Science fiction, much like any other genre of literature or art, contains certain sub-genres. Fantasy science fiction includes universal functions outside of reality or potential reality, such as magic-users or monsters, which can't be explained by science. Utopian science fiction explores the functioning of an imaginary world, where everything appears to be perfect or imperfect. These works often review the shortcomings of Utopian societies as a reflection of contemporary society. Exotic travel narratives share a travel adventure under the pretense of truth. Apocalyptic stories show the final unraveling of the world, usually because of some movement toward an amoral ideal.
Although some science fiction attempts to maintain scientific integrity, the majority of science fiction uses unproven, impossible or unthought-of scientific processes within its work. For example, the machine in H.G. Wells' "The Time Machine" breaks causality, meaning that according to modern scientific theories it could not function. Science fiction may contain fact within it, but as a creative field, authors and artists are not held by the restrictions of reality.
Scientists spend years studying minutiae, in the attempt to discover any one thing that could move a field or science forward in its understanding of the universe. Unfortunately, science fiction writers do not have the luxury of spending time on minutiae; if they did, writers could not produce works at any substantial rate. Instead, science fiction creators must make leaps of scientific faith, creating machines, methods and monsters that could possibly exist given basic information.
The real difference between science fiction and science fact can be summed up in this way: science fact is the existing collection of scientific evidence; science fiction is an author or artist's attempt to use science as the foundation for an artistic piece. The latter uses the former to create an artistic statement that entertains and inspires the reader through imagination. In science fiction, the goal is art, while in science fact, the goal is knowledge.