3 ideas
The Spaniard Domingo Gonsales, marooned on St Helena, trains a flock of wild swan-like birds called gansas to pull a harness. When he flies with them to escape pirates off Tenerife, the birds keep climbing because they migrate to the moon, and they carry him there in about twelve days. On the way he notices that he and the birds stop feeling any weight at a certain height, and he lands among a race of very tall Lunars.
The book treats heaviness as an attraction coming from the Earth, in the manner of Gilbert's magnetism, and not as a built-in tendency of objects to fall toward the center of the universe. Because the attraction grows weaker farther from Earth, a traveler who rises high enough reaches a point where weight nearly disappears and hovering takes no effort. The physics is wrong in its details, but it puts gravity forward as a force between bodies that can be measured by distance.
The Lunars speak in tones and tunes, and a word's meaning depends on pitch as well as sound. Their society has no crime, and they keep it that way by spotting children with bad natures early, from signs such as height, and shipping them to Earth, where they supposedly end up in America. The utopia keeps its peace by sending its unwanted people somewhere else, which shows the hidden cost behind a perfect society.