Gravitational wave Astronomy just gave us another incredible gift: The first observational confirmation for one of Stephen Hawking’s black hole predictions.Hawking's area theory was confirmed by an analysis of the 2015 first gravitational wave detection, GW150914. According to classical physics, the area at the event horizon of black holes can only get larger.This work provides us with a new tool to probe these mysterious objects and test our understanding of the Universe.Maximiliano Isi, an astrophysicist at MIT's Kavli Institute for Astrophysics and Space Research, stated that it is possible to have a zoo full of compact objects. Some of these black holes follow Einstein and Hawkings laws. Others may be different beasts.It's not as if you just take this test once and then it's over. This is the beginning.Hawking's theorem was first presented in 1971. It predicted that the area of an event horizon in a black hole's surface should not decrease but increase.The event horizon does not refer to the black hole, but rather the distance at which light speed in a vacuum is not sufficient to escape the gravitational field created by the black holes singularity. It is proportional to black holes' mass. Therefore, the event horizon should only grow.This increase-only model is curiously similar to the second law in thermodynamics. This theory states that entropy, the progression of order to disorder in the Universe, can only increase. Entropy is also attributed to black holes, and it's directly proportional with their event horizon area.Mathematically, it is clear that the area theorem holds, but observationally, it has been difficult to verify. This is because black holes emit no detectable radiation, making them extremely difficult to observe. The gravitational ripples that propagated through space-time after a collision between these mysterious objects were detected.This was GW150914, but the LIGO interferometer recorded a brief bloop at the collision that changed everything. This was not the first direct detection, but of two black holes. They formed one larger black hole when they joined forces.The black hole then faintly rang, sounding like a struck bell. Isi and his coworkers discovered how to detect this signal in 2019. They have now decoded the signal and broken it down to calculate mass and spin for the final black hole.The merger signal was also analyzed again to determine the mass and spin for the pre-merger black hole. They were able to calculate the event horizontals for all three objects because mass and spin are directly related to the area at which the event horizon occurs.If the event area could shrink, then the event area of the final merged dark hole should be smaller than the ones of the other black holes that created them. Their calculations showed that the event horizon area for both smaller black holes was 235,000 km (91,000 miles). The area of the final black hole was 367,000 km2.Isi stated that data showed that there was overwhelming evidence that the horizon area has increased following the merger and that the area law is being fulfilled with high probability."It was a relief to see that our results agree with our expectations, and that it confirms our understanding of these complex black hole mergers."In the short-term at least. Quantum mechanics is not compatible with classical physics. Hawking predicted that black holes would lose mass over long timescales in the form of Hawking radiation. It is possible that the area of an event horizon for a black hole will eventually decrease.This will need to be investigated more in the future. Isi's team has provided us with a new tool to probe other gravitational waves observations. This will allow us to gain more insight into black holes and the physics that makes up the Universe.Isi stated, "It's encouraging to think in new and creative ways about gravitational wave data, and reach answers we didn't know we could before.""We can continue to tease out bits of information that speak directly about the pillars we believe we understand." This data might reveal something unexpected one day.The research was published in Physical Review Letters.
