A groundbreaking development in theoretical physics may finally solve one of the most troubling enigmas in modern science: the singularity at the heart of black holes.
A team of physicists has proposed a new framework for black holes that removes the need for a central singularity — the point where the laws of physics, as we know them, break down entirely. This new model, published in Physics Letters B in February 2025, suggests that black holes can exist as stable, extremely curved regions of space-time without the infinite-density core that has long haunted scientists.
This artist concept illustrates a supermassive black hole with millions to billions times the mass of our Sun. Supermassive black holes are enormously dense objects buried at the hearts of galaxies. NASA/JPL-Caltech
“If black holes do not have singularities, then they are much more ordinary,” said Robie Hennigar, a researcher at Durham University and co-author of the study. “The singularity is the most mysterious and problematic part of a black hole. It’s where our concepts of space and time literally no longer make sense.”
What Is a Singularity — And Why It Matters
Black holes are regions of space where gravity is so strong that not even light can escape. Their outer boundary, the event horizon, acts as a cosmic point of no return. Once something crosses it, it’s lost to the outside universe. According to Einstein’s 1915 theory of general relativity, space-time curves in response to mass and energy — and black holes represent an extreme version of this curvature.
When physicists model black holes using Einstein's equations, they encounter a singularity at the core — a point of infinite density where the equations break down. “Physicists don’t like infinities,” said Pablo Antonio Cano Molina-Niñirola, a theoretical physicist at the University of Barcelona’s Institute of Cosmos Sciences and a member of the research team. “Infinities usually mean the theory is incomplete or something unphysical is happening.”
This singularity has posed a major challenge in uniting general relativity — which governs large-scale cosmic phenomena — with quantum mechanics, which governs the subatomic realm. Many scientists have speculated that a yet-undiscovered “theory of everything,” likely rooted in quantum gravity, will eventually eliminate the need for singularities.
A New Kind of Black Hole: Singularities Not Required
Rather than wait for a full theory of quantum gravity, Hennigar, Molina-Niñirola, and their colleagues have taken a bold step forward. They developed an effective theory — a modified version of general relativity — that changes how gravity behaves in highly curved space-time. This allows the theory to model black holes without invoking singularities.
“In our model, the space-time collapse stops before reaching infinite density,” said Molina-Niñirola. “Instead of a singularity, the center of the black hole becomes a highly warped but stable region. It’s static — it doesn’t contract — so, hypothetically, an observer could remain there, assuming they could survive the enormous gravitational forces.”
These “regular black holes” are composed entirely of vacuum — meaning no matter is required for their structure — though the theory can be adapted to include matter as needed. “It might sound strange, but you can have black holes without any matter even in general relativity,” Hennigar explained.
More Questions Than Answers?
While this new model avoids the singularity paradox, it raises other fascinating possibilities. For example, if singularities don’t exist, then everything that enters a black hole must eventually come back out.
“One idea is that matter falling into a regular black hole could exit through a white hole in another universe — or perhaps a disconnected region of our own universe,” Molina-Niñirola said. “It sounds exotic, but it’s one of the few viable outcomes if singularities are truly absent.”
Such a scenario is not without its challenges. It raises new questions about causality, energy conservation, and the ultimate fate of matter and information in the universe.
Can This Theory Be Tested?
The biggest hurdle for the new theory is proving it. Since black holes trap all information behind their event horizons, scientists cannot directly observe what happens inside. Still, there are indirect paths to test the theory.
Molina-Niñirola points to gravitational wave astronomy — the observation of ripples in space-time generated by cosmic collisions — as one promising avenue. These waves let scientists probe intense gravitational fields and could one day reveal deviations from general relativity that support the new model.
Another possibility lies in the study of the early universe. If the theory is correct, evidence might exist in the form of primordial gravitational waves produced during the Big Bang's inflationary phase — a signature that scientists are still searching for.
Perhaps most intriguingly, the theory implies that when black holes evaporate via Hawking radiation, they leave behind microscopic black holes — objects that may be a candidate for the mysterious dark matter that permeates the cosmos.
“If dark matter turns out to be made of tiny black holes,” Molina-Niñirola said, “that would be an indirect proof in favor of our model — and a sign that singularities are not part of nature after all.”
While the proposed model doesn’t solve every puzzle in physics, it represents a significant step toward reconciling general relativity with the quantum world. It offers a compelling new vision of black holes — not as monstrous singularities tearing at the fabric of reality, but as comprehensible (if still extreme) objects governed by laws we might one day fully understand.
“Our work provides answers to some mysteries, but it opens others,” Molina-Niñirola said. “The journey toward a full theory of gravity is far from over — but with each step, we get a little closer.”
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