In his first book ever, the father of string theory reinvents
the world''s concept of the known universe and man''s unique place
within it. Line drawings.
目錄：
Ch. 1 The world according to Feynman
Ch. 2 The mother of all physics problems
Ch. 3 The lay of the land
Ch. 4 The myth of uniqueness and elegance
Ch. 5 Thunderbolt from heaven
Ch. 6 On frozen fish and boiled fish
Ch. 7 A rubber band-powered
內容試閱：
The Cosmic Landscape
ry cold and still: except for the sound of my own breathing, the
silence is absolute. The dry, powdery snow crackles whenever my
boot touches down. Its perfect whiteness, lit by starlight, gives
the terrain a luminous, eerie brilliance, while the stars fade into
a continuous glow across the black celestial dome. The night is
brighter on this desolate planet than on my own home world. Beauty,
but of a cold and lifeless kind: a place for metaphysical
contemplation if ever there was one. Alone, I''d left the safety of
the base, to think about the day''s events and to watch the sky for
meteors. But it was impossible to think of anything other than the
sheer enormousness and impersonal nature of the universe. The
pinwheeling of galaxies, the endless expansion of the universe, the
infinite coldness of space, the heat of stars being born, and their
final death throes as red giants: surely this must be the point of
existence.
Man-life in general-seems irrelevant to the workings of the
universe: a mere smudge of water, grease, and carbon on a pinpoint
planet circling a star of no special consequence.
Earlier, during the short stingy sunlight hours, Curt, Kip, and I
had hiked about a mile to the Russian compound to see if we could
find some Ivans to talk to. Stephen had wanted to come with us but
his wheelchair could not navigate the snowdrifts. The derelict
compound, just a few low rusted corrugated-metal buildings, looked
deserted. We banged on the doors, but no life appeared. I cracked
open the door and peered into the spooky interior darkness, then
decided to brave entry and have a look around. As cold inside as it
was outside, the compound was completely abandoned. The hundred or
so dormitory rooms were unlocked but deserted. How did a hundred
men disappear so completely? In silence we hiked back to our own
base.
At the bar, we found our Russian, drinking and laughing-Victor.
Victor, it seems, was one of the last three Russians left on the
planet. Supplies from Russia had ceased more than a year ago. They
would have starved but for the fact that our own people adopted
them. We never saw the other two Russians, but Victor assured us
they were alive. Victor insisted on buying me a drink, "for the
cold," and asked, "How do you like this %#*^ place?" I told
him in all my travels only once had I seen the night sky even
remotely as beautiful as here. Ironically, that other alien planet
was so hot that the rocks would fry anything that touched
them.
Of course we were not really on another planet. It only seemed
that way. Antarctica is truly alien. Stephen Hawking, Curt Callan,
Kip Thorne, Stan Deser, Claudio Teitelboim, myself, our wives, and
a few other theoretical physicists were there for fun-as a lark-a
reward for coming to Chile for a conference on black holes.
Claudio, an eminent Chilean physicist, had arranged for the Chilean
Air Force to fly us in one of its giant Hercules cargo planes to
their Antarctic base for a couple of days.
It was August 1997-winter in the southern hemisphere-and we were
expecting the worst. The coldest I had ever experienced was 20
below zero Fahrenheit, and I was worried about how well I would
handle the 60 below that can grip the base in midwinter. When the
plane landed, we anxiously zipped up the heavy Arctic gear that the
military had provided and prepared for the fearful cold.
Then the cargo hold opened, and Curt''s wife, Chantal, bounded out
of the plane, threw up her arms, and joyously yelled back, "It''s
about as cold as a winter day in New Jersey." And so it was. It
stayed that way for the whole day while we frolicked in the
snow.
Sometime during that night the beast awoke. By morning Antarctica
had unleashed its fury. I went outside for a couple of minutes to
get a taste of what Shackleton and his shipwrecked men had endured.
Why hadn''t they all perished? Not a single member of the expedition
was lost. Freezing cold and soaking wet for more than a year, why
didn''t they all die of pneumonia? Out there in the blast of the
storm, I knew the answer: nothing survives-not even the microbes
that give men colds.
The other alien "planet" I''d mentioned to Victor was Death
Valley- another lifeless place. No, not quite lifeless. But I
wondered how much hotter it would have to get to fry all
protoplasm. What Antarctica has in common with Death Valley is
extreme dryness. It''s too cold for much water vapor to be suspended
in the air-that and the complete lack of light pollution make it
possible, in both extremes, to see the stars in a way that modern
man rarely can. Standing there in the Antarctic starlight, it
occurred to me how lucky we humans are. Life is fragile: it thrives
only in a narrow range of temperatures between freezing and
boiling. How lucky that our planet is just the right distance from
the sun: a little farther, and the death of the perpetual Antarctic
winter-or worse-would prevail; a little closer, and the surface
would truly fry anything that touched it. Victor, being Russian,
took a spiritual view of the question. "Was it not," he asked,
"God''s infinite kindness and love that permitted our existence?" My
own "mindless" explanation will become clear in good time.
