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According to many physicists, any matter near a black hole is obviously gravitated towards it, and transported to a parallel universe. As far as i know, black holes are made up of material particles, as is everything else in the universe, so why isn't it sucked up in the parallel universe? And if it is true that it sucks up everything and transports it to a parallel universe, shouldn't it be bright in that parallel universe, as light is also pulled into it? If so, why doesn't our universe have these?

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  • $\begingroup$ I'm confused, I was under the impression that a black hole was just a point of extremely high gravity, to a point causing a singularity in the Einstein field equations, and that a wormhole was the theoretical object OP (and everyone else so far) referred to. $\endgroup$
    – Matt Scott
    Feb 20, 2013 at 16:17
  • $\begingroup$ If the black hole is rotating or charged it is possible to follow a timelike path through the event horizon and back out without hitting the singularity. However the bit of the universe you re-emerge into is causally disconnected from your starting point because there is no way back without travelling faster than light. See the question I linked to in my answer above for a detailed discussion of this. $\endgroup$ Feb 20, 2013 at 16:38
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    $\begingroup$ BTW, black holes are, for most intents and purposes, not made of anything but pure gravitational influence. The event horizon is just a surface in spacetime - it is not a solid object. Also, black holes are not vacuum cleaners - they are really no better than stars or planets or anything else with mass at sucking things in from a distance. $\endgroup$
    – user10851
    Feb 20, 2013 at 17:07
  • $\begingroup$ My own impression has been that black holes are a pattern which gravity assumes under certain conditions bearing on the location of the gravitational patterns characterizing other objects. Plainly this has much to do with the "mass-energy equivalence" discovered by Einstein. PSE is a site where the translation of mathematics (whose understanding, on my part, is very inadequate) into languages (whose interpretation had been my profession for decades) is attempted. What I'd hoped to suggest, in a comment evidently misinterpreted by staffers, was the use of the OP's formalism (seen elsewhere). $\endgroup$
    – Edouard
    Nov 22, 2022 at 1:34
  • $\begingroup$ I was appalled by the rapidity with which an earlier comment of mine, bearing on language use, was yanked: I've been married for half a century to a woman whose "race"is not my own, and most of my friends reside in a rooming house operated by Ananda Marga (an Indian sect). The most profound verbal conversations I've ever had have been with persons whose native languages are Bengali and Hindi, so I want to set the record extremely straight as to my own view of PSE's functionality. "Suction" just seemed a little too two-dimensional to be optimal in a description of spherical objects. $\endgroup$
    – Edouard
    Nov 22, 2022 at 1:45

2 Answers 2

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It's a common claim that certain types of black holes provide a gateway to a parallel universe, however there are two problems with this claim. Firstly, although it's true that trajectories can be traced through the event horizon and back out again, it isn't clear whether this is physically meaningful or just a mathematical trick. In fact if recent suggestions about firewalls are correct anything crossing the event horizon will simply be incinerated.

Secondly, even if the trajectories are physically meaningful and firewalls don't get in the way, the universe you reach is not a parallel universe but just a causally disconnected bit of the same universe you and I live in.

Lastly, even if you can travel through the black hole to reach a causally disconnected bit of the universe, for any observer outside the black hole the trip will take an infinite time. So we could only see something emerge from a black hole if the black hole was infinitely old. Clearly this isn't the case.

You might be interested to have a look at my answer to Entering a black hole, jumping into another universe---with questions where I go into more detail about the travel through a black hole. Also in that answer I mention the book The Cosmic Frontiers of General Relativity by William J. Kaufmann and this book deals with your question. From outside the event horizon you can't see anything travelling out of the black hole, but if you jump into the black hole then in principle once inside the event horizon you could see light coming from other parts of the universe, or from parallel universes if you wish to describe them so.

