Tommy Jenkins, age 9, of Thomasville, North Carolina for his question:

How do clouds stay up in the sky?

Several things help the clouds to stay in the sky, but nothing can keep them up there forever. We may not notice it, but if there is no upward current of air, even the most peaceful cloud is sinking, slowly sinking down. The strange thing is that they can stay there for as long as five minutes. A small stone has to come tumbling down through the air    and small clouds weigh at least 100 tons. The secret is in sizes. Clouds can float in the air because they are made of misty droplets of moisture, too small for your eyes to see.

Gravity uses the same amount of strength to pull everything down to the ground. But a fluffy feather takes longer to drift down than a solid stone. Each little droplet in a misty cloud is on its own. It floats aloft, at least for a while, somewhat like a fluffy minifeather. A cloud is made of air mixed with zillions of these floating droplets. Sometimes warm air rise's straight up from the ground and the draft helps the cloud to stay up there all day    while the wind blows it away.