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Expanding? Really? What if

  1. May 18, 2008 #1
    Just a thought I literally just came up with sitting here on a Sunday morning after having joined this site about a minute ago (first timer). Reading some of these posts about the expanding universe and thinking about the idea of relative positions, I thought of this angle on things. Now, this has probably already been thought up but I haven't got my copy of 'science theories' handy.
    Here it is; what if the universe does not expand, but matter condenses. This does not indicate whether space is expanding/fixed or anything, but just that matter is condensing. This could explain the observation that points in space are moving away from one another, as the distance between galaxies etc. would increase as the size of the galaxies decreases. The red shift observation indicating that areas farther from the 'centre' of the universe are moving faster away could be explained (perhaps) by faster rates of condensation due to less energy being present the further you move from the 'centre'.
    Now, it is also my understanding, and this is where the relativity part comes in, that this condensation of matter would not be directly measurable. This is because the instruments, and indeed the observer, as well as the observed object(s) would all be condensing at approximately the same rate. Similar to the experiment where an observer is in a windowless room with no references other than himself or the walls. Are the room and observer moving at a constant velocity in a straight line, or are they stationary? Ok, so this is completely different situation, but the point is that no measuring device can observe what is trying to be measured, because the device is experiencing the same change. Therefore we cannot measure the condensation of matter on a small scale, but can see the change in distance between objects when talking about galaxies etc. What about planets and stars, why don't they contract in relation to one another? Measuring change in distance between them on this scale would not be noticeable, partly due to the small distances, and partly due to gravity keeping the masses at fixed orbits or at least causing them to coalesce into clusters.
    So there it is. Please feel free to shoot this one out of the sky if you wish, as I don't think it to be the case anyway, I think I just had one too many coffees. Just food for thought...
  2. jcsd
  3. May 18, 2008 #2


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    Imagine 2 circles a distance d apart. If the circles get smaller, the distance between their centers wont.
  4. May 18, 2008 #3
    Alright, good point there, but still, if you were in one of those circles observing the other, it would appear to be moving away from you...
  5. May 18, 2008 #4


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    Rafterman1, welcome to PF.

    This idea of condensation vs expansion has been proposed and it may well be possible to make one that explains observations.

    I'd like to point out that the unverse does not have a centre. It is like the surface of a sphere, which does not have any point you could a centre. Our models of the cosmos are framed in 4 dimensions, so the 'surface' is a 3D hypersurface. Hard to imagine.

    Each observer in this universe sees matter receeding ( or at least redshifted according to distance) and in that sense is at the centre of their own observable universe.
  6. May 18, 2008 #5
    Thank you Mentz, yes I understand there is no true 'centre' in the classic sense. I guess what I am trying to say is that given that we can only say something is true if we can observe this (directly or indirectly). And I am, in a way, trying to play the devil's advocate here by highlighting a possible other explanation for the handful of observations that relate to the state of our universe. Could our current observations also be explained by the condensation of matter? Or is there any evidence relating to the state of the universe that refutes this?
  7. May 18, 2008 #6


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    Rather than explanations we have theories, which are in effect mathematical models. General relativity based cosmological models actually predict an expanding space-time, which seems to fit the facts, so why look for something else ? If all observations were explained by a consistent theory of 'condensation', we would then have to choose which one we believe. But such a theory does not exist, and there seems to be little point in looking for one.
  8. May 18, 2008 #7


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    The distance will get "smaller" if the unit of measurement is based on, r, the radius of the circles. In such a system of measurement there would be no way to tell if d or r is changing, all you can really know is that the ratio d/r is changing.
    Last edited: May 18, 2008
  9. May 18, 2008 #8
    If the circles were solid objects then presumbly rod and rulers would be shrinking to the same extent and the measurement of the distance from the centre of one circle to the other would be longer using those contracted rulers.

    Of course clocks would have to speed up by the same factor (or light would have to slow down) so that measurements made by sending light signals were consistent with measurements made by rulers and things start getting complicated when you try extending the idea to a more complicated dynamic universe.
  10. May 18, 2008 #9


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    There is no way to distinguish both scenarios by observation, so you can say that both viewpoints lead to the same predictions. But there is an important philosophical difference: Both predict that we observe an expanding universe, but one theory explains this observation by an expanding universe, while the other postulates an unobservable static universe and an unobservable shrinking of rulers etc. Economy of thinking dictates that we eliminate all unobservable quantities from our theories if reality can be described equally well without these.
  11. May 25, 2008 #10
    One other comment regarding dx's thoughts:

    If the surfaces are retreating toward their centres, then the photons they emit will be redshifted, since the point of emission at the beginning would not equal the point of emission at the end (assuming photon emission is not instantaneous). Likewise, if the surfaces were moving away from the centres, the photons would be blueshifted. Of course, this idea goes a little haywire when the surface is moving away from the centre at a velocity greater than c (would this lead to negative wavelength? heh).

