Notices
Results 1 to 20 of 20
Like Tree7Likes
  • 2 Post By Markus Hanke
  • 1 Post By SpeedFreek
  • 1 Post By SpeedFreek
  • 1 Post By khaldac
  • 1 Post By Strange
  • 1 Post By SpeedFreek

Thread: What is the universe expanding into?

  1. #1 What is the universe expanding into? 
    Forum Freshman
    Join Date
    Dec 2013
    Location
    Ohio, U.S.
    Posts
    17
    Just wondering.


    Reply With Quote  
     

  2.  
     

  3. #2  
    Moderator Moderator Markus Hanke's Avatar
    Join Date
    Nov 2011
    Location
    Ireland
    Posts
    7,172
    The answer is that it is not expanding into anything. Current scientific understanding has it that the universe is either closed in itself, or infinite ( we have insufficient data to decide which one ), but in either case does not have a boundary. As such there is no "outside" to the universe, it is not embedded into any higher dimensional space into which it could expand. The metric expansion we observe is an intrinsic expansion; I understand that this is a highly counterintuitive notion for which there is no real everyday analogue, but be assured that the relevant concepts are all mathematically rigorous and well defined. Bear in mind also that the universe is actually a 4-dimensional construct, and as such is in fact static; all that really happens is that the geometry of that universe is slightly different at different points along the ( cosmological ) time axis - which is what we observe as metric expansion.


    Reply With Quote  
     

  4. #3  
    Forum Freshman
    Join Date
    Dec 2013
    Posts
    12
    somebody else with nice rounded illustrations huh, KJW? Thanks for that explanation MH.
    Reply With Quote  
     

  5. #4  
    Forum Radioactive Isotope cosmictraveler's Avatar
    Join Date
    May 2005
    Location
    Key West, Florida, Earth
    Posts
    4,789
    I'd say that infinity is outside of this universe and more universes exist that we cannot see yet. That is my opinion.
    When the power of love overcomes the love of power the world will know peace.
    Jimi Hendrix
    Reply With Quote  
     

  6. #5  
    Forum Freshman
    Join Date
    Dec 2013
    Location
    Ohio, U.S.
    Posts
    17
    I think that the universe is expanding into a never ending complete vacuum. Although the universe is recognized as a vacuum, planets, stars, asteroids, and others make the universe an incomplete vacuum. So, the universe would be slowly dragged into the complete vacuum.
    Reply With Quote  
     

  7. #6  
    Quagma SpeedFreek's Avatar
    Join Date
    Jan 2011
    Location
    London, UK
    Posts
    2,786
    So you are ignoring Marcus' excellent explanation in post #2 then?
    sir ir r aj likes this.
    "Ok, brain let's get things straight. You don't like me, and I don't like you, so let's do this so I can go back to killing you with beer." - Homer
    Reply With Quote  
     

  8. #7  
    KJW
    KJW is offline
    Forum Professor
    Join Date
    Jun 2013
    Posts
    1,134
    Quote Originally Posted by Markus Hanke View Post
    I understand that this is a highly counterintuitive notion for which there is no real everyday analogue
    One analogy I've seen for the intrinsic nature of differential geometry is an ant on a fog-enshrouded planet, where the ant can only determine the nature of the planet by measuring distances on the surface of the planet.
    There are no paradoxes in relativity, just people's misunderstandings of it.
    Reply With Quote  
     

  9. #8  
    Forum Freshman
    Join Date
    Dec 2013
    Posts
    61
    Quote Originally Posted by sabodriver17 View Post
    I think that the universe is expanding into a never ending complete vacuum. Although the universe is recognized as a vacuum, planets, stars, asteroids, and others make the universe an incomplete vacuum. So, the universe would be slowly dragged into the complete vacuum.
    If you re-read what Markus posted and think about what he said you will find that this is covered in that explanation.

