From Atoms to Infinity. Readings in Modern Science

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FROM

ATOMS TO INFINITY

READINGS IN MODERN SCIENCE Edited by CLIFFORD D. SIMAK Drawings by viICTOR LAZZARO ~%

This is the first book in a series growing out of articles written especially for the Min-

neapolis Tribune, one of the major and most influential newspapers in the United States. The nine sections in the book, written by distinguished scientists and science writers, are devoted to astronomy, mathematics, meteorology, archaeology, the earth, rockets and satellites, cancer, the atom, and plasma physics.

The section on astronomy written by Dr. Harlow Shapley deals with what the universe is and how it is measured, theories of its origin, the evolution of the solar system,

and the possibility of life on other planets. The mathematics section covers the history of numbers, the concept of zero, big and small numbers and exponents, types of mea-

surements, and the concept of infinity. In the chapters on meteorology Dr. Harry Wexler writes about the factors that cause different climates and local weather conditions, and about weather satellites and other tools the meteorologist uses in predicting the weather, plus a forecast of weather control by man in the future. The section on archaeology traces the events which led to the discovery of early man in the Americas. The shape, size, structure, and composition of our planet are discussed in the chapters on the earth, as is the story of the Mohole project. (Continued on back flan)

FROM

ATOMS

TO

INFINITY

AUTHORS

Harlow Shapley Isaac Asimov

Harry Wexler

John Chapman Willy Ley John A. O’Keefe

Willard Bascom Victor Cohn Frank C. Hibben

Hugh Odishaw Clifford D. Simak

READINGS

IN MODERN

SCIENCE

FROM ATOMS TO INFINITY [Illustrated with photographs Drawings by victoR LAZZARO

HARPER

& ROW,

PUBLISHERS,

NEW

YORK

FROM

ATOMS

TO INFINITY

Text copyright © 1963, 1964, 1965 by Minneapolis Star and Tribune Company Drawings copyright © 1965 by Victor Lazzaro Printed in the United States of America. All rights reserved. No part of this book may be used or reproduced in any manner whatsoever without written permission except in the case of brief quotations embodied in critical articles and reviews. For information address Harper & Row, Publishers, Incorporated, 49 East 33rd Street, New York, N.Y. 10016.

Library of Congress Catalog Card Number: 65-14489

CONTENTS

PREFACE

—

ix

INTRODUCTION

Hugh Odishaw

The Importance of Scientific Research

xi

ASTRONOMY

Harlow Shapley

Clifford D. Simak

The Dimensions of the Universe

The Origin of the Universe Life in the Universe Our Place in the Galaxy

3

13 21 30

MATHEMATICS

Isaac Asimov

The History of Numerals The Advantages of the Metric System An Easy Way to Handle Big Numbers

4] 49 55

The Concept of Infinity

61 METEOROLOGY

Harry Wexler

The Earth's Atmosphere

69

How the Weather Is Made

78

Forecasting the Weather

86

Future Forecast and Weather Control

96

ARCHAEOLOGY

Frank C. Hibben

How Man First Came to America

107

The Folsom Man

114

The Clovis Mammoth Hunters

12]

The Sandia Cave Men

127

vi

¢

Contents

THE

Isaac Asimov

John A. O’Keefe Isaac Asimov

Willard Bascom

EARTH

The Shape and Size of the Earth

137

The Pear-Shaped Earth

144

The Structure of the Earth

152

Project Mohole

159

The Methods and Problems of

Drilling Under the Sea ROCKETS

Willy Ley

AND

168 SATELLITES

The History of Rocketry

179

How a Rocket Works

187

How a Satellite Works

197

Future Uses of Satellites

206

PLASMA

John Chapman

PHYSICS

The Fourth State of Matter

217

How We Can Use Plasma—

the World of

MHD

225

Unlimited Power for the Future THE

Isaac Asimov

232 ATOM

The Electron

243

The Proton and the Neutron

251

The Structure of the Atom

260

Isotopes

268

Antimatter

276

Contents

°

vii

CANCER

Victor Cohn

The Cell

287

Viruses

297

Chemistry Against Cancer

305

Cancer Epidemiology

312

ABOUT

THE

AUTHORS

321

INDEX

325

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PREFACE

The articles in this book were published in 1963 and 1964 by the Minneapolis Tribune in its Science Reading Series. The Tribune’s Science Reading Series is one newspaper's contribution to a better appreciation by its readers of the momentous changes in modern life occasioned by the scientist. The Series also is designed to furnish supplementary reading in science for the secondary schools. A board of educational and scientific advisers works with the Tribune editors to plan and produce the articles. The Tribune publishes an article each week during the school year on some aspect of science, written by a scientist, a research man, or a recognized science writer.

Preprints of the articles and study outlines for each article are furnished to teachers using the program. The articles are being used in more than 2,500 classrooms in the Tribune’s primary circulation area of Minnesota,

North Dakota, South Dakota, and western Wisconsin. ix

x

¢

Preface

The Series is intended to outline those theories and principles which~are fundamental to an understanding of science, and to link the newspaper reader more

closely to the work and thought of the scientific community.

C.DS.

INTRODUCTION

THE OF

IMPORTANCE

SCIENTIFIC

RESEARCH

Hugh Odishaw

Today few people question the importance of scientific research because our standard of living and military capabilities depend upon it. The development of weapons such as guided missiles and nuclear bombs testifies to the powerful military applications of science. Mass production and the outpouring of new goods, from antibiotics to stereo phonographs, testify to the general applications of science. Common sense then suggests that research is important because it yields practical results. The interplay between science and technology is both close and complex. Moreover, it is not a one-way street. While much of modern technology and industry rests upon scientific discoveries of the past, science also benefits from the tools, instruments, and methods growing out of technology. Research in space provides a current illustration of the interrelationships between science and

technology. Rockets, satellites, space probes, and other space craft are powerful tools for scientific investigation. The asxiii

xiv

¢

Introduction

tronomer wants to place his telescopes above the masking layers of the earth’s atmosphere so that he can see farther and more clearly into our galaxy and beyond. The solar physicist wants to measure the full range of particles and radiations from the sun before they interact with the atmosphere. The biologist looks to the day when space craft will permit him to see whether living matter exists on Mars. The physicist wants to detect and measure the contents of interplanetary space, consisting of particles, radiations, and electromagnetic fields. These scientists and others view space systems as tools and, more specifically, as carriers of detecting and measuring devices. To them the vast engineering and industrial complex engaged in the production of space systems is neither more nor less than the provider of transport—transport into space.

