Results 1 to 26 of 26

Thread: Einstein's Cosmological Constant Predicts Dark Energy

  1. #1
    Join Date
    Jul 2003
    Posts
    28,024

    Einstein's Cosmological Constant Predicts Dark Energy

    SUMMARY: Researchers are finding that the mysterious dark energy found to be accelerating the expansion of the Universe is remarkably well predicted by Einstein's cosmological constant. Einstein originally added this constant to balance out the gravitation of the Universe, but threw it out after seeing evidence of the Big Bang. An international team of researchers has performed the Supernova Legacy Survey, and found that it calculates dark energy to be within 10% of Einstein's prediction.

    View full article
    What do you think about this story? post your comments below.

  2. #2
    Join Date
    Nov 2002
    Posts
    6,208
    Hmmmmm, I predict most of those people who think that dark energy is some sort of magic, brought in to "save" the "dogma" of the BB will blow off these results as flawed and go back to pushing their own pet theories that can't, quantatively (if they can even produce a number), predict a match to within even 50%.

  3. #3
    Join Date
    Nov 2005
    Posts
    3

    Einstein's prediction?

    I thought Einstein's cosmological constant predicted a static universe, not an accelerating expanded one? I thought that was the whole idea? How can we say observations confirm his prediction, when his prediction was for an unchanging universe? If he were alive today, I think he would concede his greatest blunder would still be his greatest blunder...after all without it, doesn't general relativity predict expansion? With a cosmological constant you could accelerate the expansion (which is what is actually happening), stop the expansion (which is what Einstein chose the value of his constant to do) or slow the expansion I presume. Can anyone shed some starlight on this?

  4. #4
    Join Date
    Oct 2004
    Posts
    89
    I thought the big E used the constant in an effert to prevent collapse... I suppose I was way off.

  5. #5
    Join Date
    Nov 2005
    Posts
    4

    cosmological constant(CC)

    It is true that Einstein originally postulated the CC on the assumption that the Universe was static. However, the constant had a specific value. What the supernova researchers are saying is that specific value applied to dark energy is the right value to account for the rate at which dark energy is now accelerating the expansion of the universe.

    To look at it another way, the constant originally was a pressure constant needed to prevent the universe from collapsing from gravity, thus preserving the assumed static universe at the time. Now since we know that the universe is expanding instead of being static, this constant pressure is causing the expansion to accelerate by the amount of the value of Einstein's constant. Wheter that is indeed being caused by dark energy or something else, the researchers are saying that the value of the constant is the right value to account for the observed expansion rate.

  6. #6
    Join Date
    Nov 2003
    Posts
    6,196
    Quote Originally Posted by Brett
    I thought Einstein's cosmological constant predicted a static universe, not an accelerating expanded one? I thought that was the whole idea?
    That's exactly right. There was no evidence of an expanding or contracting universe when Einstein added the constant, which was a single symbol. The constant was supposed to be a general term that would keep the universe from expanding or contracting, in spite of gravity. It had no particular numerical value.

    This was an old problem that went back to Newton's time. The question was, if the universe was finite, then why didn't it collapse due to all the gravity?

    Newton proposed several ideas: 1) that it was collapsing but we couldn't detect that with the early telescopes, 2) that it was expanding due to some initial "projectile force" at the beginning of the universe, but we couldn't detect the expansion with the early telescopes, and 3) that it was static but only if the universe were infinite in size.

    I've got an 1803 astronomy book that talks about this problem and about the possibility of an expanding or contracting universe.

    Edgar Allen Poe wrote an essay about it in 1848:

    http://xroads.virginia.edu/~HYPER/poe/eureka.html

    Einstein decided to try to explain what he thought was a non-expanding and non-contracting universe with some 19th Century 4-D geometry theories and he needed to add his cosmological consant for that. The constant was no more than saying something like, "The X factor keeps the universe static, in spite of all the gravity of all the stars."

  7. #7
    Join Date
    Nov 2003
    Posts
    6,196
    Quote Originally Posted by Maxgammon
    It is true that Einstein originally postulated the CC on the assumption that the Universe was static. However, the constant had a specific value.
    What value was it? I haven't been able to find any numerical value for it. I think the numerical value would depend on how large the universe was, how much mass it had and how far the stars were away from each other. But if you know a "value" for the constant, please let me know what Einstein said it was.

