Movies are the ultimate dream factory, allowing artists to come up with endlessly fascinating "what if?" scenarios for the rest of humanity to ponder from the safety of a comfy cinema chair.
Perhaps more so than any other genre, sci-fi is all about escapism, about looking to the stars and wondering what's out there, and what might be in store for humanity's future.
And as such, it's not terribly surprising that the genre loves to ask audiences the big questions, and saddle them with epically anxious moral dilemmas in the process.
These 10 sci-fi movies, whether indelible classics or cult curios, all gave viewers plenty of food-for-thought with their tantalising, agonising ethical questions. In the protagonist's shoes, could you make the same tough decision or not? Or better still, would you?
From making bold choices for the greater good to wilfully living a life of ignorance to shamelessly embracing your inner-creep, none of these questions have easy answers, no matter what the movie's characters ultimately decided...