Table Of Contentn o t h i n g n e s s
the science of empty space
henning genz
h
• g
n o t n n e s s
1
•
THE SCIENCE
OF EMPTY SPACE
•
HENNING GENZ
Translated by Karin Heusch
BASIC
B
BOOKS
A Member of the Perseus Books Group
New York •
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English translation copyright© 1999 by Perseus Books Publishing, L.L.C.
Copyright 1998 © by Perseus Books Publishing
Originally published in German as Die Entdeckung des Nichts© 1994 Carl Hanser
Verlag MOchen Wien
All rights reserved. No part of this publication may be reproduced, stored in a
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ISBN-I0: 0-7382-0610-5 ISBN-13: 978-0-7382-06]0-3
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CONTENTS
•
PREFACE
Things, Just Things vii
Acknowledgments xi
PROLOGUE 1
Physics and Metaphysics
2 NOTHING, NOBODY, NOWHERE, NEVER 33
Philosophical, Linguistic, and Religious Ideas on Nothingness
3 PROBLEMS WITH NOTHINGNESS 97
How to Make It a Physical Reality
4 MATTER IN THE VOID 145
Ether, Space, Fields
5 CROWDED SPACE 179
Movement All Around-the Quantum Vacuum
6 SPONTANEOUS CREATION 209
Particles and Fields
7 LET NATURE BE AS SHE MA Y 227
Special Systems
8 NOTHING IS REAL 257
The Universe as a Whole
9 EPILOGUE 305
Physics and Metaphysics
Notes 317
Figure Sources 325
Bibliography 327
Index 337
PREFACE
•
THINGS, JUST THINGS
•
THIS BOOK IS DEDICATED TO THE QUESTION "CAN THERE BE SPACE
independent of things?" Space that is immutable, like a stage that remains the
same no matter what is being played on it? Space that may be empty and for all
time remain empty? Such a space would be a "void" proper, or what we call
"nothingness"--concepts that in antiquity were found by natural philosophers
to be so controversial as to be unthinkable. Over the millennia, this void has
evolved into what physicists call the vacuum-their term for empty space. Physics
fills this vacuum with the progeny of quantum mechanics, of the general theory
of relativity, of whatever the Big Bang left for us. This question then poses itself:
How empty can space be and still remain in consonance with the laws of nature?
In the seventeenth century, Galileo's disciple Evangelista Torricelli was the
first to succeed in the removal of everything material from an otherwise empty
container. This experimental success made it harder for skeptics to insist that
there couldn't be such a thing as empty space-a skepticism maintained by the
followers of Aristotle, who dung to the tradition of the horror vacui, nature's
supposed abhorrence of a vacuum. It was Isaac Newton who considered the
meaning of space in the laws of nature; he also discussed the concept of the
ether-not the substance used to anesthetize but some mysterious matter that
was assumed to fill the universe. Newton found that these concepts helped him
describe (if not understand) the motion of a planetary system through the long
distance action of gravity across empty space.
From the seventeenth century on, science has made tremendous progress
based on the notion that there are just two fundamentals: matter and empty
space. In the back of their minds, the natural philosophers-who slowly evolved
into natural scientists in the modern sense-had long nurtured the concept of
the mysterious ether, a substance that could not be chopped up into atoms but
instead was strictly continuous.
It took Albert Einstein to do away with this idea. The details are complicated,
VII
viii NOT H I N G N E S S
and we will discuss them. Today, we know that the laws of nature do not permit
space that is absolutely empty. At high temperatures, space at its emptiest will
be filled with thermal radiation. At low temperatures, structures will form in
the void. According to quantum mechanics-more specifically, to Heisenberg's
uncertainty relation-we can never precisely fix the amount of energy that fills
a certain region of space in a certain amount of time. The amount of energy will
fluctuate. Consequently, we will never be able to define a zero-scale for energy.
One might say that the vacuum of physics emits energy-more of it the shorter
the time span we define, less of it for longer times.
