KSJ Tracker October 7, 2013

Gravity - Covering the Scientific Plausibility of the Movie


The new blockbuster Gravity has launched a number of critiques from science writers, and that’s great, since the film offers a teachable moment. The best of those science critiques enhanced the film’s impact by allowing us to learn as well as absorb entertainment.  

I saw the movie last weekend, and when it was over, I was eager to read about the scientific plausibility, or lack thereof.

The film is set on a Hubble Telescope upgrade and servicing mission. During a space walk, the Shuttle and Hubble are hit with a rush of debris. Turns out the Russians blew up a satellite and the debris hit other satellites, setting off a terrifying chain reaction. Astronauts played by Sandra Bullock and George Clooney are sent tumbling through space.

(Spoiler Alert: If you haven’t seen the movie, you might want to hold off reading the rest of this, though I won’t give away any more here than is revealed in the pieces I’m critiquing.)

The events that follow raised a bunch of scientific questions. 1. Is the debris cascade scenario plausible, and if so, would the protagonists intersect the debris every 90 minute orbit? Wouldn’t the debris itself be on its own orbit? 2. Wouldn’t the remaining crew and all their belongings be sucked out of the Shuttle once it sprung a hole? 3. How could the International Space Station be so close to the Hubble that the astronauts could even think of getting there in less than 90 minutes with a single jet pack? 4. What was the force that pulled George Cooney’s character away from Sandra Bullock once they reach the ISS?

In his blog for Slate, Phil Plait addressed most of the questions that sparked my curiosity, and answered them in a comprehensible way. For some reason he started with a long section apologizing for picking on the movie, but his post was good once he finally got to the point. Jeffery Kluger weighed in at Time, also with a long apologetic pre-amble. Astronomer/popularizer Neil DeGrasse Tyson was less apologetic, and also less complete. He reportedly tweeted his complaints and got picked up by various news outlets.

Dennis Overbye wrote on the science of Gravity with his usual flair in a Science Times story called The Astronaut and the Writer.  He watched the film with Michael Massimino, an astronaut who had been on a Hubble servicing mission. Overbye starts out with the aspects of the film that impress him and his astroanut companion as realistic - details such as the space wrench used. Then he gets to the unrealistic part:  

Unfortunately, with all this verisimilitude, there is a hole in the plot: a gaping orbital impossibility big enough to drive the Starship Enterprise through….. As we recall from bitter memory, the Hubble and the space station are in vastly different orbits. Getting from one to the other requires so much energy that not even space shuttles had enough fuel to do it. The telescope is 353 miles high, in an orbit that keeps it near the Equator; the space station is about 100 miles lower, in an orbit that takes it far north, over Russia.

To have the movie astronauts Matt Kowalski (Mr. Clooney) and Ryan Stone (Ms. Bullock) zip over to the space station would be like having a pirate tossed overboard in the Caribbean swim to London.

Good as far as it goes, but he doesn’t address all those other big questions, such as why George Clooney’s character gets pulled out into space. This scene was weird. Clooney and Bullock both make it to the ISS, and then in trying to grasp the station, Bullock’s foot gets caught in the parachute lines and she’s got Clooney by a tether.  It should be easy enough for her to reel him in. Talk about catch of the day!

And yet, Clooney’s character is being pulled hard away by what appears to be a space riptide. What is pulling him?  The Great Attractor? A Supermassive Black Hole? Relationship phobia? Angelina Jolie? My movie going companion thought it was related to Clooney’s contract negotiation.  

Phil Plait picked up on this problem:  

All she had to do was give the tether a gentle tug and Clooney would’ve been safely pulled toward her. Literally an ounce of force applied for a few seconds would’ve been enough. They could’ve both then used the shroud lines to pull themselves to the station.

…And lived happily ever after. Plait says our intuition is being fooled. Really? We’ve been watching the astronauts in orbit for a while. Until that time they hadn't been pulled violently toward the Earth. I've seen men pull away from seemingly promising relationships before, but this is a bit much.

Kluger’s Time piece got at the plausibility of the disaster premise and the 90-minute period of the debris terror:

First of all, the Hubble orbits at an inclination of 28.5º, which maximizes the time it spends passing over the American mainland on its various trips around the planet. The shuttle, in most cases, stays at that angle too. Russian satellites, however, orbit at higher inclinations, for the same reason—to keep them as close as possible to the Motherland. Junk from a Russian pigeon-shoot might cross the shuttle’s orbit on some of its passes, but it would not happen right away—and certainly not every hour and a half.

And Plait gets at the question of whether the Space Station would be moving at a sufficiently different velocity to squash the astronauts like bugs once they reached it.

And objects orbiting the Earth are moving at high velocity, many kilometers per second, to stay in orbit. If you want to get from Point A to Point B you can’t just be at the right place at the right time; you need to match velocities as well. If the two objects are in different orbits, that gets a lot harder.

Most writers gave the film high marks. Only Overbye noted a less than trivial problem:  

It wouldn’t matter so much had the producers not set such a high bar for themselves with their splendid re-creations of small things: the fogging helmets, the space tools. Violations of the known laws of physics happen in practically every frame of a “Star Wars” or “Star Trek” movie, and we don’t care because we don’t expect anything better.

And that’s perfectly reasonable. But these pieces aren’t movie reviews. They’re best read after seeing the film and at that point they serve to add to the fun.  


comments powered by Disqus