Recreations in Astronomy.

by Henry Warren.

PREFACE.

All sciences are making an advance, but Astronomy is moving at the double-quick. Since the principles of this science were settled by Copernicus, four hundred years ago, it has never had to beat a retreat. It is rewritten not to correct material errors, but to incorporate new discoveries.

Once Astronomy treated mostly of tides, seasons, and telescopic aspects of the planets; now these are only primary matters. Once it considered stars as mere fixed points of light; now it studies them as suns, determines their age, size, color, movements, chemical const.i.tution, and the revolution of their planets. Once it considered s.p.a.ce as empty; now it knows that every cubic inch of it quivers with greater intensity of force than that which is visible in Niagara.

Every inch of surface that can be conceived of between suns is more wave-tossed than the ocean in a storm.

The invention of the telescope const.i.tuted one era in Astronomy; its perfection in our day, another; and the discoveries of the spectroscope a third--no less important than either of the others.

While nearly all men are prevented from practical experimentation in these high realms of knowledge, few [Page viii] have so little leisure as to be debarred from intelligently enjoying the results of the investigations of others.

This book has been written not only to reveal some of the highest achievements of the human mind, but also to let the heavens declare the glory of the Divine Mind. In the author's judgment, there is no gulf that separates science and religion, nor any conflict where they stand together. And it is fervently hoped that anyone who comes to a better knowledge of G.o.d's works through reading this book, may thereby come to a more intimate knowledge of the Worker.

I take great pleasure in acknowledging my indebtedness to J. M.

Van Vleck, LL.D., of the U.S. Nautical Almanac staff, and Professor of Astronomy at the Wesleyan University, for inspecting some of the more important chapters; to Dr. S. S. White, of Philadelphia, for telescopic advantages; to Professor Henry Draper, for furnishing, in advance of publication, a photograph of the sun's corona in 1878; and to the excellent work on "Popular Astronomy," by Professor Simon Newcomb, LL.D., Professor U. S. Naval Observatory, for some of the most recent information, and for the use of the unequalled engravings of Jupiter, Saturn, and the great nebula of Orion.

I.

CREATIVE PROCESSES.

"In the beginning G.o.d created the heaven and the earth. And the earth was without form, and void; and darkness was upon the face of the deep."--_Genesis_ i. 1, 2.

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"Not to the domes, where crumbling arch and column Attest the feebleness of mortal hand, But to that fane, most catholic and solemn, Which G.o.d hath planned,-- To that cathedral, boundless as our wonder, Whose quenchless lamps the sun and stars supply; Its choir the winds and waves, its organ thunder, Its dome the sky." H. W. LONGFELLOW.

"The heavens are a point from the pen of His perfection; The world is a rose-bud from the bower of His beauty; The sun is a spark from the light of His wisdom; And the sky a bubble on the sea of His power."

SIR W. JONES.

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RECREATIONS IN ASTRONOMY.

I.

_CREATIVE PROCESSES._

During all the ages there has been one bright and glittering page of loftiest wisdom unrolled before the eye of man. That this page may be read in every part, man's whole world turns him before it.

This motion apparently changes the eternally stable stars into a moving panorama, but it is only so in appearance. The sky is a vast, immovable dial-plate of "that clock whose pendulum ticks ages instead of seconds," and whose time is eternity. The moon moves among the illuminated figures, traversing the dial quickly, like a second-hand, once a month. The sun, like a minute-hand, goes over the dial once a year. Various planets stand for hour-hands, moving over the dial in various periods reaching up to one hundred and sixty-four years; while the earth, like a ship of exploration, sails the infinite azure, bearing the observers to different points where they may investigate the infinite problems of this mighty machinery.

This dial not only shows present movements, but it keeps the history of uncounted ages past ready to be [Page 4] read backward in proper order; and it has glorious volumes of prophecy, revealing the far-off future to any man who is able to look thereon, break the seals, and read the record. Glowing stars are the alphabet of this lofty page. They combine to form words. Meteors, rainbows, auroras, shifting groups of stars, make pictures vast and significant as the armies, angels, and falling stars in the Revelation of St.

John--changing and progressive pictures of infinite wisdom and power.

