A Call from Space

In the episode "Call from Space" we investigate the varied methods in use to communicate with life in outer space. Covered are the methods used, the rationale for wanting to communicate, as well as the various levels of communication. What would it be like to talk to another intelligent race from space? Could we converse on their level or would talking to them be like us talking to a garden slug? Have we had messages already and if so, what are we doing about them? What language or code do we use and how do we know if the one we are using is the right one? And, have they been trying to reach us?