Speaker 1: Section nineteen of Sun, Moon and Stars Astronomy for Beginners.
Speaker 1: This is a LibriVox recording. All LibriVox recordings are in
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Speaker 1: and Stars Astronomy for Beginners by Agnes Guyburn, Uranus and Neptune.
Speaker 1: He hath showed his people the power of his works
Speaker 1: Psalms one eleven six. Till the year seventeen eighty one,
Speaker 1: Saturn was believed to be the outermost planet of the
Speaker 1: Solar System, and nobody suspected the fact of two great
Speaker 1: lonely brother planets traveling around the same Sun at vast
Speaker 1: distances beyond Uranus nine hundred millions of miles from Saturn
Speaker 1: Neptune one thousand millions of mine ailes from Uranus. No
Speaker 1: wonder they remained long undiscovered. Uranus can sometimes be seen
Speaker 1: by the unaided eye as a dim star of the
Speaker 1: sixth magnitude, And when he was known for a planet,
Speaker 1: it was found that he had been often so seen
Speaker 1: and noted again and again. He had been taken for
Speaker 1: a fixed star, And as he moved and disappeared from
Speaker 1: that particular spot. It was supposed that the star had vanished.
Speaker 1: One night, when Herschel was busy exploring with a powerful telescope,
Speaker 1: he noticed something which he took for a comet without
Speaker 1: a tail. He saw it was no mere point light
Speaker 1: like the stars, but had a tiny round disc or
Speaker 1: face which could be magnified. So he watched it carefully
Speaker 1: and found in the course of a few nights that
Speaker 1: it moved very slowly, certainly, but it did move. Further.
Speaker 1: Watching and calculations made it clear that though the newly
Speaker 1: found heavenly body was at a great distance from the Sun,
Speaker 1: yet it was moving slowly in orbit around the Sun.
Speaker 1: Then it was known to be a planet and another
Speaker 1: member of the Solar System. Everybody supposed that now at
Speaker 1: least the outermost member of all was discovered. But a
Speaker 1: very strange and remarkable thing happened. Astronomers know with great
Speaker 1: exactness the paths of the planets in the heavens. They
Speaker 1: can tell years beforehand precisely what spot in space will
Speaker 1: be filled at any particular time by any particular planet.
Speaker 1: I am speaking now of their movements around the Sun
Speaker 1: and in the Solar System, not of the movements of
Speaker 1: the whole family with the Sun, about which little is
Speaker 1: yet known. Each planet has its own particular pathway, its
Speaker 1: own particular distance from the Sun, varying at each part
Speaker 1: of its pathway, its own particular speed in traveling around
Speaker 1: the Sun, changing constantly from faster to slower, or slower
Speaker 1: to faster, according to its distance from the Sun, and
Speaker 1: according to the pull backwards or forwards of other neighboring
Speaker 1: planets in front or in rear. For as the orbits
Speaker 1: of all the planets are ovals, with the Sun not
Speaker 1: in the middle, but somewhat to one side of the middle,
Speaker 1: it follows that all the planets, in the course of
Speaker 1: their years, are sometimes nearer to and sometimes farther from
Speaker 1: the Sun. The astronomers of the present day understand this well,
Speaker 1: and can describe with exactness the pathway of each planet.
Speaker 1: This knowledge does not come merely from watching one year
Speaker 1: how the planets travel, and remember for another year, but
Speaker 1: is much more a matter of close and difficult calculation.
Speaker 1: It seems to be the will of God to govern
Speaker 1: commonly things in the heavens, as he governs commonly things
Speaker 1: upon Earth, by certain regular laws of working laws of nature.
Speaker 1: We call them though laws of God would perhaps be
Speaker 1: a truer expression and reach higher. There was a great
Speaker 1: astronomer named Kepler who discovered some of the wonderful laws
Speaker 1: by which God governs the movements of the planets in
Speaker 1: their orbits. Kepler's three laws are often spoken about, by
Speaker 1: which is meant three laws of God's working in nature
Speaker 1: discovered by Kepler. Before these laws and others were understood,
Speaker 1: the movements of the planets for a constant puzzle. Now
Speaker 1: that they have been clearly grasped, astronomers cannot only perceive,
Speaker 1: as it were, the plan of all the planet's journeys,
Speaker 1: but can draw out beforehand a scheme or sketch according
Speaker 1: to these laws, telling exactly what the pathway of any
Speaker 1: one planet is sure to be. Many things have to
Speaker 1: be considered, such as the planet's distance from the Sun,
Speaker 1: the Sun's power of attraction, the planet's speed, the nearness
Speaker 1: and weight of other neighboring planets. All these questions were
Speaker 1: gone into and astronomers sketched out the pathway in the
Speaker 1: heavens which they expected Uranus to follow. He would move
Speaker 1: in such and such an orbit, at such and such
Speaker 1: distance from the Sun, and at such and such rates
Speaker 1: of speed. But Uranus would not keep to these rules.
Speaker 1: He quite discomfited the astronomers. Sometimes he went fast, and,
Speaker 1: according to their notions, ought to have gone more slowly.
