A helmeted robot lands a flying saucer in a park in Washington, D.C. Dinosaurs freely roam a small isle off of Costa Rica. The Mayan calendar accurately predicts the fiery end of the world. Are the plots of sci-fi movies really that far-fetched?

Of course they are. But NASA, whose space engineers are apparently also sci-fi movie buffs,<a href="http://blog.moviefone.com/2011/01/03/nasa-names-most-realistic-and-unrealistic-sci-fi-films-of-all-ti/?_r=true"> has compiled a list</a> of the most — and least — realistic science fiction films of all time.

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They saved a particular amount of ire for the Roland Emmerich's end-of-days epic <em>2012</em>, which they deemed the least realistic. Rounding out the list are other apocalypse flicks <em>The Core </em>and <em>Armageddon</em>.

The most believable? <em>Gattaca</em>, a 1997 love story set in a dystopian future. Steven Spielberg's <em>Jurassic Park</em> and 1951's classic  alien invasion film <em>The Day the Earth Stood Still </em>also make the grade.