ASTRONOMY, Astronomia, the Doctrine of the Heavens, and the Phenomena thereof. See HEAVEN.

Astronomy is properly a mix'd mathematical Science, whereby we become acquainted with the Cadestial Bodies, their Magnitudes, Motions, Distances, Periods, Eclipses, &c. See MATHEMATICKS.

Some understand the Word Astronomy in a more extensive Sense; including under it the Theory of the Universe, and the primary Laws of Nature &c. In which Sense it rather seems a Branch of Phystcks than of Mathematicks. See PHYSICKS, SYSTEM, NATURE, &c.

The Word is compounded of the Greek ἀστὴρ, Star ; and νόμος, Law, Rule.—--- Care must be taken to distinguish Astronomy from Astrology. See ASTROLOGY.

The Heavens may be consider'd two Ways; either as they appear to the naked Sense, or as they are discovered by the Understanding : And hence Astronomy is divided into two Branches, Spherical and Theorical.


The Invention of Astronomy has been variously assigned ; and several Persons, several Nations, and several Ages have laid claim to it.---— From the Accounts given us by the antient Historians, it appears that Kings were the first Inventors and Cultivators of it : Thus, Belus, King of Assyria, Atlas, King of Mauritania, and Uranus, King of the Country situate on the Shore of the Atlantick Ocean, are severally recorded, as the Persons to whom the World owes this noble Science.

This, at least, is pretty evident, that it was known to those Nations long before it came into Greece : Agreeably to which, Plato tells us, it was a Barbarian who first observed the heavenly Motions; to which he was led by the clearness of the Weather in the Summer Season, as in Egypt and Syria, where the Stars are constantlv seen, there being no Rain or Clouds to interrupt the Prospect. And the want of this clearness of Atmosphere the same Author lays down as the Reason why the Greeks came so late to the Knowledge of Asronomy.

The generality of Writers fix the Origin of Astronomy and Astrology in Chaldea ; and accordingly among the Antients we find the Word Chaldean frequently used for Astronomer.—--- Some chuse to attribute the Invention to the antient Hebrews ; and some, even, to the first Men; building on the Authority of Josephus, and of what he mentions about Seth's Pillars.—--- The Mussulmans ascribe it to Enoch, and other Orientals to Cain.---— But these Opinions appear scarcely probable to others, in regard they find no Terms of Astronomy in the Language of those first People, that is, in the Hebrew Language; which, on the contrary, are very frequent in the Chaldee : Though it must be own'd we have something of this kind in Job, and the Books of Solomon.

We don't know whether it is worth noting, that Rudbeck, in his Atlantis, maintains Astronomy to have been invented by the Swedes : His Reasons are, the great Diversity in the length of the Days in that Country, which must naturally lead the People to conclude the Earth round, and that they lived near one of its Extremes : A Conclusion which the Chaldeans, and other Inhabitants of the middle Parts of the Globe, had no easy Way of coming at. The Swedes, adds our Author, prompted hereby to enquire further into the great Opposition of Seasons, soon discover'd that the Sun bounds his Progress by a certain Space in the Heavens, &c.---— But we have no Historical Facts to support this reasoning, which at best only proves that the thing might be so.

By Porphyry's Account, Astronomy must have been of a very antient standing in the East ; for he tells us, that when Babylon was taken by Alexander, there were brought thence cælestial Observations, for the Space of 1903 Years, which therefore must have commenced within 115 Years of the Flood, or fifteen Years of the building of Babel: ---— Epigenes,according to Pliny, affirmed that the Babylonians had Observations of 720 Years, engraven on Bricks.—--- Achilles Tatius ascribes the Invention of Astronomy to the Egyptians; and adds, that their Knowledge therein was engraven on Columns, and by that means transmitted to Posterity.

From the Egyptians, Astronomy is commonly supposed to have pass'd to the Greeks: Laertius tells us, that Thales, first, about the 90th Olympiad, and after him Eudoxus and Pythagoras, travell'd into Egypt, to be instructed herein ; and that this last, in patticular, living in a close Community with the Egyptian Priests for seven Years, and being initiated into their Religion, was here let into the true System of the Universe; which he afterwards taught in Greece and Italy.—--- He was the first, among the Europeans, who taught that the Earth and Planers turn round the Sun, which stands immoveable in the Center ; that the diurnal Motion of the Sun and six'd Stars, was not real but apparent, arising from the Earth's Motion round its own Axis, & c. See PYTHAGOREAN.

