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

Intuitive problems with the standard model

  1. Dec 29, 2008 #1
    I don't claim to be an expert of any kind, and most of these "problems" I see are probably just due to my own pre/misconceptions, but nonetheless:

    1) As we get closer and closer to the Big Bang event, the universe is supposed to get hotter and denser until some sort of "infinity" where the Big Bang singularity is an infinitely hot and dense point of zero size (I would think?). Observational evidence does prove beyond a reasonable doubt that as we get closer and closer to this event in time, the universe is getting hotter and denser. The infinitely hot and dense scenario works for singularities within the universe, because space-time has already been defined within the universe, so the concepts of temperature and density actually mean something tangible (though the concept of infinity does not really). Energy (I think) is supposed (I think) by general relativity (I think) to sort of "generate" space-time (I think), but only does so after the event of the Big Bang (I think). Before the actually Big Bang event, there is no space-time per se, and therefore the concepts of temperature [temperature = motion = distance/time; before the Big Bang, no distance, no time, no temperature] and density [amount of something in a unit of area; before the Big Bang, no distance, no area, no such thing as "density"]. These were the only two things we had left to define the Big Bang singularity, and their concepts are completely meaningless in the context of the Big Bang?

    2)I like to think of the universe as some sort of function, and the fact that it works is that this function is equivalent over time; all the forces in the universe balance out. They always have and always will, every instant of time can be thought of as a different form of this function, and consequently, the universe can only be a different state of the original singularity we came from. (I think) this is the currently accepted (though very very very watered down version) train of thought for that sort of thing. This is not a problem, yet, but I'll get back to it.

    3) The universe is expanding, and this expansion is accelerating. This is said to be fact. The components of the universe are not expanding. This is also said to be fact. It is, instead, the "metric of space-time", that is expanding. Seems plausible to me, as long as the "metric of space-time" is some sort of field-type-related-something that is generated by energy. It's the general consensus that if space-time is generated by energy, there is no "outward" to expand to, and the universe expands sort of "within itself" (the expanding balloon analogy). This analogy is adopted basically because we generally observe size as a conserved quantity. My problem with this is that size is not a conserved quantity in any reference frame, ever. Infinite energy can fit into zero size and general relativity sees to make sure that we understand that size is not a conserved quantity, yet the standard model of cosmology is based on size as a conserved quantity. It seems like the exact same phenomena of expansion of the metric of space with particle size as invariant could be produced if it was the metric of space that was "invariant" (though its not really, as energy generates it) and things sort of reduced in size in accord with their local gravity.

    Relative to us, within the universe, within our local reference frame, we observe everything as flying away from us; the universe should be expanding. No problems here. Relative to the universe as a whole, we're reducing in size. The simplest version of the universe (Einstein's, in my opinion; whether or not he's accurate, it's a good model for imagining) holds the universe as spherical; holding all points sort of equivalent from the conception. If we imagined the entire universe as a sphere and imagined that that sphere had an exterior surface, and this sphere was once a singularity and is now just that singularity in a different state, why would the entirety of the singularity go against its own supposed nature for its constituents if it is held that no singularity go against its own supposed nature for its constituents. I.e, we don't see large rectangular black holes resulting from random phenomena within them, they're all basically the same "shape".

    4) Dark matter and energy are supposed to be the cause of the acceleration of the expansion of the universe. Dark matter and energy are completely undetectable, but are presumed to interact with the force of gravity. We predict dark matter and energy to fill up the 3D halos that surround galactic superclusters, and push out, opposite the force of gravity, so that everything expands away from everything, even though there's nothing it could possibly expand into.

