Black Holes: Key to the beginning and end of the universe?

Discussion in 'Astronomy, Exobiology, & Cosmology' started by Electro522, Nov 2, 2011.

  1. billvon Valued Senior Member

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    We are talking many, many, many orders of magnitude more pressure - the point at which even atomic structure collapses.

    You don't even need that. When the forces are so great that the atomic structure of a material breaks down, there is no structure you can imagine that will prevent a collapse of a hollow shell. And that's true whether the shell has a vacuum in it, or even ordinary matter.

    Once the collapse starts, gravity increases even further, and the result is a neutron star.

    (Note that the only way to collect that much matter is to start with a massive star - thus neutron stars are born once massive stars exhaust the fuel that was keeping them 'inflated' against gravity.)
     
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  3. Aqueous Id flat Earth skeptic Valued Senior Member

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    the center of gravity of a hollow shell of uniform density is equal to the c.g. of a solid sphere of uniform density: the center of roundness, no? not sure what that matters.

    just thinking here. so a star burns up most everything except its neutrons which infall, eventually it supernovas if adequate mass.. then it's a neutron star and maybe a few configurations like an emitter, but if criticality is reached, it goes to BH.

    some kind of physics is being preserved, some apparently not. the cone is weird. like a mirage than you never actually reach. space compresses.. and density in compressed space means what? you forgot to recalibrate for relativity?

    the notion of crushing forces of gravity seems weird to me. or spaghettification if you believe that. it seems like all these notions should be recalibrated for the alterations in space, time and mass - like it seems they would normalize, so if you somehow fell in, every thing would remain the same for you, but the external universe would fold itself the other way? a white hole appearing to you?

    there's no doubt there's a lethal amount of neutrons crushed into an extremely small space even in our own sun. but, from the point of view of the neutron, what's the apparent change in reality? that would seem to be the analogy for being "in" a BH looking out.

    space is collapsing (apparently, ie to the observer in the observation frame) as if there is a relativistic velocity at some fraction of light speed. but there is no apparent motion. in fact, au contraire, motion seems to freeze approaching the horizon.

    then again what if the neutrons are forever infalling, and very quickly, freeze that. like at a horizon, and it would appear they are only moving in, say, angstroms per eon. sci-fi? maybe. But Dr. Who's TARDIS is such a cool way to invoke the counterintuitive: bigger on the inside than on the outside? So big, in fact he's never gotten around to checking the whole thing out? so do infalling neutrons "open" space for themselves to keep rushing into while the outer observation shows the radius of the core to be stationary? because that makes it a little easier for me to leap from one incredibly profound notion - a neutron core - to another one: a BH.

    and yes, I like the idea of a naked singularity as the ultimate reality. (pre-space). yes, also very analogous: bigger on the inside than out. so if the big bang were not an explosion, but an implosion, generating space within, until some criticality is reached whereby space is "ripped" apart (sci-fi again), leaving non-space in the ruptures, non-space being that which does not propagate light though the intrinsic impedance of free space, ie matter.

    Just a crazed notion I've had. I like to think of the event horizon exactly as the condition of v=c in the Lorentz transformation. Time stops? Space collapses? what does it mean to have no space? this to me is like the naked singularity. and the infinitely small point (tying this to the opening remarks) is the one and only point where time vanishes and space collapses. this singular point (single and singular) projects itself as the unfathomably enormous shell enclosing reality? and projects itself as the apparent disk we call the horizon of a black hole? And, I guess Brian Greene would say, co-exists with every string? would this not be the actual expected result of "ripping" space? because non-space is naked, singular, timeless, dimensionless, and all of those qualities seem to fit with the notion of whatever it means to be "at" the horizon. Matter and singularity being "of the same substance?"

    Anyway hope this is not perceived as trolling. I of course have no evidence so I am not positing like an allegation or anything. Just sharing some of the wonderment that goes on in my mind which indeed may be garbage but really I'm just thinking "what if", you know?
     
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  5. wellwisher Banned Banned

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    The closest we can get to a black hole is light years away. This phenomena is not right in front of you so you can directly test theories of black holes. From far away is there is more creative liberty. When we started to explore Mars with rockets, the theory developed from afar with telescopes, did not expect what they saw from close up. The creative liberty enjoyed for decades was lost. Black holes theory is lucky because its have so much slack at thousands of time further than Mars.

    Say we placed our hollow sphere of mass 10 light years away, and we need to use this distance to observe the hollow mass center of gravity theory. It is now easier on the theory, since subtle things can be ignored, since we can't see them that great distance. I am trying to level the playing field between theory and observational limitations. The dogma of black holes is based on slack observation.

    Say we have an earth sized hollow shell. If we drop a ball into a hole in the shell, it will fall toward center of gravity and then move back and forth between opposite sides of the shell like a spring. This motion should give off low level waves at long wavelength, since the wave motion is SR within GR.

    Say instead we had a mass of material at center of gravity within our hollow shell. Again we will drop the ball. Because of the central mass, there is damping in the wave or spring. We might still be generating half waves of SR in GR. Maybe someone could explain if we could see half waves of energy, or whether this be dark? I ask because I am not really sure what to expect. Whatever it may be, does the center of galaxies generate this at light years away.
     
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  7. KilljoyKlown Whatever Valued Senior Member

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    Are you kidding? Only mass generates gravity. If there is no mass at the center of a spherical shell, there will be no gravity generated there.

    All the gravity will be generated from the shell, and any center of gravity will depend on where you are in relation to that shell. From anywhere within that shell any center of gravity will not be at the center of the sphere.
     
  8. OnlyMe Valued Senior Member

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    I think things are being mixed up here. If the sphere is hollow and somewhere in "space", there would be vacuum both inside and outside the sphere. Even if you place the sphere in a gas cloud it is likely that there is far more preassure on the acrylic sphere of a deep sea exploration submersible than on any hollow sphere in space.

    Only the effects of gravity would be significant, whether you assume those to be conventionally gravitational or the result of some Lense-Thirring (frame-dragging) effect.


    As KJ's post points out, if the sphere is hollow its center of gravity is at its center only when viewed from outside the sphere. To this add that unless the total mass of the sphere itself is gravitationally significant and non-uninform or generating forces greater than the molecular bonds of the sphere material, would the sphere colapse inward under forces generated by the sphere itself.

    Think again about the acrylic spheres used in deep under sea exploration subs'. The acrylic is not strong enough to withstand the preassure if it were a window instead of a sphere. (think large window not small porthole)

    Try it with an egg. Carefully.... End to end an egg can withstand a great deal more pressure, without breaking, than it can side to side. If done correctly you cannot break the egg by squeezing it in your hand, end to end. If the preassure becomes unequal (this should maybe be "when" it becomes unequal), you will wind up with a hand full of egg. (This demonstration or experiment should be done with a raw egg.)

    As long as the sphere material is structurally uniformn, only when you put some mass inside the sphere or an unequally distributed force outside the sphere would the sphere become unstable and colapse.

    Neutron stars and BHs, to the best of our understanding are not hollow. The gravitational forces involved in both are far greater than any atomic or molecular forces we can even imagine. Or than most of us can imagine...
     
  9. billvon Valued Senior Member

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    Agreed. The pressure is the result of gravity, not any gas external to the sphere.
     
  10. KilljoyKlown Whatever Valued Senior Member

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