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

Absurd question

  1. Sep 29, 2007 #1
    Is the big bang a white hole? Ya know, the inverse of a black hole... Any reasons why it can't be?
  2. jcsd
  3. Sep 29, 2007 #2


    User Avatar
    Science Advisor
    Gold Member
    Dearly Missed

    that possibility is being investigated.
    There may be reasons why it is impossible.
    But if you pose the question very generally then I personally have not heard anything that rules it out.

    There are many papers that study the possibility that the bigbang could have been preceded by some kind of gravitational collapse. that idea is pretty well developed, although not checked. The question is, what kind of collapse?

    would it necessarily have been the collapse of a whole universe---a "Big Crunch?" Most of the research explores this possibility. this kind of picture is called a "Bounce".

    or could it have been a more modest gravitational collapse----the formation of a black hole in a prior region?
    this is harder to imagine and has not been successfully modeled yet (unless in grossly oversimplified form.)

    I will get a link to some recent technical articles. At the moment they have only crude simplified models and the work is preliminary. I don't think you can draw any clear yes or no conclusions, but I will get a sample of current research and you can decide for yourself.

    here is one by Bojowald
    http://npg.nature.com/nphys/journal/v3/n8/full/nphys654.html [Broken]

    here commentary by Rovelli
    http://npg.nature.com/nphys/journal/v3/n8/full/nphys690.html [Broken]

    I sense that these are landmark papers in a sense, even though quite short and relatively untechnical (not just for specialists-only). their publication in the journal NP signals a change in the intellectual climate.

    here is a brief exerpt from what Rovelli had to say

    Science has frontiers; sometimes these frontiers move. One of the most impressive of science's frontiers is the Big Bang, and now a quantum theory of gravity — loop quantum gravity — is providing equations with which to explore it. Although these equations are still tentative, and rely on drastic approximations, they introduce a definite method of exploration, and are capable of describing the Universe not only close to the Big Bang but also beyond it. It is in this context that Martin Bojowald reports, in this issue, on the possibility of a peculiar limitation to our ability to observe fully the 'other side' of the Big Bang — whatever that expression might mean (Nature Phys. 3, 523–525; 2007).

    Here is some earlier discussion in a PF thread about the above

    Here is a recent paper by Kevin Vandersloot about resolving the blackhole singularity (what comes "after" or "out the bottom of" a black hole)
    Loop Quantum Dynamics of the Schwarzschild Interior
    Christian G. Boehmer, Kevin Vandersloot
    15 pages, 13 figures
    (Submitted on 13 Sep 2007)

    "We examine the Schwarzschild interior of a black hole, incorporating quantum gravitational modifications due to loop quantum gravity. We consider an improved loop quantization using techniques that have proven successful in loop quantum cosmology. The central Schwarzschild singularity is resolved and the implications for the fate of an in-falling test particle in the interior region is discussed. The singularity is replaced by a Nariai type Universe. We discuss the resulting conformal diagram, providing a clear geometrical interpretation of the quantum effects."
    Last edited by a moderator: May 3, 2017
  4. Sep 29, 2007 #3


    User Avatar
    Science Advisor
    Gold Member
    Dearly Missed

    Here's a way to sum it up.
    It is not an absurd question but you don't want to limit it to a particular paradigm like "white" or "black" or "worm"

    it is a process of finding out. say you think as many people do that there are no singularities in nature, they are only failures in human theory, then you try to push back time a little bit before the BB singularity and see what that might look like (as Bojo does)

    and you say time goes DOWN a BH so why should it stop and not continue evolving we just need a model of that----and you try to push time evolution beyond the pit of a BH and see what THAT might look like.

    and then if you can ever get models of both things, and check them by what they say about what is observable in the present, then you can ask if they MATCH UP.
    but that only comes later. for now there is just the tentative probing and pushing past the classic singularities in both case.
  5. Oct 1, 2007 #4
    hm. It seems to me, in my little box of perception, that the exact point of singularity is truly physically off limits, but there can be a "other side" of any black or white or worm hole. As far as the possibility of space-time and matter-energy crossing that point... um, thats the real mystery. From a QM perspective, I can see how it might be possible for matter-energy to cross through, since wavefunctions can propogate through a potential described as a delta function, it's just that they don't have to be differentiable at that point. But thinking in a general way about space-time and matter-energy, perhaps we can relate things backwards and say that a--spaciotemporal--delta function can pass through a wavefunction (I'm just trying to switch things around from above). I don't know how to interpret the last sentence, but I think most of all this stuff just comes down to our conceptions of matter-energy and space-time. For one, do all theories treat matter-energy as being "inside" space-time? What if space-time and matter-energy are mutually exclusive? In other words, where a particle is, space-time is not, and hence, particles don't exist "within" spacetime, but rather they exist side by side. Please excuse all my spectulation. I still haven't read the links you posted because I've been really busy, but I will eventually, and thanks for the reply.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook