Glib popular culture would have you believe that alien stories didn't really exist until the nuclear age. But extraterrestrial tales go all the way back to the first century with Lucian's True History where he visits the Moon, and becomes involved in a full-blown alien war over the Morning Star. He's both an alien invader and watching the process of aliens invade another territory, which is pretty heady stuff for an ancient writer.

But as the modern world expanded and technology outstripped our abilities to really explain its workings (come on, do you know how your iPhone works, exactly?), we began looking more and more to the stars. Would some race pour out of our skies bent on conquest? On friendship? Like the deep sea, space has always been a source of terror and promise. Maybe the void will produce gentle intelligence like that found in a whale or dolphin. (This longing has found its home in numerous first-contact stories -- E.T., Close Encounters of the Third Kind, Star Trek.) But it seems far more likely that our visitors will be like great white sharks that will devour us whole. Whatever they are, we won't see them coming, and it's the uncertainty that keeps yielding up so many fantastic invasion stories.

Alien invasion stories also serve as neat analogies or escapes for our political and social fears. Unlike Nazis, Russians, or terrorists, aliens can never be outdated by history, even when we use them as political allegory. Unlike our changeable human enemies, we can gun them down with politically correct impunity. They also serve as a tidy device for binding the world together. Nothing can bring world peace like a bigger and nastier threat from the stars, so cook up those giant squids, and deposit them in New York.

Hollywood has mined this intergalactic paranoia for all it's worth. Many of them are very, very bad. But a lot of them are quite good and effective in scaring the heck out of us. These are the ones I like best.

1. Alien (1979)

The one that started it all, and failed to contain it. Giger's aliens are far and away the most terrifying extraterrestrials of cinema or television. Though they operate purely on a predatory and survival-based instinct, there's nothing sympathetic or relatable about them. They give off an impression of pure evil. What's especially revolting and frightening about them is their ability to invade everything -- your body, your ship, your planet. Nothing touched by them will survive.

2. Invasion of the Body Snatchers (1956)

Forget the remakes -- the best and eeriest version is the original 1956 one by Don Siegel. A simple story, the aliens are nothing but giant pods, silently replicating the ordinary townsfolk of Santa Mira. The aliens are merely giant seeds from space, overtaking the planet like Dutch Elm Disease, stripping Earth of its flawed and turbulent humanity. It introduced the term "pod person" to the popular lexicon, though I'm sure many in the 21st century have never seen its old origin story. (How can they? They're pods!)

3. The War of the Worlds (1953 / 2005)

Unlike Body Snatchers, I'll allow you to pick which one you prefer. The original is wonderful because of its iconic imagery. Steven Spielberg's remake, coming at the height of post-9/11 paranoia, really plays on our fears of chaos, smoke, and death. (The fiery train is still an absolutely terrifying image.) One's dated, one fumbles the ending, but together they pack a nightmarish punch, and yet an ephemeral hope that our planet will survive by its own natural resources. It's one of the rare victories that doesn't rely on technology or weaponry for victory.

4. The Thing (1982)

Alien invasion can be just as scary on a smaller scale, and nothing proves it better than The Thing. Like Body Snatchers, the threat of this alien is that it's parasitic. You can't really see it until it absorbs into and becomes something else. Then it eats you ... and all the friends and family who were fond of your appearance. At least it was contained in Antarctica. Right?

The majority of movies bank on aliens being smarter than us, and purposefully staging an invasion for their personal gain. District 9 explores the possibility of an accidental landing that became a refugee crisis. It's an uncomfortable analogy at how we deal with the "others" among us, and puts humanity in the rare position of being an alien oppressor. It says something about our species' self-esteem and intrinsic sense of justice that many feel the sequel (if there is one) will feature Christopher Johnson and a prawn army bent on rescue and revenge.

6. Signs (2002)

Signs gets a lot of flak for its clumsy twists and its religious overtones. I can't argue with that. But it's still one heck of an alien invasion movie, relying almost entirely on what you hear and think you see. It achieved more scare with a single, slender leg than most movies earn with a fleet of spaceships. (Fun personal fact -- I suffered from nightmares for two straight weeks after seeing this. Yes, I was mocked. And boy, did someone use my raw nerves to great effect during a corn maze that year.)

Aliens can occasionally be beneficial invaders. While other atomic-era films were filled with explosions and planet-mauling aliens, The Day the Earth Stood Still opted instead to urge detente. Like District 9, it implied we had the power to injure and dismantle entire races with our propensity for casual violence and discrimination. So fearful was the galaxy of us that they sent the terrifying Gort, tempered with the gentle and Messianic Klaatu to try and reason with us. I'm still waiting to see if it worked.

8. They Live! (1988)

The conceit is utter camp -- Sunglasses that can reveal our alien overlords! Badass bubble gum! -- but the message is bitingly appropriate to this day. Most alien films work on the idea of their lasers being superior to our missiles, but They Live! has them using our society against us. They don't need ray guns. They use television, Congress, churches, and cash. All they had to do was imprint it with some subliminal messages, and our human nature took care of the rest. That might just be ickier than a chest-burster.

9. Plan 9 From Outer Space! (1959)

Because sometimes, movies about alien invasions go horribly and hilariously wrong. Ed Wood Jr.'s film is a hilarious mishmash of zombies, aliens, and Vampira. Its string-controlled spaceships are as iconic as the technologically superior ones of The War of the Worlds. (Possibly even more so -- they're the go-to scene whenever a film or television show needs a B-movie reference.) It's so corny that it's adorable. Besides, aliens and zombies? It's like a horror geek's dream, only you know ... dumb.

This is at No. 10 purely because I wanted to achieve numerical symmetry with Plan 9. But it must also rank low because it's also a pretty blatant rip-off of The War of the Worlds right down to the "virus" that is the aliens' downfall. But its visual effects remain eye-popping and shocking, and while the plot may be old hat, it preys on our worst fears (a rubble-strewn Earth) and our greatest hopes (that we can unite to fight the ugly things).