The poem develops around the contrast between two different kinds of "stars" (and, no, not the Hollywood kind). The astronomer's "stars" are abstract ideas that can be reduced to numbers and charts. They reside in a noisy, crowded lecture-room. The real stars, on the other hand, reside in the infinite night sky. They give you that swooning, dizzy feeling in the pit of your stomach. When the speaker goes outside to look at them, he feels a spiritual unity with the night.
- Line 6: The word "gliding" is a hyperbole. It exaggerates the smoothness and ease of the speaker's exit from the lecture-room. Unless this room happens to be located in an ice-skating rink. We doubt it.
- Line 7: The phrase "mystical moist night-air" is an example of alliteration.
- Line 8: The phrase "perfect silence" is a tautology, a kind of logical repetition. "Silence," the absence of sound, is by definition already "perfect." Whitman wants to underscore this point.