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these changes? The sun was ever round and I rilliant -the stars shone with undimmed splendor-while the moon was ever waxing and waning, sometimes a silver crescent hanging in the western sky, or full orbed, walking in majesty among the stars, and eclipsing their radiance, with her overwhelming splendor. Scarcely had the second observation been made upon the moon, when the obseryer was struck with the wonderful fact, that she had left her place among the fixed stars, which on the preceding night he had accurately marked. Astonished, he again fixes her place by certain bright stars close to her position, and waits the coming of the following night. His suspi cions are confirmed—the moon is moving; and what to him is far more wonderful, her motion is precisely contrary to the general revolution of the heavens, from east to west. With a curiosity deeply aroused, he watches from night to night, to learn, whether she will return upon her track; but she marches steadily onward among the stars, until she sweeps the entire circuit of the heavens, and returns to the point first occupied, to recommence her ceaseless cycles.
An inquiry now arose, whether the changes in the moon, her increase and decrease, could in any way depend on her place among the fixed stars. To solve this question, required a longer period. The group of stars among which the new moon was first seen was accurately noted, so as to be recognized at the following new moon, and doubtless our primitive astronomer hoped to find that in this same group the silver crescent, when it should next appear, would be found. But in this he was disappointed; for when the moon became first faintly visible in the western
sky, the group of stars which had ushered her in be. fore, had disappeared below the horizon, and a new group had taken its place; and thus it was discovered that each successive new moon fell farther and farther backward among the stars. By counting the days from new moon to new moon, and those which elapsed while the moon was passing round the heavens from a certain fixed star to this same star again, it was found, that these two periods were different; the revolution from new to new occupying 294 days, while the sidereal revolution, from star to star, required 27} days.
This backward motion of the moon among the stars, must have perplexed the early astronomers; and for a long while it was utterly impossible to decide whether the motion was real or only apparent-analogy would lead to the conclusion that all motion must be in the same direction, and as the heavens revolved from east to west, it seemed impossible that the moon, which manifestly participated in this general movement, should have another and a different motion, from west to east. There was one solution of this mystery, and I have no doubt it was for a long while accepted and believed. It was this. By giving to the moon á slower motion from east to west, than the general motion of the heavens, she would appear to lag behind the stars, which would by their swifter velocity pass by her, and thus occasion in her the observed apparent motion, from west to east. We shall see presently how this error was detected.
The long and accurate vigils of the moon, and the necessity of recognizing her place, by the clusters or groups of stars among which she was nightly found
had already familiarized the eye with those along her track, and even thus early the heavens began to be di vided into constellations. The eye was not long in detecting the singular fact, that this stream of constellations, lying along the moon's path, was constantly flowing to the west, and one group after another ap parently dropping into the sun, or at least becoming invisible, in consequence of their proximity to this brilliant orb. A closer examination revealed the fact, that the aspect of the whole heavens was changing from month to month. Constellations which had been conspicuous in the west, and whose brighter stars were the first to appear as the twilight faded, were found to sink lower and lower towards the horizon, till they were no longer seen; while new groups were constantly appearing in the east.
These wonderful changes, so strange and inexplicable, must have long perplexed the early student of the heavens. Hitherto the stars, along the moon's route, had engaged special attention ; but at length certain bright and conspicuous constellations, towards the north, arrested the eye: and these were watched to see whether they would disappear.–Some were found to dip below the western horizon, soon to re-appear in the east; while others revolving with the general heavens, rose high above the horizon, swept steadily round, sunk far down, but never disappeared from the sight. This remarkable discovery soon led to another equally important. In watching the stars in the north through an entire night, they all seemed to describe circles ; having a common centre, these circles grew smaller and smaller as the stars approached nearer 10 the centre of revolution, until finally one bright star was found, whose position was ever fixed.--Alone un. changed while all else was slowly moving. The dis- . covery of this remarkable star, must have been hailed with uncommon delight by the primitive observer of the heavens. If his deep devotion to the study of the skies, had created surprise among his rude countrymen, when he came to point them to this never change ing light hung up in the heavens, and explained its uses in guiding their wanderings on the earth, their sur prise must have given place to admiration. Here war the first valuable gift of primitive astronomical science to man.
But to the astronomer this discovery opened up a new field of investigation, and light began to dawn on some of the most mysterious questions which had long perplexed him. He had watched the constellations near the moon's track slowly disappear in the effulgence of the sun, and when they were next seen, it was in the east, in the early dawn, apparently emerging from the solar beams, having actually passed by the sun. Watching and reflecting, steadily pursuing the march of the northern constellations, which never entirely disappeared, and noting the relative positions of these, and those falling into the sun, it was at last discovered that the entire starry heavens was slowly moving forward to meet and pass by the sun, or else the sun itself was actually moving backward among the stars. This apparent motion had already been detected in the moon, and now came the reward of long and diligent perseverance. The grand discovery was made, that both the sun and moon were moving among the fixed stars, not apparently, but absolutely. The previously received explanation of the mood': motion, could no longer be sustained; for the starry heavens could not at the same time so move as to pass by the moon in one month, and to pass by the sun in a period twelve times as great. A train of the most important conclusions flowed at once from this great discovery. The starry heavens passed beneath and around the earth, the sun and moon were wandering in the same direction, but with different velocities among the stars,— the constellations actually filled the entire heavens above the earth and beneath the earth,
- the stars were invisible in the day time, not because they did not exist, but because their feeble light was lost in the superior brilliancy of the sun. The heavens were spherical, and encompassed like a shell the entire earth, and hence it was conceived that the earth itself was also a globe, occupying the centre of the starry sphere.
It is impossible for us, familiar as we are at this day with these important truths, to appreciate the rare merit of him who by the power of his genius, first rose to their knowledge and revealed them to an astonished world. We delight to honor the names of Kepler, of Galileo, of Newton; but here are discoveries so far back in the dim past, that all trace of their origin is lost, which vie in interest and importance with the proudest achievements of any age.
With a knowledge of the sphericity of the heavens, the revolution of the sun and moon, the constellations of the celestial sphere, the axis of its diurnal revolution, astronomy began to be a science, and its future progress was destined to be rapid and brilliant. A line drawn from the earth's centre to the north star formed the axis of the heavens, and day and night around this axis all the celestial host were noiselessly pursuing