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Thread: Void Models and the Copernicna Principle

  1. #1 Void Models and the Copernicna Principle 
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    Here is an interesting article about void models.
    Scientists: Earth May Exist in Giant Cosmic Bubble | Fox News

    They do challenge the Copernican Principle, but are becoming more popular (LTB, Lemaitre-Tolman-Bondi models typically). This article explains why there is some hesitation to consider them. Herre are some interesting quotes:

    One problem with the void idea, though, is that it negates a principle that has reigned in astronomy for more than 450 years: namely, that our place in the universe isn't special.

    When Nicholas Copernicus argued that it made much mo
    re sense for the Earth to be revolving around the sun than vice versa, it revolutionized science.

    Since then, most theories have to pass the Copernican test. If they require our planet to be unique, or our position to be exalted, the ideas often seem unlikely.

    "This idea that we live in a void would really be a statement that we live in a special place," Clifton told SPACE.com. "The regular cosmological model is based on the idea that where we live is a typical place in the universe. This would be a contradiction to the Copernican principle."


    Another explains that the redshift distance relation is skewed, and in fact, this means the universe may not be expanding in an accelerated manner:

    If we lived in a very large under-density, then the space-time itself wouldn't be accelerating," said researcher Timothy Clifton of Oxford University in England. "It would just be that the observations, if interpreted in the usual way, would look like they were.


    Last edited by JoeSixPack; May 14th, 2014 at 11:04 AM. Reason: typo
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  3. #2  
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    Quote Originally Posted by JoeSixPack View Post
    Here is an interesting article about void models.
    Scientists: Earth May Exist in Giant Cosmic Bubble | Fox News

    They do challenge the Copernican Principle, but are becoming more popular (LTB, Lemaitre-Tolman-Bondi models typically). This article explains why there is some hesitation to consider them. Herre are some interesting quotes:

    One problem with the void idea, though, is that it negates a principle that has reigned in astronomy for more than 450 years: namely, that our place in the universe isn't special.

    When Nicholas Copernicus argued that it made much mo
    re sense for the Earth to be revolving around the sun than vice versa, it revolutionized science.

    Since then, most theories have to pass the Copernican test. If they require our planet to be unique, or our position to be exalted, the ideas often seem unlikely.

    "This idea that we live in a void would really be a statement that we live in a special place," Clifton told SPACE.com. "The regular cosmological model is based on the idea that where we live is a typical place in the universe. This would be a contradiction to the Copernican principle."


    Another explains that the redshift distance relation is skewed, and in fact, this means the universe may not be expanding in an accelerated manner:

    If we lived in a very large under-density, then the space-time itself wouldn't be accelerating," said researcher Timothy Clifton of Oxford University in England. "It would just be that the observations, if interpreted in the usual way, would look like they were.
    This was back in 2008, so I thought I'd try to see if the scientist involved, Timothy Clifton, has followed it up at all in the six years since.

    And he has: https://www2.physics.ox.ac.uk/contac...t/publications

    The conclusion seems to be - if I interpret it correctly- that, when you do the modelling, it doesn't work after all.


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  4. #3  
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    Why do I keep seeing these Copernican threads pop up instead of having them all in the same thread?
    "Sometimes I think the surest sign that intelligent life exists elsewhere in the universe is that none of it has tried to contact us." -Calvin
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  5. #4  
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    Quote Originally Posted by exchemist View Post
    Quote Originally Posted by JoeSixPack View Post
    Here is an interesting article about void models.
    Scientists: Earth May Exist in Giant Cosmic Bubble | Fox News

    They do challenge the Copernican Principle, but are becoming more popular (LTB, Lemaitre-Tolman-Bondi models typically). This article explains why there is some hesitation to consider them. Herre are some interesting quotes:

    One problem with the void idea, though, is that it negates a principle that has reigned in astronomy for more than 450 years: namely, that our place in the universe isn't special.

    When Nicholas Copernicus argued that it made much mo
    re sense for the Earth to be revolving around the sun than vice versa, it revolutionized science.

    Since then, most theories have to pass the Copernican test. If they require our planet to be unique, or our position to be exalted, the ideas often seem unlikely.

    "This idea that we live in a void would really be a statement that we live in a special place," Clifton told SPACE.com. "The regular cosmological model is based on the idea that where we live is a typical place in the universe. This would be a contradiction to the Copernican principle."


    Another explains that the redshift distance relation is skewed, and in fact, this means the universe may not be expanding in an accelerated manner:

    If we lived in a very large under-density, then the space-time itself wouldn't be accelerating," said researcher Timothy Clifton of Oxford University in England. "It would just be that the observations, if interpreted in the usual way, would look like they were.
    This was back in 2008, so I thought I'd try to see if the scientist involved, Timothy Clifton, has followed it up at all in the six years since.

    And he has: https://www2.physics.ox.ac.uk/contac...t/publications

    The conclusion seems to be - if I interpret it correctly- that, when you do the modelling, it doesn't work after all.
    He concludes (my empahsis): "and effectively rules out simple LTB models as an explanation of dark energy"

    I am seeing a lot of work ion void models though, even today, so no one has given up on them. I think it is related to the challenges to inflation posed by the CMB anistropies, and LTB is a way out while still maintaining something close to standard model type physics.
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  6. #5  
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    Quote Originally Posted by JoeSixPack View Post
    Quote Originally Posted by exchemist View Post
    Quote Originally Posted by JoeSixPack View Post
    Here is an interesting article about void models.
    Scientists: Earth May Exist in Giant Cosmic Bubble | Fox News

    They do challenge the Copernican Principle, but are becoming more popular (LTB, Lemaitre-Tolman-Bondi models typically). This article explains why there is some hesitation to consider them. Herre are some interesting quotes:

    One problem with the void idea, though, is that it negates a principle that has reigned in astronomy for more than 450 years: namely, that our place in the universe isn't special.

