It can't be easy being the third choice for a coveted role, but after viewing "Gravity" it will be hard to imagine anyone besides Sandra Bullock playing Dr. Ryan Stone in Alfonso Cuarón's groundbreaking new film.

Originally, Angelina Jolie was attached to the film when it was set up at Universal Pictures and for some time Natalie Portman was the leading candidate to replace her when it went to Warner Bros. Eventually, Bullock, coming off an Oscar win for "The Blind Side," became the unexpected choice. Four months from now, you'll hear her name among the best actress nominees for the 86th Academy Awards. And, barring a last minute surprise from "American Hustle's" Amy Adams or "Saving Mr. Banks'" Emma Thompson, it will likely come down to Bullock and "Blue Jasmine's" Cate Blanchett for the win. Yes, America's former sweetheart is that good, that triumphant in Cuarón's immersive drama.

"Gravity" finds Bullock playing a first-time NASA astronaut who gets caught unprotected in space after a massive debris field destroys the ship.  She then endures a dangerous journey from one space station to another in an attempt to land safely back on Earth. George Clooney co-stars as the more experienced astronaut Matt Kowalsky, but a majority of the screen time is just Bullock and the stars. And, frankly, that would terrify any actor. Speaking to HitFix earlier this week [in an interview you can view at the top of this post], Bullock admits if the acclaimed filmmaker of "Y Tu Mama Tambien" and "Children of Men" wasn't behind it all she might have turned the role down.

"Because of Alfonso and his work before I don't think there is anyone else I think I would have had the balls to step in and do it with because my desire to work with him was so strong," Bullock says. "And after meeting him as a human being I went, 'I can't believe this person I sort of idolized turned out to be an extraordinary human being. Usually you're disappointed. We let people down a lot. [Laughs.]" 

Bullock continues nothing Cuarón, "exceeded who he was as an artist to me. If this person can feel what he feels about life and have these point of views and tell this emotional story…I know it scares the crap out of me to do the rest of it, but if I thought about it too long I probably would have said no.  I said, 'Make my child happy while I'm there. He has to be there with me, I can't be there without him. If you can create that atmosphere there then I'll show up and make it.'"

Cuarón's film is a mixture of visual effects and practical effects, but the film contains much less CG then you'd expect. One fantastic sequence finds Ryan (Bullock) floating through a space station as the camera follows her from one module to another.  At first glance you think it must be CG, and while there has to be some element of that in the frame the image is mostly Bullock. In order to pull this off, Cuarón brought in the puppeteers from the acclaimed stage play "War Horse" who devised a mechanism to duplicate the look of weightlessness for his actors.  They invented a 12-wire harness that carried Bullock, in this case, around like a puppet. "The Heat" star admits it was painful, but it's also "so cool."

"Long story short, they had all these cameras taking pictures of my body. Created almost like a Xerox copying thing, a carbon fiber copy of my chest plate. Just breasts, rib cage that seamlessly placed over my body. I could put my clothes over it," Bullock reveals. "It then had little hooks in it and I would lay down on a table, it was like an operating table, where all these technicians would come in and they would hook me up to the wires and strap my legs [into them].  And then they would lift me up and the puppeteers from 'War Horse' were in the back puppeteering me. And then I had to move the body, do the swing and do everything myself while they would push me in one direction where zero g would push you, not where earth would push you.  Everything was designed so I then had to react the way zero g is. It was the closest thing to feeling like I was flying making this movie, the 12-wire. It was painful, but it was so cool."

While Cuarón and crew created intricate storyboards for the picture, Bullock says she didn't have a clear idea how it would all eventually come together. Like many moviegoers, she was overwhelmed by the final result.

"I had never seen George's side. I'd never seen the stars, the space shuttle. I didn't know what the music was. I didn't know what I looked like in the suit. I didn't know what we were making or what that looked and felt like. And, I felt like, all of a sudden, this was a gigantic organism that had been created out of technology. And to see it in that beautiful 3D where it was used so sparingly and emotionally? I don't know how to describe it. But, I was able to be moved by Alfonso's work rather then shred myself because I hated my work which will come later on when I'm like, 'Why did I do this? I look so bad. I look so bad.' [Laughs.] But, you've got to appreciate the ride."

"Gravity" opens nationwide in 3D and in IMAX on Oct. 4