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





Between Mars and Jupiter, a number of small bodies are known to exist,

which have sometimes been dignified by the name of “minor planets.”

They have also been called “Planetoids” and “Asteroids.” Special names

have been given these individual small bodies--Eros, Ceres, Pallas,

Vesta, Juno, etc. Eros passes, upon occasions, very close to our

earth; again passing beyond the orbit of Mars. Several hundreds of

these smaller planets are now known to exist--as though they were the

remnants of some shattered world. These bodies are very small: Ceres,

_e.g._, being about 250 miles in diameter; Pallas, 304 miles; Vesta,

211 miles; while a number of the others are thought to be from 5 to 15

miles in diameter.









ARE THERE OTHER PLANETS?





Inasmuch as some of the planets known to us have only been discovered

so lately (relatively) the question has naturally been asked: “Why may

there not be _other_ planets, beyond Neptune, still undiscovered?” It

is a perfectly legitimate question, and no definite answer to this

query can be given. It seems rather improbable that another planet

will be discovered. However, it is a conceivable possibility, and M.

Flammarion has stated that, in his estimation, such a planet probably

exists--gravitating at a distance 48 times as great as the distance

between the earth and the sun--that is to say, 7,500 million miles, in

an immense orbit which it takes at least 330 years to accomplish. Proof

as to the existence of such a planet has not, however, as yet been

forthcoming.









THE MOON





The Moon is the Earth’s only satellite, and by far the nearest body in

space to our Earth. Many astronomers are inclined to think that the

Moon at one time formed a part of the Earth, but was wrenched away from

it, leaving a huge cavity, which is now occupied by the Pacific Ocean.

The Moon is a cold body, emitting no light or heat of its own; all the

light which it seems to shed is entirely _reflected_ light--reflecting

the sun’s rays, much as a mirror might reflect them; hence its

beautiful silver color.



In round numbers, the Moon is approximately 240,000 miles distant

from us in space--the distance varying from 221,600 miles to 252,970

miles--causing a corresponding variation in its apparent diameter and

parallax.[A] The circumference of the Moon’s orbit is a little more

than a million-and-a-half miles, and it travels through space with the

velocity of 2,288.6 miles per hour, or 3,357 feet per second.



[Footnote A: See page 58 for a definition of this term.]



Our satellite always keeps the same face turned towards the Earth, so

that we only see one side of it; the other side is forever hidden from

the sight of man. However, the axis of the Moon tilts, in relation to

the earth, and permits us to glimpse a little more of the surface both

north and south, so that about five-eighths of the surface has actually

been observed.



The surface of the Moon has been subjected to intensive study, and its

“geography” is now as well known as that of our own earth. Vast “seas”

(i. e.) sea bottoms, mountain ranges, solitary mountain peaks, enormous

craters, are readily observed, and modern telescopes have now brought

the moon so close to us that it has been said that any body as high as

the Woolworth Building, in New York, would cast a shadow which could be

observed and noted.



The fact that the same face of the Moon is always seen by man does not

mean that this body remains stationary; it revolves on its own axis,

from west to east, but this revolution occupies exactly one siderial

month. The result is that the days and nights on the Moon, are many

times the length of our days and nights. The surface exposed to the

sun’s rays must get extremely hot, and, when deprived of these rays,

extremely cold. It has been estimated that the mean temperature of the

moon’s surface must approximate 200° F., during the “day” time, and

approach the intense cold of inter-stellar space during the “night”

(perhaps -250° C.). This would render life or vegetation of any kind

very unlikely. However, Professor Pickering has lately asserted that

vegetation _does_ apparently spring into being with extreme rapidity

during the moon’s day time--evidently remaining latent during the

intense cold of the “night.” (Some interesting material on this topic

may be found in Shipley’s “Is the Moon a Dead World?” No. 557 of the

present series.)



The volume of the Moon is about one-fiftieth that of the earth, but

its mass is only about one-eightieth that of our planet. The Moon

is practically devoid of atmosphere, which is another reason why it

cannot support “life,” in our sense of the word. Two theories have

been advanced as to the absence of the moon’s atmosphere: (1) that it

gradually combined, chemically, with the materials on its surface;

and (2) that it gradually escaped into space, because of the low

gravitational pull of the moon. There is no water on our satellite,

which means that there is no ice and no snow. The moon being so much

smaller than our earth, the pull of gravity is of course much less also.



Yet it is well known that the tides, on the earth, are greatly

influenced by the moon. Every atom composing our satellite must exert

some subtle pull upon every atom of our oceans, in order thus to affect

them. What is the nature of this attraction? Here we encounter the

mystery of gravitation! This question must accordingly be postponed

until we come to our discussion of that subject.



One of the most remarkable and distinguishing characteristics of the

moon consists in the so-called “lunar craters,” which appear to be

immense, extinct volcanoes. More than 30,000 of these have now been

mapped, varying in size from small hills to immense basins 50, 60, 100

miles in diameter. Ptolemy is 115 miles across, while Theophilus is 64

miles in diameter and 19,000 feet deep. The curious thing about these

lunar craters is that they are unlike the hilly volcanoes known to us

on our earth. They are rather huge circular pits, often square miles in

extent, surrounded by a circular wall, and almost invariably having a

single mountainous cone in the center.



Various theories have been advanced by way of explanation of these

craters. The most important of these are (1) that they represent

extinct volcanoes; (2) that they indicate spots where masses of matter

have dashed into the moon, from surrounding space; and (3) that

they represent the surface of the moon, when it was a hot, seething

mass--their resemblance to the “bubbles” formed at the surface of

boiling glue, mud, etc., being pointed to as analogous. Unanimity of

view does not exist even yet as to their origin.



The ever-changing “phases” of the moon have been observed by

generations of lovers. Thus, the new moon, full moon, etc., are

commonplace sights. These apparent changes are, of course, due entirely

to the relative position of the sun at the time. If the sun illumines

the whole face of the moon, as viewed from our earth, we have full

moon; if only a small portion of it, we see the first quarter, etc.

The whole disk of the moon may always be seen, however, by careful

observation. It is hardly necessary to say that the so-called “Man in

the Moon” is a mind’s eye picture, created by the configuration of the

various mountains, seas, etc., upon its surface.









