Science fiction never imagined Google, but it certainly imagined computers that would advise us what to do. HAL 9000, in “2001: A Space Odyssey,” will forever come to mind, his advice, we assume, eminently reliable — before his malfunction. But HAL was a discrete entity, a genie in a bottle, something we imagined owning or being assigned. Google is a distributed entity, a two-way membrane, a game-changing tool on the order of the equally handy flint hand ax, with which we chop our way through the very densest thickets of information. Google is all of those things, and a very large and powerful corporation to boot.