Return-path: X-Andrew-Authenticated-as: 7997;andrew.cmu.edu;Ted Anderson Received: from beak.andrew.cmu.edu via trymail for +dist+/afs/andrew.cmu.edu/usr11/tm2b/space/space.dl@andrew.cmu.edu (->+dist+/afs/andrew.cmu.edu/usr11/tm2b/space/space.dl) (->ota+space.digests) ID ; Tue, 14 Nov 89 01:36:17 -0500 (EST) Message-ID: Reply-To: space+@Andrew.CMU.EDU From: space-request+@Andrew.CMU.EDU To: space+@Andrew.CMU.EDU Date: Tue, 14 Nov 89 01:35:53 -0500 (EST) Subject: SPACE Digest V10 #244 SPACE Digest Volume 10 : Issue 244 Today's Topics: EJASA, November 1989 - Volume 1, Number 4 ---------------------------------------------------------------------- Date: 13 Nov 89 15:25:25 GMT From: wrksys.dec.com!klaes@decwrl.dec.com (CUP/ASG, MLO5-2/G1 6A, 223-3283 13-Nov-1989 1025) Subject: EJASA, November 1989 - Volume 1, Number 4 THE ELECTRONIC JOURNAL OF THE ASTRONOMICAL SOCIETY OF THE ATLANTIC Volume 1, Number 4 - November 1989 ########################### TABLE OF CONTENTS ########################### * ASA Membership Information - Don Barry * Does Extraterrestrial Life Exist? - Angie Feazel * Suggestions for an Intragalactic Information Exchange System - Lars W. Holm * A View From Down Under - Michael Carini ########################### ASA MEMBERSHIP INFORMATION The Electronic Journal of the Astronomical Society of the Atlantic is published monthly by the Astronomical Society of the Atlantic, Inc. The ASA is a non-profit organization dedicated to the advancement of amateur and professional astronomy and space exploration, and to the social and educational needs of its members. Membership application is open to all with an interest in astronomy and space exploration. Members receive the ASA Journal (hardcopy sent through U.S. Mail), the Astronomical League's REFLECTOR magazine, and may additionally purchase discount subscriptions to ASTRONOMY, DEEP SKY, and TELESCOPE MAKING magazines. For information on membership, contact Alan Fleming, ASA Treasurer, at 2515 N.E. Expressway, Apt. N-2, Atlanta, Georgia 30345, U.S.A., or call the Society recording at (404) 264-0451. ASA Officers and Council - President - Don Barry Vice President - Bill Bagnuolo Secretary - Scott Mize Treasurer - Alan Fleming Board of Advisors - Bill Hartkopf, David Dundee, Anita Kern EJASA Editor - Larry Klaes Observatory Search Committee - John Stauter Georgia Star Party Chairman - OPEN Advertising Committee - Paul Pirillo, Willie Skelton Travel Committee - Chris Castellaw Sales Committee - Jim Bitsko Society Librarians - Julian Crusselle, Toni Douglas Telephone the Society Info Line at (404) 264-0451 for the latest ASA News and Events. ARTICLE SUBMISSIONS - Article submissions on astronomy and space exploration to the EJASA are most welcome. Please send your on-line articles to Larry Klaes, EJASA Editor, at the following net addresses: klaes@wrksys.dec.com, or ...!decwrl!wrksys.dec.com!klaes, or klaes%wrksys.dec@decwrl.dec.com, or klaes@wrksys.enet.dec.com If you cannot send your articles to Larry, please submit them to Don Barry, ASA President, at the following net addresses: don%chara@gatech.edu, or chara!don@gatech.edu, or don@chara.UUCP You may also use the above net addresses for EJASA backissue requests and ASA membership information. Please be certain to include either a net or U.S. Mail address where you can be reached, along with a brief background about yourself. DISCLAIMER - Submissions are welcome for consideration. Articles submitted, unless otherwise stated, become the property of the Astronomical Society of the Atlantic, and although they will not be used for profit, are subject to editing, abridgment, and other changes. This Journal is Copyright (c) 1989 by the Astronomical Society of the Atlantic. DOES EXTRATERRESTRIAL LIFE EXIST? by Angie Feazel Since the time that humans first developed the ability to walk on two legs, we have gazed wistfully at the stars, wondering what they were. We now know that those minute pinpoints of light are actually giant glowing balls of gas, but we still look at them and wonder if we are the only forms of life in the Universe. The answer to the question, however, requires first the definition of life's properties. The characteristics of life are widely varied but are generally assumed to be composed of the four basic traits of growth, reproduction, reaction to stimuli, and the ability to ingest and process external material (WEBSTER'S DICTIONARY). This is a very rudimentary definition of life, and does not discriminate between the simple amoeba and the very complex human being. While the amoeba may be mildly interesting, the intelligent, communicative, complex organism is by far the more interesting of the two and the type that we would most wish to find. Because of the vast interstellar distances, finding these advanced beings, assuming for a moment that they do exist, is an extremely difficult task. For instance, other than physical