Science fiction is the search for definition of man and his status in the universe which will stand in our advanced but confused state of knowledge (science), and is characteristically cast in the Gothic or post-Gothic mould.
Trillion Year Spree: the History of Science Fiction (London, 1986)
The future depicted in a good SF story ought to be in fact possible, or at least plausible. That means that the writer should be able to convince the reader (and himself) that the wonders he is describing really can come true...and that gets tricky when you take a good, hard look at the world around you.
The Shape of Things to Come and Why It Is Bad, SFC, December 1991
Definitions of Science Fiction
Sci-fi authors define sci-fi June 5, 2009 Science Fiction
I'll quote myself here: “Though important events, situations and characters may in themselves be fantastical, science fiction assumes an explanation based on a logical universe. This is opposed to fantasy works, and some horror, in which such ideas are described through magic or the whims of the gods.”
A unit on genetics had Sephali Ray’s students jazzed. A seventh-grade science teacher at the New York City Lab School, a public middle- and high-school, Ray didn't stop with the scientific facts. “It’s absurd for students to talk about how DNA works without trying to understand its implications for society,” says Ray.
Good science fiction is story, science, and speculation all wrapped up in a package custom-made for improving literacy and critical-thinking skills-it does not get more convenient.
Students prepare by analyzing a work of science fiction and examining the underlying science idea in terms of the attitude and knowledge conveyed through the story about the author, following this with research on the author.
June 5, 2009 Science Fiction Every Sunday our characters talk about a book they've read in full-page full-color comic strips. Our book clubs are posted in libraries, book stores, and in homes, and you have our permission to do so too ( write us if you're interested in other uses).
SF Site is composed of many pieces. Twice a month since July 1997, we have posted a mixture of book reviews, opinion pieces, author interviews, fiction excerpts, author and publisher reading lists and a variety of other features. At the same time, we've maintained a comprehensive list of links to author and fan tribute sites, SF conventions, SF TV and movies, magazines and e-zines, writer resources, publishers and small press sites and many other SF resources.
The Hugo Award was named in honor of Hugo Gernsback, "The Father of Magazine Science Fiction," as he was described in a special award given to him in 1960. The Hugo Award, also known as the Science Fiction Achievement Award, is given annually by the World Science Fiction Society (WSFS) . The distinguishing characteristics of the Hugo Award are that it is sponsored by WSFS, administered by the committee of the World Science Fiction Convention (Worldcon) held that year, and determined by nominations from and a popular vote of the membership of WSFS.
The SS Cygni probe sent back hours of video, captured by the Biolathe AI, but only a few minutes mattered--the four minutes that showed a creature made of fire, living , moving, dancing in the plasma fire of the double star's accretion disk. A dragon made of star stuff, so alien that only a human expedition to observe and perhaps capture it, could truly understand it.
Fantasy is closely associated with science fiction, and many writers, including Robert A. Heinlein , Poul Anderson , Larry Niven , C. J. Cherryh , Jack Vance , and Lois McMaster Bujold have worked in both genres, while writers such as Anne McCaffrey and Marion Zimmer Bradley have written works that appear to blur the boundary between the two related genres.  The authors’ professional organization is called the Science Fiction and Fantasy Writers of America (SFWA). 
Science fiction from Wikipedia, the free encyclopedia
If anyone were to force me to make a thumbnail description of the differences between SF and fantasy, I think I would say that SF looks towards an imaginary future, while fantasy, by and large, looks towards an imaginary past. Both can be entertaining. Both can possibly be, perhaps sometimes actually are, even inspiring. But as we can't change the past, and can't avoid changing the future, only one of them can be real.
Star Wars could be considered both science fantasy and standard science fiction
it can be argued that science fiction is simply a modern form of fantasy. According to this view, the elements that would previously have been presented as fantasy (e.g., magic , shapeshifting , divination , mind-reading, fabulous beasts, and so on) are rationalized or supported through scientific or quasiscientific explanations such as marvelous devices, mutation, psychic abilities, aliens, etc. An example is The Force and the conflict between the Sith and Jedi in Star Wars.