ANCIENT HELLEENES ASTRONOMERS 3


(BEING CONTINUED FROM  6/06/18)

Aratus (/əˈreɪtəs/Greek: Ἄρατος ὁ Σολεύς; c. 315 BC/310 BC – 240) was a Greekdidacticpoet. His major extant work is his hexameter poem Phenomena (Ancient Greek: Φαινόμενα, Phainómena, “Appearances”; LatinPhaenomena), the first half of which is a verse setting of a lost work of the same name by Eudoxus of Cnidus. It describes the constellations and other celestial phenomena. The second half is called the Diosemeia (Διοσημεῖα “Forecasts”), and is chiefly about weather lore. Although Aratus was somewhat ignorant of Greek astronomy, his poem was very popular in the Greek and Roman world, as is proved by the large number of commentaries and Latin translations, some of which survive.

There are several accounts of Aratus’ life by anonymous Greek writers, and the Suda and Eudocia also mention him. From these it appears that he was a native of Soli[1] in Cilicia, (although one authority says Tarsus). He is known to have studied with Menecrates in Ephesus and Philitas in Cos. As a disciple of the Peripatetic philosopher Praxiphanes, in Athens, he met the Stoic philosopher Zeno, as well as Callimachus of Cyrene and Menedemus, the founder of the Eretrian school.

About 276 BC Aratus was invited to the court of the Macedonian king Antigonus II Gonatas, whose victory over the Gauls in 277 Aratus set to verse. Here he wrote his most famous poem, Phenomena. He then spent some time at the court of Antiochus I Soter of Syria, but subsequently returned to Pella in Macedon, where he died sometime before 240/239.[2][3]His chief pursuits were medicine (which is also said to have been his profession), grammar, and philosophy.

Several poetical works on various subjects, as well as a number of prose epistles, are attributed to Aratus, but none of them have come down to us, except his two astronomical poems in hexameter. These have generally been joined together as if parts of the same work; but they seem to be distinct poems, the first, called Phenomena (“Appearances”), consists of 732 verses; the second, Diosemeia (“On Weather Signs”), of 422 verses.

Phenomena

The Phenomena appears to be based on two prose works—Phenomena and Enoptron (Ἔνοπτρον, “Mirror”, presumably a descriptive image of the heavens)—by Eudoxus of Cnidus, written about a century earlier. We are told by the biographers of Aratus that it was the desire of Antigonus to have them turned into verse, which gave rise to the Phenomena of Aratus; and it appears from the fragments of them preserved by Hipparchus, that Aratus has in fact versified, or closely imitated parts of them both, but especially of the first.

The purpose of the Phenomena is to give an introduction to the constellations, with the rules for their risings and settings; and of the circles of the sphere, amongst which the Milky Way is reckoned. The positions of the constellations, north of the ecliptic, are described by reference to the principal groups surrounding the north pole (Ursa MajorUrsa MinorDraco, and Cepheus), whilst Orion serves as a point of departure for those to the south. The immobility of the Earth, and the revolution of the sky about a fixed axis are maintained; the path of the Sun in the zodiac is described; but the planets are introduced merely as bodies having a motion of their own, without any attempt to define their periods; nor is anything said about the Moon’s orbit. The opening of the poem asserts the dependence of all things upon Zeus. From the lack of precision in the descriptions, it would seem that Aratus was neither a mathematician nor observer[4] or, at any rate, that in this work he did not aim at scientific accuracy. He not only represents the configurations of particular groups incorrectly, but describes some phenomena which are inconsistent with any one supposed latitude of the spectator, and others which could not coexist at any one epoch. These errors are partly to be attributed to Eudoxus himself, and partly to the way in which Aratus has used the materials supplied by him. Hipparchus (about a century later), who was a scientific astronomer and observer, has left a commentary upon the Phenomenas of Eudoxus and Aratus, accompanied by the discrepancies which he had noticed between his own observations and their descriptions.

Diosemeia

The Diosemeia consists of forecasts of the weather from astronomical phenomena, with an account of its effects upon animals. It appears to be an imitation of Hesiod, and to have been imitated by Virgil in some parts of the Georgics.[2] The materials are said to be taken almost wholly from Aristotle‘s Meteorologica, from the work of TheophrastusOn Weather Signs, and from Hesiod. Nothing is said in either poem about Hellenistic astrology.

The crater Aratus on the Moon and the minor planet 12152 Aratus are named in his honour.

ONE OF THE BEST EVER Aristarchus of Samos

In the period between Euclid and Archimedes comes Aristarchus of Samos (about 310-230 b. c.), famous for having anticipated Copernicus. Accepting Heraclides’s view that the earth rotates about its own axis, Aristarchus went further and put forward the hypothesis that the sun itself is at rest, and that the earth, as well as Mercury, Venus, and the other planets, revolve in circles about the sun. We have this on the unquestionable authority of Archimedes, who was only some twenty-five years later, and who must have seen the book containing the hypothesis in question. We are told too that Cleanthes the Stoic thought that Aristarchus ought to be indicted on the charge of impiety for setting the Hearth of the Universe in motion.

