Hyperspace

HYPERSPACE

A Scientific Odyssey
Through
Parallel Universes,
Time Warps, and
The Tenth Dimension

Michio Kaku

Illustrations by Robert O’Keefe

Oxford University Press

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©
1994 by Oxford University Press, Inc.

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Library of Congress Cataloging-in-Publication Data
Kaku, Michio.
Hyperspace : a scientific odyssey through parallel universes,
time warps, and the tenth dimension /
Michio Kaku.
p. cm.
Includes bibliographical references and index.
ISBN 0-19-508514-0
1. Kaluza-Klein theories. 2. Superstring theories.
3. Hyperspace. I. Title.
QC793.3.F5K35 1994 530.1’42—dc20 93-7910

“Cosmic Gall.” From
Telephone Poles and Other Poems
by John Updike.
Copyright © 1960 by John Updike.
Reprinted by permission of Alfred A. Knopf, Inc.
Originally appeared in
The New Yorker
.

Excerpt from “Fire and Ice.” From
The Poetry of Robert Frost
,
edited by Edward Connery Lathem.
Copyright 1951 by Robert Frost.
Copyright 1923, © 1969 by Henry Holt and Company, Inc.
Reprinted by permission of Henry Holt and
Company, Inc.

2 4 6 8 9 7 5 3 1

Printed in the United States of America
on acid-free paper

This book is dedicated
to my parents

Scientific revolutions, almost by definition, defy common sense.

If all our common-sense notions about the universe were correct, then science would have solved the secrets of the universe thousands of years ago. The purpose of science is to peel back the layer of the appearance of objects to reveal their underlying nature. In fact, if appearance and essence were the same thing, there would be no need for science.

Perhaps the most deeply entrenched common-sense notion about our world is that it is three dimensional. It goes without saying that length, width, and breadth suffice to describe all objects in our visible universe. Experiments with babies and animals have shown that we are born with an innate sense that our world is three dimensional. If we include time as another dimension, then four dimensions are sufficient to record all events in the universe. No matter where our instruments have probed, from deep within the atom to the farthest reaches of the galactic cluster, we have only found evidence of these four dimensions. To claim otherwise publicly, that other dimensions might exist or that our universe may coexist with others, is to invite certain scorn. Yet this deeply ingrained prejudice about our world, first speculated on by ancient Greek philosophers 2 millennia ago, is about to succumb to the progress of science.

This book is about a scientific revolution created by the
theory of hyperspace
,
¹
which states that dimensions exist beyond the commonly accepted four of space and time. There is a growing acknowledgment among physicists worldwide, including several Nobel laureates, that the universe may actually exist in higher-dimensional space. If this theory is proved correct, it will create a profound conceptual and philosophical revolution in our understanding of the universe. Scientifically, the hyperspace theory goes by the names of Kaluza-Klein theory and supergravity. But
its most advanced formulation is called superstring theory, which even predicts the precise number of dimensions: ten. The usual three dimensions of space (length, width, and breadth) and one of time are now extended by six more spatial dimensions.

We caution that the theory of hyperspace has not yet been experimentally confirmed and would, in fact, be exceedingly difficult to prove in the laboratory. However, the theory has already swept across the major physics research laboratories of the world and has irrevocably altered the scientific landscape of modern physics, generating a staggering number of research papers in the scientific literature (over 5,000 by one count). However, almost nothing has been written for the lay audience to explain the fascinating properties of higher-dimensional space. Therefore, the general public is only dimly aware, if at all, of this revolution. In fact, the glib references to other dimensions and parallel universes in the popular culture are often misleading. This is regrettable because the theory’s importance lies in its power to unify all known physical phenomena in an astonishingly simple framework. This book makes available, for the first time, a scientifically authoritative but accessible account of the current fascinating research on hyperspace.

To explain why the hyperspace theory has generated so much excitement within the world of theoretical physics, I have developed four fundamental themes that run through this book like a thread. These four themes divide the book into four parts.

In
Part I
, I develop the early history of hyperspace, emphasizing the theme that the laws of nature become simpler and more elegant when expressed in higher dimensions.

To understand how adding higher dimensions can simplify physical problems, consider the following example: To the ancient Egyptians, the weather was a complete mystery. What caused the seasons? Why did it get warmer as they traveled south? Why did the winds generally blow in one direction? The weather was impossible to explain from the limited vantage point of the ancient Egyptians, to whom the earth appeared flat, like a two-dimensional plane. But now imagine sending the Egyptians in a rocket into outer space, where they can see the earth as simple and whole in its orbit around the sun. Suddenly, the answers to these questions become obvious.

From outer space, it is clear that the earth’s axis is tilted about 23 degrees from the vertical (the ‘vertical” being the perpendicular to the plane of the earth’s orbit around the sun). Because of this tilt, the northern hemisphere receives much less sunlight during one part of its orbit than during another part. Hence we have winter and summer. And since
the equator receives more sunlight then the northern or southern polar regions, it becomes warmer as we approach the equator. Similarly, since the earth spins counterclockwise to someone sitting on the north pole, the cold, polar air swerves as it moves south toward the equator. The motion of hot and cold masses of air, set in motion by the earth’s spin, thus helps to explain why the winds generally blow in one direction, depending on where you are on the earth.