This suggests one way in which science and technology are tied together, but the relationship is actually far more complicated. Rocket systems have a long history, some of it empirical, some of it dependent upon scientific discoveries and research. The ancient Chinese invented rockets for celebrations and even for war. Heron of Greece discovered the principle of jet propulsion. Newton enunciated the laws governing bodies in motion and even explained how an artificial satellite could be placed in an orbit about the earth. But not until scientists, over many decades, acquired

knowledge of metals, alloys and ceramics, of fuels and oxidizers, and of mechanics and aerodynamics, was it possible to develop practical space systems. So science of the past underlies the current technology of space systems, whose problems today are largely of an engineering nature. Looking ahead, however, science is bound to con-

Introduction

¢

xv

tribute to more effective space systems. Investigations

in chemistry and metallurgy, even though unrelated to the space effort, may be establishing, bit by bit, foundations for future application. Moreover, it is also clear that the possible development of such new propulsion

devices as nuclear rocket engines will rest heavily upon past and current research. The whole of nuclear physics and nuclear engineering

is based upon a succession of research efforts by scientists in several countries over a period of about fifty years. The story begins with the discovery of natural radioactivity in 1896. It continues during the next fortythree years with successive discoveries of atomic and subatomic particles. The period concluded with the realization of artificial fission of the uranium nucleus in 1939. This event capped the preceding decades of fundamental investigations, during which individual workers sought to determine the various features of atomic structure, and opened the door to the development of nuclear engineering, with its military and civilian implications, and to the rapid growth of research in nuclear physics. A similar story can be told in the field of communications, which now represents a complex of technical and commercial endeavors that engage the energies of hundreds of thousands. In 1887 Hertz discovered radio waves. A few years later Marconi demonstrated their usefulness in sending signals, triumphantly transmitting a message across the Atlantic in 1901. This feat was remarkable because radio waves, like light waves, largely travel along straight

lines, and therefore it was considered impossible for the signals to curve around the earth. Thirty years before, Balfour Stuart had speculated

xvi

¢

Introduction

that there must be an electrical conducting region high in the earth’s atmosphere. In 1902 Arthur Kennelly in the United States and Oliver Heaviside in England turned to Stuart’s speculations and developed theories about such a conducting-reflecting layer. Heaviside even suggested prophetically that the conductivity of this region, which we call the ionosphere, was due to the presence of positive and negative ions, probably produced by the action of ultraviolet radiations from the sun. For nearly a quarter of a century no proof for this hypothesis was obtained, but meanwhile application progressed. By 1924 a worldwide system of telegraphy had been established while advances in radio art included the invention and application of radio tubes. Then in 1925 Breit and Tuve in the United States and Appleton and Barnett in England independently supplied experimental proof of the ionosphere, ushering in a period of research on this set of electrified layers and on the properties of radio waves. One of the byproducts of the work of Breit and Tuve led to other paths of research and application, for they had detected the ionosphere and calculated the height of the reflect-

ing layer by sending short pulses of radio energy upward and receiving their reflections. This technique represents the basic element of radar, and I cite it only to suggest the many ramifications possible as science and technology pick up an event, a discovery, some new knowledge and then pursue the leads that have opened up. In an astonishingly short period of time AM and FM radio, television, radar, and similar enterprises flourished and have become established familiar features of life. Electronics developed within a few decades into a

vast industry, providing to science instruments of un-

Introduction

°-

xvii

paralleled sensitivity with innumerable practical uses.

The whole fantastic field of computers burgeoned, following the last war, bringing tools for industrial automation, for commercial information processing, and for the solution of mathematical equations as well as the analysis of monumental bodies of observational data in

the geophysical sciences. What is the significance of these examples? They make vivid the generalization that science and technology are related. They indicate that research leads to technological progress and that technology, in turn, provides tools for research. But I hope they also suggest that research does something more than provide information which can be applied to man’s material interests. For research is above all a search for knowledge about nature. The work of atomic and nuclear physicists, from the time of the discovery of natural radioactivity to the present, has been concerned with ferreting out and clarifying the character and structure of the atom and the nucleus, not with the development of weapons or power reactors.

Admittedly, this is an oversimplification. The range of activity embraced by science and technology is large and continuous, like the infinite gradations between pitch-black and snow-white. At one end we might think of technology as simply and only producing consumer’s goods. At the other end we can think of science as concerned only with theoretical models of the universe. In between there exist all grades of intermixing. A scientist engaged in applied research can and often does discover new knowledge. Another scientist, interested only in the laws of nature, may find his work sooner or later applied to practical problems or he may

xviii

¢

Introduction

himself hit upon an invention of commercial value. Nonetheless, if we think of the unique role of science, of research, we are talking about the pursuit of knowledge about man and the universe. Research in this sense has an importance that cannot be properly evaluated because it is concerned with the intangible and at the same time with the whole scheme of things. Something of its deep roots in man and something of its spirit are embodied in the following quotation from the great Norwegian scientist, explorer, and statesman, Fridtjof Nansen: “The history of the human race is a continuous struggle from darkness toward light. It is therefore of no purpose to discuss the use of knowledge—man wants to know and when he ceases to do so he is no longer man.” i There is an irony in contemporary justifications of research. We justify scientific research because it contributes to applications in technology. We should justify research because it contributes, along with other intellectual and spiritual activities of man, to insights into the fundamental nature of things. The irony is this: Out of these insights comes man’s real mastery of his physical environment, for applica-

tions are a by-product of fundamental research. Applied science is concerned with the exploitation of the known; research in science is concerned with the unknown. Research, in a sense, is a process of rigorous exploration—sometimes experimental, sometimes theoretical,

but always highly creative and usually highly individu-

alistic. It is an imaginative exercise of mind and spirit, but rigor enters into the process. For the scientific method requires a quantitative approach, hypotheses are tested against facts, and the facts must be verifiable

by all investigators.

Introduction

¢-

xix

Once we have acquired new knowledge, we have attained at least two things. First and foremost, we have added to our understanding of nature. Second, we have acquired information which usually can be med in a practical way, as the history of science demonstrates. The danger is that the emphasis within our society will be laid upon applied research, which feeds upon the known, and that we will forget the much more difficult and even more important role of fundamental research. It is the latter which extends the frontiers of knowledge. There is yet another aspect of pure science which lays claim upon our attention. Nansen said that the history of the human race is a continuous struggle from darkness to light. Science has played its part in this struggle which has engaged the energies and passions of men in

various fields, from art to zoology, throughout the ages. It has played its part not only by providing deeper in-

sights into nature, but it has played an added part

through its questioning spirit. As new knowledge is obtained, old ideas are questioned and new ideas are advanced. This continuous process has an impact upon man as a whole as well as upon a scientific hypothesis. Thus the concept of an earth-centered solar system did not give way easily to a new astronomy, with the sun at the center and the earth relegated to one of several planetary orbits, for the old concept was bound up with custom and belief.

In this sense science, by questioning old notions and prejudices, has served mankind through new insights into the nature of man and the universe.

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THE DIMENSIONS OF THE UNIVERSE Harlow Shapley

It is easy to ask questions about the universe: How big is it? How old is it? What was its origin and how will it end, if at allP But these questions are not easy to answer. To answer some of them definitely is impossible

now. It may always be impossible for students of science. Two of these questions, how big is the universe and - how was it made, can be partially answered at the present time.

First we should get clearly in mind what the universe is. It is everything that exists and, equally important, those forces which operate within it. The most basic qualities of the universe are space, time, and matter. There is a still more basic quality—existence. But when we inquire into even such a simple-sounding question as why does the universe exist, we find it is too philosophical for us who try only to measure the dimensions of the universe and its many parts.

