Trying to solidify hypotheses regarding intangible phenomenon or objects way beyond human reach is a physicist’s toughest job. Albert Einstein, who is a Godly figure in the world of physics, is the closest one has been to understanding the universe. But, it turns, even he might have been wrong about with his theories on black holes. Einstein had noted that black holes have three characteristics -- mass, spin and charge -- making all black holes identical. But according to a new research, there might be a fourth and rather unexpected feature, hair.
Before you start picturing black holes with luscious waves of hair, it is slightly different. "In classical general relativity, they would be exactly identical," Paul Chesler, theoretical physicist noted. It is called as no-hair theorem, a rather cruel analogy to say two black holes, like two bald heads, are indistinguishable. But in 2012, Stefanos Aretakis, a mathematician suggested the presence of instabilities on event horizons of black hole — making them the 'hair' that differentiates the two heads. The instability regions would present themselves by a difference in gravity, he’d suggested. But his mathematical work could not prove such things to exist in reality.
However,according to a new study, there might be a way to detect this hair. Gaurav Khanna, co-author of the paper, says that Aretakis merely suggested there might be some evidence but they have found a way to quantify this.
The paper suggests gravitational instabilities on or near the event horizon of a near-extremal black hole can be created by disturbances like matter that falls into it. After all, black holes are famous for absorbing all matter around them. "We would expect that the gravitational signal we would see would be quite different from ordinary black holes that are not extreme," says Khanna.
This hair, if present, would retain information about the black hole's past.
The no hair theorem violation could lead to resolving paradoxes between general relativity and quantum mechanics. The paper, if proven right, might find a way to not quantify black hole observation but merge it with our knowledge of fundamental physics. This may have further implications in understanding string theory and other major confusing aspects of the universe.
But, there are roadblocks in this path. Primarily, there’s no certainty there are near-extreme black holes. Even if they do, we don’t know if our gravitational wave detectors are sensitive enough to detect "these instabilities from the hair." The last hurdle is the hair itself; if it exists, it would be very short-lived, as short as fraction of a second.
"We would love to know if nature would even allow for such a beast to exist," Khanna noted as it would have very dramatic implications in the world of physics.