THE ORIGIN OF THE SOLAR SYSTEM





Men in every age have speculated as to the constitution and origin

of our world, and of the Universe in general. The first really

detailed and scientific attempt was made, however, little more than a

hundred years ago by Laplace--and subsequently known as the Laplacian

hypothesis (1796).



Concurrent with the establishment of new facts, there was a tendency,

throughout the past century, to find some philosophic interpretation

of the Universe and its structure; to ascertain, if possible, the

“beginnings of things,” and explain them in some satisfactory manner.

This has been considered as epoch-making in astronomical research as

Darwin’s great theory of the Origin of Species was in biology. The

history of the two theories has been similar also. Both have served a

useful purpose; have helped to direct scientific thought for years; and

both are now largely outgrown. Both were, however, of great value and

of daring originality.



Laplace assumed the primal existence of a glowing ball of gas rapidly

revolving about an imaginary axis running through its center of

gravity. During the process of cooling, this mass would contract, and a

disk of gas would be thrown off in this manner; and hence a number of

gaseous rings be formed, which would ultimately cool down and assume a

spherical form. Laplace conceived that this process might be interfered

with by internal accident and by comets from without.



The first modifications of the theory were suggested by Sir Norman

Lockyer, who proposed what is known as the meteoritic hypothesis in

its place. The central idea of the theory was that--“All self-luminous

bodies in celestial space are composed either of swarms of meteorites

or of masses of meteoric vapor produced by heat.” The theory was based

on spectroscopic analysis. It said that the original nebulæ were

composed, not of gases, but of meteoric material and cosmic dust. This

theory was never fully accepted in place of that of Laplace, however;

but it paved the way for a more recent theory, which may be said to

be satisfactory and more or less inclusive. This is known as _the

planetesimal hypothesis_, and was advanced within the past few years

by F. R. Moulton and T. C. Chamberlin, of the University of Chicago.

At the present time, it may be said to be the accepted theory, so far

as any such theories are accepted, since it accords with all the facts

in a remarkable manner, and has been experimentally demonstrated. In

outline, the theory is as follows.



If examination of the nebulæ in the sky be made, out of 120,000 of

them, nearly every one of them is found to be in the spiral form.

So common and universal is this, indeed, that it was concluded that

this must represent “some prevalent process in celestial dynamics.”

This process is, according to Chamberlin, the actual formation of a

solar system. As this spiral revolves, it accretes to itself various

smaller bodies, with their gases, atmospheres, etc., and these become

consolidated with the original body. As time went on, this spiral

gradually tended to decrease its speed, but at the same time, continued

to accrete bodies which came into contact with it in its flight

through space. Thus, we have to imagine our world, not as an expanded

molten mass which has continuously cooled and contracted, but, on the

contrary, as a small lump of cold and solid fragments that, moving

about in accordance with its attractions, continuously fed upon its

surrounding assemblage of “smaller fry,” and thus grew to its present

size. About the young earth so engaged it is possible to read, on the

basis of the hypothesis, something of its early history.



Thus we see that the old theory of Laplace has been reversed; and that,

instead of a great central mass of moving, white-hot gas, we have a

number of smaller bodies, all busily engaged in building up themselves,

at the expense of the surrounding masses of still smaller matter--much

as a crystal accretes to itself minute specks of crystalline matter

from the solution in which it is immersed. This is the newest of the

cosmological theories. According to it, all the planets might have been

formed at the same time. This view of the formation of the universe

opens up still wider problems, which are now the subject of keen debate.









CONSTELLATIONS





The ancients, when studying the heavens, saw all kinds of imaginary

animals in the various star-groups, and named them accordingly. A

constellation is really a group of stars, which seems to constitute a

sort of system of its own. Thus, we find reference to the Great Bear,

the Little Bear, the Bull, etc. It is difficult for the uninitiated

to see the resemblances which the ancients did, in these various

star-groups, and astronomical science has re-named them, as well as

adding a large number of new constellations to those already known.



Stars of the first six magnitudes (roughly) are visible to the

unaided eye; those of lesser magnitude must be detected by the aid

of telescopes. About 5,000 are thus visible; the number is increased

according to the magnifying power of the telescope used, and it is

estimated that there are more than 100,000,000 within the range of

visual and photographic instruments!



The names of a few of the best known constellations are as follows:

Ursa Major (The Great Bear); Cassiopeia; Hercules; Scorpio (the

Scorpion); Corona Borealis (The Northern Crown); Boötes (The Hunter);

Leo (the Lion); Andromeda; Perseus; Auriga (The Charioteer); Taurus

(the Bull); Orion; Canis Major (The Great Dog); Canis Minor (The

Smaller Dog); Gemini (the Twins), etc.



In these various constellations, certain noted stars are to be found.

Thus, in Gemini, its two principal stars are Castor and Pollux. In

Canis Major is Sirius. In Orion may be found Aldebaran and Betelgeuse.

The Pleiades and Hyades groups are in Taurus. In Perseus is Algol. In

Lyra is the first-magnitude star Vega. And so on.



The “Big Dipper,” so-called, is part of the Constellation Ursa Major;

and it is almost universally known that the Pole Star (Polaris) may

readily be found by its means. The constellations must be traced and

learned, one by one; but this the student must accomplish for himself!









METEORS: “SHOOTING STARS”





What are popularly known as “shooting stars” are not stars at all; they

are really meteors which appear at altitudes of from 60 to 100 miles,

as a rule, from the earth, and move over paths of 40 or 50 miles at a

rate of from 10 to 50 miles per second.



The light given out by meteors is due to their being heated by friction

with the atmosphere. Falling from space, they become attracted by the

earth’s gravitation, and fall towards it. Here they encounter the

earth’s atmosphere, and their rapid passage through it creates terrific

heat, which tends to consume them before they reach the face of the

earth, turning them into gases, or causing them to fall gently as dust.

This sudden flash is the “shooting star” in question.



The number of such meteors is very great. It has been computed that

between ten and twenty million strike the earth’s atmosphere daily.

Occasionally, a large number of meteors fall together; and then we have

a “meteoric shower.”









