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<v Speaker 1>Section nineteen of Sun, Moon and Stars Astronomy for Beginners.

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<v Speaker 1>This is a LibriVox recording. All LibriVox recordings are in

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<v Speaker 1>the public domain. For more information or to volunteer, please

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<v Speaker 1>visit LibriVox dot org. Read by Donald Warren, Sun Moon

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<v Speaker 1>and Stars Astronomy for Beginners by Agnes Guyburn, Uranus and Neptune.

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<v Speaker 1>He hath showed his people the power of his works

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<v Speaker 1>Psalms one eleven six. Till the year seventeen eighty one,

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<v Speaker 1>Saturn was believed to be the outermost planet of the

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<v Speaker 1>Solar System, and nobody suspected the fact of two great

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<v Speaker 1>lonely brother planets traveling around the same Sun at vast

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<v Speaker 1>distances beyond Uranus nine hundred millions of miles from Saturn

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<v Speaker 1>Neptune one thousand millions of mine ailes from Uranus. No

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<v Speaker 1>wonder they remained long undiscovered. Uranus can sometimes be seen

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<v Speaker 1>by the unaided eye as a dim star of the

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<v Speaker 1>sixth magnitude, And when he was known for a planet,

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<v Speaker 1>it was found that he had been often so seen

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<v Speaker 1>and noted again and again. He had been taken for

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<v Speaker 1>a fixed star, And as he moved and disappeared from

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<v Speaker 1>that particular spot. It was supposed that the star had vanished.

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<v Speaker 1>One night, when Herschel was busy exploring with a powerful telescope,

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<v Speaker 1>he noticed something which he took for a comet without

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<v Speaker 1>a tail. He saw it was no mere point light

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<v Speaker 1>like the stars, but had a tiny round disc or

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<v Speaker 1>face which could be magnified. So he watched it carefully

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<v Speaker 1>and found in the course of a few nights that

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<v Speaker 1>it moved very slowly, certainly, but it did move. Further.

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<v Speaker 1>Watching and calculations made it clear that though the newly

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<v Speaker 1>found heavenly body was at a great distance from the Sun,

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<v Speaker 1>yet it was moving slowly in orbit around the Sun.

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<v Speaker 1>Then it was known to be a planet and another

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<v Speaker 1>member of the Solar System. Everybody supposed that now at

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<v Speaker 1>least the outermost member of all was discovered. But a

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<v Speaker 1>very strange and remarkable thing happened. Astronomers know with great

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<v Speaker 1>exactness the paths of the planets in the heavens. They

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<v Speaker 1>can tell years beforehand precisely what spot in space will

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<v Speaker 1>be filled at any particular time by any particular planet.

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<v Speaker 1>I am speaking now of their movements around the Sun

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<v Speaker 1>and in the Solar System, not of the movements of

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<v Speaker 1>the whole family with the Sun, about which little is

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<v Speaker 1>yet known. Each planet has its own particular pathway, its

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<v Speaker 1>own particular distance from the Sun, varying at each part

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<v Speaker 1>of its pathway, its own particular speed in traveling around

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<v Speaker 1>the Sun, changing constantly from faster to slower, or slower

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<v Speaker 1>to faster, according to its distance from the Sun, and

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<v Speaker 1>according to the pull backwards or forwards of other neighboring

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<v Speaker 1>planets in front or in rear. For as the orbits

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<v Speaker 1>of all the planets are ovals, with the Sun not

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<v Speaker 1>in the middle, but somewhat to one side of the middle,

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<v Speaker 1>it follows that all the planets, in the course of

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<v Speaker 1>their years, are sometimes nearer to and sometimes farther from

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<v Speaker 1>the Sun. The astronomers of the present day understand this well,

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<v Speaker 1>and can describe with exactness the pathway of each planet.

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<v Speaker 1>This knowledge does not come merely from watching one year

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<v Speaker 1>how the planets travel, and remember for another year, but

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<v Speaker 1>is much more a matter of close and difficult calculation.