    The "complete never ending vacuum" that you mentioned would be included in the definition of "infinite" in his explanation. You could well have a finite amount of "stuff" (energy, matter....) existing in an infinite space. What we observe could be all that exists, unlikely but possible.
    Reply With Quote  
     

  10. #9  
    Quagma SpeedFreek's Avatar
    Join Date
    Jan 2011
    Location
    London, UK
    Posts
    2,786
    Quote Originally Posted by David M W View Post
    Quote Originally Posted by sabodriver17 View Post
    I think that the universe is expanding into a never ending complete vacuum. Although the universe is recognized as a vacuum, planets, stars, asteroids, and others make the universe an incomplete vacuum. So, the universe would be slowly dragged into the complete vacuum.
    If you re-read what Markus posted and think about what he said you will find that this is covered in that explanation.

    The "complete never ending vacuum" that you mentioned would be included in the definition of "infinite" in his explanation. You could well have a finite amount of "stuff" (energy, matter....) existing in an infinite space. What we observe could be all that exists, unlikely but possible.
    But I think we must clarify here that if the universe is infinite, this does not mean a finite universe expanding into infinite empty space, as sabodriver17 said. It means the infinite universe is full of particles, just like our observable part of the universe. The "complete never ending vacuum" would contain stuff and thus would incomplete by sabodriver17's definition.

    According to our current understanding, the universe is either finite and full of galaxies, or infinite and full of galaxies. It does not expand into empty space, but rather the distances between the clusters of galaxies increases.

    When we say the universe has no edge or boundary, what we mean is that there is no place where there are no more galaxies and just empty space beyond.

    Curious About Astronomy: What is the universe expanding into?

    Where is the centre of the universe?
    Cogito Ergo Sum likes this.
    "Ok, brain let's get things straight. You don't like me, and I don't like you, so let's do this so I can go back to killing you with beer." - Homer
    Reply With Quote  
     

  11. #10  
    Forum Professor pyoko's Avatar
    Join Date
    Jun 2011
    Location
    Australia
    Posts
    1,091
    "Dark flow" is no fluke, suggests a new study that strengthens the case for unknown, unseen "structures" lurking on the outskirts of creation.

    In 2008 scientists reported the discovery of hundreds of galaxy clusters streaming in the same direction at more than 2.2 million miles (3.6 million kilometers) an hour.
    This mysterious motion can't be explained by current models for distribution of mass in the universe. So the researchers made thecontroversial suggestion that the clusters are being tugged on by the gravity of matter outside the known universe.
    New Proof Unknown "Structures" Tug at Our Universe
    It is by will alone I set my mind in motion.
    Reply With Quote  
     

  12. #11  
    New Member
    Join Date
    Dec 2013
    Posts
    3
    [QUOTE] When we say the universe has no edge or boundary, what we mean is that there is no place where there are no more galaxies and just empty space beyond.
    /QUOTE]

    How then does this mesh with the concept of multiple dimensions required by string theory? As I understand it (in a highly simplified manner) universes exist as membranes in a ten or eleven dimensional "higher" universe. Wouldn't this imply that our three dimensional (4 including time) does expand into a higher dimensional space? Do these membranes grow?

    On a related thought, don't three dimensional objects *require* a four dimensional space? (I'm talking only physical dimensions here) Consider: a zero dimensional object (a point) requires a one dimensional universe (a line) or it *is* the universe. Similarly, a one dimensional object requires a two dimensional universe, etc. This would seem to lead one to the conclusion that a three dimensional object *requires* a four physical dimension universe. Am I making a classic mistake here?
    Implicate Order likes this.
    Reply With Quote  
     

  13. #12  
    Brassica oleracea Strange's Avatar
    Join Date
    Oct 2011
    Location
    喫茶店
    Posts
    16,489
    Quote Originally Posted by khaldac View Post
    On a related thought, don't three dimensional objects *require* a four dimensional space? (I'm talking only physical dimensions here) Consider: a zero dimensional object (a point) requires a one dimensional universe (a line) or it *is* the universe. Similarly, a one dimensional object requires a two dimensional universe, etc. This would seem to lead one to the conclusion that a three dimensional object *requires* a four physical dimension universe. Am I making a classic mistake here?
    Interesting point (no pun intended). It would appear that multiple zero-dimensional points would need to exist in a 2D or higher space in order to be distinct. But that appears to be an exception. Multiple 1D line segments can exist in 1D space. Multiple 2D shapes can exist in 2D space (look at the computer screen in front of you for an example). And very obviously, multiple 3D objects can exist in 3D space (look at the room around you).

