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Balloon Analogy with different visualisation

  1. May 23, 2013 #1
    I have no formal training in this field. What I do know I have garnered from reading various publications or watching videos. I understand that the balloon analogy isn't popular, partly because once you say balloon people have trouble not thinking about a balloon. What I intend here is to lay out a visualisation of the balloon analogy but with the twist of space being a flat plane before the Big Bang. If this model has been proposed before I apologise.

    Imagine a flat sheet, similar to a bed sheet, floating in the air that draws in when pressed upon by a force. This stays within Einstein's view of gravity causing space to curve around an object. It has no edges and extends into infinity. At the moment of the Big Bang, all matter in the Universe presses down on space and depresses it. Every entity that is gravitation bound to each other presses on the same area of space and goes into the same depression of space. There are many of these individual depressions and each one causes space to draw downward.

    At this point you should imagine space as similar to a folded sheet of paper into an accordion and viewed from the edge like this ( ------- becomes --vvv--). The top of the wave is the original surface of space while the bottom is the depression caused by matter. As you can see, this makes all matter appear close to each other. But, as you pull on the edges of the sheet, the distance between the gravitation bound entities get further away from each other.

    Also, the fact that each depression is not to the same depth can be assumed, meaning some areas should return to near flatness before others. An object, such as a photon, does not travel up the line of space and back down between two gravitation bound groups, but takes a straight path from one to the other. As space returns to flatness, this path becomes longer.

    So, more observed space is realised without the need for space to have stretched and instead it was gathered in and depressed. All matter would 'appear' to have been in a small area, with some (perhaps only massless) matter able to travel between the depressions directly while gravity cannot do so. Or, the force pulling space back to flat is slightly greater than the gravity. This is causing the expansion to happen more rapidly as gravity is reduced by greater distance between unbound areas and causing less resistance.

    Anyway, if I don't stop here, I will be going into a lot of speculation and hopefully I have already demonstrated the visual effect I sought to impart. I have edited the post before posting to remove any blatant speculation. I found it hard not to insert some in the course of writing. I did leave the gravity speculations as I can see those would need be directly addressed. If the entire post is viewed as speculation I apologise and will understand if it is removed.
  2. jcsd
  3. May 24, 2013 #2
    we don't know what occurs prior to the big bang

    matter doesn't form until the temperature becomes low enough to form. However you can switch that with mass-energy. Also its not known if the universe is finite or infinite. pressing down is a misleading representation better to state something along the lines of "curves spacetime"

    the above makes no sense. If you add a curvature to a region that did not have a gravitational curvature before. That new curvature will attract matter etc. but this doesn't not mean that objects appear closer. Also what pulls your sheet? The rest of your statements have the same fundamental problems.

    I would recommend reviewing some decent expansion articles and GR articles. The FLRW metric does correlate GR and fluid equations in its design.


    I've been developing this site, it currently has some decent articles PF members have assisted me in writing. I would also recommend reading the two Lineweaver and Davies articles posted under reference materials.

    also Phind's coverage of the balloon analogy and its problems is a good read

    Last edited: May 24, 2013
  4. May 24, 2013 #3


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    Hi, Ogr8bearded1. Welcome to PF!

    Your visualisation appears to try and explain the expansion of the universe while suggesting that:
    -there was and is space outside the material universe into which the matter is expanding
    -space doesn't expand itself
    -there is a finite amount of space that might eventually run out
    -distances can be measured across something else than space
    -light somehow travels through another dimension
    -matter curves space and not space-time
    -light(energy in general) doesn't contribute to the curvature

    All of which are incorrect intuitions that need to be then weeded out. Compare to the balloon analogy and its only real problem of the third dimension that is often assumed to have physical meaning. All one needs to do is to advise the listeners to restrict themselves to the surface of the balloon only. Admittedly, it doesn't always work, but it's less of a hassle than straightening out all of the above mentioned misconceptions, that are bound to arise.

    You want your analogy to induce the least possible speculation about effects that might make sense in the reality of the analogy, but have no meaning in nature.

    A lot of the problems arise from your trying to marry one imperfect analogy(the balloon) with another(the space-time curvature as a rubber sheet deformation). The latter being possibly even more cringe-inducing than the first.

    All in all an admirable goal, but this is not the way to do it.

    (I have assumed here that you're trying to represent mainstream science, not advance you personal theory)
  5. May 25, 2013 #4
    Hi Mordred, you are right and I shouldn't have started with a concept as before the Big Bang. The model can account for both finite and infinite space. If finite there would be a curvature and stretching while only curvature in the case of infinite. And yes, though to my mind depression and curvature were the same I can see the need for staying within accepted vernacular. The same for my use of matter and your suggestion of mass-energy.

