The concept of the horizon is a recurrent one in Their Eyes Were Watching God, and it is a symbol of Janie's journey towards self-fulfillment. Although at the beginning of her journey, Janie is confused about who she is and what she wants, the book describes the changes that she undergoes in order to achieve independence and acquire a different voice.
He shows that just being educated and knowing how things work does not mean that you truly and deeply understand and enjoy nature. Scientific explanations remove the magic that nature can have and explaining a star can never be as great as observing stars during a night. That is what Whitman is trying to say.