The planet Venus passes through all the phases that the moon does, and for the same reason. It does not give out any light of its own, but shines entirely by reflecting the light of the sun. Its path around the sun lies between the earth and the sun. When beyond the sun, as seen from the earth, its fully illuminated side is turned toward us, and it appears round, like the full moon. When it is this side the sun and coming in between us and the sun, we see only part of the side that the sun is shining on, and it no longer appears round. As it comes in more between us and the sun, it assumes the crescent phase, becoming a thinner crescent, until it is a mere thread of light, and is lost in the superior brightness of the sun. Under very rare conditions, at extremely long intervals, it passes across the sun's disk as a round, black spot, or makes a “
transit,” as it is called. The last transit of Venus occurred
December 6, 1882. The next will occur
June 8, 2004. Few persons now living will see this transit of Venus. And many failed to see the transit of 1882 or
1874 (for they come in pairs eight years apart).
Venus is but little smaller than the earth, being 7700 miles in diameter. We, perhaps, never see the real surface of Venus (as we do in the case of Mars). It has a very dense atmosphere, which is believed to be constantly filled with clouds which hide from us a view of the planet’s surface. Nothing is known definitely as to the length of its day. Some astronomers believe that it always presents one face to the sun, so that any beings upon it would have eternal day or eternal night, according to their location on the planet. Other astronomers believe that the length of the day of Venus is not much different from that of our own day. One thing is certain, it has a dense atmosphere, like the earth. Its year is 225 of our days.