4

e¢

From Atoms to Infinity

There are other qualities as well as space, time, and matter. They aré all grand concepts, but less fundamental than the first three. There is gravitation, which

not only holds.a man and a building and the atmosphere to the earth, but which is also a force in determining the operation of the universe. There is motion,

The Milky Way galaxy is a great star system containing

6s

The Dimensions of the Universe

¢

5

which is not only the motion of a man walking, but the motion of the electrons which make up an atom, and also the motion of the galaxies as they flee from one another in our expanding universe. And there are, as well, relativity, acceleration, life, growth, and cosmic evolution. All of these things make up the universe. about 100 billion stars. (Lund Observatory, Lund, Sweden)

“$0”

60°

6

¢

From Atoms to Infinity

We shall concern ourselves here only with the kind of material things of which we shall measure, or try to measure, the dimensions. The biggest thing we shall measure is the metagalaxy; the smallest, the electron. Galaxies are great star systems, each containing from one hundred million to one hundred billion stars. The metagalaxy is the whole system of galaxies. It is practically the same as the material universe. But it is not the total universe, which contains time and space and the other immaterial concepts. The images of more than a million galaxies are now on the photographs taken by the telescopes at Harvard University. Greater telescopes than the ones used there have probed deeper into the metagalaxy. What they

have photographed confirms my calculation that many billions of galaxies are within the distance that can be fathomed by today’s greatest telescopes. Since a fair estimate of the number of stars in an aver-

age galaxy is ten billion (our galaxy has ten times that many), the total number of stars in the universe is considerably greater than a hundred thousand million bil-

lion (the figure one, followed by twenty zeros). Of all the galaxies, we can see only three or four with the naked eye. With a large telescope we can see dimly,

if we are looking for them, about a million galaxies. Using a camera linked with a telescope, with long exposures on fast plates, we can photograph something like two and a half billion galaxies. By using the big radio telescopes, substituting electronic devices for the photographic plate, that last number can be increased considerably. Electrons and the nuclei of atoms are the smallest permanent particles we now know. The diameter of the electron is approximately one ten-trillionth of an inch.

In comparison, the diameter of the metagalaxy is

The Dimensions of the Universe

¢

7

greater than ten thousand mega-light-years. A light-year is the distance that light travels in one year, nearly six trillion miles. A mega-light-year is a million light-years. To give a better idea of what these figures mean, we can set up a table of approximate diameters. So that the table will be in familiar terms, let’s give the figures in inches, But one must remember that there is a considerable variation in some of these diameters. Only for the earth and sun are the figures fairly precise. The diameter given for the solar system is the orbit of Pluto. Pluto is the planet farthest from the sun and the diameter we use is the distance across the wheel of the solar system, from Pluto’s position on one side of the sun to its position on the other. Atoms, from hydrogen, the simplest, to the complex uranium atom, are all about the same size, 10~® inches in diameter. Since the electrons and nuclei are only 10—* or 10~*? inches in diameter, we can see that the atom is mostly emptiness, for its diameter is 100,000 times the diameter of its parts.

In the table below, the diameters of the earth and sun are given accurately to the first decimal place, but for molecules there is a considerable spread in size. The outlying star members of our galaxy make its overall size

somewhat larger than given here. All diameters are given in inches. Electron — 10-18 Atom — 10-8 Gelatin Molecule — 10-5

Earth — 5 x 10° Sun — 5.5 & 10!”

Our Solar System — 5 X 10"* (80 a.u.)

Our Galaxy — 5 x 10” (100,000 light-years) Metagalaxy —

10°7

(102° light-years)

8

¢

From Atoms to Infinity

eA a a i In scientific work it is often necessary to deal in

very large or yery small numbers. To handle such num-

bers more easily, a system called exponential notation has been developed. In this system, we count by tens, using an exponent, a small number placed to the right of the number ten and slightly above it. Thus, 10° means ten multiplied by itself, or 10 x 10, or 100. And 10%, standing for 10 x 10 x 10, equals 1,000. In writing numbers in this fashion, the number written out would have as many zeros as the value of the exponent. Thus, 10° would be written out as one, with nine zeros following it, or one billion. And 10°7 would be one followed by twenty-seven zeros.

To express numbers more involved than one followed by a certain number of zeros, another number can be multiplied by an exponential number. Thus 2.5 x 10% equals 2,500—that is, 1,000 x 2.5.

To express numbers smaller than one, negative ex-

ponents are used. This is done by putting a small minus sign ahead of the exponent. Thus 10~? is one tenth, or 0.1, while 10-2 is one hundredth or 0.01. When written in decimal form, each decimal has one less zero to the right of the decimal point than the value of the exponent. Thus, 10~° is 0.000001 and 10-% is 0.00001.

The largest diameter in the table is 10*° times greater than the smallest; that is, the metagalaxy is 10,000,000,000,000,000,000,000,000,000,000,000,000,000 _ times larger than the electron, in diameter.

The Dimensions of the Universe

¢

9

In addition to the dust, gas, and radiations. which occur throughout the universe, there are many recognized bodies of matter. Let us now consider each of these, starting with the smallest and working up to the largest.

METEORS Meteors range in size from the high-speed micrometeorites, less than a millimeter (not quite fourhundredths of an inch) in diameter, to great masses of stone or metal. comETs In size, comets range from a little group of a few meteors to a loose organization as large as the

earth, but still of very little mass (that is, they have very little material in them). There doubtless are tens of thousands of these long-orbiting conglomerations of pebbles, dust grains, ice particles, and gas, but scarcely one in a hundred gets near enough to the earth and the

sun (from which they reflect a feeble glow), to be discovered and catalogued. Sometimes known as the minor planets, ASTEROIDS the asteroids are mostly found in an orbit between Mars

and Jupiter. They may be the fragments of an ancient planet which exploded. In diameter, they range from a few hundred miles to a few miles, and probably myriads of still smaller ones escape discovery because of the

faintness of the light they reflect. These are natural moons circling the SATELLITES planets, not the contraptions that men are shooting out into space. Thirty-one satellites circle around six of the nine major planets. Their diameters range from that of

Deimos, a moon of Mars, of about five miles, to the

3,200-mile span of Ganymede and Callisto, satellites of Jupiter.

10

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From Atoms to Infinity

The nine major planets of our solar system PLANETS are the only ones we have seen, but the theory of probability indicates that billions of planets may circle other

stars. Our planets, their diameter and mean (average) distances from the sun, are: DIAMETER Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Pluto

3,000 7,699 7,927 4,200 88,700 75,100 80,900 27,700 6,000

miles miles miles miles miles miles miles miles miles

DISTANCE FROM SUN 0.39 a.u. 0.7 2.3,1 1.00 a.u. L52:a\m. 5.20 a.u. 9.54 a.u. 19.19 a.u. 80.07 a.u. 39.46 a.u.