Yet Vitruvius represents the Introduction of Astronomy into Greece , somewhat differently; maintaining, that Berosus, a Babylonian, brought it thither immediately from Babylon itself ; and open'd an Astronomical School in the Island of Cos. Pliny, Lib. VII. c. 37. adds, that in consideration of his wonderful Predictions, the Athenians erected him a Statue in the Gymnastum, with a gilded Tongue.—--- If this Berosus be the same with the Author of the Chaldee Histories, he must have been before Alexander.

After Pythagoras, Astronomy sunk into neglect ; most of the cælestial Obsetvations brought from Babylon, were lost, and 'twas but a very small Number that Ptolomy, in his Time, was able to retrieve.---— However, some few of his Followers continued to cultivate Astronomy ; among whom were Philolaus and Aristarchus Samius.

At length, those Patrons of Learning, the Ptolomys, Kings of Egypt, founding an Academy for Astronomy, at Alexandria, there arose several eminent Astronomers from the same; particularly Hipparchus, who, according to Pliny, undertook what wou'd have been a great Work even for a God to atchieve, viz. to number the Stars, and leave tire Heavens as an Inheritance to Posterity. He foretold the Eclipses both of the Sun and Moon tor 600 Years, and on his Observations is sounded that noble Work of Ptolomy, intitled μεγάλη συντάξις. See CATALOGUE, &c.

The Sarazens, on their Conquest of Egypt, got a Tincture of Astronomy, which they carried with them out of Africa into Spain ; and by this means Astronomy, after a long Exile, was at length introduced afresh into Europe.

From this Time, Astronomy began to improve very considerably ; being cultivated by the greatest Genius's, and patronized by the greatest Princes.—--- Alpbonsus, King of Castile, enrich'd it with those Tables which still bear his Name. See TABLE.

Copernicus re-establish'd the antient Pythagorean System ; And Tycho Brahe publish'd a Catalogue of 770 fixed Stars, from his own Observations. See COPERNICAN, STAR. &c.

Kepler, from Tycho's Labours, soon after discovered the true Theory of the World ; and the physical Laws by which the heavenly Bodies move. See PLANET, PERIOD, GRAVITATION, &c. Galileo first introduced Telescopes into Astronomy, and by their means discovered the Satellites of Jupiter; the various Phases of Saturn, the Mountains of the Moon, the Spots in the Sun, and its Revolution about its Axis. See TELLESCOPE, SATELLITE, MOON, MACULÆ, &c.

Add, that Hevelius, from his own curious Observations, furnished a Catalogue of the fix'd Stars, much more complete than Tycho's.---— Huygens and Cassini discovered the Satellites of Saturn, and his Ring And Gassendas, Horrox, Bullialdus, Ward, Ricciolus, Gascoign, &c. each contributed very considerably to the Improvement of Astronomy. See SATURN, RING, ELLIPTIC, MICROMETER, &c.

The immortal Newton first demonstrated from physical Considerations, the great Law that regulates all the heavenly Motions, lets bounds to the Planets Orbs, and determines their greatest Excursions trom the Sun, and their nearest approaches to it.—--'Twas he first taught the World whence arose that constant and regular Proportion observed by both primary and secondary Planets, in their Circulation round their central Bodies ; and their Distances compared with their Periods.---— He has given us a new Theory of the Moon, which accurately answers all her Inequalities, and accounts for 'em from stric Laws of Gravity and Mechanism. See NEWTONIAN. See also ATTRACTION, MOON, TIDE, &c.

Dr. Halley obliged the World with the Actronomy of Comets, and with a Catalogue of the Stars in the southern Hemisphere; and continues still a Benefactor to Astronomy, by his Observations : To which it may be added, that he has m the Press, a new set of astronomical Tables ; preferable by many Degrees to any yet published. See COMET, TABLE, &c.

