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Frontispiece: A photographic image of a star field with the addition of desig-
nations of stellar type for some of the stars. The letter designation (e.g., A) in-
dicates the spectral type of the star. The conventional spectral types are O, B,
A, F, G, K, and M, with O-stars being the hottest (effective surface temper-
atures in excess of 30,000 K) and M-stars being the coolest (effective surface
temperatures of 3,000 to 4,000 K; the effective surface temperature of the Sun
is about 5,800 K). The prefix "g" indicates that a star is a giant star, a star that
has moved away from the main sequence. Stars indicated only with the spec-
tral designation are main sequence stars, deriving their energy primarily from
the conversion of hydrogen into helium. The two important aspects of the
figure are first that stars like the Sun, spectral type G, are very numerous in
the Galaxy, and second, in any typical group of stars, most stars are of spectral
types G, K, and M. These types of stars are long lived (10 billion years or
greater). The figure shows that viewed from the perspective afforded by inter-
stellar distances, the Sun would be a rather common and ubiquitous type of
object. This suggests that the Sun's retinue of planetary companions, and
perhaps the intelligent life forms existing on one of these planets, may also be
common and ubiquitous phenomena. (Illustration kindly provided by Prof.
Jesse L. Greenstein, California Institute of Technology, Hale Observatory,
Pasadena, California).

Published in Canada by General Publishing Company,
Ltd., 30 Lesmill Road, Don Mills, Toronto, Ontario.
Published in the United Kingdom by Constable and
Company, Ltd., 10 Orange Street, London WC2H 7EG.

This Dover edition, first published in 1979, is a
republication of the work originally published in 1977 by
the United States Government Scientific and Technical
Information Office as NASA SP-419. In order to conserve
paper, numerous part titles and blank pages in the gov-
ernment publication, as well as the record of Workshop
Meetings held between January, 1975 and June, 1976,
have been omitted from this edition, and the pages have
consequently been renumbered. The main text is com-
plete and unabridged.

International Standard Book Number: 0-486-23890-3
Library of Congress Catalog Card Number: 79-52011

Manufactured in the United States of America
Dover Publications, Inc.

180 Varick Street

New York, N.Y. 10014

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There are few questions that more excite the curiosity, the imagination and the exploratory bent of modern man than the one posed in this study: Are we humans alone in this vast universe? The question is usually expressed in terms of other possible intelligent beings, on other planets. The philosopher in me would want to believe that if there are other intelligent beings, they are also free, and will use that freedom to try to find us. The basic problem to which this study is addressed is similar: Will we use our freedom to find them? What priority should this search have for modern man, everywhere?

Few would disagree with the proposition that we are living in a truly revolutionary age, inaugurated by Sputnik and the first trip to the Moon. In another such age - the Copernican - the prevailing religious or theological thought resisted, with the then current wisdom, the proposition that the Sun and the Universe did not rotate around the Earth. They mistakenly believed that man was the center of the Universe, and that astronomy should reflect that anthropocentric belief. They may ultimately be right about man, though not about astronomy, if we do not ever find intelligent life elsewhere in the Universe. However, we should not be predisposed to accept the proposition that we indeed are alone and unique as creatures possessing intelligence and freedom in this whole vast Universe.

I must now mention God

otherwise quite properly unmentioned in these scientific studies -- and must go a step further and pose the question: Can a religious person, or even more, a theologian, possibly be legitimately involved in, even be excited by these discussions of the possibility of other intelligent and free creatures out there?

Just last week, I was discussing the subject with a Russian lawyer who regarded me with some surprise and asked: "Surely you must abandon your theology when you consider these possibilities?" "Indeed, I don't," I replied. "It is precisely because I believe theologically that there is a being called God, and that He is infinite in intelligence, freedom, and power, that I cannot take it upon myself to limit what He might have done." Once he created the Big Bang - and there had to be something, call it energy, hydrogen, or whatever, to go bang He could have envisioned it going in billions of directions as it evolved, including billions of life forms and billions of kinds of intelligent beings. I will go even further. There conceivably can be billions of universes created with other Big Bangs or different arrangements. Why limit Infinite Power or Energy which is a name of God? We should get some hint from the almost, but not quite, infinite profusion of the Universe we still know only in part. Only one consideration is important here regarding creation. Since God is intelligent, however He creates - "Let there be light" - Bang - or otherwise, whatever He creates is a cosmos and not a chaos since all His creation has to reflect Him. What reflects Him most is intelligence and freedom, not matter. "We are made in His image," why suppose that He did not create the most of what reflects Him the best. He certainly made a lot of matter. Why not more intelligence, more free beings, who alone can seek and know Him?

