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Term for 4D universe

  1. Mar 20, 2009 #1
    What is the name of the theory (or person who thought it up) that the universe is infinite in the 4th spatial dimension and that our big bang is only a local effect?
     
  2. jcsd
  3. Mar 21, 2009 #2

    Chalnoth

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    Er, there are a wide variety of hypotheses that have postulated this. What you've written is not specific enough to pick out any one hypothesis/theory.

    Minor nitpick, though: so far as we know, there is no fourth spatial dimension. The fourth dimension is time.
     
  4. Mar 26, 2009 #3
    What you've written is not specific enough to pick out any one hypothesis/theory.


    Is there one theorist, in this area, that is particular accessible to the non professional?
     
  5. Mar 26, 2009 #4

    Wallace

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    I think you are mixing different concepts from different ideas. There is one idea known as 'Braneworlds' that suggests the existence of an extra large scale dimension (the 4D 'bulk') an out Universe is a 3D 'Brane' on this 4D surface. It is not an idea that says the Big Bang is a local effect though, it is a proposal to understand the nature of dark energy.

    Sean Carroll is a theoretical cosmologists who has a lot of interesting ideas about how what we call the Big Bang could have emerged from some large picture. You could look him up for some ideas in this area (though there are plenty of other theorists and theories in this area as well). As far as I know Sean hasn't written anything on 4D universes though.
     
  6. Mar 26, 2009 #5

    marcus

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    There are several theorists who have cooked up eternally proliferating universe concepts and written accessibly for the non-specialist (to a greater or lesser extent.)

    Roger Penrose has a lecture where he illustrates his idea with colorful cartoon drawings.
    He gave the talk several times and it is online several places including Cambridge. I can't say I understand it. Charming puzzling and provocative. Ask if you want link.

    Andrei Linde has an idea of eternally proliferating local inflation spots that each turn into expanding universe regions. He wrote an illustrated Scientific American piece about this. I don't like it but it corresponds to what you asked. The universe is like a metastasizing cancer. It is called chaotic inflation or eternal inflation. There is no way to verify it observationally---it's just a fantasy that either appeals to you or not. No way to test.

    Lee Smolin has his idea of a locally proliferating eternal universe. Called CNS or cosmic natural selection. New big bang regions emerge out the other side of the black holes that form in prior regions. So it is local, and the whole picture is like a branching tree. Our region is an offshoot from a previous one, which is an offshoot from an even earlier.
    He wrote a book for lay readers about this called The Life of the Cosmos.

    There are plenty of others.
    ==========================

    BTW I wasn't sure what you meant by local. You might get more focused responses if you would simply use more words. Talk more about what you have in mind.

    There are a whole bunch of eternal universe models currently being studied. Models which go back before the big bang and suggest mechanisms by which our particular big bang might have occurred. Some of them are cyclic---a series of repeating big bang events. Others are proliferating, like a branching evolutionary tree. There is a book coming out this year that tries to assemble articles by 20 or so different authors and cover the whole menu, or menagerie, of this kind of eternal cosmology. I don't recommend the book. I looked at the table of contents and it just seemed like too much. Completely inclusive. Unselective. But maybe that's good. You can take a look and decide for yourself. The table of contents is online. The editor is Rudy Vaas. The title is
    Beyond the Big Bang: Prospects for an Eternal Universe
    Here's the general description
    http://www.springer.com/astronomy/general+relativity/book/978-3-540-71422-4 [Broken]
    Here's the table of contents
    http://www.springer.com/astronomy/general+relativity/book/978-3-540-71422-4?detailsPage=toc [Broken]
    The publisher now says they plan to have it out by October 4, 2009.
    I believe them, but the book has been delayed several times in the past.
     
    Last edited by a moderator: May 4, 2017
  7. Mar 26, 2009 #6
    I read in another thread in this forum, sorry don't remember wich one or who said it. but the gist of it was that a 4th spacial dimension would cause planetary orbits to be unstable. I don't know if that's true or not. Maybe someone a lot smarter than me, could comment on that? And would a 4th spacial dimension cause gravity to be different from what we observe?

    Also this gets me thinking of the Copernican principle, can it be aplied to the universe as a whole? well, ok, I guess there's no answer to that but I like to think there is.
     
  8. Mar 26, 2009 #7

    marcus

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    In newton terms, spatial 4D would cause the force of central gravity to fall off with the cube of distance rather than with the square.

    And by the way the brightness of light would dim down faster too (as the cube as well)

    Probably the business about stability can be intuitive. Without doing the math, if you were exactly on a precise circle orbit around the sun it would be OK as long as you stayed there. But if you accidentally veered in closer, the strength of pull would increase much more sharply. An inverse cube law is more drastic than inverse square. Be glad we're spatial 3D.
     
  9. Mar 26, 2009 #8
    I quote from THE UNIVERSE IN A NUTSHELL by Stephan Hawkins
    "on the other hand, if there were four or more nearly flat directions, the gravitational force between two bodies increase more rapidly as they approached each other.This would mean that planets would not have stable orbits about their suns.they would either fall into the sun or escape to the outer darkness and cold.
    Similarly the orbits of electrons in atoms would not be stable."

    this is explained by marcus of course.
    but here i have a question to you marcus since u know a bit more than me.

    wouldn't a 4-D( 5-D with time) universe allow for a 2-D orbit.instead of circular orbits there can be a famlily of orbits in the 2-D space enveloped in 2-D.I cannot imagine this as much as i can't imagine a 4-d space but something like this exists, wouldn't gravity be divided by the radius r^(3/2)
     
  10. Mar 26, 2009 #9

    marcus

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    for me, that's an unexpected idea. I never asked myself that, and I don't know.
    Maybe one of the others here knows the answer. I suppose you are talking about the hydrogen atom, where the electron can spread out. Planets follow 1-dimensional curve paths so a planet wouldn't have a 2D orbit.

    You might go to Quantum Theory forum and start a thread and ask.
    Like for example:

    "Atoms in four spatial dimensions
    Could something like a hydrogen atom be stable in 4 spatial dimensions?
    This quote from Stephen Hawking seems to suggest not. Can anyone explain?"

    I don't guarantee you'd get results, but I think it's worth a try. Sorry I can't help.
     
  11. Mar 27, 2009 #10
    thank you for answering my thread.
    i only have to correct that i meant to say IF something like this exists and not that they do.
    I thought up the idea myself i was not thinking about the electronic cloud in hydrogen but rather the fact that an extra dimension should in principle give different laws than our 3-D model and new phenomena that are unthinkable but may be applicable in such universes.

    again thanks for the help!!
     
  12. Mar 27, 2009 #11
    this is not my thread though so sorry Pjpic
     
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