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LITTLE BLUE BOOK NO. 895 Edited by E. Haldeman-Julius

Astronomy for Beginners

Hereward Carrington, Ph.D.

Author of the following Little Blue Books: No. 679, “Chemistry for Beginners;” No. 491, “Psychology for Beginners;” No. 419, “Life: Its Origin and Nature;” No. 524, “Death and Its Problems;” No. 493, “New Discoveries in Science;” No. 409, “Great Men of Science;” etc., etc....

HALDEMAN-JULIUS COMPANY GIRARD, KANSAS

Copyright, 1925, Haldeman-Julius Company

PRINTED IN THE UNITED STATES OF AMERICA

CONTENTS.

Page

Introductory 5

Astrology 7

The Solar System 8

The Sun 9

Mercury 11

Venus 12

The Earth 13

Mars 13

Jupiter 16

Saturn 17

Uranus 18

Neptune 18

The Minor Planets 19

Are There Other Planets? 20

The Moon 20

The Origin of the Solar System 24

Constellations 27

Meteors: “Shooting Stars” 28

Meteorites 29

Comets 30

Nebulae 32

The Milky Way 33

The Number of Stars 33

The Position of Our Solar System 35

The Movement of Our Solar System 36

Distances of the Stars 36

Temperature of the Stars 37

Fixed Stars 37

Double Stars 38

Colored Stars 38

Variable Stars 39

Temporary Stars 40

Star Groups--Clusters 40

Eclipses 41

Telescopes 43

The Spectroscope: Spectrum Analysis 43

Photography 46

The Tides 47

Gravitation 48

The Ether 49

Atomic Analogies 49

Thunder and Lightning 50

Fireballs 50

Atmospheric Electricity 50

The Earth’s Magnetism 51

The Aurora Borealis 51

Time: Measurement of 52

Space: Measurement of 52

The International Day Line 54

Calendars, etc. 54

Curved Space 55

The Temperature of Space 55

Light in Space 55

Life in Space 56

The Causes of an Ice Age 56

Why Do Stars “Twinkle”? 56

Why Does the Moon Sometimes Appear Larger? 57

Are the Planets Inhabited? 57

A Few Definitions 58

INTRODUCTORY

Astronomy is one of the oldest of the sciences--as it is one of the most fascinating! The early Egyptians, Assyrians, Babylonians and Chaldeans were, as we know, great astronomers, and, considering that they were compelled to make their observations without the aid of telescopes, some of their conclusions are truly remarkable in their accuracy. Men must always have gazed at the stars, and wondered at their number and their beauty; yet it is only within the past three or four centuries that accurate ideas as to the nature, size and structure of our Universe have come into being. No subject is so calculated to impress upon man his own relative insignificance as astronomy--to show him that the speck of matter upon which he dwells is so small that it cannot even be seen, from a relatively short distance in space! How puny and absurdly trifling seem his bickerings and his disputes, his wars and his hates, his jealousies and his failures, when viewed from the standpoint of infinite time and infinite space; mere struggles upon an ant hill, which, a few million years from now, will be uninhabitable, while the sublime immensity of Nature will proceed as if nothing had happened!

Yes, astronomy is a fascinating and romantic study, and the following little book is an attempt to summarize, very briefly, the most important findings of modern astronomical science upon this question. I have endeavored to make the subject as simple as possible, and to avoid all terms of a technical character, unless these are fully explained. It is my hope that the reader may be enabled to gain a fairly clear and accurate idea as to the nature and constitution of our Universe by a perusal of this little book.

ASTRONOMY FOR BEGINNERS

ASTROLOGY

Those who have not studied this subject will often ask the question: “What is the difference between Astronomy and Astrology?” It is merely this: Astronomy studies the heavenly bodies, and their movements, etc., by all available scientific means; while astrology, also utilizing this material, further asserts that the particular relative positions which the sun, moon, planets and other heavenly bodies occupy at the moment of birth _influence the individual_ born at that moment, and continue to influence him all through life. In other words, astrology is undoubtedly an exact science in so far as its astronomical _data_ are concerned; but its further inference, as applied to the living human being, is not; it depends upon historic beliefs and traditions which have been handed-down for centuries. So far as astronomers have been enabled to ascertain, there is not the slightest scientific basis for any belief in astrology; assuredly it is a curious and interesting occult study, but it must be understood to lie within that realm, rather than in that of exact astronomical science.

