Venus (Astronomy the second)

Collier's New Encyclopedia (1921)

in astronomy, the second of the known inferior planets, if the arrangement be made according to their relative distances from the sun. With the exception of the moon Venus is nearest of all the heavenly bodies to the earth, and, when near its extreme E. or W. elongation, is much brighter than even the largest of the fixed stars. It stands first in this respect also of all the planets, the nearest approach to it being that made at certain times by Jupiter. When Venus is at its maximum of brightness, it can sometimes be seen by the naked eye in sunlight within an hour of noon. Its comparative nearness to the sun causes it to be for six months a morning and for the other six months an evening star. In the first state, it is the Lucifer of the Latins and the Phosphor of the Greeks; in the latter, it is the Hesperus of classical antiquity and of modern poetry. It undergoes phases like the moon. Father Castelli, Castelli, a famous Florentine philosopher, reasoned this out, and, questioning Galileo on the subject, induced him to look with his telescope and see. On Dec. 30, 1610, he was able to announce to Castelli that the phases had been actually discerned. They are not visible to the naked eye, to which the planet is simply a brilliant speck, too small to reveal its actual form, which is much more globular than that of the earth. Its diameter is about 7,826 miles, or about 93 miles less than that of the earth. Were man placed on the surface of Venus, the earth would look a trifle larger and brighter The than Venus does to us in our sky. mass of Venus is about three-quarters the that of the earth, or 28000 that of the sun; its density is about 0.850 that of the earth; its sp. gr. 4.81, as against 5.66, that of the earth. While a stone falling toward the earth passes through the first a little more than 16 feet in second, it would, if falling to the surface of Venus, pass through about 13 feet only in the same time. The excessive brightness of Venus makes the time of its rotation somewhat doubtful; it is provisionally placed at 23 hours 21' Its mean distance from the sun is 67, 000,000, its greatest distance 67,500,000, 66,600,000 miles. These and its least numbers show that its orbit departs but slightly from a circle. Its periodic time is 224.7 mean solar days. Observation on the passage of the planet over the sun's disk is the best method of ascertaining the distance of the great luminary; it has also revealed the fact that Venus has an atmosphere, but its composition is as yet uncertain. Old observers thought they detected a satellite; modern astronomers have not confirmed this view, and believe it to have been founded on optical delusion.