How to harvest moisture from the atmosphere

Even in the most speculative reaches of science fiction, there is no escaping humanity’s dependence on liquid water. Luke Skywalker, the hero of the original “Star Wars” trilogy, grows up on his uncle’s moisture farm, extracting water from Tatooine’s arid atmosphere. The residents of the desert world Arrakis, accessible to anyone with a copy of Frank Herbert’s novel “Dune” (or with three hours to kill at their nearest cinema), likewise use windtraps to steal precious liquid from the air.