Secrets of the stars

Front matter

'I STARS

South

MAP OF THE STARS, 12 P.M., APRIL

Preface

Emerson once said: "If the stars should appear one night in a thousand years, how would men believe and adore, and preserve for many generations the remembrance of the city of God which had been shown!"

But the stars are so common; we may look at them on every clear night, so the most of us pay them small heed. In all ages, however, there have been observing and thoughtful ones who have sought to read in the stars the answers to various questions about the Universe, until at the present time the world is dotted with observatories equipped with a great variety of instruments for studying the celestial bodies, and astronomy has come to be regarded as the golden chain between the Earth and the heavens. Indeed, so closely does it bind the two, that the one is mapped by means of the other. By the wise guidance of the stars, fleets and caravans are sent over wastes of sea and sand which would otherwise be trackless and impassable. By the vi PREFACE

stars are our clocks and watches timed, our lands surveyed, and the boundaries of our nations reckoned. In their twinkling faces are recorded not only the past and future of the comparatively small mud-ball which is our dwelling-place, but therein is also revealed the marvelous creation of the whole vast Universe. There is scarcely a science or an industrial activity of any kind that has not depended upon the revelations of starlight for its advancement. In truth, there is not a civilized person anywhere in the whole wide world whose life is not rendered more worth the living, or whose comfort is not affected, at least indirectly, by the work of astronomers and others who are applying the principles of this science to the practical affairs of daily life.

And yet so used are we to taking everything for granted, that, to most of us, the rising and setting of the Sun, the marvelous phases of the Moon, and the march of the glittering star hosts across the sky excites no wonder and inspires no awe in our breasts. We are dead to the wondrous truths, more glorious than any tale of mystery or romance, that are spread continually before our eyes in the great book of the sky — God's

PREFACE vii

own clear page. Our painted American savages, the Arab in the desert, the simple, ignorant children of the race on the banks of the Nile, the wild men on the islands of the sea, have all been more observant than we as a general people are to-day! It is impossible to read the literature of modern times without stumbling upon references to star legends which have been handed down since time immemorial. They are the efforts of primitive man to understand and explain the wonders which they saw all about them. They constitute the poetry of the sky, which we shall certainly find delightful, even if our minds are so constituted that the drier, more scientific facts of astronomy do not appeal to us. Let us, then, rouse ourselves and at least make friends with the mysterious giant figures that people the blue dome of the sky! Once we learn to look upon these and to recognize them as the faces of our friends, we can but be interested in the countless things they have to tell us.

Nor is any apparatus really needed for our study of the stars, save that which Nature supplies— a good pair of sharp eyes. Remember, telescopes, while they may add greatly to the inviii PREFACE

terest, were invented no longer than four hundred years ago, and all the planets and most of the stars that are now known had already been discovered and named. Likewise, too, countless of the most unfathomable mysteries of the skies have been discovered by no other aid than a clear eye and an inquiring mind. Have you these? Join hands, then, my readers, and let us go prospecting for the secrets of the vast suns of space — the boundless stars — which populate "the infinite meadows of Heaven."

The author gratefully acknowledges her indebtedness to the many published works on astronomy which are available, both for the beginner and advanced student in this fascinating subject. Authorities and works are cited in the text, but special thanks are due to Messrs. Cassell & Co. Ltd. for courteous permission to quote from Ball's "Starland."

I. N. McF.

Springdale, Ark.

Contents

PAGE

The Sun, to Us the Greatest Star of All . . 21

Mother Earth, a Chip from the Sun-Star . . 44

II The Sun, To Us The Greatest Star Of All

The early peoples of the world worshiped the Sun as the Lord of Day, the Fountain of Light, and the Bringer of all things good. But they were at a loss to account for him:

Whence are thy beams, O Sun, thy everlasting light?

Thou comest forth in thy awful beauty; the stars hide themselves in the sky; the moon, cold and pale, sinks in the western wave; but thou thyself movest alone.

— Ossian

And whither? No one knew that the Earth was round, when Ossian wrote. They thought it was a great flat plain, extending in every direction. It seemed that the Sun daily traversed the sky only to plunge into the western sea ! Indeed, there were those who fancied they heard the dreadful hissing noise when the glowing, red-hot orb dropped into the Atlantic! But here was the difficulty: how did it get around

to the East, and rise fresh and hot as ever the next morning? Surely the plunge into the water should have quenched it! Some said that we had an entirely new sun each morning. The business of making the suns was supposed to be in the hands of the gods; all day and all night they worked with Titanic energy, and each succeeding morning saw a new orb launched forth on its journey.

