Hard science fiction, or hard SF, is a subgenre of science fiction characterized by an interest in scientific detail or accuracy. Many hard SF stories focus on the natural sciences and technological developments, although many others leave the technology in the background. Some authors scrupulously eschew such implausibilities as faster-than-light travel, while others accept such plot devices but nonetheless show a concern with a realistic depiction of the worlds that such a technology might make accessible.
Character development is sometimes secondary to explorations of astronomical or physical phenomena, but other times authors make the human condition forefront in the story. However a common theme of hard SF has the resolution of the plot often hinging upon a technological point. Writers attempt to have their stories consistent with known science at the time of publication. Interestingly, some hard science fiction stories are set in an alternate universe where different physical laws apply; however, in such cases the author makes use of current physics to design a universe that is at least potentially realistic.
Hard science fiction is largely a literary genre, as the complexities of physics rarely translate well to the screen. One of the notable exceptions is 2001: A Space Odyssey, however the movie still leaves out much of the examination of the physics, computer science, and other scientific analyses present in the novel version.
Well known authors often said to be practitioners of hard SF, include
Poul Anderson
Isaac Asimov
Iain M. Banks
John Barnes
Stephen Baxter
Greg Bear
Gregory Benford
David Brin
Arthur C. Clarke
Hal Clement
Greg Egan
Michael Flynn
Robert Forward
Robert Heinlein
James P. Hogan
Nancy Kress
Larry Niven
Paul Preuss
Alastair Reynolds
Kim Stanley Robinson
Joan Slonczewski
Allen Steele
Jules Verne
Masamune Shirow (manga artist). His works often examine the impact of advanced future technology in society, particularly cybernetics and information networks. He is known for going into great technical and scientific detail, to the point of using numerous captions and footnotes to explain technical aspects to the reader or even suggest possible theories/implementations for fictional technology. This extends to his drawings, where he will sometimes make a note to explain the function of a stylistic feature of a weapon or robot. He has also created the Neurohard project, a world in the hard science fiction style to be used by him and other artists. Shirow's work is unique in that it develops in equally great depth the social/cultural aspects in a 'hard' style, again providing notes on ideas, philosophy, etc. and using a somewhat techical approach in discussing ethics and social issues. The Ghost in the Shell manga (but not the anime) is a good example of his serious work. Appleseed is another story featuring heavy use of advanced technology in which, ironically, the critical moment is resolved by clever use of an actual apple seed in the midst of hardcore robotic chaos.
See the article on Hal Clement for a description of how one hard science fiction author viewed his craft.
One science-fiction television show which has consciously attempted to portray physics correctly is J. Michael Straczynski's Babylon 5, albeit inconsistently especially in later seasons of its half-decade run. The sequel series, Crusade, went so far as to formally enter into a working partnership with NASA's Jet Propulsion Laboratory to ensure scientific accuracy. Certain dramatic elements such as sounds in space, visible lasers in a vacuum, etc., are probably to be expected or even demanded by the casual viewer not deeply familiar with the real science involved, and any television or film SF producer must tread a gray line between pleasing the lowest and highest common denominators in his audience. However, even in these cases, the producers came up with an explanations which attempted to produce a consistent physics (i.e. the sounds in space were background music and the lasers were not lasers but plasma bolts).
An example of a web-based hard science fiction project (where many people contribute different pieces of what becomes a coherent story) is Orion's Arm.
A fan organization that has grown up around Hard Science Fiction is General Technics, populated by scientists, technical folks, and others with a specific interest in this area. General Technics' name is taken from the organization that created a global-scale computer in John Brunner's novel, Stand on Zanzibar. General Technics, though concentrated in the American Midwest, has a global membership.