Ethics? Really? Time doesn't need ethics any more than the Voyager 1 spacecraft needs a burrito.
There are no ethics of time travel, beyond what sentient beings choose to place upon it. I imagine that if any individual ever got close to discovering time travel prematurely, people from the future would approach them in the past and place their own self-centered rules and restrictions. Far more likely though, time travelers from the future would seek to protect their own historical records, for fear that deviations of their past may erase their own future, placing someone else in power for example, or wiping out their race. If that guy was meant to figure out time travel, messing with his present could destroy their past, so it would be in the best interests of anyone not to travel into their own past for fear that it might upset their own present. If there is only time time line, that is a valid concern.
I happen to accept currently the Many Worlds Theory of Quantum Mechanics, until I see sufficient evidence otherwise. However, the writers of LOST don't seem to be falling on that overused hack answer for time travel in fiction which is to their credit. The story becomes much more interesting if there's only one time line.
In the movie Back To The Future 2, Biff goes back in time and (among other things) kills Marty's father, thus building an empire for himself that ruins Marty's future. However, when old Biff went back to young Biff and gave him the sports statistics so he could bet on the winners, he didn't erase the previous timeline. He also didn't invent a new timeline. He committed actions that were always meant to happen that were always meant to fulfill that timeline. This sounds like predetermination I know but it's not. Because Old Biff was the kinda guy who would do such a thing, there's a probable chance that he would. There's also a probable chance he wouldn't. So BOTH of those realities exist, as well as an infinite number of others. We just didn't see those other realities cuz they're not the ones to which the DeLorean took 'our' Marty McFly. Notice that in Rich Biff's time period there was another Marty McFly who was in another country. This is a fun storyline, but it's chock full of paradoxes and impossibilities, if followed to its natural conclusions.
In the LOST universe, we've been given every indication that there is only one time line. Whatever Happened Happened. Dead Is Dead. The producers and writers of LOST are not playing with paradoxes. They're saying there is no paradox, or rather if there is, it's only one, and it's a biggie, and it's what will get resolved at the end of season six for better or for worse. What I'm hoping though is that the use of time as a plot device is behind them, and as we start season six they'll make it very clear that Whatever Happened Happened, and they'll move forward. I understand many fans speculate that what we've seen are actually multiple time lines. However, the writers have gone out of their way to keep everything on as linear a line as is possible in episodic storytelling that involves seemingly sporadic and arbitrary temporal hopping. This goes against my own personal "beliefs" (for lack of a better word) about how time would work, but I'm not writing LOST.
Time is like a river. Metaphorically, time starts at the top of a mountain as a raincloud. It falls down the mountain first as a trickle then a stream and then a river. At times it collects in pockets like ponds or lakes. At other intervals it may fall quickly like down a waterfall or surging through river rapids. Sometimes it'll be in the form of a small creek and at other times the creeks merge together into larger streams or rivers, and sometimes those rivers branch off into smaller tributaries and this can go on and on until finally it reaches the ocean. Of course that is sort of where the metaphor breaks down, because water in the ocean can then be collected up into the atmosphere once again as rain clouds and the whole process repeats itself. Many fans of LOST think that is exactly what's going on: that these characters are caught in a loop and while UnLocke finds this a futile endeavor, Jacob feels that repeating their little game will eventually lead to progress - a different result. Any psychiatrist will tell you: repeating the same actions over and over, anticipating a different result, is a sign of madness. I'm not convinced Jacob is the good guy here.
Unlocke (aka Blackie or Nemesis) & Jacob have been doing dance of theirs this since at least the ancient Egyptians. Perhaps even before that but the producers haven't shown us anything older than that four toed statue. If we are to accept the conversation between Unlocke & Jacob at the start of S5's finale at face value, every time they've repeated their little game, Unlocke's prediction has come true. So Jacob has "lost" to Unlocke thru ancient Egypt, the time of The Black Rock (which I believe to be Richard's time) and on and on up until our present day.
So Unlocke & Jacob have stuck themselves in a loop, but linear time continues to keep on slippin slippin slippin into the future. Unlocke is trying to stop Jacob from changing what he believes to be the acceptable result. Jacob wants something to change. It appears that it's humanity's faults and short-sighted selfishness that is the hinge of this change. Unlocke believes their pawns are lemmings that will continue to make the same kinds of mistakes. Jacob is either aspiring for something better, or more likely he's going for something worse, because based on the lowly 3D restricted humans chosen to be their pawns, Jacob's not trying to cultivate piety and perfection and excellence. He's tilling the soil of humanity hoping to grow some weeds.
They each seem to have some control over life & death, time & space. However, they each can only cause one effect as they traverse through, and can't go back to undo what they've done or undo what the other has already committed. These are their rules of the game.
We don't know why Jacob visited Kate, Sawyer, Jack, Hurley, and perhaps even others in our Losties' pasts, and we may assume he did this by traveling back in time from some point near current present (say Sept 2004 after the crash). We may also assume he met them in his linear travel through time, either by happenstance or because he knew their fates were sealed, or a third possibility that he was altering their fates so that they would better assist his future.
We still don't know to what end, and that may not be made fully clear until the very last hour of the very last show. I don't question the ethics of time travel when it comes to Blackie & Jacob because I'm not yet convinced they're able to do so at the drop of a hat. The temporal distortions we witnessed in season five did not appear to be as a direct result of either Jacob or Blackie's actions. They knew about them. They're not surprised. Jacob could sense their impending return from the past as he lay 'dying'.
No matter how many tributaries meander about the surface of the planet Earth, all water eventually finds its way out to sea. Man can build a dam, but that only holds back the inevitable. Years, decades, centuries from a dam being built, it will fall, or the river will simply reroute itself making the dam irrelevant.
As Mrs. Hawking is fond of saying: Time has a way of course correcting.
You Broke Me A Little Bit
3 years ago