A brief history of SETI
Only a relatively short time ago, we thought ourselves to be unique in the universe, but the more we find out the less this seems likely to be true. In the 1960s people began to ponder the question: if we are not alone, then where is everyone? A good account of the beginning of the SETI communication work is Frank Drake’s 1992 book, Is Anyone Out There? The important early papers are in the book Interstellar Communications, edited by A.G.W. Cameron and published in 1963. It includes the paper by Giuseppe Cocconi and Philip Morrison in the journal Nature in 1959 that first mooted the possibility of surveying nearby stars for microwaves of intelligent origin, and also the seminal paper by Robert Schwartz and Charles Townes in the same journal in 1961 on the possibility of communication by laser. The Cocconi and Morrison paper resulted in activity at radio frequencies seeking interstellar signals. As Drake describes it, Project OZMA was the first organized experiment to look for signals. The selection of radio frequencies was based on the fact that large antennas existed; the suspicion that aliens might opt to transmit at the emission frequency of neutral hydrogen atoms at 1,420 megahertz, which is one of the quietest parts of the spectrum; and because the Earth’s atmosphere is transparent at this frequency. What is more, frequencies around that number are protected for radio-astronomy purposes, hence interference signals should be reduced in both number and magnitude. Drake got OZMA initiated in 1960 using the Green Bank antenna of the National Radio Astronomy Observatory.
KeywordsRadio Frequency Heliocentric Distance Habitable Zone Nearby Star Deep Space Network
Unable to display preview. Download preview PDF.