The sun has a family of other planets which keep circling about it at different distances. The earth on which we live is one of those planets. There are nine planets and their names in the order of their distance from the sun are: Mercury (the nearest), Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto. In addition to these, about 2,000 minor planets, some of them only a few miles in diameter, swarm round the Sun, between Mars and Jupiter. Mereury, the nearest, is about 30 million miles from the sun, less than half the distance of the earth. Naturally, it is much hotter than the earth. It is, therefore, too hot for anybody to live there. Mercury always turns the same face to the sun and its sunny side is about as hot as molten tin. Its cold side is just frozen masses like snow. Mercury is a small planet, only about one-twentieth, the size of the earth. Venus is 67,000,000 miles from the sun and is also distinctly hotter than the earth. It is certainly too hot to support life. Next after Venus, is the earth which revolves about the sun at a distance of 93,000,000 miles. Moon revolves round the earth at a distance of 2,40,000 miles. Moon is a dead world of dry rock and dust and it contains neither air nor water. It is about 1/50 as big and 1/100 as heavy as the earth. It revolves once every 27 days and so we get a new moon about once a month. The moon always keeps the same side facing the earth. The moon, like the planets, is a cold body which is only visible when the sun shines on it and that is why it appears to be in different shapes at different times. When the sun is shining on its farther side, we cannot see it at all and we say there is no moon. When the sunlight creeps gradually round its edge to show first a crescent, then gradually a bigger size. Full moon happens when the sun shines directly on the side of the moon taking the earth.