The satellite of the earth, from which it is distant 238,800 m., and which revolves round it in 27-1/3 days, taking the same time to rotate on its own axis, so that it presents always the same side to us; is a dark body, and shines by reflection of the sun's light, its diameter 2165 m.; it has a rugged surface of mountains and valleys without verdure; has no water, no atmosphere, and consequently no life.