Theoretically, if black holes are entrances where you are sucked in and you appear somewhere else, do we come out of a white hole? I ask this because a white hole is the opposite of a black hole that cannot be entered, and only have things go OUT. So, does anyone think its certainly possible?
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2$\begingroup$ Black holes are not exactly entrances, and you don't really "appear somewhere else" when you enter a black hole, you just go into the singularity. To better understand the subject, I recommend you read the book "General Relativity from A to B" by Robert Geroch. It presents the subject in a light but precise way (and is short), I'm sure it will help you. $\endgroup$– PatrickCommented Apr 27, 2017 at 17:31
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1$\begingroup$ Possible duplicates: physics.stackexchange.com/q/7005/2451 , physics.stackexchange.com/q/45876/2451 , physics.stackexchange.com/q/156769/2451 , physics.stackexchange.com/q/288570/2451 and links therein. $\endgroup$– Qmechanic ♦Commented Apr 27, 2017 at 18:40
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3 Answers
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White Holes (WH) are a theoretical possibility. It is theoretically possible that a Black Hole (BH) and WH could exist under certain conditions.
First, Einstein-Rosen obtained a general relativity solution where the two are connected by a neck or bridge, called the Einstein-Rosen bridge. Thing is later it was calculated that it could only be stable so that something could go from one side to the other if the bridge is made of so-called exotic matter, matter with negative mass.
Nobody has detected negative mass particles. But there are some theoretical constructs in string theory and other non standard model theories that have the possibility of exotic matter having appeared early after the birth of the universe, and they or some resulting wormhole may be detectable. We have found nothing like this, but we can't yet see (electromagnetically) much closer than 380000 years from the Big Bang, because of the recombination wall. Gravitational. Wave detectors in space, if big enough, could detect gravitational waves from earlier on, and possibly match them to what some of these theoretical constructs imply. So, nothing found yet, but it is not theoretically un-detectable, so semi-fair game.
The same is true with Einstein Cartan theory, with torsion in the gravitational connection (i.e., a non symmetric connection), where a wormhole may be possible. Nothing found yet supports Einstein-Cartan theory, but not fully disproven either.
So, yes, they are possible, though no evidence and maybe it just does not happen. Papers and so on still come out on it once in a while. Some people are studying it where it could be the beginning g of the universe with some models they propose about string theory M-branes pre Big Bang that led to it.
Not speculative, but far from any real good reason to think they are there somewhere. See the wiki article at https://en.m.wikipedia.org/wiki/White_hole
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Well, not really. White holes, to the best of our knowledge, do not exist. They are theoretical, and are simply a mathematical by-product of general relativity. Working within those theories, it is the opposite of a black hole, yes. However, it does not mean that they are a pair, or a set. So even if white holes actually existed, they wouldn't be the output to a black hole, and wouldn't be linked.
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$\begingroup$ I'd phrase "the opposite" as more "they are time-reversed black holes". $\endgroup$ Commented Apr 27, 2017 at 18:42
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$\begingroup$ That would be just as valid, I suppose, but no more true. After all, they can't exist here, so it's a moot point. $\endgroup$ Commented Apr 27, 2017 at 18:47
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1$\begingroup$ No, it is precisely true. A white hole solution is a black hole solution with the time-reversal operation applied. One can think of several other, inequivalent, notions of the "opposite" of a black hole (say, a Schwarzschild black hole with negative mass parameter) $\endgroup$ Commented Apr 27, 2017 at 20:01
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Short answer: We don't know yet but probably not (at least to me there seems to be no reason for it).
Black holes are just objects with very strong gravity. Black holes have been observed in contrary to white holes which are just theoretical concept. White holes should posses antigravity. Neither antigravity neither white holes have yet been observed. Everything that falls into the black hole gets atomized by very strong tidal force. If there was a white hole emitting matter from a black hole it would be very difficult to confirm that it's the same matter that once fell into black hole.
Lets assume there are several black holes and several white holes. You fall into a black hole. Which white hole would you pop out?
How do you distinguish the mass of the black hole itself from things that fall in? If you don't then even "pieces" of black hole would be emmited by white hole and the black hole would loose mass. In fact black holes could loose mass due to Hawking radiation but there is probably no link between Hawking radiation and white holes.
