What Are the Different Types of Sci-Fi?

Science fiction is a wide-ranging genre, with a lot of blurred edges and overlaps between groupings. But a number of types can be broadly identified. Here are some different types of sci-fi along with examples of famous films and authors for each category.

"Hard" science fiction extrapolates directly from today's modern science and emphasizes scientific detail and accuracy. Hard science fiction writers are often scientists themselves (Isaac Asimov, Gregory Benford).

"Soft" science fiction, in contrast, emphasizes social issues and issues of personal identity. Examples could include Star Trek in television; among novelists, Ursula K. Le Guin.

Space opera involves epic scale and conflict between idealized heroes (often involving a wizened mentor and an untried youth) pitted against unredeemable villains. In film, the original Star Wars is a classic example; a well-known novelist of this type is E.E. "Doc" Smith.

Alternate history is a branch of science fiction that extrapolates from a point in the past, rather than from today, and takes a different path from the one we took. Questions involve what the world might be like if the Axis powers had won World War II, or if Lincoln had not been shot. Master practitioners include Philip K. Dick and Harry Turtledove.

Dystopia starts by rejecting the idea that "scientific advance" with automatically bring about a superior civilization; the dreamed-up reality might, in fact, be as corrupt and unjust as the darker days of our own world. After World War II dystopian fiction often assumed a nuclear apocalypse, with survivors fighting to retain their humanity (Mad Max, A Boy and His Dog); but such a cataclysm is not necessary (Blade Runner).