A small, ordinary moment opens the poem: the sun breaks through while it's still raining. Normally that would mean a rainbow, but the sun is too high in the sky for one to appear. The speaker doesn't leave it there. Instead, they ask us to imagine looking down from above, the way a bird would, or perhaps something even higher. From that view, the rainbow could lie against the ground.
Then the poem zooms out much further. Beside that picture it places the "radiant field lines" of the Earth as a magnet, as if the planet itself were glowing with invisible energy. The title, "Earth Day," suggests why this matters: the speaker is looking at the planet with fresh wonder.
The mood is quiet, curious and gently awed. Nothing dramatic happens, yet a passing shower becomes a way of seeing the whole Earth. The trailing ellipsis at the end leaves that sense of wonder open.