Usage of the word "spheres" in "A Noiseless Patient Spider"

Question

I do have an idea of what Whitman is telling in the last stanza and the whole poem but what confuses me is the usage of the word "spheres" in the second stanza of "A Noiseless Patient Spider". A thorough explanation of the usage and the meaning of the word is much appreciated.

I have given the poem below:-

A Noiseless Patient Spider

BY WALT WHITMAN

A noiseless patient spider,
I mark’d where on a little promontory it stood isolated,
Mark’d how to explore the vacant vast surrounding,
It launch’d forth filament, filament, filament, out of itself,
Ever unreeling them, ever tirelessly speeding them.

And you O my soul where you stand,
Surrounded, detached, in measureless oceans of space,
Ceaselessly musing, venturing, throwing, seeking the spheres to connect them,
Till the bridge you will need be form’d, till the ductile anchor hold,
Till the gossamer thread you fling catch somewhere, O my soul.

Answer 1

From context, I'd take this to be the celestial spheres, an old cosmological idea that originated in antiquity. Briefly, each planet, including the sun and moon, where thought to inhabit their own sphere, while all stars were fixed in the outmost sphere (and God's heaven being placed beyond the stars). The spheres were invisible, but at least in the some schools of thought, they were thought to make a sort of music. They were a commonplace in medieval cosmological thought, and are a part of the cosmological vision in Dante's Paradisio. They are thus a concept both related to a Christian view of the Heavens, and the actual celestial objects, which fits nicely with the rest of Whitman's poem.

Both the spheres themselves, and the "music of the spheres" survived in mainly poetical contexts after they had been dismissed by science, and you can still find occasional references to them.