METEORITES





Occasionally, however, some of these bodies _do_ reach our earth,

despite the friction and opposition of the earth’s atmosphere. Such

bodies are called meteorites, siderites, or aerolites. Only a few of

these are seen to strike the earth yearly, and it is a remarkable fact

that, so far as we have any record, not one of them has ever struck a

town or killed an individual. The outside of the meteorite during its

passage through the air is subject to intense and sudden heating, and

the rapid expansion of its surface-layers often breaks it into many

fragments. The surface is fused and, on striking, cools rapidly. The

result is that it has a black, glossy structure, usually with many

small pits where the less refractive material has been melted out. Such

meteorites may be seen in most large museums.









COMETS





During the past century, many of these “tramps of the solar system”

have been discovered and their orbits computed. The “head” may range

from ten thousand to a million miles, or more, while its “tail” may

stream across the heavens for millions of miles. These comets’ tails

always point away from the sun; and for long the reason for this was

not known. It is now believed that this is due to light-pressure; the

energy of the sun’s rays press this delicate matter outwards into

space. (This theory has been elaborated at considerable length by the

Swedish astronomer and chemist, Arrhenius.)



Many readers of this little book will remember the excitement caused

by Halley’s comet, which came relatively close to the earth in 1910,

so that many persons thought there would be a collision, and were

terrified accordingly! As a matter of fact, the tails of comets are

usually of almost inconceivable tenuosity. Halley first observed this

comet, computed its orbit and predicted the date of its return.



Some comets have tails: others do not. Not much is known concerning

the origin and destination of comets; where they originated, or how.

They travel at tremendous speed over many millions of miles of space,

returning after a few years, or after a lapse of several centuries.

They are very striking looking, even when observed by the naked eye. A

number of comets have been noted. The following are a few of the more

remarkable comets which were observed during the past century:



The Comet of 1811. This was visible for nearly a year and a half, and

was carefully studied by William Herschel. Its tail was said to be

nearly a hundred million miles long, and fifteen million miles broad.



Encke’s Comet (1819). This comet is of extreme interest because of

its change of volume. Moulton says: “On October 28, 1828, it was

135,000,000 miles from the sun, and had a diameter of 312,000 miles.

On December 24, its distance was 50,000,000 miles and its diameter was

14,000 miles; while at its perihelion passage of December 17, 1838, at

a distance of 32,000,000 miles, its diameter was only 3,000 miles.”



Beila’s Comet (1826). This comet has a most interesting history. In

1846 it was again seen; and a month later it had divided into two

parts. They traveled along parallel orbits, some 160,000 miles apart.

In 1852, they were seen to be 1,500,000 miles apart. Since then they

have never been seen. They have, apparently, vanished from the face of

creation!



Donati’s Comet (1858). This comet was visible for more than nine

months. Its tail was estimated as 54,000,000 miles long. Its period of

revolution was more than 2,000 years.



The Great Comets of 1880 and 1882. The latter of these passed through

some hundreds of thousands of miles of the sun’s corona. Its orbit was

not appreciably changed, but, after emerging, it was seen to possess at

least five nuclei--showing the effect upon the comet of the disruptive

forces through which it had passed.









NEBULAE





These are of especial interest, for the reason that they have played

so large a part in forming cosmic theories--the Laplacian, the

Planetestimal, etc. Nebulæ are of various kinds--“Annular Nebulæ,”

resembling a flat, oval, solid ring, having a dark hole in the center.

Then there are “Elliptic Nebulæ,” of varying degrees of eccentricity;

the Great Nebula in Andromeda being a good example. (Numbers of

isolated stars may be found within its limits.) “Spiral Nebulæ” are,

perhaps, the best known of all, and their name accurately describes

their appearance. There are also the so-called “Planetary Nebulæ,” as

well as Nebulous Stars, Irregular Nebulæ, etc. Of late years, much

interest has been centered upon the so-called “Dark Nebulæ.” Herschel

had long before described various “holes in the heavens,” wherein no

stars could be discerned. It is now believed that such spots do not

represent “holes,” as much as dark masses of matter, which seem to

blot out the bright stars behind them. The interested reader may refer

to Hale’s “The Depths of the Universe” for additional information

upon this topic, which is relatively new to astronomy. It is also

interesting to note that the spectra of Nebulæ contain the bright

lines in the green of a substance called “nebulium,” because it is not

found except in nebulæ.









THE MILKY WAY





This is, in a sense, one vast nebula running right round the heavens

in the form of a belt, or ring; its familiar resemblance to spilt milk

being the origin of its popular name. To the naked eye, it appears

merely a hazy band of light, but the telescope shows that it is made

up of an enormous number of stars, millions of miles apart, but which

can only be distinguished from one another by telescopic aid. It

constitutes the so-called “Galaxy.” It seems to be spread out in the

form of a vast disk, whose diameter is many times its thickness. Our

solar system appears to be near the center of this vast system, and, as

we penetrate further and further into space, it becomes apparent that

fewer and fewer stars, and fewer and fewer nebulæ, seem to exist. Hence

the limitation of the material Universe. The Milky Way is made up of

thousands of millions of suns; yet their enormous distances make them

appear to constitute one vast, luminous belt encircling our globe!









THE NUMBER OF STARS





When the heavens are viewed with the naked eye, a few hundred stars may

perhaps be seen--some bright, some faint. Viewed through opera glasses,

many more stars may been seen; while their number is again greatly

increased by the use of a telescope. The larger and more powerful the

telescope employed, the greater the number of stars thus discovered in

the depths of space. The interesting question thus arises: What is the

total number of stars in the entire firmament? Can they be estimated?

And if so, what would their approximate number be?



What we call “stars” are, of course, in practically all cases

_suns_--often vastly larger and hotter than our own. These stars

differ from one another in order of brilliance; some are brighter than

others. They are accordingly classified according to their order of

brilliance, and known as stars of the “First Magnitude,” of the “Second

Magnitude,” etc., up to about the Seventeenth Magnitude. Any star of a

given magnitude is, roughly, about two-and-a-half times as brilliant as

one of the next lower order, and this variation holds throughout--each

magnitude being that much greater in brilliance.



