There are a lot of hurdles out there when it comes to making a video that will stand out among the zillions that are already available across the Internet. You need a great idea. You need to execute it well. And if you can leave the viewer wondering just how the hell you pulled it off, so much the better. The above video, a fan merging of this year’s Europa Report with imagery and footage from 2001: A Space Odyssey in order to create a faux trailer for Arthur C. Clarke’s unfilmed 2061 sequel did precisely that. It left me asking, “Is that really Keir Dullea? How the hell did they get Keir Dullea?”

Geek royalty Joss Whedon stirred the pot quite a bit this week by criticizing the ending of arguably the best Star Wars movie of all time, The Empire Strikes Back. His problem with it was that he didn’t like the cliffhanger aspect that left many things unresolved. Whedon said, “I go to movies expecting to have a whole experience. If I want a movie that doesn’t end I’ll go to a French movie. That’s a betrayal of trust to me. A movie has to be complete within itself, it can’t just build off the first one or play variations.”

Aside from that criticism being kind of odd coming from a master of TV cliffhangers, Whedon’s argument has stirred up many fans who love Empire precisely because of its dark, unresolved ending. For the second film of a planned trilogy, it makes sense to end on an ominous down note, thus setting the stakes for the third film to follow. But Whedon’s comments got us thinking: what makes for a truly great ending? We’ll try to answer that question below, with our picks for the Ten Best Science Fiction Movie Endings of All Time.