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<v Speaker 1>It seems to be the will of God to govern

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<v Speaker 1>commonly things in the heavens, as he governs commonly things

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<v Speaker 1>upon Earth, by certain regular laws of working laws of nature.

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<v Speaker 1>We call them though laws of God would perhaps be

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<v Speaker 1>a truer expression and reach higher. There was a great

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<v Speaker 1>astronomer named Kepler who discovered some of the wonderful laws

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<v Speaker 1>by which God governs the movements of the planets in

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<v Speaker 1>their orbits. Kepler's three laws are often spoken about, by

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<v Speaker 1>which is meant three laws of God's working in nature

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<v Speaker 1>discovered by Kepler. Before these laws and others were understood,

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<v Speaker 1>the movements of the planets for a constant puzzle. Now

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<v Speaker 1>that they have been clearly grasped, astronomers cannot only perceive,

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<v Speaker 1>as it were, the plan of all the planet's journeys,

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<v Speaker 1>but can draw out beforehand a scheme or sketch according

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<v Speaker 1>to these laws, telling exactly what the pathway of any

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<v Speaker 1>one planet is sure to be. Many things have to

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<v Speaker 1>be considered, such as the planet's distance from the Sun,

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<v Speaker 1>the Sun's power of attraction, the planet's speed, the nearness

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<v Speaker 1>and weight of other neighboring planets. All these questions were

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<v Speaker 1>gone into and astronomers sketched out the pathway in the

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<v Speaker 1>heavens which they expected Uranus to follow. He would move

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<v Speaker 1>in such and such an orbit, at such and such

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<v Speaker 1>distance from the Sun, and at such and such rates

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<v Speaker 1>of speed. But Uranus would not keep to these rules.

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<v Speaker 1>He quite discomfited the astronomers. Sometimes he went fast, and,

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<v Speaker 1>according to their notions, ought to have gone more slowly.

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<v Speaker 1>And sometimes he went slowly when they would have looked

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<v Speaker 1>for him to go more fast, And the line of

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<v Speaker 1>his orbit was quite outside the line of the orbit

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<v Speaker 1>which they had laid down. He was altogether a perplexing

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<v Speaker 1>acquaintance and difficult to understand. However, astronomers felt sure of

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<v Speaker 1>their rules and modes of calculation so often before tested

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<v Speaker 1>and not found to fail. They made a guess at

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<v Speaker 1>an explanation. What if there were yet another planet beyond

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<v Speaker 1>Uranus disturbing his motions, now drawing him on, now drawing

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<v Speaker 1>him back, now so far balancing the Sun's attraction by

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<v Speaker 1>pulling in the opposite direction as to increase the distance

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<v Speaker 1>of Uranus from the Sun. It might be so, yet

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<v Speaker 1>who could prove it? Hundreds of years might pass before

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<v Speaker 1>any astronomer in his stargazing should happen to light upon

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<v Speaker 1>such a dim and distant world. Nay, the supposed planet

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<v Speaker 1>might be like Uranus actually seen, and only be mistaken

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<v Speaker 1>for a variable star shining. But to disappear there. The

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<v Speaker 1>matter seemed likely to rest there. The matter probably would

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<v Speaker 1>have rested for a good while had not Two men

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<v Speaker 1>set themselves to conquer the difficulty. One was a young Englishman,

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<v Speaker 1>John Couch Adams, the other a young Frenchman Leviere, both

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<v Speaker 1>being astronomers, each work independently of the other, neither knowing

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<v Speaker 1>of the other's toil. The task which they had undertaken

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<v Speaker 1>was no light one, that of reaching out into the

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<v Speaker 1>unknown depths of space the fine and unknown planet. Each

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<v Speaker 1>of these silent searchers into the sky depths calculated that

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<v Speaker 1>the orbit and speed of Uranus would be without the

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<v Speaker 1>presence of another disturbing planet beyond. Each examined what the

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<v Speaker 1>amount of disturbance was, and considered the degree of attraction

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<v Speaker 1>needful to produce that disturbance, together with the direction from

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<v Speaker 1>which it had come. Each, in short, gradually worked his

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<v Speaker 1>way through calculations far too deep and difficult for ordinary

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<v Speaker 1>minds to grasp, till he had found just that spot

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<v Speaker 1>in the heavens where a planet ought to be, to cause,

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<v Speaker 1>according to known laws, just such an effort upon Uranus,

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<v Speaker 1>as had been observed. Adams finished his calculations first and

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<v Speaker 1>sent the results to two different observatories. Unfortunately, his report

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<v Speaker 1>was not eagerly taken up. It was, in fact hardly believed.