THE SOLAR SYSTEM

When we speak of the “solar system,” we mean our central Sun, and the various planets which revolve around it. The planets, beginning with the one nearest the Sun, and proceeding outwards into space, are: Mercury, Venus, The Earth, Mars, Jupiter, Saturn, Uranus, Neptune. Most of these planets have in turn, circling round them, smaller bodies of satellites; the Earth has but one--the Moon. Other planets have more than one. The planets vary greatly in size, as well as in their relative distances from the Sun. The following may help the reader to form a mental picture of their relative distances and sizes:

Imagine a large open common; on it place a globe 2 feet in diameter, by way of representing the Sun; Mercury will then be represented by a mustard seed at a distance of 82 feet; Venus by a pea at a distance of 142 feet; the Earth also by a pea, at a distance of 215 feet; Mars will be a small pepper corn, at a distance of 327 feet; the Minor Planets by grains of sand at distances varying from 500 to 600 feet; then a moderate sized orange ¼ of a mile distant from the central point will represent Jupiter; a small orange ⅖ths of a mile, Saturn; a full-sized cherry, ¾ths of a mile, Uranus; and lastly a plum, at 1¼ miles, Neptune,--the most distant planet yet known,--though some astronomers suspect there may exist another planet still further off, and hope one day to find it. (On the same scale, the _nearest_ “fixed” star would be 7,500 miles distant).

THE SUN

The Sun is the center of our solar (sun) system; it is the great giver of light and heat, without which life upon our planet would soon become extinct. It is an immense body, more than a million times the size of our earth. In fact, its _radius_ is nearly twice the distance of the moon from the earth! The mass of the Sun is 332,000 times that of the earth. It gives 600,000 times as much light as the full moon. The energy radiated per square yard from the Sun is equivalent to 140,000 horse power. The heat radiated by the sun would melt a layer of ice 4,000 feet thick every hour, all over its surface. Various estimates of the amount of heat upon the surface have been made, but these do not agree,--figures all the way from 10,000° F. to 180,000° F. having been given. Certain it is that its internal heat is terrific, and there is every indication that this heat has been more or less constant for millions of years in the past. No purely physical theories of its heat are at all satisfactory. The ultimate nature and source of the sun’s heat are unknown--though various theories have been advanced by way of explanation. I have discussed this question at some length, however in my little book in the present series, “New Discoveries in Science,” to which the reader is referred. (“What Keeps the Sun Hot?”)

The nature and constitution of the sun have, of course, been studied intensively for many years by astronomers. The apparent surface of the sun is called the “photosphere” (light surface). It is the part that gives forth most of the light and heat. Above the photosphere lies a sheet of gas, probably from 500 to 1,000 miles thick, called the “reversing layer,” which is cooler than the photosphere. Outside the photosphere is another layer of gas, from 5,000 to 10,000 miles deep, called the “chromosphere” (cooler sphere). The outermost portion of the Sun is the “corona” (crown). It is a halo of pearly light surrounding the sun, but it cannot be seen except during a total eclipse. It is of irregular form, and gradually fades out into the blackness of space at a distance of from 1,000,000 to 3,000,000 miles. This must not be confounded with the so-called “prominences,” which are vast eruptions of flame, spurting out from the sun’s surface, and extending into space for enormous distances--perhaps half a million miles! These also travel with enormous velocity--five or six hundred miles per second. The earth would appear an insignificant speck of dust, in this vast, roaring furnace of flame!

Of late years, the question of the so-called “sun spots” has aroused a great deal of interest, partly by reason of the fact that they apparently affect electrical and magnetic conditions upon the earth. These “spots” seem to reappear at stated intervals, and about every eleven years reach their maximum intensity, (The period of the revolution of the sun on its own axis has been estimated by their study.)

Although the sun-spots were studied before the eighteenth century, it is only within the past few years that the significance of these enormous spots has become known. For long it was thought that they were merely the great volcanoes of the sun; centers of great heat, generated by the glowing, fiery gases of the sun. In 1908, however, Prof. Hale demonstrated that the sun-spots acted as attraction centers, which drew towards them the hydrogen of the solar atmosphere. “Subsequently, it was found that these spots are the seats of great cyclones, in which cool hydrogen gas is set whirling and is sucked down in the great mælstrom of the Sun, rushing into the center of the spot at the rate of 60 miles a second. Consequently the spots are the center of great solar disturbances, which are of an electromagnetic nature.” From this it was concluded (1) that the spots are cooler than the surrounding area; (2) they are centers of violent cyclones; and (3) they are magnetic fields of great intensity. The connection of sun-spots with our weather, and the relation of one to the other, have also been studied within the past few years.

