chrunchy! Posted November 15, 2005 Share Posted November 15, 2005 Hi, Im currently doing a project on the multiverse and i would like to hear what everyone else has to say about this theory. It'll be great if someone could give me some helpful info or ideas on the project. thanks and enjoy! Link to comment Share on other sites More sharing options...
Martin Posted November 15, 2005 Share Posted November 15, 2005 Hi, Im currently doing a project on the multiverse and i would like to hear what everyone else has to say about this theory. It'll be great if someone could give me some helpful info or ideas on the project. thanks and enjoy! Max Tegmark had a popular article on this topic in the Scientific American a year or two back. It is online. Just google with "Tegmark Multiverse" and you will probably find it. Personally I don't like the article, but Tegmark is a worldclass astronomer/cosmologist guy (as well as a vivid writer)---so your teacher(s) will probably accept this as a reliable source. I think that Tegmark SciAm article is the ground floor----personal feeling is it is mostly garbage but it's where you have to start because it outlines the domain of discussion in popular colorful language. After that, it is a question of how high up the technical ladder you want to climb. There is only one Multiverse theory that I know of that actually makes TESTABLE PREDICTIONS about astronomical observations. In other words it is not just some nice mathematical fantasy, it predicts what will or will not be observed and so at any step along the way it may either pass the test or it may turn out WRONG. For me this kind of predictiveness that lets it be tested (so it risks being wrong) is the hallmark of a scientific theory. So all the usual multiverse theories, including string theory multiverses, because they are not predictive, are not very interesting. Nothing that Tegmark's SciAm article talks about makes testable predictions. The only PREDICTIVE multiverse theory I know of is discussed in Smolin's book The Life of the Cosmos (search with amazon, or with google) and in a more technical article that appeared last year Scientific Alternatives to the Anthropic Principle (this is due to be published by Cambridge University Press soon in a collection of essays on the multiverse issue by various writers) http://arxiv.org/abs/hep-th/0407213 Scientific alternatives to the anthropic principle Author: Lee Smolin Comments: Contribution to "Universe or Multiverse", ed. by Bernard Carr et. al., to be published by Cambridge University Press The villains in my world are prestigious old physicists who have failed to come up with satisfactory explanations of some features of the cosmos and don't think anyone else can (at least with string theory which is increasingly seen to not be working out as expected) and so they advocate GIVING UP ON PREDICTIVITY. Steven Weinberg is a case in point. His essay Living with the multiverse will discourage people from finding explanations for why the universe has to be the way it is-----he did great work in the 1970s and has a huge reputation, but is himself discouraged now, so he communicates the sense that "well that's just how it is, there's lots of possibilities and we just happen to live in this version of how it could be, so give up trying to explain already!" But the highly respected senior people who are spreading this message are doing so at just the wrong time, because younger less-well-known people are beginning to find physical models explaining how some basic numbers turn out to be what they are---there are some testable models uniting gravity and particle physics in the works. Now is not the time to be giving up on this 400 year old quest to get a mathematical explanation of the world. It is really bad luck that some huge reputation like Steven Weinberg and the string theorist Leonard Susskind (both now quite old) should just now be spreading this defeatist multiverse message ----- "that's how it is, dont try to explain how our version comes about, it's just the way it is, live with it." Yuk. Here is Steven Weinberg's paper, perfect example of the type of multiverse thinking that I think is so unfortunate: http://arxiv.org/abs/hep-th/0511037 Living in the Multiverse Author: Steven Weinberg Comments: 13 pages Report-no: UTTG-12-05 This is the written version of the opening talk at the symposium "Expectations of a Final Theory," at Trinity College, Cambridge, on September 2, 2005. It is to be published in Universe or Multiverse?, ed. B. Carr (Cambridge University Press). Link to comment Share on other sites More sharing options...
ecoli Posted November 16, 2005 Share Posted November 16, 2005 plenty of threads on this already... use the search functions Link to comment Share on other sites More sharing options...
