How we cite our quotes: (Chapter.Paragraph)
Quote #1
It was barely audible, yet it stopped them dead, so that they stood paralyzed on the trail with their jaws hanging slackly. (2.12)
It's not exactly clear if the man-apes are filled with awe, if they're semi-hypnotized, or just confused. The slack-jawed stare comes across as something of a parody of watching television—especially since the man-apes eventually watch images in the slab. Awe is kind of watching a screen—it's like the man-apes in the novel are watching the man-apes in the film of 2001 (and are amazed).
Quote #2
Someone had once said you could be terrified in space, but you could not be worried there. It was perfectly true. (8.31)
Heywood Floyd thinks that space is a place for big emotions. We haven't been to space, so we can't say if that's accurate—but it's certainly true that 2001 prefers big, huge, emotions to smaller more contemplative ones.
Quote #3
So perhaps these visitors had come from the stars—yet that was even more incredible…Speculation was a waste of time: he must wait until there was more evidence. (12.26)
Floyd thinks about the vastness of space and time…and then chastises himself and says he needs evidence. This is a nice thumbnail illustration of how the novel works. It gives you giant, speculative, preposterousness to swallow (evolving man-apes! Energy aliens!) and then follows that up with serious, slow-moving descriptions of technical details. The details and the plea for evidence are supposed to make the awesome ridiculousness more real—even though it might make us yawn sometimes.