The Big Bang theory has long dominated our understanding of the universe’s origin, describing a moment when all of space, time, and energy emerged from an infinitely dense point. However, a groundbreaking study suggests an alternative: our universe might have been born inside a black hole. This radical notion is being explored by a group of physicists led by Professor Enrique Gaztañaga from the Institute of Cosmology and Gravitation at the University of Portsmouth. Their paper, published in Physical Review D, proposes a “gravitational bounce” that could replace the singular event of the Big Bang with a continuous cycle of collapse and rebirth.
The concept suggests that the universe may have originally existed within a giant black hole created in a massive “parent” universe. As matter collapsed inward, quantum mechanics would prevent all the matter from occupying the same state, generating pressure that stops the collapse before a singularity forms. The energy trapped inside the black hole would then bounce outward in a burst of expansion, forming a new universe.
The End that Becomes a Beginning
This hypothesis, known as the Black Hole Universe model, uses two of nature’s most mysterious forces, gravity and quantum mechanics, to illustrate how they may work together rather than against each other. Gaztañaga explains that their examination “looks in, rather than out.” Instead of starting with an expanding universe and questioning its origins, they asked what happens when a large mass of matter collapses. He states that “gravitational collapse does not have to end in a singularity,” and under the right conditions, a bounce becomes not only possible but inevitable.
Quantum Pressure and the Rebound of the Universe
The heart of the idea lies in a simple equation describing how pressure changes as matter compresses. During collapse, the pressure becomes negative, mimicking the dark energy effect believed to be pushing the universe apart today. This negative pressure causes rapid expansion, resembling the inflation phase cosmologists associate with the Big Bang.
Unlike theories relying on hypothetical particles or new laws of physics, this model uses the same degeneracy pressure that prevents white dwarfs and neutron stars from collapsing completely. As density approaches a critical limit, quantum pressure pushes back, creating a bounce radius where contraction stops and expansion begins. This bounce could explain the inflationary growth of the universe, its nearly flat geometry, and the current acceleration of its expansion without exotic fields or arbitrary constants.
A Universe Within a Black Hole
From an external perspective, collapsing matter would appear as an ordinary black hole. The event horizon, the boundary layer of a black hole, would trap everything falling within. However, inside the black hole, remarkable occurrences unfold: matter bounces and inflates, forming a new region of spacetime, and a universe like ours emerges beyond that boundary.
This connection between black holes and cosmic genesis suggests an intriguing scenario: every black hole could be a seed for a new universe, implying that our universe may have originated from one of these cosmic wombs. Inside that black hole, time would flow normally, even if an outside observer saw a stationary black hole frozen in spacetime.
Gaztañaga and his team predict that our universe should have a small but measurable curvature, slightly closed like the surface of a sphere, with a curvature of approximately –0.07 ± 0.02.
A Cycle Without Singularities
Classical physics posits that both black holes and the Big Bang end in singularities, where density is infinite and the laws of nature cease to apply. These singularities have long haunted cosmological theories. However, by incorporating quantum effects, this model eliminates singularities.
In this model, the universe’s beginning is not a sharp explosion but a smooth bounce. Matter compresses into a high-density quantum state, stops collapsing, and then expands again. The Big Bang becomes a transition event or bounce, emerging from a precursory phase of cosmic evolution.
The model’s simplicity is appealing, directly linking the cosmos’s genesis to physics already applicable in dense stellar cores. It replaces the mystery of an initial singularity with a bounce mechanism grounded in well-established principles of quantum mechanics and general relativity.
Testing the Bounce With New Eyes
The theory will soon face real-world tests. Gaztañaga is the Science Coordinator for ARRAKIHS, an upcoming European Space Agency mission designed to investigate the faint outer regions of galaxies. The spacecraft, equipped with four wide-angle telescopes, will explore the distant halo of gas and dark matter, revealing faint glimpses of galaxy formation and evolution.
The faint outer regions contain what astronomers call the “fossil record” of galaxy formation. If the universe indeed originated from a gravitational bounce, these regions would preserve remnants of the early universe’s physical characteristics, potentially deviating from Big Bang predictions.
Observing these regions could open new methods for understanding the genesis of spacetime: were we born from an explosion and expansion, or did we emerge from a gravitational bounce before collapsing into one? Gaztañaga believes these implications extend beyond resolving initial technical questions. “One of the main strengths of the model,” he says, “is that it makes predictions that can be tested in the real world.”
If evidence confirming the gravitational-bounce model is measurable, the impact could forever change cosmology. The model suggests singularities do not form, and the “something from nothing” paradigm is better described by cycles of collapse and renewal. Every black hole could be a gateway to a new universe, restructuring creation as a process rather than an instantaneous event.
This model could unify gravity with quantum mechanics, two of the most powerful yet disconnected theories in physics, and drive future missions like ARRAKIHS to quantitatively test how galaxies and broader cosmological structures came to be. It reimagines existence as a living, regenerating system—not static, but breathing. It invites reverence, wonderment, and contemplation about our role in existence and what existence means as a catalyst for change over time.
Research findings are available online in the journal Physical Review D.