contact, receiving a radio signal or some other form of communication would be the only method of proving the existence of such life. Light travels at roughly 300,000 kilometers per second (186,000 miles per second). In order to measure interstellar distances, it is convenient to utilize this constant velocity (c) in measuring huge separations in space. We use the light year (ly), which is the distance light travels in one year. In order to illustrate our scale of distance, we may use a sample from our own solar system: Our planet Earth is approximately 150 million kilometers (93 million miles) from our Sun. It takes eight minutes for the light of the Sun to reach our planet. Therefore, it is said that Earth is eight light-minutes from the Sun. Radio signals are an invisible form of electromagnetic radiation similar to light, so they travel at the same speed as visible light. If we were to beam a radio signal at the nearest star other than our Sun - the Alpha Centauri trinary system - it would take 4.3 years for that signal to reach it. If there were life at the star, it would take an additional 4.3 years for our signal to be answered, provided that this life were intelligent, communicative, and possessed of the curiosity to receive and reply to our inquiry. The issue to be investigated here is the probability that advanced beings do exist elsewhere in the Universe. To that end, scientists have spent much deliberation in defining and estimating factors necessary for extraterrestrial life to develop and be found. For example, in 1961, a noted astronomer named Frank Drake proposed a very important algebraic equation. This equation, though we use numerical values, is not strictly mathematical. It is a method of structuring our thinking and approach to the question of the existence of extraterrestrial life. (Furenlid) In order to understand the Drake equation, we must make some definitions. We denote the total number of instances of detectable planetary life by the variable N. First, we assume that N is the product of factors, which increasingly narrow the number of stars and planets which could prove habitable. Since we know that life has developed at least once in the Universe (on Earth), we may assume that none of these factors is zero. Second, we must base our estimates on what we know. Our solar system is the only example we have of life emerging anywhere; therefore, our estimates must be educated guesswork. Each factor of the equation represents a condition which is necessary for the emergence of life. By beginning with a relatively large number (R* - See below), we may whittle away at it by using current astronomical data and assumptions to arrive at N, the predicted number of intelligent civilizations. The equation as stated by Drake is written as follows: N = R* fp ne fl fi fc L where: R* = The number of stars in the Milky Way Galaxy. fp = The fraction of these stars with planets. ne = The fraction of these planets suitable for life. fl = The fraction of suitable planets which develop life. fi = The fraction of life-bearing planets developing intelligence. fc = The fraction of intelligently-inhabited planets who have formed civilization and harnessed radio or other means to communicate. L = The lifetime of such a communicative civilization in a ratio to the age of its star. The only number of which we can be reasonably certain is the value for R*, the number of stars in our galaxy, the Milky Way. Our galaxy resembles a pinwheel with a giant central bulge. It is about one hundred thousand ly from side to side and ranges from 900 ly to 3000 ly thick. We are located approximately thirty thousand ly from the central nucleus. Our galaxy contains too many stars to physically count, and many are not visible because they lie on the other side of the galaxy and are obscured by the interstellar gas and dust of the central bulge. Even though we cannot observe these stars directly, we can calculate the mass of the galaxy and infer the number of stars by observing our own solar neighborhood and extrapolating (Furenlid). If we do this, we discover that there are several hundred billion stars in the galaxy (McDonough, 71-76). This may sound like a very large number of potentially habitable places, but the figures get significantly smaller once we begin multiplying by the other factors necessary for communicative life. If we plot the temperatures of stars against their luminosities on a graph, we get what is known as the Hertzsprung-Russell (HR) Diagram. The letters O B A F G K M along the bottom correspond to temperature and the numbers along the left correspond to luminosity or brightness. Our Sun is a G2 type star on the "Main Sequence", which means that it is neither very hot nor very cool. Because we must assume that our solar system is typical, we will include only G stars as potentially life-bearing. Therefore, we may take our initial