Either I have not understood this film or it is full of paradoxes.

The Source Code allows its user to experience the last eight minutes of another compatible person's life within an alternative timeline. That part is not hard to understand.

The bomb explodes in the Chicago train and kills everyone on board. Through the Source Code's alternative timeline, Colter Stevens is made to experience the last eight minutes of a passenger on the train so that Stevens could identify the bomber who is supposed to be on the same train. But in the end, Stevens is said to have averted the bomb explosion in the alternative timeline, effectively modifying the history. That part is creating some confusion.

Does Colter Stevens really manage to avert the bomb explosion on the Chicago train? If so, why was Captain Goodwin trying to get Stevens to find the bomber after the explosion? And how could the explosion be averted? (Not possible even from a 'fictional' point of view, unless we say that the Source Code program allows its user to travel back in time, which is actually not the case)

Edit: Removed update

  • Similar question to M&Tv movies.stackexchange.com/questions/1909/ending-of-source-code Feb 12, 2013 at 15:37
  • 3
    I think this is one of those times where it's okay to have two similar questions on different sites because they address different concepts
    – user11295
    Feb 12, 2013 at 16:12
  • 7
    I should point out that even within the movie there is confusion over how the Source Code works; the way that Colter thinks it works is fundamentally different from how its creator and operators claim it works, so the confusion is intentional.
    – KutuluMike
    Feb 12, 2013 at 16:38
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    The questions may be slightly different, but I think my answer over at movies.se covvers both.
    – magnattic
    Feb 12, 2013 at 17:09
  • Your update should be a new question, not added onto this one.
    – phantom42
    Feb 13, 2013 at 5:18

6 Answers 6


There is plenty of room for confusion in this movie, particularly for folks who are not familiar with the different theories and mechanics of time travel, as portrayed in various science fiction stories.

The theory of time travel, as used in this movie, and in other places such as the TV series Time Trax from 1993, holds that traveling back in time is actually impossible. What is possible, and what is shown in this movie, is travel to a parallel dimension that is identical to your home dimension, except for being time delayed by some value.

There are an infinite number of these parallel dimensions, each with slightly different delays. This allows the protagonist from the movie to repeatedly travel back in multiple attempts to determine what happened in his home timeline. Note that in the universes he travels to, the events have not yet unfolded and so he does not actually change history, but rather his actions cause a time-line split.

So, in a way, you are correct, he does not actually time travel. However the bottom line answer to your question is that, no, there are no paradoxes. The parallel-universe with offset and splitting time-line style multiverse makes paradoxes impossible./

  • The first three answers have been good enough, each qualifying for the best answer slot. It's just that I decided to go with Donalad McLean's. Thanks all!
    – Elzee
    Feb 14, 2013 at 16:23

My understanding is that the bomb has exploded in the main timeline and nothing Stevens can do changes that. They just want to know who planted it. They don't care if he prevents the explosion because it's just in the Source Code generated reality anyway.

However then the film seems to claim that the alternative realities created actually exist and continue for ever. This is the multi-worlds theory of parallel universes and I suppose it implies that the Source Code device is more tapping into alternate realities rather than creating them. Pretty bad luck for the teacher whose life he just took over.

  • What would be neat would be if we were to have discovered that the teacher was experiencing extreme schizophrenic episodes the last few years of his life.
    – John O
    Feb 12, 2013 at 15:14
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    @JohnO Well, maybe that's why the teacher is compatible :)
    – Tacroy
    Feb 12, 2013 at 16:44
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    "Pretty bad luck for the teacher whose life he just took over." - Well, to be fair: He would be "dead" either way.
    – magnattic
    Feb 12, 2013 at 17:05
  • I believe this is the case. The bomb has exploded in Stevens' original timeline, but the perpetrator is still out there. The government believes that there will be a second bomb, so they need Stevens to find out who set the first.
    – Steam
    Feb 13, 2013 at 14:11

We have two timelines in the source code to work with. One in which the train bomb went off and another where the train bomb was defused.

