A poet can provide the initial lift-off, but then the poem enters its own orbit and runs on its own fuel; perhaps the same can be said of any well-crafted powerful writing. No doubt NASA would approve the metaphor.
Poetry is language in orbit. It may start with recollected emotion or immediate anger or rapture, but once that personal boost has helped a poem to lift off, it runs on its own energy circuit.
For a rich selection of other Heaney similes and metaphors, see our celebration of Beowulf, both his version and that of Kevin Crossley-Holland.
Source: Seamus Heaney, Finders Keepers: Selected prose 1971-2001 (London: Faber and Faber, 2003), p. 395
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