They say there aren’t movie stars anymore. Sandra Bullock’s performance in “Gravity” would beg to differ. The sci-fi film is basically a two-hander between the star and the director. And yet, in an era of massive casts packed with big names “Gravity” still grabbed people’s attention. It’s a riveting film both immense and claustrophobic at the same time. Strap in for 20 facts about “Gravity” you might not be aware of.

Director Alfonso Cuaron was eight when Apollo 11 landed on the Moon. This had a big impact on him as a child, which was of course true of many children of the era. He even wanted to be an astronaut as a kid, although his success as a director would seem to indicate he made the right choice.

“Gravity” was written by the duo of Alfonso and Jonas Cuaron. As you might be able to surmise, the two are related. Jonas is the son of Alfonso, though he has written and directed two films without the collaboration of his successful father, with a third in the works.

Cuaron did not set out to make a space movie. He was interested in making a movie about adversity, which led to him thinking of different isolated locations that could provide adversity. Eventually, he figured, hey, what’s more isolated than being alone in space? Cuaron has gone as far as to say “Gravity” isn’t a science fiction film, but a “drama of a woman in space.”

Dr. Ryan Stone is the only character in the movie for a lot of it. Whoever was cast in the role would have to carry the film solo, a la Tom Hanks in “Cast Away.” Many actresses were considered. Angelina Jolie was attached but dropped out. Actresses from Maria Cotillard to Natalie Portman to Blake Lively and many more were also considered. It’s surprising that it took them so long to land on Sandra Bullock, given what a movie star she is.

Originally, Robert Downey Jr. was in talks to play Lt. Mark Kowalski, the second-most-important role in the movie. Then, he left the project to take a role in another film that never came to fruition. With Bullock already attached, “Gravity” went out and got George Clooney, making the process a little simpler than casting the lead.

Bullock and Clooney are huge stars, and they needed to be because you don’t spend time with any other character in the film. Everybody else who appears in the movie is a voice-only performance. Sure, that includes the voice of Ed Harris, but that’s still rare.

Most of “Gravity” is set in space, where obviously they did not actually shoot. That was all shot in a studio in England. However, there was one scene shot at Lake Powell in Arizona. It was a fitting shooting location, as it’s also the setting of the astronauts’ landing scene in “Planet of the Apes.”

The director really wanted to let his shots breathe, and wanted to do a lot of tracking shots to make it feel like an IMAX documentary. Indeed, there are only 156 shots in the film, with an average of 45 seconds per shot. Even in a lean 91-minute movie that is an unusually low number of shots for a film of this length.

Bullock spent much of the movie in a giant mechanical rig to create the movements necessary to make it seem like Stone was bouncing around in space. Getting in and out of the rig was difficult and time-consuming, so Bullock decided to just stay in it instead. Bullock would spend up to 10 hours a day in her rig, which was nicknamed “Sandy’s Cage.”

The trailer for “Gravity” is full of explosions and sounds designed to grab your attention. This is not uncommon in films set in space, of course. However, in reality, there is no sound in space. Cuaron knew that, and he wanted to be honest to the science of the vacuum of outer space. All of those scenes in the actual film do not have explosion sounds or any sounds. They were added to the trailer.

For a movie that isn’t animated, there is a ton of CGI in “Gravity.” According to the visual effects crew, 80 percent of the movie is CGI. For comparison’s sake, only 60 percent of “Avatar” is CGI.

In an era of remakes and IP-driven films, “Gravity” proved a massive success at the box office. Granted, it was released in the era of IMAX 3D being viable, but nevertheless, it was a huge hit. The movie made $723.2 million worldwide. In fact, “Gravity” is the highest-grossing movie in the careers of both Bullock and Clooney.

Even though the movie only had two actors in it more or less, “Gravity” got plenty of Academy Award nominations. It racked up 10 nominations, tying with “American Hustle” for most of that year.

While “Gravity” did not win for Best Picture, and Bullock did not win for Best Actress, the movie still took home a lot of hardware at the Academy Awards. It ended up with seven Oscars. Most of them were for technical feats, but Cuaron also won Best Director. With seven wins, “Gravity” is second only to “Cabaret” for Oscar wins without winning Best Picture.

“Gravity” is not letter-perfect in terms of accuracy – Neil DeGrasse Tyson found reasons to nitpick, naturally – but it got a lot of love for how accurate it is. This includes former astronauts. One particular fan of the movie was Buzz Aldrin, who was of course part of that Moon land that inspired Cuaron all those years ago.

In “Gravity,” one of Stone’s transmissions is intercepted by Aningaaq, a fisherman in Greenland. We just hear his voice in the movie, though. However, Jonas Cuaron made a short called “Aningaaq,” which shows that conversation from his perspective.

A NASA scientist named Donald Kessler came up with a theory in 1978 about the possibility of too much space debris leading to a chain reaction of crashes between said debris. It was called Kessler Syndrome, and it could theoretically happen. While it has not happened in real life, Kessler Syndrome is on display in “Gravity.”

Actors often get insight from people who have had the real experiences they are trying to replicate. For “Gravity,” Bullock talked to astronaut Cady Coleman. It was not your typical conversation, though. Coleman called down to Bullock from the International Space Station.

Cuaron was having trouble figuring out how to resolve the story of Clooney’s character. Considering that he dies early in the film, that was a bit complicated. It was Clooney’s idea to have Stone hallucinate Kowalski, and he even wrote some of his dialogue himself.

For one scene, Bullock needed to hold her breath underwater. Cuaron wanted to make sure he wasn’t asking too much of his star, so he agreed to hold his breath along with her. Then he found out he could not match Bullock’s lung capacity. She was just fine, but Cuaron struggled to keep up.

Chris Morgan is a sports and pop culture writer and the author of the books The Comic Galaxy of Mystery Science Theater 3000 and The Ash Heap of History. You can follow him on Twitter @ChrisXMorgan.

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