What according to the speaker is the best way to understand nature in "When I Heard the Learn'd Astronomer"?

The subject of understanding nature plays a key role in Walt Whitman’s poem “When I Heard the Learn’d Astronomer.” The speaker sits obediently and apparently appreciates the scientific facts that the lecturer is presenting. The mathematical information and its mode of presentation in charts is convincing, but he starts having trouble paying full attention. In fact, he finds that the lecture makes him feel “troubled and sick.” This motivates him to leave the lecture room and wander off alone. The speaker’s words and the poem’s tone shift markedly at this point. It is then we see how the speaker feels about understanding nature, in direct contact and through spiritually minded contemplation. Rather than listen to someone else speak in a crowded room, the speaker needs to be alone in the quiet outdoors.

I wander’d off by myself,
In the mystical moist night-air, and from time to time,
Look’d up in perfect silence at the stars.