Part 1

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THE WAYS OF THE PLANETS

BY MARTHA EVANS MARTIN, A.M. AUTHOR OF “THE FRIENDLY STARS”

NEW YORK AND LONDON HARPER & BROTHERS PUBLISHERS MCMXII

COPYRIGHT, 1912, BY HARPER & BROTHERS

PRINTED IN THE UNITED STATES OF AMERICA PUBLISHED OCTOBER, 1912

CONTENTS

CHAP. PAGE

I. ON MAKING ACQUAINTANCE WITH THE PLANETS 1

II. OUR RELATION TO THE PLANETS 11

III. WHAT THE PLANETS ARE, AND WHAT THEY APPEAR TO BE 17

IV. THE ORIGIN OF THE PLANETS 26

V. THE SEVEN GREAT PLANETS 38

VI. THE MOVEMENTS OF THE PLANETS 46

VII. HOW THE INFERIOR PLANETS SEEM TO MOVE 56

VIII. HOW THE SUPERIOR PLANETS SEEM TO MOVE 65

IX. THE PATH OF THE PLANETS 71

X. MERCURY--WHEN AND WHERE TO FIND MERCURY--DISTANCE AND BRIGHTNESS--MERCURY’S SIZE AND THE CONSEQUENCES OF IT-- WHAT THE SUN DOES FOR MERCURY--TRANSITS 93

XI. VENUS--WHEN AND WHERE TO SEE VENUS--DISTANCE AND BRILLIANCY--VENUS’S LIKENESS TO THE EARTH--ATMOSPHERE, DAY AND NIGHT, AND SEASONS--TRANSITS 122

XII. MARS--HOW TO IDENTIFY MARS--WHEN AND WHERE MARS MAY BE SEEN--SIZE, ATMOSPHERE, AND TEMPERATURE--DISTANCE AND BRILLIANCY--DAY AND NIGHT, AND SEASONS--SURFACE ASPECTS--SATELLITES 151

XIII. JUPITER--PLACE IN THE SKY--DISTANCE, LIGHT, AND HEAT-- DAY AND NIGHT, SEASONS, AND ATMOSPHERE--SURFACE FEATURES--SYSTEM OF SATELLITES 183

XIV. SATURN--AROUND ONE CIRCUIT OF THE SKIES WITH SATURN-- DISTANCE AND SIZE--SURFACE ASPECTS AND CONSTITUTION-- DAY AND NIGHT--THE RINGS AND MOONS OF SATURN--SEASONS 206

XV. URANUS 225

XVI. NEPTUNE 234

XVII. THE LITTLE PLANETS, OR THE ASTEROIDS 244

XVIII. CONCLUSION 258

SYMBOLS USED IN ALMANACS 267

INDEX 269

ILLUSTRATIONS

A WHIRLING SPIRAL NEBULA, TYPICAL OF THAT FROM WHICH THE SUN AND PLANETS WERE PROBABLY EVOLVED _Frontispiece_

MAP SHOWING THE CONSTELLATIONS OF THE ZODIAC AND THE LINE OF THE ECLIPTIC RUNNING THROUGH THEM _Facing p._ 76

THE LOVELY CRESCENT THAT VENUS SHOWS WHEN TO OUR VIEW SHE IS AT HER GREATEST BRILLIANCY " 136

RELATIVE APPARENT SIZE OF VENUS AT DIFFERENT PHASES OF ILLUMINATION _Page_ 137

THE TWO PHASES OF MARS _Facing p._ 152

MARS: DIFFERENCE IN ITS APPARENT SIZE AT ITS NEAREST, MIDDLE, AND FARTHEST DISTANCE FROM THE EARTH _Page_ 169

JUPITER, THE MAMMOTH MEMBER OF THE SOLAR FAMILY-- LARGER THAN ALL THE OTHER PLANETS PUT TOGETHER _Facing p._ 184

SATURN AND ITS RINGS " 220

THE

WAYS OF THE PLANETS

I

ON MAKING ACQUAINTANCE WITH THE PLANETS

It is sought in the following pages to give a simple account of what may now be said to be known of the character of the planets, and to describe with as little technicality as possible their movements and aspects and relations. An endeavor is made to impart concerning each one of them not, surely, profound learning, but just a good, every-day, practical notion, so that the mere name will call up a definite object, with its own attributes, appearance, and behavior, entirely distinct from any other planet or from any other object in the skies.