This, however, seemed a waste of suns, and presently a new theory was evolved: Vulcan, the God of Labor, had the matter in charge. When the Sun dropped into the sea in the West, it was his business to rescue it and row it around the northern route to the East. Some of those who sat up all night to watch for indications of the progress of this journey, fancied they could trace the light of the glorious cargo along the northern horizon. Besides how else could one account for the long midsummer twilight? A tedious night's voyage poor old Vulcan had of it! Nor was there even a moment's respite. As soon as he reached the East, he must launch the Sun with terrific energy, so that it would not flag nor falter all the day, and then paddle back the way he had come, with unceasing industry, so as to be ready to catch the Sun in the evening, and be off again on his unending task!

Time has settled this problem, as well as that other great phenomenon, the change of seasons, which was even harder for the ancients to solve. Gradually people have come to understand these "miracles," and to take them as a matter of course. No longer do we feel awed when darkness settles down, and we have absolutely no fear concerning the return of day; neither are we troubled over the unending struggle between summer and winter. Likewise, too, we accept all the other beneficences of the Sun. But it is well for us to pause now and consider that without the Sun, life on the Earth would be impossible. To him we owe light, heat, power, food, water, in short, everything that we have, even the Earth itself. Perhaps we shall understand this latter statement better by illustration:

Draw down the shades, light the candles^ and let us consider it while we have tea and muffins in the cozy radiance beside the fireplace. How cheerful the fire's ruddy glow!

Do you know that it is stored-up sunshine? "Why," you exclaim, "the fire is only coal." Yes, but what is coal? It is the fossil remains of giant trees, huge ferns, and hixuriant grasses and mosses which once grew by reason of the warm sunshine and soil-water. These muffins, too, were made from wheat grown by the Sun. Even the very power that ground the flour came from the Sun.

No matter whether ground in a mill turned by wind or by steam, the Sun did the work. For the Sun furnishes both wind and water. All the air currents on our earth are due to the Sun in this wise : great tracts of land are warmed by the pleasant sunbeams. The air, in turn, is heated and rushes upward, while the cooler air slips in to fill its place. To do this, the air, of course, moves across the country. It is wind. And it is the Sun that has started it. All the water we use comes from the clouds, either as snow or rain. Even the water we have here in our teapot was floating far overhead, only a little while ago. Before that, perchance, it was just some tiny drops of water in the ocean. The Sun poured down his warm beams upon them, the drops turned to vapor, and climbed into the sky, there to unite in the cooler atmosphere with other rising drops and thus form a cloud, which floated our way. By and by the wind came rushing along, the vapor cooled still more and changed back to drops again, falling as rain, until1 presently the little cloud wept itself away. The drops seeped down deep into the soil, and at length found their way into the underground vein which empties into our well. Our tea is a product of sunshine. It came over sea in a ship built and run by sunshine. Look anywhere you may about the room: you can see nothing which does not owe its all to sunshine. Sunshine even grew and bleached this lovely white lunch cloth, and gave the pretty colors to your dresses.

Countless, indeed, are the marvels connected with the Sun, but of them all none is more astounding than its vast distance from us and its enormous size. Astronomers have determined that 93,000,000 miles of space stretches between us and the Lord of Day. But do you have any idea of this vast distance? Suppose you try to count 93,000,000. Professor Ball says the best way will be to let the clock do this: "How long will the clock have to tick before it has made as many ticks as there are miles between the Earth and the Sun? Every minute the clock, of course, makes sixty ticks, and in twenty-four hours the total number will reach 86,400. By dividing this into 93,000,000 you will find that more than 1,076 days, or nearly three years, will be required for the clock to perform the task."

Again, here is another illustration: It is nearly 25,000 miles round the world. The journey can be accomplished in sixty days. Traveling at this rate, one man' might make 4,000 journeys around the world while another was covering the same distance between the Earth and the Sun. No man, of course, could accomplish this feat, even if such a journey were possible. He would be 600 years old when he reached his destination, even if he set out when a mere babe. As another instance, suppose that a train had started for the Sun, during the time of Cromwell, traveling at the rate of forty miles an hour, and stopping neither day nor night, it would not yet have reached its destination. It would require 265 years to complete the journey, and no man who started on the train could hope to be in at the finish. The journey must be ended by his great-great grandchildren.

No less amazing than the Sun's distance is his size. Approximately his diameter is 866,- 000 miles. This means that 109 globes the size of our Earth, set side by side across the face of the Sun, would not quite cover it. Again, comparing the vohime of the Sun with that of the Earth, Professor Gregory gives the following illustration: "If we had a contract to build up this stupendous bulk, and were to deliver a load of the same size as the Earth every hour, the order could not be completed working night and day for 150 years."