The “magnitude” of the stars varies according to their light-giving

power, and also their distance from us. One of the methods adapted to

measure the magnitude is to compare its brightness with an artificial

star, gradually cutting-off its light by means of neutral, tinted glass

until the two are equal. The color of the star must be taken into

account, in such measurements, the eye being more sensitive to some

colors than to others.



Now, it is an interesting and significant fact that the number of the

stars decreases as their magnitude decreases; that is to say, the

greatest number of stars are found of the first magnitude; a lesser

number of the second; still less of the third, and so on (broadly

speaking). After reaching the ninth magnitude, the number very rapidly

diminishes. It has been calculated that there are about 120,000,000

stars in the first 16 or 17 magnitudes. If the proportion were

maintained throughout, however, there would be more than ten times that

number. Some authorities have asserted that there are, roughly, half a

billion stars of varying magnitudes in the heavens.









THE POSITION OF OUR SOLAR SYSTEM





It has been maintained that our solar system is at, or very near,

the center of the whole Universe. Certain it is that the further we

proceed into space, the less the number of stars encountered, which has

given rise to the suspicion that their number is actually _limited_,

and that the whole Universe consists of a sort of sphere, in which is

enclosed all the stars that exist, and that, beyond this sphere, no

stars whatever remain. No matter exists beyond this point! Such a view

fits in rather well with Einstein’s conception of “curved space,” and a

finite universe of infinite proportions! Of course, it is conceivable

that, outside this vast system, another similar system may exist, and

another and still another; but of such systems we know nothing, and it

seems improbable that proof of their existence could ever be obtained

by man. So far as we can tell, the universe is _One_, and the matter

and energy of that one are limited.









THE MOVEMENT OF OUR SOLAR SYSTEM





It has been shown that our whole solar system is sweeping through space

at the speed of about ten miles a second towards the stars in the

constellation Hercules, and particularly towards Vega, one of its suns.

However, Vega is likewise moving through space, so that by the time our

sun reaches the spot now occupied by Vega (half a million years or so)

Vega will no longer occupy that position, and no “collision” will take

place in consequence! We shall not, in fact, pass very near that star.









DISTANCES OF THE STARS





Astronomical distances are so vast that they can only be measured in

the mind relatively. The distances between the planets in our own

solar system seem big enough; yet they shrink into insignificance when

compared to the distances which separate our whole solar system from

even the nearest of the stars. _Alpha Centauri_ is the nearest star,

and it is separated from us by a distance 276,000 times as great as

that which separates us from our sun. It is approximately 25 billion

miles away. Traveling with the speed of an express train flung into

space, at 40 miles an hour, towards the nearest star, without any

stoppage or any slowing down, we should not arrive at our destination

until after an interrupted flight of 75 million years. Yet this is

our nearest neighbour! Only a _very few_ of the stars are within

400,000,000,000,000 miles of the sun. The great majority of them are

many times this distance from us.



So vast are these distances that some simple means of expressing them

on paper was sought. A “light Year” was finally decided upon as the

_unit_ of measurement--that is, the distance which light would travel

in one year, speeding at the rate of 186,000 miles a second. It has

been estimated that many stars are one, two, three and perhaps five

hundred thousand light-years distant from us in space. The interested

reader may figure-out the number of miles this represents for himself!









TEMPERATURE OF THE STARS





Measurements which have been undertaken prove that the surface

temperature of our Sun is between 5,000°C. and 7,000°C. It is

thought that many stars are considerably hotter than this. We can

form no adequate conception of such intense heat; all matter would

be vaporized; yet, under the enormous pressures which must prevail,

these vapors would in turn be converted into thick, semi-fluid

substances--especially in the interior.









FIXED STARS





The so-called “fixed” stars are those which do not appear to change

their positions in the heavens for long periods of time together. There

are, of course, no “fixed” stars at all since every celestial body is

moving with greater or lesser rapidity through space; but these stars

are so far distant from us that such movements are inappreciable,

even after long periods of time, and in spite of the most careful

observations. In comparison with the more rapidly moving heavenly

bodies, they do not appear to “move,” and have been denominated “fixed

stars” in consequence.









DOUBLE STARS





A large number of stars appear single, when viewed by the naked

eye, but when seen through a powerful telescope, are seen to be, in

reality, two stars which revolve round one another. Many thousands of

such double stars are now known to exist; indeed, apparently single

stars have been found, upon closer examination, to be composed of

a group of four or five or more stars--so that the name “multiple

stars” has been given to such groups. They are near one another in the

astronomical use of that word--though they may actually be hundreds

of thousands, or millions of miles apart. Many of these double stars

seem to be quite separate from one another. Others appear to have some

physical connection. Those which are known to form systems are known as

_binaries_.









COLORED STARS





Many of the double stars exhibit curious and beautiful phenomena

of complementary colors. In such cases, the larger star is usually

more or less reddish or orange, and the smaller one bluish-green or

greenish-blue. Many of the double stars, on the contrary, are of the

same color. There are white, red, blue, orange, green and yellow

stars. The planets also vary greatly in color--Venus, e.g., being

white, Mars reddish, etc. Inasmuch as the planets only reflect light,

however, this is due to quite different causes; the other colored stars

are self-luminous suns which emit light of their own.









VARIABLE STARS





In addition to variations in the color of stars, they also vary greatly

in brilliance, and certain stars are much brighter at times than at

others. In some cases these changes in brilliance are regular; in

others, irregular. “Omicron,” for example, which, Bayer recorded in

his Atlas in 1603, is a regular variable; its period of change is 331

days, 8 hours; in other words, it reaches its greatest brightness about

12 times in 11 years, when it sometimes attains the brilliancy of a

star of the 2nd magnitude, at which brilliancy it remains stationary

for about a fortnight. It then diminishes during about three months,

until it sinks down to a star of magnitude 9½, or even becomes totally

invisible. It remains in this condition for about 5 months, and then

gradually recovers--during the next following 3 months--its maximum

brilliancy. In other words, its brilliancy is absolutely periodic.

Other variables are by no means regular, however, but “come and go” at

different intervals.