Men have not yet advanced as far as those who saw the pictures John describes, and hence the panorama is not understood. That continuous speech that day after day uttereth is not heard; the knowledge that night after night showeth is not seen; and the invisible things of G.o.d from the creation of the world, even his eternal power and G.o.dhead, clearly discoverable from things that are made, are not apprehended.

The greatest triumphs of men's minds have been in astronomy--and ever must be. We have not learned its alphabet yet. We read only easy lessons, with as many mistakes as happy guesses. But in time we shall know all the letters, become familiar with the combinations, be apt at their interpretation, and will read with facility the lessons of wisdom and power that are written on the earth, blazoned in the skies, and pictured by the flowers below and the rainbows above.

In order to know how worlds move and develop, we must create them; we must go back to their beginning, give their endowment of forces, and study the laws of their unfolding. This we can easily do by that faculty wherein man is likest his Father, a creative imagination.

G.o.d creates and embodies; we create, but [Page 5] it remains in thought only. But the creation is as bright, strong, clear, enduring, and real, as if it were embodied. Every one of us would make worlds enough to crush us, if we could embody as well as create. Our ambition would outrun our wisdom. Let us come into the high and ecstatic frame of mind which Shakspeare calls frenzy, in the exigencies of his verse, when

"The poet's eye, in a fine frenzy rolling, Doth glance from heaven to earth, from earth to heaven; And, as imagination bodies forth The forms of things unknown, the poet's pen Turns them to shapes, and gives to airy nothing A local habitation and a name."

In the supremacy of our creative imagination let us make empty s.p.a.ce, in order that we may therein build up a new universe. Let us wave the wand of our power, so that all created things disappear.

There is no world under our feet, no radiant clouds, no blazing sun, no silver moon, nor twinkling stars. We look up, there is no light; down, through immeasurable abysses, there is no form; all about, and there is no sound or sign of being--nothing save utter silence, utter darkness. It cannot be endured. Creation is a necessity of mind--even of the Divine mind.

We will now, by imagination, create a monster world, every atom of which shall be dowered with the single power of attraction.

Every particle shall reach out its friendly hand, and there shall be a drawing together of every particle in existence. The laws governing this attraction shall be two. When these particles are a.s.sociated together, the attraction shall be in proportion to the ma.s.s. A given ma.s.s will pull twice [Page 6] as much as one of half the size, because there is twice as much to pull. And a given ma.s.s will be pulled twice as much as one half as large, because there is twice as much to be pulled. A man who weighed one hundred and fifty pounds on the earth might weigh a ton and a half on a body as large as the sun. That shall be one law of attraction; and the other shall be that ma.s.ses attract inversely as the square of distances between them. Absence shall affect friendships that have a material basis.

If a body like the earth pulls a man one hundred and fifty pounds at the surface, or four thousand miles from the centre, it will pull the same man one-fourth as much at twice the distance, one-sixteenth as much at four times the distance. That is, he will weigh by a spring balance thirty-seven and a half pounds at eight thousand miles from the centre, and nine pounds six ounces at sixteen thousand miles from the centre, and he will weigh or be pulled by the earth 1/24 of a pound at the distance of the moon. But the moon would be large enough and near enough to pull twenty-four pounds on the same man, so the earth could not draw him away. Thus the two laws of attraction of gravitation are--1, _Gravity is proportioned to the quant.i.ty of matter_; and 2, _The force of gravity varies inversely as the square of the distance from the centre of the attracting body_.

The original form of matter is gas. Almost as I write comes the announcement that Mr. Lockyer has proved that all the so-called primary elements of matter are only so many different sized molecules of one original substance--hydrogen. Whether that is true or not, let us now create all the hydrogen we can [Page 7] imagine, either in differently sized ma.s.ses or in combination with other substances.

There it is! We cannot measure its bulk; we cannot fly around it in any recordable eons of time. It has boundaries, to be sure, for we are finite, but we cannot measure them. Let it alone, now; leave it to itself. What follows? It is dowered simply with attraction. The vast ma.s.s begins to shrink, the outer portions are drawn inward.

They rush and swirl in vast cyclones, thousands of miles in extent.

The centre grows compact, heat is evolved by impact, as will be explained in Chapter II. Dull red light begins to look like coming dawn. Centuries go by; contraction goes on; light blazes in insufferable brightness; tornadoes, whirlpools, and tempests scarcely signify anything as applied to such tumultuous tossing.