    Thanks.

  8. #8
    Join Date
    Nov 2003
    Posts
    6,196
    Quote Originally Posted by Dark Jaguar
    I thought the big E used the constant in an effert to prevent collapse... I suppose I was way off.
    No, you are correct. At the time he developed the idea, no one knew the Universe was expanding, and he tried to explain how it could remain static and not collapse if it were finite in size and mass. He did the correct thing in proposing the constant. This was his idea of what might keep the universe from collapsing if it was finite. Later it was learned that the universe is expanding, so he no longer needed the constant.

  9. #9
    Join Date
    Mar 2005
    Posts
    61
    Quote Originally Posted by Sam5
    What value was it? I haven't been able to find any numerical value for it. I think the numerical value would depend on how large the universe was, how much mass it had and how far the stars were away from each other. But if you know a "value" for the constant, please let me know what Einstein said it was.

    Thanks.
    I believe they are claiming dark energy behaves like Einsein's cosmological constant, it doesn't change with time, not that it is within 10% of the value he used.

  10. #10
    Join Date
    Nov 2005
    Posts
    3

    Cool Universe posting Bad Astronomy?

    Thanks to all, especially Sam5 for your answers. A couple of follow up questions for the brains trust:
    The preprint of the original article is here: http://xxx.lanl.gov/PS_cache/astro-p...10/0510447.pdf

    The article posted on Universe might be nominated for 'Bad Astronomy' actually Having (albeit quickly) read through the original paper, there is not one mention of Einstein or the 10% figure. I don't know where that comes from. I don't think the authors of the original paper mention Einstein even once. The author of the article however takes a bit of liberty and does though.

    The article says "An international team of researchers has performed the Supernova Legacy Survey, and found that it calculates dark energy to be within 10% of Einstein's prediction."

    It seems to me the closest they get to mentioning 10% is that the error in their measurement of the equation of state, w is 0.09 or 9%. I think the author of the article, and not the authors of the paper have beaten this up a bit by mentioning Einstein. Sure, he came up with the idea for a cosmological constant: but this article no more confirms that he was right to within 10% or any figure anymore than any cold dark matter-dark energy model does. Such articles mentioning confirming instances of Einstein create interest: especially as the article is a press release for a University...those guys are notorious for putting spin on things.

    That's my 5cents.

  11. #11
    Join Date
    Nov 2003
    Posts
    6,196
    Quote Originally Posted by Brett
    Thanks to all, especially Sam5 for your answers. A couple of follow up questions for the brains trust:
    The preprint of the original article is here: http://xxx.lanl.gov/PS_cache/astro-p...10/0510447.pdf

    The article posted on Universe might be nominated for 'Bad Astronomy' actually Having (albeit quickly) read through the original paper, there is not one mention of Einstein or the 10% figure. I don't know where that comes from. I don't think the authors of the original paper mention Einstein even once. The author of the article however takes a bit of liberty and does though.

    The article says "An international team of researchers has performed the Supernova Legacy Survey, and found that it calculates dark energy to be within 10% of Einstein's prediction."

    It seems to me the closest they get to mentioning 10% is that the error in their measurement of the equation of state, w is 0.09 or 9%. I think the author of the article, and not the authors of the paper have beaten this up a bit by mentioning Einstein. Sure, he came up with the idea for a cosmological constant: but this article no more confirms that he was right to within 10% or any figure anymore than any cold dark matter-dark energy model does. Such articles mentioning confirming instances of Einstein create interest: especially as the article is a press release for a University...those guys are notorious for putting spin on things.

    That's my 5cents.
    I think you are right. When I first started studying Einstein, about 15 years ago, about all I had to study were a few of his classic papers but mostly I had all the popular articles about him that said "Einstein predicted" this or that and others that said "Einstein claimed" this or that. Later I found the Princeton series of books containing translations of almost all of his papers, and many of them were papers that were never published in English until the 1980s and '90s. In many of those papers I saw that Einstein himself was much more cautious about making predictions and claims, and he willingly corrected some of his earlier errors and speculations, such as the cosmological constant.