The abbreviation a.u. stands for astronomical unit. It is the mean distance of the earth from the sun, 93 mil-

lion miles, and is commonly used for the measurement of distances within the solar system. GLOBULES

A

recent discovery by the Australian as-

tronomer, Bart J. Bok, globules are spheroidal (spherelike) masses of cosmic dust and gas. Someday, when sufficiently pulled together and compacted by gravitation, they may heat up and become stars. NEBULAE

Sometimes

called

nebulosities,

these

are

clouds of gas and dust. In size they vary from nothing much to hundreds of light-years across.

STARS These standard units of matter in the metagalaxy are hot, gaseous bodies. They range in diameter from much less than half a million miles to a thousand million. In surface temperature, most of them range from 5,000 degrees Fahrenheit, to 50,000 degrees, with many temperatures, however, outside that range.

The Dimensions of the Universe

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DOUBLE STARS About half of the fifty stars closest to us are doubles, two stars revolving about a common

center. Alpha Centauri, which, at the distance of 25 trillion miles, is the nearest of known stars, is a double.

STARCLUSTERS Star clusters are mainly of two types —open and globular. A little over a hundred globulars are associated with our Milky Way galaxy. The globular

clusters contain many variable stars (stars which fluctuate periodically in brightness). These variable stars played method covery galaxy, spiral.

a great part of measuring that our solar but rather out

in developing the photometric stellar distances and in the dissystem is not in the center of our near the edge of its wheel-shaped

GALAXIES Galaxies are great organizations of stars. About 30 per cent of them take the shape of a spiral, 65 per cent are spheroidal, and 5 per cent are irregular in form. In distance from us they range from about 170,000

light-years (the Magellanic Clouds) to those faint objects

photographed at the limit of the 200-inch telescope at Mount Palomar. These farthest galaxies are three or four billion light-years from us. Galaxies range in size from 1,000 light-years to 100,000 light-years. GALACTIC

CLUSTERS

Recent

study of faint, far-off

galaxies has shown that many of them, perhaps most, are congregated in loose clusters. Some of these clusters

may have a dozen or so members; others have thousands.

The nearest of such clusters is the one which includes our own galaxy and the two Megellanic Clouds, the Andromeda galaxy and its two companions, and a few others, mostly small in size. METAGALAXyY

As was said earlier, this huge concept

accounts for the material universe. Not only does it in-

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From Atoms to Infinity

clude all the galaxies, but also wandering intergalactic star clusters, single stars, possibly planet-sized bodies.

Its diameteris more than ten billion light-years—how much more we cannot guess. Our deepest probing of it shows no evidence of a center or an edge. There may be neither!

Some of the questions concerning the metagalaxy that we could ask may be solved, or partly solved, by the ad-

vance of theory and of observing equipment in the future. Certainly more observation and more hard, clear thinking are needed. But some of the questions we could

ask may concern matters that are unknowable. That is something on which to meditate.

THE OF THE

ORIGIN

UNIVERSE

Harlow Shapley You may ask how the earth came about? Who or what made the moon, sun, and stars? How did life begin on the earth? Scientists also would like to know the answer to these questions. But the best that science can do is to consider the probabilities. Some of the tentative answers are based on high probabilities, others only on possibilities. Stated otherwise, some theories of the origin of planets, stars, and life are almost certainly correct, while others are but agreeable guesses. Let’s tackle these questions one at a time, starting with the moon; how did it originate and has it changed much with the passage of time? Does it now evolve? There are many hypotheses of the lunar origin, but nothing very convincing. The best of them suggest that the earth and moon were “born” at the same time as the materials from which all the planets formed. These suggestions indicate that the earth and moon never were a single body, but were from the beginning of the planetary system a sort of double planet, circling around the center of gravity of the pair as they do now, and together circling the sun. There is another well-known hypothesis of the moon’s origin: that it came out of the Pacific Ocean in the early days, thrown out by the rapid whirling of the primitive, or proto-earth. The density of the rocks in the earth’s crust is much

the same as the mean density (specific gravity) of the 13

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From Atoms to Infinity

whole moon. The expulsion theory would account both for the depth and size of the Pacific Ocean and for the earth’s rugged satellite. But the craters and the mountains of the moon were not produced at its birth; they have come later through the continual bombardment by the meteorites that roam the solar system.

It remains only to add that some believe the moon originated elsewhere and has been “captured” by the earth—a somewhat desperate hypothesis, for to capture and ease the moon into its nearly circular orbit would require much in the way of an interplanetary medium. All these hypotheses and others are being tested by the exploration of the ocean bottoms that is now proceeding as a continuation of the worldwide research

effort, the International Geophysical Year. And the attack on lunar mysteries—chemical makeup, origin, moon

quakes, magnetic properties, dust layer—will be much

advanced when and if landings are made by space travelers, landings of instruments and men, and by the return to the earth of data compiled by the instruments

or by the men in person! Is the moon evolving at the present time? Yes, but a

Wy

The solar system has nine planets and thirty-one moons

Ye GLLE

revolving around the sun.

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rot Beat es

The Origin of the Universe

°

15

slowly. There is a continual fall of meteoric dust and of meteorites on its surface, so that the mass is growing. The tidal effects—the moon dragging on the earth’s air, water, and rocks—very slightly slows down the earth’s rotation, lengthening the day; and to compensate for that decrease in momentum, the moon is very slowly receding from the earth, lengthening the month. A billion years ago the moon was closer to the earth and brighter. The days then were shorter and the tides higher. Gravitation then, as now, had complete control of the moon, as it has everywhere in the solar system. The origin and evolution of the solar system—of the earth, planets, and comets—also has encouraged much speculation. Once I tabulated sixteen different theories and was able to convince myself that none of them was sufficient to interpret satisfactorily all the abundant properties that observations yield—none of them sufficient, not even my own! But this failure to satisfy all the data is admitted by the many speculators. Here are some of the questions we ask scientists to answer: Why are the nine planets spaced as they are? Why do they move in the same direction around the

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From Atoms to Infinity

sun? Why are they moving so fast while the sun rotates so slowly (the momentum problem)? Why are the orbital planes so near each other, and near the plane of the sun’s

equator? What produced the thousands of asteroids moving mostly between the orbits of Mars and Jupiter? Where did the long-orbited comets come from? How should we explain the tiny moons of Mars that move in such a strange fashion? Why is the solar corona so

hot (a million degrees or more, when the temperature of the sun’s surface is only 10,000 degrees Fahrenheit)? There are, as well, many additional properties, such as peculiar planetary atmospheres, the numbers of moons, the sun’s interior—all of which we know about and cannot completely explain. Two major classes of theories are now recognized—the disruptive-collisional type which might explain the planets, moons, and comets, but not the sun; and the neo-Kant-Laplacian theory that fits our planetary system best and rests on the gravitational condensation of primeval gas and dust clouds. When the expanding universe was “young” and much more crowded together than now, there were undoubtedly more frequent collisions of stars and gas clouds than could occur now or in the past billion years or so. Collision-born planets must be reckoned with, but the dust cloud origin seems better suited to the sun’s family. The contraction of a great gas and dust cloud, it is surmised, would produce a big protosun, which somehow got into rotation. In the course of the concentration

and rotation of the dust cloud, matter (mostly hydrogen) would form persistent eddies that became the protoplanets. If these eddies were close together they would cancel each other or the weaker ones would be eliminated, thus spacing out the surviving planets. Sub-eddies would become the protosatellites moving

