SPOILER ALERT for the film Source Code, the Many Worlds hypothesis of quantum mechanics, and fiction by Dalton Trumbo and Ambrose Bierce. Bet you wanna read this now, dontcha?
Colter Stevens is living proof. A living proof of several things, actually, when you really take apart Duncan Jones' film Source Code (2011, scr: Ben Ripley) and the protagonist's place in it. In proving these concepts, he inhabits several contradictory states at once. He has the freedom to go anywhere, yet he will never leave his prison.
Stevens (Jake Gyllenhaal) awakens, shorn of memory, in metal pod of some kind. From here, he's repeatedly plunged back in time to inhabit the body of another man. He is told little by his remote handler Goodwin (Vera Farmiga), except that his consciousness is being hurled into an eight-minute window before a terrorist bomb destroys a Chicago-bound commuter train — a train that was, in his current reality, destroyed that same morning. He dies in the effort to prevent the blast, repeatedly, and each time is yanked back to his pod to try again.
No one will miss him. Reported KIA in a helicopter sortie over Afghanistan, Stevens is in fact a limbless lump of flesh in a sealed box, his internal organs held in place by a plastic sheath. His pod, emulating a pilot's cockpit, is just his psychological projection of space. His last glimmer of consciousness — call it his soul — is a tool in a project to change the recent past. In his box, unseen by the world, Colter Stevens is simultaneously alive and dead.
In his original thought experiment, Schrödinger imagined that a cat is locked in a box, along with a radioactive atom that is connected to a vial containing a deadly poison. If the atom decays, it causes the vial to smash and the cat to be killed. When the box is closed we do not know if the atom has decayed or not, which means that it can be in both the decayed state and the non-decayed state at the same time. Therefore, the cat is both dead and alive at the same time — which clearly does not happen in classical physics.
For injection into the past, Stevens' preserved psyche is wrapped into a spacetime field called the Source Code. The informational set that comprises his personality is shot back to the moments before the train's destruction. Essentially, he becomes a packet of data, overwriting the brain (soul?) of rail passenger Sean Fentress, who's doomed to die in the bombing.
In programming terms, "source code" is the raw commands for a piece of software, written in text language. Change any character of the text and you change the operation of the software. (Indeed, Goodwin sees Stevens' responses to her commands entirely as text on a screen.) The Source Code project is, in essence, rewriting informational space to put Colter Stevens in another man's body, several hours ago.
Space is the set of dimensions that allows motion to take place, but it also stores information via its configuration. ... Space that has information stored in it has some entropy. Since there is more information stored in some parts of space — for instance, in highly curved parts of space — then the entropy is not uniform. ... Looking specifically at a black hole, space is curved sharply around it — so sharply that, from the inside, it is closed off from the rest of the universe. As objects fall into the black hole, the event horizon expands (this is the spherical surface that, from the inside, is perceived as a closed surface). That sphere now has more surface area, and so can accommodate more information, all of which remains on the surface of the object.
In the transitions from his box to his hijacked body, Stevens frequently glimpses a huge, curved, reflective surface, gleaming in the sun like an alien craft. Its presence echos the General Relativity notion of spacetime, through which Stevens is whiplashing back and forth, as a curvature. It also reminds one of the "magic mirror" frequently encountered in Grant Morrison's graphic novel series The Invisibles — the physical manifestation of spacetime, through which enlightened operatives may travel or observe other points in their various continua.
Stevens is deeply cut off from the material world and his own physical self, relying on Goodwin's input to make sense of what's happening to him. As they work together — over the course of a single day — Goodwin grows more sympathetic to her subject's plight, becoming the only person in the Source Code program to treat Stevens as a human being, rather than an experiment or an implement. Maimed and only debatably alive, he can only act in the material here-and-now, and can only understand what he's become, through surreal interactions with his caregivers.
The door of the room jarred open and the nurse's footsteps came up to the bed. He began to tap out more frantically now. Here he was right on the brink of finding people of finding the world of finding a big part of life itself. Tap tap tap. He was waiting for her tap tap tap in response. A tap against his forehead or his chest. Even if she didn't know the code she could tap just to let him know she understood what he was doing. Then she could rush away for someone who could help her get what he was saying. SOS. SOS. SOS. Help. He felt the nurse standing there looking down at him trying to figure out what he was doing. The mere possibility that she didn't understand after all he had gone through before discovering it himself shocked him into such excitement and fear that he began to grunt again. He lay grunting and tapping grunting and tapping until the muscles in the back of his neck ached until his head ached until he felt that his chest would burst from his eagerness to shout out to explain to her what he was trying to do. And still he felt her standing motionless beside his bed looking down and wondering.
— Dalton Trumbo, Johnny Got His Gun (1939)
Because Stevens and Sean Fentress are essentially frozen in the moments before death — and because the Source Code intervention creates a potential for something like survival for both — another text rises to mind.
He stands at the gate of his own home. All is as he left it, and all bright and beautiful in the morning sunshine. He must have traveled the entire night. As he pushes open the gate and passes up the wide white walk, he sees a flutter of female garments; his wife, looking fresh and cool and sweet, steps down from the veranda to meet him. At the bottom of the steps she stands waiting, with a smile of ineffable joy, an attitude of matchless grace and dignity. Ah, how beautiful she is! He springs forward with extended arms.
— Ambrose Bierce, "An Occurrence At Owl Creek Bridge"
These trapped protagonists all spend time in alternate realities, whether psychological/spiritual in the case of Trumbo and Bierce's work, or (we are led to believe) physical in Stevens' misadventures. They are experiencing dimensions in which other ends are possible; Stevens is, in fact, creating those new dimensions by his actions on the train. In a dramatic sense, he is enacting Hugh Everett's Many Worlds Interpretation of quantum physics, in which subatomic behaviors are explained by parceling them out to parallel universes.
... The upshot of the Many Worlds theory is that this universal wave function describes a series of branching universes that make up what [physicist] David Deutsch calls the "multiverse," and that in these branching universes, there are beyond trillions of copies of you, of me, of Everett. There are branches in which Everett is still alive. There are branches in which we did things that we don't want to talk about, that we may have thought about but we never did. Well, guess what? I'm sorry to tell you, in Everett's theory, you actually did it, because everything that is physically possible happens in some branch of the multiverse.
None of this can be realized, though, so long as Stevens exists in a state of improbability — shut away, channeled, the truth of him unconfronted. Like Schrödinger's cat, Stevens' condition is only theoretical. Like the cat, his condition inspires compassion. Goodwin, the observer of these quantum events, is the determinant for whether Colter Stevens is alive or dead, and whether he will live or die again. She is the one who must open the box, if his unbearable half-life is to end.
The crucial plot questions of Source Code are teased apart at length — and diagrammed! — in an excellent piece by Brad Brevet at Rope of Silicon, published the week of the film's release.
(Cross-posted from Soul Smithy.)