    However, when we talk about curved (4D) space-time, you might think that that needs to be embedded in a higher order space. After al, we are familiar with the curved 2D surface of an orange being embedded in 3D space. But it turns out that for three dimesnions and above, curvature can be defined "intrinsically" and does not require a higher dimensional space. So, as far as we know, the universe is 4 dimensional.
    Implicate Order likes this.
    Without wishing to overstate my case, everything in the observable universe definitely has its origins in Northamptonshire -- Alan Moore
    Reply With Quote  
     

  14. #13  
    Quagma SpeedFreek's Avatar
    Join Date
    Jan 2011
    Location
    London, UK
    Posts
    2,786
    Quote Originally Posted by khaldac View Post
    When we say the universe has no edge or boundary, what we mean is that there is no place where there are no more galaxies and just empty space beyond.
    How then does this mesh with the concept of multiple dimensions required by string theory? As I understand it (in a highly simplified manner) universes exist as membranes in a ten or eleven dimensional "higher" universe. Wouldn't this imply that our three dimensional (4 including time) does expand into a higher dimensional space? Do these membranes grow?
    When we talk of space in relation to our universe, we are using the same concepts as we use within our universe. We describe the universe with 3 dimensions for space (and 1 to represent time, as you say), so those 3 spatial dimensions are what I was talking about above. We do not think the 3 dimensions of space extend beyond the contents of the universe (this is based on things like the cosmological principle, the predictions of general relativity and the idea that the boundary conditions would leave a signature that we may be able to detect), so we do not think there is a place in those 3 spatial dimensions where the galaxies stop and there is empty space beyond. Higher dimensions are a different issue.

    If the (3+1) dimensions of our universe were embedded in a higher dimension, there would still be no edge to our universe when viewed from within those (3+1) dimensions. A simple example is to use the topology of a 3-sphere (a spherical 3 dimensional surface, rather than the 2-spheres we are accustomed to seeing, which are only spherical 2 dimensional surfaces, such as a globe). If the universe were a 3-sphere, then in any direction you look outwards into the universe, the straight line you think you are looking along is actually a very small section of a very large great circle that circumnavigates the universe. If it were possible to travel as far as possible in a straight line in the universe, you would end up back where you started.

    These principles can apply whether the universe is embedded in a higher dimension or not.
    Implicate Order likes this.
    "Ok, brain let's get things straight. You don't like me, and I don't like you, so let's do this so I can go back to killing you with beer." - Homer
    Reply With Quote  
     

  15. #14  
    Forum Junior
    Join Date
    Oct 2013
    Posts
    215
    Quote Originally Posted by SpeedFreek View Post
    Quote Originally Posted by khaldac View Post
    When we say the universe has no edge or boundary, what we mean is that there is no place where there are no more galaxies and just empty space beyond.
    How then does this mesh with the concept of multiple dimensions required by string theory? As I understand it (in a highly simplified manner) universes exist as membranes in a ten or eleven dimensional "higher" universe. Wouldn't this imply that our three dimensional (4 including time) does expand into a higher dimensional space? Do these membranes grow?
    When we talk of space in relation to our universe, we are using the same concepts as we use within our universe. We describe the universe with 3 dimensions for space (and 1 to represent time, as you say), so those 3 spatial dimensions are what I was talking about above. We do not think the 3 dimensions of space extend beyond the contents of the universe (this is based on things like the cosmological principle, the predictions of general relativity and the idea that the boundary conditions would leave a signature that we may be able to detect), so we do not think there is a place in those 3 spatial dimensions where the galaxies stop and there is empty space beyond. Higher dimensions are a different issue.

    If the (3+1) dimensions of our universe were embedded in a higher dimension, there would still be no edge to our universe when viewed from within those (3+1) dimensions. A simple example is to use the topology of a 3-sphere (a spherical 3 dimensional surface, rather than the 2-spheres we are accustomed to seeing, which are only spherical 2 dimensional surfaces, such as a globe). If the universe were a 3-sphere, then in any direction you look outwards into the universe, the straight line you think you are looking along is actually a very small section of a very large great circle that circumnavigates the universe. If it were possible to travel as far as possible in a straight line in the universe, you would end up back where you started.

