Saturday, February 19, 2011

Deja Vu

I've recently realized a symmetry regarding the nature of time. It is illustrated in the graph shown at left. Under normal circumstances, you and I travel forward in time. Our relationship with the future is not that we know it, but that we move into it, we experience it. On the other hand, our relationship with the past is the reverse of this. We see the past through the eyes of our memory. We know it, but we cannot move into it. The paradoxes of time arise when you try to reverse either of these relationships. If you try to move into the past, you end up creating alternate histories that cannot co-exist with each other. I in fact wrote about the impossibility of backward time travel at length in a previous entry. Likewise, another type of paradox arises if we try to see into the future. Once you know what is to come, you then have the power to prevent what you have seen. This, of course, is less paradoxical than trying to change history. If the future you see does not come to pass, you can always argue that what you saw was never really the future in the first place. But the main point I'm making is that there are philosophical paradoxes associated with traveling into the past and seeing into the future, but there is no paradox associated with traveling into the future or seeing into the past.

Now the real insight for me came when I realized that the non-paradoxical scenarios could be stretched and extended and still remain non-paradoxical. Traveling into the future at a faster rate than everyone else is accepted by physicists as perfectly possible... if you are near a black hole or traveling near the speed of light. It may be a nearly impossible feat to actually accomplish, but theoretically achievable. Similarly, you can collect all the information you wish about the past without running into any sort of philosophical conundrum. The idea of seeing into the past never caught my attention as did the idea of traveling into the future because it seemed so ordinary by comparison. All you have to do to see into the past is spend lots of time in a library. With the help of video and audio recording you can experience the past as if you were actually there. But this whole attitude was turned on its head when I first saw the film Deja Vu. Ok, I know that's an awfully winded introduction for a movie review, but I had to describe all this before getting to the point because I don't think this film gets enough credit for the concept that it's writers so crisply and cleanly introduced to moviegoers. I think it deserves a little respect, and with that, on to the film...

The plot line of this film is quite simple. A ferry in New Orleans carrying over 500 Navy sailors, friends, and families explodes and kills all on board. Denzel Washington plays an ATF agent named Doug Carlin who is sent to investigate the accident. When it is discovered to be the work of a domestic terrorist, the FBI gets involved and, noticing Carlin's keen detective instincts, recruits him to join the investigation. Most of what follows is your basic who-done-it crime drama, with one interesting twist.
The FBI, it turns out, is using the case to test a new technological gadget. It is actually an area wide system connected to remote satellites that allows them to obtain detailed and close-up real time monitoring of any location within a certain radius. That doesn't sound too far from today's satellite technology, except that they are able to use it to monitor such locations at a different point in time, one that is about 4 days in the past. It is a type of time window, but they say they have no way to change the time range of the window. They can record what they focus in on, but they cannot move the window backward or forward in time, and it is video only. It is like being able to watch what happened 4 days ago as it evolves. It is impossible to view every location at once, so they must try to focus on what is important to the investigation. This is where Carlin's help comes in handy.

You might ask yourself, why not record everything and then sort through it after the fact? It is not a stretch for me to believe that the amount of data required for such a feat would be too huge to manage. Even if you could find enough storage capacity to hold all the information, it would be impossible to beam it to one location, whether direct or by satellite, at any usable rate. There is only so much bandwidth available and that restriction is based on the laws of physics. No, it makes sense that one would need to focus on specific locations at a time. Focusing technology does not suffer from such physical limitations. Why they can only see a fixed time period in the past is never explained, and of course is completely arbitrary, but it makes for an exciting detective story. Remember, they only have 4 days worth of history leading up to the crime that they can work with.

=================< spoilers below >=========================

Carlin focuses on one of the victims, a woman named Claire, who is discovered to have been killed before the accident and therefore might have come in contact with the assassin prior to it. If you like detective stories, there's a lot of good material here, but its more than just CSI style puzzle work. The writers really delved into the real time aspect of this time window system. One of my favorite scenes is a type of car chase. In the time window, the terrorist is driving the woman to his hideout outside the city, which is supposedly out of range of the FBI's system. They have an extender device in the form of a helmet with a visor that shows what is happening at your current location 4 days ago. Carlin decides to try to "follow" the suspect by driving the freeways with this helmut on. In the harrowing chase that follows, we see from the detective's viewpoint. One part of the screen shows the suspect's car that Carlin is trying to follow from 4 days ago, and the other part shows the current traffic in the windshield in front of him. The traffic patterns in both windows are completely different, making it a delightfully unnerving sequence to watch as Carlin tries to dodge the real cars, ignore the imaginary ones, and still keep the suspect's car in his viewer. There is one point where the cars stop and it appears like the killer is looking straight at Carlin even though that is really just coincidence. Nice touch. In fact, you can watch most of that chase sequence here from 1:16 to 1:20.

As I mentioned, this whole system is free of paradoxes. But the writers decided to challenge themselves a bit more and allow objects to be sent back into the time window. There are only two instances of this in the film. The first involves sending a piece of paper to the desk of Carlin's partner telling him where to find the suspect. This ends up getting his partner killed, something that was already known to have happened but no one knew why. The detective blames himself. Once they catch the criminal, the second incident involves Carlin convincing the team to send him back so he can save Claire, whom he has begun to care about. They send him to a nearby hospital bed with the words "REVIVE ME" written in large letters on his chest. Very clever. Carlin ends up not only saving Claire but also preventing the entire incident from occurring. What is really neat is that here again, the writers have shown us everything that Carlin's time travel affected at earlier points in the movie. As he intervenes in the time line, you see and understand the reasons why everything was this way or that way when you saw it before, including messages he wrote to himself. In other words, we only ever saw one time line to begin with, except for the very beginning when the boat actually explodes. In the changed timeline, the boat is saved.

Personally, I consider it a really well crafted script. Not only does it keep track of the clues to the crime, it also keeps tabs on the alternate time loop so as to minimize the paradox effect. The only detail to tie up is the fact that two Doug Carlin's exist at the same time now. This is neatly handled by causing Carlin to heroically save the ship at the expense of his own life, leaving his alternate future self to meet Claire under more favorable circumstances, and leaving her as the only one knowing all that actually happened. The film did not do very well at the box office, so maybe there aren't as many people out there who appreciate a good puzzle as much as I do.

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