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Help me understand Cosmological constant?

  1. Nov 30, 2009 #1
    What does this paragraph mean?

    I read it somewhere that a relatively newer observation renewed the concept of "cosmological constant", and it was connected with "dark energy", again, can anyone provide detailed information on that?

    Wasn't "cosmological constant" proved erroneous long ago?

    Or is it something are now being called "cosmological constant", something other than "cosmological constant" itself? What is it, then?

    How should I understand the word "economical" here?

    I know it may be quite difficult to answer my question since I got the experience when trying to explain something to an outsider about the concept withing my speciality, so I start by telling the inquisitor whatever pertinent. I'm not trying to "teach" you how to explain this issue in any fashion (if I did made you feel so, I apologize), rather, this is just a personal suggestion, because I do not even know this question I'm asking is hard to begin with or not.

    I hope my question is not so valueless. Any help will be appreciated, a paragraph, a link etc. Also, sorry for my english.
  2. jcsd
  3. Nov 30, 2009 #2


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    This seems a little out of context to me but I'll try to provide what insight I can. Einstein added the cosmological constant term into his field equations for one purpose: to produce a static universe. After the realization that the universe was expanding, he saw no need for the cosmological constant term, and it was discarded as an ad-hoc construction.

    When Dark Energy was discovered in the late 1990s, it is very convenient to formulate this extra repulsive force in exactly the same manner Einstein formulated his cosmological constant (an extra term in the field equations). However, the value is no longer cherry-picked to create a static universe, but is an experimentally measured value (I know of no successful theoretical predictions of its value).

    Does that make sense?
  4. Nov 30, 2009 #3

    Yes it does! Thanks Nabeshin!

    At least I know what "economical" means here. "If it's useful, get it back from the trashcan".

    Further discussion is encouraged!
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