Our nearest neighbour is the moon. In the sky, the moon and the sun seem to be of the same size because the moon is much nearer.
The moon makes the tides（潮汐）—the changes in the level of the sea. The moon and the sun together pull the sea. In some parts of the world, the difference between "high tide" (when the sea is very near to the land) and "low tide" (when the sea is far away from the land) is very big. This is very important to ships.
The moon is very different from the earth. Gravity（地心引力）on the moon is one-sixth of that on the earth. There isn't any air. During the day, the part of it that face the sun is very, very hot but at night it is very, very cold. Nothing can live on the moon.
If the moon goes between the earth and the sun, we have an eclipse of the sun（日食）. The moon stops the light from the sun and it is dark in the day.
If the earth goes between the moon and the sun, we have an eclipse of the moon. The moon goes into the shadow（影子）of the earth and it disappears for a few minutes.
