In James Cameron's Avatar, we're introduced to an alien race that we immediately take to: the almost-human Na'vi. But sympathizing with slightly-different people is easy. Here are few examples of sci-fi giving us truly "alien" aliens.
It's a common pet peeve among sci-fi fans: why do aliens always seem so undeniably human? Shouldn't a strange new consciousness from a far-away world seem more alien? And not just in looks - we've written about human-looking aliens before - but in motivations and behavior as well.
For instance, there's no reason to assume that an alien species would look like a human with a weird forehead. But there's also no reason to assume that aliens would have a human-like conception of property or of societal connection or even of self.
While what seems to be a majority of science fiction relies very heavily on making their aliens as behaviorally human as possible, there are a few aliens in the cannon that challenge our perceptions of aliens and what a true other might actually be like. Here are some examples of truly alien aliens (each include some spoilers).
In one of the only common features between both film versions of Solaris and the original novel, one of the main objects of the story is to present a truly "other" alien. In Solaris, human scientists have stumbled upon a planet that seems to be covered in a living ocean. So, they attempt to communicate with it.
And the "ocean" communicates back in the only way it knows how: by conjuring up living manifestations of the deeply hidden tragedies and shames of the scientific crew. The films hint at what is the novel's focus: the sentient oceans are so alien from humanity that its attempts to communicate look more like torture. All three versions leave the audience with no clue as to what the sentient oceans actually want. And that's a lot more realistic than clear communication between two wildly different species.
The motivations of the 456 in Torchwood's Children of Earth miniseries are a lot clearer: they just want Earth's children for what appears to be a very gruesome narcotic-like use. But what makes the 456 so great an example of an alien species is that this use is never clear, and humanity is in no position to investigate the aliens.
It's another common misstep in alien stories: unlocking the biological or scientific secrets of the alien proves the necessary step to defeating them. In this story, the alien remains callously and disturbingly other throughout. It's like "To Serve Man" with a decidedly Lovecraftian twist.
The creature from Midnight
In the Dr. Who episode "Midnight," we see that in science fiction stories, you don't always need a malicious alien to find a villain. The alien in this case is certainly creepy, and its "voice stealing" method of communicating makes the viewer squirm, but in the end, the ones that we fear the most are not aliens, but other humans.
And that is what makes this, along with Children of Earth, such a great alien story: no matter what the extra-planetary life is, the much more frightening thing is the paranoia and fear-induced violence that this alien consciousness causes.
While Rama in Arthur C. Clarke's Rama series is actually a place, it reveals another misstep in most alien portrayals. When humans land on Rama and begin exploring, they are struck by how strange the place is. The "buildings" don't appear to actually be buildings, the "cities" are apparently uninhabited, and the sheer scope and engineering of the place betray a fundamental flaw in any human-assumption-based analysis of the place.
While this unknowable other concept gets shelved a bit in the sequels to Rendezvous with Rama, the first book ends as it might in reality: the craft moves on, and humanity is no wiser than before. Rama remains a foreign thing, even after all is supposedly "revealed."
(From this short film based on the book Rendezvous with Rama)
The Buggers and the Piggies
Finally, in Orson Scott Card's Ender's Game, and maybe more so in its sequel, Speaker for the Dead, we see two new alien races that eventually challenge humanity to tolerate and maybe even love something truly other. The buggers start the story as the frightening antagonist, but it's revealed that their acts of aggression were really attempts at communication. The piggies, on the other hand, seem wild and unpredictable at first, but their horrific acts were really ceremonies of great honor.
The reality of these books, though, is that, when all is said and done, the humans in these stories find the humanity in an inscrutable other. They prove to us that something menacing and indifferent and entirely alien can sometimes become almost human. And even if that means humanizing the aliens slightly, it's a feat that's far more impressive than getting us to sympathize with blue versions of ourselves.