1. What is beyond the point of singularity in a black hole and universe expands in all the three $x$, $y$ and $z$ axis?

  2. So how can one thing be on top of another when we don't know where the end point of the things is?

  3. And how does a black hole connect two parallel universes?

  4. And if there is another universe then is there another milky way, solar system and Earth?

  5. And how does a black hole connect them?


It is not necessaryly the case that black holes connect two parallel universes. But instead, that if there are parallel universes (at least one), a black hole (the sink) in one universe can connect to another universe through a wormhole (the pipe). The exit of a black hole in another universe or in another region of our universe would be a white hole (the pipe exit). If there is a parallel universe the likelihood that there is another Earth (Sun, etc.) is zero. In order for them to exist there should be a huge number of universes (and even in this case the existence of a duplicate is not granted).

To imagine how two universes are connected imagine that our universe is a two-dimensional rubber planar sheet, and the paralle universe another one that is parallel to ours and separated by some distance. The third dimension is (a fourth dimension) not observable from within the universes, but can connect them: imagine that you press one sheet and deform it such that now the two sheets are conected trough a cilindrical rubber tube (made of "space"), which is analogous to the wormhole.

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    $\begingroup$ The other end of a wormhole need not be a white hole. If the wormhole is an Einstein-Rosen bridge, for example, the other end is also a black hole; the same black hole $\endgroup$ – Jim Jan 5 '15 at 18:25
  • $\begingroup$ @Jim my understanding is that Einstein-Rosen bridges,or Schwarzschild wormholes, are vacuum solutions. Are you sure the result still holds if you have matter falling in one end? where would the incoming matter go? $\endgroup$ – user66432 Jan 5 '15 at 19:05
  • $\begingroup$ It's not a traversable wormhole, but it's a wormhole nonetheless that connects two universes and starts and ends on a black hole $\endgroup$ – Jim Jan 5 '15 at 19:12
  • $\begingroup$ but my point is your assumptionor imagination that universe is 2 dimensional sheet is wrong it is a 3 d object and if the universe is parellel so ought to be the other celestial objects in it right $\endgroup$ – itmakesmefeelgr8 Jan 6 '15 at 16:43
  • $\begingroup$ @itmakesmefeelgr8 I did not assume that our universe is 2D. I just made an analogy because you need an extra dimension to make a bridge. Thus if our universe is 3D we would need two universes parallel to each other in a fourth dimension, but most people cannot visualize this. That is why an analogy that reduces the dimension of the universe is useful (for some people) $\endgroup$ – user66432 Jan 7 '15 at 0:45

The question stated "black hole", and I will answer for a non-rotating, non-charged black hole. You can see from this Penrose diagram that the black hole interior does indeed connect to both a "universe" and a "parallel universe". However they are joined at the horizon, not the singularity which is the jagged line at top labelled $r=0$. However nothing can travel between the two so-called universe regions, because any path drawn at shallower than a $45^\circ$ angle in the diagram corresponds to motion faster than light.

In fact, half these regions do not even exist for a black hole formed from a collapsing star.



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