse theory, but as it says nature trumps all.

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Put this way, a multiverse doesn’t sound attractive. It would cut to the very heart of physics’ purpose. Nature, of course, doesn’t care about this. Maybe the cosmos really is this way and we just have to accept it. Certainly, there are many who are willing to defend the multiverse as a valid direction for thought.

https://www.theguardian.com/science/across-the-universe/2017/may/17/multiverse-have-astronomers-found-evidence-of-parallel-universes
« Last Edit: 05/19/2017 09:06 AM by Star One »

Offline KelvinZero

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Re: CMB Cold Spot likely not a super void
« Reply #10 on: 05/19/2017 12:57 PM »
It is anomalous, but only 'slightly'. As also the Physics World article mentions, an anomalous spot as large and deep is seen in ~1-2 percent of simulations using standard cosmological model. So it's not some one in a million or one in a billion miracle.
This isn't responding to the OP article is it? You are just saying a gap large enough to explain this is not astronomically unlikely given the distribution of 'blobbyness' to use a technical term and would not need a special explanation.

but aren't they saying that the cold does not seem to correspond to a large void? There are too many galaxies in the location? It is not empty enough?

Offline Star One

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CMB Cold Spot likely not a super void
« Reply #11 on: 05/19/2017 01:09 PM »
It is anomalous, but only 'slightly'. As also the Physics World article mentions, an anomalous spot as large and deep is seen in ~1-2 percent of simulations using standard cosmological model. So it's not some one in a million or one in a billion miracle.
This isn't responding to the OP article is it? You are just saying a gap large enough to explain this is not astronomically unlikely given the distribution of 'blobbyness' to use a technical term and would not need a special explanation.

but aren't they saying that the cold does not seem to correspond to a large void? There are too many galaxies in the location? It is not empty enough?

Correct. That's why I was questioning the OP's statement on this as to me what he was saying was at complete odds with what the article I posted actually says. In fact the conclusion of their paper is a counter to the argument the OP is trying to make.
« Last Edit: 05/19/2017 01:11 PM by Star One »

Offline as58

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Re: CMB Cold Spot likely not a super void
« Reply #12 on: 05/19/2017 01:12 PM »
It is anomalous, but only 'slightly'. As also the Physics World article mentions, an anomalous spot as large and deep is seen in ~1-2 percent of simulations using standard cosmological model. So it's not some one in a million or one in a billion miracle.
This isn't responding to the OP article is it? You are just saying a gap large enough to explain this is not astronomically unlikely given the distribution of 'blobbyness' to use a technical term and would not need a special explanation.

but aren't they saying that the cold does not seem to correspond to a large void? There are too many galaxies in the location? It is not empty enough?

The paper says that the cold spot is not caused by ISW (though as far as I know, that was already pretty well established), so it's most likely primordial. However, that doesn't require necessarily any new exotic physics - the spot is only mildly unlikely in the standard cosmological model.

Offline Star One

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CMB Cold Spot likely not a super void
« Reply #13 on: 05/19/2017 01:23 PM »
It is anomalous, but only 'slightly'. As also the Physics World article mentions, an anomalous spot as large and deep is seen in ~1-2 percent of simulations using standard cosmological model. So it's not some one in a million or one in a billion miracle.
This isn't responding to the OP article is it? You are just saying a gap large enough to explain this is not astronomically unlikely given the distribution of 'blobbyness' to use a technical term and would not need a special explanation.

but aren't they saying that the cold does not seem to correspond to a large void? There are too many galaxies in the location? It is not empty enough?

The paper says that the cold spot is not caused by ISW (though as far as I know, that was already pretty well established), so it's most likely primordial. However, that doesn't require necessarily any new exotic physics - the spot is only mildly unlikely in the standard cosmological model.

Why do you insist on promulgating this as an answer when the paper points out there is still more data to analyse.
« Last Edit: 05/19/2017 01:23 PM by Star One »

Offline hop

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Re: CMB Cold Spot likely not a super void
« Reply #14 on: 05/19/2017 04:32 PM »
Why do you insist on promulgating this as an answer when the paper points out there is still more data to analyse.
IMO, this is uncalled for. The reality is that some ideas are a lot less well supported than others. People who are familiar with a field often have a better idea where that lines falls than those who just follow along in the popular press.

Theorists love coming up with exotic explanations for anomalies that are just barely on the edge of being statistically interesting. This is a good thing: sometimes those little anomalies lead to important insights, but does mean one should exercise a bit of caution with the breathless headlines that often follow.

From the article in the op
Quote
If there really is no supervoid that can explain the Cold Spot, simulations of the standard model of the universe give odds of 1 in 50 that the Cold Spot arose by chance.
As as58 said, those odds are really nothing to get excited about.

Offline Star One

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Re: CMB Cold Spot likely not a super void
« Reply #15 on: 05/19/2017 04:36 PM »
Why do you insist on promulgating this as an answer when the paper points out there is still more data to analyse.
IMO, this is uncalled for. The reality is that some ideas are a lot less well supported than others. People who are familiar with a field often have a better idea where that lines falls than those who just follow along in the popular press.

Theorists love coming up with exotic explanations for anomalies that are just barely on the edge of being statistically interesting. This is a good thing: sometimes those little anomalies lead to important insights, but does mean one should exercise a bit of caution with the breathless headlines that often follow.

From the article in the op
Quote
If there really is no supervoid that can explain the Cold Spot, simulations of the standard model of the universe give odds of 1 in 50 that the Cold Spot arose by chance.
As as58 said, those odds are really nothing to get excited about.

I don't think it is uncalled for and I stand by my comments as I believe they are trying to put their personal theory/beliefs in front of the data. Especially when as it says in the paper there is further analysis of the Planck data to come.

Offline as58

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Re: CMB Cold Spot likely not a super void
« Reply #16 on: 05/19/2017 06:56 PM »
My point was that this particular article has been hyped up in popular press completely out of proportion as somehow presenting evidence of multiverse. My opinion is hardly unusual among astrophysicists, see for example this (there's even a comment from one of the authors there) or this (with comments from the first author).

Offline Star One

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Re: CMB Cold Spot likely not a super void
« Reply #17 on: 05/19/2017 07:27 PM »
My point was that this particular article has been hyped up in popular press completely out of proportion as somehow presenting evidence of multiverse. My opinion is hardly unusual among astrophysicists, see for example this (there's even a comment from one of the authors there) or this (with comments from the first author).
Well being as the better articles on this actually quoted from the paper, which having read the paper the quotes appear accurate (I mean they haven't been doctored) I can only assume you're accusing the authors of the paper of hype?

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