Hipparchus

“ It is easy to overestimate the influence of any single man, and, contrariwise, to underestimate the power of the Zeitgeist. But when we reflect that the doctrines of Hipparchus, as promulgated by Ptolemy, became, as it were, the last word of astronomical science for both the Eastern and Western worlds, and so continued after a thousand years, it is perhaps not too much to say that Hipparchus, "the lover of truth," missed one of the greatest opportunities for the promulgation of truth ever vouchsafed to a devotee of pure science. ”

“ Hipparchus and Ptolemy entertained the same large organic designs; they worked on similar methods; and, as the outcome, Hipparchus. their performances fitted so accurately together that between them they re-made celestial science. Hipparchus fixed the chief data of astronomy—the lengths of the tropical and sidereal years, of the various months, and of the synodic periods of the five planets; determined the obliquity of the ecliptic and of the moon’s path, the place of the sun’s apogee, the eccentricity of his orbit, and the moon’s horizontal parallax ”

“ Another citizen, Aristogiton, had reasons of his own for wishing ill to Hipparchus: he stimulated his friend Harmodius to a keener sense of the injury, and they resolved to [170] wash away their wrongs in blood. But few associates were admitted to the knowledge of their plot, which was to be executed at the Panathenaic festival, when it was usual for all persons to appear in arms. Hipparchus alone was personally offensive; but to dissolve the tyranny, and to secure themselves from retribution, Hippias was to be involved in his brother’s fate. ”

“ Rather than to disturb my tranquil mood;
But, as the Fates determined, it was seen. —
Suddenly, running round the dovecote, came
A young man naked, breathless, through the dawn,
Florid with haste and wine; it was Hipparchus. ”

“ Hipparchus was the author of other great discoveries and improvements in astronomy, besides the establishment of the Doctrine of Eccentrics and Epicycles; but this, being the greatest advance in the theory of the celestial motions which was made by the ancients, must be the leading subject of our attention in the present work; our object being to discover in what the progress of real theoretical knowledge consists, and under what circumstances it has gone on. ”

“ Delambre doubted, and most subsequent writers follow him here, whether Hipparchus ever so much as visited Alexandria. In any event there seems to be no question that Rhodes may claim the honor of being the chief site of his activities.
It was Hipparchus whose somewhat equivocal comment on the work of Eratosthenes we have already noted. No counter-charge in kind could be made against the critic himself; he was an astronomer pure and simple. His gift was the gift of accurate observation rather than the gift of imagination. ”

“ He also pointed out how longitude might be determined by observing the eclipses of the sun and moon. This led to the construction of maps; but none have reached us except those which were used to illustrate the geography of Ptolemy. Hipparchus was born B.C. 276, the first who raised geography to the rank of a science. He starved himself to death, being tired of life, like Eratosthenes, more properly an astronomer, and the most distinguished among the ancients, born about 160 B.C., although none of his writings have reached us. ”

“ When the new splendour dies out again, it is not that a star has ceased to exist; but simply that a faint star which had increased greatly in lustre has resumed its original condition. Hipparchus's star must have been a remarkable object, for it was visible in full daylight, whence we may infer that it was many times brighter than the blazing Dog-star. It is interesting in the history of science, as having led Hipparchus to draw up a catalogue of stars, the first on record. ”

“ EXPULSION OF THE TYRANTS FROM ATHENS (510 B.C.) .—The two sons of Pisistratus, Hippias and Hipparchus, succeeded to his power. At first they emulated the example of their father, and Athens flourished under their parental rule. But at length an unfortunate event gave an entirely different tone to the government. Hipparchus, having insulted a young noble, was assassinated. Hippias escaped harm, but the event caused him to become suspicious and severe. His rule now became a tyranny indeed, and was brought to an end in the following way. ”

“ Hipparchus was the first among the Greeks who observ'd some Change in the Constellations with regard to the Equinoxes, or rather who learnt it from the Egyptians. Philosophers ascrib'd this Motion to the Stars; for in those Ages People were far from imagining such a Revolution in the Earth, which was suppos'd to be immoveable in every respect. ”

“ In the first place, the statement that Lycurgus obtained the poems from descendants of Creophylus must be admitted to be purely mythical. But if we reject it, have we any better reason for believing the parallel assertion in the Platonic Hipparchus? It is true that Hipparchus is undoubtedly a real person. On the other hand it is evident that the Peisistratidae soon became the subject of many fables. Thucydides notices as a popular mistake the belief that Hipparchus was the eldest son of Peisistratus, and that consequently he was the reigning “tyrant” when he was killed by Aristogiton. ”

“ There are few better illustrations of genuine scientific caution than the way in which Hipparchus, having tested the planetary theories handed down to him and having discovered their insufficiency, deliberately abstained from building up a new theory on data which he knew to be insufficient, and patiently collected fresh material, never to be used by himself, that some future astronomer might thereby be able to arrive at an improved theory. ”

“ Modern science offers an explanation of the phenomenon, as we shall see in due course. We do not know that Hipparchus attempted to explain it, but he was led to make a chart of the heavens, probably with the idea of guiding future observers in the observation of new stars. Here again Hipparchus was not altogether an innovator, since a chart showing the brightest stars had been made by Eratosthenes ”

“ He carried out both Hipparchus's plan of determining latitude and longitude by astronomical observations, and that of representing the earth by the modern method of projection—with the "curved meridians and parallels" which Strabo had despised. We can see from the errors which he makes that he did not fully understand Hipparchus's ideas, but he did measurably; and he had the energy to stamp his knowledge upon the world, and thereby became the master of geography. ”