    When Nicholas Copernicus argued that it made much mo
    re sense for the Earth to be revolving around the sun than vice versa, it revolutionized science.

    Since then, most theories have to pass the Copernican test. If they require our planet to be unique, or our position to be exalted, the ideas often seem unlikely.

    "This idea that we live in a void would really be a statement that we live in a special place," Clifton told SPACE.com. "The regular cosmological model is based on the idea that where we live is a typical place in the universe. This would be a contradiction to the Copernican principle."


    Another explains that the redshift distance relation is skewed, and in fact, this means the universe may not be expanding in an accelerated manner:

    If we lived in a very large under-density, then the space-time itself wouldn't be accelerating," said researcher Timothy Clifton of Oxford University in England. "It would just be that the observations, if interpreted in the usual way, would look like they were.
    This was back in 2008, so I thought I'd try to see if the scientist involved, Timothy Clifton, has followed it up at all in the six years since.

    And he has: https://www2.physics.ox.ac.uk/contac...t/publications

    The conclusion seems to be - if I interpret it correctly- that, when you do the modelling, it doesn't work after all.
    He concludes (my empahsis): "and effectively rules out simple LTB models as an explanation of dark energy"

    I am seeing a lot of work ion void models though, even today, so no one has given up on them. I think it is related to the challenges to inflation posed by the CMB anistropies, and LTB is a way out while still maintaining something close to standard model type physics.
    Ah, OK, do you have any reference to work done on these since 2011, then?

    This article, in 2012, seems to conclude that void models have more or less had it, thanks to recent observations by the Hubble telescope:http://www.pbs.org/wgbh/nova/blogs/p...o-dark-energy/

    The observation in question is detailed here: NASA - NASA's Hubble Rules Out One Alternative to Dark Energy
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  7. #6  
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    Quote Originally Posted by JoeSixPack View Post
    He concludes (my empahsis): "and effectively rules out simple LTB models as an explanation of dark energy"
    I assume you have only read the abstract. What he means by that is that they have not been able to come up with a model that fits all of the data. (This is rather like the mathematicians use of "non trivial" to mean apparently impossible, but not provably so.)

    He then goes on to highlight some of the shortcomings in their approach (for example, the assumption "that we are exactly in the center of a perfectly spherically symmetric void, serves to simplify our calculations but is clearly unrealistic") and of the TLB model in general.

    I like the idea of non-constant bang time he uses. It would be interesting to know if this fits with ideas such as eternal inflation.

    Finally, thanks for pointing out yet another paper that falsifies your claim that scientists are too scared or not allowed to investigate alternative cosmological models. This is a very active area of research, mainly because of the interesting unsolved problems.
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  8. #7  
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    Moved to Pseuo.

    Joe you've chosen to ignore the last warning. This time you're getting a week off to reconsider that action.
    Last edited by Lynx_Fox; May 14th, 2014 at 02:16 PM.
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  9. #8  
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    Quote Originally Posted by Lynx_Fox View Post
    Moved to Pseuo.

    Joe you've chosen to ignore the last warning. This time your getting a week to reconsider that action.
    Actually Lynx I do find this a bit harsh. All he was actually doing in this thread was discuss void models of cosmology, which is fair enough (and actually both new and interesting to me personally). I agree we all know he has an agenda, but so long as that agenda does not intrude into the thread, I'd have thought myself we could discuss whether these models are still a live possibility and so on, purely as a matter of hard science.

    But you're the Mod. of course.
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  10. #9  
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    Quote Originally Posted by exchemist View Post
    Quote Originally Posted by Lynx_Fox View Post
    Moved to Pseuo.

    Joe you've chosen to ignore the last warning. This time your getting a week to reconsider that action.
    Actually Lynx I do find this a bit harsh. All he was actually doing in this thread was discuss void models of cosmology, which is fair enough (and actually both new and interesting to me personally). I agree we all know he has an agenda, but so long as that agenda does not intrude into the thread, I'd have thought myself we could discuss whether these models are still a live possibility and so on, purely as a matter of hard science.

    But you're the Mod. of course.
    Ok fair enough. It seems a few of you think this might become a productive conversation so I'm moving it back to astronomy.

    I'm reducing Joe's suspension to a day for ignoring the warning not to start another thread so obviously related to his agenda to push pseudoscience. We will continue to monitor.
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  11. #10  
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    Quote Originally Posted by Lynx_Fox View Post
    Quote Originally Posted by exchemist View Post
    Quote Originally Posted by Lynx_Fox View Post
    Moved to Pseuo.

    Joe you've chosen to ignore the last warning. This time your getting a week to reconsider that action.
    Actually Lynx I do find this a bit harsh. All he was actually doing in this thread was discuss void models of cosmology, which is fair enough (and actually both new and interesting to me personally). I agree we all know he has an agenda, but so long as that agenda does not intrude into the thread, I'd have thought myself we could discuss whether these models are still a live possibility and so on, purely as a matter of hard science.

    But you're the Mod. of course.
    Ok fair enough. It seems a few of you think this might become a productive conversation so I'm moving it back to astronomy.

    I'm reducing Joe's suspension to a day for ignoring the warning not to start another thread so obviously related to his agenda to push pseudoscience. We will continue to monitor.
    Thanks for your understanding Lynx. I'm not sure how much further this discussion will go, but there are a couple of references to good papers, or write-ups of recent findings, which could come in handy and it would be hard to remember to search pseudoscience to find them.
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