If our kind of intelligence is not unique in the Galaxy, then advanced extraterrestrial civilizations may be currently broadcasting signals (directed or leaked) that we could detect with radio telescopes.

SETI = the Search for Extraterrestrial Intelligence.

Objectives:
 

(1) Where should we point our radio telescopes?

(2) Which frequencies (and frequency range) are the most likely for communications?

(3) What "listening" programs are underway currently?

(4) What kind of message might we expect?