On a planet revolving around the star Epsilon Eridani there may be a radio antenna several times as big as a baseball stadium. From it toward other planets revolving around other stars may go messages proclaiming the existence of a high civilization in the Epsilon Eridani system. The Earth may be one of the planets toward which such messages are beamed.
Such is the stuff that dreams are made of—but in this case the dream is shared by highly intelligent and practical scientists. Among them is Dr. Frank Drake, 29, of the National Radio Astronomy Observatory at Green Bank, W. Va., who this week launched an effort called Project Ozma—after the Princess in Author L. Frank Baum's strange and faraway Land of Oz. In Project Ozma, Green Bank's 85-ft. radio telescope is turned toward Epsilon Eridani and another star, Tau Ceti, both of them about eleven light years (66 trillion miles) away. Tuned to the 21-centimeter waves (1,420 megacycles) that come from cold hydrogen in interstellar space, the telescope is so set up that it points for a short time at the target star, then at an empty region beside it. The system eliminates background "noise," and the balance of the signal should contain any message that might be coming from one of the star's planets.
Universal Waves. Another scientist much preoccupied with the possibility of messages from civilizations outside the solar system is Harvard's Nobel Prize-winning Edward Mills Purcell, who with Harold I. Ewen was the first to detect the 21-cm. waves. If nonsolar aliens are sending messages to earth, theorizes Purcell, their first problem is to select the proper radio frequency, and their most likely choice is 21 cm., the sharpest and most universal radio waves that flash through space. Such aliens would reason that if earthlings have an electronic technology, they would know about the 21-cm. waves, and would be tuned to them.
But what message would the aliens send that could be understood by earthlings? Dr. Drake suggests a familiar series of numbers, such as 1, 2, 3, 4. Professor Purcell believes that a simple on-off signal would be more logical as a starter. After that, the messages could progress to mathematical relationships, which are surely the same in all planetary systems. When earthlings understand the aliens' way of saying two plus two equals four, they will have learned the important words "plus" and "equals." Other words and logical concepts could be taught in the same way.
Older Civilizations. Improbable as the notion of message-sending nonsolarites may seem, it is certainly not impossible. Most astronomers now believe that something like 5% of the billions of stars in the Milky Way galaxy have planets that are habitable. If so, there is an excellent chance that some of them support civilizations older and higher than earth's, and that such civilizations might be interested in establishing communications with the planets of other stars.
There is no doubt that radio messages can span interstellar distances. Dr. Purcell estimates that the total power of all the 21-cm. waves that bathe the earth's surface is equal to the power of only one watt, but modern antennas can pick them up easily. And this week's Project Ozma is a first small step in an effort that might take one year or 10,000 to turn a dream into reality.