What role does "Where is Tianhe" at the beginning of the second paragraph of Silent Night play in the whole poem?

"Where is Tianhe?" This problem broadens and promotes the realm of the whole poem and brings the reader's vision and mind to the vast universe. The author seems to want to lead the reader's thoughts to "concentrating on the eight poles" and "roaming in Wan Ren", and seems to want the reader to see the infinite depths of the starry night through the boundless darkness.