Sometimes writers write about a world that does not yet exist. We do it for a hundred reasons. (Because it's good to look forward, not back. Because we need to illuminate a path we hope or we fear humanity will take. Because the world of the future seems more enticing or more interesting than the world of today. Because we need to warn you. To encourage. To examine. To imagine.) The reasons for writing about the day after tomorrow, and all the tomorrows that follow it, are as many and as varied as the people writing.