    And as I read modern articles and papers about new theories, I noticed that a lot of guys use Einstein's name improperly, claiming basically that "Einstein would support my new theory because....." Whereas I believe Einstein would have actually laughed at some of the new papers and theories. I think too many people want to promote their favorite new theories by claiming that "Einstein predicted this," when in reality, he didn't "predict" it at all, and if he were alive today he might object to many of the new theories and he might be able to point out how they are wrong and what is the correct solution to some of the modern mysteries. When we get someone like Einstein in our world, it's too bad that he doesn't live for 200 or more years so he can work on some of these modern problems and figure out the correct solutions.

    Too bad we don't have both Newton and Einstein working together today. I think they would agree on a lot of issues and could solve some of the modern cosmology problems.

  12. #12
    Join Date
    Mar 2005
    Posts
    1,846
    An interesting link:




    http://super.colorado.edu/~michaele/Lambda/blund.html



    Titana........

  13. #13
    Join Date
    Aug 2003
    Posts
    585
    The cosmological constant has a value?
    I would love to hear what that might be. I doubt the authors of the paper are aware of it either. I thought the Hubble constant was an attempt to describe the value (or rate) of expansion of the universe related to redshift. And that is still an estimate or guess.

  14. #14
    Join Date
    Jan 2003
    Posts
    302
    Quote Originally Posted by Greg
    The cosmological constant has a value?
    I would love to hear what that might be. I doubt the authors of the paper are aware of it either. I thought the Hubble constant was an attempt to describe the value (or rate) of expansion of the universe related to redshift. And that is still an estimate or guess.
    according to this page, by Sean Carroll
    http://pancake.uchicago.edu/~carroll/encyc/
    the CC has a value of

    L= (8*Pi*G)/(3*c*c)*d

    d is the vacuum energy density

  15. #15
    Join Date
    Sep 2005
    Posts
    121
    Hi,

    I think that the entire debate on dark energy requires a careful examination of the facts on which the idea of dark energy is based. Otherwise, it might turn out that the darkness of this energy is mainly some sort of darkness within heads. People have faith in the trustworthiness of science. They should not feel like being cheated.

    As far as i recall, Einstein invented the cosmological constant as a means to explain why the universe does not collapse due to the pull of gravity which acts between its components. (If you find that you are living in a universe where certain forces are acting, it is essential that you explain why these forces do not crunch it. So, there must be a force to balance the pull of gravity, as otherwise everything would end up in a big crunch, and that was an idea Einstein did not like.)
    Later, as Hubble found that the universe expands, Einstein dropped the idea of a cosmological constant, as the facts showed that it was not required any more in his concepts.

    A couple of years ago, astrophycisists found that supernovae of type I that exploded billions of years ago and thus billions of light years away appeared to be a bit brighter than they should be for the distances found from their redshifts. This puzzling phenomenon was explained by a recent acceleration of space expansion, and the idea was developed that this acceleration of space expansion was caused by a mysterious dark energy which is thought to act just like Einstein´s cosmological constant.

    Supernovae of type 1 are explained to be caused by an explosion of a White Dwarf which takes place when the mass of this White Dwarf exceeds Chandrasekhar´s mass limit, which defines the maximum mass a White Dwarf may have. As it is always the same mass that explodes when a supernova type 1 occurs, the brightness of every single supernova explosion of that type is considered to be of the same value. This being true, every supernova of that type at a certain distance must offer a certain, predictable brightness. If the brightness doesn´t match the distance found by examining the red shift of the supernova´s light, the expansion of space must have increased since this supernova took place.

    Some years ago I read a report that simulations of supernovae of type I revealed that the emission produced by that type of supernova is not of the same value in every direction. There may be differences of brightness dependind on the direction from where you look at the supernova. The same supernova may differ in brightness for observers at same distances as they observe from different directions.
    Plainly said: There are indications that you do not need dark energy to explain why distant supernovae of type I appear too bright for their distance. This must be checked and solved.

    Energy cannot come from nothing. If you have energy, you must explain where it comes from. If you have dark energy, it is necessary to explain what it is, and what is its source.
    The world and the universe is something that is real. It is amazing and it is extraordinary, but it is nothing of fiction and phantasy. If we have dark energy, we must strip it from fiction and prove its reality.
    Or drop it.

