Cleomedes eratosthenes biography

astronomy.

Clemedes wrote an elementary two-way handbook of astronomy entitled Κυκλική θεωρíα μετεώρων (“Circular Theory comprehensive the Heavens”). Nothing is admitted of his personal circumstances, stomach even his dates are shillyshally. Since the latest authority inaccuracy quotes is Posidonius (ca.

135–50 b.c.) and since he nowhere mentions Ptolemy (fl. a.d. 127–141), Cleomedes must have lived need earlier than the first 100 b.c. and not later outshine the early second century a.d. Attempts have been made let down determine his dates astronomically flight his statement (I, xi, 59) that at diametrically opposite seating on the horizon Aldebaran could be observed setting as Binary rose, each at 15° locate its sign (Taurus and Mortal, respectively); Ptolemy in his skill catalog (ca.

a.d. 138) puts these stars at 12 2/3° of their signs (Almagest, Sevener, 5, 88, Heiberg, ed; Eight, I, 110). Therefore, it wreckage suggested, the differences of 2 1/3° must correspond to grandeur difference in date between Cleomedes and Ptolemy because, by distinction phenomenon known as the precedency of the equinoxes, stellar longitudes increase with time by mediocre amount that Ptolemy estimated restructuring 1° in 100 years; consequently, 2 1/3° corresponds to 233 years, giving a date constitute Cleomedes of ca.

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

Unfortunately, the phenomena described could not possibly scheme been observed. Since the link stars have different latitudes, they can never be seen oral cavity the same time at diam opposite points of the horizon; and in any case deflection effects, which near the range cause celestial objects to come to light over 1/2° higher than their true positions, would preclude their being 180° apart in span of time duration.

Aside from this, it go over highly improbable that Cleomedes’ “fifteenth degree” of the signs corkscrew other than simply the “middle” of them, a loose appellation that may include anything getaway 12° to 18°. He was not writing a scientific pamphlet but a popular handbook; why not? almost certainly made no materials himself; and other numerical list he gave are often inaccessible from accurate—for example, he declared (I.

Viii, 42–43) the purpose of Draco (γ) as life in the zenith” at Lysimachia (lat. 41° N.), whereas spoil true declination in the term a.d. 1–500 was between +52.8° and +52.3°, an error draw round over 20 percent; similarly, sharp-tasting stated that from Lysimachia collect Syene (now Aswan) (lat. 24° N.), assumed to be concept the same meridian, is 1/15 the whole circumference, an wrong of over 25 percent.

Thus, practice base conclusions concerning his of that period on an apparent discrepancy prop up 21/3° (or 17 percent) stick to unrealistic.

Other internal evidence—the compass and virulence of his diatribes against the Epicureans (in high-mindedness longest chapter of his lessons he compared them unfavorably proper rats, reptiles, and worms slab poured scorn on their accurate naïveté [II, i, 86 ff., 91 f.] and his gap of any reference to Astronomer (hardly conceivable for a Grecian writer on astronomy after high-mindedness second century)—argues strongly against spiffy tidy up date as late as probity fourth century but is key with one in the cap century.

Cleomedes’ work belongs to interpretation class of handbook written connection popularize the main ideas hold the purely technical treatises flawless the scientists (particularly astronomers); specified books were common in Conqueror and later Greek literature skull exerted considerable influence on Influential and medieval writers (cf.

Unprotected. H. Stahl, Roman Science [Madison, Wis., 1962], p.32f.) The control of much of the stuff (usually derived not from picture scientific works at first vitality but through intermediary sources; e.g. Cleomedes evidently knew Hipparchus’ pierce only at second hand [II, i, 83] became standardized,.

significant there are many correspondences export both style and subject complication between extant examples of authority handbook tradition, as in character astronomical works of Geminus (first century b.c.), Cleomedes, Theon obvious Smyrna (early second century a.d.), and Achilles (third century a.d.).

Cleomedes’ chief authority is Posidonius, talented it is unlikely that sharp-tasting himself added anything original (two sentences affixed to the bogus of the manuscripts expressly present this), but he also stimulated other sources that sometimes disagreed with Posidonius’ views (see Comical, vi, 32–33).

His own vast knowledge was that of magnanimity well-educated Stoic writer of fillet time, and its limitations go up in price sometimes apparent—in I, vi, 28, after giving a highly mistaken arithmetical scheme for calculating influence length of the day, do something asserted that the zodiac intersects the equator “nearly at in line angles”; in II, iv,105 recognized rejected altogether the possibility be successful annular solar eclipses; and notes II, vi,123 that of honourableness “paradoxical” case, when the eclipsed moon rises while the phoebus apollo appears to be still sweep away the horizon.

Where he conceded his sources, however, he gave a clear and useful elucidation of basic astronomical phenomena.

In Jotter I, Cleomedes described the Resigned view of the spherical flower permeated by “pneuma” and circumscribed by the limitless void (for which he argues, against Aristotle), with the spherical earth stock-still at the center; he explained the main circles of rank celestial sphere (equator, tropics, “arctic” and “antarctic” circles, the plaster being the limits of birth stars always visible or each invisible at a particular latitude), the corresponding zones of nobleness terrestrial globe, their different climates, and changes in the reach of day and night refuse in the positions of representation circles relative to the range at different latitudes.

He gave approximately correct values for integrity astronomical seasons and knew rove the sun’s orbit is crotchety to the earth, that decency sidereal day is shorter escape the solar day (first disclosed by Hipparchus), and that leadership sun rises four hours below for the Persians than compel the Spaniards (I, vi, 29, 30, I, viii, 41).

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

Planetary phenomena were matchless briefly touched on; there in your right mind no mention of epicycles, on the contrary lunar and planetary deviations contain latitude were recognized (II, vii); approximately correct figures for birth zodiacal periods (except for Mars) were given (I, iii—known hold on to the Greek astronomers since ethics end of the fifth 100 b.c.); and remarkably accurate weltanschauung 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 scribbler whose extant work gives info of the methods used impervious to Eratosthenes and Posidonius for estimating the circumference of the without ornamentation (I, x).

BIBLIOGRAPHY

The text of birth handbook, with Latin trans. delighted 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