SYSTEM
, in a general Sense, denotes an assemblage or chain of principles and conclusions: or the whole of any doctrine, the several parts of which are bound together, and follow or depend on each other. As a System of astronomy, a System of planets, a System of philosophy, a System of motion, &c.
System, in Astronomy, denotes an hypothesis or a supposition of a certain order and arrangement of the several parts of the universe; by which astronomers explain all the phenomena or appearances of the heavenly bodies, their motions, changes, &c.
This is more peculiarly called the System of the world, and sometimes the Solar System.
System and hypothesis have much the same signification; unless perhaps hypothesis be a more particular System, and System a more general hypothesis.
Some late authors indeed make another distinction: an hypothesis, say they, is a mere supposition or fiction, founded rather on imagination than reason; while a System is built on the firmest ground, and raised by the severest rules; it is founded on astronomical observations, and physical causes, and confirmed by geometrical demonstrations.
The most celebrated Systems of the world, are the Ptolomaic, the Copernican or Pythagorean, and the Tychonic: the economy of each of which is as follows.
Ptolomaic System is so called from the celebrated astronomer Ptolomy. In this System, the earth is placed at rest, in the centre of the universe, while the heavens are considered as revolving about it, from east to west, and carrying along with them all the heavenly bodies, the stars and planets, in the space of 24 hours.
The principal assertors of this System, are Aristotle, Hipparchus, Ptolomy, and many of the old philosophers, followed by the whole world, for a great number of ages, and long adhered to in many universities, and other places. But the late improvements in philosophy and reasoning, have utterly exploded this erroneous System from the place it so long held in the minds of men.
Copernican System, is that System of the world | which places the Sun at rest, in the centre of the world, and the earth and planets all revolving round him, in their several orbits. See this more particularly explained under the article Copernican System.
Solar or Planetary System, is usually confined to narrower bounds; the stars, by their immense distance, and the little relation they seem to bear to us, being accounted no part of it. It is highly probable that each fixed star is itself a Sun, and the centre of a particular System, surrounded with a company of planets &c, which, in different periods, and at different distances, perform their courses round their respective sun, which enlightens, warms, and cherishes them. Hence we have a very magnificent idea of the world, and the immensity of it. Hence also arises a kind of System of Systems.
The Planetary System, described under the article Copernican, is the most ancient in the world. It was first of all, as far as we know, introduced into Greece and Italy by Pythagoras; from whom it was called the Pythagorean System. It was followed by Philolaus, Plato, Archimedes, &c: but it was lost under the reign of the Peripatetic philosophy; till happily retrieved about the year 1500 by Nic. Copernicus.
Tychonic System, was taught by Tycho, a Dane; who was born An. Dom. 1546. It supposes that the earth is fixed in the centre of the universe or firmament of stars, and that all the stars and planets revolve round the earth in 24 hours; but it differs from the Ptolomaic System, as it not only allows a menstrual motion to the moon round the earth, and that of the satellites about Jupiter and Saturn, in their proper periods, but it makes the sun to be the centre of the orbits of the primary planets Mercury. Venus, Mars, Jupiter, &c, in which they are carried round the sun in their respective years, as the sun revolves round the earth in a solar year; and all these planets, together with the sun, are supposed to revolve round the earth in 24 hours. This hypothesis was so embarrassed and perplexed, that very few persons embraced it. It was afterwards altered by Longomontanus and others, who allowed the diurnal motion of the earth on its own axis, but denied its annual motion round the sun. This hypothesis, partly true and partly false, is called the Semi-Tychonic System. See the figure and economy of these Systems, in plates 30, 31, 32, 33.
System, in Music, denotes a compound interval; or an interval composed, or conceived to be composed of several less intervals. Such is the octave, &c.
