Stephen Hawking Lecture - How to Escape Out of a Black Hole
Δημοσιεύτηκε στις 30 Νοε 2015
Professor
Stephen Hawking gave this very interesting and fun lecture at the
University of Southern California College of Letters, Arts and Sciences
in which he gives us a brief history of black holes and a way in which
we might be theoretically able to travel through them.
“If you
feel you are in a black hole, don’t give up,” says Professor Hawking.
Black holes are the remains of stars that have collapsed under their own
gravity, producing gravitational forces so strong that even light can’t
escape. Anything that falls inside is thought to be ripped apart by the
massive gravity, never to been seen or heard from again.
What
you may not know is that physicists have been arguing for 40 years about
what happens to the information about the physical state of those
objects once they fall in. Quantum mechanics says that this information
cannot be destroyed, but general relativity says it must be – that’s why
this argument is known as the information paradox.
Now Hawking
says this information never makes it inside the black hole in the first
place. “I propose that the information is stored not in the interior of
the black hole as one might expect, but on its boundary, the event
horizon,”
The event horizon is the sphere around a black hole
from inside which nothing can escape its clutches. Hawking is suggesting
that the information about particles passing through is translated into
a kind of hologram – a 2D description of a 3D object – that sits on the
surface of the event horizon. “The idea is the super translations are a
hologram of the ingoing particles,” he said. “Thus they contain all the
information that would otherwise be lost.”
In the 1970s Hawking
introduced the concept of Hawking radiation – photons emitted by black
holes due to quantum fluctuations. Originally he said that this
radiation carried no information from inside the black hole, but in 2004
changed his mind and said it could be possible for information to get
out.
Just how that works is still a mystery, but Hawking now
thinks he’s cracked it. His new theory is that Hawking radiation can
pick up some of the information stored on the event horizon as it is
emitted, providing a way for it to get out. But don’t expect to get a
message from within, he said. “The information about incoming particles
is returned, but in a chaotic and useless form. This resolves the
information paradox. For all practical purposes, the information is
lost.”
Last year Hawking made headlines for saying “there are no
black holes” – although what he actually meant was a little more
complicated, as he proposed replacing the event horizon with a related
concept, an apparent horizon.
“The message of this lecture is
that black holes ain’t as black as they are painted. They are not the
eternal prisons they were once thought,” Hawking said. “Things can get
out of a black hole both on the outside and possibly come out in another
universe.”
Stephen Hawking gave this very interesting and fun lecture at the
University of Southern California College of Letters, Arts and Sciences
in which he gives us a brief history of black holes and a way in which
we might be theoretically able to travel through them.
“If you
feel you are in a black hole, don’t give up,” says Professor Hawking.
Black holes are the remains of stars that have collapsed under their own
gravity, producing gravitational forces so strong that even light can’t
escape. Anything that falls inside is thought to be ripped apart by the
massive gravity, never to been seen or heard from again.
What
you may not know is that physicists have been arguing for 40 years about
what happens to the information about the physical state of those
objects once they fall in. Quantum mechanics says that this information
cannot be destroyed, but general relativity says it must be – that’s why
this argument is known as the information paradox.
Now Hawking
says this information never makes it inside the black hole in the first
place. “I propose that the information is stored not in the interior of
the black hole as one might expect, but on its boundary, the event
horizon,”
The event horizon is the sphere around a black hole
from inside which nothing can escape its clutches. Hawking is suggesting
that the information about particles passing through is translated into
a kind of hologram – a 2D description of a 3D object – that sits on the
surface of the event horizon. “The idea is the super translations are a
hologram of the ingoing particles,” he said. “Thus they contain all the
information that would otherwise be lost.”
In the 1970s Hawking
introduced the concept of Hawking radiation – photons emitted by black
holes due to quantum fluctuations. Originally he said that this
radiation carried no information from inside the black hole, but in 2004
changed his mind and said it could be possible for information to get
out.
Just how that works is still a mystery, but Hawking now
thinks he’s cracked it. His new theory is that Hawking radiation can
pick up some of the information stored on the event horizon as it is
emitted, providing a way for it to get out. But don’t expect to get a
message from within, he said. “The information about incoming particles
is returned, but in a chaotic and useless form. This resolves the
information paradox. For all practical purposes, the information is
lost.”
Last year Hawking made headlines for saying “there are no
black holes” – although what he actually meant was a little more
complicated, as he proposed replacing the event horizon with a related
concept, an apparent horizon.
“The message of this lecture is
that black holes ain’t as black as they are painted. They are not the
eternal prisons they were once thought,” Hawking said. “Things can get
out of a black hole both on the outside and possibly come out in another
universe.”
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