One work of Aristarchus, On the sizes and distances of the Sun and Moon, which is extant in Greek, is highly interesting in itself, though it contains no word of the heliocentric hypothesis. Thoroughly classical in form and style, it lays down certain hypotheses and then deduces therefrom, by rigorous geometry, the sizes and distances of the sun and [122]moon. If the hypotheses had been exact, the results would have been correct too; but Aristarchus in fact assumed a certain angle to be 87° which is really 89° 50′, and the angle subtended at the centre of the earth by the diameter of either the sun or the moon to be 2°, whereas we know from Archimedes that Aristarchus himself discovered that the latter angle is only ½°. The effect of Aristarchus’s geometry is to find arithmetical limits to the values of what are really trigonometrical ratios of certain small angles, namely

1/18 > sin 3° > 1/20, 1/45 > sin 1° > 1/60, 1 > cos 1° > 89/90.

The main results obtained are (1) that the diameter of the sun is between 18 and 20 times the diameter of the moon, (2) that the diameter of the moon is between 2/45ths and 1/30th of the distance of the centre of the moon from our eye, and (3) that the diameter of the sun is between 19/3rds and 43/6ths of the diameter of the earth. The book contains a good deal of arithmetical calculation.

Aristyllus (Greek: Ἀρίστυλλος; fl. c. 261 BC) was a Greek astronomer, presumably of the school of Timocharis (c. 300 BC). He was among the earliest meridian-astronomy observers. Six of his stellar declinations are preserved at Almajest 7.3. All are exactly correct within his over-cautious rounding to 1/4 degree. See discussion (and lessons) at DIO 7.1 ‡1 p. 13 (2007).

Aristyllus was long mis-dated to c. 300 BC (which made his data look among the poorest of the ancients); but when his correct date was found by least-squares (Isis 73:259-265 [1982] p. 263), it was realized that his star declinations’ accuracy was unexcelled in antiquity. His data suggest that he worked in Alexandria: see DIO 4.1 ‡3 Table 3 p. 45 (2004).

lunar craterAristillus, aptly near the Moon’s meridian and at a lunar latitude roughly equal to the terrestrial latitude of Alexandria, is named after him.Sources

“Aristyllus was an early astronomer in the school of Alexandria. Little is known about him. He made astronomical observations during the first half of the third century BCE, and was probably a pupil of Timocharis.”

“Aristyllus and Timocharis are usually considered to have compiled the first true catalog of the fixed stars, in which stars are identified by numerical measurements of their positions.”

“Aristyllus, a Greek astronomer, who appears to have lived about B.C. 233. He wrote a work on the fixed stars (τηρήσις ἀπλανῶν), which was used by Hipparchus and Ptolemy, and he is undoubtedly one of the two persons of this name who wrote commentaries on Aratus.”References

  1. “Aristyllus – Springer”. springerreference.com. Retrieved 2014-12-10.
  2. Hockey, T.; Bracher, K.; Bolt, M.; Trimble, V.; Palmeri, J.A.; Jarrell, R.; Marché, J.D.; Ragep, F.J. (2007). Biographical Encyclopedia of Astronomers. Springer. p. 62. ISBN 9780387304007. Retrieved 2014-12-10.
  3. “A Dictionary of Greek and Roman biography and mythology, Abaeus, Ari’stophon, Aristyllus”. perseus.tufts.edu. Retrieved 2014-12-10.

External links

Aristillus is a prominent lunarimpact crater that lies in the eastern Mare Imbrium. It was named after Greek astronomer Aristyllus.[1] Directly to the south is the smaller crater Autolycus, while to the southwest is the large Archimedes. To the northeast are the craters Theaetetus and Cassini.

The rim of Aristillus has a wide, irregular outer rampart of ejecta that is relatively easy to discern against the smooth surface of the surrounding mare. The crater impact created a ray system that extends for a distance of over 600 kilometers. Due to its rays, Aristillus is mapped as part of the Copernican System.[2] The rim is generally circular in form, but possesses a slight hexagonal shape. The inner walls of the rim have a terraced surface, and descend to a relatively rough interior that has not been flooded with lava. In the middle of the crater is a set of three clustered peaks, which rise to a height of about 0.9 km.

In the northern outer ramparts of Aristillus is a ghost crater remnant. This is the protruding rim of an old crater that has been almost completely submerged by the lava flows of the surrounding Mare Imbrium. The southern end of the rim has been covered by the ejecta from Aristillus. Along the eastern inner wall and rim is an unusual narrow ribbon of dark material.Detail map of Mare Imbrium’s features. Aristillus is the feature marked “E”.

English progressive rock band Camelnamed the first song on their Moonmadness album after the crater. Science fiction author Travis J I Corcoran set much of his first novel, The Powers of the Earth, on and under Aristillus.Satellite craters

By convention these features are identified on lunar maps by placing the letter on the side of the crater midpoint that is closest to Aristillus.

SOURCES https://www.revolvy.com ,www.mlahanas.de ,WIKI

(TO BE CONTINUED)

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About sooteris kyritsis

Job title: (f)PHELLOW OF SOPHIA Profession: RESEARCHER Company: ANTHROOPISMOS Favorite quote: "ITS TIME FOR KOSMOPOLITANS(=HELLINES) TO FLY IN SPACE." Interested in: Activity Partners, Friends Fashion: Classic Humor: Friendly Places lived: EN THE HIGHLANDS OF KOSMOS THROUGH THE DARKNESS OF AMENTHE
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