Various theories have been advanced by way of explanation--one of

the simplest being that such stars are in reality double, one being

luminous and the other not; and that, during their revolutions, the

non-luminous star partially or totally eclipses the bright one, at

stated intervals. The whole subject, however, is difficult, and much

yet remains to be learned concerning these variable stars.









TEMPORARY STARS





From time to time, stars have suddenly appeared in the heavens, where

no star existed before! Such stars have usually become increasingly

brilliant for a short period of time, and then as suddenly died

away again, leaving no trace of their existence behind them. These

“new stars” for long puzzled astronomers. The theory often advanced

to explain them is that some distant star has “exploded,” and the

increasing brilliance which we see is the result. If such were the

case, its sudden dimming-down and disappearance would be quite

intelligible--as would be its sudden appearance. A large number of

such stars have now been recorded, and their existence is no longer in

doubt. In some cases, they have remained visible for weeks or months

before their final disappearance.









STAR GROUPS--CLUSTERS





Here and there throughout the sky are places where the brighter stars

seem to be clustered. These families of stars are of such magnificent

proportions as to stagger the imagination. Among the best known are the

Pleiades, the Hyades, Coma Berenices and Orion. Although they appear to

us very close together, they are not really so, being usually several

hundreds of thousands of miles apart. Many of these star-groups

are irregular; but numbers of them constitute clusters, which are

of various sizes and shapes. Perhaps the most interesting are the

so-called “globular clusters,” because they present the appearance of

stars having been massed together as globes. Some of them contain five

or six thousand stars. Although they appear to us so close together,

it has been calculated that, in a cluster containing 5,000 stars the

average distance of the stars from one another would be 30,000 times

the distance of the sun from the earth! The vast distances of space

considered in astronomy may perhaps be realized by this fact--when

it is considered that such a cluster appears to us as a single star,

only capable of being separated into its component parts by means of

high-powered telescopes!









ECLIPSES





The total eclipse of the Sun, January 24, 1925, brought the subject of

eclipses to the public attention as never before, and many thousands

of persons watched that beautiful and impressive sight through smoked

glasses or strips of film.



When we speak of eclipses, we usually mean an eclipse of either the Sun

or the Moon. How are such eclipses caused?



A total or partial eclipse of the sun is caused by the moon passing

between the earth and the sun, the three celestial bodies forming, as

it were, a straight line. The sun is then shut-off from the vision

of the inhabitants of our globe over a certain, limited area of its

surface. The shadow cast by the moon falls across the earth.



But how is the moon eclipsed? Certainly the sun does not pass between

the moon and the earth, on such occasions! What causes the moon to be

eclipsed?



The answer is as follows: Inasmuch as both the earth and the moon are

illuminated by the sun, they both cast long shadows into space, as any

solid body does, when held in front of a strong light. The earth’s

shadow trails away for thousands of miles into space. Into this shadow

the moon enters, and when it does so, it becomes eclipsed--totally or

partially, as the case may be. Total eclipses are instances when the

whole surface of the celestial body is apparently covered; partial

eclipses are those in which only a portion of the body is dark--the

remainder being still visible.



In addition to eclipses, two other astronomical phenomena of interest

should here be mentioned: _Transits_, and _Occultations_. By “transit”

is meant the passage of some other heavenly body between ourselves and

the sun. Thus, Mercury and Venus, both lying nearer the sun than the

earth, occasionally pass in front of it. We then have a transit of

Venus, or a transit of Mercury, as the case may be.



By “Occultation” is meant the hiding of one heavenly body by

another--as when the moon hides some other planet or star, or one

planet hides another planet or star. The three bodies are then “in

line” as before. Of course, all eclipses represent instances of

Occultation.









TELESCOPES





Telescopes are of relatively recent origin; the ancients were forced

to make their observations without them, which makes some of their

conclusions all the more remarkable. There is considerable evidence

that the builders of the Great Pyramid employed the “Grand Gallery” for

astronomical observations (see “The Great Pyramid of Egypt,” in the

present series), and other devices were employed. But no telescopes of

any great power of magnification existed before the last century, while

our present marvelous instruments of precision are the evolution of the

present century.



Telescopes are of two kinds: refracting and reflecting. Any small

telescope exemplifies the former; the incoming light-rays are focussed

by a series of lenses, and directly observed by the eye. In the

employment of reflecting telescopes, however, another principle is

employed: the incoming light-rays are caught and reflected by means

of a curved mirror, and focussed on a lens, which in turn is inserted

in an elaborate eye-piece, in which the light-rays are magnified and

measured. Some of the modern instruments have a forty or more inch

aperture, and are capable of enormous powers of magnification.









THE SPECTROSCOPE: SPECTRUM ANALYSIS





For more than two thousand years, astronomy remained a purely

mechanical and mathematical science, being limited to observations and

deductions therefrom; but in 1860 the method of spectrum-analysis was

discovered. This was a most revolutionary discovery, inaugurating, as

it did, the whole science of astro-physics; and enabling us to know as

much of the physics and chemistry of distant stars and nebulæ--their

nature, constitution, and temperature--as we know of the planets of our

own system! Even the existence of otherwise invisible stars has been

demonstrated in this manner--their orbits, rate of motion, and mass.

The science of astro-physics is now one of the most exact in the whole

realm of science; and has only been rendered possible by the invention

of the spectroscope. As this instrument plays such an important part

in all astronomical research, a brief explanation of the instrument

becomes necessary.



If a ray of sunlight be passed through a glass prism, the ray is split

up into its primary colors; so that, instead of a single spot of white

light being visible a narrow band of brilliant colors is seen--ranging

from red to violet. But this is not the most important part of the

discovery. When this spectrum was closely examined, it was found to

be crossed by numerous black bands of various thicknesses. Sometimes

these occurred in groups, sometimes singly. By enlarging the spectrum

by passing it through several prisms, as many as 3,000 of these bands

could be counted. The nature and explanation of these strange bands

of blackness remained long uninterpreted, however. It remained for

Kirchoff, in 1860, to discover their uses and significance.



Briefly, it is this. The chemical elements, when heated to a state

of incandescence, present each one its own characteristic spectrum;

each one has its own peculiar markings, or band of lines. No two

elements are exactly like in their bands, as shown in the spectrum.

