Photo by Industrial Light & Magic/MarvelBy Benjamin Radford -- Special to Newsarama

Great science fiction isn't just about gooey aliens and gee-whiz technologies like teleporters. Unlike, say, the ever-popular fantasy genre, sci-fi is often grounded in the human condition and based on plausible-if speculative-science. Of course, some science fiction films are more plausible than others: Would the Galactic Empire really have enough manpower to build (and then rebuild) the Death Star in the "Star Wars" films? While legions of sci-fi nerds debate that question, here's are flicks that stand out:

Photo by MGM, Everett Collection1. 2001: A Space Odyssey (1968)

It's no accident that the classic sci-fi film "2001" was rooted in good science, having sprung from the mind of the late, great Arthur C. Clarke. Clarke's background in science informed and inspired the setting in 2001, describing geosynchronous satellites, artificial intelligence, and commercial space travel. Clarke lived long enough to see the satellites he envisioned actually put into orbit, and in the deserts of New Mexico, a "spaceport" is planned that will allow paying passengers to see our pale blue dot from near space.

Photo by Paramount Pictures, Everett Collection2. The Truman Show (1998)

It's hard for many young people to remember, but there was a time before the 24-hour news feed and the reality TV craze. "The Truman Show," starring Jim Carrey as the unwitting star of a voyeuristic television show watched by billions around the planet, foretold the coming of America's weekly entertainment. Not only was close, continuous surveillance plausible, it already exists in current hits like Big Brother and Survivor.

Photo by Sony Pictures3. Gattaca (1997)

In the not-too-distant future world of "Gattaca," children's genes are pre-selected by their upper-class parents for the best traits; those babies whose genes are imperfect are treated as second-class citizens. Today DNA analysis is common, and several companies offer genetic testing for as little as a few hundred dollars. Genetic profiling? Health insurance companies potentially denying claims based on genetic predisposition to a disease? For many, this fear is not science fiction but science fact.

Photo by Zade Rosenthal/Marvel/Paramount Pictures4. Iron Man - 2008

Marvel Comics hero Tony Stark is a genius inventor whose suit of armor-basically a souped-up mechanical exoskeleton run by computers-is probably more scientifically plausible than most superheroes. Though Iron Man's nifty gadgets, including his handy laser repulsors and jet boots, remain science fiction, in many cases the underlying scientific principles are sound. Practical problems, such as the suit's cost and weight, would make a real Iron Man unlikely.

Photo by Universal Pictures, Everett Collection5. Jurassic Park (1993)

Part of what made Michael Crichton an enormously popular writer was his ability to extrapolate current science technology. Science fiction has always been about "What if?", and few modern authors blended science fact with science fiction so successfully. Though scientists are a long way off from cloning dinosaurs-they haven't gone much past Dolly the cloned sheep-the scientific fundamentals are there. By the end of the century, real cloned dinos might just be chasing down tourists!