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Spawn of black hole thought experiment

  1. Jun 30, 2006 #1
    This thread is being started to avoid having https://www.physicsforums.com/showthread.php?t=124037" bunked down here to the realms of philosophy.

    We'd hit a few assumption walls, too many.

    I'm the OP of the parent thread, and I'm repliing to JesseM whose raised some fine point about why I think I should be calling a region cut off from all 'external' information, a universe. Even if the greater region that previously contained that region 'still' exists.

    I'll be quoting from JesseM's https://www.physicsforums.com/showpost.php?p=1023156&postcount=139"

    This is true. I think it is. I was trying to justify this in my previous 'philosophical' posts.

    I'll start again:

    If no information can pass into the new contained region, then how can it be effected by that which is exterier. In all meaningful ways, there is no exterior. No information, no cause, no effect. No exterior. Therefore, the 'interior' is all that is (in all meaningful ways). If the exterior where to have some other gargantuan event occur in it, how could this effect the interior? When would it, if the timeline is no longer intact?

    If you're asking the more 'physicsy' question, why is the time line severed then we need to descuss that on the other thread? But if you accept that no information can pass through the sigular surface, as it will be anahhilated by the infinite properties found there, time is holted, space destroyed, etc... Then the information that is contained within, is all that should be concidered for that region.

    You will have essencially created a new Laplacian Demon. A little one that fits perfectly in the new island of reality.

    You (or I) have had a little confusion over what my assertion was re this:

    You say:
    but previously in the same post you quote:
    I AM saying that its a new universe. I'm NOT saying that if HE can't see it, its not real. But if his universe (or if you prefer, region) can not observe something, then it can not effect him.

    Do you believe in the Demon? Do you think it will be cut in two by the singular surface?

    Without infomation there is no knowledge. The new lesser demon is still omniscient of all event that can occur, within his new realm.

    I'll stop there for response. :smile:
    Last edited by a moderator: Apr 22, 2017
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  3. Jun 30, 2006 #2


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    Instine, have you looked at all into Padmanabhan's recent papers? Marcus has started a thread on them up in "Beyond the Standard Model". The earlier one, "Dark Energy, Mystery of the Millenium" has what might be called a world view based on horizons. A rough memory from that paper: "Every class of observers has a horizon, and every surface in spacetime is the horizon for some class of observers."

    Then he uses insights from the holographic thesis (AdS/CFT) to build physics up from the horizons, but all physics remains relative to its horizon, or so I understand him.
  4. Jun 30, 2006 #3
    No, but yes this does sound interesting.

    Cheers for this pointer. I've not touched physics in 9 years, and had never heard of Padmanabhan. (shame on me)

    My own world theory is probably influencing this stance on 'what is a universe'.

    I believe that we may describe the universe in 6 dimensions. If we see the universe simply as an infinite matrix of space (3), time (1), Energy (1), Probability (1).

    i.e. at any point in space time there is a particular probability of there being a particular amount of energy.

    Certain laws inevitably evolve from logic and the intrinsic nature of the dimensions, and the constant speed of c. Such as the uncertainty principle. From these follow the larger scale laws. But they all stem from what can be observed, and what can not. SR and GR obviously are big players here. From this neat, but mostly useless world model, I do gain some deductions.

    It does away with creation issues, as well as many other unponderables (why are we here...). But it also creates a kind of large scale uncertainty principle, whereby an observer is within a world more complex than he/she can ever observe in total, but further, this world is immersed in another, beyond the observers light horizon. This hammers home the uncertainty on all scales.

    So from this I further assume that there can be no observable certainty. This is a leap, but it has been postulated, and for 'proven', many times before.

    So in a singularity, not only do we need to shield mortal eyes from infinite density, timeless space, etc... cosmic censorship also needs to keep things uncertain, where otherwise there would be no doubt. If you think about it, a true and absolute certainty in this reality, is as incongruous as infinite length/time dilation, or an infinitely massive/energetic object.

    Its this rather spurious belief of mine that made me most skeptical of the possibility of a spherical shell of infinite density and zero thickness, as it seems to create either absolute certainty or absolute uncertainty. Depending on your best guess of how things will pan out for FP in the parent thread. Most people say, he will certainly perish, OR you can never know what will happen. Either way, this is too certain. He should always probably something.

    Thoughts anyone?
    Last edited: Jun 30, 2006
  5. Jun 30, 2006 #4


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    Instine, I can certainly see how it's logically possible that the laws of physics would work in this way, that the conditions in a given region of spacetime could only be determined by information accessible in that region. Even then it's not clear this would mean cosmic censorship would have to apply within the singular surface, since an observer in there can probably measure the radius of the surface and the rate it's shrinking, which might be enough to tell him the mass and figure out whether the radius is smaller than the Schwarzschild radius for that mass; so he would then have enough information to deduce the existence of an event horizon surrounding him in the universe outside the surface, even if he couldn't measure the horizon directly (but then I don't think you ever can when you're within an event horizon).

    But more generally, do you agree it's logically possible that the laws of physics wouldn't work this way, and that conditions and events in a region of spacetime could be determined by information the observers in that region has no access to? And doesn't something like the Schroedinger's cat thought experiment suggest that the laws of physics in our universe don't in fact have the property you describe, since at the moment the box is opened the cat is suddenly subjected to influences that up until that moment it could have obtained no information about within the box (assume it's a really really smart cat!).
  6. Jun 30, 2006 #5


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    Here's the "Mystery of the Millenium" paper: http://arxiv.org/abs/astro-ph/0603114

    The idea is roughly this: AdS is an anti-de Sitter space - hyperbolic like the space around a gravitationg mass. The AdS is supposed to be a boundary (such as a horizon) of another space, called the "bulk". CFT is a conformally invariant physical theory. String theory is conformally invariant, but general relativity is not. The holographic thesis is that the degrees of freedom of the CFT in the bulk are completely encoded in the details oof the AdS on the boundary. Just as a two dimensional hologram can store a complete three dimensional scene.
  7. Jun 30, 2006 #6
    Lol sorry. Thats an annoying habit of mine. I just made a quick post, and then spent half an hour editing it. Sorry.

    Thank you SelfAjoint. If you break a hologram, the peices contain the entire image. Is this relevant?

    You given me some good stuff to get reading about.

    As I said before, you've got me thinking here. But what would he see?

    Infinitely fast particles? After they've been accelerated past the infinite ST curve?

    No, because although it may take a finite proper time to reach a singularity, it will take an infinite time to pass through one.

    I concede that I'm only guessing, and that physics may not conform to this plan at all, and that Schrodinger's cat is not conclusive proof of anything at all.

    All just thoughts.
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