The title sounds like a physics problem, and the first stanza treats it like one. The speaker stands on a hilltop, level with the hemlock tops, and builds a bird piece by piece: arms raised in "the perfect dihedral," shoulders "rounded exactly right," hands curved "into the primaries of a rough-legged hawk." The vocabulary belongs to a birdwatcher or an engineer. A dihedral is the upward angle of a wing, and the primaries are the long flight feathers at its tip. The speaker is not playing at flying but attempting it with technical correctness, and the poem lets her come astonishingly close.
Then the body takes over from the mind. There is "a vibration, a trembling up my arms," and fingers that "pinnate," a descriptive adjective pressed into service as a verb, as if the hands were changing faster than the language could keep up. The feathers are "prickling through my skin," a sensation that is slightly painful and entirely physical. Nothing here is vague or dreamy. The precision that makes the attempt believable is also what makes the failure sting.
The poem has no rhyme and no fixed meter, and its rhythm follows the speaker's thinking. The early lines are long and accumulating, like a checklist being ticked off. Then the syntax hedges: "I could have done it," "Perhaps I could have risen." The dash after "that stunning sky–" holds the sentence in the air, and "and yet" drops it. What stops her is named hesitantly: "some solid thing, / some reservation of gravity." The repeated "some" suggests she is groping for a name she cannot find. "Reservation" is the stranger and better word. It means a doubt or a holding-back, like a seat set aside, and "gravity" carries two meanings as well, the force that pins her down and the seriousness of adulthood. Read that way, the thing that grounds her is as much a habit of mind as a law of physics. The stanza ends on the flat, heavy word "ground."
The second stanza changes tense. Everything so far has been conditional ("could have," "perhaps"), but now the verbs are present and certain: children "know," "leap," "flutter," "carry." It is also much shorter, as though it needs little explaining. Where the speaker had a hilltop and a hawk's anatomy, the children have "homemade wings" and "kitchen chairs." Their launch pad is a piece of furniture and their equipment is cobbled together, yet they succeed where exactness failed. Their flight even produces souvenirs, "the smiling sun, yellow moon, / the sharp pointed stars." These are the sun and stars as a child draws them, with a face on the sun and points on the stars. Compare the adult's sky, "the sun scattering the light into improbable blue," a phrase that is half scientific explanation and half wonder. The children's sky is something you can bring home.
The sound of the poem links the two worlds. The "s" runs through the sky imagery ("sun scattering," "stunning sky," "solid," "some") and returns in the closing line ("smiling sun," "sharp," "stars"). The adult's sky and the children's sky are made of the same sounds, only the children can reach theirs. The poem also ends upward, on "stars," where the first stanza ended on "ground."
The poem is significant because it answers its title without stating the answer. The speaker has the knowledge, the posture and even the physical sensations, so skill is not what it takes to fly. What the children have is the absence of reservation, a belief that does not stop to check itself. The poem does not scold the adult, and its "perhaps" stays honest about what might have happened. But it quietly suggests that imagination is a kind of knowledge ("Small children know"), and that growing up may mean trading the ability to leap for the ability to name every feather.