While the idea that the black holes may connect with the other regions in the universe or the other universes entirely has been considered in great depth, this is a pure speculation.
Yes, this is just a mere theory that has been believed by few without any evidence that could firmly support this.
Some physicists have attempted to combine quantum mechanics with the general theory of relativity, concluding that the black holes may not contain a singularity.
But wait. What is this Singularity? Why was it believed that the point of singularity inside the black holes could act as portals for another universe? To know this you must understand what is the point of singularity.
What is the point of singularity?
Singularity is the point where the density becomes infinite. If the singularity is there then it would act like a passage or tunnel or Portal for another universe. But how?
In physics, spacetime is any mathematical model that fuse three-dimensional space and the one dimension of time into a single 4‑dimensional continuum.
So consider, we all live in this SpaceTime sheet which spread throughout the universe. Which would look something like the one in this picture.
you can notice that every planet is disturbing this space-time sheet ( you can see the dip made on the sheet by every planet).
This curvature made by each object is proportional to the mass of the object. More the mass, more the curvature would be.
If the mass become infinite then what will happen? Something like this in the below picture will happen.
So, in the case of blackholes where the point of singularity exists, the mass becomes infinite, Time and space become into the single dimension and this will puncture the space-time sheet.
So this opened up the possibility that the black holes are a shortcut to other universes – Actual Tunnels through the space-time called ‘Wormholes‘, may be a better bet for transversing between universes. This was predicted by Einstein.
This idea is so fascinating that it was adopted in many sci-fi films for the past decades.
But there is no evidence that that the point of singularity may present inside the black hole and no wormholes have yet been discovered.
Doubts remain that they could they could naturally occur at all.
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