As a theologian, I would say that this proposed search for extraterrestrial intelligence (SETI) is also a search of knowing and understanding God through His works especially those works that most reflect Him. Finding others than ourselves would mean knowing Him better.

Theodore M. Hesburgh, C.S.C.
President, University of Notre Dame

100383

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PREFACE

Over the past two decades there has developed an increasingly serious debate about the existence of extraterrestrial intelligent life. More recently, there have been significant deliberations about ways in which extraterrestrial intelligence might in fact be detected. In the past two years, a series of Science Workshops has examined both questions in more detail. The Workshop activities were part of a feasibility study on the Search for Extraterrestrial Intelligence (SETI) conducted by the NASA Ames Research Center.

The objectives of the Science Workshops, as agreed at the second meeting in April 1975, were: to examine systematically the validity of the fundamental criteria and axioms associated with a program to detect extraterrestrial intelligent life; to identify areas of research in the astronomical sciences, and in other fields, that would improve the confidence levels of current probability estimates relevant to SETI; to enumerate the reasons for undertaking a search, the values and risks of success, and the consequences of failure; to explore alternative methods of conducting a search; to select, in a systematic way, preferred approaches; to indicate the conceptual design of a minimum useful system as required to implement the preferred approaches; to delineate the new opportunities for astronomical research provided by the system and their implications for system design; to outline the scale and timing of the search and the resources required to carry it out; to examine the impact of conducting a search, and the impact of success or failure in terms of national, international, social and environmental considerations; and to recommend a course of action, including specific near-term activities.

This report presents the findings of the series of Workshops. The major conclusions of our deliberations are presented in Section I. First, an Introduction lays out the background and rationale for a SETI program, and then in The Impact of SETI, we examine the implications of the program. In particular, the Impact section examines the significance of the detection of signals and of information that may be contained in signals from extraterrestrial civilizations.

For those who wish to see some of the arguments in more detail, we have extracted from the discussions of the last two years, six of the most interesting and significant elements of the debate in the form of Colloquies (Section II). Finally, we have documented, in greater depth, a selection of detailed technical arguments about various aspects of the SETI endeavor. This is Section III Complementary Documents.

The reader should note that the Introduction, the Impact of SETI, and the Conclusions, which comprise Section I of this volume, have been prepared by and represent the views of the Workshop as a whole. Sections II and III, on the other hand, have been prepared by the individual authors listed, and while consonant with the major SETI findings, reflect specifically the views and style of presentation of the authors.

In addition to the series of six Workshops, and at the instigation of the participants, two additional series of meetings were held. The first, under the Chairmanship of Dr. Joshua Lederberg of Stanford University, addressed the question of Cultural Evolution in the context of SETI. The

second, under Dr. Jesse Greenstein of the California Institute of Technology, addressed the question of the Detection of Other Planetary Systems. The conclusions of these meetings are presented in Colloquies 2 and 3.

The last of the Complementary Documents (III-15) lists the members of the Science Workshops, our consultants and advisors, and the agendas for the nine Workshop meetings. Detailed minutes of all of the Workshops are available from Dr. John Billingham, SETI Program Office, NASA Ames Research Center, Moffett Field, California, 94035.

I would like to express my appreciation to everyone who has worked with me in this undertaking I must single out first the Workshop members themselves (see Complementary Document 15), and in particular Joshua Lederberg and Jesse Greenstein for their major contributions in taking the chair at their respective special Workshops (see Colloquies 2 and 3). The assistance of the NASA Centers, and specifically of the SETI Groups at the Ames Research Center and Jet Propulsion Laboratory must be recognized, together with numerous contributions from consultants and speakers who have addressed and advised us. Last, but by no means least, special thanks are due to Vera Buescher, Secretary to the Ames SETI Team, for her loyal and indefatigable attention to the thousand details which went into the preparation of this report.

In conclusion, I would hope that our report will provide a logical basis for the evolution of a thoroughgoing but measured endeavor that could become a significant milestone in the history of our civilization.

We recommend the initiation of a SETI program now.

Philip Morrison
Chairman

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