“ Aratus was no astronomer, while Hipparchus was; and from the fact that the latter adopted, with but trifling exceptions, the constellation system portrayed by Aratus, it may be concluded that the system was already familiar in Greek thought. And three hundred years after Hipparchus, the Alexandrian astronomer Ptolemy adopted a very similar scheme in his uranometria, which appears in the seventh and eighth books of his Almagest, the catalogue being styled the Ἔκθεσις κανονική or “accepted version.” ”

“ In habits of thought and scientific aims the contrast between Pythagoras and Hipparchus is probably greater than that between Hipparchus on the one hand and Coppernicus or even Newton on the other, while it is not unfair to say that the fanciful ideas which pervade the work of even so great a discoverer as Kepler (chapter vii., §§ 144, § 151) place his scientific method in some respects behind that of his great Greek predecessor. ”

“ This has been done by Hipparchus, who has noted down (as he says) the differences of the heavenly appearances for every degree of that quarter of the globe in which our habitable earth is situated, namely, from the equator to the north pole.
What is beyond our habitable earth it is not however the business of the geographer to consider. Nor yet even in regard to the various parts of the habitable earth must too minute and numerous differences be noticed, since to the man of the world they are perplexing; it will suffice to give the most striking and simple of the statements of Hipparchus. ”

“ In the application of astronomy to geography, he followed Hipparchus principally, and he seems from his residence at Alexandria to have derived much information through the merchants and navigators of that city, as well as from its magnificent and valuable library. His great work, as it has reached us, consists almost entirely of an elementary picture of the earth, (if it may be so called,) in which its figure and size, and the position of places are determined. There is only a short notice of the division of countries, and it is very seldom that any historical notice is added. ”

“ Hipparchus inherited his father's literary tastes. He invited several distinguished poets, such as Anacreon and Simonides, to his court. The people appear to have been contented with their rule; and it was only an accidental circumstance which led to their overthrow and to a change in the government.
Their fall was occasioned by the conspiracy of Harmodius and Aristogiton, who were attached to each other by a most intimate friendship. Harmodius having given offence to Hippias, the despot revenged himself by putting a public affront upon his sister. ”

“ Fourteen years had thus passed in peace and prosperity, when Hipparchus gave serious offense to a citizen named Harmo ́dius, who thereupon united with his friend Aristogi ́ton in a plot to murder the two tyrants. Hipparchus was slain. Hippias saved himself by promptness and presence of mind; but from that day his character was changed. His most intimate friends had been accused by the conspirators as concerned in the plot, and executed. Though the charge was false and made only for revenge, the suspicions of Hippias never again slept. ”

“ Amongst the Greeks, Hipparchus [A6] deserves particular notice; by an improvement of whose labours Ptolemy formed that system of astronomy which appears to have been the only one studied for ages after, and particularly (as was said before) by the Arabians; who made some improvements of their own, and, if not the inventors, were at least the preservers of astronomy. For with them it took refuge, during those ages of ignorance which involved Europe, after an inundation of northern people had swallowed up the Roman empire ”

“ Hippias being their despot and growing ever bitterer in enmity against the Athenians by reason of Hipparchus’ death, the Alcmeonidae, a family of Athenian stock banished by the sons of Pisistratus, essayed with the rest of the banished Athenians to make their way back by force and free Athens, but could not prosper in their return and rather suffered great hurt. ”

“ Of my household furniture let so much as the executors think right be given to Pompylus and let the rest be sold. I also devise Carion to Demotimus, and Donax to Neleus. But Euboeus must be sold. Let Hipparchus pay to Callinus 3000 drachmas. And if I had not seen that Hipparchus had done great service to Melantes and Pancreon and formerly to me, and that now in his private affairs he has made shipwreck, I would have appointed him jointly with Melantes and Pancreon to carry out my wishes. ”

“ Another measurement due to Eratosthenes was that of the obliquity of the ecliptic, which he estimated at 22/83 of a right angle, or 23° 51', the error in which is only about 7'.
37. An immense advance in astronomy was made by Hipparchus, whom all competent critics have agreed to rank far above any other astronomer of the ancient world, and who must stand side by side with the greatest astronomers of all time. ”

“ As the star of Hipparchus announced the extinction of the Greek ascendency and the rise of the Roman empire, so the star of 1572 is the forerunner of vast changes, not only in politics, but also in religious affairs, for the star was situated close to the equinoctial colure, which by astrologers is supposed to have something to do with religious matters. ”

“ His catalogue of the stars is preserved in the Almagest of Ptolemy; and his commentary on Aratus and Eudoxus is still extant.
Such is a brief sketch of the advantages which geography, as founded on astronomy, derived from the labours of Hipparchus. We possess little information respecting his ideas of the form of the earth, or the relative position or extent of the different quarters and countries on the surface of the globe. ”

“ Ptolemy, in his Almagest, states nothing whatever as to how the time was found when the numerous astronomical phenomena which he records took place; but Hipparchus, in the only book we possess from his hand, gives a list of 44 stars scattered over the sky at intervals of right ascension equal to exactly one hour, so that one or more of them would be on the meridian at the commencement of every sidereal hour. ”

“ They say, then, that Hipparchus the Pythagorean, being guilty of writing the tenets of Pythagoras in plain language, was expelled from the school, and a pillar raised for him as if he had been dead. Wherefore also in the Barbarian philosophy they call those dead who have fallen away from the dogmas, and have placed the mind in subjection to carnal passions. "For what fellowship hath righteousness and iniquity?" according to the divine apostle. ”

“ Hipparchus, a hundred years after Aristotle, calculated the length of the year to within six minutes, discovered the precession of equinoxes and counted all the stars he could see, making a map of them.
Seventy years after Christ, Ptolemy, a Greco-Egyptian, but not of the royal line of Ptolemies, published his great book, "The Almagest." For over fourteen centuries it was the textbook for the best astronomers. ”