White holes are a theoretical region of singularity and spacetime, which cannot be accessed from the outside, although light, energy-matter, and information can escape from them. In this sense, it is the opposite of a black hole, which can be accessed only from the outside and from which light, energy-matter, and information cannot escape it.
White holes emerge in the hypothesis of eternal black holes. In addition to a black hole area in the future, such a solution of the Einstein field equations has a white hole area in its past. However, this area does not exist for black holes that have developed through gravitational collapse, nor are there any observed physical methods through which a white hole could be created.
White hole Origin
Russian cosmologist Igor Novikov put forward the possibility of the existence of white holes in 1964 CE. White holes are prophesied as part of a solution to the Einstein field equations known as the maximally extended account of the Schwarzschild metric, representing an eternal black hole with no rotation and no charge. Here, “maximally extended” means the idea that the spacetime should not have any “edges”: for any potential trajectory of a free-falling particle (following a geodesic) in the spacetime dimension, it should be possible to carry on this path arbitrarily far into the particle’s future unless the trajectory catches a gravitational singularity indeed like the one at the heart of the black hole’s interior. In order to satisfy this condition, it turns out that in addition to the black hole center region, which particles penetrate when they fall through the event horizon from the outside, there must be a different white hole interior region, which enables us to extrapolate the particles’ trajectories which an outside spectator sees rising away from the event horizon. For an apparent observer outside using Schwarzschild coordinates, infalling particles take an infinite time to enter the black hole horizon extremely far in the future, while outgoing particles which pass the observer have been moving outward for an endless time since intersecting the white hole horizon infinitely far in the past. The white hole/black hole appears “eternal” from the prospect of an outside observer, in the sense that particles moving outward from the white hole central region can pass the observer at any time, and particles traveling inside which will ultimately reach the black hole interior region can also pass the spectator at any time.
Big Bang/supermassive white hole
A glimpse of black holes first introduced in the late 1980 CR might be interpreted as shedding light on white holes’ nature. Some scientists have suggested that when a black hole forms, a Big Bang may occur at the singularity/core, which would develop a new universe that expands outside of the parent universe.
The Einstein–Cartan-Sciama-Kibble theory of gravity protracts general relativity by eliminating a constraint of the affine connection’s symmetry and, regarding its antisymmetric section, the torsion tensor, as a dynamical variable. Torsion typically accounts for the quantum-mechanical spin (intrinsic angular momentum) of matter.
According to general relativity theory, the gravitational collapse of a adequately compact mass forms a singular black hole. In the Einstein–Cartan theory, however, the minimum coupling between Dirac spinors and torsion creates a repulsive spin–spin interaction, which is extremely significant in fermionic matter at incredibly high densities. Such an exchange prevents the development of a gravitational singularity. Instead, the collapsing matter on the opposite side of the supposed event horizon reaches an immense but limited density and rebounds, creating a regular Einstein–Rosen bridge. The other end of the bridge becomes a new, developing baby universe. For spectators in the baby universe, the parent universe seems like a single white hole. Accordingly, the observable universe is the Einstein–Rosen center of a black hole existing as one of probably many inside a larger universe. The Big Bang was suggestively a nonsingular Big Bounce at which the observable universe had a minimum, finite scale factor.