Vincent Harlton, Age 13, Of Winnipeg, Manitoba, Canada, for his question:

What is nuclear fusion?

The terms nuclear fusion and nuclear fission belong to the atomic age. The words fusion and fission may be confusing to the non scientist, perhaps because they sound so much alike. To the physicist, however, they are opposite methods of releasing nuclear energy. The first atomic bomb was pawered by nuclear fission. The mighty h bomb is powered by nuclear fusion.

In the world of science it has become stylish to talk about nuclear energy rather than atomic energy. This is because the energy is rfleased from the nucleus of the atom. The nucleus, of course, is surrounded by orbiting electrons  the particles which hold together chemical compounds. Electrons yield chemical energy. The tight wad of particles in the atomic nucleus yields the far more dynamic nuclear energy.

Nuclear physicists use two methods to release energy on a large scale. Nuclear fission is atom smashing in which the nucleus is broken into smaller parts and some of its matter released as seething energy. In the first atomic bombs, heavy atoms of plutonium were broken up by nuclear fission.

Nuclear fusion occurs when small atoms or ions are fused together to form larger atoms. You would imagine that nuclear fusion releases less energy than nuclear fission  but this is not so. The mighty h bomb and the seething nuclear powerhouse of the sun are powered by nuclear fusion. In both nuclear fission and nuclear fusion, small amounts of matter are converted into various forms of energy.

The nuclear fusion in the sun, we think, takes place when four ions of hydrogen fus e t0 make one ate of helium. The hydrogen atom has one proton particle in its nucleus and one orbiting electron. In the heat of the seething sun, most electrons

Are stripped away and the lopsided hydrogen atoms becarne ions. Most experts think that nuclear fusion in the sun occurs because of the heat. Ions speed up as the temperature rises. Traveling, say, at 300 miles a second, the hydrogen ions crash and some of them stick together. A few atomic fragraents are left over when four hydrogen ions fuse to form an atom of helium. Billions of these surplus particles of matter are then converted into the nuclear energy which radiates from the sun.

Atomic fission has been tamed to run nuclear reactors for generating electricity. Nuclear fusion, however, would yield far more energy than nuclear fission. But as yet we have no way to do the job economically. The heat required for the fusion of hydrogen ions may be 10,000 greater than a blast furnace—and heat is expensive to produce. But the heat yielded by nuclear fusion is a million times greater than ordinary fire.