The first time you watch 2001: A Space Odyssey, you’re most likely struck by a profound sense of confusion—which can be either deliriously entertaining or, if the walkouts during its 1968 premiere were any indication, frustrating.

But then there are all the other times you can (and should) take in Stanley Kubrick’s sci-fi masterpiece: a visually stunning but also thoughtful head trip that explores the trajectory of human and other life on Earth and beyond. People used to enjoy illicit substances while traveling through the psychedelic Star Gate sequence. But sobriety helps if you want to puzzle out the nifty techniques, prescient futuristic design, and yes, a few flubs, that have made 2001 such a lasting movie over the years.

From ahead-of-the-curve furniture design to geeky scientific fact-check details, here’s what to zoom in on the next time you’re sitting awestruck watching Kubrick’s space vision.

1. There’s a lot more story to 2001.

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2001’s screenplay is credited to both Kubrick and acclaimed sci-fi author Arthur C. Clarke. In fact, Clarke wrote a novel companion to the movie concurrently with the filmmaking. The book explains a lot more than the film, which keeps things very open-ended. Those wanting to pick apart the exact meaning of the ending Star Child (and what that has to do with nuclear warheads!) should go directly to the book’s pages.

2. Those leopard eyes aren’t right.

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If the natural landscape in the opening “Dawn of Man” sequence seems still and painterly, well, it is. Kubrick’s team shot footage in Namibia that was then projected on a set to create the backgrounds (notice the clouds don’t move). And those apes are humans in costumes. Meanwhile, the leopard with the wild bright eyes is actually reflecting light from the projection system beaming at it, according to The New Yorker’s fascinating feature on the movie’s making. But the “mistake” makes the animal look adequately ferocious, and Kubrick smartly kept it.

3. Stanley Kubrick couldn’t handle aliens.

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Well, at least, the director couldn’t settle on realizing their physicality on the screen. Kubrick, Clarke, and Kubrick’s wife Christiane sketched out possible visual ideas and sought paintings for inspiration in depicting what extraterrestrial life might look like. Christiane modeled clay aliens that were rejected, then banished to the home garden. Eventually, Kubrick decided not knowing the unknowable was the most sensible route.

4. Kubrick seemed to know the International Space Station was coming.

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NASA itself has pointed out that long before the low earth-orbiting International Space Station was housing crews year-round, 2001 created a strikingly similar vessel with similar purposes (and, honestly, a cooler shape).

5. There is no Sound on the moon.

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The astronauts investigating the mysterious monolith that’s on the moon find that it can also make a horrifying screeching noise. In this scene, they attempt to cover their ears. Two problems: They’re wearing space helmets, making covering your ears totally ineffective; and, even more importantly, as the moon lacks any atmosphere, there’s no sound anyway.

6. Phone booths exist in space?

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As much as 2001 got plenty of details about the future eerily right in 1968, the filmmakers also made some ... interesting period detail choices. Apparently while hanging out on a sleek space station orbiting earth, those in the future are still communicating with loved ones via phone booths, using a card and everything.

7. Branding goes to space.

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Don’t miss the clever nods to real brands in the spacecrafts, including a Hilton lobby, Howard Johnson's, and a Whirlpool device.

8. 2001's furniture of the future is very 1968.

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2001 laid a path for the future, in part, with then-new design trends that subsequently circulated through the wider culture. Sure, you might not buy one of these red sculptural Djinn chairs designed by Olivier Mourgue, but the antique furniture still fetches around $4000 online. If you do purchase one, just assure any guests that HAL is in a good mood.

9. That floating pen is off.

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The floating pen in zero gravity is one of the slyest effects in 2001. But as eagle-eyed physics enthusiasts have noted, the pen doesn’t rotate around its own center of mass as it would under those actual conditions, but rather around some other fixed point.

10. Those strange flight attendant outfits were made by a designer for the Queen.

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Costumes in 2001 were designed by Hardy Amies, a Savile Row tailor who worked with the Queen of England. The space flight attendant uniform with the voluminous hat is particularly memorable. If only it would make an appearance at a royal wedding.

11. Flat screens got their debut.

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NASA has literally confirmed that 2001 envisioned a number of features of space exploration that have since come to be. (Also keep in mind the movie came out a year before NASA made its first moon landing.) Among them, the consoles of flat screens with multiple purposes are prescient in understanding where technology was headed.

12. Stanley Kubrick invented running in space …

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… Kind of. Astronauts need to stay fit, and it’s no real surprise this became a thing, but he ushered it in beautifully. In April 2007, 210 miles above earth, astronaut Sunita Williams ran the Boston Marathon while in orbit.

13. HAL 9000 could’ve been an IBM product.

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The weirdly lovable antagonist of 2001 is the one and only artificial intelligence system who quickly dispatches with his human passengers. (And he sings while being unplugged!) IBM consulted on the production to help with the creation of HAL 9000, but backed off once Kubrick described HAL as “a psychotic computer.”

14. Vital signs tell the lie.

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According to the explanation in the movie, astronauts hibernating in their pods breathe only once a minute, and their hearts beat only three times a minute. But close shots of the vitals show that their pulses are moving normally. One wonders where the medical consultant on the set went.

15. The sun doesn’t look like that in space.

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For as much as Kubrick and his collaborators nailed so many scientific details in the meticulous making of 2001, certain basic facts are missed. The sun is repeatedly shown from space with a yellowish hue. When looking at the sun from space, it should appear pure white, since the color tinting is an effect of viewing the sun from within Earth’s atmosphere.

16. The Star Gate sequence was based on Timothy Leary's LSD trips.

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While the climactic “Star Gate” sequence, in which we enter an alien-designed portal complete with a light show, might seem like an LSD trip, it involved that and more. Kubrick was inspired by a Canadian educational film that used shots of inks and paints in paint thinner to render outer reaches. Meanwhile, one of the scientific consultants was boning up on research overseen by Timothy Leary about the effects of psychedelic drugs. The result is undeniably outrageous.