• Show Spoilers
• Night Vision

So, when you go back in time.. does the previous timeline keep going, making it semi-pointless, or... do six billion people die?
• Keep going, objective collapse(one world) QM and time travel don't mix, ergo you must be using Many world QM. It's not semi-pointless though, it still affects your perception down that probability pathway.
• This troper thought the movie took the Cloverfield path on that issue. Any of the above could be true, or could be false. Either way, it's not like the protagonists would know. Part of the reason they stop using the time machine is because they could be seriously messing up the world, or themselves and wouldn't even know.
• The time-box reset mechanism guarantees that the return time always advances on every box (the best someone can do on exiting the box is to turn it off immediately and set a timer to turn it back on, so those minutes are lost forever). Therefore Abe should not be fooled for a second when he uses his fail-safe — he could see by a glance at the running timer that Aaron had used it before him.
• This may actually be Fridge Brilliance instead. It shows that the mechanism for "recycling" a box is not by switching it off and on, but by using the same setting and getting out "early" (which means exiting after the other person has left). Abe didn't notice a timer change, or he would have sought out and confronted Aaron instead of going back. The amount of oxygen he took (three tanks of 625 liters each) is consistent with the given breathing rate (.3 liters/minute) and the time shown on the fail-safe box (3 days, 22 hours, 8 minutes), so he will use 2.7 tanks worth of air. If he expected a substantially longer travel time, he would have brought four tanks of air. An engineer would safe-side something as important as air to breathe).
• Told you it was a geeky movie...
• Hmm. I assumed this was a mistake on Abe's part. He's so shaken up by the Granger incident that he doesn't realise that the box should have been running for 4 days rather than 3 days 22 hours. Aaron would have set up his own failsafe box soon after exiting Abe's original one, then set up Abe's dummy failsafe box soon after that. There wouldn't have been much difference in the time - nothing that made a 4th tank of air necessary. Aaron took these 2 boxes back with him, folded up, so there would be no situation where people "share" boxes.
• Near the beginning of the movie, Abe sets up a closed time loop where he comes out of the time machine from the old timeline, then the Abe from the present timeline goes in. Most of the movie takes place after this, which means it isn't ending the Universe.
• The process of getting into (or out of) the box doesn't make sense. Suppose you're about to get into the box. That means there's another "you" already in the box, going backwards. So someone outside watching should see the two of you combine and annihilate. Instead, we see a single person crawling into an empty box.
• That's what the timers were for!
• Presumably the field "leaks" in such cases, preserving local causality.
• It's similar to the classic Schrödinger's cat thought experiment. Whoever is currently in the box is in a state of quantum uncertainty while they are completely separated from the external environment. i.e. they may or may not actually exist at any given point in time to an external viewer. When they again interact with the external world outside of the box, their quantum state collapses because they are now a viewer of their own state as part of the external environment. The way the machines work don't allow their quantum state to collapse from an external perspective into a stable state except at either end of a cycle which is why an external viewer wouldn't see anything inside a box in action. Since everything in QM is based on probability of particle interactions, whatever mechanism causes the boxes to work gives what's inside the box a zero probability of quantum collapse to a viewer outside the internal quantum state. Getting out of the box early (forcing an interaction with the external environment) or having two entangled quantum states at once inside the box (i.e. Granger) leaves the field in an uncertain state for the external viewer as well. Abe collapsed near Granger because they were both in a prolonged state of quantum uncertainty/out of phase quantum state to the rest of the universe - it still wasn't sure whether they existed or not.
• No, sorry, it isn't anything like Schrodinger's Cat. Like the man said, that's what the timers are for. You get in the box, and the timer turns on. The timer turns (on/off) in the past and you get out. And earlier someone (probably you) set the timer. You aren't getting in while the field is active and presumably you aren't getting out while it is either. And what makes you think either that someone could be in 'a prolonged state of quantum uncertainty' (when uncertainty is resolved by observation) or that being so would make one have earbleeds?
