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Expanding universe or shrinking space(-time)

  1. Nov 13, 2009 #1
    Hi all,

    I was watching some online video lectures from the Quantum to Cosmos festival, where they discussed the expansion of the universe and the problems this brings in physics. Problems like the need of dark matter and what the mysterious force is that accelerates this expansion. I've been pondering about this some more, I'm not a scientist but just like to think about such things.
    As I was watching this lecture today I suddenly had a crazy idea. Actually it's so simple I can not imagine I would be the first one to come up with this and since I could not find any other references to this idea it may be just too silly to even consider. I think on this forum a lot of people know much more about this so I will just throw in my idea and will see how silly this would actually be :)

    So, here's my thought: What if the universe is not really expanding, but in stead the galaxies are decreasing in size. Well, not just their size but their space-time. This would make it appear from our point of view that the universe is expanding, while we are actually shrinking. This is simple relativity. It this would be true we would not have to wonder about the mysterious force that expands the universe and maybe dark matter could be questioned (more).
    Actually this question comes down to "do we really know for sure if the universe is expanding?" (and why). If we don't know this for sure my idea may not be so crazy after all.

    I'd love to hear your thoughts about this.
     
  2. jcsd
  3. Nov 13, 2009 #2
    Hi Luuk, welcome to PF.
    First of all, universe must expand or contract. We know that it is expanding by observing other galaxies, which are redshifted, meaning that they are receding from us. It is not expansion by itself which is puzzling, but rather expansion that is accelerating.
    You proposal is in conflict with Hubble's law, which states that more distant object is, it is receding faster. In case of "galaxies getting smaller" it would mean that more distant galaxy is, it is shrinking faster. That does not make much sense.
     
  4. Nov 13, 2009 #3
    Thanks S. Vasojevic. But I must tell I was actually expecting to get an answer like this. It leaves me with some other questions:
    1. "universe must expand or contract". Isn't this only based on the "big bang" model, which is only a theory? In this model it does make sense, but what if this model is incorrect?
    2. The red shift of the galaxies could only be produced by the doppler effect but this could be the result of difference in energy loss over longer distances in the color spectrum of light. I've read and heard more about this, one article that mentions a bit about this can be found here: http://www.newscientist.com/article...antum-speed-bumps-no-obstacle-for-light.html" I don't recall where I've read the other articles about this.
    3. I don't know much about Hubble's law. I'll look into this more. But then again, is this law proven, or could it be questioned concerning this?

    If I'm asking too silly questions just say so. I just like to question everything. I'm just having this thought but if I'm getting proved wrong I can let it go.
     
    Last edited by a moderator: Apr 24, 2017
  5. Nov 13, 2009 #4
    1. If you ask me BB model is on the right track, but still has a potential to throw some surprises, probably as soon as James Webb telescope starts beaming pictures back to Earth.

    2. You are probably referring to cosmological redshift, which describes redshift of distant objects as "stretching" of light wave during its journey through expanding space.

    3. Hubble law is straight forward observational law, it really does not need much proving.
     
  6. Nov 13, 2009 #5
    BTW, there are no silly questions, especially if you are willing to respect arguments. But in order to ask silly questions you should learn much, because there is a good chance that either same question has already been considered in science, or there is some well established law which contradicts your idea.
    Just consider Einstein thinking "Oh, I have this idea of gravity as curved space time, but it is so silly, I will not pursue it any more". So ask silly questions as much as you want, but keep in touch with reality.
     
  7. Nov 14, 2009 #6
    Yes, you're right; there are no silly questions, just the silly people who ask them :)
    I need to learn more about all this for sure, but knowing all is a long way to go. Hubble's law may seem straight forward and proven. I still question it because it is based on the red shift which depends on a lot of factors. Again, I don't know all about this but I do know this subject is still debated.