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<v Speaker 1>Lavier finished his calculations also and sent the result to

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<v Speaker 1>the Berlin observatory. The planet was actually seen in England first,

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<v Speaker 1>but the discovery was actually made known from Berlin first.

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<v Speaker 1>The young Englishman had been beforehand, but the young Frenchmen

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<v Speaker 1>gained foremost honor. This, however, was of slight comparative importance.

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<v Speaker 1>The truly wonderful part of the matter was that these

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<v Speaker 1>two men could have so reason that from the movements

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<v Speaker 1>of one lately discovered planet, they could point out the

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<v Speaker 1>exact spot where a yet more distant planet ought to be,

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<v Speaker 1>and that close to this very spot the planet was found.

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<v Speaker 1>Or that when both in England and in Germany, powerful

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<v Speaker 1>telescopes were pointed in the direction named there, the planet

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<v Speaker 1>was no doubt about the matter. Not a star, but

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<v Speaker 1>a real new planet in the far distance, wandering slowly

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<v Speaker 1>around the Sun. This was indeed a triumph of human intellect.

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<v Speaker 1>Yet it is no matter for human pride, but rather

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<v Speaker 1>of thankfulness to Him who gave to man his marvelous

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<v Speaker 1>reasoning power, and the very delight we have in such

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<v Speaker 1>a success may humble us in the recollection of the

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<v Speaker 1>vast amount lying beyond the utterly known. Perhaps the chief

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<v Speaker 1>feeling of satisfaction in this particular discovery may be said

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<v Speaker 1>to arise from the fact that it gives marked and

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<v Speaker 1>strong proof of the truth of our present astronomical system

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<v Speaker 1>and beliefs. Many mistakes may be made, and much has

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<v Speaker 1>often to be unlearned. Nevertheless, if the general principles of

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<v Speaker 1>modern astronomy were wrong, if the commonly received facts were

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<v Speaker 1>a delusion, such complete success could not have attended so

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<v Speaker 1>delicate and difficult a calculation. We do not know much

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<v Speaker 1>about these two outer planets, owing to their enormous distance

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<v Speaker 1>from us. Uranus is in size equal to sixty four earths,

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<v Speaker 1>and Neptunism in size somewhat larger than Uranus. Both of

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<v Speaker 1>these planets are formed of decidedly heavier materials than Saturn,

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<v Speaker 1>being about as dense as water. The size of the

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<v Speaker 1>Sun as seen from Uranus is about one three hundred

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<v Speaker 1>and ninetieth part of the size the Sun we see.

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<v Speaker 1>To Neptune, he shows a disk only one nine hundredth

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<v Speaker 1>part of the size of that visible to us. No

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<v Speaker 1>disk at all, in fact, but only starlike brilliancy to

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<v Speaker 1>any such eyes as ours. The Uranian year lasts about

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<v Speaker 1>eighty four of our years, and this with a very

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<v Speaker 1>sloping axis, must cause most long and dreary winters, the

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<v Speaker 1>tiny sun being hidden from parts of the planet during

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<v Speaker 1>half an earthly lifetime. Uranus has at least four moons,

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<v Speaker 1>traveling in very different plains from the plane of the elliptic.

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<v Speaker 1>Once it was thought that he had eight, but astronomers

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<v Speaker 1>have since searched in vain for the other four, believed

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<v Speaker 1>for a while to exist. Neptune has one moon and

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<v Speaker 1>may possess others not yet discovered. End of section nineteen