What is the meaning behind "When I Heard the Learn'd Astronomer" by Walt Whitman?

The poem falls into two sections, even though they are not
indicated on the page. In the first, the narrator is inside the lecture room, listening
to a well educated astronomer, a "learned" man, explain the universe in terms of
mathematics, with his charts and diagrams to be added, divided, and measured. In the
second part of the poem, the narrator goes outside alone. The poem is developed in the
contrast between these two settings.

Inside the lecture
room, there is "much applause" by the audience, but the narrator begins to feel "tired
and sick." When he removes himself from the room and from the astronomer's lecture,
however, the change of setting suggests a change in his
feelings:

. .
. I wandered off by myself,

In the mystical moist night
air, and from time to time,

Looked up in perfect silence at
the stars.

The narrator has
placed himself in a romantic natural setting that is beautiful and appealing with the
reference to the "mystical moist night air." In this setting, he does not see the stars
as objects on charts and diagrams. He views them "in perfect silence" in the heavens,
their natural setting. The silence itself is an natural element of beauty that contrasts
the noisy lecture room.

The poem can be interpreted as
expressing a romantic view. The beauty, mystery, and grandeur of the universe cannot be
grasped intellectually, only spiritually.