    Regards,

    Günther

  16. #16
    Join Date
    Mar 2005
    Posts
    1,846
    Quote Originally Posted by iron4
    according to this page, by Sean Carroll
    http://pancake.uchicago.edu/~carroll/encyc/
    the CC has a value of

    L= (8*Pi*G)/(3*c*c)*d

    d is the vacuum energy density
    Just incase nobody looked at the link above, i would have to say it is quite worth looking at. Especially the part about Observational Prospects.


    Titana......

  17. #17
    Join Date
    Nov 2003
    Posts
    6,196
    Quote Originally Posted by GBendt
    As far as i recall, Einstein invented the cosmological constant as a means to explain why the universe does not collapse due to the pull of gravity which acts between its components. (If you find that you are living in a universe where certain forces are acting, it is essential that you explain why these forces do not crunch it. So, there must be a force to balance the pull of gravity, as otherwise everything would end up in a big crunch, and that was an idea Einstein did not like.)
    Later, as Hubble found that the universe expands, Einstein dropped the idea of a cosmological constant, as the facts showed that it was not required any more in his concepts.

    Here is a brief discussion of this problem in an 1803 astronomy book that I have. It is titled “Natural Theology”, by William Paley, Arch-Deacon of Carlisle. In those days some well-educated religious leaders wrote science books. Paley got some of these ideas from Newton, principally from some of Newton’s letters, which were available in book form in the early 1800s. Many of Newton’s letters contained speculations that he didn’t want to include in his science books, because the ideas were too speculative.

    From the 1803 book:

    “But many of the heavenly bodies, as the sun and fixed stars are stationary. Their rest must be the effect of an absence or of an equilibrium of attractions. It proves also that a projectile impulse was originally given to some of the heavenly bodies, and not to others. But further; if attraction act at all distances, there can be only one quiescent center of gravity in the universe: and all bodies whatever must be approaching this center, or revolving around it. According to the first of these suppositions, if the duration of the world had been long enough to allow it, all its parts, all the great bodies of which it is composed, must have been gathered together in a heap round this point.”

  18. #18
    Join Date
    Nov 2005
    Posts
    3
    Scientific American has picked it up now, with this quote "The researchers also plugged this data into a so-called equation of state, which measures the relationship between pressure and density, and found that dark energy must be less than -0.85--awfully close to Einstein's cosmological constant at -1. " So they say. Have a look at the article http://www.sciam.com/article.cfm?cha...7FFE87&ref=rss

    So according to SCIENTIFIC AMERICAN now, Einstein's cosmological constant was -1. What's all that about?

  19. #19
    Join Date
    Jan 2003
    Posts
    302
    Quote Originally Posted by Brett
    Scientific American has picked it up now, with this quote "The researchers also plugged this data into a so-called equation of state, which measures the relationship between pressure and density, and found that dark energy must be less than -0.85--awfully close to Einstein's cosmological constant at -1. " So they say. Have a look at the article http://www.sciam.com/article.cfm?cha...7FFE87&ref=rss

    So according to SCIENTIFIC AMERICAN now, Einstein's cosmological constant was -1. What's all that about?
    -1 is the value of the dark energy equation of state for the cosmological constant, not the value of the cosmological constant

  20. #20
    Join Date
    Nov 2003
    Posts
    6,196
    Quote Originally Posted by Brett
    Scientific American has picked it up now, with this quote "The researchers also plugged this data into a so-called equation of state, which measures the relationship between pressure and density, and found that dark energy must be less than -0.85--awfully close to Einstein's cosmological constant at -1. " So they say. Have a look at the article http://www.sciam.com/article.cfm?cha...7FFE87&ref=rss

    So according to SCIENTIFIC AMERICAN now, Einstein's cosmological constant was -1. What's all that about?
    Einstein’s introduction of the cosmological constant was in his 1917 paper, “Cosmological Considerations on the General Theory of Relativity.” The paper is published in English in the standard Dover paperback edition of “The Principle of Relativity”. It starts on page 177. The constant is introduced on page 179.

