I just finished viewing Duncan Jones’s second movie, SOURCE CODE. Stop reading now if you don’t want spoilers.
Overall: enjoyable movie that posits the reality of Many Worlds QM. What I find myself most struck by leaving the theater, though, is that at the end of the movie there is a reality in which Colter Stevens has, essentially, murdered Sean Fentress and stolen his body. This is the happy ending; Stevens gets to live on in a new body with a pretty girl. But it’s hard to really be happy about it given that that body was in use by someone else. Are we to think that by saving so many people, Stevens somehow earns Fentress’s death? That would be a difficult argument for me to accept.
Also, since at the end of the movie there is a reality where there are two consciousnesses that think they are Colter Stevens, it stands to reason that the next time Source Code is used, there will be three. Then four. Then five. The identity Coulter Stevens becomes a trans-universal memetic virus taking over human body after human body. There are a few possibilities here. (1) The process continues until there are eventually whole relaties populated mostly by Coulter Stevenses, none of them knowing that they are all, on the inside, the same person. Or (2) the need to find a body with a close enough biological match means that there are a finite number of Stevens-habitable corpuses walking around, in which case once all of them are used up he starts overwriting himself. Here some subset of male humanity is Stevens-infected, but after that the disease is stopped.
Of course, in every reality where Source Code is proven to work, the program gets expanded to include women, different body types, etc. so that there will be the greatest possible room to work in the event of another disaster. As the number of people proliferates, so do the number of trans-universal memetic identity viruses. Eventually there are whole realities where most human beings share one of, say, 25 different personalities. And eventually some of them would have to discover that they all have memories of being part of Source Code. At which point Source Code is no longer top secret. The possibilities are known, and it become explicitly what it has always been implicitly: a tool of inter-reality war.