George Clooney and Sandra Bullock are usually the biggest stars on set. But even they risk being eclipsed by the dazzling effects in the film Gravity, which opens on Friday. Alfonso Cuarón's thriller is about two astronauts lost in space after an accident cuts them off from the mother ship. So convincing are the effects, which were partly knocked up in a studio in Soho, that one reporter asked Cuarón what it had been like shooting in space. "I got really dizzy while rehearsing," came the deadpan reply.
It's already tipped for Oscar glory. Here are 10 more need-to-know facts about the film Titanic director James Cameron has called "the best space film ever done".
Sandra Bullock was not allowed to wear make-up during filming, on the basis that astronauts don't. This hasn't troubled previous space films featuring actors covered in slap, but Cuarón wanted authenticity. "God help us all when my face comes rushing at you with no make-up on," said Bullock, 49. George Clooney doesn't wear any either, allegedly.
To replicate a zero-gravity environment, Bullock was strapped into a specially constructed rig in a lightbox, a walled space whose sides were 20ft high and 10ft wide. It was controlled by robots like the ones on car production lines, and had a camera attached. For some shots, the camera would zoom in from several feet away and stop one inch from Bullock's face.
Because her harness took so long to get in and out of, Bullock would spend up to 10 hours alone in the lightbox rig, communicating through a headset. Cuarón worried she might get lonely, so every morning there would be a party when she arrived on set, with a Rocky-style fanfare and a lightbox saying "Sandy's cage".
Authentic lighting was created by using 1.8 million lights that could be individually controlled. Essentially, they used the same technology that's used in giant stadium screens. This meant that if Bullock was meant to have Earth providing bounce light from her left, a giant image of Earth would appear on her left.
The film's trailer features numerous loud explosions and lots of action. The explosions were taken out for the film. As there's no sound in space, any explosion would happen in silence.
To have Clooney or Bullock fall towards the camera, the actors would not move but instead the camera would fly towards them. This combination of flying the camera and lighting Clooney and Bullock by the lightbox would then allow an accurate performance to be filmed of each of the two lead actors. But for a shot where they were in their suits, only their faces would be real – the rest of their bodies, their suits, hands and environments were all digital and fully 3D animated.
The film lasts only 91 minutes, which makes it quite short for a major feature, and is mostly in silence, except for the soundtrack. As Bullock had her head in a helmet for so much of the time, Cuarón created CDs of sounds and music that were specific to each scene.
The last film to attempt replicating zero gravity was Ron Howard's Apollo 13. He used a combination of actors on wires in front of blue screens, and short takes of weightlessness filmed using the "vomit comet" – Nasa's Reduced Gravity Aircraft. But Cuarón wanted to film long takes, and for it to be in 3D.
Almost every Hollywood actress had been billed to play Bullock's role at some point during pre-production. Scarlett Johansson, Blake Lively, Marion Cotillard and Natalie Portman were all tipped, as was Angelina Jolie. Robert Downey Jr was down to play Clooney's role. It's thought Warner Brothers rejected Jolie after she demanded a $20m (£12.5m) fee.
Gravity had a production budget of $100m, but has already netted more than £360m since its US release. Despite some minor quibbles, space experts are impressed. Buzz Aldrin, the second man to walk on the Moon, said: "Going through the space station was done just the way that I've seen people do it in reality."