I think that the answer to this is going to be a personal one. From the tone of the question, it seems like this has been discussed in your classroom setting and you might have to reference this discourse in any answer. Looking at it from Whitman's point of view, I think that he would make the argument that there is a difference between learning and understanding. Whitman's fundamental argument in the poem is that the process of understanding and discovery is not limited to the formal setting. When Whitman understands the nature of astronomy, and in a larger sense the sense of wonderment about the world, it happens outside of the formal lecture hall. I think that the concept of a journey involves learning and understanding in both structural and informal sensibilities and to embrace both is part of the advanced process of graduate school and beyond. I think that this is where Whitman's poem might fit into your scope and sequence of study. Whitman listens to the learn'd astronomer and decides that his journey involves integrating the external setting into his own frame of reference. Perhaps, there is a lesson here for the reader in that the true aspect of understanding and wisdom comes when one integrates as many frames of reference as possible into their own learning experiences. This might be where the journey lies.