Hence, whenever that particular marking is observed, it becomes certain

that that element, and none other, is present. These spectra are very

varied; iron, for example, has more than 2,000 such bands, while lead

and potassium have but one each.



In this way--all the chemical elements having been studied, and their

characteristic bands known--it became possible to explore the stars,

planets and suns, and discover their chemical composition. For, no

matter where an element was discovered--on this earth or on the

remotest star--it would always cast its particular spectrum, when thus

examined. The effect of all this upon astronomy can be perceived at

once. Not only the heavenly bodies known to us, but those which have

never been seen by human eye--even when aided by the most powerful

telescopes--can be studied and their chemical composition and structure

accurately determined. Here is progress indeed!



All this becomes the more remarkable when we stop to consider the

immense distances of space, and how widely separated the heavenly

bodies are from one another. This may, perhaps, be shown by one or two

illustrations. We are, roughly, about 93,000,000 miles from our own

sun. Now, the majority of the stars we see are suns, like ours. The sun

next removed from us in space is about 275,000 times as far from us as

we are from our sun. The orbit of Halley’s comet, of which so much has

been written lately, is some 3,280,000,000 miles in length; and this

sporadic body, coursing through space at a speed 50 times greater than

a rifle bullet, takes 75 years to complete its circuit. The nearest

star has been calculated to be nearly 25 trillion miles away; while

some of the stars are 40 times as far from us as that!









PHOTOGRAPHY





The second great engine of astronomical research, that has been added

during the past century, is _photography_. By this means exact maps

may be taken of the heavens at any hour of the night, and the precise

position of thousands of stars determined with the utmost exactitude.

A chart of the heavens, made in this manner, is not only more complete

but more accurate than the combined observations of any number of men

could possibly be. Moreover, the photographic plate will record the

existence of stars which cannot be seen even with the aid of the most

powerful telescopes. This is due to the fact that the plate gradually

collects light, and its _cumulative_ effect is noticeable, when its

_immediate_ effect cannot be perceived. This power of photographic

plates is most valuable, and cannot be duplicated in any other manner.

We are assured on good authority that “an ordinary good portrait camera

with a lens three or four inches in diameter, if properly mounted so

that an exposure of several hours can be made, will show stars so

minute that they are invisible even in the great Lick telescope.” An

international photographic chart of the heavens is now under way,

which, when finished, will represent an accurate catalog of every

visible sun, star, and planet, in the sky. After this, any unusual body

should be quickly discovered.



But photography is employed not only for mapping out the heavens, but

for reaching the farthest stars. The moon and the sun have both been

photographed repeatedly, and with most instructive results. The first

good pictures of the moon were made by Dr. John W. Draper of New York

City, in March, 1840. His son, Dr. Henry Draper, succeeded him in this

work, and his photographs were considered the best until Rutherfurd

began his remarkable work in 1865. After this, much important work

was done in the Lick observatory, and elsewhere. The first picture of

the sun was taken in 1845, by Fizeau and Foucault, on a daguerreotype

plate. Sun spots, total eclipses, etc., are now studied in great detail

by this means.









THE TIDES





Every particle of matter attracts every other particle of matter

throughout the entire Universe. The Sun and the Moon both exert a

definite pull upon the earth; the moon particularly, being the earth’s

satellite, is (so to say) held in place by the earth. The moon,

exerting this definite pull, naturally influences the water of the

earth most of all, because water is a fluid, mobile body. A heaping-up

of the water then occurs--“high tide.” But the moon also attracts the

earth to some extent; and the consequence of this is that the water

on the opposite side of the globe is, as it were, left behind, which

causes a heaping-up of the water there also. Hence, there are two high

tides daily, with an interval of 12 hours between them, on opposite

sides of the globe.



When the sun and moon pull together, we have the highest tides--“spring

tides.” When they do not pull together (being in different parts of the

heavens) we have only the surplus pull of the moon over the sun, and

the tides are consequently not so high. These are the “neap tides.” All

tides act as a sort of check or brake upon the rotation of the earth on

its axis--tending to slow down its speed to some extent. “Tidal waves”

are due to a combination of special causes.









GRAVITATION





The mysterious influence or “pull” which various celestial bodies

exert upon one another is known as gravity or gravitation. We know

that masses of matter attract one another according to their size;

the larger the body, the greater the force exerted, etc. Further, the

influence decreases according to a definite law--according to the

square of the distance between the two bodies. The innermost nature

of gravitation is still largely a mystery--though various ingenious

theories have been advanced in order to explain it. (See my article

in “The Monist,” for July, 1913, and pp. 44-46 of “New Discoveries

in Science” in the present series.) Gravitation is supposed to act

throughout the whole Universe, so that all celestial bodies mutually

influence one another, to some extent. Its speed, mode or action, etc.,

as well as its essence or true nature are, however, unknown even yet;

they are still unsolved mysteries!









THE ETHER





At all events, gravitation is thought to act through, or by means of,

the Ether--the nature of which is still another mystery! Lodge, in his

“Ether of Space,” has given some interesting figures as to the enormous

strain which the ether must be supposed to transmit or carry. Lack

of space, however, prevents a further discussion of this interesting

question; a brief summary may be found on pp. 53-55 of my book on

“Chemistry for Beginners,” in the series of Blue Books. For our present

purposes, it need only be said that the ether is the only hypothetical

connecting-link between celestial bodies--since there is no air or

atmosphere in interstellar space. And it is across or by means of this

ether that gravitation must be exerted.









ATOMIC ANALOGIES





Recent investigations of the innermost structure of the atom have

shown us that it is probably constituted on very much the same plan

as our solar system--a central “sun” or proton, round which revolve

the negative planets or “electrons.” This question I have treated more

fully in my “Chemistry for Beginners,” pp. 42-44, to which the reader

is referred.









THUNDER AND LIGHTNING





The lightning flash is merely a huge electric spark, such as may

be seen between the terminals of any electric machine. In cases of

flashes, or forked lightning, this “spark” is seen directly. Sheet

lightning is observed when the original flash is hidden behind clouds,

and only its reflection or effects are seen. The rumbling of thunder is

due to the reverberations and echoes of the original “peal.” The peal

is thought to be due to the sudden rushing together of the molecules of

the upper atmosphere, which have been rent asunder by the flash--a sort

of vacuum created. Camille Flammarion has written an interesting book

on “Thunder and Lightning,” which may be consulted for further details.









