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Thread: Can dark matter be an unobservable potential energy?

  1. #1 Can dark matter be an unobservable potential energy? 
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    Can dark matter be an unobservable potential energy, and not matter? or does it have to be some sort of matter?
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    Quote Originally Posted by David Hawkins View Post
    Can dark matter be an unobservable potential energy, and not matter? or does it have to be some sort of matter?
    No. Energy itself is not a physical quantity. Matter, by definition, is something for which the stress-energy-momentum (SEM) tensor is non-zero. Since the SEM tensor is the source of dark energy it's not possible for it to be zero. If it was zero there'd be no dark matter whatsoever.
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    We I believe are still somewhat in the dark about this, but I think that dark matter is thought to exhibit pull on observable matter and dark energy to exhibit a sort of something that causes spatial expansion. Dark Energy vs. Dark Matter - HETDEX
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    Unobservable potential energy? Would that mean some extended field rather than some particles? I've seen speculations that dark matter is some Bose-Einstein condensate of something, but it's hard to get a BEC to have the observed properties of dark matter, like its clustering.
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    Quote Originally Posted by mayflow View Post
    We I believe are still somewhat in the dark about this, but I think that dark matter is thought to exhibit pull on observable matter and dark energy to exhibit a sort of something that causes spatial expansion. Dark Energy vs. Dark Matter - HETDEX
    To be precise, it causes the expansion to accelerate. Cosmological expansion was known to exist before dark energy was around. When it was found that the rate of expansion was accelerating did we realize that something was causing gravitational repulsion and that's when dark energy was postulated to exist.
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    Quote Originally Posted by Physicist
    be precise, it causes the expansion to accelerate. Cosmological expansion was known to exist before dark energy was around. When it was found that the rate of expansion was accelerating did we realize that something was causing gravitational repulsion and that's when dark energy was postulated to exist.
    - ps can someome make the quote button work for me so I don't have to keep bothering to use HTML?

    I don't think we know this yet Mr Physicist as it may be true that dark energy was not postulated by science until much later (it may yet prove to be proof of Einstein's "cosmological constant", which he apparently chose to think was a mistake on his part) Just because we did not postulate these possibilites earlier, does not mean they did not exist then. Dark Energy, Dark Matter - NASA Science
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    Quote Originally Posted by mayflow View Post
    - ps can someome make the quote button work for me so I don't have to keep bothering to use HTML?
    Double-click on the quote button. That's the current workaround.

    I think you've misunderstood what Physicist meant. He is not saying that dark energy did not exist until recently. He is saying that only recent observations (dating back to around 1997 when Saul Perlmutter's team looked at Sn1a data in detail) compelled us to invoke dark energy as an explanation.
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    Quote Originally Posted by tk421 View Post
    Double-click on the quote button. That's the current workaround.

    I think you've misunderstood what Physicist meant. He is not saying that dark energy did not exist until recently. He is saying that only recent observations (dating back to around 1997 when Saul Perlmutter's team looked at Sn1a data in detail) compelled us to invoke dark energy as an explanation.
    Thanks Tk!
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    Quote Originally Posted by tk421
    I think you've misunderstood what Physicist meant. He is not saying that dark energy did not exist until recently. He is saying that only recent observations (dating back to around 1997 when Saul Perlmutter's team looked at Sn1a data in detail) compelled us to invoke dark energy as an explanation.
    That is precisely correct. Thanks for clearing that up for me.
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