According to Albert Einstein's famous formula E = mc2, energy and mass
are the same thing. Mass therefore also fluctuates, and empty space will see a
constant emergence and disappearance of particles that carry this mass. These
particles don't last, and physicists call them virtual particles.
The physical vacuum is by no means empty and devoid of characteristics.
Rather, anything that can exist at all will oscillate and spin in it in a random,
disordered fashion. In this vacuum, quantities will emerge that, in an abstract
space of particle properties, will define directions; these quantities, which in their
abstract space act somewhat like magnets in real space, are called fields. Although
these fields influence the way in which we perceive the physical world on all
levels, the discipline of physics needs to examine minuscule regions in order to
confront them directly. It might appear paradoxical-but the huge accelerating
machines of elementary particle physics not only examine the particles they
accelerate but also explore the emptiest of spaces we can imagine, and thereby
some of the questions that the Greek natural philosophers bequeathed to us as
problems still to be solved. But it is not only with huge accelerators that we
investigate the void-we can perform less spectacular but enormously precise
and complex experiments based on nothing but light.
Most of this book is devoted to what we know about the void. There is,
however, another question intimately related to this void, a question that has
fascinated humankind across the millennia, that has spawned myths and legends
of creation: How did it happen that at some point in time, something appeared
out of nothing? To this day, physics cannot give a definite answer to this question.
The standard models advanced by cosmologists and elementary particle physicists
permit them to reconstruct the history of the universe back to fractions of a
second after the Big Bang. So much is for certain. But the closer we get to the
Big Bang, the less certain our knowledge. We can only speculate about the Big
Bang itself, and what happened immediately after it. This is the subject of the
last two chapters of this book. Which ideas about creation do the laws of nature
admit? These laws always and everywhere have been the same. This is a central
tenet of physics: It is just the state of our world that has changed over time.
The main purpose of this book is the transmittal of scientific insight. Only
such insight can foster the reali7.ation that nature is. in fact, understandable to
PRE FA C E (X
humankind. I stand convinced that this is the most noble aim of basic scientific
research. By this I do not mean to assert that the world in all its complexity will
one day be completely understood. That, to be sure, will not happen. Rather,
the implication is that natural phenomena are not the work of spooks and demons
but are due to rationally explorable causes. This is the attitude that launched
Western cultural and scientific thinking six centuries before Christ. We owe it
to the so-called pre-Socratic philosophers in Ionic Greece, who, as Erwin Schrod
inger, recipient of the 1933 Nobel Prize in physics, has put it, "saw the world as
a rather complicated mechanism, acting according to eternal innate laws, which
they were curious to find out. This is, of course, the fundamental attitude of
science up to this day."
My physics colleagues who browse through this book may be amazed at the
long passages I devote to the ancient naturalists. I do this for two reasons: first,
there is my curiosity, which goes hack to my own school days; second, there is
my conviction that those ideas from antiquity do not differ much from what
determines many of our contemporaries' notions of the natural sciences. It is
therefore appropriate that we take them as a starting point for the communication
of today's scientific insight. It should be possible to start from the views of the
ancient Greek naturalists and move to those of modern science. This is what I
have tried to accomplish here.
In the process, I have had to ask myself how far I can pursue this path
without losing contact with the notions actually developed by those ancient
naturalists. Take the ideas of Anaxagoras as an example: I started with his divisibil
ity of ur-matter and interpreted it in terms of modern ideas on the formation of
structures of matter. In doing so, I did not dare to go as far as taking what he
calls the seeds of, say, hair, which are hairs themselves, to be an early form of
self-replicating fractals.
In my original manuscript, I limited myself to the interpretation of those
ideas from antiquity that were directly related to the topics I am covering. Other
ancient notions I merely renamed in modern terms. This was not enough for
Eginhard Hora, my meticulous editor at Hanser Publishing: He insisted on the
insertion of minireviews on many physics subtopics, from A (as in antimatter)
to Z (as in zero-point energy).
