Cheryl Harris, age 13, of Oromocto, N.B., Canada, for her question:

How can the sun burn without oxygen?

We are used to the idea that candle flames and campfires cannot burn without supplies of oxygen. We also know that the sun is a blazing star. So we naturally assume that it, too, needs oxygen to keep going. Then we learn that there is little or no oxygen around the starry sun. Obviously it burns by some process that needs no oxygen and our 20th century scientists have discovered what this process is.

The sun is a nuclear furnace that works by changing atoms. The tight fisted core of an atom is called the nucleus and the sun burns by nuclear fusion. It fuses the nuclei of hydrogen atoms to create larger atoms of helium. In the process, atomic particles are converted to atomic energy. On a much smaller scale, the same sort of nuclear fusion powers the H bomb. And neither the sun nor the H bomb needs oxygen to change atomic particles into nuclear energy.