For centuries, humans have wondered if there might be intelligent life on other planets. With the goal of turning this wonder into a scientific pursuit, the SETI Institute was founded in 1984.
SETI (www.seti.org) stands for the Search for Extraterrestrial Intelligence, and its major effort has been to search the heavens with very large radio telescopes listening for radio signals that have a pattern expected of messages created by sentient beings.
These telescopes are capable of detecting very faint signals and were often plagued by the radio noise created here on Earth. The idea was that since we were sending powerful radio signals back and forth to one another across our planet, and since these signals leaked out and could be detected far out into space, aliens might detect them and attempt to contact us.
Some have thought that laser beams carrying messages might have a better chance of being detected. Powerful light beams and radio waves do come from space but, to date, all those detected can usually be accounted for by astronomical events occurring on distant stars and do not have a pattern suggestive of purposeful messages.
A significant improvement in this search could made if we were to place a radio telescope on the far side of the moon where it would be shielded from the cacophony of communication signals coming from Earth.
Now, however, the focus has shifted to a potentially more fruitful search for planets that have the potential of harboring life and are associated with suns not more than a few dozen light years from Earth. That is, planets with rocky surfaces, gaseous atmospheres, and circling at an appropriate distance from their sun. These searches have been made possible by means of the Hubble telescope and significant improvements in the resolution of ground-based telescopes, and a few candidate planets are presently under investigation.
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