[image] This is Man on Earth Speaking to Space, the message beamed from Arecibo Observatory to M-13. *** Life In The Universe The Universe is a rather large place, large enough to contain all the wonders imaginable and quite a few which we have not approached in even our wildest dreams. Of all the things which may exist outside the bounds of our planet Earth, surely the most wondrous of these is life itself. The search for extraterrestrial life is an exciting and important part of radio astronomy. Scattered through interstellar space, between the stars and dust clouds, are isolated molecules of materials such as hydrogen, formaldehyde and methyl alcohol - some of the basic ingredients of life on Earth. The Arecibo radio telescope can be used to gather data for analyzing and quantifying these molecules, as well as to search for other freely floating chemicals. These chemicals may very well be the seeds from which life on Earth evolved. Important confirmation of this theory may come when the Viking landers conduct the first rigorous search for life on Mars in the summer of 1976. If life has evolved on the planet Earth, in our solar system, why may it not have evolved elsewhere in the Universe? There are some 200 billion stars in our Milky Way Galaxy alone. It is now fairly certain that a number of stars, at least in our part of the Galaxy, have planets of about the mass of Jupiter. Present methods can not detect less massive planets in orbit around other stars, but it is generally accepted that stars with planetary systems are not exceedingly rare. Surely, on some of the other planets in our galaxy, the correct conditions have obtained for life of some sort to begin its slow way along the evolutionary process. Among 200 billion stars, odds of even a million to one begin to look rather plausible. The most exciting possibility of all is that there may not simply be life elsewhere in the Universe, but that it may be intelligent life. There are billions of stars in our galaxy and there are billions of galaxies in our universe. It is not so difficult to believe that intelligent beings inhabit more than one planet in this vast universe. Some of these *** M-13 Response Received Less than 10 days after a formal announcement of life on earth was beamed toward a far-off cluster of stars known as M-13 from the Arecibo Observatory in Puerto Rico, an "answer," purported to be from outer space, was received. Cornell professor and director of the National Astronomy Ionosphere Center (NAIC) Frank D. Drake who, with his staff, initiated and composed the "life on earth" message, received this answer by telegram Nov. 25: "Message received. Help is on the way. -M-l3." It came through on the NAIC telex machine in Ithaca via the International Telephone and Telegraph system. The true identity of the sender has not been confirmed, but Drake suspects that it may have come from practical jokers on the observatory staff at Arecibo. *** beings have probably reached the same level of understanding of natural phenomena as have human beings; some are more, and some are less, advanced. With all of them we must feel the most basic kinship and a yearning to know for certain that we are not alone in the face of the vastness of the Universe. *** Listening For Intelligence It is indeed tantalizing to think that, right now, like an inaudible whisper, radio messages from light years away are falling into the valley of the Arecibo reflector bowl - messages that could be heard if their direction and frequency were known. When the upgraded Arecibo radio telescope was dedicated on November 16, 1974, a message was sent commemorating the occasion. Our first intentional attempt at radio communication with extraterrestrial life is now travelling at the speed of light through the Milky Way toward a globular cluster of some 300,000 stars known as M-13. It will take about 25,000 years to reach its destination. Any reply will take as long to return to Earth. Although the message was beamed from Arecibo for only three minutes it is entirely possible that one day a reply will be received. (see figure) In the meantime, it is within Earth's technological ability to decide the question of whether there are other beings Out There trying to communicate with each other and with us. No more stupendous moment in the history of the Earth can be imagined than the first intellectual interchange with an intelligence other than our own. The Arecibo radio telescope is now the premier instrument in the world for such an undertaking. Given careful planning and an adequate observing program, there is a genuine probability that this most important of frontiers will be crossed for the first time. *** Thanks to Cornell University and the National Astronomy and lonosphere Center for permission to use illustrations and to make extensive use of published material on the Arecibo Observatory. *** Annotated Bibliography Hey, J. S. The Evolution Of Radio Astronomy. New York: Science History Publications, 1973. A semi-technical account of the history of radio astronomy, its instruments and its accomplishments. Misner, C. W., K. S. Thorne and J. A. Wheeler. GRAVITATION. San Francisco: W. H. Freeman and Co., 1973. A massive book on an utterly fascinating topic. Takes at least calculus through simple partial-differential equations to really understand, but it is a mind stretching book to browse. Just reading the chapter headings and subheadings is a trip in itself. Sagan, Carl. The Cosmic Connection. New York: Dell Publishing Co., 1975. An unrestrained intellectual romp through the concept of extraterrestrial life. Sagan, Carl and Frank Drake. "The Search For Extraterrestrial Intelligence." Scientific American. Vo. 232, No. 5, pp. 80-89, May, 1975. A current appraisal of the subject. Contains the Arecibo message and its translation. Strom, Richard G., et al. "Giant Radio Galaxies." Scientific American. Vol. 233, No. 2, pp. 26-35, August, 1975. Research into the largest known objects in the Universe. Sullivan, Walter. We Are Not Alone. New York. Signet Books, 1966. One of the first popular books on the subject of extraterrestrial life. Includes an account of Project Ozma and Frank Drake's first proposed interstellar message. *** 56