Was There Really a Billion Lightyear-Wide Void in the Sky?

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Discussion Overview

The discussion centers on the existence of a purported billion lightyear-wide void in the universe, as initially reported by Rudnick et al. Participants explore the implications of this void, its statistical analysis, and the ongoing debate surrounding its validity within the context of cosmological models.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Exploratory

Main Points Raised

  • Rudnick et al. reported a void with significantly fewer galaxies than similar regions, leading to speculation about its nature, including ideas related to the multiverse.
  • Kendrick Smith and Dragan Huterer argue that the void may be a result of inadequate statistical analysis, presenting evidence of higher-than-average density regions within the supposed void.
  • David Spergel has acknowledged the work of Smith and Huterer, suggesting some level of professional support for their findings.
  • A later paper claims to find no significant evidence for the cold spot associated with the void, challenging the initial claims made by Rudnick et al.
  • Another participant points to a different paper that suggests a correlation between hot and cold spots and voids, indicating that the issue remains complex and unresolved.

Areas of Agreement / Disagreement

Participants express differing views on the existence and significance of the void, with some supporting the initial claims and others challenging them based on statistical analysis. The discussion remains unresolved, with multiple competing perspectives presented.

Contextual Notes

There are limitations regarding the statistical methods used in the analyses, and the dependence on specific cosmological models is acknowledged. The ongoing nature of the research and the submission status of various papers contribute to the complexity of the discussion.

marcus
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http://www.eurekalert.org/pub_releases/2008-05/ns-hhi051408.php

Last year Rudnick et al thought they saw a big hole in the sky, a billion lightyears wide.

It had some galaxies in it, they said, but significantly fewer than equalsize volumes in other parts of the sky.

That was around November 2007. There was some silly talk about it's being the "gateway to another universe", and it suited some people's "multiverse" ideas. The NewScientist had a coverstory about it.

Kendrick Smith at Cambridge says that the notion of a void probably resulted from inadequate statistical analysis. He and Dragan Huterer have found regions of higher-than-average density contained within the supposed "hole". They are getting a paper ready to submit to the Monthly Notices of RAS.

David Spergel at Princeton has given Smith and Huterer's work a nod of approval. Spergel is a WMAP chief and the lead author of many of the official WMAP reports. Authority and professional consensus do NOT ultimately decide scientific truth, right? But they can be useful straws in the wind. I'd guess this particular gateway to another universe is destined for the dump. If any corroboration turns up later, please tell me about it. Love to be wrong :biggrin:
 
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Here is the said paper:

http://arxiv.org/abs/0805.2751

No evidence for the cold spot in the NVSS radio survey
Authors: Kendrick M. Smith, Dragan Huterer
(Submitted on 18 May 2008)

Abstract: We revisit recent claims that there is a "cold spot" in both number counts and brightness of radio sources in the NVSS survey, with location coincident with the previously detected cold spot in WMAP. Such matching cold spots would be difficult if not impossible to explain in the standard LCDM cosmological model. Contrary to the claim, we find no significant evidence for the radio cold spot, after including systematic effects in NVSS, and carefully accounting for the effect of a posteriori choices when assessing statistical significance.
 
I agree, cristo. A lengthy stream of random numbers will inevitably produce statistically improbable sequences. The 'a posteriori' objection is well founded.
 
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Looks like this issue isn't resolved yet, have a look at http://arxiv.org/abs/0805.2974" paper which has looked at a great number of hot and cold spots and their relationships to voids and clusters seen in the Sloan Digitial Sky Survey. They claim there is a highly significant correlation, for these spots in general, including the 'extreme Cold Spot' under question in this thread.

It doesn't say where the paper is submitted too, but looks to be in the Nature format. That would be odd though, since Nature doesn't permit you to post to arXiv before publication. In any case it's clear that this is a tricky question that may be debated for a while yet!
 
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