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Superluminous Objects and Black Holes

  1. Dec 26, 2009 #1
    Simple question to ask, but probably not so simple to explain an answer: Can an object moving faster than light (I would say a tachyon, but I don't want to since there are different theories about what a tachyon might be) escape from a black hole?

    Obviously a black hole isn't just about gravity, in the sense that things 'fall' because of gravity. Even light can't escape, since space-time curves in on itself so much. So would something that is somehow faster than light still be trapped in the same way? Or maybe moving faster than light would change how the object is experiencing time enough to make the outcome different. I can't really wrap my head around it.
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  3. Dec 26, 2009 #2

    Vanadium 50

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    Since relativity precludes objects traveling faster than light, asking how such objects would behave in the context of relativity can't be answered. It's like asking "how many sides does a square triangle have?"
  4. Dec 26, 2009 #3


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    Well, I don't think that's quite right. Relativity doesn't completely preclude FTL, but it does tightly constrain its properties. For instance, it requires that any mechanism of FTL violate causality. Bussani clearly realizes that the assumption of tachyons (or whatever) is questionable, but he wants to know what follows if you grant the assumption.

    I would say that the answer to Bussani's question has to be that tachyons could escape from a black hole. A tachyon is simply something whose world-line is always spacelike. There are certainly spacelike world-lines that lead outward from within the event horizon of a black hole.
  5. Dec 28, 2009 #4
    Sorry guys, I know my questions usually have a few ifs. Thanks for the reply though, bcrowell. That helped me picture it in my head a bit better.
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