chrunchy! Posted November 19, 2005 Author Share Posted November 19, 2005 Max Tegmark had a popular article on this topic in the Scientific American a year or two back. It is online. Just google with "Tegmark Multiverse" and you will probably find it. Personally I don't like the article' date=' but Tegmark is a worldclass astronomer/cosmologist guy (as well as a vivid writer)---so your teacher(s) will probably accept this as a reliable source. I think that Tegmark SciAm article is the ground floor----personal feeling is it is mostly garbage but it's where you have to start because it outlines the domain of discussion in popular colorful language. After that, it is a question of how high up the technical ladder you want to climb. There is only one Multiverse theory that I know of that actually makes TESTABLE PREDICTIONS about astronomical observations. In other words it is not just some nice mathematical fantasy, it predicts what will or will not be observed and so at any step along the way it may either pass the test or it may turn out WRONG. For me this kind of predictiveness that lets it be tested (so it risks being wrong) is the hallmark of a scientific theory. So all the usual multiverse theories, including string theory multiverses, because they are not predictive, are not very interesting. Nothing that Tegmark's SciAm article talks about makes testable predictions. The only PREDICTIVE multiverse theory I know of is discussed in Smolin's book [b']The Life of the Cosmos[/b] (search with amazon, or with google) and in a more technical article that appeared last year Scientific Alternatives to the Anthropic Principle (this is due to be published by Cambridge University Press soon in a collection of essays on the multiverse issue by various writers) http://arxiv.org/abs/hep-th/0407213 Scientific alternatives to the anthropic principle Author: Lee Smolin Comments: Contribution to "Universe or Multiverse", ed. by Bernard Carr et. al., to be published by Cambridge University Press The villains in my world are prestigious old physicists who have failed to come up with satisfactory explanations of some features of the cosmos and don't think anyone else can (at least with string theory which is increasingly seen to not be working out as expected) and so they advocate GIVING UP ON PREDICTIVITY. Steven Weinberg is a case in point. His essay Living with the multiverse will discourage people from finding explanations for why the universe has to be the way it is-----he did great work in the 1970s and has a huge reputation, but is himself discouraged now, so he communicates the sense that "well that's just how it is, there's lots of possibilities and we just happen to live in this version of how it could be, so give up trying to explain already!" But the highly respected senior people who are spreading this message are doing so at just the wrong time, because younger less-well-known people are beginning to find physical models explaining how some basic numbers turn out to be what they are---there are some testable models uniting gravity and particle physics in the works. Now is not the time to be giving up on this 400 year old quest to get a mathematical explanation of the world. It is really bad luck that some huge reputation like Steven Weinberg and the string theorist Leonard Susskind (both now quite old) should just now be spreading this defeatist multiverse message ----- "that's how it is, dont try to explain how our version comes about, it's just the way it is, live with it." Yuk. Here is Steven Weinberg's paper, perfect example of the type of multiverse thinking that I think is so unfortunate: http://arxiv.org/abs/hep-th/0511037 Living in the Multiverse Author: Steven Weinberg Comments: 13 pages Report-no: UTTG-12-05 This is the written version of the opening talk at the symposium "Expectations of a Final Theory," at Trinity College, Cambridge, on September 2, 2005. It is to be published in Universe or Multiverse?, ed. B. Carr (Cambridge University Press). wow! thanks for your opinion and info. ^^ Link to comment Share on other sites More sharing options...
chrunchy! Posted November 19, 2005 Author Share Posted November 19, 2005 plenty of threads on this already... use the search functions lol! i've already read them all, just wanted to start my own thread. Link to comment Share on other sites More sharing options...
ecoli Posted November 19, 2005 Share Posted November 19, 2005 lol! i've already read them all, just wanted to start my own thread. in that case, I'll shut the hell up. Most of what I know about multiverse theory (without entering the realm of theology) involves Youngs double slit experiment. If you don't know what that is, http://en.wikipedia.org/wiki/Youngs_double-slit_experiment Anyway, when the light source is diminished so that only one photon is allowed to enter the double slit, the photons behave exactly the same as if there were lots of photons allowed to go threw the slit. Proponents of the multiverse theory claim this is because the photons are interacting with photons from other universes. Link to comment Share on other sites More sharing options...
DV8 2XL Posted November 20, 2005 Share Posted November 20, 2005 An overview of the various theories can be found at: http://en.wikipedia.org/wiki/Multiverse Link to comment Share on other sites More sharing options...
danny8522003 Posted November 20, 2005 Share Posted November 20, 2005 Most of what I know about multiverse theory (without entering the realm of theology) involves Youngs double slit experiment. If you don't know what that is' date=' http://en.wikipedia.org/wiki/Youngs_double-slit_experiment Anyway, when the light source is diminished so that only one photon is allowed to enter the double slit, the photons behave exactly the same as if there were lots of photons allowed to go threw the slit. Proponents of the multiverse theory claim this is because the photons are interacting with photons from other universes.[/quote'] Isn't this something to do with the wave-particle duality of the photon? Electrons do this as well Also if universes collide in 11-dimensional space like in string theory, are those universes not part of an even greater universe? Link to comment Share on other sites More sharing options...
DV8 2XL Posted November 20, 2005 Share Posted November 20, 2005 Multiverse proponents are often vague about how the parameter values are selected across the defined ensemble. If there is a “law of laws” or meta-law describing how parameter values are assigned from one universe to the next, then we have only shifted the central problems of cosmology up one level, because we need to explain where the meta-law comes from. Moreover, the set of such meta-laws is infinite, so we have merely replaced the question “why this universe?” with “why this multiverse?”. There would seem to be little point in invoking an infinity of universes when it would be simpler to postulate a single universe with a single principle. In Tegmark’s extreme multiverse theory this problem is circumvented, because in that case all possible meta-laws (or all possible unified theories) are in force and describe really-existing multiverses Link to comment Share on other sites More sharing options...
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