One of Stephen Hawking‘s most famous theorems has been proven right, using ripples in space-time caused by the merging of two distant black holes.
The theorem was first proposed by Hawking in the year 1971. It claimed that it was impossible for a black hole to decrease in size over time. The theorem was based on Einstein’s theory of relativity that defined gravitational waves and black holes.
This rule interests physicists because it is closely related to another rule that appears to set time to run in a particular direction: the second law of thermodynamics, which states that the entropy, or disorder, of a closed system must always increase. Because a black hole’s entropy is proportional to its surface area, both must always increase.
Now a recent theory proposed by researchers from the Massachusetts Institute of Technology has validated this theorem of Hawking. According to LiveScience, the team of researchers led by astrophysicist Maximiliano used the data of gravitational waves released because of two small black holes merging into one to reach their conclusion. These gravitational waves were observed using the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) and divided into segments: before and after the merger.
The team then used this before and after measurement to calculate the surface area of the black holes in each segment. The calculations showed that the total surface area of the combined blackhole was greater than the sum of the two smaller blackholes. This observation upholds the area law that states that the size of black holes does not decrease over time.
“A black hole’s surface area can’t be decreased, which is like the second law of thermodynamics. It also has conservation of mass, as you can’t reduce its mass, so that’s analogous to the conservation of energy,” said lead author Maximiliano.
A black hole is formed from the death of a star with such a high gravitational field that the matter gets squeezed into the small space under it, trapping the light of the dead star. The first such merger of a black hole was detected in 2017 using the LIGO detectors that recorded gravitational signals via the merger of two relatively smaller black holes that started about a billion light-years from the Earth.
A black hole’s surface area is set out by a spherical boundary known as the event horizon — beyond this point nothing, not even light, can escape its powerful gravitational pull. According to Hawking’s interpretation of general relativity, as a black hole’s surface area increases with its mass, and because no object thrown inside can exit, its surface area cannot decrease. But a black hole’s surface area also shrinks the more it spins, so researchers wondered whether it would be possible to throw an object inside hard enough to make the black hole spin enough to decrease its area.
