BY:SpaceEyeNews.
For decades, scientists have linked black hole entropy to the area of the event horizon. That idea helped connect gravity, heat, and quantum physics in one of the most famous frameworks in modern science. It also shaped how physicists think about black holes as thermodynamic objects.
But real black holes are not frozen in place.
They grow. They spin. They merge. They may even evaporate over time through quantum effects. That makes them far more dynamic than the idealized black holes used in many classic equations.
Now, a team of physicists led by Abhay Ashtekar of Pennsylvania State University has proposed a new way to describe entropy in black holes that are far from equilibrium. Instead of relying only on event horizons, the team suggests using dynamical horizons. These horizons describe a black hole based on what is happening at a given moment, rather than depending on the entire future history of spacetime.
The result is not a rejection of Stephen Hawking’s famous framework. It is a careful extension of it. And it could give scientists a sharper language for studying black holes during their most extreme changes.
Why Black Hole Entropy Needed a Fresh Approach
The classic connection between black holes and thermodynamics began in the 1970s. Stephen Hawking and other physicists found striking parallels between ordinary thermodynamic laws and the mechanics of black holes.
In that framework, the area of the event horizon became linked to entropy. The temperature of a black hole was also tied to its mass and spin. These ideas turned black holes from purely gravitational objects into systems that seemed to carry deep thermodynamic meaning.
For half a century, this became the dominant picture.
Yet there was always a limitation. The original laws worked best for black holes in equilibrium. In other words, they were best suited to black holes that were not actively changing.
That is not how the universe usually works.
Black holes form from collapse. They feed on surrounding matter. They rotate. They collide and merge. In quantum theory, they may slowly lose energy through Hawking radiation. These are not calm, balanced situations. They are dynamic processes.
The new work addresses that gap. It asks a simple but powerful question: can the thermodynamic laws of black holes be extended to black holes that are changing in real time?
The Event Horizon Problem: A Boundary with a Future
The event horizon is one of the most famous concepts in black hole physics. It marks the boundary beyond which light cannot escape. But as useful as this idea is, it has a strange feature.
An event horizon is not defined only by what is happening nearby at one moment. Its full structure can depend on what happens later. Physicists describe this as a teleological feature.
That creates a problem for dynamic black holes.
In some situations, an event horizon can form or grow in regions of spacetime where nothing dramatic is locally happening. That means its area may not always reflect the immediate physical condition of the black hole.
For a stable black hole, this may not be a major issue. For a changing black hole, it matters a lot.
A black hole that is growing, merging, or evaporating needs a measure that follows the actual process. If the horizon used to define entropy depends partly on the future, then it becomes harder to treat it as a physical, moment-by-moment measure.
This is why the Penn State-led team looked for an alternative.
Dynamical Horizons Give Black Holes a Present-Moment Measure
The proposed solution is to use dynamical horizons.
A dynamical horizon describes a black hole using properties at a given instant. It does not depend on knowing what will happen in the future. That makes it more suitable for black holes that are actively changing.
This is the key shift.
An event horizon gives scientists a global boundary. A dynamical horizon gives them a more local and time-sensitive description. It captures the black hole while the process is happening.
This is especially important because dynamical horizons are not just abstract ideas. They are already used in numerical simulations of black holes. These simulations help scientists model complex systems, including black hole mergers.
By using dynamical horizons, researchers can connect entropy more directly to physical features such as energy, spin, and the flow of matter or radiation into the black hole.
In simple terms, this approach turns the black hole from a still object in a textbook into a system that can be tracked as it changes.
What the New Entropy Measure Changes
The new proposal does not throw away black hole thermodynamics. It makes the framework more flexible.
The older picture linked entropy with the area of the event horizon. The new work points toward the area of marginally trapped surfaces in quasi-local horizons. That phrase sounds technical, but the core idea is clear: the entropy measure should be tied to a horizon that reflects the black hole’s actual physical state during change.
This allows scientists to describe finite changes caused by real processes. That is important because the traditional first law of black hole mechanics often deals with tiny changes between nearby equilibrium states.
Real black holes do not always evolve through tiny, polite steps.
A merger can reshape the system rapidly. Infalling energy can grow the horizon. Quantum effects may slowly drain energy away. These processes require a framework that can handle motion, flux, and evolution.
The new measure gives physicists a way to discuss those changes with more precision.
It also makes the second law more quantitative. Instead of only saying that horizon area does not decrease under certain assumptions, the framework links changes in the dynamical horizon area to the flux of energy entering the black hole.
That is a major conceptual upgrade.
Black Hole Thermodynamics Beyond Equilibrium
Equilibrium is useful in physics because it simplifies complex systems. But it can also hide the most interesting behavior.
Black holes are most fascinating when they are not at rest. A black hole pulling in energy from its surroundings is changing. Two black holes spiraling together are changing. A black hole that radiates energy through quantum effects is changing.