Speaker 1: And sometimes he went slowly when they would have looked
Speaker 1: for him to go more fast, And the line of
Speaker 1: his orbit was quite outside the line of the orbit
Speaker 1: which they had laid down. He was altogether a perplexing
Speaker 1: acquaintance and difficult to understand. However, astronomers felt sure of
Speaker 1: their rules and modes of calculation so often before tested
Speaker 1: and not found to fail. They made a guess at
Speaker 1: an explanation. What if there were yet another planet beyond
Speaker 1: Uranus disturbing his motions, now drawing him on, now drawing
Speaker 1: him back, now so far balancing the Sun's attraction by
Speaker 1: pulling in the opposite direction as to increase the distance
Speaker 1: of Uranus from the Sun. It might be so, yet
Speaker 1: who could prove it? Hundreds of years might pass before
Speaker 1: any astronomer in his stargazing should happen to light upon
Speaker 1: such a dim and distant world. Nay, the supposed planet
Speaker 1: might be like Uranus actually seen, and only be mistaken
Speaker 1: for a variable star shining. But to disappear there. The
Speaker 1: matter seemed likely to rest there. The matter probably would
Speaker 1: have rested for a good while had not Two men
Speaker 1: set themselves to conquer the difficulty. One was a young Englishman,
Speaker 1: John Couch Adams, the other a young Frenchman Leviere, both
Speaker 1: being astronomers, each work independently of the other, neither knowing
Speaker 1: of the other's toil. The task which they had undertaken
Speaker 1: was no light one, that of reaching out into the
Speaker 1: unknown depths of space the fine and unknown planet. Each
Speaker 1: of these silent searchers into the sky depths calculated that
Speaker 1: the orbit and speed of Uranus would be without the
Speaker 1: presence of another disturbing planet beyond. Each examined what the
Speaker 1: amount of disturbance was, and considered the degree of attraction
Speaker 1: needful to produce that disturbance, together with the direction from
Speaker 1: which it had come. Each, in short, gradually worked his
Speaker 1: way through calculations far too deep and difficult for ordinary
Speaker 1: minds to grasp, till he had found just that spot
Speaker 1: in the heavens where a planet ought to be, to cause,
Speaker 1: according to known laws, just such an effort upon Uranus,
Speaker 1: as had been observed. Adams finished his calculations first and
Speaker 1: sent the results to two different observatories. Unfortunately, his report
Speaker 1: was not eagerly taken up. It was, in fact hardly believed.
Speaker 1: Lavier finished his calculations also and sent the result to
Speaker 1: the Berlin observatory. The planet was actually seen in England first,
Speaker 1: but the discovery was actually made known from Berlin first.
Speaker 1: The young Englishman had been beforehand, but the young Frenchmen
Speaker 1: gained foremost honor. This, however, was of slight comparative importance.
Speaker 1: The truly wonderful part of the matter was that these
Speaker 1: two men could have so reason that from the movements
Speaker 1: of one lately discovered planet, they could point out the
Speaker 1: exact spot where a yet more distant planet ought to be,
Speaker 1: and that close to this very spot the planet was found.
Speaker 1: Or that when both in England and in Germany, powerful
Speaker 1: telescopes were pointed in the direction named there, the planet
Speaker 1: was no doubt about the matter. Not a star, but
Speaker 1: a real new planet in the far distance, wandering slowly
Speaker 1: around the Sun. This was indeed a triumph of human intellect.
Speaker 1: Yet it is no matter for human pride, but rather
Speaker 1: of thankfulness to Him who gave to man his marvelous
Speaker 1: reasoning power, and the very delight we have in such
Speaker 1: a success may humble us in the recollection of the
Speaker 1: vast amount lying beyond the utterly known. Perhaps the chief
Speaker 1: feeling of satisfaction in this particular discovery may be said
Speaker 1: to arise from the fact that it gives marked and
Speaker 1: strong proof of the truth of our present astronomical system
Speaker 1: and beliefs. Many mistakes may be made, and much has
Speaker 1: often to be unlearned. Nevertheless, if the general principles of
Speaker 1: modern astronomy were wrong, if the commonly received facts were
Speaker 1: a delusion, such complete success could not have attended so
Speaker 1: delicate and difficult a calculation. We do not know much
Speaker 1: about these two outer planets, owing to their enormous distance
Speaker 1: from us. Uranus is in size equal to sixty four earths,
Speaker 1: and Neptunism in size somewhat larger than Uranus. Both of
Speaker 1: these planets are formed of decidedly heavier materials than Saturn,
Speaker 1: being about as dense as water. The size of the
Speaker 1: Sun as seen from Uranus is about one three hundred
Speaker 1: and ninetieth part of the size the Sun we see.
Speaker 1: To Neptune, he shows a disk only one nine hundredth
Speaker 1: part of the size of that visible to us. No
Speaker 1: disk at all, in fact, but only starlike brilliancy to
Speaker 1: any such eyes as ours. The Uranian year lasts about
Speaker 1: eighty four of our years, and this with a very
Speaker 1: sloping axis, must cause most long and dreary winters, the
Speaker 1: tiny sun being hidden from parts of the planet during
Speaker 1: half an earthly lifetime. Uranus has at least four moons,
Speaker 1: traveling in very different plains from the plane of the elliptic.
Speaker 1: Once it was thought that he had eight, but astronomers
Speaker 1: have since searched in vain for the other four, believed
Speaker 1: for a while to exist. Neptune has one moon and
Speaker 1: may possess others not yet discovered. End of section nineteen