    5) My big problem with the standard model is that these problems are almost too well cleared up (intuitively at least, though it could be way off mark, like I said I'm no expert of any kind) by the train of thought I propose in #3. The expansion of the universe should only be an observation relative to us measly observers within the universe, and the entire universe itself should "feel" no shape-altering effects, and we should instead, be reducing in size (or some sort of equivalent to this) within the universe. "Why would this clear things up?" you might ask. First, it requires no dark matter or energy. The force that governs the "expansion" of the universe, would work in the same inward direction as gravity, and because size is not a conserved quantity, more and more and more can be packed in to a smaller and smaller area, and as more is packed in, the smaller this space will try to get, just like a black hole. As a result, there will be a lot of space left over, in the form of a 3D halo that surrounds large structures such as galactic superclusters, though within these, things try to pack in to much to see that much space around things. The fact that dark matter and energy can only interact with gravity, are completely undetectable, and completely hypothetical probably makes this notion an order of magnitude more plausible. Furthermore, as a DIRECT result, as everything clumped together. Humans could only have evolved in a space small enough that they would be unaffected by this large scale phenomenon, and thusly we experience the same sizes everywhere in everything everyday, and naturally assume size to be conserved, and therefore naturally assume that as our galaxy gets smaller, and that galaxy gets smaller, that the increase in space between them means they're being pushed away by some mysterious force. By this notion, we would necessarily observe that 99.9999999% of structures would appear to be receding from us; does this observation sound familiar?

    Now since I spent so long punching holes in the masterpiece built by the blood sweat and tears of very hardworking and intelligent people, it's only fair to punch some holes in mine. First of all, if size were not conserved, it seems we should find at least some of the same particle type (protons for example) that did not share the same size as those we commonly find. As I understand it, this is not the case, and as far as we have directly observed, particle size is VERY conserved. Secondly, if everything in the universe were reducing in size, rather than the metric of space-time expanding, it seems the speed of light would be variable, which is known to be false. To be perfectly honest, these two considerations make my hypothetical scenario much more unlikely than the standard hypothetical scenario, so if I managed to sway you, go ahead and just sway yourself back over there, but leave a reply before you do :)
  2. jcsd
  3. Dec 29, 2008 #2


    User Avatar
    Science Advisor
    Gold Member
    Dearly Missed

    Tickle, your initial assumption is unfounded.
    You should read an up-to-date account. Try Einstein-online, the link is in my sig.
    As far as I know, nobody is claiming that a state of infinite density occurs in nature. All that happens is that the classic vintage-1915 model breaks down near "t=0" and is no longer applicable.

    Look at the page called "A tale of two big bangs" at the Einstein-online website.

    The bolded statement is unsupported by scientific evidence. A superannuated model breaks down at that point, but in other more recent models spacetime continues back before. Nonsingular cosmology is an active research area at present.

    True the vintage-1915 model breaks down and stops computing as you go back in time to near "t=0", so for that particular model, there is nothing before t=0. It's common for all sorts of mathematical models to have limits of applicability and to break down if pushed beyond their limits. That has happened before (not just in cosmology!) and the problem has been fixed by improving the model.

    It would be pretentious to claim, just because an old model breaks, that there is no spacetime and no temperature no density no time no distance etc etc. In the newer models there are all these things.

    One can run computer models back in time and study conditions, and vary parameters and so forth. The goal now is to derive observable consequences of the models so that they can be tested against fresh CMB data.

    One way to connect with the research literature, if you want, is to use keywords "quantum cosmology" at the Spires database. This particular search gives 241 papers published 2006 or later, with the most highly cited papers listed first.
    http://www.slac.stanford.edu/spires/find/hep/www?rawcmd=FIND+DK+QUANTUM+COSMOLOGY+AND+DATE%3E2005&FORMAT=www&SEQUENCE=citecount%28d%29 [Broken]
    My guess is if anything this underestimates research activity in this area---other search strategies would bring up a bunch more
    Last edited by a moderator: May 3, 2017
  4. Dec 29, 2008 #3


    User Avatar
    Science Advisor
    Gold Member

    General relativity [GR] is not intuitive, but, has survived every test ever applied. It is illogical to apply any model to t=0 in the bulk [watch of God] time sense. All of physics falls apart at that point, as Marcus noted.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook