Sulfur dioxide combines with atmospheric oxygen to form sulfur trioxide, which reacts with water vapor to form sulfuric acid. The result is acid rain, which some scientists think could be causing damage to northeastern Canadian and American hardwood forests. All our energy comes from the sun. Our problem is to convert enough of it to useful forms. Our best hope for an abundant energy source here on earth is nuclear fusion .
Fission starts with a heavy element that has large atoms, such as uranium.
Uranium nuclei, orbited by clouds of electrons, are so large that they are unable to remain in one piece and tend to lose fragments. These emitted fragments dissipate their energy as heat, but they are still radioactive and continue to break down into smaller atoms in time. This is the fission process, and these radioactive fragments create a serious waste disposal problem. Nuclear fusion begins instead with atoms of the lightest element, hydrogen, abundant in water. Fuel cost is negligible.