The Black Hole War
My Battle with Stephen Hawking to Make the World Safe for Quantum Mechanics
By Leonard Susskind
Little, Brown
Copyright © 2008
Leonard Susskind
All right reserved.
ISBN: 978-0-316-01640-7
Chapter One
THE FIRST SHOT
San Francisco, 1983
The dark clouds of war had been gathering for more than eighty years by the time
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. His new
name would be Werner (for Werner Heisenberg) Erhard (for the German statesman
Ludwig Erhard); the new pitch would be Erhard Seminars Training, aka EST. And he
did succeed, if not in saving the world, at least in making his fortune.
Thousands of shy, insecure people paid several hundred dollars each to be
harangued, harassed, and (according to legend) told that they couldn't go to the
toilet during the sixteen-hour motivational seminars run by Werner or one of his
many disciples. It was a lot cheaper and faster than psychotherapy, and in a way
it was effective. Shy and uncertain going in, the attendees appeared confident,
strong, and friendly-just like Werner-coming out. Never mind that they sometimes
seemed like manic, hand-shaking robots. They felt better. "The training" was
even the subject of a very funny movie called
Semi-Tough with Burt Reynolds.
EST groupies surrounded Werner.
Slaves would definitely be too strong a term;
let's call them volunteers. There were EST-trained chefs to cook his food,
chauffeurs to drive him around town, and all manner of house servants to staff
his mansion. But ironically, Werner himself was a groupie-a physics groupie.
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. Sometimes just a few of his
special physics buddies-Sidney Coleman, David Finkelstein, Dick Feynman, and
I-would meet in his home for spectacular dinners catered by celebrity chefs. But
more to the point, Werner liked to host small, elite conferences. With a
well-equipped seminar room in the attic, a staff of volunteers to cater to our
every whim, and San Francisco as the venue, the mini-conferences were lots of
fun. Some physicists were suspicious of Werner. They thought he would use the
physics connection in some devious way to promote himself, but he never did. As
far as I can tell, he just liked hearing about the latest ideas from the
characters who were hatching them.
I think there were three or four EST conferences altogether, but only one left
an indelible imprint on me, and on my physics research. 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. Everyone knew that he was brilliant, but I sensed much more
than that. He seemed to have a steel core, an intellectual toughness that
exceeded that of anyone else I knew, with the possible exception of Dick
Feynman. Both of them were showmen. Dick was an American showman-brash,
irreverent, and full of macho one-upmanship. Once, among a group of young
physicists at Cal Tech, he described a joke that the graduate students had
played on him. There was a sandwich place in Pasadena where they served
"celebrity" sandwiches. You could get a Humphrey Bogart, a Marilyn Monroe, and
so on. The students had taken him to lunch there-I think for his birthday-and
one after another ordered the Feynman sandwich. They had conspired with the
manager beforehand, and the guy behind the counter didn't bat an eye.
After he finished the story, I said, "Gee, Dick, I wonder what the difference
would be between a Feynman sandwich and a Susskind sandwich."
"Oh, they'd be about the same," he replied, "except the Susskind sandwich would
have more ham."
"Yeah," I responded, "but a lot less baloney." That was probably the only time I
beat him at that game.
Gerard is a Dutchman. The Dutch are the tallest people in Europe, but Gerard is
short and solidly built, with a mustache and the look of a burgher. Like
Feynman, 't Hooft has a strong competitive streak, but I am sure that I never
got the better of him. Unlike Feynman, he is a product of old Europe-the last
great European physicist, inheritor of the mantle of Einstein and Bohr. Although
he is six years younger than I am, I was in awe of him in 1983, and rightfully
so. In 1999 he was awarded the Nobel Prize for his work leading to the Standard
Model of elementary particles.
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 is also a showman. He is a physically tiny man-I doubt that he weighs a
hundred pounds-but his small body contains a prodigious intellect and an equally
outsized ego. At that time, Stephen was in a more or less ordinary powered
wheelchair, and he could still talk using his own voice, though he was very hard
to understand unless you spent a lot of time with him. He traveled with an
entourage that included a nurse and a young colleague who would listen to him
very carefully and then repeat what he said.
In 1983 his translator was Martin Rocek, now a well-known physicist and one of
the pioneers in an important subject called Supergravity. At the time of the EST
conference, however, Martin was quite young and not so well known. Nevertheless,
from previous meetings I knew that he was a very capable theoretical physicist.
At some point in our conversation, Stephen (through Martin) said something that
I thought was wrong. I turned to Martin and asked him for clarification of the
physics. He looked at me like a deer caught in the headlights. Later he told me
what had happened. It seems that translating Stephen's speech required such
intense concentration that he was usually unable to keep track of the
conversation. He barely knew what we were talking about.
