It’s a conundrum that the late Stephen Hawking left us with as part of his groundbreaking work on these giant things, which has prompted experts to ponder potential solutions for more than half a century.
There’s a little but substantial defect somewhere between the two finest theories ever built in physics. Finding a solution would allow us to either understand general relativity as a particle-like system or appreciate quantum physics in the context of time and space. If not, a mix of the two.
A recent attempt at a novel theory by physicists from the United Kingdom, the United States, and Italy has piqued public curiosity, albeit it will be some time before we know for sure if it is the solution we seek.
Mathematically, it’s a brilliant new twist on an old idea – that black holes are kind of ‘hairy.’
To comprehend why a hairy black hole could be useful in terms of paradoxes, it’s first necessary to understand why there is a contradiction in the first place.
Black holes are densely packed clumps of matter whose gravity distorts space and time to the point where nothing can escape at the appropriate speed.
Normally, this would not be a big deal. Hawking, though, realised approximately half a century ago that black holes must shine’ in a special way. The wave-like character of surrounding quantum fields was changed by their bending of the Universe, resulting in a sort of heat radiation.
To make the math work, black holes would gradually emit energy, decrease at an increasing rate, and eventually vanish.
The information that falls into a radiating object like a star is normally represented by the jumbled rainbow of colours that erupt from its surface. After it dies, it is left in its chilly, dense husk.
In the case of black holes, however, this is not the case. If Hawking’s radiation theory is right, everything would simply vanish. This violates quantum physics’ big rule, which states that the information that defines a particle is conserved in the Universe from instant to moment.
The extent to which the properties and behaviour of the contents of a black hole’s information bank continue to affect their surroundings even after they’ve fallen over the edge is a major point of contention in the dispute over the nature of the black hole’s information bank.
In general relativity, there exist solutions for black holes that realise that their mass, angular momentum, and charge nonetheless push and pull on their immediate surroundings. Hair is used to characterise any residual ties with the Universe, and theories that assume their permanence are known as ‘yes-hair theorems.’
Black holes with a little fuzz would have a method to keep their quantum information stuck in the Universe, even if they fade away over time.
As a result, theorists have been hard at work attempting to reconcile the laws that instruct space and time how to curve with the laws that teach particles how to exchange their information.
In the form of theoretical particles known as gravitons, this new solution brings quantum thinking to gravity. These aren’t real particles like electrons or quarks, because no one has ever seen one in person. It’s possible they don’t exist at all.
That doesn’t rule out the possibility of imagining what they might look like if they did, or considering the quantum states in which they may operate.
The team demonstrates a reasonable model for how information inside a black hole can remain connected with surrounding space across its line-of-no-return – as slight perturbances of the black hole’s gravitational field – by following a series of logical steps from how gravitons could potentially behave under certain energy conditions (the hairs).
It’s an intriguing notion that’s built on a solid foundation. But there’s still a long way to go before we can call this puzzle “solved.”
In general, research advances in one of two ways. One is to notice something unusual and try to explain it. The second option is to make a wild guess and then try to find it.
Having a map which is theoretical like this is extremely helpful in our quest to solve one of physics’ most puzzling puzzles.
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