Science › Creation theories
A universe born inside a black hole
1992· Theory
SpeculativeA serious idea with no experimental proof yet.
The idea that our universe began inside a black hole in a parent universe, and that black holes here may spawn universes too.
See it on the Science map →How it works
Inside a black hole, collapse might not end in a singularity but bounce, as in the Big Bounce, into a new expanding region cut off from its parent. In 1992 Lee Smolin added evolution: each baby universe inherits slightly altered constants. Universes whose constants make many black holes leave more offspring, so a typical universe should be tuned to make black holes, and with them stars and carbon. Versions also come from R. K. Pathria (1972) and Nikodem Popławski (2010).
Why it matters
It ties origins to objects we can study, and it is one of few multiverse ideas that makes testable claims about our own constants.
How we know
No direct evidence. Smolin predicted neutron stars could not exceed about 1.6 times the Sun's mass; neutron stars of about two solar masses, found since 2010, seriously challenge that prediction.
Still a mystery
Whether a black hole's interior can really bounce, how a baby universe would inherit 'mutated' laws, and whether our constants truly maximize black holes are all open.
Connections (3)
▸A universe born inside a black hole says our universe began inside one of the Black holesSpeculative
The relationship
Collapse inside a black hole might stop at a maximum density, as in bounce models, and rebound into a new expanding region. That region would grow into its own spacetime, cut off from the parent behind the horizon. From outside, nothing looks unusual: just a black hole. From inside, the rebound would look like a Big Bang.
How the link was found
R. K. Pathria proposed in Nature (1972) that our universe could be a black hole's interior; Lee Smolin (1992) and Nikodem Popławski (2010) developed bouncing versions.
Is it proven?
Unproven. An often-noted coincidence, that the mass within about 14 billion light-years (where expansion reaches light speed) would form a black hole about that size, holds automatically in a flat universe, so it is not evidence.
Open questions and mysteries
Can black-hole interiors bounce at all? Would a baby universe grow large enough to make galaxies? Nothing inside a horizon can be observed.
▸A universe born inside a black hole would explain by cosmic natural selection Fine-tuning: a universe built for life?Speculative
The relationship
Smolin borrowed Darwin's logic. If each black hole spawns a universe with slightly mutated constants, universes good at making black holes have more 'offspring'. After many generations, nearly all universes are tuned for black holes. Making black holes takes stars, and long-lived stars need carbon and chemistry, so life-friendly constants come along as a by-product.
How the link was found
Lee Smolin, 'Did the universe evolve?' (1992) and 'The Life of the Cosmos' (1997), building on Wheeler's idea that laws might change at each rebirth.
Is it proven?
Untested and disputed. Smolin claims any small change to our constants should reduce black-hole production; critics argue some changes would increase it, which would refute the idea.
Open questions and mysteries
How would constants be passed on and mutated? Does the theory really explain life, or only black holes?
▸A universe born inside a black hole offers an answer to What came before the Big Bang?Speculative
The relationship
Its answer: before our Big Bang was a collapsing star or other massive object in a parent universe. Its matter, crushed to extreme density, rebounded into our expanding space. In Popławski's version, spinning particles twist spacetime, supplying the repulsion. Our universe might then inherit a preferred direction from the parent black hole's spin.
How the link was found
Pathria (1972); Smolin (1992); Nikodem Popławski, in papers from 2010, using the Einstein–Cartan extension of relativity, which includes this twisting, called torsion.
Is it proven?
No evidence. A 2025 study of early galaxies seen by JWST reported more spinning one way than the other, which some linked to a parent's spin; it is unconfirmed and may be an observational bias.
Open questions and mysteries
Where did the first parent universe come from? The idea moves the origin question back a generation without answering it.