So, it's completely possible that a vehicle in a crewed space mission could be damaged by debris in orbit—even catastrophically. That part holds up to scientific scrutiny.

On to the next bit: showing someone adrift in space. This comes with its own problems. To begin with, orbital mechanics are incredibly counterintuitive. For example, if you're adrift in space, 50 feet behind the space shuttle, equipped only with a wrench, what do you do?

Those of us familiar with Newton's laws of action and reaction might throw the wrench away from the spacecraft, in the hopes that the reaction would push us toward the shuttle. But thanks to the peculiarities of orbital physics, we might actually need to throw the wrench toward the spacecraft because, believe it or not, this will help us catch up by dropping us into a faster orbit.

But even so, there's just no way an orbital change would save the two Gravity astronauts. The Hubble Space Telescope and ISS are in completely different orbits, at different altitudes, passing over different parts of the Earth. There's no practical way a space shuttle on a mission to one of these objects could change orbit to visit the other. In fact, because of this, NASA had to take special trouble with 2009's final space shuttle repair mission to Hubble: Knowing that Atlantis wouldn't be able to make it to ISS if it could not re-enter Earth's atmosphere, NASA officials readied the space shuttle Endeavour for a possible rescue mission.

Gravity's science advisor is Dr. Kevin Grazier, an astrophysicist specializing in computational orbital dynamics, the study of how objects in orbit interrelate. It was exactly the specialty needed for this movie. Kevin has been the science advisor for many SyFy-channel shows. I got to know him through his work behind the scenes of Battlestar Galactica; eventually he and I co-wrote the book The Science of Battlestar Galactica. Knowing what sticklers for accuracy we both are, I contacted him last week to talk about the science of Gravity.

What is the role of a science advisor to a movie?

A large part of the job is persuasive. It is incumbent upon the science advisor to say, “The technical dialogue on page 21 isn’t really what a scientist would say, but HERE is some dialogue that a scientist would say, and it’s a ‘plug and play’ replacement.” That’s why I can not emphasize enough that anybody who has dreams of working as a science advisor in Hollywood should take a screenwriting class or two. Learn the writers’ concerns.

But sometimes the powers that be still ignore the science?

Often a story worth telling can fall apart if there is a complete dedication to perfect science. The goal is to make everything seem grounded enough in the physical world that it seems real.

So story trumps science every time. It’s the job of a science advisor to know where pushing back on the science is important, and where to just say, “Let’s go with it.”