The moon shining in the sky at night is so beautiful that long ago ignorant people, who did not know what it was, worshipped it like a goddess under different names. The Syrians thought it was a goddess called Astarte, the Greeks called it Artemis, and to the Romans, it was the goddess Diana. Of course, we are not so silly as to worship the moon now, because we know what it really is; but we admire its beauty, and poets are fond of singing about it in their poems.
We know now that the moon is a round ball like the earth on which we live, only much smaller. Just as our earth goes round the sun, taking a year to do the journey, so the moon goes round the earth once every month. So it is sometimes called the earth’s servant. The light of the moon is not its own light; for it is not a mass of fire like the sun, but a cold, dead mass of rock. Moonlight is really second-hand sunlight; for the moon looks bright to us at night because it is lit up by the sun. So we say it borrows its light from the Sun. That is why moonlight is dim and soft, as compared with sunshine.
During each month, the moon seems to change its shape. At first, it looks like a thin, curved line in the sky, it is then called the crescent moon. Every night it grows larger until it looks like half a circle, and we call it the half-moon. It goes on growing, until it is three-quarters of a circle, and is called the “gibbous” moon. At last, it is a full circle of white light, and then it is the full moon. After that, it begins to become smaller again-becoming once more “gibbous”, half, and crescent until at the end of the month it disappears altogether. Of course, the moon does not really change its shape: all the time it is a round ball. But we can see only that part of it which is lit up by the sun, and the lit-up part increases or decreases as the moon changes its place in the sky.
The use of the moon to us is that it gives us light part of the month; it also causes the tides of the sea by pulling the water towards it as it goes round the earth.