The philosophical and historical passages are based on an unsystematic pe
rusal of the available literature. The term nothingness invariably evokes mythical
psychological connotations. The reader will not find these connotations here,
nor will terms such as nirvana, black-out, immersion, the nothing that acts out of
nothingness be found here. I hope I have managed to write this book in such a
way that these connotations cannot even be read into my text.
But I cannot be sure. The great English astrophysicist Sir Arthur S. Eddington
wrote in the preface to his popular science book New Pathways in Science,
published in 1935: co A hook of this nature has to evoke precise thinking hy means
x NOTHINGNESS
of imprecise turns of language." Therefore, the author may not always succeed
in "evoking in the reader's mind the very ideas he is trying to convey. He certainly
cannot do so unless the reader joins in an active effort." Eddington demands
that the author manage to "relegate secondary complications to the background."
Those complications will become obvious to anybody trying to describe the facts
in a straightforward fashion. But what do we mean by "secondary"? That may
well be a matter of opinion. Certainly, some scientists who have spent years
chasing down one of those complications will be unhappy to see it classed as
"secondary. "
Given such a book, how will it be read, and by whom? All authors naturally
hope to see their readership riveted on their books, breathlessly engaged from
start to finish, but such readers are rare. Most pick and choose, looking for what
elicits their interest, their happy concurrence, or their violent protest. I tried to
write the prologue and epilogue so that those readers who read nothing else will
still gain an overview of the substance of the entire book. The prologue and
epilogue should stand on their own as an intelligible and, I hope, captivating
synopsis of our subject.
ACKNOWLEDGMENTS
•
Part of this book is the result of a six-month stay at the TRIUMF Laboratories
in Vancouver, British Columbia, from 1991 to 1992. The author wishes to thank
his Canadian colleagues for their hospitality. He acknowledges the support of
the Volkswagen Foundation, which made that visit possible. He has greatly
profited from discussions with, and from the reactions of, friends and colleagues
who may have wondered about some of the topics that came up in the process.
This book has benefited considerably from the helpful comments of Eginhard
Hora, editor at Carl Hanser Editions, and Jeffrey Robbins of Helix Books. To all
of them, and to many whom I cannot name but who are well aware of their
contributions to this project, I feel deeply beholden.
XI
CHAPTER 1
PROLOGUE
•
PHYSICS AND METAPHYSICS
•
LET'S ASSUME WE CAN REMOVE ALL MATTER FROM SOME REGION OF
space. What will we be left witM A region of empty space? Not necessarily.
In the universe, between galaxies, each atom is at a distance of about one
meter from its next neighbor. Still, the space between those atoms is not empty;
it is bright with light and other radiation from very different sources. It is only
in the absolutely empty space of our imagination that no light, no radiation
penetrates-that space is as dark as the legendary rooms of Schild a, in the German
fairy tale. A region of space is not really empty simply by virtue of not containing
matter.
BLACKBODY RADIATION
If we wanted to produce a region of really empty space, we would have to remove
from it not only all matter but also all radiation. To keep it from exchanging
matter and radiation with the space around it, we would have to shield it
effectively-say, by surrounding it with walls. We might then take an ideal pump
to evacuate this enclosed space, hoping that the radiation it contained would
gradually be absorbed by the walls and that the final result would in fact be a
truly empty space.
Unfortunately, that is not how it works. First of all, walls not only absorb
radiation but also emit it. Every enclosed space is filled with the radiation absorbed
and emitted by its walls. That is why a space free of matter is not necessarily
empty space.
The radiation we are discussing here might be thermal radiation; at higher
temperature, it might be red light, like that emitted by an overheated electric
stove; and at still much higher temperature, it might be the light of the Sun.
This radiation weakens as the temperature of the emitting body decreases, but
we would have to go to what the physicists call absolute zero-that is, - 273