Stephen is an unusual sight. I am not talking about his wheelchair or the
obvious physical limitations of his body. Despite the immobility of his facial
muscles, his faint smile is unique, simultaneously angelic and devilish,
projecting a sense of secret amusement. During the EST conference, I found
talking to Stephen very difficult. It took a long time for him to answer, and
his answers were usually very brief. These short, sometimes single-word answers,
his smile, and his almost disembodied intellect were unnerving. It was like
communicating with the Oracle at Delphi. When someone submitted a question to
Stephen, the initial response was absolute silence, and the eventual output was
often incomprehensible. But the knowing smile said, "may not understand what
I'm saying, but I do, and I am right."
The world sees the diminutive Stephen as a mighty man, a hero of extraordinary
courage and fortitude. Those who know him see other sides: Stephen the Playful
and Stephen the Bold. One evening during the EST conference, a few of us were
out walking on one of San Francisco's famous brake-busting hills. Stephen was
with us, driving his powered chair. When we reached the steepest section, he
turned on the devilish smile. Without a moment's hesitation, he took off down
the hill at maximum velocity, the rest of us startled. We chased him, fearing
the worst. When we got to the bottom, we found him sitting and smiling. He
wanted to know whether there was a steeper hill to try. Stephen Hawking: the
Evel Knievel of physics.
Indeed, Hawking is very much a daredevil of a physicist. But perhaps his boldest
move ever was the bomb he dropped in Werner's attic.
I can't remember how his lecture worked at EST. Today a physics seminar given by
Stephen has him sitting quietly in his chair while a disembodied computer voice
lectures from a previous recording. That computerized voice has become Stephen's
trademark; as flat as it is, it is full of personality and humor. But back then,
maybe he talked and Martin translated. However it happened, the bomb fell with
full force on Gerard and me.
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. How did the rest of the people in
Werner's attic receive the news? Like the coyote in the roadrunner cartoon who
overruns the edge of the cliff: the ground had disappeared beneath their feet,
but they didn't know it yet.
It is said of cosmologists that they are often in error but never in doubt. If
so, Stephen is only half a cosmologist: never in doubt but hardly ever wrong. In
this case, he was. But Stephen's "mistake" was one of the most seminal in the
history of physics and could ultimately lead to a profound paradigm shift about
the nature of space, time, and matter.
Stephen's lecture was the last that day. For about an hour afterward, Gerard
stood glaring at the diagram on Werner's blackboard. Everyone else had left. I
can still see the intense frown on Gerard's face and the amused smile on
Stephen's. Almost nothing was said. It was an electric moment.
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.
Stephen's theory went even further. He postulated that the vacuum-empty
space-was full of "virtual" black holes that flashed into and out of existence
so rapidly that we didn't notice them. The effect of these virtual black holes,
he claimed, was to erase information, even if there was no "real" black hole in
the vicinity.
In chapter 7, you will learn exactly what "information" means and also what it
means to lose it. For now, just take it from me: this was an unmitigated
disaster. 'T Hooft and I knew it, but the response from everyone else who heard
about it that day was "Ho hum, information is lost in black holes." Stephen
himself was sanguine. For me the toughest part of dealing with Stephen has
always been the irritation I feel at his complacency. Information loss was
something that just could not be right, but Stephen couldn't see it.
The conference broke up, and we all went home. For Stephen and Gerard, that
meant back to Cambridge University and the University of Utrecht, respectively;
for me a forty-minute drive south on Route 101 back to Palo Alto and Stanford
University. It was hard to concentrate on the traffic. It was a cold day in
January, and every time I stopped or slowed down, I would draw the figure from
Werner's blackboard on my frosty windshield.
Back at Stanford, I told my friend Tom Banks about Stephen's claim. Tom and I
thought about it intensely. To try to learn some more, I even invited one of
Stephen's former students to come up from Southern California. We were very
suspicious of Stephen's claim, but for a while we weren't sure why. 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. Although I knew that Stephen was
wrong, I couldn't find the hole in his reasoning. Perhaps that was what
irritated me the most.
The ensuing Black Hole War was more than an argument between physicists. It was
also a war of ideas, or perhaps a war between fundamental principles. The
principles of Quantum Mechanics and those of General Relativity always seemed to
be fighting each other, and it was not clear that the two could coexist. Hawking
is a general relativist who had put his trust in Einstein's Equivalence
Principle. 'T Hooft and I are quantum physicists who felt certain that the laws
of Quantum Mechanics could not be violated without destroying the foundations of
physics. In the next three chapters, I will set the stage for the Black Hole War
by explaining the basics of black holes, General Relativity, and Quantum
Mechanics.
(Continues...)
Excerpted from The Black Hole War
by Leonard Susskind
Copyright © 2008 by Leonard Susskind.
Excerpted by permission.
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