Many years (20+?) ago in Analog SF magazine I read a short story where a culture discovered interstellar travel shortly after the start of their iron age. They could construct air-tight ships and travel essentially as far as their oxygen supply lasted. Before they met us, the most technologically advanced culture they came across had discovered balloon flight. Needless to say they thought our jets were merely improved balloons.
1 Answer
Pretty sure that's The Road Not Taken by Harry Turtledove.
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1Never read that, but I have read the sequel Herbig-Haro as anthologized in Republic and Empire or something like that. A good story. Commented Nov 23, 2011 at 2:25