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The New York Times Book Review
August 24, 2008
The Theory That Ate the World
By GEORGE JOHNSON
http://tinyurl.com/6zhyfl
THE BLACK HOLE WAR
My Battle With Stephen Hawking to Make the World Safe for Quantum Mechanics
By Leonard Susskind
470 pp. Little, Brown & Company. $27.99
This is your universe on acid: 10 dimensions of space, seven of which we
cannot see, filled almost entirely with dark matter and dark energy —
invisible thought stuff that serves to make the cosmologists’ equations come
out right.
The cosmologists are stuck, with the rest of us, in Dimensions 1 through 3,
and we are all made from what Earthlings quaintly regard as ordinary
particles, the tiny fraction of matter that radiates and reflects mysterious
waves called light. Compounding the indignity, this afterthought of an
existence may be only an illusion — a holographic projection of some
two-dimensional flatland that stretches like a timpani skin across the very
edge of space. Plato had it backward. It’s the shadows on the wall that are
real.
At night when our brains are unplugged from our senses and error-correction
is off, we dream furiously. And so it is with 21st-century physics.
Undeterred by experimental data — it would take a particle accelerator as
big as the galaxy to test some of the latest cosmological contrivances —
theorists have found a new role as entertainers, scientific Scheherazades.
Leonard Susskind, a professor of theoretical physics at Stanford, is one of
the wiliest. Three years ago in “The Cosmic Landscape: String Theory and the
Illusion of Intelligent Design,” he spun a tale of a multitude of different
universes — nooks and crannies of a transcendent multiverse, or “landscape,
” each ruled by a different physics. This is probably the most controversial
interpretation of superstring theory (some of Susskind’s colleagues
absolutely hate the idea), but it has its appeal. With so many universes out
there, the fact of our own existence need not inspire worship and awe. We
just happen to occupy one of the niches where the laws are favorable to
carbon-based life.
In his new book, “The Black Hole War: My Battle With Stephen Hawking to
Make the World Safe for Quantum Mechanics,” Susskind’s cosmos gets even
weirder. Black holes already seemed scary enough, with their ability to
swallow everything, including light. For a while, we learn, physicists were
faced with the possibility that these cosmic vortexes might also be eaters of
order, sucking up and destroying information. Like the Echthroi, the evil
demons of entropy in Madeleine L’Engle’s novel “A Wind in the Door,”
black holes might be chomping their way through the universe, ploughing sense
into nonsense.
The story of how Susskind and a colleague, the Dutch physicist Gerard ’t
Hooft, disproved (or at least undermined) the theory begins in 1983 at a San
Francisco mansion owned by, of all people, Werner Erhard, the New Age
entrepreneur who had made his fortune with a profitable cult called EST.
Erhard, we’re told, was also a “physics groupie,” and he presided over
salons in which some of the world’s great theorists came to butt minds.
The trouble began when Stephen Hawking made an astonishing prediction about
what happens when information — a book, a painting, a musical recording or
any pattern of matter or energy — falls into a black hole. Earlier, Hawking
had proved that black holes eventually evaporate — at which point, he now
claimed, everything inside them disappears from the universe.
That might not sound like such a big deal. Just find another copy of
whatever was lost. But that, Susskind realized, was not the point. Among the
fundamentals of physics is that information must always be conserved. Even if
you throw a DVD into a wood chipper, it is possible in theory (important
weasel words) to chase down the splinters and recover the songs. Burned books
can be reassembled from the smoke and ashes. Physics, in other words,
dictates that everything that happens must be reversible. And that means
information cannot be allowed simply to vanish.
Even worse, quantum mechanics predicts that empty space seethes with tiny “
virtual black holes,” popping in and out of existence and gobbling up bits.
If Hawking was right, Susskind concluded, “the foundations of our subject
were destroyed.”
Not everyone was quite so alarmed. But Hawking’s information paradox, as it
came to be called, opened an arena in which two great theories of physics —
general relativity, describing gravity, and quantum mechanics, describing
everything else — duked it out.
I was eager to learn how, in the end, Susskind and company showed that
Hawking was probably wrong — that information is indeed conserved. But first
I had to get through a 66-page crash course on relativity and quantum
mechanics. Every book about contemporary physics seems to begin this way,
which can be frustrating to anyone who reads more than one. (Imagine if every
account of the 2008 presidential campaign had to begin with the roots of
Athenian democracy and the heritage of the French Enlightenment.)
Finally we get to the heart of the story, and it turns out to be a
mind-bender. To make sense of Hawking’s paradox one must consider how much
information, measured in bits, the 1s and 0s of binary code, can fit inside a
black hole. The amount, it turns out, does not depend on the black hole’s
volume, as one might expect, but on the area of its “horizon” — the flat,
funnel-like mouth of the cosmic rabbit hole.
Susskind explains this dizzying notion about as clearly as is probably
possible. Every time a bit falls into a black hole, its opening expands by
one square Planck length — an area billions and billions of times smaller
than a proton. It is because of this phenomenon, Susskind contends, that the
information isn’t lost. A description of everything that falls into a black
hole, whether a book or an entire civilization, is recorded on the surface of
its horizon and radiated back like imagery on a giant drive-in movie screen.
As with a hologram, three dimensions are contained within two.
Strangest of all, we learn, this holographic conjecture — elevated in the
book, perhaps prematurely, to the holographic principle — may apply to the
entire universe. Hence the notion of our own reality as an illusory
projection of some flatlanders’ membrane world. It’s as though the
pixilated people we see on television are real and the actors are only
secondary manifestations.
Or something like that. How this all fits together is still pretty murky. “
Getting our collective head around the holographic principle is probably the
biggest challenge that we physicists have had since the discovery of quantum
mechanics,” Susskind admits. He speculates at one point that our big bang of
a universe is some kind of “inside-out black hole” — one that spews
everything outward instead of sucking it in.
But wait. Maybe it just looks that way because time is moving backward! Or —
who knows? — maybe our universe is really a 3-D projection of a 4-D world
falling through some hyperdimensional gullet!
Toward the end of the book Susskind quotes Hawking: “We are just an
advanced breed of monkeys on a minor planet of a very average star. But we
can understand the universe.”
Maybe. But not without a lot more data.
George Johnson is the author of “Fire in the Mind: Science, Faith, and the
Search for Order.” His most recent book is “The Ten Most Beautiful
Experiments.”
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