The poet can be building images out what he believes to be literal "scientific" truth.
In fact, it is interesting to look at the cosmological references in poetry of different ages.
Just to follow up on this. Let us compare some hymns.
From the bible we have psalm 19. From the 15th century we have "The spacious firmament on high" by Joseph Addison, which paraphrases Psalm 19.
There are some subtle differences between the wording of the Psalmist and Addison's wording.
The psalmist speaking of the wordless "language" of the heavens says "Yet their voice goes out through all the earth and there words
to the end of the world." This is followed by a description of the sun whose "rising is from
the end of the heavens and its circuit
to the end of them."
Clearly the psamist is portraying both an earth and a heaven with definable "ends".
In Addisons' paraphrase the stars "confirm the tidings as they roll/And spread the truth from
pole to pole." And he continues "What though in solemn silence all/move round the
dark terrestrial ball..."
Two things stand out. Addison is still speaking of the heavens and heavenly bodies moving around the earth. But instead of the "end" of the earth, he speaks of its poles and calls it a "terrestrial ball". So he has changed from imagery of a flat-earth with vaulted heaven above to a geocentric earth with the heavens rolling around it.
I couldn't find a modern paraphrase of Psalm 19, but look at these lines from some contemporary hymns.
From "God created heaven and earth"
"God's great power made dark and light/earth
revolving day and night"
From "Creating God, your fingers trace"
"Creating God, your fingers trace/the bold designs
of farthest space"
From "Before the Earth"
"Before the Earth had yet begun/its
journey round the burning sun..."
Here we have the poetry of modern cosmology.
(All these hymns were found in
Voices United, the current hymnbook of the United Church of Canada)
Conclusion: the poetic/literal dichotomy is too simplistic. It does not always apply. Ideas we understand to be "literal fact" often find their way into poetry. So one can not assume from a poetic setting that the author's phrasing is not also to be understood literally -- at least as far as the author is concerned. He can well be referring to what he thinks of as "fact" according to the knowledge of his time.