An endeavor is made also to so simplify and direct the observation that any one, after a little practice, will know almost without hesitation, on seeing a planet in the sky, that it is a planet, and not a fixed star, and exactly what planet it is. The situation and aspect of it will then as quickly and clearly pronounce it to be the individual planet that it is as the sight of a person of one’s acquaintance proclaims him to be that person, and no other. The very name of Venus, for example, and still more the sight of Venus, will call up a conception of Venus, with the particular atmosphere and light and movements and wanderings which make her what she is. On looking at her the observer will at once know why she occupies the special position in the sky in which he sees her, why she is not so bright as she was when she was last in view, or is so much brighter than she was then, about how long she is likely to remain where she is, and when she goes what will become of her.

For far off and truly mysterious as the planets are, it still is with them as with most other objects in nature: a very little knowledge of their aspects and their ways begets a sense about them that makes the most casual observation of them interesting and, as far as it goes, intelligent. The slightest glance at them betrays some shape, or position, or light, or other quality, which at once makes recognition of them unmistakable. They disclose themselves oftentimes, one can scarcely say how, just as persons with whom we are intimate do by some half-caught outline, motion, or posture; or just as the trees do to an observer who knows, for example, an oak-tree from an elm, whether they are covered with their own peculiar verdure, or whether they stand with bare branches stretched out and colored in their own peculiar way.

This instant recognition of the planets is, of course, not to be had by simply reading about them. Such practical familiarity with them is attained only by seeking them out over and over again and looking at them with attention, with eagerness, and with all one’s faculty. With them, as with other natural objects, it requires observation truly to know them. But then, observation, when one gets a little started in it, is a great deal more interesting, a great deal more absorbing, than any reading about them can ever be. It is also a very easy thing to begin, for, after all, it is not much more than looking and then looking again. In doing this one can hardly tell just when an object ceases to be strange, and then becomes familiar, and finally is so much a part of every-day knowledge that one knows it at a glance. But this is what happens in the case of any natural object when we observe it often and with true attention.

In the case of the planets, if one is interested at all, every stage in the cultivation of such an acquaintance is full of pleasure. Even to one who regards them only as a part of the general aspect of the sky, they are the most beautiful objects in it and always the first to attract special attention. Nine times out of ten, when any one asks what a certain star is, it proves to be one of the planets. When one of them is visible a person can hardly glance at the heavens without noticing it, even if he does not stop to think about it. But if he does stop to think about it and notices that it is far larger than any star he has noted before, that it hangs low in the western sky early in the evening, and shines with a brilliant silvery light, and if he then learns that it is Venus, will he not always have a pleasant thrill of recognition when he again sees such a star in such a position and knows it as Venus, among the planets as surpassing in beauty as the goddess of that name was among the immortals? Or, if in the east, at the same time in the evening, he sees a brilliant, solid-looking, unblinking star shining with a white light, but pinkish white, not silvery, and finds it to be Jupiter, will not such a star in such a situation be to him ever after a pleasant acquaintance that he can call by name? Not that Jupiter and Venus are always in these positions, or shine in just this way at all times. These are their places and aspects at certain times, frequently recurring, and at such times always unmistakably distinguish them.

It is, then, merely the matter of a little more and yet a little more observation, in order to come to know any one of the visible planets in all its varying aspects and situations. Of course, at the start some guidance is necessary, but only a little; and that little, if it is of the right sort, should not be irksome. To provide such guidance is one of the aims of this book. That is, indeed, its main aim.

But in addition to what, as a help in observation, it may find to say regarding the appearance and movements of the planets, it will endeavor to give also ample information concerning their character and constitution.

It is hoped that this may be done without weighting the narrative with figures, though some of the peculiarities of the planets must be expressed by means of numbers. Certainly no mathematical problems will be presented. But it will be profitable to remember that every one of the intimate things we know about the planets has come to us through the long and laborious mathematical work of astronomers. To them we owe the extinguishable debt that we owe to all special workers who put us in possession of the facts that interpret life to us.

For the astrology and poetry and romance of the planets one must go elsewhere. Nearly every book on the subject of the planets--and there are many of them--has some information about these things; and properly, too, for every genuine emotion and every real fancy has its value. But neither curious lore of the planets nor the sentiment and emotion they have produced in others is what the author of this book is striving to set forth. It is something much more vital than this. What we wish to contemplate here are the plain facts, the knowledge of which enlivens and enriches one’s mind and nature. If the contemplation of them kindles one’s fancy or excites one’s emotions, these results at least will not be second-hand. If the bare facts, simply and plainly told, and the view of the planets themselves as they wander through their courses in the sky, do not awaken one’s understanding and imagination, no amount of poetry or romance that other people have built up around the planets will arouse anything more than a factitious interest in them. It is when our own faculties are at work and our own fancy plays over a subject that we become genuinely and lastingly interested in it.

