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A Real Astronaut Talks The Science Of "Gravity"

Movie magic makes space travel look easy. Here’s how the Oscar-winning movie compares to reality. Warning: Spoilers ahead.

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This is astronaut Leroy Chiao.

Leroy Chiao

After being with NASA for 15 years and on six spacewalks, he knows a thing or two about space. He also saw Gravity — and liked it! Here are some of the things the movie depicted and how they compare to reality.


Ryan Stone (Sandra Bullock) is on a spacewalk with Matt Kowalski (George Clooney) to fix the Hubble Space Telescope.

Reality: The Hubble was designed to be serviced, so a repair mission isn't unusual. But maintenance usually requires removing larger modules with connectors, not individual circuit boards. "Something similar did happen, but normally the operations are planned so you wouldn’t have to do that sort of delicate work in a suit," says Chiao.


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Stone has a hard time keeping her space lunch down.

Reality: Space sickness is different for every astronaut, but most of it stems from your balance system. Otoliths are little ear stones that are sensitive to gravity and acceleration, and they help you sense movement.

In space, those stones are tumbling around and sending all sorts of confusing information to your brain, making you feel nauseated and dizzy. After a day or two, your brain starts to ignore the signals and the nausea subsides.


Space Noise

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In between bouts of astronaut banter and shuttle noise, space is so quiet you can hear yourself breathe.

Reality: In a vacuum like space, there is no sound because sound waves don't have a medium to travel through, so any spacecraft whooshes are purely for your enjoyment. (See: Star Wars.)

Inside the suit, because oxygen is continuously blown over your face, there's no chance of you being able to hear your own vitals. "It’s a very noisy environment inside the suit, but it’s a good noise," says Chiao.

Space Debris

Debris from a neighboring satellite knocks out all communication and sends Stone tumbling into the pit of space.

Reality: NASA closely monitors any impending obstacles, and missions are planned to minimize any chance of catastrophe. "There’s a lot of stuff in space, but frankly, it’s still a pretty big sky," says Chiao. It's unlikely to run into something even if things aren't being monitored — especially if the debris comes from an entirely different orbit.


Kowalski jets his way over to Stone and brings her back to the shuttle.

Reality: Manned Maneuvering Units, hand-controlled and propelled by nitrogen, were used for three missions in 1984 but were never recertified after the Challenger accident in 1986. Astronauts are always tethered.


Kowalski finds and rescues Stone.

Reality: Helmets have very limited visibility. Chiao's scariest moment was when his boots became disengaged from the robotic arm that was holding him.

"I knew I was drifting away from the shuttle and the station, and I knew intellectually that I had connected my cable, but I couldn’t see it," he says. "I was rotating very slowly and had to wait about 15 seconds before my body rotated to the point where I could see that I was still connected."


Space Suits

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The American suits have transparent visors and helmet lights.

Reality: True! Suits are designed to withstand direct sunlight (250°F) or deep shade (-250°F). Helmets also have lights so astronauts can work at night and gold visors, or glare shields, with UV protection that works just like sunglasses.


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Stone and Kowalski putter their way over to the International Space Station (ISS).

Reality: The Hubble and ISS are in completely different orbits and aren't visible to other spacecraft. "They’d never have the fuel to be able to change their orbital plane, especially in a Man Maneuvering Unit," says Chiao. "Not even a space shuttle."


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When they arrive at the ISS, Kowalski untethers himself from Stone Titanic-style and floats away into the abyss so that she can survive.

Reality: This was the most cringeworthy violation of physics to Chiao. She would have been easily able to tug him in with her if he had continued to hold onto her, he says. "He wouldn’t have just floated away."



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Stone enters and exits the ISS and Chinese station Tiangong like it ain't no thang.

Reality: Not only does prepping to put on a suit take hours, you also have to depressurize the airlock so you can get out the door and repressurize it when you return so you can take your suit off.

Carbon Dioxide

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So Stone doesn't prep the airlocks, ever.

Reality: All the airflow in shuttles and stations is forced because there's no natural convection. The air always has to be moving, otherwise you'll develop little pockets of carbon dioxide everywhere you've been breathing (not unlike tiny toxic ghosts). In an airlock, you take a big flexible hose and position it to blow fresh air in and keep it circulating.

Putting on a Suit

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Stone puts on a Russian space suit and is ready to go.

Reality: The pressure inside a suit is lower so that you can have flexibility in your arms and fingers to move around. "The more pressure you have to fight, the more stiff the suit is, and the more energy and strength you need to do things," Chiao says.

To get to that lower pressure, you have to pre-breathe pure oxygen to eject as much nitrogen out of your blood as you can — otherwise it'll bubble up and give you a nasty case of decompression sickness, better known as the bends.


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Stone bypasses a cute fireball at one point aboard the ISS.

Reality: You would never bypass flames. "Fire’s one of the things that’ll kill you quickly," says Chiao. "You worry about pressure loss, fire, and toxic atmosphere."


Taking Off a Suit

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Stone quickly disrobes.

Reality: Suits are designed for a single person to take it off, but it takes a while to extract yourself out of the snug and stiff upper torso. On Earth, you have your body weight to pull you down, but with no gravity, "either your buddies have to pull you out, or you’ve better figure a way to wriggle your way out of the suit," says Chiao.


Stone is only wearing boy shorts and a tank top under her suit.

Reality: Astronauts layer like incontinent Midwesterners. That includes thermal underwear and a maximum absorbency garment (i.e. diaper). They also wear a liquid cooling garment with sewn-in tubes that circulate cooling water to get heat away from your body, which race-car drivers have adapted.

Fire Extinguishers

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Stone thrusts herself over to Tiangong using a fire extinguisher.

Reality: That would be like never having skiied and then attempting freestyle flips on your first try. You'd really need to practice, otherwise you'd send yourself tumbling. "Theoretically and physically, of course it’s possible, but it takes some training and talent to be able to do it," says Chiao.

But after all, it's show biz!

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"Certainly as an engineer, I see all the technical inaccuracies, but I’m able to ignore those because I see the big picture," says Chiao. "After all, this is a movie, and it’s for entertainment!"