In fact we have much more to be thankful for than just the
earth''s temperature. Without the right amount of carbon, oxygen,
nitrogen, and other elements, a temperate climate would be wasted.
If the sun at the center of our solar system were replaced by the
more common binary star system, planetary orbits would be too
chaotic and unstable for life to have evolved. There are endless
dangers of this kind. But on top of all these are the laws of
nature themselves. All it takes is a small change in Newton''s laws,
or the rules of atomic physics, and poof-life would either be
instantly extinguished or would never have formed. It seems that
our guardian angel not only provided us with a very benign planet
to live on but also made the rules of existence-the laws of physics
and cosmology-just right for us. This is one of the greatest
mysteries of nature. Is it luck? Is it intelligent and benevolent
design? Is it at all a topic for science-for metaphysics-for
religion?
This book is about a debate that is stirring the passions of
physicists and cosmologists but is also part of a broader
controversy, especially in the United States, where it has entered
the partisan political discourse. On one side are the people who
are convinced that the world must have been created or designed by
an intelligent agent with a benevolent purpose. On the other side
are the hard-nosed, scientific types who feel certain that the
universe is the product of impersonal, disinterested laws of
physics, mathematics, and probability-a world without a purpose, so
to speak. By the first group, I don''t mean the biblical literalists
who believe the world was created six thousand years ago and are
ready to fight about it. I am talking about thoughtful, intelligent
people who look around at the world and have a hard time believing
that it was just dumb luck that made the world so accommodating to
human beings. I don''t think these people are being stupid; they
have a real point.
The advocates of intelligent design generally argue that it is
incredible that anything as complex as the human visual system
could have evolved by purely random processes. It is incredible!
But biologists are armed with a very powerful tool-the Principle of
Natural Selection- whose explanatory power is so great that almost
all biologists believe the weight of evidence is strongly in favor
of Darwin. The miracle of the eye is only an apparent
miracle.
I think the design enthusiasts are on better ground when it comes
to physics and cosmology. Biology is only part of the story of
creation. The Laws of Physics and the origin of the universe are
the other part, and here again, incredible miracles appear to
abound. It seems hopelessly improbable that any particular rules
accidentally led to the miracle of intelligent life. Nevertheless,
this is exactly what most physicists have believed: intelligent
life is a purely serendipitous consequence of physical principles
that have nothing to do with our own existence. Here I share the
skepticism of the intelligent-design crowd: I think that the dumb
luck needs an explanation. But the explanation that is emerging
from modern physics is every bit as different from intelligent
design as Darwin''s was from "Soapy" Sam Wilberforce''s.
The debate that this book is concerned with is not the bitter
political controversy between science and creationism. Unlike the
debate between "Darwin''s Bulldog" Thomas Huxley and Wilberforce,
the present argument is not between religion and science but
between two warring factions of science-those who believe, on the
one hand, that the laws of nature are determined by mathematical
relations, which by mere chance happen to allow life, and those who
believe that the Laws of Physics have, in some way, been determined
by the requirement that intelligent life be possible. The
bitterness and rancor of the controversy have crystallized around a
single phrase-the Anthropic Principle-a hypothetical principle that
says that the world is fine-tuned so that we can be here to observe
it! By itself I would have to say that this is a silly, half-baked
notion. It makes no more sense than saying that the reason the eye
evolved is so that someone can exist to read this book. But it is
really shorthand for a much richer set of concepts that I will make
clear in the chapters that follow.
But the controversy among scientists does have repercussions for
the broader public debate. Not surprisingly, it does overflow the
seminar rooms and scientific journals into the political debates
about design and creationism. Christian Internet sites have leapt
into the fray:
The Bible says: "From the time the world was created, people have
seen the earth and the sky and all that God made. They can clearly
see His invisible qualities-His eternal power and divine nature. So
they have no excuse whatsoever for not knowing God."
This is as true today as it ever has been-in some ways, with the
discovery of the Anthropic Principle, it is more true now than ever
before. So the first kind of evidence that we have is the creation
itself-a universe that carries God''s signature-a universe "just
right" for us to live in.
And from another religious site:
In his book "The Cosmic Blueprint," the astronomer professor Paul
Davies concludes that the evidence for design is overwhelming:
Professor Sir Fred Hoyle-no sympathizer with Christianity-says that
it looks as if a super-intellect has monkeyed with physics as well
as with chemistry and biology.
And the astronomer George Greenstein says: As we survey all the
evidence, the thought insistently arises that some supernatural
agency, or rather Agency, must be involved. Is it possible that
suddenly, without intending to, we have stumbled upon scientific
proof of the existence of a supreme being? Was it God who stepped
in and so providentially created the cosmos for our benefit?
