"Today I swam through MOMA. Leon says it was a waste, encasing the art, then flooding the museum-frivolous and elitist. I say it was a gesture of optimism, a triumph of technology and political will." Want to thrill to the possibilities of a hopeful future? We asked a bunch of sci-fi writers to spin tales of a better future, imagining ways in which the world might become a better place. From a swim through an underwater...