The Origin of the Universe

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under the gravitational control of the individual planets. The light gases, such as hydrogen and helium, would

escape from the planets that were not massive enough to hold the fast-moving lighter atoms. The young earth could retain heavier molecules like oxygen and nitrogen in its atmosphere, but not the hydrogen, which is by far the most abundant atom in the universe. We are, in fact, living on a remnant, the core of the

original protoearth; while big Jupiter and Saturn are able to retain most of their primeval hydrogen. Through the introduction of rather reasonable assumptions, this gas-and-dust contraction theory does very well in the explanation of the origin of all our solar system bodies; but we should always remember that there may be other ways (collisions, captures, explosions) in which planets could be, and probably to some extent have been, formed. It is now obvious that evolution is at this moment pro-

ceeding in our planetary system. For example, (1) the comets—(there are thousands of them)—are breaking up into meteor streams, some of them after their orbits have been distorted by the attraction of neighboring planets;

(2) the orbits of the thirty-one known satellites are being gradually changed through tidal action; (3) the sun is gathering in meteorites from interstellar space and is radiating its energy and mass away through the mutation of hydrogen into helium and gamma rays in its central regions and the outward flow of that energy into the

cold of space; (4) the earth is still adjusting itself through volcanoes and earthquakes; (5) the major planets are still sweeping up the debris of interplanetary space, and by that act suffer small orbital changes. Perhaps the fastest evolution is on the surface of the

earth, where

man’s

activities have produced

many

changes. There is some likelihood that the now lifeless

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moon and the questionable surface of Mars will some-

day undergo evolutionary changes through the agency

\ of man. Before we go into the depths of space in our search for evidences of the origins and evolution of stars, galaxies, and the universe itself, it will be proper to talk further about the stars. It is commonly believed that

they have all condensed from the gas and dust of space. Some are very big, some dwarfish, and literally millions are just about like our star, the sun. Miss Annie Cannon, an astronomer with the Harvard Observatory for forty-five years, made a great catalogue of more than 200,000 stars, putting them into about sixty different classes and subclasses. The sun is average in many ways, in color, temperature, chemical content, size, and mean density; but it is above the average in candle power and probably in mass. In all these properties are found gradations that bespeak evolution. The sun is a middle-aged star. In the globular clusters we have old stars; in the spiral arms of galaxies the giant bright stars are mostly young. Many of the bright stars of our sky are much younger than the Paleozoic rocks in the earth’s crust. The sun’s atmosphere contains more than sixty of the ninety-two standard kinds of atoms found on earth; but the astrophysicists believe that all but 1 per cent of the sun is hydrogen and helium. The hydrogen is growing less, the helium more, through a process which is in a sense the burning of hydrogen fuel into helium ash, releasing the gamma radiation that keeps the sun and most of the stars shining steadily through billions of years. More than half of the stars are double, or multiple, according to our census of nearby space. Millions are in star clusters. The globular star clusters are beautiful

The Origin of the Universe

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19

to behold, but they are not the last word in stellar organization. The galaxies, like our own home galaxy, the

Milky Way system, also are marvelous structures, but only by way of photographic plate are they well known to us.

More than a million galaxies are faintly seen on plates in the Harvard collection, and from sampling with

powerful telescopes we learn that there are at least ten billion of them within the reach of our instruments. And since the population of an average galaxy is something like 10° stars (our own galaxy, a giant, has

something like 10"'), we believe that there are in our explorable universe more than 10” stars. In words, that is more than a hundred thousand million billion. At last we come to that great mystery, the origin and evolution of the whole universe of stars and galaxies. Nothing much is really known as yet, but the theories are entertaining.

Three theories concerning the origin of the universe are the Big Bang (top row), in which all matter blew up and is still expanding; the No-Bang, or “continuous creation” hypothesis (middle), of a universe without beginning or end; and the Bang, Bang, Bang theory (bottom), of an expanding and condensing universe.

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There is the “big bang” hypothesis of Lemaitre and Gamow, which was inspired by the observational phenomenon of an expanding universe—the observation that the galaxies are all retreating from us and from each other at very high speeds. It suggests that many billions

of years ago all matter was concentrated in a primeval super-atom that blew up, with the chemical elements, the stars, and the galaxies appearing as by-products of this tremendous manifestation of radiant energy. And there are the equally strange hypotheses of Bondi, Gold, Hoyle, and others, which see in the observations and mathematical theory no evidence of the beginning of the universe, no forecast of an end. Theirs

is the “continuous creation” theory, which holds that hydrogen emerges from absolutely nothing at the right speed to keep the mean density of matter the same throughout all time, notwithstanding the disappearance of distant galaxies over the “rim of the world” with speeds greater than that of light. There are also some new observations with the 200inch Palomar reflector telescope which suggest that the

speed of expansion of the universe now is slowing down.

Perhaps it will stop expanding, then return to the condensed state, to the primeval atom, and again explode, repeating this pulsating operation again and again. We can thus list these preliminary theories as the Big Bang, the No Bang, and the Bang, Bang, Bang hypotheses. But the origin of the universe and the origin of matter are deep subjects requiring more observation and much more serious thought. We can well leave the subject at this point with the remark that origins and evolution certainly prevail throughout the entire material universe.

LIFE

IN THE

UNIVERSE

Harlow Shapley

Our thoughts about life throughout the universe are so numerous that we can devote but a few sentences to each phase of this most interesting subject. We shall first offer a working definition of life, remarking on life’s origin and requirements. Then we shall systematically examine the probabilities of life on each of the several

planets of our solar system, and finally advance some argument on its probable occurrence beyond the bounds of the solar system. Life is a chemical affair. It involves the activities of many kinds of atoms and of compounds of atoms. Its

systematic study during the past century has resulted in the emergence of a special science—biochemistry. The atoms appearing most abundantly in organisms are oxygen, carbon, and hydrogen. In the human body

the distribution of atoms, by percentage, is as follows: oxygen, 65; carbon, 18; hydrogen, 10; nitrogen, 3; calcium, 2; phosphorus, 1; all others, 1. The percentages vary little with the age of the body. And they are much the same for all mammals. The preponderance of oxygen is noteworthy. In the sun and the stars, and in the spaces between the stars, the quantity of oxygen is much less than 1 per cent. But in the crust of the earth it is the most abundant element —nearly 50 per cent, with silicon just half as much. The ocean is 89 per cent oxygen; the remainder is hydrogen and various salts, with a trace of organic matter in the shape of fish, whales, and plankton. The 21

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air we breathe is over 20 per cent oxygen. It thus appears that athough oxygen is not abundant in the universe at large, compared with hydrogen and helium, it is dominating in water, rocks, air, and the biological organisms of this planet.

