In a figurative sense, the Search for Extra Terrestrial Intelligence(SETI) predates the dawn of human history, ancient humans perceiving the stars of the night sky were gods and deities watching over them. To more primitive humans the stars were representative of the other world, heaven, nirvana, the unity of the limited and unlimited, the mortal and spiritual realms. The stars were representative of the quintessential sphere all humans could aspire to, and the status of perfection that we might ascend to should we be made worthy by mortal effort. And these beliefs pretty much persisted until the sixteenth century, when a well educated astronomer named Nicolas Copernicus took exception with the way another astronomer, Claudius Ptolemy, had explained the movement of the celestial orbs 1500 years earlier.
Knowing that challenging the status quo in the 16th century would likely result in a barbeque in his honor, at which he also would be the objective participant, Copernicus would not allow the formal publication of his thesis until he was on his deathbed, but he did see one of the 500 copies printed of his book, On the Revolutions of the Heavenly Spheres, some time before he took his final breath.
Born two years after Copernicus died, Giordano Bruno would grow up to become a Franciscan monk with an avid curiosity about the Cosmos. He read Copernicus's book and was an instant convert to Copernican heliocentrism, thereafter traveling around Europe sharing his enlightenment with others. Along the way, Bruno developed some of his own ideas as well, and one of them had a whole lot to do with the search for extraterrestrial intelligence. In fact, in contemporary terms, Giordano's ideas could easily be thought of as the incipient stage of SETI. You see, once Giordano has subscribed to the premise that God had not put the earth at the center of his creation, but instead, the Earth was but one of six planets known in the day that revolved around the Sun, and the stars were other Suns which likely had Earth-like planets revolving around them as well, that there were equally likely to be other beings inhabiting these distant worlds as well. And so it is, that we acknowledge Giordano Bruno as the originator of SETI in its contemporary modality, for his was truly the first notion of it.
It would take almost three hundred years after Giordano Bruno was tortured for 8 years by the inquisition, and finally burnt at the stake for his ETI assertions among other things, before humans would begin again to consider that there may indeed be intelligent life beyond Earth. But before SETI could go much beyond the pages of science fiction novels, a whole lot of discovery and innovation would be required. By the end of World War II necessity had instigated the inventions and the inventions had produced the discoveries. The cosmos had become a far more complex place than anyone had ever thought it to be, and it had been around a whole lot longer than any previous notion of it had held. In 1950, and not unlike Giordano Bruno, the distinguished physicist Enreico Fermi took to pondering the existence of extra terrestrial life, and it occurred to him by rational induction, that it should be both abundant and obvious. But is so, then where is the evidence that should be all over the place to conclusively establish the existence of extraterrestrial intelligence? It is a postulate today referred to as Fermi's paradox and may well have been the impetus to begin anew the quest of discovery with respect to alien existence.
In 1959, Giuseppe Cocconi and Philip Morrison of Cornell University wrote a paper titled Searching for Interstellar Communications, outlining the potential of extraterrestrial communication and suggesting that a search be launched to investigate the possibilities. The first actual scientific project to do so, called project Ozma, was undertaken the following year by Cornell University Astronomer Frank Drake. The Ozma project looked at two near earth stars, Tau Ceti and Epsilon Eridani in the 1.4 Ghz frequency range. A total of 150 hours of observations were recorded over a four month period, but analysis of the data revealed no intelligent signals. In 1961, Frank Drake developed an equation which predicted, based on 7 variables, the number of stars in the galaxy having planets which might support intelligent life. A second experiment conducted by Benjamin Zuckerman and Patrick Palmer and called Ozma II, ran from 1973-76 and looked at 650 near by stars. Again, no affirmative results were detected.