    The reason I came up with my crazy idea is that all the scientists speaking at this festival were telling about all the problems they're having with their theories and they want new "crazy" theories. That's what they really said. You can watch this interesting opening video here: http://www.q2cfestival.com/play.php?lecture_id=7976" [Broken]

    My thought was that my hypothesis using contracting galaxies/local space would make more sense than searching for some mysterious invisible force that would accelerate the universe outwards. It's like falling from a roof and wondering why the house is suddenly accelerating upwards.
     
    Last edited by a moderator: May 4, 2017
  8. Nov 14, 2009 #7

    Chalnoth

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    Well, from my perspective, those are just two different ways of talking about the exact same behavior of our universe.

    A perhaps more accurate description of how our universe is changing through time is that the ratio between the average distances between atoms and the sizes of atoms is increasing. But because we think of atoms being stable (probably because we are made of atoms), we think of the universe as expanding.

    If you were to change your language so that our universe is static in size, then we would have to be shrinking.
     
  9. Nov 14, 2009 #8
    Yes, that's another way of putting it. But I'm not stating the actual size of the universe is static. I'm leaving this open because it could also be a combination of an expanding (or maybe even contracting) universe and contracting galaxies. I guess this would be very difficult to know for sure.
     
  10. Nov 14, 2009 #9

    Chalnoth

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    Well, what I'm saying is that there is now no question that the distances between galaxies is increasing relative to the sizes of atoms. That's a statement that is clearly true, as it is supported by multiple lines of independent, mutually-corroborating evidence.
     
  11. Nov 14, 2009 #10
    So you're also saying the size of atoms is not related to the size/density of space itself? How would one determine this?
     
  12. Nov 14, 2009 #11

    Chalnoth

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    No, I'm not saying that. I'm just saying that the distances between galaxies are getting larger compared to the sizes of atoms.
     
  13. Nov 14, 2009 #12

    atyy

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    When scientists say the universe is expanding they assume:

    1) Einstein's general relativity is true
    2) Matter is homogeneously distributed in space

    According to our observations, Assumption 2 is approximately true only on very large scales, so the expanding universe is only a good approximate description on the largest scales.

    If we drop Assumption 2, we can find non-expanding space, and we apply that on smaller scales such as the solar system.

    The universe as a whole - large and small scales is described by patching together both approximate descriptions.

    Expanding Space: the Root of all Evil?
    Matthew J. Francis, Luke A. Barnes, J. Berian James, Geraint F. Lewis
    http://arxiv.org/abs/0707.0380
     
    Last edited: Nov 14, 2009
  14. Nov 15, 2009 #13
    Thanks for the link. There's a lot of information there, a bit too much for for to grasp at once :) I will think this over some more and will see where it gets me.
    Now back to the usual weekend-things to do.

    Thanks all for taking the time and sharing the knowledge!
     
  15. Nov 15, 2009 #14
    If the galaxies were decreasing in size but the separation of galaxies was constant, they would be a lot less red shifted, I think. I don't think your idea is simply a different way of looking at the same "expansion", because in your model the space between shrinking galaxies is unaccounted for. What happens in between galaxies, where photons spend 99.99...% of their transit time, where they are heavily stretched by expansion?
     
  16. Nov 15, 2009 #15

    Chalnoth

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    Well, depends upon what you mean by shrinking galaxies. If we're not just talking about stars getting closer together, but all matter within galaxies shrinking proportionally, then the two ideas are indistinguishable.

    Consider the difference:
    1. Atom emits a photon at a particular wavelength. As the photon is in transit, space expands, photon expands with it. When it is received at the other end, its wavelength has now increased by a factor of the expansion.

    2. Atom emits a photon at a particular wavelength. As the photon is in transit, atoms shrink. When it is received at the other end, the apparatus used to measure the wavelength has shrunk by a factor of the expansion, meaning that the experimenter measuring the wavelength considers it to be larger by a factor of the expansion.
     
  17. Nov 15, 2009 #16
    Well, now couldn't we test this with some rather large Young's two slit experiment?

    Case1 : Space expands while wavefronts are in transit. Wavelengths lengthen. Measure the distance between interference fringes with a big ruler. Interference pattern will be more spread out than expected.