Though the Sun is vastly greater than the Earth in volume, it weighs only 330,000 times as much. Thus the density of the Earth is about four times that of the Sun. The reason of this is that the Earth is a solid globe, while the Sun is a great glowing ball of incandescent gas. Nor is the force of gravity at the Sun's surface so great as his immense mass would seem to indicate : it is only twenty-seven and two-thirds times as great as gravity at the surface of the Earth. A body would fall vertically 444 feet in tfhe first second. An athlete attempting stunts on the Sun would find his movements hampered by a bodily weight of 4,000 pounds. His running high jump, if possible at all, would not be over three inches. On the Sun, the pendulum of an ordinary clock would swing so rapidly that its movements could scarcely be counted.

The Sun is so constantly before us that we do not often stop to consider the immense amount of energy it is pouring forth every second. Astronomers have determined that the Sun is immensely hotter than a powerful electric arc-light which melts all known substances, and scientists have puzzled not a little to account for the work which this heat does in the vast regions of space; for only the two-billionth part of it reaches our Earth and is used to support the life of creatures here. On its surface the solar heat has been estimated at 18,000° Fahrenheit. How shall we realize this enormous heat? From even one square meter of this glowing surface enough heat is generated to supply 100,000 horse-power, continuously night and day. Further than this, Professor Young says: "If we could build up a solid column of ice from the Earth to the Sun two miles and a quarter in diameter, spanning the inconceivable abyss of 93,000,000 miles, and if the Sun should concentrate his power upon it, it would dissolve and melt, not in an hour, not in a minute, but in a single second ; one swing of the pendulum and it would be water, seven more and it would be dissipated in vapor." Were the Sun as near to us as the Moon, his powerful rays would not only quickly turn all the ocean to vapor, but the solid Earth itself would be speedily melted.

How do astronomers know all this? By experiments with burning-glasses, mirrors, and arc-lights. The Sun's heat is determined by opposing it to an electric arc and measuring the heat which both produce at different distances. You may perhaps have started a camp-fire by means of the Sun's rays through a burning-glass ; or perchance you may have seen a cannon covered by a burning glass in such a way that the Sun's rays touched it off at the noon hour. Sometimes one discovers black spots on leaves that have been caused by the drops of dew acting as little burning-glasses and concentrating the Sun's rays. It is an interesting experiment to make a lens out of ice, and burn a piece of paper by means of Sun rays which have passed through such a cold body. A mirror from an old automobile reflector is ideal for concentrating the Sun's rays, as its curved surface brings the beams to a direct focus. If the mirror is large enough an iron nail will burn like a match in the heat generated.

From experiments with large mirrors, we know that the heat of the Sun must be capable of melting all known metals, and glass and porcelain ; for the Sun must be even hotter than the focus of the largest mirror we can construct, since a wall exposed to a blazing fire cannot be hotter than the fire itself. "With the Sun in the zenith," says Professor Todd, "his heat is powerful enough to melt annually a layer of ice on the earth nearly 200 feet in thickness."

The time is coming when the world's supply of bottled sunshine — wood and coal — will have disappeared; so that, within a century or two, new ways of furnishing heat and power must be devised, or the human race will perish of cold and hunger. Fortunately electricity and windpower are at hand, but greater than either of these two sources is the unlimited might of the sea tides, which men have sought in vain to harness; and the direct heat of the Sun itself. Already solar motors have been invented — such as those by John Ericsson, the great Swedish engineer who built the Monitor, by Mouchot, Schuman, and others; the principal features to make them a success — cheapness and practicality— have not, however, been arrived at. Perhaps the key to these may be in the hands of some one who reads these words! Certain it is that the dependable solar motor is bound to come. Think what such a source of cheap power will do. Above all, it will make valuable countless acres of desert land, providing homes for thousands on profitable irrigated tracts. Any place in the tropics where the sun shines practically speaking throughout the year, and where ordinary fuel is very expensive, offers excellent opportunity for the solar motor. A small solar plant on the roof of the modern apartment house will not only light and heat it at the least possible cost, but it will cook the meals of the inmates, run the sewing-machine and the vacuum cleaner, and in short furnish power wherever power is needed.