Is it any wonder that the Anthropic Principle makes many
physicists very uncomfortable?
Davies and Greenstein are serious scholars, and Hoyle was one of
the great scientists of the twentieth century. As they point out,
the appearance of intelligent design is undeniable. Extraordinary
coincidences are required for life to be possible. It will take us
a few chapters to fully understand this "elephant in the room," but
let''s begin with a sneak preview. The world as we know it is very
precarious, in a sense that is of special interest to physicists.
There are many ways it could go bad-so bad that life as we know it
would be totally impossible. The requirements that the world be
similar enough to our own to support conventional life fall into
three broad classes. The first class involves the raw materials of
life: chemicals. Life is, of course, a chemical process. Something
about the way atoms are constructed makes them stick together in
the most bizarre combinations: the giant crazy Tinkertoy molecules
of life-DNA, RNA, hundreds of proteins, and all the rest. Chemistry
is really a branch of physics: the physics of the valence
electrons, i.e., those that orbit the nucleus at the outer edges of
the atom. It''s the valence electrons hopping back and forth or
being shared between atoms that gives the atoms their amazing
abilities.
The Laws of Physics begin with a list of elementary particles
like electrons, quarks, and photons, each with special properties
such as mass and electric charge. These are the objects that
everything else is built out of. No one knows why the list is what
it is or why the properties of these particles are exactly what
they are. An infinite number of other lists is equally possible.
But a universe filled with life is by no means a generic
expectation. Eliminating any of these particles electrons, quarks,
or photons, or even changing their properties a modest amount,
would cause conventional chemistry to collapse. This is obviously
so for the electrons and for the quarks that make up protons and
neutrons. Without these there could be no atoms at all. But the
importance of the photon may be less obvious. In later chapters we
will learn about the origin of forces like electric and
gravitational forces, but for now it''s enough to know that the
electric forces that hold the atom together are consequences of the
photon and its special properties. If the laws of nature seem well
chosen for chemistry, they are also well chosen for the second set
of requirements, namely, that the evolution of the universe
provided us with a comfortable home to live in. The largescale
properties of the universe-its size; how fast it grows; the
existence of galaxies, stars, and planets-are mainly governed by
the force of gravity. It''s Einstein''s theory of gravity-the General
Theory of Relativity- that explains how the universe expanded from
the initial hot Big Bang to its present large size. The properties
of gravity, especially its strength, could easily have been
different. In fact it is an unexplained miracle that gravity is as
weak as it is. The gravitational force between electrons and the
atomic nucleus is ten thousand billion billion billion billion
times weaker than the electrical attraction. Were the gravitational
forces even a little stronger, the universe would have evolved so
quickly that there would have been no time for intelligent life to
arise. But gravity plays a very dramatic role in the unfolding of
the universe. Its pull causes the material in the
universe-hydrogen, helium, and the so-called dark matter-to clump,
into galaxies, stars, and finally planets. However, for this to
happen, the very early universe must have been a bit lumpy. If the
original material of the universe had been smoothly distributed, it
would have stayed that way for all time. In fact, fourteen billion
years ago, the universe was just lumpy enough-a bit lumpier or a
bit less lumpy, and there would have been no galaxies, stars, or
planets for life to evolve on.
Finally, there is the actual chemical composition of the
universe. In the beginning there were only hydrogen and helium:
certainly not sufficient for the formation of life. Carbon, oxygen,
and all the others came later. They were formed in the nuclear
reactors in the interiors of stars. But the ability of stars to
transmute hydrogen and helium into the all-important carbon nuclei
was a very delicate affair. Small changes in the laws of
electricity and nuclear physics could have prevented the formation
of carbon.
Even if the carbon, oxygen, and other biologically important
elements were formed inside stars, they had to get out in order to
provide the material for planets and life. Obviously we cannot live
in the intensely hot cores of stars. How did the material escape
the stellar interior? The answer is that it was violently ejected
in cataclysmic supernova explosions. Supernova explosions
themselves are remarkable phenomena. In addition to protons,
neutrons, electrons, photons, and gravity, supernovae require yet
another particle-the ghostly neutrino previously mentioned. The
neutrinos, as they escape from the collapsing star, create a
pressure that pushes the elements in front of them. And,
fortunately, the list of elementary particles happens to include
neutrinos with the right properties.
Continues...
Excerpted from The Cosmic Landscape by Leonard Susskind
Copyright ? 2006 by Leonard Susskind . Excerpted by
permission.
All rights reserved. No part of this excerpt may be reproduced or
reprinted without permission in writing from the publisher.
Excerpts are provided by Dial-A-Book Inc. solely for the personal
use of visitors to this web site.
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