Some giant molecules contain thousands of atoms. When these macromolecules, incited by the energy of radiation, divide in such a way that they duplicate themselves in structure and reactions, we have what we call life. May there not be kinds of life completely different from that which we know on earth, where life is based chiefly on oxygen, hydrogen, carbon, and nitrogen? We are asked, for example, why we cannot substitute silicon for carbon. These two elements have much in common; their compounds are similar in structure. But the biochemists

say No. On the earth we see no evidence of silicon taking the important place of carbon in living bodies. We learn from the spectrum analysis of stars and nebulae that there is a universal chemistry—the same elements everywhere. It is now believed by experts in the subject that there is also a universal biochemistry. Now let us examine possible sites in the solar system for the emergence and persistence of that delicate operation called life. Could there be living organisms on the surface of the sun or inside it? Of course not. For the surface temperature of the sun is 10,000 degrees Fahrenheit. The comparatively cooler sunspots still have a temperature of

6,000 degrees, and the internal temperatures run into millions of degrees.

These temperatures would make viable (capable of life) macromolecules impossible. The simple molecule H,O could not exist; and for the origin and evolution of

Life in the Universe

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organisms we must have water in the liquid state. Therefore there can be no protoplasmic life on the sun and, for the same reason, no life on any of the radiant stars. Mercury is the nearest of all planets to the sun. Observations by radio telescope made in 1965 now indicate that the planet revolves on its axis once every 54 to 64 days. There can be no liquid water on the planet, because on the side that faces the sun, the temperature is

nearly 800 degrees Fahrenheit, and on the opposite side it must be very far below zero. In one place it is too cold

for water and life of any kind, and too hot in the other. How about the twilight zone between the sizzling heat and congealing cold? Any life there? No, for several reasons. The chief of them is that the mass of Mercury is only a twentieth that of the earth; since the amount of gravity of a planet is dependent upon its mass, all gases would have escaped into space. There could be no permanent atmosphere. All life, by our definition, requires not only water but air as well. Mercury is, therefore, a lifeless desert. Venus, the second planet, is, much of the time, the brightest planet in our sky. It is generally misnamed the Evening Star or the Morning Star. Until recently the question of the possibility of life on Venus could not be decided. Clouds of nitrogen and carbon dioxide, possibly also of dust, completely blanket the surface, and no markings can be seen. Under such circumstances this “twin of the earth” has been left to the imagination of the fiction writers, at least as far as the length of the day and the nature of the surface is concerned. By some writers vital “Venusians” have been imagined—strange beclouded creatures that never see the sunlight.

At times in the past some weak evidence has been put

forward in favor of a short rotational period for Venus, but other evidence has been advanced in favor of a

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longer day—perhaps 225 earth days, the same as the period of the revolution of Venus around the sun. Then, a few years ago, the puzzles were at least partially solved and the “Venusians” became more than ever fictional. The conclusion that there can be no protoplasmic life on Venus came as the result of advances in electronics. The radio telescope, the development of which was a by-product of World War II, settled the matter by penetrating the cloud blanket that surrounds the planet and finding that Venus emits long-wave radiation that is characteristic of surfaces with temperatures above 600 degrees Fahrenheit. That appears to dispose of the question of life. Venus is too hot for life. The radio telescope is able to “see” the surface of Venus and other nearby planets because it can detect the long waves which can get through the cloud blanket; the much shorter infrared, visual, and ultraviolet radiations from the surface of Venus are almost completely blocked by the cloud layer. It is only by sunlight reflected from the top of its atmosphere that we see Venus. The radio telescopes not only answer the questions of life and temperature, but also indicate that the rotation

period (the Venus day) is the same as the orbital period —225 of our days. Venus, therefore, keeps one face to-

ward the sun. But because of its moving gaseous atmosphere, the temperatures on the day and night sides do not differ so conspicuously as they do on Mercury.

- Mercury and Venus, the planets nearest the sun, are

too hot to sustain life. Mars may have some form of life, and Jupiter may too, due to the greenhouse effect of its

cloud cover. Saturn, Uranus, Neptune, and Pluto are far too cold to support life as we know it.

Life in the Universe

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The planet Earth here requires no special attention. Everyone admits the existence of life on planet No. 3. And it appears in a million different forms—plant and animal—many millions, in fact. There are more than 200,000 kinds of beetles now known and 15,000 species of ants; and much of the world is not as yet thoroughly explored. One further remark on the earth’s biology. Life has been on the surface of the earth for at at least one and a half billion years, according to the best tests of the ages

of the fossils found in the sedimentary rocks. That must mean that the strength of the sunlight necessary for photosynthesis has been essentially constant for all these years. From that conclusion we are led to another, namely, that to keep the sun steady in radiation for such a long time an unfailing source of solar energy must be found. Gravitational compression would not suffice, or meteor infall, or just simple burning at the surface. The source

was sought, and found to be the burning of hydrogen as fuel into helium ash in the center of the sun; that is, transforming hydrogen atoms into helium atoms and short-wave gamma radiation. The internal temperature required for this operation is of the order of 20,000,000 degrees Fahrenheit. By the time this central heat has “leaked” to the surface of the sun it is down to a comfortable temperature of about 10,000 degrees. This surface heat of the sun flows into space and of this one two-billionth part falls on

the earth, providing our steady light and heat. We have here a good illustration of the profitable tieup between two sciences: Paleobotany joins astrophysics, the ages of fossile algae bear on the mutations of chemicals in the centers of stars trillions of miles away.

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Mars is the most talked of member of the sun’s family, excepting only our obsession with the earth. The Martian appeal is as much romantic as it is scientific. Hun-

dreds of hypothetical space travelers and exaggerators. have woven Mars and the off-human Martians into their fiction. From a purely astronomical standpoint, the planet is rather second-rate—with small, desert-dry, uninteresting, dim surface features and undersize moons. But

from a biological standpoint there is much of interest —so

much,

in fact, that our modern

astronauts

have

Mars listed for a visit as soon as the lunar curiosity abates. The easily observed seasonal changes on the Martian surface are responsible for much of our interest, since the best interpretation of these changes indicates that they are biological. But it must be a tough biology on that planet No. 4 when judged by terrestrial standards. The air is thin, the temperature cold (40 degrees below zero Fahrenheit, on the average), oxygen is very scarce, and there is just enough water vapor to produce in the Martian winters some polar ice caps (or possibly caps of hoar frost). In the proper summer season, however, there is a little water in a liquid state, and there are, therefore, likely to be simple forms of life.

When the astronauts arrive and land, they must carry their customary earth environment with them, the same as for landings on the moon. Probably all kinds of living things, such as we have on the earth, would promptly

die if transferred to Mars. But that does not mean that life could not have originated independently on Mars and become adjusted to the physical conditions prevailing there. We humans could not adjust, but possibly low algae forms from earth might survive temporarily. Why is the Martian air so thin? Clearly because the

Life in the Universe

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mass and surface gravity are small compared with that of earth. The Martian air probably is composed of nitrogen for the most part with a good deal of carbon dioxide.

