Black Holes Just Proved Stephen Hawking Right

The historic discovery meant that researchers could now sense the universe through three different means. Gravitational-wave astronomy has e...

The historic discovery meant that researchers could now sense the universe through three different means.

Gravitational-wave astronomy has entered a golden era. Since the first detection in 2015, scientists have recorded hundreds of black hole and neutron star collisions, using them to probe the deepest laws of physics. Now, a stunningly clear signal from a black hole merger has provided the strongest confirmation yet of Stephen Hawking’s black hole area theorem, a cornerstone of modern theoretical physics.

On January 14, 2025, the LIGO detectors picked up gravitational waves from a cataclysmic event dubbed GW250114 — the merger of two black holes about 1.3 billion light-years away. Thanks to a decade of advances in detector sensitivity, the signal arrived with unprecedented clarity. Scientists were able to hear multiple “tones” in the cosmic ringing, like a bell struck in space-time itself.

By studying these tones, physicists confirmed Hawking’s 1971 prediction: the combined surface area of black holes can never shrink. In GW250114, the two original black holes had a surface area roughly the size of the United Kingdom, but the merged giant swelled to nearly the size of Sweden. This increase was measured with such precision that researchers are 99.999% confident in the result — far stronger than the first test of the theorem in 2021.

Since the groundbreaking event of GW150914, the LIGO, Virgo, and KAGRA detectors have joined forces as the LVK network, now observing about one black hole merger every three days. More than 300 mergers have been confirmed, with hundreds more candidates awaiting analysis. Along the way, the LVK has uncovered neutron star collisions, mixed black hole–neutron star mergers, and the heaviest stellar-mass black hole ever recorded.

The instruments’ sensitivity is mind-boggling: they detect ripples in space-time smaller than one ten-thousandth the width of a proton. These feats are achieved through cutting-edge quantum engineering that reduces noise and allows scientists to listen deeper into the universe than ever before.

Beyond Einstein

The extraordinary detail in GW250114 also allowed researchers to perform stringent tests of Einstein’s theory of general relativity. They confirmed that the “ringdown” phase — when the newborn black hole vibrates after the merger — unfolded exactly as predicted. Multiple modes of gravitational waves were identified for the first time, strengthening confidence that Einstein’s equations still hold in the most extreme conditions nature can provide.

The LVK network is not stopping here. Scientists are already building the next generation of observatories: the Einstein Telescope in Europe, the Cosmic Explorer in the US, and LISA, a space-based interferometer led by the European Space Agency. These instruments will be capable of detecting black hole mergers from the dawn of the universe, possibly capturing echoes from the first moments after the Big Bang itself.

“This is an amazing time for gravitational-wave research,” said Massimo Carpinelli, director of the European Gravitational Observatory. “Instruments such as Virgo, LIGO, and KAGRA are opening a window into the dark universe, and the discoveries of the next decades will transform our understanding of cosmic origins.”