In Alfonso Cuarón's excellent new film Gravity, Sandra Bullock and George Clooney are marooned in space. It has been described as "the closest most of us will ever come to going into space." But it's easy to tell from the trailers that Gravity isn't really about the joy of space travel; death hangs over this film. Watching Bullock struggle in her claustrophic, terrifying spacesuit as she realizes she's cut off in the universe from — well, everything — you can't avoid queasy, dreadful thoughts about what it might actually be like to die in space. Is there a nice way to go? Which would be worse: slowly wait until your spacesuit runs out of oxygen? Or going for the quick option of ripping off your suit and exposing yourself to the vacuum of space?

Jonathan Clark of the Center for Space Medicine at Baylor College of Medicine thought over the dilemma for us, and, assuming there is no chance of rescue, he'd go for the exposure option. "In a vacuum you take a few breaths and you're unconscious within probably 10 seconds," explained Clark, who has served as a Space Shuttle Crew surgeon and is the Red Bull Stratos medical director. "You're totally out. It's not like you're suffering. I think you'd suffer more in a suit. And part of it would be that you know you can't be rescued and that you know you’re going to run out of oxygen. It's the psychological impact of knowing you're dying."

As Clark noted, there have been cases of humans surviving the vacuum. In the mid-sixties a NASA test subject in a chamber was exposed. He remembers his tongue starting to boil and Clark explained others have said they felt grittiness on their eyes, "basically bubbles forming." That's ebullism. Ultimately, though, you probably don't suffer very much, Clark said: "Every time you take a breath you are getting rid of oxygen. Then you just go out. You're just unconscious and then your brain starves and it dies and then your heart stops, but you don't suffer. It's pretty quick." On the other hand, if you're in a space suit that runs out of oxygen, carbon dioxide could become a problem—a problem which is in fact on display in the film. "If you’re in a suit though and you run out of oxygen the only downside to that is you could end up building up carbon dioxide and that could make you very anxious and air hungry," Clark explained. In the film, Sandra Bullock's panicked heavy breathing makes this situation feel all too real.

It's no spoiler to say that her character faces the discomfort of dying in her suit during her fight for survival. In doing so she spins out of control, the camera taking on her perspective in nauseating fashion. Clark said, "you're basically like a hockey puck, you're just going wherever the forces of mass and acceleration take you," though he did add that you can act like a "skater" and use your arms to lessen your spin. A NASA representative told us that likely wouldn't happen in a real life situation: their spacesuits are affixed with a SAFER backpack, a jet pack, that allows astronauts to control themselves. While Bullock's character does spin out of control at one point in the film, it's one of the errors Jeffrey Kluger of Time pointed out in his "fact check" of the film. That isn't the only not quite realistic part of Gravity — Dennis Overbye at the New York Times points out a major plot hole in the film, having to do with the differing orbits of the Hubble Telescope and the International Space Station — but its general sense of, uh, spaciness apparently ring true. It's hard to argue with a rave review from Buzz Aldrin in The Hollywood Reporter. "We're in a very precarious position of losing all the advancements we've made in space that we did 40 years ago, 50 years ago, " he wrote. "From my perspective, this movie couldn't have come at a better time to really stimulate the public." Stimulate it may—it also forces you to contemplate your place in the vastness and loneliness of space.