The speaker of this poem describes listening to a learned astronomer lecture. He sees proofs and figures in columns before him, as well as charts and diagrams that he is supposed to analyze mathematically. At the end of the the lecture, everyone else applauds the astronomer. Meanwhile, the speaker sits in the lecture room, feeling sick and tired. When he wanders away, he looks up into the sky and finally recognizes the magic.
Whitman wrote this poem in free verse, like most of his other poems. It consists of one single stanza with eight lines. The lines vary in length and have different stressed and unstressed syllables, which gives the poem an anecdotal feel. The first four lines of the poem all begin with "When" as the speaker recalls sitting and listening to the astronomer lecture. These first four lines function as a setup; and the final four lines describe the speaker's reaction to the experience well as the lesson from the poem.
In this poem, Whitman uses the example of the astronomer to show the difference between academic learning and experiential learning. The speaker finds the astronomer's lectures stars and mathematical formulas to be boring. He does not feel any sort of connection to the subject matter until he goes outside and sees the stars for himself. Looking up at the night sky is not an experience that one can experience in a classroom, no matter how "learn'd" the teacher might be Whitman felt very strongly that experiencing life's marvels was the only real way to learn.
In this poem, Whitman draws out the stark contrast between the speaker and the educated astronomer. Whitman writes the speaker's voice to emphasize the fact that he is not an academic. For example, he shortens "learned" to "learn'd" when describing the sophisticated professor. The speaker quickly grows bored while listening to the astronomer talk about theories and mathematical equations. The astronomer, however, represents a highly educated and refined class that has a more structured approach to learning. The speaker and the astronomer serve as foils to each other - characters who have opposite beliefs. The writer uses this disparity to highlight each individual's distinct characteristics.
Even though this poem is short, Whitman establishes a clear and vivid setting. First, he describes the classroom and lecture hall, where the astronomer is using charts to illustrate his theories and the audience's polite applause. Whitman's skill in creating evocative imagery is most powerful in the second half of the poem. The speaker is clearly inspired as he "glides" out into the "mystical moist night air" and admires the dazzling stars above him. Whitman paints pictures with these words.
Ultimately, this poem serves to highlight the difference between wisdom and knowledge. In the context of this poem, wisdom is the process of learning through experience and exploration (the speaker appreciates the wonders of the night sky only when he sees it for himself). Knowledge, on the other hand, comes from research, reading, and established theories. Academic knowledge is a more tangible form of intelligence; while wisdom, on the other hand, is intuitive. The astronomer attempts to relay his academic knowledge in his lecture, but the speaker does not connect to the subject matter from such a distance.