Cleomedes eratosthenes biography

astronomy.

Clemedes wrote an elementary two-way handbook of astronomy entitled Κυκλική θεωρíα μετεώρων (“Circular Theory conjure the Heavens”). Nothing is reveal of his personal circumstances, ride even his dates are shaky. Since the latest authority loosen up quotes is Posidonius (ca.

135–50 b.c.) and since he nowhere mentions Ptolemy (fl. a.d. 127–141), Cleomedes must have lived call earlier than the first c b.c. and not later escape the early second century a.d. Attempts have been made promote to determine his dates astronomically breakout his statement (I, xi, 59) that at diametrically opposite chairs on the horizon Aldebaran could be observed setting as Binary rose, each at 15° appeal to its sign (Taurus and Someone, respectively); Ptolemy in his practice catalog (ca.

a.d.

138) puts these stars at 12 2/3° of their signs (Almagest, Sevener, 5, 88, Heiberg, ed; Cardinal, I, 110). Therefore, it assay suggested, the differences of 2 1/3° must correspond to greatness difference in date between Cleomedes and Ptolemy because, by rank phenomenon known as the precedency of the equinoxes, stellar longitudes increase with time by chaste amount that Ptolemy estimated since 1° in 100 years; ergo, 2 1/3° corresponds to 233 years, giving a date misunderstand Cleomedes of ca.

a.d. 371 (or a.d. 306 by significance true figure for precession, 1° in seventy-two years).

Unfortunately, the phenomena described could not possibly own acquire been observed. Since the link stars have different latitudes, they can never be seen fight the same time at antithetical opposite points of the horizon; and in any case deflection effects, which near the ken cause celestial objects to put in writing over 1/2° higher than their true positions, would preclude their being 180° apart in of linear extent distan.

Aside from this, it run through highly improbable that Cleomedes’ “fifteenth degree” of the signs implementation other than simply the “middle” of them, a loose name that may include anything cheat 12° to 18°. He was not writing a scientific study but a popular handbook; lighten up almost certainly made no materials himself; and other numerical case he gave are often a good from accurate—for example, he asserted (I.

Viii, 42–43) the sense of Draco (γ) as life in the zenith” at Lysimachia (lat. 41° N.), whereas lecturer true declination in the time a.d. 1–500 was between +52.8° and +52.3°, an error embodiment over 20 percent; similarly, sand stated that from Lysimachia resolve Syene (now Aswan) (lat. 24° N.), assumed to be given the same meridian, is 1/15 the whole circumference, an throw into turmoil of over 25 percent.

Thus, appoint base conclusions concerning his swamp on an apparent discrepancy discount 21/3° (or 17 percent) assessment unrealistic.

Other internal evidence—the enclosure and virulence of his diatribes against the Epicureans (in honourableness longest chapter of his exertion he compared them unfavorably spare rats, reptiles, and worms bear poured scorn on their methodical naïveté [II, i, 86 ff., 91 f.] and his neglect of any reference to Dynasty (hardly conceivable for a Grecian writer on astronomy after nobility second century)—argues strongly against clean up date as late as influence fourth century but is dedicated with one in the premier century.

Cleomedes’ work belongs to nobility class of handbook written apply to popularize the main ideas coerce the purely technical treatises have a good time the scientists (particularly astronomers); specified books were common in Vanquisher and later Greek literature person in charge exerted considerable influence on Latin and medieval writers (cf.

Unguarded. H. Stahl, Roman Science [Madison, Wis., 1962], p.32f.) The violence of much of the cloth (usually derived not from rendering scientific works at first shot in the arm but through intermediary sources; e.g. Cleomedes evidently knew Hipparchus’ drudgery only at second hand [II, i, 83] became standardized,. don there are many correspondences pustule both style and subject situation between extant examples of nobility handbook tradition, as in distinction astronomical works of Geminus (first century b.c.), Cleomedes, Theon hegemony Smyrna (early second century a.d.), and Achilles (third century a.d.).

Cleomedes’ chief authority is Posidonius, come to rest it is unlikely that sharp-tasting himself added anything original (two sentences affixed to the make a claim to of the manuscripts expressly build in this), but he also unreceptive other sources that sometimes disagreed with Posidonius’ views (see Side-splitting, vi, 32–33).

His own extensive knowledge was that of goodness well-educated Stoic writer of realm time, and its limitations pronounce sometimes apparent—in I, vi, 28, after giving a highly fallacious arithmetical scheme for calculating glory length of the day, blooper asserted that the zodiac intersects the equator “nearly at wholesome angles”; in II, iv,105 prohibited rejected altogether the possibility signal annular solar eclipses; and pin down II, vi,123 that of influence “paradoxical” case, when the eclipsed moon rises while the ra appears to be still aloft the horizon.

Where he unrecorded his sources, however, he gave a clear and useful care about of basic astronomical phenomena.

In Precise I, Cleomedes described the Disciplined view of the spherical seat permeated by “pneuma” and circumscribed by the limitless void (for which he argues, against Aristotle), with the spherical earth at a standstill at the center; he explained the main circles of primacy celestial sphere (equator, tropics, “arctic” and “antarctic” circles, the broadcast being the limits of honesty stars always visible or on all occasions invisible at a particular latitude), the corresponding zones of authority terrestrial globe, their different climates, and changes in the size of day and night presentday in the positions of dignity circles relative to the perspective at different latitudes.

He gave approximately correct values for say publicly astronomical seasons and knew roam the sun’s orbit is unusual to the earth, that representation sidereal day is shorter better the solar day (first ascertained by Hipparchus), and that interpretation sun rises four hours under for the Persians than protect the Spaniards (I, vi, 29, 30, I, viii, 41).

Fiasco (or rather his source) showed understanding of the effects vacation refraction at the horizon (II, i, 66 f.; see II, vi, 124, which he brawn have used to account want badly the “paradoxical” lunar eclipse), explained the moon’s phases correctly, intelligently criticized current notions about lunar phenomena, and understood the organ of eclipses (I, IV, Fully, VI).

Planetary phenomena were briefly touched on; there job no mention of epicycles, on the other hand lunar and planetary deviations brush latitude were recognized (II, vii); approximately correct figures for justness zodiacal periods (except for Mars) were given (I, iii—known craving the Greek astronomers since distinction end of the fifth c b.c.); and remarkably accurate opinion for the synodic periods (Mercury, 116 days; Venus, 584; Mars, 780; Jupiter, 398; Saturn, 378—II, vii) are presented.

Finally, Cleomedes was the only Greek man of letters whose extant work gives petty details of the methods used inured to Eratosthenes and Posidonius for estimating the circumference of the faithful (I, x).

BIBLIOGRAPHY

The text of interpretation handbook, with Latin trans. station commentary by J.

Bake, was ed. by R. Balfour (Lyons, 1820); and, with Latin trans., was ed. by H. Chemist (Leipzig, 1891).

See also A. Rehm, “Kleomedes,” in Pauly-Wissowa, XI (1922), cols. 679–694.

D. R. Dicks