There are, in fact, places in the heavens where radiation is unusually high in quantity and in energy. Can we be witnessing such enormous mutual annihilation? Indeed, it is not altogether inconceivable that we may still have new types of forces and new sources of energy to discover. Until about 1900, no one suspected the existence of nuclear energy. Are we quite sure now that nuclear energy brings us to the end, and that there is not a form of energy more subtle still, and greater? In 1962, for instance, certain puzzling objects called “quasars” were discovered far out in space, a billion light-years or more away from us. Each one shines from 10 to 100 times as brilliantly as an entire ordinary galaxy does, and yet may be no more than a hundred-thousandth as wide as a galaxy. This is something like finding an object 10 miles across that delivers as much total light as 100 suns. It is very hard to understand where all that energy comes from and why it should be concentrated into so tiny a volume. Astronomers have tried to explain it in terms of the four interactions now known, but is it possible that there is a fifth greater than any of the four? If so, it is not impossible that eventually man’s restless brain may come to understand and even utilize it. FOOTNOTES [1]See _The First Reactor_, another booklet in this series. [2]See _Nuclear Reactors_ and _Nuclear Power Plants_, companion booklets in this series. [3]See _Breeder Reactors_, another booklet in this series. [4]See _Thorium—and the Third Fuel_, another booklet in this series. [5]See _Controlled Nuclear Fusion_, another booklet in this series. QUOTATION CREDIT Inside front cover Copyright © by Abelard-Shuman, Ltd., New York. Reprinted by permission from _Inside the Atom_, Isaac Asimov, 1966. READING LIST Basic Books _Basic Laws of Matter_ (revised edition), Harrie S. W. Massey and Arthur R. Quinton, Herald Books, Bronxville, New York, 1965, 178 pp., $3.75. Grades 7-9. A nontechnical presentation of atoms and the laws governing their behavior. _Biography of Physics_, George Gamow, Harper & Row, Publishers, New York, 1961, 338 pp., $6.50 (hardback); $2.75 (paperback). Grades 9-12. A history of theoretical physics. _Discoverer of X Rays: Wilhelm Conrad Roentgen_, Arnulf K. Esterer, Julian Messner, New York, 1968, 191 pp., $3.50. Grades 7-10. This interesting biography includes a brief, but very helpful, pronouncing gazetteer of the German, Swiss, and Dutch names in the text.