When and how did the universe begin? Why are we here? What is
the nature of reality? Is the apparent “grand design” of our
universe evidence of a benevolent creator who set things in
motion—or does science offer another explanation? In this startling
and lavishly illustrated book, Stephen Hawking and Leonard Mlodinow
present the most recent scientific thinking about these and other
abiding mysteries of the universe, in nontechnical language marked
by brilliance and simplicity.
According to quantum theory, the cosmos does not have just a
single existence or history. The authors explain that we ourselves
are the product of quantum fluctuations in the early universe, and
show how quantum theory predicts the “multiverse”—the idea that
ours is just one of many universes that appeared spontaneously out
of nothing, each with different laws of nature. They conclude with
a riveting assessment of M-theory, an explanation of the laws
governing our universe that is currently the only viable candidate
for a “theory of everything”: the unified theory that Einstein was
looking for, which, if confirmed, would represent the ultimate
triumph of human reason.
關於作者：
Stephen Hawking was the Lucasian Professor of Mathematics at
the University of Cambridge for thirty years, and has been the
recipient of numerous awards and honors including, most recently,
the Presidential Medal of Freedom. His books for the general reader
include the classic A Brief History of Time, Black Holes and Baby
Universes and Other Essays, The Universe in a Nutshell, and A
Briefer History of Time. He lives in Cambridge, England.
Leonard Mlodinow received his doctorate in theoretical physics
from the University of California at Berkeley, and teaches at
Caltech. He is the New York Times bestselling author of The
Drunkard’s Walk: How Randomness Rules our Lives, Subliminal: How
Your Unconscious Mind Rules Your Behavior, War of the Worldviews:
Science versus Spirituality with Deepak Chopra, Feynman’s
Rainbow: A Search for Beauty in Physics and in Life, and Euclid’s
Window: The Story of Geometry from Parallel Lines to Hyperspace. He
also wrote for Star Trek: The Next Generation. He lives in South
Pasadena, California.
目錄：
1 The Mystery of Being
2 The Rule of Law
3 What Is Reality?
4 Alternative Histories
5 The Theory of Everything
6 Choosing Our Universe
7The Apparent Miracle
8 Thc Grand Design
Glossary
Acknowledgments
Index
內容試閱：
Chapter 1
We each exist for but a short time, and in that time explore but
a small part of the whole universe. But humans are a curious
species. We wonder, we seek answers. Living in this vast world that
is by turns kind and cruel, and gazing at the immense heavens
above, people have always asked a multitude of questions: How can
we understand the world in which we find ourselves? How does the
universe behave? What is the nature of reality? Where did all this
come from? Did the universe need a creator? Most of us do not spend
most of our time worrying about these questions, but almost all of
us worry about them some of the time.
Traditionally these are questions for philosophy, but philosophy
is dead. Philosophy has not kept up with modern developments in
science, particularly physics. Scientists have become the bearers
of the torch of discovery in our quest for knowledge. The purpose
of this book is to give the answers that are suggested by recent
discoveries and theoretical advances. They lead us to a new picture
of the universe and our place in it that is very different from the
traditional one, and different even from the picture we might have
painted just a decade or two ago. Still, the first sketches of the
new concept can be traced back almost a century.
According to the traditional conception of the universe, objects
move on well-defined paths and have definite histories. We can
specify their precise position at each moment in time. Although
that account is successful enough for everyday purposes, it was
found in the 1920s that this "classical" picture could not account
for the seemingly bizarre behavior observed on the atomic and
subatomic scales of existence. Instead it was necessary to adopt a
different framework, called quantum physics. Quantum theories have
turned out to be remarkably accurate at predicting events on those
scales, while also reproducing the predictions of the old classical
theories when applied to the macroscopic world of daily life. But
quantum and classical physics are based on very different
conceptions of physical reality.
Quantum theories can be formulated in many different ways, but
what is probably the most intuitive description was given by
Richard Dick Feynman, a colorful character who worked at the
California Institute of Technology and played the bongo drums at a
strip joint down the road. According to Feynman, a system has not
just one history but every possible history. As we seek our
answers, we will explain Feynman''s approach in detail, and employ
it to explore the idea that the universe itself has no single
history, nor even an independent existence. That seems like a
radical idea, even to many physicists. Indeed, like many notions in
today''s science, it appears to violate common sense. But common
sense is based upon everyday experience, not upon the universe as
it is revealed through the marvels of technologies such as those
that allow us to gaze deep into the atom or back to the early
universe.
Until the advent of modern physics it was generally thought that
all knowledge of the world could be obtained through direct
observation, that things are what they seem, as perceived through
our senses. But the spectacular success of modern physics, which is
based upon concepts such as Feynman''s that clash with everyday
experience, has shown that that is not the case. The naive view of
reality therefore is not compatible with modern physics. To deal
with such paradoxes we shall adopt an approach that we call
model-dependent realism. It is based on the idea that our brains
interpret the input from our sensory organs by making a model of
the world. When such a model is successful at explaining events, we
tend to attribute to it, and to the elements and concepts that
constitute it, the quality of reality or absolute truth. But there
may be different ways in which one could model the same physical
situation, with each employing different fundamental elements and
concepts. If two such physical theories or models accurately
predict the same events, one cannot be said to be more real than
the other; rather, we are free to use whichever model is most
convenient.