number R to be 125 billion. (Furenlid) As a star collapses from a cloud of gas and dust, a quality called angular momentum causes formation of a central condensation surrounded by a thin disk of matter. At this point it seems the system then either evolves into a planetary system or a binary/multiple star (Ridpath, 19-20); but how might we detect a planet? Each planet exerts a certain amount of pull on the Sun. That pull from a planet as comparatively small as Earth around some other star would be unobservable. By measuring the deviation of a star from its presumed normal course, some investigators say they have discovered the existence of Jupiter-or-larger-sized companions around several of the nearest stars (Talcott, 18; Sagan and Drake, 80). If these stars had Earth-sized worlds, then those planets would be undetectable. If it is given that any single star would tend to form planets, and that approximately seventy-five percent of the stars visible from Earth are multiples, then we must reduce that 125 million by three-fourths, which gives us our estimate: fp = 0.25 (Furenlid). Our definition of life leaves much to imagination. As Thomas McDonough states, "On Earth, our experience with chemistry has been highly biased. We were born on a lukewarm, watery planet with an oxygen atmosphere and carbon-based life...." (102). His observation is the one most likely to influence our value for ne. First, temperature would seem to be a major factor in the search for a suitable habitat. A very convenient window for our estimates would be between the freezing and boiling points of water. If the temperature were too cold, the molecular bonding processes would be too sluggish to give rise to life. Likewise, if the temperature were too hot, molecules complex enough to begin life would break apart. Our Earthly temperature is warm enough to allow chemical interactions to take place yet cool enough to prevent any compounds from breaking up. We must also assume that some sort of liquid must be present to give those molecules a medium in which to bond. Hal Clement suggests that the components of that liquid should be relatively abundant. Hydrogen and helium compose ninety-eight percent of the mass in the Universe. As helium does not combine with other elements, hydrogen is the most likely basic candidate. There are many elements which combine well with hydrogen, but the four which seem to be the most reasonable are carbon, nitrogen, oxygen and fluorine (Clement). The compounds formed are methane, ammonia, water, and hydrogen fluoride. Although these compounds are gaseous under normal, terrestrial circumstances, they could be liquid if the temperature were low enough or if the pressure were high enough. Any one of them could be the fundamental building blocks for an extraterrestrial form of life. Thirdly, there must be some sort of force present in order to keep gasses in liquid form. Atmospheric pressure serves this purpose. The gasses above the surface of a planet exert a certain amount of force upon all things beneath them, thus keeping liquid in its place. Atmospheric gases also protect the surface of a planet from potentially damaging rays of its sun. Our Sun emits ultraviolet rays which would kill every unprotected living organism. The ozone layer in Earth's atmosphere efficiently absorbs the majority of these killing rays. Though there are between one and three planets in our solar system to have developed at least two of these characteristics, only one planet developed all three. Moderate temperatures, abundant liquid, and a complex atmosphere are observed on the only planet which has spawned life. This is roughly ten percent of the planets in the solar system, so we will take our value for ne to be 0.1. Frank Drake states that "there seems to be near unanimity of opinion that fl is very nearly 1" (325). As stated earlier, fl is the number of habitable planets where life evolves (Drake, 324). We know that life began very early on Earth, probably within the first billion years. The rapidity with which it developed on our Earth suggests that life must be common (Furenlid). Scientists can even create the basic building blocks of life, such as amino acids, under conditions mimicking those believed to have been present on prehistoric Earth (Drake, 325; Shklovski and Sagan, 230). These laboratory experiments illustrate the first step in a series of steps which "had to be completed before complex life could evolve...." These steps are: 1 - The formation of small organic molecules from Earth's original materials. 2 - The combination of these small molecules into the long chains necessary for living organisms. 3 - The formation of isolated, reproducing systems from these long molecules. 4 - The formation of cells and multicellular organisms. 