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Assume wormholes exist. One hole allows matter to pop out of another hole somewhere else in the universe.

If one end of the wormhole is swallowed by a black hole, then no information can get from that end to the other hole.

If the wormhole acts as some kind of gateway to another part of the universe, wouldn't that mean that the entire universe would be swallowed by the black hole? ie. the wormhole end is an entry portal to the entire universe, so if that is inside the black hole, wouldn't that mean the entire universe is then in the black hole?

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    $\begingroup$ We need a speculative tag. $\endgroup$
    – HDE 226868
    Jan 6, 2015 at 16:00
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    $\begingroup$ I don't see any problem with this post compared to most others... Sure, it's speculative, but does that mean that there shouldn't have been questions about BHs if SE existed before the 90s? If you downvote; please leave a comment to explain why. $\endgroup$ Jan 6, 2015 at 22:01
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    $\begingroup$ @zhermes I didn't downvote; I thought about voting to close. I'll leave a comment nonetheless. I think this should be closed because we don't know if wormholes exist, or how one would interact with a black hole. Answering this properly would require a long answer with general relativity - although you did a good job answering. Oliver Watkins - I meant a tag for things like this that rely on speculative concepts. $\endgroup$
    – HDE 226868
    Jan 6, 2015 at 23:09
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    $\begingroup$ @frodeborli But we have solid evidence for black holes. We have no evidence for wormholes. $\endgroup$
    – HDE 226868
    Jun 8, 2015 at 15:27
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    $\begingroup$ I love how people are born to ask such questions. Challenging the so called frontier of physics. $\endgroup$
    – LocalFluff
    Jan 29, 2016 at 14:36

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The concept of a wormhole is, of course, highly speculative. None the less, such a phenomenon could take many forms - most simple something which to outside observers looks like a blackhole on each end of the wormhole. Alternatively, a traversable wormhole (see for example Morris & Thorne 1988; which has the same basic topology but no horizon), could still behave for the most part* like a normal, massive object.

In either case, if one end were 'swallowed' by a blackhole, it is unclear to me whether it would remain stable (i.e. remain a wormhole). In the case of a non-traversable wormhole, if it remained stable, it would continue to look like a blackhole on each end --- one end of which now merged with another blackhole, and subsequently more massive. A traversable wormhole on the other hand could (extremely hypothetically) still remain traversable if there were enough exotic matter, or it could retain the horizon from the blackhole it merged with and be no-longer traversable.

All wormhole metrics that I've seen are more or less symmetric, and thus either have no horizon, or horizons on both ends... I don't think it would be possible to have a horizon on only one side --- allowing something to fall into an apparent blackhole on one side, and come out of a wormhole on the other. Even so, however, remember that a blackhole isn't a magic vacuum --- and wouldn't 'suck in' the 'entire universe'.

*A traversable wormhole is believed to require some sort of 'exotic matter' in the neck, which may behave somewhat differently...

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  • $\begingroup$ I don't think you can differentiate between the two ends of a wormhole. Both ends would be the same - i.e. it's non-orientable. If there is a black hole next to a wormhole, would not the gravitational effects of the other black hole also work through the wormhole itself? $\endgroup$
    – frodeborli
    Jun 8, 2015 at 7:51
  • $\begingroup$ You made an interesting statement that "a blackhole ... wouldn't 'suck in' the 'entire universe'". It makes sense, of course, but it's a characterization of at least one aspect of spacetime. It would be really bad if there was something that would eat all of spacetime if it was created. I guess that the existence of the universe to this point is evidence such a thing doesn't and maybe can't exist. $\endgroup$ Aug 8, 2016 at 23:26
  • $\begingroup$ One more possibility: the traversable wormhole spits the black hole out the other side. Assuming you had a traversable wormhole, this result will be dependent on trajectory and other factors. $\endgroup$
    – Joshua
    Jan 14, 2022 at 5:13

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