There hangs the only world in existence; it hangs in empty s.p.a.ce.

It has no tendency to rise; none to fall; none to move at all in any direction. It seethes and, flames, and holds itself together by attractive power, and that is all the force with which we have endowed it.

Leave it there alone, and withdraw millions of miles into s.p.a.ce: it looks smaller and smaller. We lose sight of those distinctive spires of flame, those terrible movements. It only gives an even effulgence, a steady unflickering light. Turn one quarter round.

Still we see our world, but it is at one side.

Now in front, in the utter darkness, suddenly create another world of the same size, and at the same distance from you. There they stand--two huge, lone bodies, in empty s.p.a.ce. But we created them dowered with attraction. Each instantly feels the drawing influence of the other. They are mutually attractive, and begin to [Page 8]

move toward each other. They hasten along an undeviating straight line. Their speed quickens at every mile. The attraction increases every moment. They fly swift as thought. They dash their flaming, seething foreheads together.

And now we have one world again. It is twice as large as before, that is all the difference. There is no variety, neither any motion; just simple flame, and nothing to be warmed thereby. Are our creative powers exhausted by this effort?

[Ill.u.s.tration: Fig. 1.--Orbit A D, resulting from attraction, A C, and projectile force, A B.]

No, we will create another world, and add another power to it that shall keep them apart. That power shall be what is called the force of inertia, which is literally no power at all; it is an inability to originate or change motion. If a body is at rest, inertia is that quality by which it will forever remain so, unless acted upon by some force from without; and if a body is in motion, it will continue on at the same speed, in a straight line, forever, unless it is quickened, r.e.t.a.r.ded, or turned from its path by some other force. Suppose our newly created sun is 860,000 miles in diameter.

Go away 92,500,000 miles and create an earth eight thousand miles in diameter. It instantly feels the attractive power of the sun drawing it to itself sixty-eight [Page 9] miles a second. Now, just as it starts, give this earth a push in a line at right angles with line of fall to the sun, that shall send it one hundred and eighty-nine miles a second. It obeys both forces. The result is that the world moves constantly forward at the same speed by its inertia from that first push, and attraction momentarily draws it from its straight line, so that the new world circles round the other to the starting-point. Continuing under the operation of both forces, the worlds can never come together or fly apart.

They circle about each other as long as these forces endure; for the first world does not stand still and the second do all the going; both revolve around the centre of gravity common to both.

In case the worlds are equal in ma.s.s, they will both take the same orbit around a central stationary point, midway between the two.

In case their ma.s.s be as one to eighty-one, as in the case of the earth and the moon, the centre of gravity around which both turn will be 1/81 of the distance from the earth's centre to the moon's centre. This brings the central point around which both worlds swing just inside the surface of the earth. It is like an apple attached by a string, and swung around the hand; the hand moves a little, the apple very much.

Thus the problem of two revolving bodies is readily comprehended.

The two bodies lie in easy beds, and swing obedient to constant forces. When another body, however, is introduced, with its varying attraction, first on one and then on the other, complications are introduced that only the most masterly minds can follow. Introduce a dozen or a million bodies, and complications arise that only Omniscience can unravel.

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[Ill.u.s.tration: Fig. 2.]

Let the hand swing an apple by an elastic cord. When the apple falls toward the earth it feels another force besides that derived from the hand, which greatly lengthens the elastic cord. To tear it away from the earth's attraction, and make it rise, requires additional force, and hence the string is lengthened; but when it pa.s.ses over the hand the earth attracts it downward, and the string is very much shortened: so the moon, held by an elastic cord, swings around the earth. From its extreme distance from the earth, at A, Fig. 2, it rushes with increasing speed nearly a quarter of a million of miles toward the sun, feeling its attraction increase with every mile until it reaches B; then it is r.e.t.a.r.ded in its speed, by the same attraction, as it climbs back its quarter of a million of miles away from the sun, in defiance of its power, to C. All the while the invisible elastic force of the earth is unweariedly maintained; and though the moon's distances vary over a range of 31,355 miles, the moon is always in a determinable place.

A simple revolution of one world about another in a circular orbit would be a problem of easy solution. It would always be at the same distance from its centre, and going with the same velocity.