5 - The evolution of the different species of plants and animals. (Rood and Trefil, 62) The first three are exclusively physical and chemical. Four and five deal with biological processes because they deal with living organisms. Amino acids apparently do nothing but form long chains, but some of these chains act as "enzymes" - they modify the way other chains are made. Once a sufficiently sophisticated system of amino acids and enzymes have formed, they begin metabolic-like reactions. They can take in and process external material, thus facilitating their growth and subsequent reproduction. The enzymes act as glue to cause molecules to bind together and grow (Rood and Trefil, 70-73). Step four begins the process of natural selection. When mutations occur in developing cells, the cells pass the new trait onto succeeding generations, provided the first cell survived the mutation. In this way, primitive life trudged along for the first two billion years after life developed (Rood and Trefil, 78-79). Then, about five hundred million years ago, sexual reproduction began. With the advent of sexual reproduction, primitive life suddenly had enormous potential for evolution. Organisms could combine portions of themselves and form new combinations which would retain the genetic mutations and offer the new creature a greater chance for survival. Since we know that life developed on the only planet which had the very circumstances which we think necessary for life, our number for fl could reasonably be considered to be 1. As we move further away from the realm of the astronomer and farther into the realm of the biologist, our numbers rely even more heavily upon extrapolation and conjecture. Though we can not necessarily assume that every planet which develops life will evolve intelligence, it seems likely that once intelligence manifests, it would not die out. Robert Rood and James Trefil have stated that there are six events crucial to the development of intelligence: 1 - An oxygen-laden atmosphere. 2 - Migration to land. 3 - Stable body temperature. 4 - Hand and eye development. 5 - Tool use. 6 - Evolution of a social structure. Until one or two billion years ago, oxygen was poisonous to the life existing on Earth. Those species that were able to adapt to the new atmosphere gained the advantage of increased metabolic processes. As the brain consumes an incredible amount of energy, the elevated energy level became the catalyst for increased intelligence. The second step, migration to land, would have been impossible if there had not been enough oxygen in the atmosphere to filter out the damaging ultraviolet radiation from the Sun. The protection that this new layer of oxygen provided offered enough shelter that an organism could move with relative comfort to land. The brain requires a consistent temperature to continue functioning. The development of a stable body temperature allowed the organism to bypass the awkward practice of "sunning itself in order to bring its body temperature up." (Rood and Trefil, 88) As our Sun radiates light mainly in the visible part of the electromagnetic spectrum, the development of sight is advantageous for avoiding predators, pitfalls, and other potentially dangerous situations. Once some sort of appendage "exists along with the eyes" (88), the organism would be able to fight and manipulate items in the environment. The use of tools is the next step. When the organism learns to utilize external tools, it immediately gains an immense advantages over the less advanced predators. The development of a social structure among advanced creatures enabled "...groups of thinking animals to coordinate hunting and a defense against predators...and survive more often. Intelligence, being a survival trait, would lend strength to the survival of the fittest (Simpson, "This View of Life", as quoted by Sullivan, 252). At the Green Bank conference where Drake first presented his theory, Phillip Morrison argued that "...intelligence would always appear, sooner or later, because of 'convergence'...the tendency of species, evolving along highly diverse routes, to converge toward life forms that, because of certain basic laws, resemble one another." (Sullivan, 252) Following this chain of reasoning, we assume that any planet which develops life will evolve intelligence. Therefore, our value for fi will be 1. Frank Drake defines a communicative civilization as "a civilization of intelligent beings having a technology sufficiently advanced to permit detection of the civilization over interstellar distances (324)." Just because a civilization develops the technology advanced enough to communicate does not mean that the society will develop the desire to do so. It could be possible that with the emergence of intelligence and technology, a given race would acquire curiosity and the urge to make itself known. Our intelligence, technology, and curiosity have pushed us to take our first small steps into the Cosmos. So because the race may have the