FIREBALLS





These are virtually the same as “shooting stars” (_q.v._,) and no

essential difference can be pointed to, as to their origin or nature.

They are not mere “blobs” of lightning, but solid bodies which

sometimes burst, with a great noise--though they are usually noiseless.

Many of them appear to be pear-shaped, but they may be seen to change

their size and shape during the period of visibility. Fireballs are

often accompanied by a train of sparks.









ATMOSPHERIC ELECTRICITY





The surface of the earth is constantly charged with negative

electricity of a static character. The upper atmosphere is usually

charged positively, though, this may vary according to circumstances.

The earth and upper air thus resemble two sheets of tin-foil, with

the air an imperfect dialectric between them. This may be broken

down, especially in wet or damp weather. The effects upon the mental

and physical health are often very noticeable (see Dexter: “Weather

Influences,” etc.)









THE EARTH’S MAGNETISM





It has long been known that the magnetic pole does not coincide with

the North Pole (or South Pole). The compass points to the magnetic

north pole, and not to the true north pole. Lines of magnetic force

seem to envelop the earth, terminating at the north and south poles,

respectively. Although this is purely a terrestrial phenomenon, it is

necessary to mention it here, since it has enabled us to explain, very

largely, the remarkable manifestation known as









THE AURORA BOREALIS





This is usually seen in northern climes, and the reason for this is

now clear. We know that the corpuscles discharged from a Crookes tube

are deflected by a magnet. These corpuscles are discharged in immense

numbers by the sun, and rain upon our earth. Now, the earth is a

magnet, and these corpuscles are caught by the lines of force girdling

our earth, and carried towards the poles, where they find themselves

in an atmosphere comparable with high vacua. They then begin to give

out the shifting and darting lights characteristic of the cathode rays,

causing a certain luminosity. These darting and shifting lights would,

on this theory, account for the Aurora Borealis--which is also known to

vary with the number of sun-spots.









TIME: MEASUREMENT OF:





Our divisions of time are purely arbitrary, and are all based upon

the revolution of our earth upon its axis, which thus constitutes

a gigantic clock. All other clocks, watches, etc., are adjusted

accordingly. This is really our only way of measuring time; subjective

feelings are very illusory, and have to be checked-up by other means.

The solar day is the basis of all our calculations--a month, a year,

etc., being only so many days in length. Our earth, therefore, is the

clock by which we measure the time of the Universe!









SPACE: MEASUREMENT OF:





The measurement of space is always a difficult problem, even for

near-by objects (see my “Psychology for Beginners”). When applied to

celestial bodies, it becomes immensely complicated, and the only wonder

is that such apparently accurate measurements have in fact been made!

Such measurements cannot, of course, ever be made _directly_, but must

depend upon trigonometry and abstruse mathematical calculations. Most

of them are based upon the following principles: If we observe a

distant object from two different points-of-view, at a known distance

apart, the angle formed by imaginary lines running from the object to

one position, and to the other, can readily be calculated. Knowing

this angle, much can be ascertained as to the size, distance, etc., of

the distant body. If a distant star be viewed from opposite sides of

the earth, we have here a known base-line of slightly more than 8,000

miles. But this is altogether too small for astronomical distances! A

much longer base-line must be sought. Accordingly, observations are

made of a distant star when the earth is (so to say) “north” of the

sun, and further observations of the same star when the earth is (so

to say) “south” of it--six months later, when the earth has traveled

half-way through its orbit round the sun. The diameter of the earth’s

orbit being known (186,000,000 miles, almost) we have here a base-line

of this size for use in our measurement of the angle and subsequent

calculations. Immense as this base-line is, however, it is too small

for our purposes, for so immense are astronomical distances, that _no

change whatever_ can be observed in the relative positions of certain

fixed stars--even when studied from such different positions in space!

In other words, the star is so far distant that, when viewed from two

positions in space, distant from one another nearly one hundred and

eighty-six million miles, it appears to occupy the same position! But a

mere summary of this question, and its details would involve an entire

volume in itself!









THE INTERNATIONAL DAY LINE





Inasmuch as our earth revolves on its axis, a new day is beginning

at some different moment all round the world. This being the case,

how are we to fix some definite and official “starting point” for our

day--since the day officially begins at midnight, and not at sunrise?

To determine this, an arbitrary International Day Line has been drawn,

on the 180th meridian--just half way round the globe from Greenwich.

Fortunately, this falls in the Pacific Ocean, where there is almost

no land. When the sun crosses this line, a new day begins. I have

explained this more fully in my book “New Discoveries in Science” in

the present series (pp. 40-42).









CALENDARS, ETC.





Our year is a little more than 365 days in length--in fact, nearly

365¼. Because of this fact, an extra day accumulates every four years;

and to include this we add this extra day to February every “leap

year.” In this way, our celestial bookkeeping is kept fairly accurate.

Twelve months of 30 days each would give 360 days, with five days over.

It was, however, found that five days was not enough, while five and a

quarter was too much. It is interesting to note that Hipparchus, who

flourished in the 2nd century B. C., worked on this problem, and fixed

5 days and 55 m., as the time required--a truly remarkable achievement,

since it has since been found to be accurate to within less than six

minutes.









CURVED SPACE





This, and various other problems connected with the Einstein theories

may be found treated in No. 408 of the present series, “An Introduction

to Einstein,” by William F. Hudgings.









THE TEMPERATURE OF SPACE





The Earth is warmed by the sun’s rays, some of which are absorbed,

while some are reflected. But these rays themselves possess no

“heat”; they are merely minute vibrations in the ether. Heat is only

present when they strike some solid body. Consequently the vast

inter-stellar spaces are tremendously cold--probably at or about

absolute zero (-273.10°C). Our earth is not heated directly, as a man

is heated by standing in front of a blazing fire; but only by means

of electro-magnetic undulations, which traverse millions of miles of

space, colder than death, without heating them!