The original supply of oxygen, if any, has been depleted in the rusting of the surface rocks, which has given the planet its reddish color. The localized changes in color have been ascribed by some investigators, wholly or in part, to seasonal dust storms, or even to lava flows. But the growth and dying out of vegetation remains the best interpretation. There-

fore, the best reply to the question, Life on Mars? is “Probably.” Asteroids by the tens of thousands, moving in orbits

mostly between the orbits of Mars and Jupiter, are airless and waterless, and therefore lifeless. They do not have enough mass to hold air or water.

If the asteroids did originate, as many believe, from the destruction of one or more planets, we may rightly

surmise that the recently found organic compounds in meteorites may point to the former existence of a planetary site of life, a site that once existed on the outer fringes of the solar system’s liquid water zone, But at present this is crass speculation.

Jupiter is now getting some attention from the lifesite hunters. In the past it was ruled out as too cold, but it is now possibly qualifying because of our recognition of the greenhouse effect. The surprisingly high temperature of Venus is properly ascribed to its thick atmosphere acting like the glass of a greenhouse, transmitting sunlight inward, but cutting down radiation upward from the surface.

If the same effect prevails on Jupiter, which also has a heavy cloud cover, its surface may be warmed up to a livable range despite the fact that the top of the atmosphere measures a temperature of —200 degrees F.

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Saturn, the second largest planet in the sun’s family

(Jupiter is the largest), is disqualified as a site for organic existence

because

its temperature

is more

than

240 degrees below zero, much too cold for protoplasm, even with some help from greenhousing. The atmosphere is hydrogen gas, adulterated with methane and ammonia snow. It is so thick that the planet as a whole

is lightweight—it would float on water. The picturesque rings of Saturn are moonlets, billions of them, probably composed of water ice, and of course, lifeless, as also must be the many satellites. Titan, Saturn’s largest moon, is a little larger than our

own moon. According to Dr. Gerard Kuiper, a high authority on planetary atmosphere, Titan has an atmosphere of methane. But there can be no Titan biology. The moon is much too cold.

Uranus and Neptune are hopelessly frigid and so are their satellites. Both are far from the sun. Pluto, the ninth and most remote of the sun’s organization of planets, is colder still-perhaps 350 degrees below zero. Further out are some long-period comets and count-

less meteors, but in our survey we have passed far beyond the realm where the sun can, in sufficient strength, be a provider of life-sustaining radiation. Does life exist elsewhere among the stars?

There are in the Harvard spectrum catalogues compiled by Miss Annie Cannon at least forty thousand nearby stars very much like the sun in size, color, temperature, motion, affiliations, and candle power. And in our total home galaxy there must be billions of duplicates of our own sun. And the same thing holds true in billions of other galaxies. Probably about half of these sunlike stars have planets. Certainly many, many millions will have

Life in the Universe

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29

planets like the earth in all respects, such as distance

from their stars, size, chemical makeup, length of years and day, and age. Since

we

have,

as mentioned

above,

learned

the

mechanism of the emergence of the animate from the inanimate, the living from the not alive, and have proposed that we ourselves are but one item in the wonderful stream of evolution from atoms to macromolecules to organisms to man and the other higher animals, we are in a proper position to say confidently that there must be life, living biochemicals, scattered all over the universe.

In some of the innumerable places where life occurs, the biological evolution may indeed be very similar to that which we know here on earth. But we must remember that there are millions of variations on the plant and animal theme, even here on earth. Hence a belief

in the exact duplication anywhere of Homo sapiens is not very sapient!

OUR PLACE IN THE GALAXY Clifford D. Simak In the three preceding chapters Dr. Harlow Shapley has discussed the dimensions of the universe, the theories concerning its origin, and the possibilities of life on planets other than the earth. Dr. Shapley himself has made important contributions to our knowledge of the true nature of the universe, and by his work he has become known as the first of the modern astronomers. In the early part of the twentieth century a man

named Jacobus Cornelius Kapteyn was director of the Groningen Astronomical Observatory in Holland. Kap-

teyn had made the mapping of our galaxy, the Milky Way, his life work. In working on his maps, Kapteyn concluded that the galaxy was shaped like an elongated pancake, with a

diameter of some 20,000 light-years. (Since a light-year is approximately 6,000,000,000,000 miles long, the diameter of the galaxy was about 120,000,000,000,000,000 miles across.) Our sun and its planets, Kapteyn said, were in the approximate center of the galaxy. This was, of course, an important discovery and proved to be a fairly accurate determination of the

shape of the Milky Way galaxy. However, Kapteyn and the other astronomers of his day did not know that there were any other galaxies or stars beyond those in

the Milky Way. This was the situation when, in 1912, Henrietta Leavitt, an astronomer at Harvard Observatory, made

what at the time seemed a minor discovery. 30

Our Place in the Galaxy

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The daughter of a clergyman, Miss Leavitt was a quiet, reserved

person,

passionately

attached

to her

work. For some years she had been studying certain variable stars in the Small Magellanic Cloud. The Small Magellanic Cloud, we now know, is ancther galaxy, in the same cluster as our own galaxy. The variable stars she had been studying are of the

type known as cepheids. The cepheids are pulsating stars—that is, they contract and expand. When a cepheid contracts, its temperature rises and it shines more brightly. As it expands, it cools and shines more dimly. Another thing about the cepheids is that this rate of contraction and expansion is no haphazard thing. Each of them has an absolutely fixed rate of pulsation. It has

been said that if all the clocks in the world should stop, they could be reset to exact time by the pulsation of the

cepheids. Polaris, which we know as the North Star, is a cepheid. It has a period of 3 days, 23 hours, 16 minutes, and 14 seconds. The periods of hundreds of other stars of this type now are known as precisely as that of Polaris. Miss Leavitt, back in 1912, discovered something else about the cepheids: Their brightness was in direct proportion to the period of their pulsation. The dimmest of the cepheids had short periods. The brightest has long periods, in some instances periods lasting several months.

