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."
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.
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!
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....)
Quote from: jgoldader on 05/18/2017 02:54 pmI 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.
Quote from: as58 on 05/18/2017 08:56 pmQuote from: jgoldader on 05/18/2017 02:54 pmI 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.
Quote from: Star One on 05/18/2017 11:22 pmQuote from: as58 on 05/18/2017 08:56 pmQuote from: jgoldader on 05/18/2017 02:54 pmI 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.
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.
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.
Quote from: as58 on 05/19/2017 08:56 amIt 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?
Quote from: KelvinZero on 05/19/2017 12:57 pmQuote from: as58 on 05/19/2017 08:56 amIt 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.
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.
Quote from: Star One on 05/19/2017 01:23 pmWhy 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 opQuoteIf 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.
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).