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Alternate universe attractive/repeling force?

  1. May 29, 2009 #1
    Before I post the question, I must state for the record that I am a grunt so please be gentle with me. My question is this, Could altenate universes generate an attractive force on our own to speed our own expansion? Or a repeling force to aid contraction? Possibly other universes may have lumped our own during the big bang.
  2. jcsd
  3. May 29, 2009 #2


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    The fad for colliding brane cosmology, and string cosmology as a whole, seems to have passed. You should keep in mind that pretty much all the more bizarre multiverse scenarios were purely speculative---they offered no clear possibility of testing them and so were not science in the usual sense.

    String Landscape and multiverse topics were hot and now they're not. Here's a report on the change.

    The point is you can tell where the professional research interest is focusing by looking at the invited talks at the annual conferences. The relevant one here would be Strings 2009. Because in past years there has been a lot of string research and string-inspired research into scenarios or fantasies about our universe is a "brane" floating in a higherdimensional surround and maybe bumping other branes etc etc. And in past years there has been a lot of discussion of the almost infinite "landscape" of possible versions of physics "predicted" by string and the notion that they all might be realized in a huge multiverse, where only the habitable ones were inhabited etc etc.
    This year the annual Strings conference has none of that highly imaginative stuff.

    Same way last year. Strings 2008 ostracized the Landscape and Braneworld and Multiverse researchers. The organizers didn't invite them to talk.

    Other groups like Loop cosmologists were never interested in that stuff. So the people who were interested during the 2003-2007 fad years have now pretty much lost interest.
    So it goes. The public, which gets the fads thru popularizations (like Brian Greene books) is left holding an empty cage from which the bird of research has flown. So it goes.
    Last edited: May 29, 2009
  4. May 29, 2009 #3
    So the possibility is a fad. Like a hulahoop?
  5. May 29, 2009 #4
    Thanks for the links
  6. May 29, 2009 #5


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    Great analogy! :rofl:
    there is some guy who still does hulahoop on the hill up behind campus, a quarter mile or so from where we live. Skinny old hippy, very limber.

    We don't know what is real. But we can watch how the professional research community behaves. Ideas come and go. We can watch the indicators and gauge this. And try to explain and understand the trends.

    There are some physics reasons why the Landscape and the Multiverse have declined in hotness. I could try to go into that if you want. Probe possible physics reasons. Make some guesses. But only if you want.

    Maybe we should first wait and see if anyone hops in and wants to discuss those ideas. I'm telling you my take. Someone else may see it differently. Interesting topic. I have to go but will get back to this later tonight or tomorrow.
    Last edited: May 30, 2009
  7. May 30, 2009 #6


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    Marcus, I highly doubt that branes and the landscape are just passing fads. We will probably see all of these sorts of more speculative ideas die down significantly as the LHC turns up and we get some new results from there. But they'll come right back with the next lull in high energy experiment.

    And, on the off chance that experiments start to support some of these ideas, well, theorists won't have forgotten about them.
  8. Jun 3, 2009 #7
    See my post CYCLIC MODEL OF THE UNIVERSE ...A recent proposal by well know theorists...
    New ideas are almost always rejected or ignored by the majority....and often with good reason....but even general relativity took nearly 20 years to catch on....I think because most did not understand it's implications( even Einstein never believed in black holes and initially insisted on a static universe) and also because mathematical solutions were so difficult....
  9. Jun 6, 2009 #8


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    Naty we cannot know the future and everybody has their own vision what trends in research are important---so in a general sense about Steinhardt cyclic ("brane clash") cosmology you might be right!

    But let's get straight on details.

    The cyclic model is not recent. I think the big paper on it came out in 2002. In cosmology that is not recent (cosmology is a fast moving field).

    The cyclic model was not rejected or ignored. It got a huge amount of attention by researchers around 2002-2005. The original 2002 paper has gotten over 160 cites!

    General Relativity did not get ignored at first and have to wait in the wings for 20 years. It got immediate acclaim. The news came out in 1915 and by 1917 you had deSitter's universe, 1918 Schwarzschild derived the black hole solution, 1922 Friedman published his expanding universe cosmology model, the great Brit astronomer Eddington traveled to Africa to observe the 1919 eclipse so he could test General Relativity. (Any earlier expeditions would have been precluded by World War I.) I have seen newspaper headlines from around 1915-1919 and my impression is that GR got a lot of attention, funding for tests, professional acceptance and follow-up, and publication journal-space.

    You could counter that GR still has not been accepted because the Standard Particle Model is only using special, not general. Some branches of physics have been slow to adopt GR for one reason or another. But it received plenty of attention and study. And testing! A theory that has been tested as much as GR has cannot really complain.

    You draw an analogy between Steinhardt Cyclic and GR.

    There are differences. Steinhardt's interest in Cyclic seems to have declined after 2005, along with other people's.

    The original 2002-2005 flood of highly cited papers has tapered off, tended to peter out.

    There are reasons for this we could discuss.
  10. Jun 6, 2009 #9


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    Of course, the reason why quantum mechanics doesn't use GR is mathematical: quantum mechanics tends to fail when you try. This indicates that in order to really understand how what we know about GR impacts quantum mechanics, we need a quantum theory of gravity.

    By the way, though, people do sometimes work with quantum mechanics in curved space-time. There are just lots of problems with it.
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