MERCURY

This is the smallest of the planets in our solar system, being only about 3,000 miles in diameter. It revolves round the sun in almost exactly 88 days, at a distance of approximately 36,000,000 miles, varying between 28½ million to 43½ million miles. Owing to its smallness, it is often difficult to see this planet, and a powerful telescope must be employed to study it effectually. It is thought that Mercury possesses mountains, but it is practically devoid of atmosphere. Dark, irregular spots have been observed upon the planet, and its surface is thought, by some astronomers, to resemble that of Mars, to a great extent. The solar heat on Mercury is about seven times that on us, owing to its proximity to the Sun. Schiaparelli, and others, have contended that the period of rotation of Mercury is exactly equal to its period of revolution round the Sun. If that be true, one side of the planet is always turned to the Sun, and the other side away from it. One side of the planet would thus be intensely hot, while the other side would be icy cold. Comparatively little is known concerning this small planet, though much study has been devoted to it.

VENUS

This is one of the brightest and most beautiful “stars” in the sky, and has for long been the theme of poets. It is practically the same size as our earth, its diameter being approximately 7,500 miles. It travels round the Sun in 224 days, at a mean distance of 67,000,000 miles. It revolves on its own axis in about 23½ hours, so that its days are nearly the same as ours. It is thought that Venus has a fairly dense atmosphere, and also water-vapor, which proves the existence of water upon its surface. Dense layers of cloud exist in the upper regions of its atmosphere, making direct observations of its surface very difficult. For this reason, comparatively little is known as to the conditions on the surface of Venus. Every eighth year Venus passes through a period of great brilliance, being then so bright as to cast a shadow, like the Moon. Venus must have a higher temperature than our earth; its sky is always overcast; thunder and lightning must be never-ending. Some controversy has existed as to the habitability of Venus; but the consensus of opinion is that life would be practically impossible upon its surface.

THE EARTH

The earth on which we dwell was thought by the ancients to be the center of the entire Universe--the Sun, stars and the vast host of Heaven were thought to revolve around it. This was the so-called “geocentric” theory. It was later on displaced by the so-called “heliocentric” theory, when it was found that the Sun, and not the Earth, was the center of our system. It only remains to be said that our Earth is the third of the planets which revolve round the Sun--Mercury and Venus being nearer the Sun than we are, and the others still further removed in space. We are thus but one of a number of similar bodies moving through space, all revolving round the central Sun.

MARS

This now-famous planet is somewhat smaller than our earth, being about 5,000 miles in diameter. It travels round the Sun in 686 days, at a mean distance of 140,000,000 miles. The eccentricity of its orbit is considerable. Mars appears to us reddish in color, owing to the vast stretches of arid soil (desert) which exist upon its surface. Water exists, but it is relatively scarce; it is gradually drying-up, as it does in the case of all bodies of the kind--the water on our own earth is very gradually becoming less and less, as the centuries pass.

Mars has been drawn particularly to the public’s attention, of late years, by reason of the dispute (still raging) as to its habitability, and the character of its so-called “canals”--the more or less regular markings, like long, dark lines which have been seen to exist upon its surface. Its surface has accordingly been studied minutely for many years, but it may be said that no unanimity of opinion exists as to its being an inhabited planet. Says Kæmpffert, in his “Astronomy,” (pp. 183-84):

“The mapping of Mars is no recent matter, for even in 1659 a rough sketch of the surface of the planet was made by Huygens, in which the V-shaped markings at the equator, pointing to the north, can be identified as the _Syrtis Major_. This was followed by rough sketches from time to time down to 1840, when Maedler first began a systematic charting of the planet. His map was followed in 1864 by Kaiser’s, by Flammarion’s in 1876, and Greene’s in 1877. Drawings of various parts of the planet were made during these intervals, but were not combined into good charts.”

“Observations made by Prof. Lowell and his staff at the Observatory, at Flagstaff, Arizona, have had a study of this planet especially in view.... The surface of Mars as seen in the telescope, is composed of two white polar caps, which wane with the approach of summer; orange areas, which are supposed by Lowell to be deserts, and blue-green areas, which change their hue to orange during the Martian autumn and winter, and resume their verdant tint in spring. The planet is covered with a network of fine lines, first discovered by Schiaparelli, in 1877; and called by him ‘canals’--a designation by which they are still known. These canals connect the polar caps with the temperate and equatorial zones. According to Prof. Lowell, they may be regarded as planetary irrigation ditches, which serve the purpose of leading the melting water of the poles to those desert regions which would still blossom, if properly watered. The canals disappear with the approach of winter, and creep down from the poles towards the equator in summer--a phenomenon which long puzzled astronomers, until Pickering ingeniously suggested that we see, not the canals themselves (for they are much too narrow) but the vegetation which fringes their banks--which withers as the cold of winter descends, and which flourishes with the melting of the snows.”

