Adrian Toy, age 7, of Duluth, Minnesota, for his question:

What holds down the earth's atmosphere?

Our big round world is very strong. It has an invisible force called gravity that reaches out and hugs all smaller objects within its reach. It hugs us tight to the surface on the globe whether we live in America or way around on the other side of the world. When you drop a stone, the earth's gravity pulls it down to the ground in a hurry. It also pulls down tiny, light things such as feathers and specks of dust. The earth's gravity also pulls at the airy atmosphere. It refuses to let its filmy gases escape and go zooming off into space. Oh yes, our old earth holds on tight to what rightfully belongs to it.

The air is made of tiny molecules that are far too small for our eyes to see. They are gases  and in gases the molecules and atoms are separate and very, very far apart. But each one has a tiny tiny weight. The whole atmosphere weighs zillions of tons, and the earth's gravity holds and hugs it close, like a filmy blanket around the whole globe.