Could our Universe be inside a wormhole that is itself part of a black hole that is inside a much larger universe?
This scenario, in which our universe is born inside a wormhole (also known as the Einstein-Rosen Bridge), has been proposed by the theoretical physicist at Indiana University, Nikodem Poplawski. In this study, Poplaswski uses a Euclidean mathematical model to suggest that all black holes can have wormholes, and that, in turn, there are universes created at the same time as black holes.
Poplawski relies on a Euclidean coordinate system known as isotropic coordinates to describe the gravitational field of a black hole and to model the radial geodetic motion of a massive particle within it.
By studying the radial motion across the event horizon of two different types of black holes - Schwarzschild and Einstein-Rosen black hole, both legitimate solutions of General Relativity - Poplawski admits that only experiment or observation can reveal the motion of a particle that falls into a real black hole. But he also notes that since observers can only see the outside of the black hole, the inside cannot be seen unless the observer enters or resides in it.
"This condition could be met if our Universe were inside a black hole that exists in a larger universe," he says. Because Einstein's Theory of Relativity does not choose a temporal orientation, if a black hole can be formed by the gravitational collapse of matter across an event horizon, it is also possible to reverse the process in the future. Such a process would describe the explosion of a white hole: matter arising from an event horizon in the past, such as the expanding universe. "
A white hole is connected to a black hole by means of an Einstein-Rosen bridge (or wormhole) and is hypothetically the temporary inversion of a black hole. Poplawski's article suggests that all astrophysical black holes, not just Schwarzschild's and Einstein-Rosen's, can have Einstein-Rosen bridges, each with a new universe inside it that formed simultaneously with the hole black. "From this it follows that our Universe could have formed within a black hole that exists within another universe," he points out.
Continuing the study of the gravitational collapse of a dust sphere in isotropic coordinates, and applying the present investigation to other types of black holes, it is observed that if the Universe is born inside an Einstein-Rosen black hole, the problems could be avoided that scientists observe in the Big Bang theory, and the problem of loss of information from black holes, which states that all information about matter is lost when it passes through the event horizon.
This isotropic coordinate model of the Universe as a black hole could explain the origin of cosmic inflation, Poplawski says.