Chronos said:
Hmm, Stanislaw Lem is an author of F&SF books. He has not founded a cult, claimed to be a UFO contactee, or otherwise claimed paranormal powers that I know of - aside from annoying some other F&SF authors. Why would he not be ignored by scientists? Most bookstores mark the fiction from fact aisle.
Bookstore marketing aside (so you can take the "F" for "Fantasy" right out of your characterization) good science fiction writers are masters of extrapolation. They take facts and currently-accepted scientific thought and say "what if?". Many of them, besides being able to write compelling stories, are rigorously logical people and have a better foundation in "real science" than you might think. Some have doctorates in the fields about which they write. Here is a presentation on the subject.
http://members.optushome.com.au/guests/PhysicsinSF.html
The author cites Larry Niven's work extensively and offers examples, but you could as easily choose novels by Hal Clement, Isaac Asimov, Theodore Sturgeon, Robert Heinlein, etc. Each of them has written stories predicated on the sciences of physics, chemistry, sociology, mathematics, etc. It would be unwise to dismiss the ideas of these people simply because they write "fiction" for a living. Indeed, some scientists have denigrated Hawking, Sagan, and others for stooping to "popularize" science, as if writing to the comprehension level of an interested lay-person is somehow demeaning. This is a particularly poisonous type of pretentious snobbery that does not serve the sciences well.
Ideas should be weighed on their merits and not solely on the manner of their presentation. There are many, many conflicting ideas written up in scientific journals every day, many of which will be discarded because they are inadequate or just plain wrong. There are many ideas in popular literature that are valuable - you have to take the time and effort to think them through and evaluate them.
"Fiction" does not equal "false", "wrong", etc. Some of the truest words ever spoken were written a few years back by a fellow named Shakespeare.