    I think we must agree that for some reason bodies which are gravitation bound to each other do not experience expansion. For this reason it seems obvious to me that space which has gravitation bound entities act in some way different from space which does not have them. I am trying to show a 2D view of a 3D volume of space. Hopefully some of my responses to Bandersnatch below will help clear up the model.

    Hi Bandersnatch. First let me say you are correct that I am trying to represent mainstream beliefs, and it seems I am trying to correlate Balloon Analogy with the space-time curvature. Let me try and clear up some misunderstandings or my mis-conveying the image.

    There isn't space outside the material universe, though by trying to make it a 2D model it does give that effect and I don't have sufficient knowledge of converting to 3D. I think this would be the same as the balloon doesn't expand into somewhere but stretches nevertheless.

    As above in my section to Mordred, I can adjust in the visual for either finite or infinite space (I think the latest data from WMAP now has swung back to the finite but I may have misread.)

    Once more a 2D model shows a 'gap' but this is still space that the matter moves through. Somehow this space is different, perhaps think of it as space containing a gravitation bound accumulation of matter for some unknown reason having slightly different properties than that which does not. This is a part of speculation I did miss in my clean-up and which had led to thoughts of why and how Dark Matter and Dark Energy had come into play. If I could figure out a 3D way of showing the shape then it wouldn't be a gap, so lets call it a limitation of the 2D image.

    I would like to ask either of you, in the Balloon Analogy, does the balloon space have only one side in a way similar to a Mobius Strip (and yes, I know a Mobius Strip has more than one side, just the other sides are very, very thin and overlooked,) and is this why some models suggest that the pennies are within and not on top of the balloon material? If it was in fact a Mobius strip shape, would the thin sides correlate to the 'small dimenstions' found in String Theory? Would I be off the mark in thinking it could still have, for want of a better way of saying it, an 'outside' and an 'inside' portion but still representing the same space? And by that I should be clear I am thinking as if was one coin but with a head and tail.
  6. May 25, 2013 #5


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    A 2d surface has no up or down sides. What you said there is just another misconception stemming from mentally embedding a plane into 3d space.
  7. May 25, 2013 #6
    A good way of representing expansion and personally my favourite is with a 3d grid of commoving coordinates.
    At its simplist form (x,y,z) you can easily show the following key aspects.
    1) the coordinates do not change.
    2) the angles do not change between any set of coordinates.
    3) Doesn't completely avoid the inside outside issue but far less likely. Lol new posters can be imaginitave.
    4) works well into adapting to the related mathematics,
  8. May 25, 2013 #7
    Thanks Bandersnatch that is what I thought, then my Attention Deficit set me off on the Mobius Strip thing(at least others say its AD, to me its just new questions popping up to explore,) did the other things make what I was trying to describe easier to understand? If not, then I guess trying to visualise a 3D object as a 2D example is beyond me and I should just leave it to those with a better understanding of the maths. I only did high school physics, chemistry and algebra and took CLEP tests for my science and math towards an AS in Accounting. I do appreciate you taking the time to answer, and maybe with the new data WMAP has given, someone can do a better modelling in the future than I have accomplished and it won't 'stretch and warp' my brain trying to understand. It does seem that any attempt to show in 2D is going to lead to problems of visualisation no matter who does it, and if we had an accurate 3D model already we would also probably have the answers to a lot of our current questions.
  9. May 25, 2013 #8
    No analogy is ever perfect. Some simply are more prone to misrepresentation.
    The complex shapes I consider as unlikely scenarios. They are worth considering as possibilities some may or may not have been ruled out.
  10. May 25, 2013 #9
    Thanks for your help also Mordred. Actually what I was trying to visualise came to me after reading the following which was linked from a link in your first post here. I had actually gone there to read after seeing you had linked it in another post. Maybe some geometry would help me understand better but took physics without doing that class.....plus it was all over 30 years ago.

    I had to remove at least a quarter of my first post so I wouldn't violate forum rules about speculation and staying with what I had read. I do enjoy the 'layman' examples even if the actual maths is beyond my ken. I guess this doesn't help with my trying to visualise. I'll try to do some more reading of posts here and links and hopefully if post again I can do better. Thank-you both for helping me see where I may have been unclear, misconceptions I had and ways of seeing how I could better visualise.
  11. May 31, 2013 #10


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    Thread closed at the request of the OP.
    Last edited: May 31, 2013
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