    I have to admit though, I still believe wholeheartedly in the metric expansion of space (and dark energy if need be).
  12. May 25, 2008 #11
  13. Jun 2, 2008 #12
    I was just wondering when you say time would have to speed up what do you mean? What is time relevant to?
    And it depends on whether you believe the universe is open or closed....the rods and rulers would shrink if the universe is closed but if it was open wouldnt they stay the same but objects would just get smaller.
    Or if you take that a contracting universe is returning to its original state (before the big bang) then the space between the objects wouldnt have any effect as they would all stop at a centre.
    If that makes sense to any of you.
  14. Jun 2, 2008 #13
    Also to what Shalayka said....
    as we are still seeing red shift i dont think what i said about the universe returning to its original state is possible because it would have a blue shift so yea scratch what i wrote about that :)
  15. Jun 2, 2008 #14
    Whats the explanation as to why the universe just happens to be expanding at just below the critical rate?
  16. Jun 4, 2008 #15
    What do you mean?
    all i can think is that probably because no one knows what the critical rate is and it hasnt become critical yet.
  17. Jun 6, 2008 #16
    condensation rather than expansion

    And I am, in a way, trying to play the devil's advocate here by highlighting a possible other explanation for the handful of observations that relate to the state of our universe. Could our current observations also be explained by the condensation of matter? Or is there any evidence relating to the state of the universe that refutes this?[/QUOTE]

    I am glad to know I am not the only one who has this idea. There are few details you did not mention in your post. I am not sure where can I read about the condesation theory rather than the expansion one. I do not understand why we keep avoiding the obvious. Centuries ago, we though that the earth was flat (knowing that everything in the sky was spheric). Same now, we all see that life of stars and galaxies is created based on condensation/exlosion cycles. Why not to accept the idea that the hole universe are, as you said, a huge space filled with areas of condensation/explosion of matter. The detail I would have to add is that the limits between these clusters of matter is filled with its own escence at rest and therefore suspended in time (no time).

    Kudos for the expansion/condensation theory!!!

  18. Jun 10, 2008 #17
    What would be interesting is if the "contracting" theory could link with GR especially time dilation.
  19. Jun 16, 2008 #18
    Great Idea. One thing is there is no center of our 4d bottle and one would have to use 4d logic to think about contracting. So it would be a big bottle and it is contracting. I have enough trouble understanding how there is no outside to the universe and no time before zero. One thing is if space was contracting then you could turn this around and say spce is shrinking faster now than in the past. With exspantion of space as each amount of space is added to the universe expands faster as the amount of space expands like compound interest. Space is what is exspanding isn't it not matter? I'm new to the forum and just have used my head and a book on relativity I read many years ago and what I pick up on TV. So if I have and bad idea let me know.

  20. Jun 25, 2008 #19
    I'm interested in a similar scenario except that it relates to a red shift due to gravitational attraction.

    When considering the speed of objects revolving around a galactic boundary and the gravitational confluence at the center of the galaxy, it would appear that all luminous objects would be spiraling toward the center. If an object is spiraling toward that center, then it would appear that light from these objects would experience a red shift as the object would have a relative motion away from any external static frame. What is interesting is that the motion toward the center would cause a red shift from any observable direction except parallel to the axis of rotation. Additionally the observer's field of vision would encompass a larger field of red shift on the near side of the galaxy and the blue shift would encompass a larger field on the far side of the galaxy. The farther away a galaxy the more this shift would be observable.
  21. Jun 27, 2008 #20
    That is a hard thought to think about and I find the idea that space is exspanding and when we look out to another galaxy we see it in the past and when the universe was smaller that is about as far as I can stretch my mind. This of course means that there is a curve in a beam of light as it travels from galaxy to my eye and that is in the 4th demension. This curve will bring one back to were it started from that is if you could go instantly around the loop and you should the way I have it figured out pass through the singularity or were it was any way.So back to topic I fail to see the way the details would work if the universe was contracting and I'm leaving that discussion to wiser chaps than me.
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