The facts themselves are in the main quite simple, and will not be given here as anything else than that. They have been fairly wrested from that mysterious thing called space by the mighty power of mind and unceasing labor. Our knowledge of them is due to long nights of watching and long days of calculating; to long and careful testing and considering of theories, only to find that something else must be tried; to courage to begin all over again, to sudden inspirations, and sometimes to those lucky discoveries that seem almost like miracles.

The subject of the planets has in some respects a greater interest even than that of the stars, because we know, after all, more about them. We sometimes have a feeling, though, that we know more of the stars, although the stars are so much farther off. Why we have this feeling it is easy to explain. Knowing them to be so far removed from us, we really approach the stars with a different expectation. The few things that we have learned about them have in themselves such a magnitude that it makes them seem a greater body of knowledge than they truly are. The stars are indeed so far away, and what we know of them has to be expressed in such large terms, that the mind does not demand in that information the minute exactness that it seeks for in the case of nearer objects.

In the case of the stars, we seek mainly to know their distances, the direction of their motions, the speed with which they travel, and their probable connection with each other. The fact that in computing the distance of a single star, many trillions of miles away, the result may be a little less than exact does not keep us from learning what ones are sufficiently near for their distances to be measured at all and what ones are immeasurably remote. Whether they travel at the rate of exactly three or three hundred miles a second, we can learn that some are traveling at somewhat the same rate of speed as our sun travels, and some incredibly faster; that certain groups are going in one direction and certain groups in another; that some are approaching us and some are receding from us. And thus we can classify them and learn the significance of these facts, and, little by little, gain a definite understanding of the construction and meaning of the entire universe. Their very remoteness gives a certain compactness to the information we have about the stars, by making it necessary to generalize more than we would if they were near enough to yield more details; and we are in a way satisfied with this more general sort of knowledge of them.

But the very fact of our knowing so much about the planets extends our curiosity concerning them and makes us feel that we ought to know more. The mind is provoked into more minute speculations about them, and we demand more exactness of information and knowledge of a more specific or intimate sort than would satisfy us in regard to the stars. Atmosphere, habitability, exact size, seasons, and day and night, are the kind of things we most seek to know in reference to the planets. These are such definite things that conclusions concerning them are subject to close criticism, and differences of opinion in regard to them thus sometimes occur which tend to give one a more or less confused notion of what is really known. As a matter of fact, our information about the planets is much fuller than our knowledge of the stars, as we would naturally expect it to be. Much of what we seek to know about the stars has long been common knowledge about the planets.

II

OUR RELATION TO THE PLANETS

To know about the planets is to know about ourselves. The earth is one of them. Whatever their origin, the earth’s is the same. It and they are formed from the same nebula, controlled by the same central body, subject to the same laws, and destined for the same fate in the end. In this, the stars and the planets are not alike. They all shine upon us with the same sweet friendliness, and commonly we make no difference between them in our feeling for them. But the stars are bright and beautiful acquaintances living far away in their own domain. The planets are members of our own family, bone of our bone and flesh of our flesh, living comparatively near to us, within the domain of our common source of life, the sun.

One evening last autumn I was coming up Broadway, New York, with a friend, when we encountered at Union Square a man with a six-inch telescope directed toward the eastern sky. He was soliciting those who passed to stop and look at Mars and Saturn. Both of these planets were then very bright. They were also fairly near together, and so low in the east that one could scarcely help seeing them. But the people passed back and forth with hardly so much as a glance at the man and his telescope, and for the most part never even raised their eyes to the sky with a passing curiosity to see what it might be that he wanted to show them. My friend and I stopped and took each a view first of Mars and then of Saturn. While we were looking at the planets, a few of the passers-by began to loiter about, half smiling at us for so playing in public, slightly curious to see how we were faring at it, but for the most part apparently indifferent to what we were seeing. We had a fine view of Saturn lightly resting in his nest of rings, and an equally good view of the comical “eye” of Mars.

