Dessa Sue Gilbert, age 8, of Monroe, Michigan, for her question:

What set the sun on fire?

Our dazzling sun does not blaze away like an ordinary fire. It is a monstrous atomic power plant somewhat like thousands of hydrogen bombs all going off at the same time. Nobody could start such a furnace with a match or put out the blaze with water from a fire hose. Our atomic bombs and atomic power plants need very special materials. Special things must be done to them and lots of special work must be done to make them work. And the huge atomic sun is like them but much, much bigger. it has lots of the right materials to make an atomic furnace. And about five billion years ago, the right things happened to start the atomic furnace going. Its filmy gases were jam packed tight together and whirled around and around in a heavy ball. The big ball became hot, hotter than you can imagine. These were the right things to make the atomic furnace start up by itself. And the monster furnace has enough of the right materials to go on blazing for at least 12 billion more years.