Carl Sagan, in my opinion, was one of the best science communicators of all time. In this video clip, he is on The Tonight Show in 1978 when Johnny Carson was the moderator.

In the section I've marked below, Carson asks him about the search for extraterrestrial intelligence, an endeavour that Sagan has been involved with deeply.

I recommend watching the whole clip if you have the time. On a lighter note, I found it hilarious that after the show ends they all stand around and talk, and Johnny Carson lights a cigarette on stage.