David Sheen, age 10, of Taber, Alberta, Canada, for his question:

 How do the clouds move?

When a strong wind blows through the treetops, you may look up and watch the clouds riding along with it. We can say that the wind moves the clouds    and this is true. But sometimes we look up and see something that seems to disprove it. Groups of clouds seem to be coming and going in different directions. No, the wind does not push some of them and pull some of them. It carries them all along in the same direction it is blowing.

The secret is this. The wind near the ground does not tell us about other winds that blow along higher up in the airy The wind in the trees may blow westward and carry a flock of low clouds along in the same direction. But a mile or more above our heads, another wind may be blowing eastward. If there are clouds up there, it will carry them along with it. This is what goes on when we see the clouds in the sky moving along in different directions