HEAVEN, among astronomers, called also the ethereal and starry heaven, is that immense region wherein the stars, planets, and comets, are disposed. See ASTRONOMY Index.
This is what Moses calls the firmament, speaking of it as the work of the second day's creation; at least it is thus the word רָמָה is usually rendered by his interpreters; though somewhat abusively, to countenance their own notion of the heavens being firm or solid. The word, it is certain, properly signifies no more than expanse or extension; a term very well adapted by the prophet to the impression which the heavens make on our senses; whence, in other parts of scripture, the heaven is compared to a curtain, or a tent stretched out to dwell in. The LXX first added to this idea of expansion that of firm or solid; rendering it by σπίμα, according to the philosophy of those times; in which they have been followed by the modern translators.
The latter philosophers, as Des Cartes, Kircher, &c. have easily demonstrated this heaven not to be solid, but fluid; but they still suppose it full, or perfectly dense, without any vacuity, and cantoned out into many vortices. But others have overturned not only the solidity, but the supposed plenitude, of the heavens. Sir Isaac Newton has abundantly shown the heavens void of almost all resistance, and, consequently, of almost all matter: this he proves from the phenomena of the celestial bodies; from the planets persisting in their motions without any sensible diminution of their velocity; and the comets freely passing in all directions towards all parts of the heavens.
Heaven, taken in a general sense, for the whole expanse between our earth and the remotest regions of the fixed stars, may be divided into two very unequal parts, according to the matter found therein; viz. the atmosphere, or aerial heaven, possessed by air; and the ethereal heaven, possessed by a thin, unrefining medium, called ether.
HEAVEN is more particularly used, in Astronomy, for an orb, or circular region, of the ethereal heaven.
The ancient astronomers assumed as many different heavens as they observed different motions therein. These they supposed all to be solid, as thinking they could not otherwise sustain the bodies fixed in them: and spherical, that being the most proper form for motion. Thus we had seven heavens for the seven planets, viz. the heavens of the Moon, Mercury, Venus, the Sun,
Mars, Jupiter, and Saturn. The eighth was for the fixed stars, which they particularly called the firmentum. Ptolemy adds a ninth heaven, which he called the primum mobile. After him two crystalline heavens were added by King Alphonseus, &c. to account for some irregularities in the motions of the other heavens: and lastly, an empyrean heaven was drawn over the whole, for the residence of the Deity; which made the number twelve. But others admitted many more heavens, according as their different views and hypotheses required. Eudoxus supposed 23, Calippus 30, Regiomontanus 33, Aristotle 47, and Fracastor no less than 70. It must be added, however, that the astronomers did not much concern themselves whether the heavens they thus allow of were real or not; provided they served a purpose in accounting for any of the celestial motions, and agreed with the phenomena.