Intelligent Life, ETIs, Aliens, and UFOs Part 2
About the prospect of intelligent life, ETIs, aliens, and UFOs, history of arguments, possibility of life in this or other solar system, NASA begins the search.
Is there intelligent life on other planets?
Astronomers currently believe the best place to look for ETI is around stars like our own sun, which may support earthlike planets--some possibly inhabited. Since the nearest such star is 4.3 light-years away, it isn't practical to conduct the search with manned or unmanned space probes. The fastest spacecraft ever launched from earth would take 80,000 years to travel that distance. Instead, scientists are using a more promising device--the radio telescope.
It's pure speculation whether civilizations thousands of years in advance of earth use radio communications. Perhaps there are better techniques we know nothing about. Presumably, though, societies close to our own in technical development generate some form of radio energy that "leaks" into space, just as radar beams and TV signals spill out from earth. Astronomers hope to detect this energy using such monstrous machinery as the 1,000' radio dish at Arecibo, Puerto Rico. This telescope has the capability to transmit and receive signals from any similar facility in our galaxy.
It may be a long search. Radio waves vary in frequency and power. If ETI is transmitting, which frequency is it using? Is the signal strong enough to excite our receivers? How many stars should we monitor? How long should we listen? Would we be sure to recognize a signal if we picked it up?
In the summer of 1960, scientists at the National Radio Observatory in Green Bank, W.Va., conducted a preliminary experiment, Project Ozma, to examine some of these questions. They listened for a total of 200 hours to 2 stars within 12 light-years of earth: Tau Ceti and Epsilon Eridani. They listened on a frequency of 1,420 megahertz, a natural emission frequency of hydrogen. Because of the earth's rotation, the antenna could be directed at the stars only for a certain period each day. Nothing unusual was heard. Since then, more sophisticated short-term projects have been conducted in the U.S. and the Soviet Union, none productive.
In the summer of 1971, NASA funded a 3-month study called Project Cyclops to assess the feasibility of using multiple radio telescopes to listen for ETI at distances of up to 100 light-years. The study proposed a spectacular array of at least 1,000 antennas, spread out over a 10- or 20-mi. area. No action was taken on the proposal, but it remains under discussion.
Besides leakage, once our telescopes begin listening, there are 2 other types of extraterrestrial signals we might encounter: radio beacons and interstellar messages. The 1st are signals transmitted by an advanced society to announce its presence to cultures not yet discovered; the 2nd are transmissions exchanged by societies already known to each other. The 1st, if they exist, should be easy to understand since they will likely be based on information familiar to most technological communities. Not so the 2nd, which almost certainly would be too sophisticated for us to decipher. Imagine a telegraph operator in 1840 trying to understand data transmissions from an Apollo spacecraft.
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