The Bomb Goes Boom

This timeline goes bomb blows up train, military secret project is activated, bomber is found before he manages to blow up Chicago. Goodwin kills Stevens body while his consciousness is absent.

The Bomb Doesn't Go Boom

In this timeline, some dude on a train finds and disarms the bomb, locates the person responsible and handcuffs him for the authorities. No military is involved.

What Does It All Mean

That the Source Code is actually allowing body swap time travel. However, instead of being able to change the future, any changes result in a new timeline being spun off. That new timeline only lasts as long as the person sent back does (Maybe. There isn't really enough info in the movie to make that call). We know that because every time Stevens is sent back, he starts at the same spot in the timeline. The timeline also continues until his death, as it is death that causes him to wake up back in the "present". We know that because the one time he doesn't die the timeline continues. It could alternately be that your consciousness gets sucked back to your body after eight minutes, as Goodwin does kill Stevens right on the line, but the other way works better for me.

So the basic model of the time travel is a consciousness is sent back into a compatible host, wiping out the original consciousness. Any changes to the timeline result in a new timeline, although information transfer to the present doesn't count as a change. Since we are following the protagonist, we are inhabiting his POV of the timelines, seeing both until he is separated from timeline one by the death of his body. At that point, he remembers the events of the first timeline, but those events never actually happened in the timeline he now inhabits. He then makes arraignments for the other version of himself that is already in this timeline to also be able to escape into a new timeline.


If you follow the theory that these alternate timelines are created by the action of sending Colter into the train, then the Source Code project is responsible for the deaths of a lot of people - at least every person on the train (if the timeline is stopped at Colter's death) but possibly every person in Chicago... although each of those timelines might create it's own Source Code project to save the city, spawning many more timelines, which create Source Codes, which create...


One big paradox, if Colter can only enter the minds of dead people for eight minutes, then preventing them dying means he can't get there to do it.


Long version: (if you're bored or you don't have time look down for the short version)

I was wondering the same thing.. are there any paradoxes... the paradox i thought was in the movie.. is that the captain has to be sent on a mission (it says so at the end of the movie) but didn't he already go on a mission and safe himself + all others... well.. no.. he took over the life of a teacher.. he is the teacher now.. but he still has his own mind and memories... so basically he stole the teachers soul and entered his soul into the teachers body... and from there he dailed the number from Goodwin... but not the goodwin we see at first.. the alternative source code Goodwin.. she has the Alternative Code Source Captain Stevens still in the komora (or whatever that thing is) and he told her that her and him already saved one attack.. but that was the real world Goodwin and Captain Stevens.. Captain stevens is dead in the main world.. but his mind transfered into the pararell alternative universe.. and he lives his days as the teacher... where as alternative universe stevens is going on a mission (not the same one but probablly a similar one) and that will maybe make another parrarel universe.. so Tehnically there is a potential PARADOX

Short version:

-Main world Captain Stevens Died (his body) -Main world Captain Stevenses Mind got transfered to the Alternative universe made by source code (into the teachers body) -Main world Captain Stevens lives his days as the teacher... -Main world Captain Stevens (while in the alternative universe) sent Aleternative World Goodwin a message that he and her(main world Goodwin) saved the day already once.. and that she should go easy on him (alternative world Captain Stevens) and tell him that everything is going to be okey -Alternative world Captain Stevens still has to go on a mission (won't be the same mission but it will be a similar one maybe there will be another girl for the alternative version Captain Stevens and that Could lead him making another alternative version of himself)


-So if the alternative World Captain Stevens makes another Alternative version of himself.. by rescuing some other ppl with some other girl on some other terrorist attack.. that would mean the alternative version of alternative world Captain Stevens could make another alternative version of himself so we are tehnically looking at a very possible Paradox!

  • Could you clarify this?
    – Adamant
    Jul 26, 2016 at 6:48
  • This is incredibly difficult to read. Jul 26, 2016 at 6:55

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