In 1914 young Harlow Shapley joined the staff of Mount Wilson Observatory in California. At that time the observatory was using a 60-inch telescope, then the largest in the world. The 100-inch lens which was to be installed later was then in production. But the 200inch glass at Palomar was as yet undreamed of. For several years Shapley was concerned largely with the study of globular clusters. From this study he rea-

The Small Magellanic Cloud is a galaxy about 160,000 light years distant-from the earth. (Yerkes Observatory)

Our Place in the Galaxy

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lized that the globular clusters, instead of being wisps of gas as had previously been thought, were actually great aggregations

of stars. These

stars were

so close

together (relatively, that is) that it was difficult to make out individual ones. Generally one simply got the impression of great blobs of light. Many of the stars that Shapley could make out were pulsating stars, like the cepheids that Miss Leavitt had been studying. About this time Shapley and Ejnar Hertzprung were seeking new ways to measure the distance of stars. In the course of this Shapley made an assumption based on Miss Leavitt’s findings. He assumed that all the cepheids in the Small Magellanic Cloud were the same distance from our sun. Once again, this matter of distance was relative. Suppose that you have several friends who live in Italy. Each of these people may live many miles from one an-

other. Yet you think of them as living the same distance from you. Their difference in location within Italy itself becomes insignificant as compared with the distance from your home to Italy. This would be the situation with the stars in the Small Magellanic Cloud. They might be trillions of miles apart and yet we can think of them as the same distance from us since the Small Magellanic Cloud is 160,000 light-years distant. For all practical purposes they are the same distance. Since the cepheids in the Magellanic Cloud were the same distance from us, it then must also be true that the degree of their brightness would be due to actual difference in their brightness rather than to distance. Suppose, then, that you could measure the distance to

one cepheid which has a period of five days. Once you knew the distance to that cepheid, then you could meas-

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ure the distance to all cepheids with five-day periods. If a five-day cepheid, anywhere in the sky, was dimmer than the one to which you had measured the distance, then that dimness would be due to distance. It would be farther away and how much farther away could be calculated by the degree of dimness. If it was brighter, then it would be closer and that, once again, could be calculated. Nor is that all. Once you knew the distance of a five-

day cepheid, you could then calculate the distance of any cepheid of any period. To do this you would only have to use the scale of brightness as related to the periods worked out by Miss Leavitt. In her work Miss Leavitt had established the relationship between the period of a cepheid’s pulsation and its brightness. She had not carried her conclusions beyond that determination. Now Shapley went a long step further. He related the period-luminosity relationship to the distance that the star might be from us. The distance to the cepheids in the Magellanic Cloud was difficult to measure. But scattered throughout the sky and concentrated in the globular clusters are other stars, the RR Lyrae stars, which have a period-luminosity relationship similar to the cepheids. Using established methods of measurement, Shapley

learned the distance to some of the RR Lyrae stars, and eventually to some of the cepheids in the Magellanic Cloud. Prior to this there had been two methods of measurement used to determine the distance of stars: the triangulation method and the spectroscopic parallax

method. To explain these would take another chapter

fully as long as this one, so we won’t attempt it. But the point is that the triangulation method was valid only to about 300 light-years and the spectroscopic parallax

Our Place in the Galaxy

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method was useable only to about 3,000 light-years. But now Shapley had a new yardstick. By using the scale of brightness in the cepheid and RR Lyrae stars, as related to their periods of pulsation, you could measure the distance to any star of these types, no matter how far away it might be. All you had to do was to be able to determine its brightness and its period of pulsation. Having set up his yardstick, Shapley went back to his globular clusters. Using the yardstick to measure the

distance of the cepheids which he had found in the clusters, he was amazed to find that some of these distances were more than twice as great as that which Kapteyn had set for the entire Milky Way galaxy. Another thing bothered him as well. The globular clusters simply were not grouped in any way that it was reasonable to expect. They seemed to be concentrated in one area. One-third of them occurred in one-thirtieth of the sky. In thinking about this grouping, Shapley assumed that the globular clusters were concentrated about the center of our galaxy. If this were true, then our sun and its planets were not, as Kapteyn and all other astronomers had thought up until that moment, in the center of the galaxy.

Shapley was well acquainted with the work of the Danish existentialist and theologian, Kierkegaard, from whose writings he now remembered a phrase, “the leap of faith.” Shapley took his “leap of faith.” In 1918 he announced

his conclusions. The Milky Way galaxy, he said, was 300,000—not 20,000—light-years in diameter; our solar system was not in the center of it but near its rim. This was all but the final step toward destroying the egocentricity of man in relation to the universe. Until

the sixteenth century the earth had been believed to be

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the center of the universe. Earth was finally toppled from that central position, which was given to the sun. And now the sun, which had been believed to be located in the center of the galaxy, had been moved out

to its rim. In a few years’ time Edwin Hubble, another of the great American astronomers, would show that our galaxy was only one of billions of galaxies. With that announcement, man’s belief in his central position in the universe would be gone forever. At first Shapley’s findings were scoffed at. But as time went on he began to gain support. In 1920 the National Academy of Sciences staged a debate with Shapley defending his view and Heber Curtis, then at Lick Ob-

servatory, speaking for the view still held by Kapteyn and many others. So ably did Shapley present his case that he convinced a great part of his audience. Shapley was wrong, however, in his figures. Not realizing that dust between the stars existed to such a degree that it cut down the brightness of the stars, he had overestimated his distances. The size of the galaxy eventually was reduced from his 300,000 light-years to 100,000. But his basic assumptions were correct.

Shortly atfter Shapley’s announcement of his findings, Bertil Lindblad, a Swedish astronomer, suggested that the galaxy rotated about its center. He based his theory on the teachings of mechanics that no such system as a

galaxy could be stable unless its components (its stars, in other words) were held apart by a centrifugal force arising from the rotation of the whole. In 1927 Jan Hendrik Oort, the Dutch

astronomer,

demonstrated that the galaxy did, indeed, rotate. Furthermore, he showed that it rotated about the region of Sagittarius, an area of the galaxy some 80,000 light-

years distant from us. It had been in Sagittarius that

Shapley had placed the center of the galaxy.

Our Place inthe Galaxy

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37

Oort’s discovery left no doubt about the rightness of

Shapley’s findings. Shapley had won the day. Man and the earth and the sun were out in the suburbs of the galaxy. In comparison with the nineteenth-century astronomers, whose ideas had hardly changed since the time of Isaac Newton, Shapley was the first of the modern

astronomers. Today he might be said to have made a “breakthrough” in our thinking about the universe. After him came many others with the ideas and the observations which give us our present concept of the universe. But of them all, Shapley was the first.

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MATHEMATICS

THE OF

HISTORY

NUMERALS Isaac Asimov

At an early time in history, men found that it would be helpful to invent a shorthand code of marks to symbolize numbers. Thus it would be possible to simplify the records of business transactions and tax payments.

(Imagine, today, having to write your street number or telephone number in words every time you wanted to

record it.)

The easiest way to set up a number code is to make a little line for each unit. In that way, / could be “one,” it could be “two,” Wilt could be “seven,” and so on. This is exactly what the ancient Egyptians did, over three thousand years ago. The ancient Babylonians did the same thing. How-

ever, they wrote by pressing a stylus, or sharp-pointed instrument, into soft clay. This made wedge-shaped marks instead of straight lines and their numbers therefore looked like this: y “one,” YY “two,” WY “seven,

and so on. However, it quickly becomes wearisome to

make many marks for high numbers, and also it becomes 41

42

e¢

From Atoms to Infinity

hard to read thém. Whether you are writing or reading,

you have to stop and count, and it is very easy to make an error in counting.

One way out of this dilemma was to make use of different kinds of marks. Men originally counted on their fingers, and the little marks used for units do look like fingers. Well, once you get to ten “units” or fingers, you have used both hands. Instead of making ten little finger marks, why not make a special mark of a hand?

The Egyptians let the mark Q represent the ten fingers of the hands while the Babylonians used