(Previous Page) Part 4:The Origin Of Life    

SETI, Fermi and the Anthropic Principle

      All the questions regarding the possible origin of extraterrestrial life come together in the Fermi paradox, named for Enrico Fermi. The Fermi Paradox asks: if there are so many civilizations out there, as many current calculations suggest that there are, where is everybody? Specifically, if an extraterrestrial race of intelligent beings has formed a super-advanced civilization, then they should have begun intergalactic exploration. Had an intelligent species formed elsewhere in the galaxy in the past, it should have attained a very high level of technology and likely also curiosity--they should have tried to contact life from planets other than theirs, such as on Earth. Thinkers trying to solve the Fermi paradox have offered many solutions over the years, which fall into three categories: extraterrestrials are here, extraterrestrials exist but have not communicated yet, and extraterrestrials do not exist. There are many sub-solutions for each area, and they range anywhere from being plausible to far-fetched.

     Some of the solutions offered are more likely than others.  The most unlikely solutions are the social solutions, such as the zoo scenario, the interdict scenario, the planetarium hypothesis, or that extraterrestrials just want to stay at home.  These solutions are most unlikely because they require all extraterrestrial civilizations to behave the same way for a very long time. It is hard to imagine that every race of extraterrestrials would want the same things, or that a certain race would continually be averse to extraterrestrial contact throughout the age of their civilization.  The most likely solutions are combinations of various suggestions.  For example, a combination of the solutions that it the races are too far away for communication and that everyone is listening for communications instead of broadcasting.

     Some of the solutions to this, while very "Pop Science-Fiction" in nature, do an excellent job of explaining why we seem to be alone. For example, in Webb's book, solution 22 refers to one civilization that creates self-replicating probes that are sent out to search the far reaches of the galaxy. Somehow, be it on purpose or by accident, their programming includes a line that requires them to destroy any intelligent life they might find. Despite how uncomfortable that might make us as a species, it does rather handily answer the question "where is everybody?"

     In contrast, many of the more believable theories fall into the category of "They do not exist". The solutions that our class found most probable were numbers 9, 36, 40, and 42. From the section "They do exist" we considered  Solution 9 most likely: The stars are far away (Webb, Where is Everybody?, p. 62). This is one of the most straightforward solutions; it simply says that the stars are too far apart to allow for interstellar travel, no matter how technologically advanced the civilization becomes. The only problem with this solution is that it only resolves the issue of us never being visited by extraterrestrials, and does not address the lack of communication. From the catergory of "They do not exist" we liked Webb's solution number 36: Continuously habitable zones are narrow (Webb, Where is Everybody?, p. 158). This states that Earth is in a seemingly perfect place for life to emerge in our solar system. Earth recieves a constant amount of light and heat from the sun that is necessary for life. The sun does not give inconsistent heat that would scorch or freeze the planet's surface. Typically, a CHZ, or continuously habitable zone, is defined as a region in which an Earth-like planet can support liquid water for one billion years - the timescale evolution presumably requires to develop complex life. These CHZ zones are very rare in our galaxy, therefore it seems very likely that there are no other forms of intelligent life within our galaxy.  We also achieved some consensus on Solution 40: A planetary system is a dangerous place--this solution lists all of the different ways that things from our solar system and Earth itself could halt life. The list includes the ideas of "snowball Earth," super-volcanos, and many different mass extinction possibilities. The idea is that there are so many ways for life to be wiped out on any planet, and that makes exterrestrial life even more unlikely (Webb, Where is Everybody?, p. 172). Finally, there is solution 42: The moon is unique. The moon is the only "double planet" in our solar system and it might be rare. The moon was probably formed when a large meteorite glanced off the Earth when the planet was still fairly young. The resulting debris coalesced and formed our moon. Much evidence suggests that life may not have been able to emerge or evolve without the presence of the moon.

     Despite the fact that many of the solutions to the Fermi paradox involve the nonexistance of extraterrestrial life many scientists remain convinced that life exists in the universe and have developed a program to try and find it.  This program works independently of NASA which actively sends probes and lander out into our solar system.  This program simply listens for communication from extraterrestrial civilizations.

     SETI, the Search for ExtraTerrestrial Intelligence, began in 1959 with the start of the space age.  The SETI program was a natural merging of the Copernican model, modern astronomy, and the principle of plentitude. By the 1950's and 1960's, the universe was agreed to be much larger than previously thought. The framework for SETI is a vast network of dishes and telescopes that scans the skies for signals that might be emitted from extraterrestrial civilizations.  SETI first began sending signals at the frequency of hydroden, our most basic element. This was believed to be the frequency we should also look for as a response.

     Drake came onto the scene attempting to do the exact same contact system independently of the others. He organized a conference in 1961 with many other ethusiasts and revealed the Drake equation. This equation, according to Drake, could calculate the number of intelligent civilizations that should be present in our galaxy or the universe. Essentially, Drake's equation estimates the number of sun-like stars and the number of planets around these stars, and then applies a conglomeration of probabilities (such as planets remaining in a CHZ for long enough periods, planetary densities being habitable, etc.) to weed out planets not suitable to the development of extraterrestrial life.  This was a time of soaring optimism and Drake was initially a large factor in earning public funding for SETI.

     SETI kept its government funding for two years before Congress decided to remove it, and it is currently a private-funded endeavor. So far, SETI has recieved no signals from space, but there are many factors that could explain this (e.g. we haven't searched long enough; we can't decode the signals aliens are sending; etc.). Those who believed in SETI remained very optimistic until about 1975 when pessimism began to grow.  Mars was generally accepted to be our best hope for extraterrestrial life within our solar system, and searches for life on Mars had revealed no strong evidence for such life. Scientist Carl Sagan was one of the most opimistic of the SETI program.  He said that if a signal were recieved from an alien civilization, "it would be made up of mostly prime numbers."  He used the Drake equation to predict the number of intelligent civilizations in the universe. His estimate for the number of E.T. civilizations was around 10 million. 

     SETI is one of our answers to the "box analogy". Since the only way we know to try and find another marble is to keep opening up boxes, SETI is our way of X-raying the boxes, looking for something small and round. While it is faster than opening each box by hand, there is a good chance that it would not detect something that isn't exactly what we're looking for. We've gotten better at identifying false-positives, but the system isn't perfect. The Arecibo telescope in Puerto Rico sent a message in 1974 to the globular cluster M13, which is 25,000 light years away.  No signal has been sent back to us. 

     Nicolai Kardashev thought of three types of classifications for civilizations that surpassed the vision of Dyson.  He came up with Type I, Type II, and Type III civilizations.  The Type I would have the technology similar to ours now.  Type II civilizations would be able to capture the energy of their own star and be able to build a Dyson sphere for an example. Type III would be able to use energy from their whole galaxy.  He says that finding Type I civilizations would be a low probability and we should search for Type II and Type III civilizations instead.

     As far as the question of extraterrestrial life goes, neither Fermi nor SETI have actually been able to bring us any sort of answers. Fermi's Paradox brings about a number of ways of looking at the issue logically, and can help us eliminate a number of improbable explanations. SETI has introduced a possible connection to willingly communicative extraterrestrial species, but there has been no connection thus far. Therefore, despite the respective cleverness of both, neither has truly made mankind any closer to locating, reaching, understanding, or even being aware of any specific alien life.

(Next Page) Part 6: The Principle of Plenitude