Hard science fiction is a category of science fiction characterized by an emphasis on scientific or technical detail, or on scientific accuracy, or on both.[1] The term was first used in print in 1957 by P. Schuyler Miller, book reviewer for Astounding Science Fiction.[2] The complementary term, soft science fiction (a back formation that first appeared in the late 1970s[3]) by contrast refers to science fiction in which science is not featured, or the science is incorrect or made-up. The term sometimes also contrasts the “hardness” of the sciences used in the story: the “hard” sciences are quantitative or material-based disciplines, such as physics, chemistry, and astronomy; while the more “soft” sciences are social sciences, such as sociology, anthropology, or psychology. (Stories featuring engineering tend to be categorized as hard SF, although technically engineering is not a science.). Neither term is part of a rigorous taxonomy — instead they are rule-of-thumb ways of characterizing stories that reviewers and commentators have found useful. The categorization “hard SF” represents a position on a scale from “softer” to “harder”, not a binary classification.