How Sandra Bullock studied with a real astronaut for ‘Gravity’ (over a nice merlot)

In the new film “Gravity,” directed by Alfonso Cuarón, Sandra Bullock spends most of her time alone, in zero gravity -- 373 miles above the Earth’s surface.

That wasn't easy to pull off, either for the Oscar-winning actress or for the film’s production crew.

“I pushed my body to the extreme,” Bullock said of portraying Dr. Ryan Stone, a medical engineer out on her first shuttle mission. “Strength-wise, I had to know I could do anything Alfonso asked of me at any given point, so not a day went by that we didn’t train.”

Because of a chance meeting at a wine packaging facility between Bullock’s brother-in-law and the sister of Catherine "Cady" Coleman, an astronaut with more than 4,330 hours in space aboard the Space Shuttle Columbia and the International Space Station, Bullock was able to get advice on how to “float” in space from a veteran astronaut.

'The pervasive view of the Earth, and how you see it reflected in the helmet -- it’s like you can’t get away from the view.'

— Catherine "Cady" Coleman, an astronaut with more than 4,330 hours in space

“(My brother-in-law) got my number to Cady, who was at the ISS at the time, and she called and I was able to literally ask someone who was experiencing the things that I was trying to physically learn,” explained Bullock. “I was able to ask her about how the body works, and what do you do, and what do I need to reteach my body physically to do that cannot happen on Earth. It was just a really coincidental, fortuitous thing that happened -- over wine -- that got me the final piece of information that I needed.”

“You’re in a really unusual environment -- it’s a very profound environment,” Coleman told FoxNews.com about her experience in space. “The pervasive view of the Earth, and how you would see it reflected in the helmet -- it’s like you can’t get away from the view.”

Coleman also appreciated the emotional journey Bullock’s character went through. “It took me a while to realize that (Stone) didn’t solve her problems in the beginning as effectively sometimes -- not because she wasn’t capable of it, but because she hadn’t decided whether she wanted to live,” Coleman said. “And that can happen to anybody -- no matter how trained they are, no matter if they are a woman or a man.”

Bullock, for her part, is grateful that Cuarón and his son, Jonás, wrote the part of Ryan Stone specifically for a woman.

“It wasn’t an afterthought. It was, I think, an integral part of the story,” Bullock said. “It’s revolutionary in the fact that a studio on blind faith would fund something as unknown as this.”

Coleman, meanwhile, sees Bullock’s portrayal as inspirational. “I think that it’s going to empower young women in ways we that can’t even imagine.”

One of the film’s biggest challenges was replicating the effect of zero gravity in space. Traditional theatrical wires could not give the desired illusion of weightlessness. “With wires, you can see the strain on the actors,” explained Cuarón. “Gravity is still pulling everything down.”

To create a realistic illusion, filmmakers devised a custom, 12-wire rig that was operated by a team of puppeteers. Bullock served as a sort of live marionette, spending hours in the rig, “floating” in space. A cheerleader and gymnast in high school, Bullock used her early training to make it appear as though she was gliding effortlessly through the interior of the International Space Station.

“It’s just core strength,” Bullock explained. “From a dancer’s perspective, just making sure that you weren’t going to hurt your body -- that you could be very agile and physical to maintain your body in a rig that’s load-bearing -- with the load as your weight, for long hours of time.”

The effort was worth it, even for a perfectionist like Bullock. “There was no time to pick apart one’s performance, because you were inundated with the extreme beauty and emotion that (Cuarón) created visually,” Bullock said. “We had that same reaction -- I think that George (Clooney) and I both did -- we both went, ‘Wow.’ You can’t really speak after the film’s over.”

“Gravity” opens in theaters on October 4. The film will be released in 3D and 2D and IMAX, and has been rated PG-13 for intense perilous sequences, some disturbing images and brief strong language. For more information, check out gravitymovie.warnerbros.com.