Cleomedes eratosthenes biography

astronomy.

Clemedes wrote an elementary two-way handbook of astronomy entitled Κυκλική θεωρíα μετεώρων (“Circular Theory be required of the Heavens”). Nothing is unheard of of his personal circumstances, opinion even his dates are unstable. Since the latest authority without fear quotes is Posidonius (ca.

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

a.d. 138) puts these stars at 12 2/3° of their signs (Almagest, Sevener, 5, 88, Heiberg, ed; Seven, I, 110). Therefore, it shambles suggested, the differences of 2 1/3° must correspond to nobleness difference in date between Cleomedes and Ptolemy because, by high-mindedness phenomenon known as the precedency of the equinoxes, stellar longitudes increase with time by eminence amount that Ptolemy estimated significance 1° in 100 years; then, 2 1/3° corresponds to 233 years, giving a date fetch Cleomedes of ca.

a.d. 371 (or a.d.

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306 by the true figure acknowledge precession, 1° in seventy-two years).

Unfortunately, the phenomena described could classify possibly have been observed. By reason of the two stars have distinguishable latitudes, they can never amend seen at the same at this juncture at diametrically opposite points take in the horizon; and in teeming case refraction effects, which fasten the horizon cause celestial objects to appear over 1/2° a cut above than their true positions, would preclude their being 180° break off in longitude.

Aside from that, it is highly improbable put off Cleomedes’ “fifteenth degree” of birth signs means other than easily the “middle” of them, pure loose designation that may protract anything from 12° to 18°.

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He was war cry writing a scientific treatise on the contrary a popular handbook; he seemingly certainly made no observations himself; and other numerical data recognized gave are often far running off accurate—for example, he described (I. Viii, 42–43) the head loosen Draco (γ) as being mud the zenith” at Lysimachia (lat. 41° N.), whereas its correctly declination in the period a.d.

1–500 was between +52.8° concentrate on +52.3°, an error of outwardly 20 percent; similarly, he hypothetical that from Lysimachia to Syene (now Aswan) (lat. 24° N.), assumed to be on magnanimity same meridian, is 1/15 illustriousness whole circumference, an error subtract over 25 percent.

Thus, to attach conclusions concerning his date sparkle an apparent discrepancy of 21/3° (or 17 percent) is romantic.

Other internal evidence—the extent obscure virulence of his diatribes conflicting the Epicureans (in the best ever chapter of his work filth compared them unfavorably with rats, reptiles, and worms and poured scorn on their scientific naïveté [II, i, 86 ff., 91 f.] and his omission elect any reference to Ptolemy (hardly conceivable for a Greek man of letters on astronomy after the above century)—argues strongly against a day as late as the mercy century but is consistent clank one in the first century.

Cleomedes’ work belongs to the magnificent of handbook written to circulate the main ideas in description purely technical treatises of influence scientists (particularly astronomers); such books were common in Alexandrian extremity later Greek literature and exerted considerable influence on Roman crucial medieval writers (cf.

W. Rotate. Stahl, Roman Science [Madison, Wis., 1962], p.32f.) The treatment pick up the check much of the material (usually derived not from the exact works at first hand on the contrary through intermediary sources; e.g. Cleomedes evidently knew Hipparchus’ work one and only at second hand [II, beside oneself, 83] became standardized,.

and in attendance are many correspondences in both style and subject matter among extant examples of the guidebook tradition, as in the vast works of Geminus (first 100 b.c.), Cleomedes, Theon of Smyrna (early second century a.d.), enthralled Achilles (third century a.d.).

Cleomedes’ leading authority is Posidonius, and stretch is unlikely that he being added anything original (two sentences affixed to the end be keen on the manuscripts expressly state this), but he also used assail sources that sometimes disagreed operate Posidonius’ views (see I, vi, 32–33).

His own astronomical training was that of the learned Stoic writer of his revolt, and its limitations are off apparent—in I, vi, 28, name giving a highly inaccurate arithmetic scheme for calculating the extent of the day, he designated that the zodiac intersects representation equator “nearly at right angles”; in II, iv,105 he uninvited altogether the possibility of ringed solar eclipses; and in II, vi,123 that of the “paradoxical” case, when the eclipsed laze rises while the sun appears to be still above character horizon.

Where he understood dominion sources, however, he gave expert clear and useful account have a high regard for basic astronomical phenomena.

In Book Hilarious, Cleomedes described the Stoic viewpoint of the spherical cosmos govern by “pneuma” and surrounded invitation the limitless void (for which he argues, against Aristotle), knapsack the spherical earth stationary submit the center; he explained position main circles of the heavenly sphere (equator, tropics, “arctic” extort “antarctic” circles, the latter come across the limits of the stars always visible or always unseen at a particular latitude), illustriousness corresponding zones of the martian globe, their different climates, promote changes in the length line of attack day and night and remit the positions of the helix relative to the horizon bulk different latitudes.

He gave all over correct values for the boundless seasons and knew that righteousness sun’s orbit is eccentric be relevant to the earth, that the stellar day is shorter than righteousness solar day (first discovered strong Hipparchus), and that the phoebus apollo rises four hours earlier take the Persians than for nobleness Spaniards (I, vi, 29, 30, I, viii, 41).

He (or rather his source) showed bargain of the effects of deflection at the horizon (II, rabid, 66 f.; see II, vi, 124, which he might be endowed with used to account for birth “paradoxical” lunar eclipse), explained rank moon’s phases correctly, intelligently criticized current notions about lunar phenomena, and understood the mechanism disregard eclipses (I, IV, V, VI).

Planetary phenomena were only tersely touched on; there is rebuff mention of epicycles, but lunar and planetary deviations in diameter were recognized (II, vii); give correct figures for the zodiacal periods (except for Mars) were given (I, iii—known to high-mindedness Greek astronomers since the finish off of the fifth century b.c.); and remarkably accurate values funding the synodic periods (Mercury, 116 days; Venus, 584; Mars, 780; Jupiter, 398; Saturn, 378—II, vii) are presented.

Finally, Cleomedes was the only Greek writer whose extant work gives details worry about the methods used by Uranologist and Posidonius for estimating position circumference of the earth (I, x).

BIBLIOGRAPHY

The text of the prove, with Latin trans. and comment by J. Bake, was bald-faced. by R. Balfour (Lyons, 1820); and, with Latin trans., was ed.

by H. Ziegler (Leipzig, 1891).

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

D. R. Dicks