capacity to communicate but not the desire, fc = 0.5. Of all of the values in the equation, L is the most uncertain. As we must end up with a value for N with no dimensions, L must be expressed as a fraction of the age of the civilization's parent star. We think that the average life span of a G star is about ten billion years, so we would divide the age of the civilization by the life of the star. As of yet, we do not have even one example of the lifetime of such an advanced civilization. Since our society has not yet ended, we must rely totally upon guesswork. A civilization may last for one hundred, ten thousand, or one million years. There are three views regarding the value of L: One can take an optimistic view and argue that the civilization will broadcast signals as long as its star continues to provide energy. Or, that the civilization will continue to broadcast as long as it is unable to travel in the depths of outer space. Once an efficient means of transport is discovered, humans could transverse the galaxy in one million years. The same could be said for another civilization. Interstellar communication would be facilitated by travel because two-way communication would take far less time "in person" than with the years or centuries long delays of radio. Thus, the optimists place this value at ten million years (Rood and Trefil, 101). On the pessimistic side, one could argue that beings with technology akin to ours would destroy themselves before they could make contact with another planet. Our global tensions have escalated to the point where many people think that we will utilize the nuclear weapons that we have at our disposal and therefore destroy the very civilization many are trying to preserve. Because we may not be the only beings with the potential for self-destruction, the pessimists favor the value for L = 100. For our own purposes, we will adopt a more moderate figure which is a compromise between the two: L = 10,000/10,000,000,000 or 1/1,000,000. There are those who would make strident objections about our estimates for some of these factors. We are assuming that single stars form planets (Meylan). We do not yet have conclusive proof that other planetary systems exist, so our solar system may be unique. Thomas McDonough states that "Some scientists claim that the evolution of life is so complex, the chances of it happening elsewhere are infinitesimal" (9). Two of these scientists, Fred Hoyle and Chandra Wickramasinghe, feel that in the time that we have had on Earth, there would be no way for "...randomly assembling the particular sequence of DNA atoms which would give rise to life...." (as quoted by McDonough, 67). The assumption that life develops independently on a planet is implicit in the Drake equation. How do we know that our planet was not "seeded" by beings from another planet or by spores from a comet? The answer is that we do not know. Doctors Francis Crick and Leslie Orgel are firm believers in the theory that extraterrestrials, either deliberately or inadvertently, "planted" some form of microorganism and "we evolved from that" (35). Though we have no way of proving this theory wrong, we think that the harsh conditions in outer space would kill any organism sent to populate Earth. As Robert Rood and James Trefil point out, if a spore were to be ejected from a planet, the gravity of the nearest and largest celestial object would attract it. In our solar system, that would be the Sun (108). The spore would have to navigate the depths of interstellar space and find a suitable planet on which to evolve. The chances of this happening by pure coincidence is virtually zero. Of course, if another civilization were to have "seeded" Earth, we must then ask, "Where and how did that "seeder" originate?" We assume that life will originate on a planet because the radiation dangers in outer space work against the seeding hypothesis (Rood and Trefil, 107). If amino acids were to develop in the vacuum of space, the chances of their being able to get close enough to form chains of any kind are virtually zero. The assumption that extraterrestrial life is carbon-based is also implicit in the equation. Carbon is the only element which conforms to our expectations of what is necessary. It is plentiful, it forms chains long enough to begin molecular structure, and it operates at the temperate limits stated earlier. Silicon behaves similarly, but it falls short for many reasons. It does not form chains long enough to begin molecular structure unless the temperature is low enough to support nitrogen in liquid form. In our experience, this is much too low to support life as we know it (Rood and Trefil, 111-113). Another question is: Does the planet need to have a satellite to create tidal pools in which the proteins can form? Earth's Moon is one of the largest satellites in our solar system. There is an ongoing debate as to