Part 95

Astronomy, like the Christian religion, if you will allow me the comparison, has a much greater influence on our knowledge in general, and perhaps on our manners too, than is commonly imagined. Though but few men are its particular votaries, yet the light it affords is universally diffused amongst us; and it is difficult for us to divest ourselves of its influence so far, as to frame any competent idea of what would be our situation without it. Utterly ignorant of the heavens, our curiosity would be confined solely to the earth, which we should naturally suppose a vast extended plain; but whether of infinite extent or bounded, and if bounded, in what manner, would be questions admitting of a thousand conjectures, and none of them at all satisfactory.

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Footnote A11:

“Certain it is,” says the learned and pious Dr. Samuel Clarke (in his Discourse on the Evidences of Nat. and Rev. Religion,) “and this is a great deal to say, that the generality, even of the meanest and most vulgar and ignorant people,” (among Christians,) “have truer and worthier notions of God, more just and right apprehensions concerning his attributes and perfections, deeper sense of the difference of good and evil, a greater regard to moral obligations and to the plain and more necessary duties of life, and a more firm and universal expectation of a future state of rewards and punishments, than, in any heathen country, any considerable number of men were found to have had.”

In like manner, Archdeacon Paley (in his View of the Evidences of Christianity) observes:—“Christianity, in every country in which it is professed, has obtained a sensible, although not a complete influence, upon the public judgment of morals. And this is very important. For without the occasional correction which public opinion receives, by referring to some fixed standard of morality, no man can foretell into what extravagances it might wander.” “From the first general notification of Christianity to the present day,” says the same ingenious writer, “there have been in every age many millions, whose names were never heard of, made better by it, not only in their conduct, but in their dispositions; and happier, not so much in their external circumstances, as in that which is inter præcordia, in that which alone deserves the name of happiness, the tranquillity and consolation of their thoughts. It has been since its commencement, the author of happiness and virtue to millions and millions of the human race.” He then asks: “Who is there, that would not wish his son to be a Christian?” W. B.

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The first discovery then, which paved the way for others more curious, seems to have been the circular figure of the earth, inferred from observing the meridian altitudes of the sun and stars to be different in distant places. This conclusion would probably not be immediately drawn, but the appearance accounted for, by the rectilinear motion of the traveller; and then a change in the apparent situations of the heavenly bodies would only argue their nearness to the earth: and thus would the observation contribute to establish error, instead of promoting truth, which has been the misfortune of many an experiment. It would require some skill in geometry, as well as practice in observing angles, to demonstrate the spherical figure of the earth from such observations.

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Footnote A12:

Some of the commentators inform us, that Mahomet taught that the earth is supported by the tip of the horn of a prodigious ox, who stands on a huge white stone; and that it is the little and almost unavoidable motions of this ox which produce earthquakes.

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But this difficulty being surmounted, and the true figure of the earth discovered, a free space would now be granted for the sun, moon, and stars to perform their diurnal motions on all sides of it; unless perhaps at its extremities to the north and south; where something would be thought necessary to serve as an axis for the heavens to revolve on. This Mr. Crantz in his very entertaining history of Greenland informs us, is agreeable to the philosophy of that country, with this difference perhaps, that the high latitude of the Greenlander makes him conclude one pole only, necessary: He therefore supposes a vast mountain situate in the utmost extremity of Greenland, whose pointed apex supports the canopy of heaven, and whereon it revolves with but little friction.

A free space around the earth being granted, our infant astronomer would be at liberty to consider the diurnal motions of the stars as performed in intire circles, having one common axis of rotation. And by considering their daily anticipation in rising and setting, together with the sun’s annual rising and falling in its noon day height, swiftest about the middle space, and stationary for some time when highest and lowest, he would be led to explain the whole by attributing a slow motion to the sun, contrary to the diurnal motion, along a great circle dividing the heavens into two equal parts, but obliquely situated with respect to the diurnal motion. By a like attention to the moon’s progress the Zodiac would be formed, and divided into its several constellations or other convenient divisions.