• When you get in, the field must still be partly active, otherwise you'd miss the boat and just end up sitting in a box moving forward through time (the machine isn't going to turn itself on; you get in while it's turning off). So at some point you get time-reversed; probably not all at once, because you're not a single particle. For several hours before whenever some part of you got reversed, that part of you is in the box...and, when it first enters, from its point of view that same part of you is trying to leave the box (it sees itself getting into the box, in reverse). Even if your whole self somehow got reversed all at once, you have to deal with the fact that you're entering (from the outside) and leaving (from your POV) the box in the same period of time; either you get duplicated right then and there, or you end up entering and leaving the box forever, or, if you're lucky, the box just spits you back out and finishes turning off. Getting out of the box after time-travelling has similar issues. I don't see a way around these problems, besides teleporting in/out of the box, which they didn't do.
• Okay. I may be wrong but this is the best interpretation I can come up with. According to Einstein's theory of special relativity the space-time continuum exists as 4 base dimensional axes where movement across any given axis for any given variable determines velocity, acceleration etc. Hence although the continuum is basically (basically, people!) invariable, movement across the dimensional axes is relative. Hence movement through the continuum is relative for any given object (or sentient entity, as the case might be). So, when, for example, Aaron initiates the first temporal paradox that impacts upon his original timeline, he is not in fact changing anything relative to him, and for the other him at the same time frame nothing is changed either. You simply have multiple different movements through time-space which are congruent with a determined iteration. Now, if you ascribe to the theory that a temporal paradox can't exist (due to negation of the original timeline), I postulate the theory that if individual A2 impacts the timeline of him/herself as individual A1 (where A1 must become A2 at some undetermined point in time) that results in the deviation of A1 from the path of becoming A2, then A2 would not exist, and, as per the premise, A1 would become variant individual A3 instead. HOWEVER, if A2 does not now exist (as A1 becomes A3 instead of A2), then A2 could not have influenced the original timeline in order for A1 to become A3, and hence A1 would have become A2 instead. The result? You have a projected outcome where both A2 and A3 must exist as per a stable time-loop. Hence you could technically have an infinite number of the same individual A existing in the same time-space continuum simply at different points on the axes (i.e. different co-ordinates in 4-D space-time). The limitation of course is the individual. So each time Abe and Aaron use the boxes they are simply reinforcing a different iteration of the time-line which exists concurrently with the original timeline with both existing in the same space-time continuum. However, it's fair to say that with each congruent iteration and each new paradox, each movement is relative according to the individual. Hence, if we assume that the Aaron narrating is the original, then we can assume that he has observed the entire result of his selves' iterations. Kinda sets it self up as Fridge Brilliance if you think of it that way, "the past is always the future for someone." Anyway, that's what I got.... feel free to correct me if I'm wrong....
• Oh, and just to add on that thing with the timers; relative passage of time per iteration where movement is determined by position in time, not space, as position in space is (relative to the earth) the same. Hence, movement in time is the determinant of movement within 4-D continuum.
• Another note: I mentioned Einstein's theory of special relativity to maintain the local impact. No way in hell am I gonna try to rationalise it with the general theory.
• Please try. You'll be watching porn anyway in the next tab.
• .... -/-........ still not gonna! * sulk*
• The way you explain it (or the way I understand what you're trying to explain) is the same idea as the mechanism used in Robert A. Heinlein's "The Number of the Beast" for moving between universes. They invent a widget that allows them to shift any of the four axes with each other. Shift the X axis with the T axis and move around in time by physically moving back and forth. Starting getting more complex and move forward along X, up along T, over along Y and back down X and you're not just somewhere and somewhere else, but in a different universe entirely. (The problem with this in reality is that there is no "T axis." It was just a metaphor Einstein used to describe how time can be thought of as another measurable property of the universe.)