The new research tries to extend the first and second laws of black hole mechanics into these far-from-equilibrium situations.
That matters because modern black hole science is no longer limited to static equations. Scientists now study black holes through gravitational-wave observations, high-powered simulations, and quantum theory. Each of these areas deals with black holes as active systems.
A thermodynamic framework that follows that activity could help connect several branches of physics.
It may also help researchers ask better questions. How does entropy evolve during a merger? How does horizon area respond to incoming energy? What is the best way to describe an evaporating black hole?
The new framework does not answer every question. But it gives scientists a better tool for asking them.
Why This Matters for Black Hole Mergers
Black hole mergers are among the most extreme events in the universe. They produce ripples in spacetime called gravitational waves, which have been detected by observatories including LIGO, Virgo, and KAGRA.
During a merger, the system is far from equilibrium.
Two horizons evolve. Energy moves through the system. The final black hole settles into a new state. This is exactly the kind of event where a static horizon picture can feel limited.
Dynamical horizons offer a better fit because they are designed for changing situations. They can help scientists model how horizon area, energy, spin, and entropy evolve during the process.
This does not mean scientists are directly seeing the horizon during a merger. The advance is theoretical and mathematical. But better theory matters because it improves the way simulations are built and interpreted.
As gravitational-wave astronomy grows, tools like this may become more important. They can help researchers connect what detectors measure with what theory predicts near the black hole itself.
Why Evaporating Black Holes Also Matter
The new approach may also matter for one of the deepest ideas in modern physics: black hole evaporation.
Hawking showed that black holes can radiate energy and particles. Over vast timescales, this leads to the idea that black holes may slowly shrink and eventually evaporate.
That process is not a simple equilibrium state. It involves gravity, quantum theory, temperature, and information. It is also connected to some of the biggest open questions in physics.
If a black hole can lose energy, then its entropy should be described by a framework that understands change. A dynamical-horizon approach may help researchers think more clearly about that process.
This does not solve the black hole information problem. It does not complete quantum gravity. But it may offer a more realistic thermodynamic foundation for future work.
That is why the study matters beyond one equation. It touches the larger effort to understand how gravity, heat, and quantum physics fit together.
What This Study Does Not Claim
This discovery should not be overstated.
It does not mean Hawking’s framework was wrong. It does not replace the event horizon in every context. It does not reveal a new black hole image. It is also not a telescope observation.
Instead, this is a theoretical advance.
It refines how scientists can define and calculate entropy for black holes that are not stable. It moves the conversation from idealized equilibrium systems toward the more complex black holes that exist in the universe.
That distinction matters.
Science often advances this way. A powerful old framework remains useful, but a new idea extends it into cases where the older version becomes too limited.
That is what appears to be happening here.
A Better Language for Dynamic Black Holes
Modern black hole science is becoming more dynamic. Scientists now study black holes as systems that feed, collide, rotate, and evolve.
That means the language of black hole physics must also evolve.
Dynamical horizons may give researchers a cleaner way to describe what is happening during growth, mergers, and possible evaporation. They connect better with simulations. They avoid the future-dependent problem of event horizons. They also provide a more physical way to track changes at the horizon.
The universe does not offer perfect textbook black holes. It offers active engines of spacetime.
A framework built for that reality could become an important step forward.
Conclusion: Black Holes Are No Longer Just Static Objects
Black hole entropy has long stood at the crossroads of gravity, thermodynamics, and quantum physics. The new dynamical-horizon approach does not erase that legacy. It updates it for black holes that change.
By moving beyond a purely event-horizon-based picture, physicists may now have a sharper way to describe black holes that grow, merge, spin, and possibly evaporate.
The result is not the final answer to every black hole mystery. But it may be an important step toward a more realistic understanding of black holes as they truly are: not frozen objects, but evolving systems in an active universe.
Main sources :
- Penn State official news release
Dynamic black holes explained by simple thermodynamics?
https://www.psu.edu/news/eberly-college-science/story/dynamic-black-holes-explained-simple-thermodynamics - Physical Review Letters paper record
Thermodynamics of Black Holes, Far from Equilibrium
https://link.aps.org/doi/10.1103/3c1r-v8f1 - arXiv paper record
Thermodynamics of Black Holes, far from Equilibrium
https://arxiv.org/abs/2512.11659 - arXiv related paper
Thermodynamics of dynamical black holes beyond perturbation theory
https://arxiv.org/abs/2604.00170 - Phys.org report
Dynamic black holes may obey Hawking-style thermodynamics with an adjustment
https://phys.org/news/2026-07-dynamic-black-holes-obey-hawking.html - EurekAlert release
Dynamic black holes explained by simple thermodynamics?
https://www.eurekalert.org/news-releases/1134642 - Original article you shared
Entropy of black holes determined through dynamic horizons
https://universemagazine.com/en/entropy-of-black-holes-determined-through-dynamic-horizons/