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.