Mr. Flamstead upwards of forty Years watch'd the Motions of the Stars, and has given us a great number of curious Observations of the Sun, Moon, and Planets ; besides a noble Catalogue of 3000 fix'd Stars; which is more than double the Number in that of Hevelius.---— Nothing now seem'd wanting to Astronomy, but an universal and compleat Theory of the cælestial Phænomena, explained according to their true Motions and physical Causes, which has been performed by Dr. Gregory. See CENTRIPETAL, CENTRIFUGAL, etc.

Astronomy is somecimes divided, with respect to its different States, into New and Old.—--- The antient Astronomy is such as the Art stood under Ptolomy, and his Followers; with all the Apparatus of solid Orbs, Epicycles, Excentricks, Deterents, Trepidations, &c. See PTOLOMAIC. See also HEAVEN, EPICYCLE, &c.

The antient Astronomy is deliver'd by Claud. Ptolomy, who died A. D. 147; in his p>iy*?m Swerogis; tranlated in 827, into Arabick; and thence, in 1528, into Latin. An Epitome of it, for the use of Learners, was made by Purbachius and his Scholar Regiomontanus, in 1550; containing the whole Doctrine of the heavenly Motions, their Magnitudes, Eclipses, &c.---— On the Model hereof, Albategennis the Arab, compiled another Work, on the Knowledge of the Stars, published in Latin 1537.

The New Astronomy is such as the Art has been since Copernicus ; by whom those fictitious Machines were thrown out; and the Constitution of the Heavens reduced to more simple, natural, and certain Principles. See COPERNICAN. See also SYSTEM, SUN, EARTH, PLANET, ORBIT, &c. See also SPHERE, GLOBE, &c.

The modern Astronomy is delivered in Copernkus's six Books of Cælestial Revolutions, published about the Year 1566 ; wherein, by retrieving Pythagoras's and Philolaus's Dogma of the Motion of the Earth, he laid the Foundation of a juster System.—--Kepler's Commentaries of the Motions of Mars, published in 1609; wherein, in lieu of the circular Orbits admitted by all former Astronomers, he proposed the elliptic Theory ; which, in his Epitome of the Copernican Astronomy, published in 1635 he applied to all the Planets.—--- Ish. Bullialdus's Astronomia Philolaica, published in 1645, wherein he endeavoured to amend Kepler's Theory, and render the Calculus more Exact and Geometrical : Some Errors committed by Bullialdus were pointed out by Dr. Seth. Ward, in his Inquiry into the Phihlak Astronomy, published in 1653 ; and corrected by himself in his Foundations of the Philoaic Astronomy more clearly explain'd, in 1657.---— Ward's Astronomia Geometrica, published in 1656; wherein a Geometrical Method is proposed of computing the Planets Motions ; though not consistent with the true Laws of their Motions established by Kepler. The same was proposed the Year following by the Count de Pagan. The Truth is, Kepler himself does not seem to have been ignorant thereof ; but rather chose to set it aside, as finding it contrary to Nature. — Vin. Wing's Astronomia Britannica, publish'd in 1669; wherein, going on Bullialdus's Principles, he gives juii Examples of all the Precepts in practical Astronomy, well accommodated to the Capacity of Learners — Newton's Astronomia Britannica, published in 1657; and Street's Astronomia Carolina, in 1661 ; both upon Ward's Hypothesis.

In Ricctoius's Almagesium Magnum, published in 1651, we have the several Hypotheses of ail the Actronomers, antient as well as modern.---— And in Dr. Gregory's Elementa Astronomiæ Physicæ & Geometricæ, in 1702, the whole modern Astronomy, as founded on the Discoveries of Copernicus, Kepler, and Sir Isaac Newton.---— The Marrow of the new Astronomy is also laid down by Whiston, in his Præletion Astronomicæ, in 1707.---— For Novices in the Art, Mercators Institutiones Astronomicæ, published in 1676 ; which contains the whole Doctrine, both according to the Antients and Moderns ; and Dr. Keill's Introductio ad Veram Astronomiam, in 1718, which only takes in the Modern, are the best calculated.