Science fiction is hard to define because it has a wide range of subgenres and themes.
That is true, although I think they fit under the general label of science fiction. Do you like science fiction?
Yes, I am really interested in it because I dislike supernatural themes and sci-fi avoids it. 
Yeah that's true. Have you seen 2001 space odyssey?
No, I have not, but I have heard it is very good, maybe I will watch it. One of my favorite TV series is Battlestar Galactica  which was about sci-fi and American military science.
Oh really? I watched i think the first two seaons or so, but got busy doing other stuff. I liked Gaius the most.
Gaius was one of my favorite characters too. I liked the 2004 series, but started with the original tv series in 1978 which led to the 2004 series, a line of book adaptions, original novels, comic books, and more.