Our nearest neighbor 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—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 for ships.
    The moon is very different from the Earth. Gravity on the moon is six times weaker than that on the Earth. There isn't any air. During the day, it 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 we have night 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.

沿东西方向直线运动列车突然紧急刹车，但车箱里乘客看到光滑水平桌面上的小球却朝着自己滚动起来了，这是由于小球____的缘故，若乘客是面朝西坐着的，则列车原来朝着____方向运动的。