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I ran across a news article saying that using loop quantum gravity it turns out nothing really falls into the singularity after all. The article is here but it is formidably armored; they say the singularity is avoided but I don't know how. Still, it gets me going on a far cruder point from long ago...
The major issue I have with the idea of a black hole is that it seems well agreed you can see a photon from infalling matter at any time, with no upper limit. Sometimes this is presented as being the "ghost" of something that has "already fallen" into a black hole, but this seems clearly unsupportable -- nothing can fall in faster than a photon, no matter how much gravity pulls on it, so surely the photon's emission takes up the shorter part of the time involved from the perspective of an outside observer. I don't see any way to avoid concluding that whatever was dumped into the hole has to "actually" be there, somewhere outside the event horizon.
The classic Schwarzschild metric diagram gives what looks like a nice explanation for the reason why. Space becomes infinitely curved at the event horizon -- not the singularity. Which means that no matter how fast something falls in, it is limited to travelling at the speed of light through an infinite amount of space. I am tempted to compare this to the classic rubber-sheet model of geodesic motion through spacetime -- the marble bends into gravity wells, or collides into planets should the wells be filled, or starts falling down a black hole and never stops... but never reaches the center either.
Problem with this is that someone has modified our articles on stuff like Wormhole and Schwarzschild metric and I think gravity well also to say that the classic diagrams of spacetime curvature and EPR bridges have absolutely nothing to do with gravity wells, that one is a Flamm's paraboloid that is totally not the same as a gravity well because it's a spacelike surface (though I have to say, I thought the same might be true of gravity wells). There are an abundance of citation needed tags in some of those sections.
I see a similar debate playing out at [1] with one guy saying what I am here, and true, more than one disagreeing, which doesn't bode well but I am short of convinced. But nobody there pulls out the Flamm thing.
If I could take an EPR bridge as a valid diagram, then it would suggest a very intuitive basis for black holes, white holes, wormholes etc. where things falling into heavy gravity simply encounter lots of extra space, which may curve to allow them to use the energy they gained infalling to carry them away. (A black hole should certainly be a "white hole" in the later universe when mass and light are very rare and even the faintest Hawking radiation is warmer than everything else) It would seem like spacetime simply "defends itself", with a time delay, to avoid an ugly singularity. Even if something is stuck "near" (in a 2-D sense) the event horizon, in virtually flat spacetime, when a massive object plunges into the far end of the black hole and expands the event horizon, it should be very difficult for the gravity from that object ever to reach the infalling object! And if it could, I'd think the expansion of the event horizon would mean the outward displacement of the vertical neck of the EPR bridge?
I understand of course that from the point of view of the person falling, they could pass the event horizon in the sense that after an infinite time on ice around a perpetual non-evaporating black hole they would reach the horizon, having experienced almost no subjective time in the duration.
Anyway, I at least want clarification on how to reestablish a sense of a rubber sheet model and make direct comparisons between gravity wells and black hole curved spacetime, and whether c explicitly applies to any motion on the rubber sheet and whether down is really "down" in wormholes. Wnt ( talk) 14:45, 24 December 2018 (UTC)
Science desk | ||
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< December 23 | << Nov | December | Jan >> | December 25 > |
Welcome to the Wikipedia Science Reference Desk Archives |
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The page you are currently viewing is a transcluded archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages. |
I ran across a news article saying that using loop quantum gravity it turns out nothing really falls into the singularity after all. The article is here but it is formidably armored; they say the singularity is avoided but I don't know how. Still, it gets me going on a far cruder point from long ago...
The major issue I have with the idea of a black hole is that it seems well agreed you can see a photon from infalling matter at any time, with no upper limit. Sometimes this is presented as being the "ghost" of something that has "already fallen" into a black hole, but this seems clearly unsupportable -- nothing can fall in faster than a photon, no matter how much gravity pulls on it, so surely the photon's emission takes up the shorter part of the time involved from the perspective of an outside observer. I don't see any way to avoid concluding that whatever was dumped into the hole has to "actually" be there, somewhere outside the event horizon.
The classic Schwarzschild metric diagram gives what looks like a nice explanation for the reason why. Space becomes infinitely curved at the event horizon -- not the singularity. Which means that no matter how fast something falls in, it is limited to travelling at the speed of light through an infinite amount of space. I am tempted to compare this to the classic rubber-sheet model of geodesic motion through spacetime -- the marble bends into gravity wells, or collides into planets should the wells be filled, or starts falling down a black hole and never stops... but never reaches the center either.
Problem with this is that someone has modified our articles on stuff like Wormhole and Schwarzschild metric and I think gravity well also to say that the classic diagrams of spacetime curvature and EPR bridges have absolutely nothing to do with gravity wells, that one is a Flamm's paraboloid that is totally not the same as a gravity well because it's a spacelike surface (though I have to say, I thought the same might be true of gravity wells). There are an abundance of citation needed tags in some of those sections.
I see a similar debate playing out at [1] with one guy saying what I am here, and true, more than one disagreeing, which doesn't bode well but I am short of convinced. But nobody there pulls out the Flamm thing.
If I could take an EPR bridge as a valid diagram, then it would suggest a very intuitive basis for black holes, white holes, wormholes etc. where things falling into heavy gravity simply encounter lots of extra space, which may curve to allow them to use the energy they gained infalling to carry them away. (A black hole should certainly be a "white hole" in the later universe when mass and light are very rare and even the faintest Hawking radiation is warmer than everything else) It would seem like spacetime simply "defends itself", with a time delay, to avoid an ugly singularity. Even if something is stuck "near" (in a 2-D sense) the event horizon, in virtually flat spacetime, when a massive object plunges into the far end of the black hole and expands the event horizon, it should be very difficult for the gravity from that object ever to reach the infalling object! And if it could, I'd think the expansion of the event horizon would mean the outward displacement of the vertical neck of the EPR bridge?
I understand of course that from the point of view of the person falling, they could pass the event horizon in the sense that after an infinite time on ice around a perpetual non-evaporating black hole they would reach the horizon, having experienced almost no subjective time in the duration.
Anyway, I at least want clarification on how to reestablish a sense of a rubber sheet model and make direct comparisons between gravity wells and black hole curved spacetime, and whether c explicitly applies to any motion on the rubber sheet and whether down is really "down" in wormholes. Wnt ( talk) 14:45, 24 December 2018 (UTC)