More or less, we have all heard about black holes, regions of space in which there is such a concentration of mass, that it generates a gravitational field so large that nothing that falls inside it can come out again, not even light.
Just as black holes are a solution to Einstein's equations, the solution of white holes could also be obtained from these equations, although none has yet been discovered and even few scientists believe that they can exist.
If black holes are gravity wells that draw all the matter and energy that surrounds them into it, white holes would be stellar objects that would expel matter and energy.
To explain the formation of black holes, there is a well-known physical process, when a large-mass star ends its nuclear fuel collapses, shrinking to reach a few tens of kilometers in diameter but with the same mass.
On the contrary, for white holes no one has yet been able to imagine a solution for its formation, although several theories are proposed, such as, for example, that these white holes are the output of black holes.
This by definition looks like a wormhole or Einstein-Rosen bridge, which have also not been discovered yet but which would allow us to move between regions of space-time too far away to do it in a conventional way.
Some have even dared to suggest that the big-bang could have arisen from a white hole arisen from the black hole of a parallel universe.
Undoubtedly, if these wormholes existed, it would be a great way to travel through space without being affected by the speed limit of light, but at the moment, they are just a nice dream and maybe we will never see one.
Although, they said the same about black holes and now it turns out that there are thousands of them only in our galaxy ...
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