For example, Clarke, the author, explicitly tells you that the monoliths are machines left behind by aliens who had passed by our solar system to give our ancestors a little push in the right direction.
Clarke wrote a short story, "The Sentinel," upon which Kubrick based his concept for the motion picture. Kubrick was looking for a theme and a vehicle for a good science fiction movie. He and Clarke met, and Clarke gave him some of his short stories to read. Kubrick selected "The Sentinel." In the short story, an artifact is found on the moon, which seems to be protected by a "force field." When that field is breached, the device sends a powerful signal out into the cosmos. Kubrick, of course, greatly expanded the idea.
The representation of future technology and of space in the movie were outstanding by the standards of 1968.
The movie had only about 70 special effects. I think it was far better in terms of portraying space and space travel, compared, for example, to Star Wars
, which had hundreds of special effects and looked hokey from start to finish.