how does the free verse structure reflect the central theme of the when I heard the learn'd astronomer poem ? Cite evidence from the poem to support your answer

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.