whether the presence of tides aided the primordial organisms in their transitions to land. Those that favor this theory suspect that the tidal forces of the Sun would be sufficient to serve this purpose (T. Gold, as quoted by Sagan, 143; Meylan). Therefore, while the presence of a moon would be beneficial, its absence would not be critical. It could be that the planet on which that society resides is covered by an invariable blanket of clouds or that the society is located under the seas (Rood and Trefil, 97). The inhabitants would have very little way of knowing that there is an "outside" or an "outer space". But perhaps the biggest fallacy of the Drake equation is the assumption that an extraterrestrial civilization would use a readily detectable form of communication. To use an extreme example, if a civilization were to develop a means of communication based upon smell or taste, how would it be detectable over interstellar distances? The differences in technology could be an insurmountable barrier (Meylan). With our numerical values in place of the variables, the equation now looks like this: N = 125 million x 0.25 x 0.1 x 1 x 1 x 0.5 x 1/1,000,000 When we compute the numbers, we discover that N = 1.56. According to these calculations, there is at least one intelligent, communicative civilization at any given time in the Milky Way Galaxy. We must keep in mind that the Drake equation is only a tool and can be used to support one's own viewpoint. If one had a preconceived notion as to what one would wish N to be, one could alter the values of the numbers and increase or decrease them drastically. For instance, if one were to expand R to include F and K stars, then one could get a much higher result. One could assign a much larger number to L on the assumption that a more advanced civilization would discover an artificial means of living indefinitely. On the other hand, one could significantly reduce the numbers on any available pretext, and get a value for N less than one. We know that N cannot be much less than one because of the nature of the problem. The value for N seems to be a reasonable and it corresponds with our observations. We may conclude that, while the Drake equation is not infallible, it offers adequate means of guiding our thinking in the search for extraterrestrial life. References - Clement, Hal, WHERE THERE'S LIFE..., Byron Preiss Visual Publications, In Press. Crick, F. H. C., and L. E. Orgel, "Directed Panspermia", THE QUEST FOR EXTRATERRESTRIAL LIFE: A BOOK OF READINGS, Donald Goldsmith, University Science Books (Mill Valley, California, 1980) Drake, F. D., "Radio Search for Extraterrestrial Life", CURRENT ASPECTS OF EXOBIOLOGY, edited by G. Mamikunian, Pergammon Press (1965) Edelson, Edward, WHO GOES THERE?, Doubleday and Company, Inc. (New York, 1979) Goldsmith, D., and Tobias Owen, THE SEARCH FOR LIFE IN THE UNIVERSE, Benjamin/Cumming Publishing Co. Inc. (Menlo Park, California, 1980) McDonough, Thomas R., THE SEARCH FOR EXTRATERRESTRIAL INTELLIGENCE, John Wiley and Sons, Inc. (New York, 1987) Ridpath, Ian, MESSAGES FROM THE STARS: COMMUNICATION AND CONTACT WITH EXTRATERRESTRIAL LIFE, Harper and Row (New York, 1978) Rood, Robert T., and James S. Trefil, ARE WE ALONE?, Charles Scribner's Sons (New York, 1981) Sagan, Carl, editor, COMMUNICATIONS WITH EXTRATERRESTRIAL INTELLIGENCE (Cambridge, Massachusetts, 1973) Sagan, Carl, "Direct Contact Among Galactic Civilizations by Relativistic Space Flight", THE QUEST FOR EXTRATERRESTRIAL LIFE: A BOOK OF READINGS, Donald Goldsmith, University Science Books (Mill Valley, California, 1980) Sagan, C., Drake, F. D., "The Search for Extraterrestrial Intelligence", SCIENTIFIC AMERICAN, 232, May, 1975. Shklovski, I. S., and Carl Sagan, INTELLIGENT LIFE IN THE UNIVERSE, Holden-Day, Inc. (San Francisco, California, 1966) Sullivan, Walter, WE ARE NOT ALONE: THE SEARCH FOR INTELLIGENT LIFE ON OTHER WORLDS, McGraw-Hill Book Company (New York, 1964) Talcott, Richard "Possible Planetary Systems Discovered", ASTRONOMY, v15, September, 1982. Tipler, Frank J., "Extraterrestrial Intelligent Beings Do Not Exist", FRONTIERS OF MODERN PHYSICS, Rothman, Tony et al., Dover Publications Inc. (New York, 1985) Consultants - Ingemar Furenlid, Associate Professor of Astronomy, Georgia State University. Tom Meylan, Graduate Student, Department of Astronomy, Georgia State University. Special thanks to the Georgia State University Department of Astronomy. SUGGESTIONS FOR AN INTRAGALACTIC INFORMATION EXCHANGE SYSTEM by Lars W. Holm This article is pure speculation on how to operate and manage an information interchange ultimately through the Milky Way Galaxy. The technicalities and economics of such an undertaking are not taken into consideration here, only some fundamental issues as I see them. The pros and cons of SETI (Search for ExtraTerrestrial Intelligence) have been discussed ad nauseam, and I will only briefly state the crucial points in my view. 1 - The existence of other planetary systems comparable to our solar system. 