Ten years after its groundbreaking first detection, the Laser Interferometer Gravitational-Wave Observatory (LIGO) has achieved another monumental milestone. The detection of GW250114, the loudest gravitational wave event ever recorded, provides unprecedented clarity into the nature of black holes, confirming predictions made by Albert Einstein, Stephen Hawking, and Roy Kerr. This signal, described as a 'whisper becoming a shout,' allowed for rigorous testing of Einstein's theory of general relativity.
The collision of two black holes, each roughly 32 times the mass of our sun, generated the gravitational waves detected by LIGO. This event dramatically validates Hawking's prediction regarding the event horizon of black holes – that the total area of the resultant black hole's event horizon following a merger is always larger than the combined area of the original black holes. GW250114 vividly demonstrated this, with the combined surface area of the progenitor black holes roughly equivalent to the size of the United Kingdom, while the resulting black hole's surface area was approximately the size of Sweden.
Furthermore, the detection strongly supports Kerr's geometry, which describes the spacetime around a rotating black hole (a Kerr black hole). Following the merger, black holes enter a 'ringdown' phase, emitting gravitational waves at specific frequencies. LIGO's detection clearly identified these frequencies, confirming their behavior aligns precisely with Kerr's predictions. This is remarkable, as it suggests that black holes, regardless of mass (even those billions of times more massive than our sun), can be fully characterized by only two values: mass and spin.
This leap forward in gravitational wave astronomy is a testament to the continuous technological advancements in LIGO. The observatory, with its detectors in Washington and Louisiana capable of measuring spacetime distortions 700 trillion times smaller than a human hair, has pushed the boundaries of what's possible. The planned addition of a fourth detector in India promises further improvements in precision and localization of gravitational wave sources.
The significance of this research, published in Physical Review Letters, extends beyond confirming existing theories. It paves the way for deeper understanding of black holes and potentially offers insights into a unified theory of quantum gravity – a holy grail of theoretical physics. The sheer power and clarity of GW250114 offer a glimpse into a universe that Einstein himself might have found astonishing. This remarkable achievement underscores LIGO's transformative impact on our understanding of the cosmos, confirming that a new era of gravitational wave astronomy has just begun.
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Originally published at: https://www.space.com/astronomy/gravitational-wave-detector-confirms-theories-of-einstein-and-hawking-this-is-the-clearest-view-yet-of-the-nature-of-black-holes