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  • $\begingroup$ Yes you are right that the black hole needs to be of an infinite age so that we can see something coming out of it but in this universe of uncertenity can,t we have one because unverse is much older thn my grand grand mother. $\endgroup$
    – Deiknymi
    Feb 20, 2013 at 16:34
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    $\begingroup$ Observers outside the event horizon would have to be able to observe the event horizon for an infinite time to see anything coming out through it. Basically this means the black hole and the universe it's in would have to be infinitely old. You may have heard that infalling matter takes an infinite time to reach the event horizon, and the infinite time taken to emerge from the event horizon is just the corollary of this. $\endgroup$ Feb 20, 2013 at 16:44
  • $\begingroup$ @JohnRennie --If causal disconnection from everywhere outside it would not leave the interior of a black hole (even if it's empty) definable as a separate "local universe" in a "multiverse", what would? (I've looked at the earlier answer you've cited, and I'm not objecting to your assertion, but I'm trying to bring it down to a verbal level I can understand: Does it require picturing the entire interior of a BH as one relatively huge, ball-shaped geodesic?) $\endgroup$
    – Edouard
    Nov 20, 2022 at 20:33
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    $\begingroup$ @Edouard the region outside the horizon is causally disconnected from the region inside, but the region inside is not causally disconnected from the region outside. That is, the event horizon acts a one way barrier. $\endgroup$ Nov 21, 2022 at 5:29
  • $\begingroup$ That makes sense of the "Hawking Points" (effects of Hawking radiation on the CMB), whose observation may have been the decisive factor in Penrose's 2020 Nobel Prize for his past- and future-eternal cosmological model, while also allowing (in the context of the Einstein-Cartan version of relativity) for Nikodem Poplawski's past- and future-eternal model, where it would allow occupants of the local universe germinating within a black hole to observe effects of spatial expansion. (As long as it's proven to last forever, I'll buy it....) $\endgroup$
    – Edouard
    Nov 21, 2022 at 6:42
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This model you are talking about, parallel universes and black holes connecting with them is a popularized version of a model that is not mainstream physics.

Black holes exist because we have seen their influence, we have not seen any white hole sources of particles, this is an experimental fact. This is the reason that the black holes of mainstream physics are described as:

a region of spacetime from which gravity prevents anything, including light, from escaping.1 The theory of general relativity predicts that a sufficiently compact mass will deform spacetime to form a black hole. Around a black hole there is a mathematically defined surface called an event horizon that marks the point of no return

The matter that falls in the black hole adds to its mass and its attractive strength. There is no other universe where it leaks out. That is a science fiction view at the moment.

A black hole is not eternal, as quantum mechanics tells us that it slowly radiates away the energy it has accumulated.

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  • $\begingroup$ that,s my point if we haven,t seen one so far than how can we say that there is one on the other side of the black hole because whatever id there should be here. If there any correction to made to my statement please do and then answerme back :) $\endgroup$
    – Deiknymi
    Feb 20, 2013 at 16:41
  • $\begingroup$ It's too simple a view to bother posting as an answer, but, have you ever noticed that a "bus line" (to "take" a very everyday example) is not a single, continuous bus, shaped like a line extending all the way between one terminus and another? "Black holes" have, physically, a similar relation to literal, material reality: More than 90 have been spotted astronomically, by the surviving member of each of 90-odd binary pairs (most stars are usually considered to be in binary systems, even though our own star, "the" sun, isn't) continuing to follow an "eliptical" (nearly circular) orbit. $\endgroup$
    – Edouard
    Nov 22, 2022 at 0:11
  • $\begingroup$ This is not to say that there aren't languages (of which you, to judge by your location, may know several) that would describe things differently: For instance, some "native American" languages describe the "floating of a boat" in terms of an object being pressed upward by water beneath its hull, which is actually a more completely "realistic" view than describing a boat as doing the same thing ("floating") that snowflakes and stars do. I just don't think a "physics" question without some relation to mathematics is really a "physics question". $\endgroup$
    – Edouard
    Nov 22, 2022 at 0:20
  • $\begingroup$ I appreciate the reinstatement of these innocuous and speculative comments, just as I'd sincerely appreciate any information about their possible inaccuracy: I'm here to learn, not to insult. $\endgroup$
    – Edouard
    Nov 22, 2022 at 4:25
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    $\begingroup$ I agree with your "a "physics" question without some relation to mathematics is really a "physics question"" Mianstream physics means heavy dependence on mathematics to fit observations. $\endgroup$
    – anna v
    Nov 22, 2022 at 4:29

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