In 1982, the year E.T. The Extraterrestrial ruled at the box office, another, less heralded movie about aliens came out—John Carpenter's remake of The Thing, starring Kurt Russell. In the first film, a kind-hearted, magical being appears on Earth, works miracles, then ascends into the heavens with a promise to return. Basically, the Christ story.
The second film took a darker, more Darwinian view of extraterrestrial contact. "They" were here to invade their newfound host organisms (us!) with no explanation or apology.
Lacking information about the motives of whatever aliens might exist, both scenarios are equally plausible. And that makes some people nervous about deliberately advertising our presence by beaming messages to other stars. Maybe we shouldn't "shout at the cosmos," for fear of who'd come running.
The folks at the SETI Institute in Mountain View, California, who patiently listen for radio signals that might hint at alien intelligence, have no plans to send messages into space. But they'd like to know what you'd say if they did. So they've invited the public to upload words, pictures, songs, or whatever to a site called "Earth Speaks." The project explores a critical question, according to the researchers: "If we discover intelligent life beyond Earth, should we reply, and if so, what should we say?"
No doubt some people will strain themselves trying to be profound or all-inclusive, as Carl Sagan and colleagues did when they created the Voyager Golden Record, which contains, among many other things, the sound of thunder and whales, and greetings in 55 languages, from Czech to Sotho. (What, no Guaraní? Come on!)
My advice? Don't worry about it. When communicating with imaginary beings, any message is as good as any other. And let's hope that the aliens—who learned eons ago to merge their consciousness with the fabric of space-time and are watching us all the time, anyway—will look on our efforts with amused sympathy.