One of the great mysteries in regard to the Sun's heat is its constancy. It shines to-day just as intensely as it did as far back as man has any record. How is this enormous heat kept up ? Certainly it is not by the combustion of carbon. Had the Sun been composed of coal it must have burned out in less than five thousand years. And apparently the sun is in his prime! Scientists have decided that the only real plausible theory for the Sun's heat is that he is contracting upon himself. If this be true, he must have been vastly larger in the remote past, just as in the far distant future he will be very much reduced in size. It has been estimated that the burning of gases in a contraction of his diameter of six miles per century would fully account for his present heat. At this rate it has been calculated that the Sun will shrink to one-half of its present diameter in five million years. While certain types of life would disappear, enough heat and light would still be emitted for another five million years. But, after that period the glacial epoch would again dawn, and presently the Sun and his retinue would swing silently through space as cold, inert lumps of matter. That there are many types of such dead suns in the heavens is a fact well-known to astronomers.

No less remarkable than the heat of the Sun is his brightness. The intensity of sunlight, as it is called, has been calculated as 190,000 times that of a candle, 146 times that of a calcium light, and nearly four times brighter than the brightest electric arc-light; 600,000 full moons would be needed to equal the light of the Sun. Absorption by the Sun's own atmosphere not only reduces the amount of light which we receive, but changes its character. According to Langley, were it not for its atmosphere, the Sun would shine two or three times brighter than it now does, and with the bluish color of the arc-light.

Of course no one can look directly at the Sun, but by observing him with the aid of a telescope, or even through a darkened glass, we behold first a disc of yellow light — the photosphere, astronomers term it. Looking at this carefulry, we may note that the brilliant surface is marked with dark spots. These are called sun-spots. But they are not permanent features of the Sun, like the mountains and craters are of the Moon. They are only temporary markings, here to-day perhaps and gone to-morrow. Sometimes the spots close up within a few minutes and fresh ones open elsewhere. Again the whole surface seemes mottled over in a curious way.

What does it all mean? Galileo and Scheiner, the astronomers who first discovered this phenomenon, could scarcely credit their senses. Surely the sun was too dazzlingly perfect to show defects, such as the sunspots seemed to be! At length, however, it was determined that the photosphere was merely the brilliant envelope or light-sphere of the sun, and that the dark spots were in truth great rents or holes in the glowing envelope, through which the core of the Sun was seen. Shortly, by means of the sunspots, astronomers were assured that the Sun, like the Earth, rotates on its axis. But "the day" of the Sun is twenty-five and onequarter times longer than that of our planet. Another interesting fact is that the sunspots increase and decrease about every eleven years. Incredible as it may seem, the discovery of this solar cycle, as the increase and decrease of the sunspots is called, was made by a mere amateur in astronomy, whose only instrument was a hand telescope! In 1826, a German apothecary named Schwabe, who had been interesting himself in the heavens, commenced to count the number of spots on the sun as seen from day to day. After about twenty years had passed, he began to feel sure that there was a periodic increase and decrease of the sunspots, and by 1851 he had triumphantly proved the existence of the solar cycle — an important fact that had escaped the observation of all the noted astronomers. Today it is known that when the sunspots are most numerous the aurora borealis is the most frequent and vivid ; at this time, too, the presence of magnetic disturbances is noted in the fluctuations of the delicately mounted magnetic needles at Greenwich and in various other observatories. The largest sunspot on record covered about one thirty-fifth of the whole sun. This occurred in

1858. In February, 1892, another huge spot appeared, some 92,000 miles in length and 62, 000 miles wide. Closely connected with this huge gap in the photosphere were a number of smaller spots, in all making a rent that seventy bodies of the diameter of our Earth would have, been required to patch.

Besides the sunspots, the telescope reveals another decidedly interesting feature on the bright surface of the Sun. This is the appearance of brighter streaks or ridges, called the faculce, and wholly as irresponsible and notionate as the sunspots whose neighborhood they seem to frequent. Often it is impossible to sketch their form, so quickly do they appear and disappear. Some astronomers believe them to be elevated peaks of luminous matter extending thousands of miles above the gaseous plain. Some are evidently composed of clouds of incandescent calcium, an element which exists freely in the Sun. As a rule, sunspots are usually confined to the two zones above and below the solar equator, while the f aculse are often found well distributed over the Sun's surface, excepting in the "polar" regions.

For a large part of our knowledge of the Sun we have to thank the Moon. Occasionally this beneficent body gets between us and the Sun, producing an eclipse. Then, of course, we do not see the Sun, but we see something for the moment infinitely more interesting and beautiful. This is the wondrous spectacle of the corona and the prominences. The corona is the marvel of the astronomical world. Unfortunately it can be seen clearly only about seventy times in a century, though there is no doubt but that it is a regular part of the Sun — the third and final solar envelope, a halo glowing with a soft radiant silvery light. "Its shape," says Macpherson, "varies in sympathy with the eleven-year period, and it seems closely connected with electricity and magnetism. It streams out from the sun for millions of miles, becoming more and more rarified until it gradually fades into the ether of space."