In the history of science we have discovered a sequence of better
and better theories or models, from Plato to the classical theory
of Newton to modern quantum theories. It is natural to ask: Will
this sequence eventually reach an end point, an ultimate theory of
the universe, that will include all forces and predict every
observation we can make, or will we continue forever finding better
theories, but never one that cannot be improved upon? We do not yet
have a definitive answer to this question, but we now have a
candidate for the ultimate theory of everything, if indeed one
exists, called M- theory. M-theory is the only model that has all
the properties we think the final theory ought to have, and it is
the theory upon which much of our later discussion is based.
M-theory is not a theory in the usual sense. It is a whole family
of different theories, each of which is a good description of
observations only in some range of physical situations. It is a bit
like a map. As is well known, one cannot show the whole of the
earth''s surface on a single map. The usual Mercator projection used
for maps of the world makes areas appear larger and larger in the
far north and south and doesn''t cover the North and South Poles. To
faithfully map the entire earth, one has to use a collection
of
maps, each of which covers a limited region. The maps overlap
each other, and where they do, they show the same landscape.
M-theory is similar. The different theories in the M-theory
family may look very different, but they can all be regarded as
aspects of the same underlying theory. They are versions of the
theory that are applicable only in limited ranges-for example, when
certain quantities such as energy are small. Like the overlapping
maps in a Mercator projection, where the ranges of different
versions overlap, they predict the same phenomena. But just as
there is no flat map that is a good representation of the earth''s
entire surface, there is no single theory that is a good
representation of observations in all situations.
We will describe how M-theory may offer answers to the question
of creation. According to M-theory, ours is not the only universe.
Instead, M-theory predicts that a great many universes were created
out of nothing. Their creation does not require the intervention of
some supernatural being or god. Rather, these multiple universes
arise naturally from physical law. They are a prediction of
science. Each universe has many possible histories and many
possible states at later times, that is, at times like the present,
long after their creation. Most of these states will be quite
unlike the universe we observe and quite unsuitable for the
existence of any form of life. Only a very few would allow
creatures like us to exist. Thus our presence selects out from this
vast array only those universes that are compatible with our
existence. Although we are puny and insignificant on the scale of
the cosmos, this makes us in a sense the lords of creation.
To understand the universe at the deepest level, we need to know
not only how the universe behaves, but why.
Why is there something rather than nothing?
Why do we exist?
Why this particular set of laws and not some other?
This is the Ultimate Question of Life, the Universe, and
Everything. We shall attempt to answer it in this book. Unlike the
answer given in The Hitchhiker''s Guide to the Galaxy, ours won''t be
simply "42."
2
The Rule of Law
Skoll the wolf who shall scare the Moon
Till he flies to the Wood-of-Woe:
Hati the wolf, Hridvitnir''s kin,
Who shall pursue the sun.
-"Grimnismal," The Elder Edda
n Viking mythology, Skoll and Hati chase the sun and the moon.
When the wolves catch either one, there is an eclipse. When this
happens, the people on earth rush to rescue the sun or moon by
making as much noise as they can in hopes of scaring off the
wolves. There are similar myths in other cultures. But after a time
people must have noticed that the sun and moon soon emerged from
the eclipse regardless of whether they ran around screaming and
banging on things. After a time they must also have noticed that
the eclipses didn''t just happen at random: They occurred in regular
patterns that repeated themselves. These patterns were most obvious
for eclipses of the moon and enabled the ancient Babylonians to
predict lunar eclipses fairly accurately even though they didn''t
realize that they were caused by the earth blocking the light of
the sun. Eclipses of the sun were more difficult to predict because
they are visible only in a corridor on the earth about 30 miles
wide. Still, once grasped, the patterns made it clear the eclipses
were not dependent on the arbitrary whims of supernatural beings,
but rather governed by laws.
Despite some early success predicting the motion of celestial
bodies, most events in nature appeared to our ancestors to be
impossible to predict. Volcanoes, earthquakes, storms, pestilences,
and ingrown toenails all seemed to occur without obvious cause or
pattern. In ancient times it was natural to ascribe the violent
acts of nature to a pantheon of mischievous or malevolent deities.
Calamities were often taken as a sign that we had somehow offended
the gods. For example, in about 4800 bc the Mount Mazama volcano in
Oregon erupted, raining rock and burning ash for years, and leading
to the many years of rainfall that eventually filled the volcanic
crater today called Crater Lake. The Klamath Indians of Oregon have
a legend that faithfully matches every geologic detail of the event
but adds a bit of drama by portraying a human as the cause of the
catastrophe. The human capacity for guilt is such that people can
always find ways to blame themselves. As the legend goes, Llao, the
chief of the Below World, falls in love with the beautiful human
daughter of a Klamath chief. She spurns him, and in revenge Llao
tries to destroy the Klamath w...
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