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ASTRONOMY, Astronomia, the Doctrine of the Hea- vens, and the Phenomena thereof. See Heaven.
Aftro?tomy is properly a mix'd mathematical Science, whereby we become acquainted with the Cadeftial Bodies, their Magni- tudes, Motions, Diftances, Periods, Eclipfes, &<■ SeeMATHE-
MATICKS.
Some underftand the Word Aftronomy in a more exteniive Senfe; including under it the Theory of the Univerfe, and the primary Laws of Nature ■ In which Senfe it rather feems a Branch of Phyftcks than of Mathematicks. See Physicks, System, Na- ture, &c.
The Word is compounded of the Greek "s-»{, Star ; and «»^s, Law, Rule.— Care muft be taken to diftinguilh Agronomy from Aftrology. See Astrology.
The Heavens may be confider'd two Ways; either as they ap- pear to the naked Senfe, or as they are difcovered by rhe Un- derftanding : And hence Aftronomy is divided into two Branches, Spherical and Theorical.
Spherical Astronomy, f „ 5 Spherical Aftronomy. Theorkal Astronomy, $ £ Theorical Aftronomy.
The Invention of Aftronomy has been varioufly affigncd ; and feveral Peilbns, feveral Nations, and feveral Ages have laid claim to it,— From the Accounts given us by the antient Hiftorians, it appears that Kings were the firft Inventors and Cultivators of it : Thus, Belus, King of Ajjyria, Atlas, King of Mauritania, and Uranus, King of the Country iicuate on the Shore of the Atlantic!: Ocean, are feverally recorded, as the Perfons to whom the World owes this noble Science.
This, at leaft, is pretty evident, that it was known to thofe Nations long before it came into Greece : Agreeably to which, Plato tells us, it was a Barbarian who firft oblerved the heavenly Morions; to which he was led by the clearnefs of the Weather in the Summer Seafon, as in Egypt and Syria, where the Stars arc conftantlv feen, there being no Rain or Clouds to interrupt the Prolped.' And the want of this clearnefs of Atmofphere the fame Author lays down as the Reafon why the Greeks came fo late to the Knowledge of Afronomy.
The generality of Writers fix rhe Origin of Aftronomy and Aftrology in Chahtea ; and accordingly among the Antients we find the Word Chaldean frequently ufed for Aftronomcr.— Some chute to attribute the Invention to the antient Hskewi ; and fome, e- ven, to the firft Men; building on the Authority of Jofephtis, and of what he mentions about Seth's Pillars.— The Muftubuans afcribe it to Enoch, and other Orientals to Cain— Bat thefe Opi- nions appear fcarcely probable to others, in regard they find no Terms of Aftronomy in the Language of thofe firft People, that is, in the Hebrew Language; which, on the contrary, are very frequent in the ChaUee : Though it muft be own'd we have fomcihing ot this kind in Job, and the Books of Solomon
We don't know whether it is worth noting, that RuJbeck, in his Atlantis, maintains Aftronomy to have been invented by the Swedes : His Reafons are, the gteat Diverfity in the length of the Days in that Country, which muft naturally lead the People to conclude the Earth round, and that they lived neat one of us Extremes : A Conclulion which the Chaldeans, and other Inhabi- tants of the middle Parts of the Globe, had no eafy Way of coming at. The Swedes, adds our Author, prompted hereby to enquire further into the great Oppolition of Seafons, foon difco- ver'd that the Sun bounds his Progrefs by a cerrain Space in the Heavens, &c— But we have no Hiftorical Fads to fupport this reafoning, which at beft only proves that the thing might be fo.
By Porphyry's Account, Aftronomy muft have been of a very antient Banding in the Eaft ; for he tells us, that when Baby/on was taken by Alexander, there were brought thence cseleftial Obfervations, for the Space of 1903 Years, which therefore muft have commenced within 1 15 Years of the Flood, or fifteen Years of the building o{Babel:—Epigenes,accordmgmPlixy,a3irm- ed that the Babylonians had Obfervations of 720 Years, engra- ven on Bricks.— Achilles Tatius afcribes the Invention of Aftro- nomy to the Egyptians; and adds, that their Knowledge therein was engraven on Columns, and by that means tranfmitted to Po- fterity.
From the Egyptians, Aftronomy is commonly fuppofed to have pafs'd to the Greeks: Laertius tells us, that Thales, firft, about the 90th Olympiad, and after him Ettdoxus and Pythagoras, tra- veli'd into Egypt, to be inftru&ed herein ; and that this laft, in patticular, living in a clofe Community with the Egyptian Priefts for feven Years, and being initiated into their Religion, was here let into the true Syftem of the Univerfe; which he afterwatds taught in Greece and Italy. — He was the firft, among the Euro- peans, who taught that the Earth and Planers turn round the Sun, which ftands immoveable in the Center ; that the diurnal Moti- on of the Sun and fix'd Stars, was not real but apparent, anfing from the Earth's Motion round its own Axis, & c. See Pytha- gorean.
Yet Fllrmiiai reprefents the Introduction of Aftronomy into 'Cfrmt, fomewhat differently; maintaining, thj. Berofis, a Baby-
lonian, brought it thither immediately from Babylon itfelf ; anal open'd an Aftronomical School in the Ifland of Cos. Pliny, Lib. VII. c. 37. adds, that in confideration of his wonderful Predicti- ons, the Athenians erected him a Statue in the Gymnaftum, with a gilded Tongue. — If this Berojits be the fame with the Author of the ChaUee Hillories, he muft have been before Alexander.