Around the same time in the 1970's, some researches suggested that alien planets within a 160 light years might be using high powered laser beams in the infrared spectrum to communicate with Earth. Interest in the possibility sparked the first optical SETI project in 1973. In 1974, a 3 minute long transmission at very high power was beamed from Arecibo in the direction of the Great Globular cluster (M3) in the constellation Hercules, 21,000 light years away. With an estimated million stars occupying a space about 100 light years across, the star cluster provides the highest ETI probability within close proximity to earth, making it the ideal direction to aim a hi were here message from Earth at. You can actually hear the message at: http://www.youtube.com/watch?v=6qQRQyEodsE In the Northern Hemisphere summer sky the cluster is visible as a faint fuzzy blob to the naked eye. It is about 17 arc-minutes across, about half the size of the Moon. It can been seen well with binoculars and is probably the deep space object with the greatest detail you can observe with a 4 inch telescope in the Northern Hemisphere.
The first two space craft that would exit the solar system, Pioneer 10 and 11, launched in 1972 and 1973 respectively, were equipped with a plaque giving directions as to where the craft originated from, and diagrams of a human female and male to indicate the species that sent the probes. Dr. Carl Sagan and Dr. Frank Drake committed ET enthusiasts designed the plaque with assistance of Sagan's second wife Linda Salzman Sagan. More elaborate golden phonograph records were sent along with the Voyager 1 and 2 spacecraft, launched in 1977, including narratives and musical selections. Pictographic instructions were included on the back side of the records showing how to they could be played. Of the four spacecraft, only Voager 1 has a remote chance of being snagged by some alien space travelers as it will pass within 1.6 light years of the star AC+79 3888 in the Ophiuchus constellation.
In 1979, the University of California at Berkeley's astronomy department started a project called Search for Extraterrestrial Radio Emissions from Nearby Developed Intelligent Populations (SERENDIP). Initially the project was conducted using equipment at UC Berkeley's Radio Astronomy Observatory in Hat Creek California. Later the experiment was moved to the National Observatory at Green Bank Virginia and finally to Arecibo where the research project is ongoing. The SERENDIP project does not require exclusive use of the Arecibo Radio Telescope, but instead is accomplished concurrent with other observations being made.
The SETI Institute was organized as a private nonprofit organization in 1984 and today represents the most comprehensive program of SETI research. In 1993, the organization picked up the pieces of the NASA SETI project HRMS that had been canned by the congress. The SETI Institute fittingly renamed the project Phoenix, after the bird of Greek mythological importance. The project got under way in 1995, and had completed surveillance of the 800 targeted stars for the project by 2004. The Phoenix project turned up no evidence of ETI, but it blazed a trail that future projects could benefit from and build on.
Meanwhile, in 1994, another nonprofit SETI venture called SETI League was getting off the ground. The SETI League projects mission was to develop a worldwide capability of mostly amateur ETI search enthusiast using common inexpensive 3-5 meter TV satellite dishes. The ultimate goal was to network as many as 5000 such dishes to essentially build the biggest antenna on Earth. To date the organization boasts 110 dishes on line.
Perhaps one of the most significant SETI projects, and one which brings us current in our retrospective review, is the Allen Tellescope Array (ATA), a joint project of UC Berkeley's Astronomy department and the SETI Institute. The initial phase of the project was funded in large part by Microsoft cofounder Paul Allen and named in his honor. Forty-two of the eventual 350 20-meter dishes comprising the final version of the ATA are already in place and operational at the Hat Creek Radio Observatory(HCRO) in Northern California. As of the dateline for this article, there has been no report from HCRO of any messages from deep space being received yet, but they are expecting one at any moment, and are poised ready to capture what SETI Institute director Dr. Jill Tarter would tell you, will be the most profound incident in the history of the human species.
M3 - ASTRONOMY The Definitive Guide, 2003 Barns and Noble.
NASA SETI - http://history.nasa.gov/garber.pdf
Ozma - http://en.wikipedia.org/wiki/Project_Ozma
Pioneer Voyager - http://en.wikipedia.org/wiki/Pioneer_plaque