Final answer:
Whitman's poem contrasts scientific language with natural imagery to express the limitations of pure rationality and the need for a deeper connection to the universe.
Step-by-step explanation:
In Whitman's poem "(When I heard the Learn'd Astronomer)", lines 1-4 and lines 5-8 contrast in their language describing the domain of science. In lines 1-4, Whitman uses scientific and technical terms such as "astronomer", "lecture", and "charts and diagrams" to depict a formal and academic approach to science. However, in lines 5-8, Whitman shifts to natural and sensory imagery, describing the speaker's longing for the "mystical" and "starlit" beauty of the night sky.
This contrast between scientific language and natural imagery expresses a theme of the poem which highlights the limitations of a purely analytical and rational understanding of the world. Whitman suggests that there is a deeper, emotional and spiritual connection to the universe that cannot be captured by scientific knowledge alone.