Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Larger structure than observable universe?

  1. Mar 11, 2012 #1


    User Avatar

    Hi all,
    just like the atomic world is unobservable to our normal optical observation,
    can it not be that there can be out there some structure too large that we are deluded to believe that there are merely galaxies and all empty beyond.
  2. jcsd
  3. Mar 11, 2012 #2
    Hi dpa,

    All one can really do is look at the arguments. The reason why we can't observe small things using light is simply because they are smaller than the wavelength of light we can use to measure it (and if we try too make wavelengths smaller we disturb the thing more). It does not seem like this is any objection in the case of very large objects.

    Also I don't think anyone really sticks to a hypothesis that there is nothing beyond the observable universe. Actually I think most cosmologists would expect the universe to be infinitely large and so we cannot possibly observe it all. In any case the difference between this case and the atomic scale case is that scientists have been able to observe, measure and describe things on an atomic and even subatomic scale. Then we can say something like we know something of a certain (observed) nature exists on these scales, but we cannot observe it in the usual optic sense. Moreover we have an explanation of why this is impossible.

    On the large scales I think the only thing sort of related are things like dark matter (and possible dark energy, but I know nothing about this). Dark matter is also not observable by light of any kind, hence dark. We can observe it only through gravity, however we can through these same means also make some estimate of it's size and I don't think it will be larger than say a galaxy. So the fact that we cannot see it does not seem to be merely because of its size.

    So to answer the question: of course it could, anything is possible. There is however nothing to be explained by this reasoning so it doesn't pay to think about it. First find something 'invisible' and large, then try to explain why it is invisble!
  4. Mar 11, 2012 #3


    User Avatar
    Science Advisor

    Is the Universe really infinite or just really big? talks about what's beyond the observable universe within the LCDM model, which is the simplest model consistent with present observations.

    Inhomogeneity effects in Cosmology discusses models for what's beyond the observable universe in more complex models that are still consistent with present observations and the known laws of physics such as general relativity.
    Last edited: Mar 11, 2012
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook