Artist impression of a white hole. (Credit: University of Sheffield)
In a nutshell
- New research suggests that black holes could transition into white holes, ejecting matter and potentially preserving information, challenging the long-held view that black holes are inescapable cosmic dead ends.
- By applying quantum rules to black hole interiors, scientists found that singularities, points where physics breaks down, are replaced by “quantum bounces,” preventing complete collapse and allowing space and time to continue.
- The study proposes that dark energy, the mysterious force driving the universe’s expansion, also provides a natural way to measure time inside black holes, potentially linking two of the biggest mysteries in physics: quantum mechanics and gravity.
SHEFFIELD, England — Black holes might not be the cosmic dead ends astronomers have long believed them to be. A new international study suggests something that sounds like science fiction but is rooted in serious mathematics: black holes might evolve into white holes, effectively “bouncing” matter back out into the universe.
Black holes have fascinated scientists and the public for decades. According to Einstein’s theory of general relativity, they contain a “singularity” at their center, a point where matter gets crushed to infinite density and the laws of physics simply break down. This mathematical infinity has bothered physicists because it’s like hitting a brick wall in our understanding of reality.
The new research, published in Physical Review Letters, takes a fresh approach by modifying Einstein’s theory slightly. Instead of treating dark energy, the mysterious force causing our universe to expand, as fixed, they allow it to vary. This seemingly small tweak creates a natural way to track time inside a black hole and apply quantum physics rules.
“While time is generally thought to be relative to the observer, in our research time is derived from the dark energy which permeates the entire universe,” says study co-author Steffen Gielen from the University of Sheffield, in a statement. “We propose that time is measured by the dark energy that is everywhere in the Universe, and responsible for its current expansion. This is the key idea that helps us understand what happens inside a black hole.”
The Quantum Bounce: From Black to White
In the traditional view of a black hole, once you cross the point of no return (the event horizon), you’re doomed, and you’ll inevitably be crushed at the singularity. But this new quantum picture shows something much more interesting.
When the researchers applied quantum rules to their model, they found that both the horizon and the singularity were replaced by “quantum bounces.” Instead of space shrinking to zero and time ending, the volume of space reaches a minimum size but never disappears completely. Then, remarkably, it begins to expand again, transforming the black hole into a white hole, which expels matter rather than consuming it.
“Hypothetically, you could have an observer go through the black hole, through what we think of as a singularity, and emerge on the other side of the white hole. It’s a highly abstract notion of an observer but it could happen, in theory,” says Gielen.
The researchers found that near what would classically be the singularity, tiny quantum fluctuations, small, temporary changes in energy, become extremely important. These fluctuations prevent the complete collapse of space and time, allowing for this transition to a white hole.
Dark Energy: The Universal Clock
To reach these conclusions, the researchers used a simplified model of a black hole with a flat boundary (rather than the spherical shape of real black holes). While this simplification made the math more manageable, the researchers believe their core findings would apply to real black holes too.
According to current scientific consensus, dark energy makes up roughly 68% of the universe and drives its accelerating expansion. Researchers used this same dark energy to provide a natural reference for measuring time inside a black hole.
This approach could help solve one of the biggest puzzles in physics: the black hole information paradox. This paradox emerged when Stephen Hawking discovered that black holes slowly evaporate over time. If everything that falls into a black hole is completely destroyed at the singularity, then information is permanently lost, something quantum physics doesn’t allow. But if black holes transform into white holes, the information could eventually come back out.
What This Means for Our Universe
Similar mathematical approaches could potentially explain what happened at the Big Bang, often described as a time-reversed black hole singularity. If quantum effects prevent the complete collapse at the center of a black hole, they might similarly have prevented a true “beginning of time” at the Big Bang. Also, if black holes do transform into white holes, they might leave distinctive signatures in gravitational waves or in radiation patterns that future instruments could detect.
For now, this remains cutting-edge theoretical work, but it paints a fascinating picture of cosmic renewal. Rather than being dead ends where matter meets its final doom, black holes might be more like cosmic recycling centers where matter and energy are processed and eventually returned to the universe in a new form.
Paper Summary
Methodology
The researchers studied a simplified version of a black hole with high symmetry to make the mathematics more manageable. They used an approach called “unimodular gravity,” where dark energy can vary rather than remain fixed. This provided a natural way to measure time inside the black hole. They then applied quantum mechanics principles to this model, focusing particularly on how the volume of space would behave as it approached what would classically be the singularity. A key requirement in their approach was that information must be preserved throughout the process—a fundamental principle in quantum physics.
Results
The calculations showed that both the classical black hole singularity and horizon are replaced by “quantum bounces” where space reaches a minimum size but never shrinks to zero. As their model approached what would classically be the singularity, quantum effects became dominant. Instead of collapsing completely, the volume of space bounced back and began expanding again—effectively transitioning from a black hole to a white hole. In these transition regions, quantum fluctuations grew dramatically, indicating a breakdown of our usual understanding of space and time. These results remained consistent across different variations of their model.
Limitations
This study uses a highly simplified model of a black hole that’s different from the spherical black holes that exist in nature. While the researchers argue that their findings about singularities should apply universally, their specific conclusions about horizons might not apply to all black holes. The study only looks at the inside of the black hole and doesn’t address how this modified interior would connect to the space outside. The research is purely theoretical with no direct experimental verification currently possible. Additionally, their approach introduces a preferred way of measuring time, which some physicists might view as contradicting Einstein’s principle that physical laws should be the same in all reference frames.
Discussion and Takeaways
The central finding is that quantum mechanics naturally prevents the formation of singularities in black holes when information preservation is required. If correct, this would mean information isn’t truly lost in black holes but could eventually emerge through a black-hole-to-white-hole transition. These findings might also apply to other cosmic singularities like the Big Bang, potentially replacing the idea of a universe beginning from a singular point with a quantum bounce from a previous state. The research highlights an important tension between Einstein’s relativity and quantum mechanics regarding how time works at a fundamental level.
Funding and Disclosures
The research was funded by the Royal Society through the University Research Fellowship Renewal URF\R\221005 for Steffen Gielen. Lucía Menéndez-Pidal was supported by the Leverhulme Trust. The paper was published under the Creative Commons Attribution 4.0 International license, with funding from SCOAP³ (Sponsoring Consortium for Open Access Publishing in Particle Physics).
Publication Information
The research paper “Black Hole Singularity Resolution in Unimodular Gravity from Unitarity” was authored by Steffen Gielen from the University of Sheffield, United Kingdom, and Lucía Menéndez-Pidal from Universidad Complutense de Madrid, Spain. It was published on March 11, 2025, in Physical Review Letters (volume 134, issue 10, article 101501).