In summary, the rather obscure laws of the weather are easy to understand once we view the earth from space. Thus the solution to the problem is to go
up
into space, into the
third dimension
. Facts that were impossible to understand in a flat world suddenly become obvious when viewing a three-dimensional earth.

Similarly, the laws of gravity and light seem totally dissimilar. They obey different physical assumptions and different mathematics. Attempts to splice these two forces have always failed. However, if we add one more dimension, a
fifth
dimension, to the previous four dimensions of space and time, then the equations governing light and gravity appear to merge together like two pieces of a jigsaw puzzle. Light, in fact, can be explained as vibrations in the fifth dimension. In this way, we see that the laws of light and gravity become simpler in five dimensions.

Consequently, many physicists are now convinced that a conventional four-dimensional theory is “too small” to describe adequately the forces that describe our universe. In a four-dimensional theory, physicists have to squeeze together the forces of nature in a clumsy, unnatural fashion. Furthermore, this hybrid theory is incorrect. When expressed in dimensions beyond four, however, we have “enough room” to explain the fundamental forces in an elegant, self-contained fashion.

In
Part II
, we further elaborate on this simple idea, emphasizing that the hyperspace theory may be able to unify all known laws of nature into one theory. Thus the hyperspace theory may be the crowning achievement of 2 millennia of scientific investigation: the unification of all known physical forces. It may give us the Holy Grail of physics, the “theory of everything” that eluded Einstein for so many decades.

For the past half-century, scientists have been puzzled as to why the basic forces that hold together the cosmos—gravity, electromagnetism, and the strong and weak nuclear forces—differ so greatly. Attempts by the greatest minds of the twentieth century to provide a unifying picture of all the known forces have failed. However, the hyperspace theory allows the possibility of explaining the four forces of nature as well as the seemingly random collection of subatomic particles in a truly elegant
fashion. In the hyperspace theory, “matter” can be also viewed as the vibrations that ripple through the fabric of space and time. Thus follows the fascinating possibility that everything we see around us, from the trees and mountains to the stars themselves, are nothing but
vibrations in hyperspace
. If this is true, then this gives us an elegant, simple, and geometric means of providing a coherent and compelling description of the entire universe.

In
Part III
, we explore the possibility that, under extreme circumstances, space may be stretched until it rips or tears. In other words, hyperspace may provide a means to tunnel through space and time. Although we stress that this is still highly speculative, physicists are seriously analyzing the properties of “wormholes,” of tunnels that link distant parts of space and time. Physicists at the California Institute of Technology, for example, have seriously proposed the possibility of building a time machine, consisting of a wormhole that connects the past with the future. Time machines have now left the realm of speculation and fantasy and have become legitimate fields of scientific research.

Cosmologists have even proposed the startling possibility that our universe is just one among an infinite number of parallel universes. These universes might be compared to a vast collection of soap bubbles suspended in air. Normally, contact between these bubble universes is impossible, but, by analyzing Einstein’s equations, cosmologists have shown that there might exist a web of wormholes, or tubes, that connect these parallel universes. On each bubble, we can define our own distinctive space and time, which have meaning only on its surface; outside these bubbles, space and time have no meaning.

Although many consequences of this discussion are purely theoretical, hyperspace travel may eventually provide the most practical application of all: to save intelligent life, including ours, from the death of the universe. Scientists universally believe that the universe must eventually die, and with it all life that has evolved over billions of years. For example, according to the prevailing theory, called the Big Bang, a cosmic explosion 15 to 20 billion years ago set the universe expanding, hurling stars and galaxies away from us at great velocities. However, if the universe one day stops expanding and begins to contract, it will eventually collapse into a fiery cataclysm called the Big Crunch, in which all intelligent life will be vaporized by fantastic heat. Nevertheless, some physicists have speculated that the hyperspace theory may provide the one and only hope of a refuge for intelligent life. In the last seconds of the death of our universe, intelligent life may escape the collapse by fleeing into hyperspace.

In
Part IV
, we conclude with a final, practical question: If the theory is proved correct, then when will we be able to harness the power of the hyperspace theory? This is not just an academic question, because in the past, the harnessing of just one of the four fundamental forces irrevocably changed the course of human history, lifting us from the ignorance and squalor of ancient, preindustrial societies to modern civilization. In some sense, even the vast sweep of human history can be viewed in a new light, in terms of the progressive mastery of each of the four forces. The history of civilization has undergone a profound change as each of these forces was discovered and mastered.

For example, when Isaac Newton wrote down the classical laws of gravity, he developed the theory of mechanics, which gave us the laws governing machines. This, in turn, greatly accelerated the Industrial Revolution, which unleashed political forces that eventually overthrew the feudal dynasties of Europe. In the mid-1860s, when James Clerk Maxwell wrote down the fundamental laws of the electromagnetic force, he ushered in the Electric Age, which gave us the dynamo, radio, television, radar, household appliances, the telephone, microwaves, consumer electronics, the electronic computer, lasers, and many other electronic marvels. Without the understanding and utilization of the electromagnetic force, civilization would have stagnated, frozen in a time before the discovery of the light bulb and the electric motor. In the mid-1940s, when the nuclear force was harnessed, the world was again turned upside down with the development of the atomic and hydrogen bombs, the most destructive weapons on the planet. Because we are not on the verge of a unified understanding of all the cosmic forces governing the universe, one might expect that any civilization that masters the hyperspace theory will become lord of the universe.