Stephen Hawking's Black Hole Theory Confirmed by Gravitational Waves

In a landmark announcement on September 10, 2025, the LIGO-Virgo-KAGRA (LVK) Collaboration revealed that the most distinct gravitational wave signal ever recorded, GW250114, has provided the strongest evidence to date confirming Stephen Hawking's 1971 black hole area theorem. This theorem posits that when two black holes merge, the surface area of the resulting event horizon cannot be smaller than the sum of the original black holes' horizons—a fundamental prediction of black hole thermodynamics and general relativity.

The GW250114 event, detected on January 14, 2025, was observed with an unprecedented signal-to-noise ratio of 80, allowing researchers to extract details previously obscured by noise. The clarity of this signal enabled scientists to precisely measure the masses and spins of the merging black holes, as well as the final black hole's properties during the so-called 'ringdown' phase, when the new black hole vibrates and emits gravitational waves at characteristic frequencies. These measurements confirmed that the final event horizon area increased, in line with Hawking's prediction, and provided a direct test of the Kerr solution, which describes spinning black holes using only mass and spin.

The findings, published in Physical Review Letters, represent a significant advance over previous tests of Hawking's theorem, which had been limited by less precise data. The ability to distinguish two distinct gravitational wave modes in the ringdown phase was key to this breakthrough, as it allowed for a more accurate calculation of the final black hole's surface area. According to the research team, the parent black holes had a combined surface area of approximately 240,000 square kilometers, while the merged black hole's area was measured at 400,000 square kilometers, a clear increase as predicted.

This result not only cements Hawking's area theorem but also reinforces the view of black holes as thermodynamic objects, with entropy proportional to their surface area. It further validates the predictions of general relativity and the Kerr metric, which describes the geometry of spacetime around spinning black holes. The confirmation comes almost exactly ten years after LIGO's first detection of gravitational waves, marking a decade of rapid progress in gravitational wave astronomy.

Researchers from the University of Birmingham, Caltech, and other institutions emphasized the significance of the discovery. "GW250114 is the loudest gravitational wave event we have detected to date; it was like a whisper becoming a shout," said Geraint Pratten, a member of the LVK collaboration. The improved sensitivity of the detectors, achieved through years of technological advancements, was crucial in making this high-precision test possible.

The confirmation of Hawking's theorem is expected to have far-reaching implications for the study of black holes, quantum gravity, and the fundamental laws of physics. It opens the door to even more stringent tests of general relativity and the exploration of new physics in the extreme environments surrounding black holes. As LIGO and its partners continue to enhance their detectors, scientists anticipate further discoveries that could probe the nature of dark matter, dark energy, and the quantum aspects of gravity itself.