It’s a unique writer-filmmaker collaboration.

Stanley Kubrick and Arthur C. Clarke conceived the story together, inspired by some of Clarke’s short stories. Clarke’s novel was written as the film was being made, with Clarke checking in along the way to try as best he could to match the events in the novel to the events in the film. The resulting novel is neither the basis for nor a simple adaptation of the film; it’s a second, simultaneous product of the same creative collaboration.

It got space right.

Released in 1968, 2001 immediately became a favorite of astronauts and engineers in the space program for its treatment of space as a site of slow wonder rather than of zip-bang-pow theatrics. When astronauts first saw the dark side of the moon, they later told Clarke, they considered telling Mission Control that they’d seen a monolith.

It got aliens right.

2001 shows how uncreative most movie aliens are: they’re just like us, except slimier. The alien intelligence depicted in 2001 is completely beyond our comprehension, and humans’ encounters with it are deeply unsettling. The plot of the film neatly uses our relationship to this alien intelligence to dramatize how incomprehensible the humans of today would be to our distant ancestors—and how incomprehensible later generations of humanity might be to us.

It’s stylish.

While there’s a timeless beauty to many scenes in 2001, it’s also an elegant example of 1960s design. Check out details like the chairs in the space lounge, the moon base photographer’s suit, and the use of lettering in console readouts.

It’s wound whip-tight.

For all its patience, the pacing of 2001 consistently shows the hand of a master. That’s most clear during the tense confrontation with HAL, but the film’s opening and closing sequences are just as carefully crafted. Nothing here is lazy or sloppy.

Its use of music is inspired.

An original score was written for the film, but Kubrick wisely stuck with the music he’d been using during production: a selection of classical and avant-garde music ranging from Richard Strauss to György Ligeti. The resulting sequences represent some of the most successful uses of music in the entire history of movies, turning long, potentially tedious sequences into deeply immersive experiences.

Its special effects hold up.

It’s obvious the ships are models—but then, real spaceships can look a lot like models too. What’s most important is that the effects are beautiful and seamless, creating a completely consistent and engrossing milieu.

It’s dryly witty.

HAL’s dialogue is the most famous example of this (“Without your space helmet, Dave, you’re going to find that rather difficult”), but also notice Dr. Floyd carefully reading the directions for the zero-gravity toilet.

It puts humanity in its place.

The original conception of 2001 was much more explicitly anti-war; Kubrick had just released Dr. Strangelove, and the novel reveals that the Star Child stops a nuclear war. Kubrick’s decision to exercise restraint in that regard guaranteed the film’s timelessness, but nonetheless, the broad depiction of humanity as a very fallible race remains.

It’s just weird.

There are few films as ambitious as 2001. It requires multiple viewings, which are consistently rewarding as the film’s grand, layered themes become apparent. Many first-time viewers find 2001 confusing, even aggravating. That long visit to the planet of the apes, the seemingly interminable spaceship-docking sequence, the fact that Floyd is established as a central character but then disappears, and especially the increasingly trippy denouement—all are totally bizarre, and all contribute to the film’s enduring power. Outer space has never seemed more strange, or more fascinating.

– Jay Gabler