Night falls in this poem one step at a time. Every line begins with "as," so the poem feels like a single long breath, or a slow countdown, with each image adding to the one before. The light drains away: darkness spreads, the moon appears, the sun's fire dies down, and the stars take over. Then the focus shifts to living things. Predators wake up while prey drifts off to sleep, which hints at a quiet sense of danger hiding inside the calm.
The speaker is only a watcher, "gazing outside," and that detail makes the poem feel personal and still. The final line is the most striking. The "fragile Earth disappears," and the word "fragile" suggests the speaker feels how delicate the world is. The mood is peaceful but a little uneasy, as if falling asleep means letting go of everything. Because the sentence never finishes, the poem seems to fade out the way a mind does just before sleep.