ABERRATION OF THE PLANETS, is equal to their geocentric motion, or, in other words, to the space which each appears to move as seen from the earth, during the time that light employs in passing from the planet to the eye of the observer. Thus the sun's aberration in longitude is constantly 20', that being the space actually moved by the earth; but apparently by the sun in 8 minutes and 7 seconds, the time in which light passes from the sun to the earth. If then the distance of any planet from the earth be known, the time which light employs in passing from the planet to the earth must likewise be known; for as the distance of the sun is to the distance of the planet, so is 8 minutes and 7 seconds to that time; and the planet's geocentric motion in that time is its aberration, whether it be in longitude, latitude, right ascension, or declination. See ASTRONOMY in this Supplement.