Instead, he uses the concept of time as a metaphor for limitation and artificiality:
* The astronomer's lecture: The lecture is presented as a rigid, intellectual approach to understanding the universe, confined to facts and figures. It's a very structured, "time-bound" way of perceiving the cosmos.
* The "numb" feeling: The speaker experiences a sense of numbness from the lecture, suggesting that the astronomer's approach to the universe feels *unnatural* and *devoid of real connection*. This numbness can be seen as a metaphor for feeling trapped in a rigid, time-bound perception.
* The "mystical" feeling: When the speaker goes outside and looks at the stars, he experiences a profound, emotional connection with the universe. This feeling is free from the constraints of time and intellect.
Essentially, the astronomer's lecture is a metaphor for the limitations of intellectual understanding, while the speaker's experience under the stars represents a more direct and timeless connection to the cosmos.
So, while Whitman doesn't use the word "time" directly as a metaphor, he does use the *concept* of time to contrast the limiting, artificial view of the universe with a more profound, mystical experience.