hawking’s Theorem Confirmed with Unprecedented Precision: LIGO‘s Latest Finding Validates Black Hole Growth
For decades,Stephen Hawking’s “area theorem” – the assertion that the total surface area of black holes can never decrease – remained a cornerstone of theoretical physics,yet lacked direct observational proof. Now, thanks to a decade of relentless technological advancement and the amazing sensitivity of the Laser Interferometer Gravitational-Wave Observatory (LIGO), that proof has arrived. A recent detection, designated GW250114 (signaling a gravitational wave arrival on January 14, 2025), has provided the strongest evidence yet confirming Hawking’s groundbreaking theory.
This landmark achievement isn’t just a win for astrophysics; it’s a testament to human ingenuity and our ability to probe the universe’s deepest mysteries. Since its first run in 2015, the LIGO-Virgo-KAGRA (LVK) collaboration has identified approximately 220 candidate black hole mergers – a figure more then double that of the first three observing runs combined. This exponential increase in detections highlights the dramatic improvements made to these incredibly complex instruments.
The power of Precision: Listening to the universe’s Whispers
Gravitational waves, ripples in the fabric of spacetime predicted by Einstein, are notoriously faint. LIGO’s detectors are, quite literally, the most precise measuring devices ever created. They detect distortions smaller than 1/10,000th the width of a proton – a staggering 700 trillion times smaller than a human hair.
The GW250114 event itself wasn’t radically different from LIGO’s initial detection (GW150914) – both involved the collision of black holes roughly 1.3 billion light-years away, each with masses 30 to 40 times that of our Sun.However, the clarity of the GW250114 signal is what sets it apart. Ten years of refinement, focused on minimizing instrumental noise, has allowed scientists to “hear” the event with unprecedented detail.
“We can hear it loud and clear, and that lets us test the fundamental laws of physics,” explains Katerina Chatziioannou, a Caltech assistant professor of physics and a key member of the LIGO team, in a recent study published in physical Review Letters (https://doi.org/10.1103/kw5g-d732).
Verifying Hawking’s Area Theorem: A Deeper Dive
The LVK team leveraged the detailed frequencies of the gravitational waves emitted during the merger to provide the strongest observational support for the black hole area theorem to date. Essentially, they where able to observe two black holes growing in size as they spiraled inward and ultimately merged into a single, larger black hole – precisely as Hawking’s theorem predicted.
This isn’t the first attempt to test the theorem.An initial analysis of the GW150914 signal in 2021 yielded a confidence level of 95%. However, the cleaner data from GW250114 has boosted that confidence to an astonishing 99.999%.
The late Stephen Hawking himself was keenly interested in the possibility of observational verification. Nobel Laureate Kip Thorne recalls Hawking inquiring about LIGO’s potential to test his theorem shortly after the 2015 gravitational-wave detection. Sadly, Hawking passed away in 2018, before witnessing the confirmation of his theory. “If Hawking were alive,he would have reveled in seeing the area of the merged black holes increase,” Thorne reflects.
Unlocking the Secrets of the Ringdown Phase
The most challenging aspect of this analysis lay in accurately determining the surface area of the final, merged black hole. Measuring the surface areas of the pre-merger black holes is relatively straightforward as they orbit and generate strong gravitational waves. Though, the signal becomes more complex after the collision, during what’s known as the “ringdown” phase.
This phase sees the newly formed black hole vibrate, much like a struck bell. Researchers were able to precisely measure the details of this ringdown, allowing them to calculate the mass and spin of the final black hole and, crucially, its surface area.
For the first time, the team successfully identified two distinct gravitational-wave modes within the ringdown phase. These modes, analogous to the different tones a bell produces, are
