Why is the moon not saddened by this saddened event in the poem edge by Sylvia Plath?

In the poem "Edge" by Sylvia Plath, the moon is depicted as an impartial observer that remains indifferent to the human emotions and struggles around it. The moon's detachment from the human experiences of sadness emphasizes a sense of isolation and alienation in the poem. This portrayal reinforces the poem's themes of despair and existential angst.