What Goes In The Black Hole
Stays In The Black Hole. OK?
Reviewed by James Trefil
Washington Post, September 7, 2008
Edited by Andy Ross
The Black Hole War
My Battle with Stephen Hawking to Make the World Safe for Quantum Mechanics
By Leonard Susskind
Little, Brown. 470 pages
If you must learn about black holes, you could do a lot worse
than to pick up this engagingly written book. Stanford physicist Leonard
Susskind provides a marvelous introduction to the subject that is both readable
and easy to understand. Or at least as easy as something involving the two great
20th-century advances in science can be.
The 20th century brought two revolutions. The first, which dealt with objects
moving near the speed of light or having very large mass, was relativity, the
brainchild of Albert Einstein. The second revolution came when people starting
thinking about very small objects, such as the stuff inside the atom. The
resulting theory is called quantum mechanics and was developed by a small group
of young scientists, the most familiar probably being Werner Heisenberg.
With increasing urgency over the past 50 years, theoretical physicists have
tried to tie these two great 20th-century advances together. So far, we have not
been successful. And this is where Susskind's "war" comes in, because it looked
as if there could well be a fundamental contradiction between the two theories.
At least that's what Stephen Hawking argued.
Remember that a black hole is an object so compact and so massive that nothing,
not even light, can escape from it. Stuff can fall in, but nothing can come out.
The black hole forms a kind of nexus where both relativity and quantum mechanics
come into play.
In 1983, Hawking proved that black holes are not eternal. In fact, over
unimaginably long spans of time, they evaporate. And that's when the "war"
started, because if a black hole evaporates (and everyone agrees that it will),
what happens to all the information that was carried by the stuff that fell in?
Hawking argued that this information was lost forever.
The problem is that one of the basic laws of quantum mechanics is that
information cannot be lost. Hawking argued that with the material that
evaporated from the black hole, the information simply disappeared.
In the end, Susskind and his colleagues were able to resolve this dilemma and,
in the words of the subtitle, "make the world safe for quantum mechanics." I
won't spoil the book for you by telegraphing the ending. Suffice it to say that
it involves a tour through the whole arcane menagerie of modern physics.
James Trefil is Clarence J. Robinson Professor of Physics at George Mason
University.
Stephen Hawking
Chapter One
The First Shot
San Francisco, 1983
The ... initial skirmish took place in the attic of Jack Rosenberg's San Francisco
mansion. Jack, also known as
Werner Erhard, was a guru, a supersalesman, and a
bit of a con man. Prior to the early 1970s, he had been just plain Jack
Rosenberg, encyclopedia salesman. Then one day, while crossing the Golden Gate
Bridge, he had an epiphany. He would save the world and, while he was at it,
make a huge fortune. All he needed was a classier name and a new pitch. ...
I liked Werner. He was smart, interesting, and fun. And he was fascinated by
physics. He wanted to be part of it, so he spent wads of money bringing groups
of elite theoretical physicists to his mansion. ...
The year was 1983. The guests included, among other notables, Murray Gell-Mann,
Sheldon Glashow, Frank Wilczek, Savas Dimopoulos, and Dave Finkelstein. But for
this story, the most important participants were the three main combatants in
the Black Hole War: Gerard t'Hooft, Stephen Hawking, and myself.
Although I had met Gerard only a few times before 1983, he had made a big
impression on me. ...
But it wasn't Gerard whom I most remember from Werner's attic. It was Stephen
Hawking, whom I first met there. It's where Stephen dropped the bomb that set
the Black Hole War in motion. ...
Stephen claimed that "information is lost in black hole evaporation," and,
worse, he seemed to prove it. If that was true, Gerard and I realized, the
foundations of our subject were destroyed. ...
On the blackboard was a Penrose diagram, a type of diagram representing a black
hole. The horizon (the edge of the black hole) was drawn as a dashed line, and
the singularity at the center of the black hole was an ominous-looking jagged
line. Lines pointing inward through the horizon represented bits of information
falling past the horizon into the singularity. There were no lines coming back
out. According to Stephen, those bits were irretrievably lost. To make matters
worse, Stephen had proved that black holes eventually evaporate and disappear,
leaving no trace of what has fallen in. ...
What's so bad about losing a bit of information inside a black hole? Then it
dawned on us. Losing information is the same as generating entropy. And
generating entropy means generating heat. The virtual black holes that Stephen
had so blithely postulated would create heat in empty space. Together with
another colleague, Michael Peskin, we made an estimate based on Stephen's
theory. We found that if Stephen was right, empty space would heat up to a
thousand billion billion billion degrees in a tiny fraction of a second. ...
AR Reading this book
sounds like a pretty dumb way to try to catch up with some deep physics.
As for
Werner Erhard, I became acquainted with his works in London in 1985. A girlfriend
had just "done" The Forum and liked it so much she persuaded me to do it too.
It was quite a pleasant experience and I did not feel conned at all.