It may be said that this theory of the canals on Mars is not universally accepted by astronomers, but is warmly disputed in some quarters. The _markings_ are undoubted; but some astronomers are inclined to think they are due solely to vegetal growth, and are not the result of human hands. The controversy still continues. Meanwhile, two satellites of Mars were discovered in 1877.

JUPITER

Jupiter is the largest of all the planets, having a diameter of about 88,000 miles; it is only about 1,000 times smaller than the sun--that is, about 1,000 times larger than our earth. In volume, it is 1,300 times larger than our globe. Gravitation must be enormous on its surface. Its density is however relatively low--being only about one-quarter that of the earth. It is thought to be a world of water and more or less dense gas. It is constantly covered by a thick blanket of clouds and vapors, making direct observation very difficult--as we saw was the case with some other planets. Immense as this planet is in size, it revolves at a tremendous speed--approximately 10 hours. Owing to its immense bulk, it cools more slowly than a body such as our earth. Consequently it will take tens of millions of years for it to cool sufficiently to permit life to become manifest upon its surface. Yet it may at that time! In a sense, Jupiter may be said to be a planet of the future; when our earth is cold and dead, Jupiter may be teeming with animate existence.

Jupiter has 8 satellites, and a number of dark bands cross its surface from east to west. A certain dark spot upon its surface has caused great interest among astronomers, who are unable to determine its exact nature. This planet revolves round the Sun in rather more than 11¾ years, at a mean distance of 483,000,000 miles.

SATURN

Saturn revolves round the Sun in 29½ years, at a mean distance of 886,000,000 miles, in an orbit slightly eccentric. According to Barnard, its equatorial diameter is 76,470 miles, and its polar diameter 69,770, which figures imply a polar compression of 1/11. This planet is famous for the celebrated “ring” which surrounds it. As a matter-of-fact, when observed by means of high-powered telescopes, this famous “ring” is found to consist of a number of rings--three being clearly distinguishable. For long it was thought that these rings were vaporous; then that they were solid; but the present view is that they are composed of myriads of discrete particles of matter, so closely compacted together that to our remote eyes they appear as a solid mass. These rings are fairly broad, but relatively thin in diameter; they resemble a sort of huge disk. Perhaps 100 miles would be the thickness of these rings. Their diameter, however, is tens of thousands of miles in breadth. Owing to these rings, Saturn is one of the most beautiful of all the planets, when viewed through a high-powered telescope.

Saturn doubtless has certain features in common with Jupiter, as to its physical appearance. The general hue of the planet is yellowish-white; it probably has no atmosphere, or at most a very tenuous one. It is attended by ten satellites, the largest of which is known as Titan, thought to be about 2,700 miles in diameter.

URANUS

This is the next to the last planet in our solar system. It is a large planet, having a diameter of about 31,000 miles. Uranus revolves round the Sun in rather more than 84 years, at a mean distance of 1,781,000,000 miles. It is attended by four (or five) satellites. Belts and spots have been seen upon its surface, but relatively little is known concerning its physical conditions, owing to its great distance from us, and its relative smallness. This planet was discovered, as is well known, by Herschel, and was named after him, but its name was subsequently changed. (It is still mentioned as Herschel, in certain books upon Astrology.) It is probable that the temperature of Uranus is relatively low, owing to the small percentage of the sun’s rays which reach its surface. It has been calculated that its theoretical temperature is about 330° F.

NEPTUNE

The past century was remarkable for the discovery of this new planet: Neptune. How it was accomplished is a matter of great interest. In 1820, it was found that Uranus was not following its computed path. Adams, of Cambridge, and Leverrier, of Paris, each independently took up this question, and, assuming that this perturbation was due to the presence of a planet still more remote from the sun (which had been hinted at in 1830 by Bessel) they set to work to calculate its position in the heavens. They finished this at about the same time, arriving at practically the same conclusions. Adams’ results were first submitted to the Astronomer Royal, who set them aside without consideration until too late. Leverrier sent his conclusions to a German astronomer, Galle, who found the planet the first evening he looked for it, September 23, 1846.

Neptune is the furthest known planet of our solar system; it is a very large body, having a diameter of about 37,000 miles. It revolves round the sun in an immense orbit which it takes 164 years to complete. Its mean distance from the Sun is nearly 2,800,000,000 miles--a majestic sweep through the heavens! Relatively little is known as to the physical conditions of Neptune, owing to its immense distance, and its relatively small size. At least one satellite is known to exist. The temperature on Neptune must be extremely low, owing to its distance from the sun, whose rays would be exceedingly feeble at that great distance.

THE MINOR PLANETS