3. (Science: astronomy) The apparent surface of the heavens, which is assumed to be spherical and everywhere equally distant, in which the heavenly bodies appear to have their places, and on which the various astronomical circles, as of right ascension and declination, the equator, ecliptic, etc, are conceived to be drawn; an ideal geometrical sphere, with the astronomical and geographical circles in their proper positions on it. In ancient astronomy, one of the concentric and eccentric revolving spherical transparent shells in which the stars, sun, planets, and moon were supposed to be set, and by which they were carried, in such a manner as to produce their apparent motions.
5. Circuit or range of action, knowledge, or influence; compass; province; employment; place of existence. To be called into a huge sphere, and not to be seen to move in 't. (Shak) Taking her out of the ordinary relations with humanity, and inclosing her in a sphere by herself. (Hawthorne) Each in his hidden sphere of joy or woe Our hermit spirits dwell. (Keble)
7. An orbit, as of a star; a socket. Armillary sphere, crystalline sphere, oblique sphere,. See Armillary, crystalline,. Doctrine of the sphere, applications of the principles of spherical trigonometry to the properties and relations of the circles of the sphere, and the problems connected with them, in astronomy and geography, as to the latitudes and longitudes, distance and bearing, of places on the earth, and the right ascension and declination, altitude and azimuth, rising and setting, etc, of the heavenly bodies; spherical geometry. Music of the spheres. See music.