What causes tides?

I can’t tell you all about tides, but I can tell you the basic idea. The tides are caused by the effect of the force of gravity of the moon. The actual pull of the moon’s gravity isn’t very great. You can’t feel the moon when it goes overhead, but it does have a small effect in a special way. Since the earth is a solid body, the pull of the moon’s gravity acts upon the center of the earth. The ocean is at the earth’s surface, so it is four thousand miles closer to the moon than the core of the earth. So, when the moon is overhead, it pulls on the water more than on the earth. This makes the water bunch up a little under the moon. That’s what is called a high tide.