The next step that astronomy advanced, I conceive, must have been in the discovery attributed to Pythagoras; who it is said first found out that Hesperus and Phosphorus, or the Evening and Morning Star, were the same. The superior brightness of this planet, and the swiftness of its motion, probably first attracted the notice of the inquisitive: and one wandering star being discovered, more would naturally be looked for. The splendor of Jupiter, the very changeable appearance of Mars, and the glittering of Mercury by day light, would distinguish them. And lastly, Saturn would be discovered by a close attention to the heavens. But how often would the curious eye be directed in vain, to the regions of the north and south, before there was reason to conclude that the orbits of all the planets lay nearly in the same plane; and that they had but narrow limits assigned them in the visible heavens.

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Footnote A13:

Pythagoras, who was one of the most celebrated among the Greek philosophers, in the knowledge and study of the heavens, was born about 540 years before the Christian era. It is believed that he was the first who made mention of the obliquity of the ecliptic, and of the angle which this circle makes with the equator; although Pliny attributes this discovery to Anaximander, whose birth was seventy years earlier. Among the remarkable things which Pythagoras taught his disciples, was the doctrine that fire, or heat, occupied the centre of the world; it is supposed he meant to say, that the sun is placed in the centre of the planetery system, and that the earth revolves around him, like the other planets. He also maintained each star to be a world; and that these worlds were distributed in an ethereal space of infinite extent. W. B.

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From a careful attendance to those newly discovered celestial travellers, and their various motions, direct and retrograde, the great discovery arose, that the sun is the centre of their motions; and that by attributing a similar motion to the earth, and supposing the sun to be at rest, all the phænomena will be solved. Hence a hint was taken that opened a new and surprizing scene. The earth might be similar to them in other respects. The planets too might be habitable worlds. One cannot help greatly admiring the sagacity of minds, that first formed conclusions so very far from being obvious; as well as the indefatigable industry of astronomers, who originally framed rules for predicting eclipses of sun and moon, which is said to have been done as early as the time of Thales; and must have proved of singular service to emancipate mankind from a thousand superstitious fears and notions, which juggling impostors (the growth of all ages and countries) would not fail to turn to their own advantage.

For two or three centuries before and after the beginning of the Christian era, astronomy appears to have been held in considerable repute; yet very few discoveries of any consequence were made, during that period and many ages following.

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Footnote A14:

Thales, who died about five centuries and an half before the Christian era, in the ninety-sixth year of his age, first taught the Greeks the cause of eclipses, He knew the spherical form of the earth; he distinguished the zones of the earth by the mean of the tropicks and the polar circles; and he treated of an oblique circle or zodiac, of a meridian which intersects all these circles in extending north and south, and of the magnitude of the apparent diameter of the sun.

Herodotus, Cicero, and Pliny, assert, as is noticed by Mr. Lalande, that Thales had predicted, to the Ionians a total eclipse of the sun, which took place during the war between the Lydians and the Medes, But the manner in which Herodotus (who lived about one century, only, after the time of Thales) speaks of this prediction, is so vague, that one finds some difficulty in believing that it was fact, If it were true, says Lalande, that Thales had actually foretold an eclipse of the sun, it could be no otherwise, than by means of the general period of eighteen years, of which he would have acquired a knowledge from the Egyptians or the Chaldeans: for the period had not yet arrived, when eclipses could be prognosticated by an exact calculation of the motion of the moon. W. B.

Footnote A14a:

But, according to Dufresnoy, he was born in the first year of the 35th Olympiad, and died the first year of the 52d, those periods corresponding, respectively, with the years 640 and 572, B. C.: and if so, he lived only sixty-eight years.

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The ancients were not wanting in their endeavours to find out the true dimensions of the planetary system. They invented several very ingenious methods for the purpose; but none of them were at all equal, in point of accuracy, to the difficulty of the problem. They were therefore obliged to rest satisfied with supposing the heavenly bodies much nearer to the earth than in fact they are, and consequently much less in proportion to it. Add to this, that having found the earth honoured with an attendant, while they could discover none belonging to any of the other planets, they supposed it of far greater importance in the Solar System than it appears to us to be: And the more praise is due to those few, who nevertheless conceived rightly of its relation to the whole.