After Pythagoras, Aftronomy funk into neglect ; moft of the OEleftial Obfetvations brought from Babylon, were loft, and 'twas but a very fmall Number that Ptolomy, in his Time, was able to retrieve. — However, fome few of his Followers continued to cul- tivate Aftronomy ; among whom were Philolaus and Ariftarchus Samius.
At length, thofe Patrons of Learning, the Ptolomys, Kings of Egypt, founding an Academy for Aftro-aomy, at Alexandria, there arole feveral eminent Aftronomers from the fame; particularly Hipparchus, who, according to Pliny, undertook what wou d have been a great Work even for a God Co atchieve, vise, to number the Stars, and leave tire Heavens as an Inheritance to Polterity .- He foretold the Eclipfes both of the Sun and Moon tor 600 Years, and on his Obfervations is founded that noble Work ot Ptolomy, intitled pr/aM trvsri^tf. See CataloGUT, &c.
The Sarazens, on their Conqu'eft of Egypt, got a Tincture of Aftronomy, which they carried with them out of Africa into Spain ; and by this means Aftronomy, after a long Exile, was at length introduced afrefh into Europe.
From this Time, Aftronomy began to improve very confidera- bly ; being cultivated by the grcatcft Genius's, and patronized by the grcatcit Pi'mces.—Alpbonjiis, King of Caftile, emich'dic with thofe Tables which (till bear his Name. SeeTAflLE.
Copernicus re-elhl hlh'd the antient Pythagorean Syftem ; And Tycho brake publilh'd a Catalogue of 770 fixed Stars, trom Iris own Observations. See Copernican, Star. &c.
Kepler, from Tycho's Labours, foon after diicovered the true Theory of the World ; and the phyfica) Laws by which the hea- venly Bodies move. See Planet, Period, Gravitation, dc.
Galileo firft introduced Telefcopes into Aftronomy, and by their means discovered the Satellites of Jupiter; the various Phales of Saturn, the Mountains ot the Moon, the Spots in the Sun, and its Revolution about its Axis. See Tellescope, Satellite, Moon, Macule, &c.
Add, that Hevelius, from his own curious Obfervations, fur- nifhed a Catalogue of the fix'd Stars, much more complece than Tycho's. — Huygens and Caftini difcovered the Satellites of Saturn,
and his Ring And Gaftendas, Horrox, Bullialdus, Ward, Rtccio-
lus, Gafcoign, &c. each contributed very confiderably to the Im- provement of Aftronomy. See Saturn, Ring, Elliptic, Mi- crometer, &c.
The immortal Newton firft demenftrared from phyfical Con T fiderations, the great Law that regulates all the heavenly Moti- ons, lets bounds to the Planets Orbs, and determines their grcatcft Excuriions trom the Sun, and their neareft approaches to it. — 'Twas he firft taught the Worid whence arole that conftanc and regular Proportion obferveu by both primary and ieconeary Pla- nets, in their Circulation round their central Bodies ; and their Diftances compared with their Periods. — He has given us a new Theory of the Moon, which accurately aniwers ail her Inequa- lities, and accounts for 'em from sric Laws of Gravity and Me- chaniitn. See Newtonian. Sec alio Attraction, Moon, Tide, &c.
Dr. Bailey obliged the Wotld with [he Aftronomy of Comets, and with a Catalogue of the Stars in the foudiern Hemiiphere; and continues ftill a Benefactor to Aftronomy, by his Obfervati- ons : To which it may be added, that he has m the Prefs, a new fet of aftronomical Tables ; preferable by many Degrees to any yet pubhfhed. See Comet, Taele, <&c
Mr. Flamftead upwards of forty Years watch'd the Motions of the Scars, and has given us a great number of curious Obier- vacions of [he Sun, Moon, an.i Planets ; belides a noble Catalogue of 3000 fix'd Scacs; which is more than double the Number in that of Hevelius. — Nothing now feem'd wanting to Aftronomy, but an univcrfal and compleac Theory of the cseleftial Phenome- na, explained according to their true Motions and phyfical Caufes, which has been performed by Dr. Gregory. SccCentripetal, Centrifugal, etc.
Astronomy is fomecimes divided, with refpecl to its different Scaces, into New and Old.— The antient Aftronomy is fuch as rhe Arc flood under Ptolomy, and his Followers; with all theApparalusof folid Orbs, Epicycles, Excenrricks, Deferents, Trepidations, (ire. See Ptolomaic. See alfo Heaven, Epicycle, eJ-r.
The antient Aftronomy is delivet'd by Claud. Ptolomy, who died A. D. 147; in his p>iy*?m Swerogis; tranllated in 827, into Ara- hick; and thence, in 1528, mo Latin. An Epitome of it, for the ufc of Learners, was made by Purbachius and his Scholar Re- giomontanus, in 1550; containing [he whole Doctrine of the hea- venly Motions, their Magnitudes, Eclipfes, cj-c— On che Model hereof, Albategeimis che Arab, compiled another Work, on the Knowledge of the Stars, publiihed in Latin 1537.
The New Aftronomy is fuch as the Art lias been fince Copernicus ; y by whom thoie fictitious Machines were thrown out; and the Con- flitution of the Heavens reduced to more limple, natural, and certain Principles. See Copernican. See alfo System, Sun.
Earth,
