Are we trying to contact extraterrestrial civilizations?
Yes. Using a large radio telescope in Ukraine, Canadian astronomers Yvan Dutil and Stephane Dumas plan to beam a coded greeting toward four stars that are similar to the Sun. The message, about 50 kilobytes in size, will be transmitted three times over a three-hour period on May 24, 1999.
The message will use basic mathematics and physics to establish a common language with any civilization that intercepts the transmission. It will include brief descriptions of basic astronomy, geography, biology, and other scientific concepts.
Astronomers say that any civilization within 100 light-years of Earth with a radio receiver covering one square kilometer (0.4 square mile) should be able to read the message. Civilizations out to 10,000 light-years should be able to discover the intelligent nature of the message, but the signal wouldn't be strong enough for them to decipher it.
The target stars are all roughly 50-70 light-years from Earth, and lie in or near the Summer Triangle, a large region of the sky bounded by the bright stars Vega, Deneb, and Altair. As the signal races through the Galaxy, however, it will spread out, so it will reach all of the stars in that direction. Sun-like stars were chosen as targets because they are considered the most likely homes for life.
The message concludes with an invitation for the recipients to respond with information about themselves. But a reply from the target stars wouldn't arrive for more than a century (50-70 years for the message to reach them, and 50-70 years more for a response to reach Earth).
In the 1970s, NASA's Pioneer and Voyager missions left Earth carrying information about the civilization that sent them. A quarter-century later, however, the four probes are barely to the edge of the solar system, so they're not likely to encounter an alien civilization any time soon. They serve more as interstellar time capsules documenting humanity's first efforts to explore beyond its home planet.
Our radio, television, and other communication signals also are a sign of our presence, having been beamed into space at the speed of light for most of the twentieth century. So far, though, none of our broadcasting signals have been explicitly designed to announce our presence.
We're also listening for other civilizations. Since the 1960s, teams of observers have tuned radio telescopes to microwave and radio wavelengths in hopes of detecting a signal from an alien civilization. Collectively known as the Search for Extraterrestrial Intelligence (SETI), the searches have uncovered no ETs yet, but recent discoveries of planets around other stars and the possibilities of life having formed on Mars or the moons of Jupiter and Saturn have provided encouraging evidence to the prospects of a universe teeming with life. We may be lucky enough to detect and respond to the signals of an extraterrestrial civilization someday, but the vast distances of space make having a conversation impossible.
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