2 - The existence of other planets with Earthlike conditions. 3 - The existence of intelligent life forms other than humans. 4 - The existence of other technical civilizations. 5 - The desire for information exchange. There need not be any necessary causal relationship between these points, even if it is natural to suspect that this is the case; but disregarding the question of an intelligence not emerging on a planet, these point should be affirmed to establish a "common ground" with humankind as of today. To my knowledge, not even Point One has been answered positively. Point Five does merit some discussion: What is the sender and receiver gaining by such a project? For the sender, it must be a bit more than a "Kilroy was here" message, and the receiver does not wish to open the box of Pandora. The only answer to the last question is that we will have to wait and see when a message arrives, if ever. One kind of safe and meaningful information will be briefly mentioned later. Setting the ifs aside, let us assume there are other civilizations distributed around our galaxy, communicating with each other and working on establishing contact with new civilizations like ours. How could this be achieved in a practical and rational way? As a carrier of information, electromagnetic radiation presents itself as an obvious solution. The technical problems of which frequencies, bandwidth, encoding and signal strength to be used is beyond my knowledge and will not be mentioned here. The main problem is that we have not managed to detect any intelligent signals yet. One conclusion of this may be that the Milky Way Galaxy is not full of intelligence lining up to shout at newcomers, or on the other hand, they might be politely waiting for the upstarts to knock on the door. I do not see any clearcut answer to this dilemma; then again, we might not even be deemed fit for polite company by more advanced beings. The question of time lag is worth some consideration; indeed, it is one of the main problems of effective interstellar communication: How to exchange information across tens, hundreds, even thousands of light years in roughly the same time span. It is very important to bear in mind that we are not talking about telephone conversations or radio hams DX-ing (transmitting overseas) on the shortwave. Everybody who considers the problems of SETI knows this very well, but instant two-way communication is an integral part of our civilization, so the concept of communication with a time lag of generations is quite alien to us at present. However, it is not necessary to go back further than to the area of sea exploration in human history before we have a similar situation, to set out into the unknown and hopefully return years later with tales of wonder. An even better analogy regarding a large time span is the Melanesian kula chain: Tokens of good faith were once exchanged among the peoples of the islands of the Western Pacific Ocean, constantly passed along in a great circuit, the means of transportation being sail and oar. How long information transfer will take depends on the available medium, not on what our culture regards as conversation. These examples illustrate that the problems of considerable time lag are not insurmountable. The concept of what I have in mind is a network of "nodes", constantly sending and receiving information to and from other nodes, without waiting for confirmation. An analogy may be a WAN (Wide Area Network, with emphasis on Wide). To make this a bit more feasible on the galactic scale discussed here, a couple of additions may be suggested: The message is returned to the sending node, with some additional information to serve as a "receipt", and most important, the message is beamed further on to star systems having a potential to serve as new nodes. In several hundred thousand years, a network like this might span the whole of the galaxy. The basic assumption for a scheme like this to succeed is that a minimum number of civilizations exist to "pick up the ball and pass it on". What is important to consider in this network concept is that the nodes are to function more or less on a peer-to-peer basis, and it must be possible for new nodes to place their information among the existing information; and at the same time leaving room for still more information further down the chain. On the other hand, at least some nodes must have the role of "moderator" to prevent the signal from being saturated with information. A node firmly established in the network will receive the signal from various nodes and, depending on the size of the network and how long the node has been connected to the network, will receive some of their own earlier messages. The signal should be regarded as an everchanging