Table Of ContentThe
Unfolding Universe
A Stellar J ourney
PREVIOUS BOOKS BY
LLOYD MOTZ AND JEFFERSON HANE WEA VER
THE CONCEPTS OF SCIENCE: From Newton to Einstein
THE STORY OF PHYSICS
The
Unfolding Universe
A Stellar Jo urney
Lloyd Motz
and
Jefferson Hane Weaver
Springer Science+Business Media, LLC
Library of Congress Cataloging in Publication Data
Motz, Lloyd, 1910-
The unfolding universe: a stellar journey / Lloyd Motz and Jefferson Hane Weaver.
p. cm.
Includes bibliographical references and index.
ISBN 0-306-43264-1
1. Astronomy. I. Weaver, Jefferson Hane. 11. Title.
QB43.2.M674 1989 89-8782
520-dc20 CIP
ISBN 978-0-306-43264-4 ISBN 978-1-4899-5982-9 (eBook)
DOI 10.1007/978-1-4899-5982-9
© 1989 Lloyd Motz and Jefferson Hane Weaver
Origina1ly published by Plenum US in 1989.
Softcover reprint of the hardcover I st edition 1989
All rights reserved
No part of this book may be reproduced, stored in a retrieval system, or transmitted
in any form or by any means, electronic, mechanical, photocopying, microfilming,
recording, or otherwise, without written permission from the Publisher
To Minne and Shelley
Preface
There is hardly an area in our lives that has not been influenced by
or does not owe something to astronomy. It has been the friend of
the sailor exploring uncharted seas, the inspiration of the poet and
artist, the source of mythology and astrology, the great arena in
which theology was born and evolved, and the intellectual domain
of the philosopher, to name but a few human activities that astron
omy has enriched. The greatest chronicler of them all , William
Shakespeare, conveyed his belief in the importance of astronomy
to romance and music in The Merchant of Venice, where he had
Lorenzo exhort Jessica to contemplate the heavens while the
"sounds of music" crept in their ears and the "soft stillness and
night" be.came "the touches of sweet harmony."
Astronomy is the queen of the sciences because it bore so me
of our most important scientific principles; so now more than ever
the stars, and the uni verse itself, are the ultimate laboratories where
the high-energy particle physicists seek answers to some ofthe most
perplexing problems about the nature of space and time and the
origin ofthe universe. Indeed, astronomy has enabled us to grapple
with some of the so-called "ultimate questions" about the nature
of existence that scientists used to leave to philosophers and me
taphysicists. We now have astronomical evidence that the universe
originally began with a gigantic explosion that scattered the pri
mordial ingredients of the cosmos thoughout space.
In this book we have tried to communicate so me of our feeling
that the study of astronomy is a great adventure that, more than
any other intellectual pursuit, reveals the relationship of all things
vii
viii PREFACE
to each other and the present to the past and the future. This sen
timent was perhaps most beautifully expressed by the poet William
Blake, who saw the "world in a grain of sand, heaven in a wild
flower and infinity in an hour." While it is doubtful that Blake knew
much about astronomy or had even an inkling that all things might
consist of fundamental building blocks that we now call atoms, his
poem does suggest his sense that all things are related to each other
in some subtle yet pervasive manner. Similarly, Albert Einstein 's
lifelong search for a unified field theory that would somehow explain
all known physical phenomena in the uni verse was motivated by
his belief that the uni verse is ultimately homogeneous on the sub
atomic level.
Recent exciting discoveries in astronomy, such as quasars, pul
sars (neutron stars), X-ray sources, background cosmic radiation,
black holes, interstellar organic molecules, and the origin and ev
olution of the universe, to name the most spectacular ones, have
had an important although not always desirable effect on the ex
position of astronomy and the writing of astronomy books. The
emphasis both in popular articles and in recent books on astronomy
has shifted to such an extent from classical astronomy to the current
dramatic discoveries that the general reader may be left with a feel
ing of discontinuity and a sense that astronomy consists of aseries
of amazing but unrelated tableaux. It is very difficult, if not im
possible, for the person not trained in science to see, without proper
guidance, how the various astronomical phenomena now being stud
ied so assiduously are related to each other and to the great body
of astronomical knowledge and principles that has been built up
over the ages. This book supplies that guidance in a simple, non
mathematical way so that the reader can see just how the modern
great developments in astronomy have emerged from classical as
tronomy and how they are related to each other and to the two great
theories of physics-the theory of relativity and the quantum the
ory-that lead us in our exploration of the universe.
The first eight chapters of this book deal with the major bodies
in the solar system and their dynamics. We present the properties
of Earth, the moon, the planets and their satellites, the asteroids,
the comets, and the sun in a purely descriptive way that any in
quisitive reader can understand and absorb as easily as any well
written description of the geographical and topographical features
of Earth. Since the dynamics of the solar system are determined
PREFACE ix
essentially by the gravitational force of the sun on the other bodies
in the solar system, we introduce Newton's law of gravity and his
laws of motion in a simple, direct way with a minimal use of ele
mentary algebra. We discuss the way the orbits of the planets and
the motion of the planets (Kepler's laws of planetary motion) are
related to Newton's law of gravity. Since a complete understanding
of the motions of the planets requires some knowledge of the theory
of relativity, the special and the general theories of relativity are
described in Chapters 4 and 5.
In Chapters 9 through 13 we examine the general properties of
the stars and describe correlations among these properties, such as
the Hertzsprung-Russell diagram. Since one must know something
about the characteristics of radiation and the structure of the atom
to understand how the astronomer obtains his results, we introduce
and explain the principles ofthermodynamics, the laws ofradiation,
and atomic theory as they are needed. Chapters 14, 15, and 16 are
devoted to the structure and evolution (from birth to death) of stars,
and the conditions that determine wh ether a star will end its Iife as
a white dwarf, a neutron star, or a black hole. The three remaining
chapters concern the motions of stars, the structure of our galaxy
(the Milky Way), the properties of galaxies in general, and the struc
ture and evolution of the universe (cosmology).
We have tried to write an accessible exposition of the great
astronomical and astrophysical principles, presented in their sim
plest form so as to appeal to the general reader who comes to as
tronomy because it is the only science that offers an insight into
our relationship to the universe. By showing that astronomy has
both observational and theoretical features, we demonstrate that
this subject presents so me ofthe most spectacular images ever imag
ined as weil as some of the most profound physical principles our
intellects have yet uncovered.
L10yd Motz
Jefferson Hane Weaver
Contents
Chapter 1. The Earth 1
Chapter 2. The Moon 15
Chapter 3. The Planets and Their Motions 25
Chapter 4. The Special Theory of Relativity 65
Chapter 5. The General Theory of Relativity 85
Chapter 6. The Properties of the Planets 99
Chapter 7. Comets, Meteors, and Interplanetary Dust 123
Chapter 8. The Sun 129
Chapter 9. The Stars: Their Distances, Luminosities,
and Colors 139
Chapter 10. Deat, Radiation, and the Temperatures
of Stars 147
Chapter 11. Spectral Classes of Stars 175
Chapter 12. Atomic Structure and Stellar Spectra 193
Chapter 13. Stellar Masses and Radii 223
Chapter 14. The Deep Interiors of Stars 233
Chapter 15. The Structure and Evolution of Stars 249
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