Researchers may have solved Professor Stephen Hawking's famous black hole paradox—a mystery that has puzzled scientists for almost half a century.
According
to two new studies, something called "quantum hair" is the answer to
the problem.
In
the first paper, published in the journal Physical Review Letters, researchers
demonstrated that black holes are more complex than originally thought and have
gravitational fields that hold information about how they were formed.
The
researchers showed that matter collapsing into a black hole leaves a mark in
its gravitational field—an imprint referred to as a "quantum hair."
In a
follow-up paper, published in a separate journal, Physics Letters B, Professor
Xavier Calmet from the University of Sussex's School of Mathematical and
Physical Sciences and Professor Stephen Hsu from Michigan State University said
quantum hairs resolve Hawking's Black Hole Information Paradox.
In
1976, Hawking suggested that, as black holes evaporate, they destroy information
about what had formed them.
That
idea goes against a fundamental law of quantum mechanics which states any
process in physics can be mathematically reversed.
In
the 1960s, physicist John Archibald Wheeler, discussing black holes' lack of
observable features beyond their total mass, spin, and charge, coined the
phrase "black holes have no hair"—known as the no-hair theorem.
However,
the newly discovered "quantum hair" provides a way for information to
be preserved as a black hole collapses and, as such, resolves one of modern
science's most famous quandaries, experts say.
Prof
Calmet said: "Black holes have long been considered the perfect laboratory
to study how to merge Einstein's theory of general relativity with quantum
mechanics.
"It
was generally assumed within the scientific community that resolving this
paradox would require a huge paradigm shift in physics, forcing the potential
reformulation of either quantum mechanics or general relativity.
"What we found—and I think is particularly exciting—is that this isn't necessary."
Explaining
the discovery of the "quantum hair," Roberto Casadio, professor of
Theoretical Physics at the University of Bologna, said: "A crucial aspect
is that black holes are formed by the collapse of compact objects and then,
according to the quantum theory, there is no absolute separation between the
interior and the exterior of the black hole.
"In
the classical theory, the horizon acts as a perfect one-way membrane which does
not let anything out and the exterior is therefore the same for all black holes
of a given mass. This is the classical no-hair theorem," Casadio added.
"However,
in the quantum theory, the state of the matter that collapses and forms the
black hole continues to affect the state of the exterior, albeit in a way that
is compatible with present experimental bounds. This is what is known as
'quantum hair.'"
Reference(s): PhysicsLetters B, Physical Reviews Letter