    Case 2 : Atoms shrink while wavefronts are in transit. Use some kind of photelectric apparatus to measure the distance between interference fringes by the time for light to propagate from one to another. The interference pattern is the originally expected size.

    Well, at least, that seems to be the case to me....
     
  18. Nov 15, 2009 #17
    Ok, I see your point.

    In turn I'd say the equipment would not be able to shrink, because the atomic bonds are at equilibrium points- moving them closer together will result in a restoring force that will maintain their solid structure, unlike the photons which cannot maintain their wavelength.

    But I realise this is a different line of argument, and I don't know if it's a very good one because I think am making some big assumptions.
     
  19. Nov 15, 2009 #18

    Chalnoth

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    Well, this is sort of the issue. The alternative to the universe expanding is that the atomic forces change in time in such a way that atoms get smaller with time.

    Bear in mind that I don't think this is saying anything in particular about our universe. That is, I don't think this little thought experiment is showing that it could be true that we have no expansion. Rather, I think what it is saying is that there are different potential ways of looking at the exact same phenomenon. The particular words we use to describe the phenomenon are pretty much irrelevant to the underlying behavior, which can be described in any number of different ways. We only choose to use the specific terminology that "space is expanding" because it is convenient to think of atoms as being stable in size. There are other perfectly equivalent descriptions of the same behavior.
     
  20. Nov 18, 2009 #19
    I'm with you Luuk.
    You are not the first on that line of reasoning but anyway you deserve
    congratulations.
    To our satisfaction a complete model is scientifically available since 2002 in the arxiv, but it was never discussed. When 9999.9% of published pappers are in one direction it is hard to find 'the one' that constructs a whole new theory.

    "[URL [Broken] relativistic time variation of matter/space fits both local and cosmic data"
    [/URL]

    as Chalnot says, we think that atoms stay unmodified with time, but in fact there no scientific basis to that, as we can find in this post
    https://www.physicsforums.com/showpost.php?p=2439470&postcount=4"
    If we can not assert their invariability then the study must be pursued. There is a general rule that says "if something can happen then, most probably it must happen" (sure, in other words)

    I've tried, like you, to explore, the idea in this thread
    https://www.physicsforums.com/showpost.php?p=1999028&postcount=1"
    here https://www.physicsforums.com/showpost.php?p=2443586&postcount=44"
    I showed (with reasoning and calculations) that in fact there seems to exists a physical mechanism that is in presence that gives support to your thoughs.
    It reads like this: "Particle and his fields are associated, i.e. the field is an emanation of the particle. As field is spreading at 'c' speed then the energy in the field gets bigger and bigger and the energetic content of the particle must get lesser and lesser"
    Then the 'mass' M of particle must decrease, idem to the 'length' L and 'time unit' T.
    Those three quantities M,L,T are tied to atom scale.
    The time unit is a construct on top of 'length' (c=L/T is a constant).

    Now I expect it is time to tie all links, and also expect that some mentor can defend the liberty of thought.

    The interesting aspect is that all basic laws of physics remain the same and we will find the possible solution to many questions there remain open in physics.

    This is the "International Year of Astronomy - 2009" lets take advantage of this and start talking about the future.

    (someone can say that this issue is better suited to the subforum "debunk and scepticism" but it would be unfair because I can find more help and more informed opposition in this subforum)

    'aleas jacta est'
     
    Last edited by a moderator: May 4, 2017
  21. Nov 18, 2009 #20

    Chalnoth

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    heldervelez,

    Sorry, but I think you're making far too much of this. It is overstating the facts when you state there is "no scientific basis" for the atoms being unmodified in time. Rather, I would say that there is an arbitrariness in how we define time and space, which is just a statement that the numbers that we place on reality don't change how reality behaves. this means that there are multiple different ways to talk about the behavior of the universe around us that are equally correct.

    I suspect, however, that the things that you are proposing here are incorrect, or at least misleading. But it is difficult to say with the minimal explanation that you have provided here.
     
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