stream of information criss-crossing its own path, partly repeated and constantly deleted from and added to. The topology of the net should be regarded as non-deterministic; i.e., new nodes appearing and old ones disappearing and reappearing randomly. One kind of information that would be relevant to transmit in a network like this would be astronomical data, perhaps the only kind of information being universally (no pun intended) comprehensible. For one thing, civilizations participating in the network would, per se, have astronomical knowledge. In addition, nodes will have a different view of the Milky Way Galaxy depending on their location: Our solar system, for example, has a fairly poor viewing angle on phenomenon occurring along the galactic plane except in our relative vicinity. Among Earth's meteorologists the World Weather Watch (WWW) is a necessity for good weather forecasts, so why not a Galactic Astronomy Watch (GAW)? On the time scale of an interstellar network, considerable changes should be noticable among the stars, nebulas, and other celestial objects of our galaxy. Here I have tried to present some ideas of how contact between stars might operate. There are many unanswered and unposed questions, but one thing is for certain: The human race may never know if there is anybody else among the stars if we do not knock on the galactic door and listen. A VIEW FROM DOWN UNDER by Michael Carini One of the benefits of being an astronomer is having the opportunity to travel to places you normally might not have the chance to visit. One example is the South American country of Chile, home to three observatories, including the Cerro Tololo Interamerican Observatory (CTIO). For seven nights in September of 1988, I had the unique opportunity to observe. It is a long trip to CTIO, starting with a roughly ten hour commercial jet ride to the capitol, Santiago. Usually, there is a stopover at some place like Lima, Peru, or Buenos Aires, Argentina. Once the international flight lands and you survive customs, there is either an eight hour bus ride, or an hour and a half flight (La Deco, the national airline) to the coastal town of La Serena. This is the home of the observatory headquarters. Only an hour and a half ride into the Andes remains to get to the Observatory. So two days after you've left Atlanta, Georgia, you find yourself on top of a mountain, somewhere in the Andes; but life at the observatory is easy for a visiting astronomer. The lodge rooms are nice with patios that overlook a valley. On the other side are the Andes - a spectacular view, especially if the higher peaks have snow on them. Meals are provided and are very good - it's easy to gorge yourself even if you're not quite sure what it is you are eating! The lodge lies below the telescopes, so you are given a Volkswagen Beetle to move around the mountain. Believe me, you need the car; it's quite a hike up to the observatory. On clear days, the sunsets are something to behold. Usually you can see the so-called "green flash" - a flash of green light that appears on the western horizon just after sunset. I had never seen this before and was expecting a single flash of green. Instead, what I saw was several consecutive flashes of green along the western horizon; but the best treat comes after twilight: On a dark, Moonless night, the southern sky is spectacular. The Magellanic Clouds, satellite galaxies of our Milky Way Galaxy, are an amazing sight; M42, the Orion Nebula, pales in comparison. The Milky Way stretches across the sky and really looks "milky". There are some odd sights, too, such as the constellation Orion rising upside down, or Canis Major on his back. Scorpius fills almost a quarter of the sky - talk about a big bug! Looking north, you can find some old friends - Cygnus, Lyra, etc., were all there, but very far north. Since the purpose of the trip was scientific, let me spend a minute on the science I did. I was observing on the 90-centimeter (36-inch) telescope, using a CCD (Charge Coupled Device) camera. The objects I was observing were two BL Lacertae objects. BL Lacs are a subclass of quasars; they undergo large amplitude variations in visual brightness. In particular, I was searching for optical variations on time scales of less than one day, and with amplitudes of a tenth of a magnitude or less. These particular objects are at southern declinations, hence the obvious need to observe from a southern hemisphere observatory such as CTIO. I could continue, but the idea should be clear. As beautiful as the southern sky is, however, I still prefer the northern sky and all its wonders. Perhaps that is because no matter where I go, I'll always be a Yankee at heart! THE ELECTRONIC JOURNAL OF THE ASTRONOMICAL SOCIETY OF THE ATLANTIC November 1989 - Vol. 1, No. 4 Copyright (c) 1989 - ASA ------------------------------ End of SPACE Digest V10 #244 *******************