Sometimes Hollywood gets the science right – or at least not completely wrong. With input from experts, we’ve picked sci-fi’s most plausible big-budget films. – By David Kushner

In late 2009, a writer, a producer, a director, and three scientists sat in a Los Angeles conference room. They were discussing Marvel’s Thor – a film based on a comic book that was in turn inspired by the Norse god of thunder – about an arrogant warrior who, at the start of the film, violates a truce by attacking the Frost Giants.

As the film team described their vision of the fight, Sean Carroll, a theoretical physicist at the California Institute of Technology, knew the filmmakers had a problem. “They wanted the Frost Giants to fall off the edge of a disc-shaped planet,” he says. “That makes no sense. Where does the gravity to pull them down come from? Enough people know how gravity works that it would throw them out of the movie. You’d get a lot of giggles.” Carroll and the other scientists argued their point, even though, Carroll says, “it was clear some people thought we were being uptight killjoys”.

But producer Kevin Feige sided with the scientists, and in the final cut, the Frost Giants’ planet was spherical. That was just one way that Carroll, a clean-cut 45-year-old who has advised on films such as TRON: Legacy and the TV show Bones, helped the production.

Read how filmmakers are turning more frequently to experts to make their movies more believable, as well as find out what PM's 10 most accurate sci-fi movies are, in the February 2012 issue of Popular Mechanics - on sale on 23 January.