New black hole merger bolsters Hawking area theorem

The clearest black hole merger signal yet, recorded by LIGO in January 2025, offers new insights into these mysterious objects. Credit: Maggie Chiang/Simons Foundation

Back in 1971, the late physicist Stephen Hawking made an intriguing prediction: The total surface area of a black hole cannot decrease, only increase or remain stable. So if two black holes combine, the newly formed black hole will have a larger surface area. This became known as Hawking's area theorem. Analysis of the gravitational signal from a black hole merger detected in January provides the best observational evidence to date in support of Hawking's theorem, according to a new paper published in the journal Physical Review Letters.

The breakthrough just happens to coincide with the 10-year anniversary of the LIGO collaboration's Nobel Prize-winning first detection of a black hole merger. A second paper has been submitted (but not yet accepted), placing ...