• Unfortunately, we have to presume that our current hypothetical model of the universe is correct until either pure or applied maths and physics advance to come up with something new to explain the current phenomena better. Let's face it, we're all making up hypothesis to fit how we view the universe, that currently works. Until something comes up to disprove it, we have to go with what we've got (which is really stuff someone else made up to explain what they saw, or discovered, or observed, about reality). Two thousand years ago, humans saw the earth as flat because according to immediate visual perception, it was. However, that hypothesis was proved wrong, because we found out the earth is spherical. Whose to say our current model won't be as equally absurd to humans in another two millennia? According to M-theory the universe apparently has 11 dimensions. However, we can only account for 3 in physical space, because all dimensions must be at right angles to each other and our limited senses can only detect length, depth and height. We hypothesize that time must exist because to us memories exist of previous moments. However, we cannot actually verify those memories from an in-universe perspective. Time may or may not exist. So the hypothesis that time is a measurable variable may or may not be valid. However if it is measurable, then we are moving through it at an alternate dimension to those physically observable to us. If Time is a changing variable, an axis on which it travels must exist. Hence according to the objective reality that humans apparently share, there must be a fourth dimension. Exactly where it fits into an extrapolated exponent dimension model is something I can't comment on. Mostly 'cause I'm really not caught up on the math... The more lack of proof there is, or the more countering proof there is, the more unlikely a hypothesis becomes, but you can't really provide a negative proof. No one's seen little blue aliens from andromeda but that doesn't mean they don't exist. Time seems to be measurable currently, and they're aren't really that many contraindications, so I'm sticking with the "4 basic dimensions" theory. Okay, I went on a bit of a ramble there (I have a terrible tendency to do that). My point was... oh right: reality may or may not be real, but according to what we subjectively know/understand/think to be real, time as another dimension is the most likely hypothesis. That said, insanity is pretty much by definition a perception of reality deviating from an objective consensus, so if you walk up to a psychiatrist and say that there are little blue aliens from Andromeda and that their tinkering in world affairs is most likely going to bring about World War Three, they may give you a shot of thorazine and stick you in a padded cell. So let's all just pretend they're not listening in, ok?
• I've read Carruth saying that he made Primer follow the real laws of physics as closely as possible while still allowing for the time travel. I was on board with this until it got to the point where you have several copies or Aaron running around as result of the time travel. Wouldn't this be a major violation of the First Law of Thermodynamics: The total energy contained in an isolated system can not increase or decrease. So how did the energy (in form of mass) for the extra Aarons poof into existence?
• Well, Aaron does kill his doubles, and doesn't seem like he has any problem doing so, so he probably does it many, many times. So with each Aaron he manages to snuff out, that's at least that much energy not being physically displaced by moving around. But, because bodies take up mass, even dead ones, the energy going into decomposing and taking up space is drawing away from !aliveAaron. And that may explain the earbleeds, the handwriting, and the degrading personality. I admit my explaination is kinda weak. But at some point you just have to "repeat to yourself it's just a show, I should really just relax..." :)
• At no point does Aaron kill anyone, much less himself. A1 (Hooded Aaron) arrives in the failsafe early Monday morning, drugs A0 and hides him in the attic. He then records everything until he encounters A2, who is exhausted from extensive time travel. A2 tries to subdue him but can't; this doesn't matter because A1 understands what he is trying to do and agrees to leave forever and let A2 fix the incident at the party. A0 wakes up a day later from his perspective, probably very perplexed at why he was drugged, and goes on to attempt to build a time machine, which is interfered with in secret by Abe 1 so the current "real" pair of friends never get themselves in this mess. A2 fixes the incident at the party on monday night while A0 is still drugged, and leaves tuesday morning at the airport forever.
• Hypothetical: Looking at things from the perspective of someone who isn't Aaron or Abe. When Abe goes into his failsafe to go back a week into the past, what does it look like to anyone else? They see a man go into a box and disappear. Then what. Does he just disappear forever? Or are your memories rewritten to accommodate whatever the guy who went to the past did?