In spite of its infrequency, various photographs of the corona have been taken. For it is possible for astronomers to figure when eclipses are due, the regions of their greatest visibility, and the length of their duration.

These dates are regularly published in the Nautical Almanacs, used by the English, French, German, and American governments, and naturally, at each occurrence, even though they must journey half-way around the world, representatives from every observatory are on hand, with a very definite idea of just what they want to accomplish in the few seconds, or perhaps moments, of the exhibition. Very carefully, you may be sure, are all the details rehearsed beforehand, time and again, that there may be the most accurate observation. In 1955 (Luzon) and 1973 (Sahara) will be two great total eclipses of seven and one-half minutes' duration, the longest for a thousand years.

The prominences, or red flames, which were first to be seen only at eclipse dates, are now, happily, to be observed almost any time. But they are not to be seen through even the most powerful of telescopes. You must call into service one of those ingenious oft-mentioned contrivances called a spectroscope — an instrument which is no more nor less than a special kind of a glass prism. By this means the prominences are shown to be tongues of glowing fire shot forth with tremendous power from the chromosphere — an irregular rose-tinted fringe, varying from five to ten thousand miles in width, which completely encircles the sun, forming its second envelope. Many of these prominences are of enormous height, ranging from an average of 25,000 miles — about the circumference of the Earth — to 350,000 miles, nearly half of the Sun's diameter. Like the sunspots, the prominences increase and decrease every eleven years. Their variety of color shows them to be the gaseous vapor of various well-known metals, chiefly calcium (fiery-red) and iron (dark colored). Dairy photographs of the Sun's prominences are taken in various observatories, but especially is this a feature at the Carnegie Solar Observatory in California. Two forms of prominences are known: brilliant eruptive jets and cloud-like wide-spreading shapes.

Few people who look up at the arc-lights which illuminate most of our city streets give any thought to how interesting and mysterious that light is. We know that it is the nearest thing possible to direct sunlight; in truth the arc-light is really the Sun's own imitation of himself. Thousands of years ago the Sun's energy was packed deep in the coal mines of the earth. To-day man has unearthed this treasure and turned it into carbon rods, which have again been led to produce the light and heat which the Sun stored up eons ago. By the aid of the Sun's own bottled energy, miraculous as it may seem, we have measured his heat. Through the medium of the multi-useful spectroscope we have watched various substances burn in the arc until their gaseous color is familiar on sight. By applying this same knowledge to the colors observed in the Sun's spectrum, we have been able to determine of what the Sun is made. So far about forty elements are known to exist in the Sun. Strangely enough, too, some elements were known in the day's bright orb long before they were found on our sphere: helium and coronium are two of these. Iron, hydrogen, calcium, nickel, and sodium are the most abundant of the Sun's elements.

Of what lies below the Sun's photosphere, in the center of his mighty orb, we can form no conception. According to one astronomer, "The pressure within the Sun is equally unconceivable. A cannon ball weighing 100 pounds on earth would weigh 2,700 pounds on the Sun. Thus a mighty conflict goes on unceasingly between imprisoned and expanding gases and vapors struggling to burst out, and massive pressures holding them down."

This, then, is our Sun, the center of the solar system, the great Fountain of Light, to which we on Earth owe all that we have. Besides our Earth there are seven planets of considerable size, and a whole host of insignificant little ones which depend upon the Sun. They all revolve about him, and derive their light and heat from his beams. In a good many ways these planets resemble the Earth. One of them, Venus, is about the same size. Mercury and Mars are much smaller, but Jupiter, Saturn, Uranus, and Neptune are a great deal larger. The nearest of these is millions of miles away, and naturally but little is known concerning them, though people have known of their existence for ages. The ancients named the days of the week from these seven celestial bodies.

You will perhaps like to make a drawing of our planetary system, in order to give yourself an idea of how it appears.

In order to draw the inner part of the solar system to scale, take a piece of blank paper at least ten inches square. In the center set up one leg of a drawing compass, open the other leg one inch, and describe a circle. The central dot, which can be enlarged is, of course, the Sun. The first orbit thus described is that of Mercury, and can be so marked, with "88 days" set down for the year, or time to complete the circle. The compass should next be opened one and threequarters inches, from the center, and this circle will represent the orbit of Venus, 225 days. The third circle with a radius of two and one-half inches is that of our own Earth, 365 days. The fourth circle, with a radius of four inches, is Mars, 687 days. This completes the inner solar system. A very much larger piece of paper would be required to describe the orbits of the four outer planets.