    The symbol he used for the constant was λ. He said in the paper λ = 1/R^2. He said about R, “The points of this hyper-surface form a three-dimensional continuum, a spherical space of radius of curvature R.” He also said, “The term is necessary only for the purpose of making possible a quasi-static distribution of matter, as required by the fact of the small velocities of the stars.”

  21. #21
    Join Date
    Nov 2003
    Posts
    6,196
    Here is Einstein’s 1932 paper in which he withdrew the constant:

    http://tinypic.com/hvny95.jpg

  22. #22
    Join Date
    Jan 2003
    Posts
    302
    Quote Originally Posted by Sam5
    Here is Einstein’s 1932 paper in which he withdrew the constant:

    http://tinypic.com/hvny95.jpg
    I've added it to my favourites, it's better to learn these things straight from the horse's mouth, not from articles that can contain errors

  23. #23
    Join Date
    Aug 2003
    Location
    The Wild West
    Posts
    9,439
    Quote Originally Posted by iron4
    according to this page, by Sean Carroll
    http://pancake.uchicago.edu/~carroll/encyc/
    the CC has a value of

    L= (8*Pi*G)/(3*c*c)*d

    d is the vacuum energy density
    Quote Originally Posted by Titana
    Just incase nobody looked at the link above, i would have to say it is quite worth looking at. Especially the part about Observational Prospects.
    Quite right, Titana. That page was very well composed.

    I concur with those who said that Einstein's cosmological constant (lambda) did not take a particular value. As I understand it, it was designed to take whatever value was needed to counter the gravity inherent in all the galaxies, etc. of the universe, which was not particularly well known in Einstein's time. As Harvard GR prof. Tony Rothman says, even Einstein's equations in general "do not specify the universe; rather they may be considered a general framework within which you can construct many different model universes."

    I think this also answers Brett's question....
    Quote Originally Posted by Brett
    How can we say observations confirm his prediction, when his prediction was for an unchanging universe?
    Such scientific "predictions" are not so much spoken "prophecies" that "come true" but rather they're often novel or specific solutions to (equations that allow many answers, depending on the parameters). Einstein developed the general equations, and many others have found specific "predictions" inherent in those equations, some that apparently Einstein didn't even foresee.
    Everyone is entitled to his own opinion, but not his own facts.

  24. #24
    Join Date
    Nov 2003
    Posts
    6,196
    Quote Originally Posted by iron4
    I've added it to my favourites, it's better to learn these things straight from the horse's mouth, not from articles that can contain errors
    Yes, I agree.

    You might want to copy that one-page paper to hard drive, because the tinypic service I used to post it will delete it in a couple of months.

  25. #25
    Join Date
    Nov 2003
    Posts
    6,196
    Some of you math-oriented guys and gals might enjoy studying some of the first 19th Century papers about "curved space". This is where Einstein got some of his ideas from, regarding the universe.

    Here is a simple article by Arthur Cayley, first published in 1884:

    http://www.hti.umich.edu/cgi/t/text/...=image&seq=237

  26. #26
    Join Date
    Mar 2005
    Posts
    1,846
    Quote Originally Posted by Sam5
    Some of you math-oriented guys and gals might enjoy studying some of the first 19th Century papers about "curved space". This is where Einstein got some of his ideas from, regarding the universe.

    Here is a simple article by Arthur Cayley, first published in 1884:

    http://www.hti.umich.edu/cgi/t/text/...=image&seq=237


    Very interesting, Thanks......




    Titana.......

Similar Threads

  1. Replies: 1
    Last Post: 2009-May-07, 03:31 PM
  2. Replies: 20
    Last Post: 2008-Dec-25, 01:11 AM
  3. Has Dark Energy Always Been Constant?
    By Fraser in forum Universe Today
    Replies: 0
    Last Post: 2007-Oct-12, 03:31 PM
  4. Einstein's Cosmological Constant
    By Fr. Wayne in forum Space/Astronomy Questions and Answers
    Replies: 14
    Last Post: 2006-Jan-16, 11:18 PM
  5. Dark Energy Could be a Breakdown of Einstein's Theory
    By Fraser in forum Universe Today
    Replies: 0
    Last Post: 2005-Sep-06, 09:07 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •