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SETI, Pessimists and Optimists

Page history last edited by Audrey Zimbelman 15 years, 4 months ago

Summary of Today's Topic



      By the 1960's, our galaxy was found to be much larger than previously thought. By 1959, it was widely accepted that our Sun is a typical star, and that we should direct our telescopes to certain regions of the sky. In that same year Morrison sent radio signals into outer space, hoping to recieving a reply sometime in the future. He chose the frequency of hydrogen to send the signals because that is the most basic element, and therefore might be more easily identifiable by other organisms as a sign of intelligence.


     At the same time, but completely independent of Morrison, Frank Drake developed the same idea. He was a radio-astronomer and worked privately on his secret project called "Project Ozma." In his opinion, since we are capable of sending radio signals, the extraterrestrials should have the same capability. He determined what he believed to be the optimal frequency to avoid background noise both from earth and from space. Drake then organized the Green Bank Conference in 1961. This was a meeting of physicists and astronomers interested in "project Ozma." Here he revealed the Drake equation (N = R x Fs x Fp x Ne x Fl x Fc x L) which could, in his opinion, calculate how many intelligent civilizations there are in the universe. Drake wanted to send radio signals into space. However, other men wanted different signals to be sent. Some of the other proposed sending infrared signals, probes (to monitor the galaxy, watching for signs of intelligent life), or mazers (like lasers, they are a distortion-free way to send signals across the galaxy). One of these men was Freeman Dyson who suggested that we should attempt to detect infrared radiation. He is credited with the Dyson sphere, which he believed other beings might have built around their sun. This shell would allow them to harness materials but would give off raditation. By looking for this radiation, we could essentially find extraterrestrial beings.


     Drake also believed there were three different types of civilizations (the Kardashev Scale). Type one is like our own civilization - the ability to send and receive radio signals -  and therefore we should not look for signals from them because we would have trouble picking them up. We should look for the more advanced signals from types two and three. Type two civilizations would be capable of getting energy from their own star, an would be the making of a Dyson sphere. Type three civilizations would be able to use energy from their whole galaxy. This was a time of soaring optimism in the desire for contact with other worlds. Although it did not relate to SETI-style searches, it is interesting to note that Drake made no mention of a Type Zero civilization, which would be a society that does not yet have the ability to manipulate or translate radio signals, much like earth 100 years ago.


     The acronym SETI stands for the Search for Extraterrestrial Life. It is based on natural merging of the concepts of the Copernican model, modern astronomy/radio astronomy, and the principle of plentitude. SETI researchers scan the sky for radio waves, technology, and signs of artifical activity that could be the product of intelligent extraterrestrials. When it was first founded, SETI was supported financially by the United States government, but it has since lost governement backing and is now a private non-profit agency. The SETI program has expanded to include amateur astronomers with a computer program that allows regular people to listen for alien signals from their homes.


     Carl Sagan was one of the most optimistic people when it came to the topic of extraterrestrial life. In his article "Encyclopedia Galactica" he goes into detail on Drake's equation. The R = rate of star formation, the first F = fraction of good stars that have planetary systems. Ne = number of planets around those stars within the "ecoshell." Fl = the fraction of those planets where life develops. Fc= the fraction of inteligent species with communicative technology. L= lifetime in communicative phase. After using all of the calculations he had at hand, Sagan came to the conclusion that there are 10 to the power of 7 different intelligent species in our universe. He goes on to explain that if we were to recieve a mesage from another civilization, it might possibly be in a series of prime numbers. These numbers do not accur normally, they are too original to be random and therefore it would prove that an intelligent species was sending the code.  The Drake equation was made partially to be used as a propoganda tool for increased funding, and partically it separates the overall probablitiy into several smaller problems which makes it easier to solve.



      By 1975, there were many more skeptics making their way onto the scene. Michael Hart was one such skeptic. He was aware of the profound implications of finding extraterrestrials, he said in his article An Explanation for the Absence of Extraterrestrials on Earth, "The question is not a foolish one; indeed, it is perhaps the most significant of all questions in astronomy" (128), however he ultimately concluded that they do not exist.He said that extraterrestrials are not here on earth, so therefore, they are not anywhere in the universe, and he called this "Fact A". He refuted many of the common arguments for pluralism. He breaks up his arguements into 4 explanations:

  1. Physical Explanations
  2. Sociological Explanations
  3. Temporal Explanations
  4. Perhaps they have come

One such argument is that we have not been visited because they live too far away and it would take too long. Hart says that the extraterrestrials could have a much longer lifespan and therefore could have been here by now. The second argument is that the aliens don't want to find us. This was refuted by Hart because he said that would be generalizing all alien species and saying they are all the same and that it is very unlikely that none of them would want to contact us. The third argument he refutes is that there hasn't been enough time for them to get here. He says that it would only take about 600,000 years to colonize the entire galazy and therefore these extraterrestrials can't exist. These civilizations could have emerged before us and by now have take over the entire galaxy. He concludes with these two exclamations: 1) an extensive search for radio messages from other civilizations is probably a waste of time and money and 2) in the long run, cultures descended directly from ours will probably occupy most of the habitable planets in our Galaxy (135).



Key Terms

Maser- microwave amplification by stimulated emission of radiation, creates a form similar to that of a laser.


Drake Equation - N = R x Fs x Fp x Ne x Fl x Fc x L - The equation to find the estimated number of civilizations existing in the galaxy.


Fact A: Extraterrestrials are not here; therefore they do not exist






 Related Sources



 Carl Sagan Portal : http://www.carlsagan.com/


Drake's Equation: http://www.activemind.com/Mysterious/Topics/SETI/drake_equation.html


SETI and the galactic colonization hypotheisis:  http://www.astrobio.net/news/index.php?name=News&file=article&sid=1745&theme=Printer


Greenbank conference: http://www.daviddarling.info/encyclopedia/G/GreenBankconf.html


History of the Drake Equation: http://www.daviddarling.info/encyclopedia/G/GreenBankconf.html


Project Ozma: http://www.time.com/time/magazine/article/0,9171,874057,00.html







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