The Ozma Problem and the Fall of Parity

Abstract

On controversial scientific questions for which there is a scarcity of empirical data, scientific opinion sometimes shifts back and forth like the changing fashions of women’s clothes. The skirt is low in one decade, high in the next, then back down it goes again. When I was in college it was fashionable among astronomers to think that planets were extremely rare in the universe, on the theory that the earth was the result of an improbable collision or near approach of two suns. Quite possibly (it was believed) life in the cosmos is confined to our solar system, perhaps even to the earth. Today, informed opinion has swung the other way. Astronomers now suspect that planets are extremely common in the universe. Perhaps there are billions of them in our galaxy alone, millions of which may support intelligent life. If so, it seems likely that inhabitants of some of these planets, with a knowledge of science equal to or in advance of our own, may be trying to communicate with other planets.