After we had finished, one or two others, evidently prompted by our example, followed us at the telescope. One or two inquired of us what the stars were that had so interested us, and one, pointing to Mars, wanted to know if it was Venus. As the crowd grew larger a few more ventured to take a look, much as they might venture to take their chance at hitting the bull’s-eye in some shooting-gallery. With the telescope pointed at Saturn, the man droningly chanted: “This planet is 887,000,000 miles from the sun. The ring you see is 170,000 miles in diameter,” and so on. These, to be sure, were the facts--and most marvelous facts, too--but without much meaning to one who knows nothing much about the planets; and the manner of their recital certainly did not make them alluring. I could not myself help feeling that the people there were missing a valuable opportunity, and that it would be only fair to them for some one fairly to cry out: “Come here and look at this planet. It is different from anything else you have ever seen or ever will see. It was at one time a part of the same nebulous mass that we were a part of. It is in the same system of worlds with us. It was formed in the same way that this world was formed. It is in itself the most wonderful thing you ever saw, and it is bound, as we are, to the sun by the ever-drawing tie of gravitation. The very position of our own world in space is more or less influenced by it. If anything should happen to it, it might be a serious matter to us.”

For it is true that we are thus closely bound to the planets. The family tie among us is of far more force and significance than in any ordinary case of common origin. Human family ties wear, as we know, often into the merest threads, or even become no ties at all. But that between the earth and the planets remains apparently as close and strong as ever it was. The law of gravity, under which the earth draws toward its center every atom of matter surrounding it, and thus holds together all the atoms composing it, is not solely terrestrial in its application. It is probably universal. It certainly applies to every part of our little family of worlds. Every particle in the solar system attracts toward it every other particle in that system with a force determined by its mass and its distance. The sun, by reason of its immense size, compels the earth and all the other planets forever to circle around it. But the planets themselves have just as much power of attraction as the sun, atom for atom.

Thus, while the sun controls the motions of all of them, each pulls at the other, and, according to its power, determines how much the path of each shall vary from the course around the sun it otherwise would make. In the case of the smaller planets, this gravitational influence is, of course, very slight, and so subtle that we here on earth are not even conscious of it. But it is, nevertheless, real and continuous. It is greatest between the two largest planets, Jupiter and Saturn; but it was enough in the case of Uranus and Neptune to lead, by its mere manifestation on the earth, to the discovery of Neptune, the farthest planet.

Being thus of the same origin with the planets, having the same life history, being bound to them in space by a tie that is perhaps eternal, how can we fail to have the most intimate interest in their nature and all that concerns them?

But in addition to their close relationship to us there is, to make them of peculiar interest, the fact that, after the sun and the moon, they are for our eyes the most splendid objects in all the brilliant panorama of the sky. Such of them as we can see at all with the naked eye are most of the time much brighter than any first-magnitude star. As they wander from constellation to constellation the soft light of their placid faces gives a beauty and variety to the spectacle that endears them to us, and at the same time enhances by contrast their own charm and that of the glittering, unchanging stars.

There is nothing that gives one such a sense of sweet familiarity with the heavens as a really recognizing acquaintance with the planets. They are not, like the stars, associated with particular seasons. They come sometimes with the gay company of stars that dance their way across the cold winter skies, and sometimes with those that shine during the soft summer nights. Often in the spring and autumn we see some one of them before the sun is fairly down, and, before the light of an ordinary star can yet be seen, hanging in lone brilliancy as the evening star; and often an early riser has the reward of seeing one as a morning star glowing almost in the rays of the rising sun. Thus they are, one and another, with us at all times and seasons, and it accords with the fact of the relation being a family one that we have in their coming and going a sense of frequency and informality which we cannot have in the more regular and seasonal coming and going of the stars.

III

WHAT THE PLANETS ARE, AND WHAT THEY APPEAR TO BE

The planets are dark, opaque bodies which revolve at varying distances and at varying rates of speed in orbits more or less circular around the sun as a center. They have no light of their own, as the stars have, but shine wholly by reflected light received from the sun, which itself is a star. The amount of light they show to us depends upon their size, their distance, and their power of reflecting the light they receive.

In comparison with the stars, the planets are very near to us. Our sun, which is in constitution a star, but very widely separated from any other star in the universe, holds all his family of planets by the tether of gravitation, and so keeps them circling about him in a very small space, as astronomical space is measured. To all of the planets except Mercury, we ourselves are nearer than the sun is. To be sure, this distance between us and the planets, as measured by any terrestrial measure, is not exactly small. It is only by comparison that we can be said to have anything like a cozy relation to them. For merely earthly affairs we use terrestrial measures. In solar affairs we measure by an astronomical unit, which is the sun’s distance from the earth, ninety-three millions of miles. When we say a planet’s distance from the sun is thirty astronomical units, we mean it is thirty times farther than the earth is from the sun.