LIGHT IN SPACE





Space is also intensely dark; no light exists there save the faint

twinklings of distant stars. The sun illumines our earth, because its

rays are reflected from its surface; but space itself is intensely

black, just as it is intensely cold It is a “cold world” indeed, once

we have stepped off the little planet on which we dwell!









LIFE IN SPACE





All this being so, life in any form cannot very well exist in

space--since the conditions for its existence are altogether absent.

Arrhenius has, however, suggested, that the “germs of life” might

possibly be carried across millions of miles of space on dust

particles, propelled by the energy of light. This, however, is a pure

theory, which has so far received no official proof.









THE CAUSES OF AN ICE AGE





We know that our Earth has passed through several ice ages, in the

past, and various astronomical theories have been advanced in order to

explain this fact. Perhaps the most ingenious of these is that advanced

by Sir Robert Ball (see his “The Cause of An Ice Age”). Very briefly,

it is that the eccentricity of the earth’s orbit and the tilting of

the polar axis causes an ice age, or the reverse. If the northern axis

is tilted towards the sun, when nearest to it (so to say), then the

northern hemisphere will enjoy a genial climate, and if the southern

axis be thus tilted, the reverse conditions will prevail. This, and

various other theories have, however, been discussed by Finger in his

book on “The Ice Age,” in the present series, No. 327.









WHY DO STARS “TWINKLE”?





When we look at a star near the horizon, we at once notice that it

twinkles, or “scintillates,” especially in the winter time. The

phenomenon is purely atmospheric, and is due to waves of air of unequal

density sweeping across the line of sight. When viewed through a

telescope, this is sometimes magnified into actual dancing.









WHY DOES THE MOON SOMETIMES APPEAR LARGER?





It is well known that the moon often appears larger when rising or

setting--i. e., near the horizon, than when it is overhead. The same

is true of the Sun. It is hardly necessary to say that these celestial

bodies have not _actually_ increased or decreased in size! Why, then,

should we perceive them larger at some times than at others?



The reason for this is two-fold; psychological and optical. In the

first place, the Heavens do not appear to us quite round, but somewhat

flattened out, like a watch-glass. Hence the moon appears to be much

further away when it rises than it does when it is overhead, with

nothing between. The moon near the horizon is apparently larger because

it seems further away. The second reason is that the refraction of the

earth’s atmosphere gives this illusion of increased size.









ARE THE PLANETS INHABITED?





This is a much-disputed point! Various astronomers (Schiaparelli,

Lowell, etc.) have contended that they have almost indubitable evidence

that Mars is inhabited by living beings like ourselves; other

equally competent astronomers assert the contrary. Certainly, none

of the planets of our own solar system, with the possible exceptions

of Mars and Venus, could possibly be inhabited. That is universally

granted. And we have no _direct_ evidence of any other inhabited

worlds throughout space. Analogy, however, forces us to believe that,

of the millions of suns blazing in the heavens, many of them must be

attended by a planetary system such as ours; and if such be the case,

there is no reason why life should not originate and thrive thereon as

well as upon our own planet. We have, however, no means of proving or

disproving this directly.



In our own system, Venus and particularly Mars offer possibilities.

Venus probably always turns one face towards the sun, so that this

side would be tremendously hot, while the other side would be frozen

in perpetual ice. Mars is a possibility; and, as we know, great

controversy has raged regarding the habitability of this planet, and

as to its “Canals.” The interested reader may refer to Lowell’s “Mars

as the Abode of Life,” and “Mars and Its Canals” for the affirmative,

and to Maunder’s “Are the Planets Inhabited?” for the negative, side of

this question.









A FEW DEFINITIONS





What “Parallax” means. Since the earth revolves round the sun, the

stars are apparently in slightly different directions from it at

different times of the year. The difference in direction of a star as

seen from two points on the earth’s orbit which are separated by the

mean distance to the sun is the _parallax_ of the star. In other words,

the parallax of a star is the angle subtended by the major semi-axis of

the earth’s orbit, as seen from the star.



The “Orbit” of a moving body is its more or less circular passage

through space, usually around another larger body, as our earth

revolves round the sun. The “eccentricity” of the orbit consists in the

fluctuations or variations from its exact path.



The “Ecliptic” System. If we could see the stars near the sun, we

should find that the Sun apparently moves eastward among them,

completing one revolution in a year. Tracing such a path, it will be

found that it more or less coincides with the celestial equator. The

equator and the ecliptic intersect at two points; these points are the

“equinoxes” the _vernal_ equinox being the one at which the sun crosses

the equator from south to north, and the _autumnal_ equinox the other

one.



“Satellites.” These are smaller bodies which revolve round large ones,

and, so to say, attend them. All except two of the planets are known

to have satellites revolving round them, just as they revolve round

the sun. Mercury and Venus have none; the earth has the moon; Mars has

two little moons, only a few miles in diameter; Jupiter has four large

satellites and four small ones; Saturn has ten, one of which is larger

than Mercury; Uranus has four satellites, and Neptune one.



The “Planetoids.” Between Mars and Jupiter a number of small bodies

have been discovered, moving in a regular orbit; these have been

called planetoids. If some planet has once occupied this mid-way

position, and subsequently exploded, the fragments would occupy the

position occupied by the planetoids. Whether or not this is their

origin is a disputed point, which it would take us too far afield to

consider here. They suggest the possibility.



“Planets.” These are the bodies revolving round a central sun. Aside

from those constituting our own solar system, we see no planets in

space; we see suns, or stars; but if the latter have planets attendant

upon them, we cannot see them.



The point of the moon’s orbit nearest the earth is called the

_perigee_; the furthest point, the _apogee_.









TRANSCRIBER’S NOTES





Author’s spelling of “dialectric” has been retained.



Inconsistencies in hyphenation have been left unchanged.



Typos corrected:



Title page: missing opening quote in “Psychology for Beginners”



Page 13: “concenses” to “consensus”



Page 17: “equitorial” to “equatorial”, "Myriads" to "myriads"

(lowercase)



Page 49: “on my book” to “of my book”



Page 54: “litle” to “little”



Page 59: “Unanus” to “Uranus”