The Cosmic Landscape
By Leonard Susskind
Little, Brown
Copyright © 2006
Leonard Susskind
All right reserved.
ISBN: 0-316-15579-9
Introduction
The air is very 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.
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