    These principles can apply whether the universe is embedded in a higher dimension or not.
    If each moment is different than the next this would imply that each moment has boundaries relative to mass and velocity. This would mean traveling in a straight line and curving around and ending up where it started is relative to the moment. The reference frame is the fastest frame which in our case is the speed of light. A straight line traveling faster than the speed of light would start to curve. Traveling at the speed of light a straight line would be constant as it would stretch across each frame in every frame.
    Reply With Quote  
     

  16. #15  
    Forum Bachelors Degree GoldenRatio's Avatar
    Join Date
    Dec 2013
    Posts
    415
    In an infinite universe, an infinite number of civilization obtain FTL travel, and not one but an infinite ammount of them. Likewise, wouldnt an infinite ammount of them decided to come take over earth.

    This assumes 3 things. FTL is possible, we are not alone (which in an infinite universe is almost a mathmatical impossibility) and the universe is not infinite. If any one of these is wrong then we are still here. Im hedging that the universe is not infinite.
    Reply With Quote  
     

  17. #16  
    Forum Freshman
    Join Date
    Dec 2013
    Posts
    5
    We don't really know, one way or the other, if our Universe is all there is and can only expand "into itself", or is expanding into a much larger existing three dimensional space, or is a three-dimensional space warped into a fourth physical dimension. Or what about the Multiverse "theory"? Well, until it can be tested and disproved, it's not really a scientific theory, now is it. (Not a question)

    Although I remember reading recently about the possibility of inferring the existence of other "universes" by their possible quantum effects on OUR Universe. Great stuff, cosmology. Where science meets philosophy and religion.
    Reply With Quote  
     

  18. #17  
    Malignant Pimple shlunka's Avatar
    Join Date
    Jan 2013
    Location
    Dogbox in front of Dywyddyr's house.
    Posts
    1,784
    The neighbor's.
    "MODERATOR NOTE : We don't entertain trolls here, not even in the trash can. Banned." -Markus Hanke
    Reply With Quote  
     

  19. #18  
    Forum Sophomore
    Join Date
    Dec 2010
    Posts
    117
    Read Paul Davies - 'The goldilocks enigma'

    The big bang was not an explosion IN space and time
    It was an explosion OF space of time
    Reply With Quote  
     

  20. #19  
    Forum Professor Zwirko's Avatar
    Join Date
    Sep 2008
    Location
    55 N, 3 W
    Posts
    1,082
    I know this is an old thread with a very good answer at the top, but it seems like a decent enough place to ask this question.

    In brane cosmology there a concept known as the "bulk", which is apparently some kind of weird hyperspace. Some models of brane cosmology have branes colliding and creating our universe. My question is this: In these models is the space-time of our universe expanding inside that hyperspace? Or, if we could somehow observe from inside the bulk (as a thought experiment) would the expansion of the universe not be visible at all, as if it were expanding "inside itself".
    Reply With Quote  
     

  21. #20  
    New Member
    Join Date
    Jun 2012
    Posts
    3
    My question posted today has a video link as shown here http://m.youtube.com/watch?v=MO_Q_f1WgQI&feature=kp this relates to a Brian Greene video which explains the 4 dimensions of spacetime rather well and could help you understand the expansion of the universe.
    Reply With Quote  
     

Similar Threads

  1. Is the universe expanding or ?
    By Martinaston in forum Personal Theories & Alternative Ideas
    Replies: 31
    Last Post: March 11th, 2013, 02:59 AM
  2. Expanding Universe
    By ampwitch in forum Physics
    Replies: 7
    Last Post: July 11th, 2012, 03:42 AM
  3. Expanding Universe
    By MOHANTHILAGARAJ in forum Physics
    Replies: 5
    Last Post: December 31st, 2011, 08:02 AM
  4. Is the universe expanding?
    By ox in forum Astronomy & Cosmology
    Replies: 27
    Last Post: September 8th, 2009, 02:16 PM
  5. Expanding Universe
    By Joshua Violinist in forum Astronomy & Cosmology
    Replies: 14
    Last Post: May 16th, 2006, 05:44 PM
Bookmarks
Bookmarks
Posting Permissions
  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •