Chemistry is a hard thing to pinpoint or quantify and is just as impossible to predict. This is especially true when it comes to acting, which is why actors have to partake in special chemistry screen tests in order to see if they have any heat with their potential costars. Even real-life couples have a hard time showing chemistry onscreen, so there is really no way to tell whether two actors will have that special something until they are in front of a camera together. In the case of "Gravity" stars Sandra Bullock and George Clooney, the chemistry the two share in the film is completely off the charts.
The two movie stars have actually known each other for more than twenty years, which may contribute to the great bond their characters seem to have in the film. In fact, they have known each other since before they both became famous: he on the NBC medical drama "ER" and she as the love interest for Keanu Reeves' character in "Speed." The fact that they have been friends for so long and helped see each other through painful (and even painfully public in the case of Bullock) divorces says a lot about their onscreen bond.
In the film, from "Children of Men" director Alfonso Cuaron, Bullock plays Ryan Stone, a NASA scientist who is embarking on her very first space flight. A small crew is sent into space to make repairs to the Hubble Telescope, and pilot Matt Kowalski (Clooney) is at the helm in what is his final mission. Even though he is about to retire, Kowalski clearly loves his job and is a good leader to the crew. He takes rookie Stone under his wing to help her out on her first mission, joking with her in a way that is most paternal.
Even though Kowalski seems protective of Stone at first, a little bit of flirting is still going on, especially because Clooney's character recently found out his wife had been cheating on him. Clooney's real-life friendship with Bullock comes into play here, because even though the two stars seem to flirt on the red carpet and in interviews, they really are just friends who seem very protective of each other. They clearly have each other's back in real life, and the same can be said of their characters in "Gravity."
As the film progresses, the two characters find themselves in grave danger after debris from a Russian satellite destroys their ship, killing the rest of the crew and cutting off their oxygen and communications with NASA. They have to work together to figure out a way to get to safety and find a way back to earth. These two virtual strangers, who only know each other a little bit, now have to rely on and trust each other as if they had been working together for years. Somehow, it is believable to the audience that these two can find a way to work together, because the characters seem to have a familiarity that goes far beyond the short time they have known each other. This is arguable because the two actors portraying them have known each other for over two decades.
The two imperiled astronauts find safe haven on a space station and later on another rocket that they must try to use to get back in communication with NASA. They can't rely on anyone but themselves, so they must put their heads and knowledge together to devise a plan. As they plot a way to survive increasingly slim odds against them, they debate and occasionally bicker like an old married couple. Then, they encourage each other as each person does his or her assigned part of the plan. It's a familiarity and trust that is born out of intense situations like the ones depicted in the film. During the most harrowing of scenes, the two actors amp up the chemistry to the point that it is downright electric, making everything on screen feel completely believable to the audience.
There is an old saying that life imitates art, but in the case of "Gravity," it may just be that art imitated life, or at least shares a few similarities. The great bond between Clooney and Bullock is mirrored in the film, which will leave audiences wonder why these two superstars don't team up more often. If "Gravity" does well at the box office, they might not be able to avoid teaming up again in the future.