A centrepiece of Prof Stephen Hawking's theory of black holes states that black holes can only grow. Thanks to precision observations made with the Laser Interferometer Gravitational-Wave Observatory (LIGO), this theory has now been verified for the first time.
By Prof Thomas Hertog
This marks a new milestone exactly 10 years after LIGO’s first detection of gravitational waves.
Above all, it demonstrates that advanced observations of gravitational ripples can reach into the deepest roots of physics. In the future, they may even reveal that the Universe is a hologram.
Time without time
The theoretical discovery that there might be a hologram hiding underneath our familiar reality of space and time ranks among the most important, baffling and far-reaching physics discoveries of the late-20th century.
Physicists still don’t agree on what form this hologram might take, but just the mere idea of a hologram has opened up implications that have already changed theoretical physics beyond recognition.
For decades, physicists had struggled to seal the marriage of General Relativity and quantum theory. The discovery of holography did exactly that.
It showed that gravity and quantum theory need not be water and fire, but can be like yin and yang: two very different yet complementary descriptions of the same physical reality.
Physical systems can be gravitational and quantum at the same time, holography says, albeit in different dimensions. This is the shift in perspective brought about by holography.
A diagram depicting how the Universe may emerge from a hologram, where entangled qubits on its boundary encode the information shaping time and space. Image credit: Thomas Hertog
Perhaps our entire expanding Universe might be a hologram. This is Hawking’s final theory of the Universe.
In the holograms we’re familiar with, a third dimension of space emerges from the light projected on a surface.
In the cosmos-as-a-hologram idea, however, it would be the dimension of time that can be holographically encoded. That is, the evolution of the Universe might be a holographic projection.
Hawking’s final thoughts on time emerging as a holographic projection are encapsulated in a disc-like image.
The outer circle represents a timeless hologram made up of countless entangled quantum bits, or qubits, like the spin state of particles.
From this, the evolution of an expanding Universe is thought to emerge. At the centre of the disc lies the origin of the Universe, which expands outward in the so-called “radial direction.”
It’s as if there’s a code operating on the entangled qubits that brings about the Universe, and this emergent process is what we perceive as the flow of time.
We can venture back in time, towards the interior of the disc, by taking a fuzzier view of the outer hologram, like zooming out of a picture.
Eventually, however, one runs out of bits. This would be the origin of time in the holographic vision of the cosmos.
If true, there could be nothing before the Big Bang, because the past that holographically emerges simply doesn’t extend further back.
Are black holes the ultimate holograms?
In the 1970s, Jacob Bekenstein and Stephen Hawking discovered, with an ingenious thought experiment, that black holes aren’t empty bottomless pits, as Einstein’s theory of General Relativity suggests.
Rather, they store a vast amount of information about their history in a mysterious microscopic structure.
Black holes would actually be by far the most efficient hard drives in the Universe, Hawking suggested.
Colleagues Thomas Hertog and Stephen Hawking questioned the theory Hawking put forward in his book, A Brief History of Time. Image credit: Thomas Hertog
For example, Sagittarius A*, the huge black hole lurking in the centre of the Milky Way, can store the equivalent of no less than 10⁸⁰ gigabytes.
All the data in the Google storage banks could easily fit into a black hole smaller than the size of a proton.
Hawking even derived a precise mathematical formula for the amount of information, or entropy, that black holes contain.
For one, it implies that the entropy of black holes grows like the surface area of their event horizon and not like their interior volume.
This was the first glimmer of holography in modern physics.
The storage capacity of black holes isn’t determined by their interior volume, but by the area of their horizon surface.
It’s as if, from a quantum viewpoint, black holes don’t quite have an interior, but are actually holograms.
Sagittarius A*, the supermassive black hole at the centre of the Milky Way, captured using 2017 Event Horizon Telescope observations. Image credit: Science Photo Library
Gravitational waves
Gravitational waves are tiny vibrations in the fabric of space. Their existence was first predicted by Albert Einstein in 1916.
Today, more than a century on, the very first detections of these elusive ripples are racing like a tsunami through physics and astronomy.
Why?
Because the observational discovery of gravitational waves marks the birth of an entirely new astronomy.
Illustration showing two black holes merging and generating gravitational waves. Image credit: Science Photo Library
Ever since Galileo’s first telescopic observations in 1609, nearly everything we’ve learnt about the Universe has come through light observations.
The 21st century may become the era where humanity explores the cosmos through gravitational waves as well.
It’s as if humanity is developing a new sense, learning to listen to the Universe instead of only looking at it.
The exceptionally powerful detection registered as GW250114 showed two black holes approximately 1.3 billion light-years away colliding and combining into a larger black hole.
The analysis confirmed Hawking’s theory that the total surface area of the resulting black hole increases after a merger.
A technician inspects one of LIGO’s four core mirrors, which help measure distances affected by gravitational waves. Image credit: LIGO/CALTECH/NSF/Matt Heintze
Fresh evidence
Researchers are also investigating whether primordial black holes formed shortly after the Big Bang may eventually provide evidence for Hawking radiation.
Advanced observations of gravitational waves can reach into the deepest foundations of physics. Image credit: Shutterstock
In February 2026, researchers at UMass Amherst suggested that an ultra-high-energy neutrino detected by the KM3NeT Collaboration in 2023 might be linked to a primordial black hole explosion.
If confirmed, future neutrino observations could provide insight into the quantum dynamics of black holes and potentially support the theory of the Universe as a hologram.
Black hole radiation
Hawking’s famous equation for black hole temperature united multiple fields of physics into a single framework.
By combining General Relativity with quantum mechanics, Hawking concluded that black holes emit tiny amounts of thermal radiation.
This process, now known as Hawking radiation, means black holes slowly lose mass and eventually evaporate.
That discovery triggered one of the biggest puzzles in modern physics.
If information enters a black hole, what happens to it when the black hole disappears?
Quantum theory says information cannot be destroyed.
At first, physicists believed the information would be lost forever.
Hawking himself famously warned that “physics is in serious trouble.”
But holography offered a possible solution.
Researchers now believe Hawking radiation may contain hidden information encoded within subtle quantum entanglements between particles.
The result is a radically different understanding of black holes, gravity, and perhaps reality itself.
Physics, for now, may have been saved.