Black hole cosmology
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A black hole cosmology (also called Schwarzschild cosmology or black hole cosmological model) is a cosmological model in which the observable universe is the interior of a black hole. Such models were originally proposed by theoretical physicist Raj Kumar Pathria,[1] and concurrently by mathematician I. J. Good.[2] These ideas were presented as conjectures based on analogies, not derived from exact solutions of Einstein's field equations.
More recent studies by, among others, Nikodem Popławski,[3] the observable universe is the interior of a black hole existing as one of possibly many inside a larger parent universe, or multiverse. However, some such models rely on speculative extensions to general relativity, such as torsion, and are not grounded in mainstream physics.
Variants
Cosmological Natural Selection
According to Lee Smolin a collapsing black hole causes the emergence of a new universe on the "other side". See Cosmological natural selection
Shockwave Cosmology
Shockwave cosmology, proposed by Joel Smoller and Blake Temple in 2003, has the "big bang" as an explosion inside a black hole, producing the expanding volume of space and matter that includes the observable universe. This black hole eventually becomes a white hole as the matter density decreases with the expansion. A related theory proposes that the acceleration of the expansion of the observable universe, normally attributed to dark energy, may be caused by an effect of the shockwave.[4]
Cosmology with Torsion
According to general relativity, the gravitational collapse of a mass into a sufficiently compact area forms into a Schwarzschild black hole. In the Einstein–Cartan–Sciama–Kibble theory of gravity, however, it forms a regular Einstein–Rosen bridge, or wormhole. Schwarzschild wormholes and Schwarzschild black holes are different mathematical solutions of general relativity and the Einstein–Cartan theory. Yet for observers, the exteriors of both solutions with the same mass are indistinguishable. The Einstein–Cartan theory extends general relativity by removing a constraint of the symmetry of the affine connection and regarding its antisymmetric part, the torsion tensor, as a dynamical variable. Torsion naturally accounts for the quantum-mechanical, intrinsic angular momentum (spin) of matter. The minimal coupling between torsion and Dirac spinors generates a repulsive spin-spin interaction, which is significant in fermionic matter at extremely high densities. Such an interaction prevents the formation of a gravitational singularity. Instead, the collapsing matter reaches an enormous but finite density and rebounds, forming the other side of an Einstein-Rosen bridge, which grows as a new universe.[5] Accordingly, the Big Bang was a nonsingular Big Bounce at which the universe had a finite, minimum scale factor.[6]
Black Hole Universe
In 2025, a new model proposed a non-singular cosmological solution[7] in which the Universe originates from the gravitational collapse of a finite overdensity followed by a quantum bounce inside a black hole. This model, derived from an exact analytical solution to Einstein's equations combined with quantum degeneracy pressure, avoids a singularity and naturally generates a period of accelerated expansion. The resulting "Black Hole Universe" scenario suggests that our observable Universe could be the interior of such a black hole, with testable predictions such as a small positive spatial curvature and a non-zero cosmological constant.
Evidence
Any such model requires that the Hubble radius of the observable universe be equal to its Schwarzschild radius, that is, the product of its mass and the Schwarzschild proportionality constant. This is indeed known to be nearly the case, but might be a coincidence.[8]
A paper, published in March 2025 claims that, of a sample of over 200 early galaxies, around two thirds spin clockwise, whereas only half would be expected to do so. One possible explanation for this anomaly is that we might be inside a black hole; as all known black holes spin and this spin would influence any galaxies inside one. Alternatively it might be that the cosmos spins slowly for some other reason, or there may be some problem with the data.[9]
See also
References
- ^ Pathria, R. K. (1972). "The Universe as a Black Hole". Nature. 240 (5379): 298–299. Bibcode:1972Natur.240..298P. doi:10.1038/240298a0. S2CID 4282253.
- ^ Good, I. J. (July 1972). "Chinese universes". Physics Today. 25 (7): 15. Bibcode:1972PhT....25g..15G. doi:10.1063/1.3070923.
- ^ Popławski, N. J. (2010). "Radial motion into an Einstein-Rosen bridge". Physics Letters B. 687 (2–3): 110–113. arXiv:0902.1994. Bibcode:2010PhLB..687..110P. doi:10.1016/j.physletb.2010.03.029. S2CID 5947253.
- ^ Clara Moskowitz (2009-08-17). "'Big Wave' Theory Offers Alternative to Dark Energy". Space. Retrieved 2025-07-06.
- ^ Popławski, N. J. (2010). "Cosmology with torsion: An alternative to cosmic inflation". Physics Letters B. 694 (3): 181–185. arXiv:1007.0587. Bibcode:2010PhLB..694..181P. doi:10.1016/j.physletb.2010.09.056.
- ^ Popławski, N. (2012). "Nonsingular, big-bounce cosmology from spinor-torsion coupling". Physical Review D. 85 (10): 107502. arXiv:1111.4595. Bibcode:2012PhRvD..85j7502P. doi:10.1103/PhysRevD.85.107502. S2CID 118434253.
- ^ Gaztañaga, E.; Kumar, K. S.; Pradhan, S.; Gabler, M. (2025). "Gravitational bounce from the quantum exclusion principle". Physical Review D. 111 (10): 103537. Bibcode:2025PhRvD.111j3537G. doi:10.1103/PhysRevD.111.103537.
- ^ Landsberg, P. T. (1984). "Mass Scales and the Cosmological Coincidences". Annalen der Physik. 496 (2): 88–92. Bibcode:1984AnP...496...88L. doi:10.1002/andp.19844960203.
- ^ Sutter, Paul M. "Do We Live inside a Black Hole?". Scientific American. Retrieved 2025-04-30.