Newton’s laws of motion:
- First law: When viewed in an inertial reference frame, an object either is at rest or moves at a constant velocity, unless acted upon by an external force.
- Second law: The acceleration of a body is directly proportional to, and in the same direction as, the net force acting on the body, and inversely proportional to its mass. Thus, F = ma, where F is the net force acting on the object, m is the mass of the object and a is the acceleration of the object.
- Third law: When one body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude and opposite in direction to that of the first body.
Gravity is the most realistic movie about space and space travel ever. All the romantic notions of smooth flight, with astronauts just hopping outside ships to fix this or that, are thrown out. Remember the movie Armageddon, where Bruce Willis flies his shuttle in space like a commercial jetliner, banking when it makes curves? Utter nonsense. Space has no air, so there is no sound, other than that of your own breathing, your own heartbeat, or the amplified vibrations of bodies you are attached to or are holding on to.
Gravity was directed by Mexican director Alfonso Cuaron (Y Tu Mamá También and the Harry Potter series). The two only actors are Oscar winners Sandra Bullock and George Clooney.
Dr. Ryan Stone (Sandra Bullock) is a medical engineer on her first shuttle mission. The shuttle has docked to the Hubble Space Telescope for a repair mission conducted mostly by Stone. Veteran astronaut Matt Kowalsky (George Clooney) is testing a jet pack by flying it in circles around the shuttle and the Hubble, jovially chatting while doing space acrobatics.
Everything is going well and according to plan, until mission control announces that the Russians blew up one of their own satellites, causing a cloud of space debris. Nothing to worry about. Until disaster strikes. Suddenly the two humans inside their space suits find themselves utterly alone.
Being a space nut and science fiction fan, I enjoyed every second of this one hour and 31 minute movie. Seeing the immensity of space as the shuttle drifts upside down 600 kilometers above the earth, nothing but a tiny spec in the vastness of space. There is no up and down in space. At one point I spotted the constellation or Orion behind and below Kowalski, as he floated upside down.
If a body without a propulsion system is untethered and has momentum away from the station, there is no way to get back. If a body tumbles, there is no way to stop the tumbling. The surrounding just endlessly spins around the body. If one body approaches another body at a reasonable velocity, the momentum can be huge and the impact can be extremely violent. Two bodies tethered to each other just make the tether snap constantly, jarring both. And if the two tethered bodies spin about each other, there is nothing to stop that either, until the tether snags on something else.
I enjoyed seeing how small an astronaut is outside the International Space Station, a three-dimensional construct the size of the inside of a football stadium. Whenever the astronauts move about, their bodies keep spinning from their own mass and momentum, and every grab for a handhold is critical and every spin or slip can be fatal, either by missing and drifting away, or by puncturing a suit or helmet.
Understanding physics and the basic concepts of orbital dynamics, I loved seeing the reality of space travel unfold realistically in front of me. Anyone who does not understand those concepts, or is not as informed about the current state of space technology, might miss some of the details, but will still enjoy this cliffhanger.
I think I need to go and see this again, this time for the imagery alone.
Read only after seeing the movie!
This movie quenched my hunger for realistic portrayal of space travel with the current state of technology. But there were a number of things necessary for a realistic plot that didn’t make much sense. These didn’t distract me enough from the movie to get in the way, but I can’t help but mention them here.
The fact that the Russians for some reason blew up one of their own communications satellite seemed odd. At first it was in an orbit that would not harm the space shuttle at 600 kilometer altitude, docked to the Hubble Space Telescope. But then all of a sudden, they announced that all communications satellites were wiped out and that a debris field was approaching the shuttle. Obviously, the debris field must have been at the same orbital plane, but crossing the orbit of the shuttle/Hubble somehow.
Then, after disaster had hit, the solution was for the tethered survivors to hop over to the International Space Station, which was just a few miles away, visible as a bright spot in the neighborhood. Obviously, this implies that the International Space Station and the Hubble Space Telescope are in identical, matched orbits within a few miles from each other, close enough for two tethered astronauts with minutes of oxygen left to cross the gap.
Furthermore, when they find the Soyuz lifeboat with the parachute deployed and must conclude that they can’t use it to deorbit, they decide to make their way to the Chinese Space Station, which is, surprisingly, only about 100 kilometers away, another bright spot, apparently also in an orbit perfectly matched with the International Space Station.
I also found it hard to swallow when Stone flew the Soyuz, which was out of fuel, by using the landing jets, to make to the Chinese station. The craft had just luckily been oriented so the vector of the landing jets pointed directly at the Chinese station. Then Stone was able to cross over using a fire extinguisher as her mobile jetpack, decelerating her enough to match velocities with the Chinese station. Oh my.
Matt didn’t have to die. He was safely tethered to Ryan, and holding her hand, and Ryan was attached to the station via her leg wrapped around a parachute strap. They were stable. The slightest tug would have drifted Matt back toward the station, along with her.
The shuttle with the Hubble, the ISS and the Chinese Space station, all three are in the same orbital school yard, reachable on foot, so to say. But that’s ok, because it was necessary for the plot to work. The imagery and the portrayal of the concepts all make up for it.
For much more “Bad Astronomy” – here is a great blog post by Phil Plait which supports my criticism but also my premise that you have to go see this movie. Phil is just much more scientific and precise.