In Steven Spielberg's popular 1982 movie, "ET, the Extra-Terrestrial," a friendly alien is stranded on Earth, three million light years from home, and builds a communicator to arrange for his rescue.
Now anyone with a PC can try to receive calls from ETs, or at least listen to what they may be saying.
SETI@home is a scientific experiment that uses Internet-connected computers in the Search for Extraterrestrial Intelligence ("SETI"). People participate with a free program that analyzes data from the Arecibo radio telescope in Puerto Rico to find signals that might indicate intelligent life.
According to the Wall Street Journal, computer scientist David P. Anderson realized that with the Internet connecting millions of often-idle computers, the time was right for "distributed computing." This takes one big computing project, and breaks it into little pieces, to be farmed out to many machines.
Anderson chose SETI as a problem for the machines to tackle, and participants earn points for computer time donated. Points are good only for bragging, but are an important motivator because finding an ET is unlikely.
If you'd like to hunt for aliens, or just play for points, go to