Sara Solaun, age 11, of Rochester, New York, .for her question:

What really makes the clouds move?

We can say that the winds blow the clouds along. This is true., but nothing in this world is quite that simple. The winds are moving air and the turbulent atmosphere is governed by mighty forces.. The sun and the rotating earth pull the strings that make them blow    and they carry along the floating clouds. Some clouds sail along six miles or more above the earth. But actually all of them are slowly sinking    because gravity gradually pulls them down.

The winds blow because masses of dense, heavy air tend to flow into masses of lighter air, somewhat like water flowing downhill. The sun warms the earth and the earth warms the air in uneven patches. This starts the winds blowing and the spinning earth tends to direct the breezy traffic in circles around the globe. In our latitudes, most of the clouds move eastward because this is the way most of the winds blow.