Why do you think Swift put Laputa in the sky?

This has to do with social hierarchy. On Laputa, the floating island, Swift creates a way of physically stratifying a society. Those who work with their hands for a living-and the ridiculous professors-live on Balnibarbi. The upper class, including the royal family and the more able intellectuals, live on the floating island of Laputa. In this way Swift makes the separation between the two types of people visually obvious, with the better above the lesser.