In the movie Looper, we are shown a scene where Bruce Willis is transported back in time with a bag over his head and gets shot. His younger version lives out his life to right before he is sent back and somehow escapes.
How does he escape the 2nd time? In general, how do things change? There isn't any knowledge that he knew or anything different than the first time he went back (and died) that we are shown to explain how he can escape this time but didn't escape the time before.
SPOILER ALERT DISCLAIMER: This answer contains spoilers to the movie Looper.
Definitions and assumptions
In order to make the answer more readable, let's first declare that:
Younger = the one that lives in the present.
Older = the one that came from 30 years later in the future to the present.
There are in fact two Younger persons: First Younger is the one who shoots the Older with the bag on his head (I will refer to this Older as the First Older). Second Younger is the one whom First Younger, when he becomes Second Older, meets when he goes back to the past, without the bag on his head, and meets the Second Younger.
There are some assumptions that are to be made in order to feel good with the suggested answer below:
Younger to Older: in other words, whatever happens to a character, remains in his mind 30 years later.(1)Older to Younger: in other words, whatever happens to Older in the future, Younger will know nothing about it, unless Older will tell him this.Younger commits, Older may be affected by them, but as long as these changes are reversible, they exist as a possibility, and do not yet change Older.(2)The answer
When First Younger meets the First Older, First Younger hasn't already lived his life 30 years in the future, and therefore, he has no real knowledge that his loop is going to be closed (although he does suspect this may happen sooner or later, since many of his fellow loopers had their loops closed lately). Then, he kills the First Older and lives his life for the next 30 years, possessing the knowledge his loop is going to be closed. In 30 years from this incident, he becomes the Second Older, who in comparison to the First Older has an advantage of knowing how his life supposed to end(3), and he has the ability to do something against being killed.
Second Younger has no knowledge of the First Younger having his loop already closed, so he is surprised to see his victim without a bag on his head. Second Older is most likely shocked by the time travel, and it takes him few seconds to react, but it's a second less than it takes to the Second Younger to react, and this way he is able to block the shot with the gold tied to his back, and to save his life.
Another important point to take notice of, is the flashback(4) that First Younger sees before he shoots the First Older in real time. This incident allows the Second Older to improvise his escape from being killed by the Second Younger.
Footnotes
(1) Second Older knows that First Younger had this day-dream about missing his victim and going back to his apartment to retrieve the silver plates and to escape, and therefore Second Older follows Second Younger to his apartment after Second Younger misses Second Older and Second Older escapes.
(2) The blurry thoughts of Second Older when he sits in the bistro with Second Younger versus the photo of Second Older wife in his watch.
(3) We're getting into sort of a time paradox in here, since Older supposed to have all the memories and the experience that Younger has, and he supposed to know that his loops is going to be closed on the first time that Older is sent back in time. A possible solution to this time paradox is to assume that an experience becomes a memory in the future only after it happened in the past, and there are no parallel possible time lines.
(4) Technically this is not a flashback, since he most likely day-dreams the whole scene while First Younger waits for his victim to arrive from the future. We know that this was a day-dream/flashback only because we see that later he kills the First Older, and later, in a similar way, Second Younger shoots at the Second Older, who already has the memory of this day-dream.
At a guess: Infinite parallel worlds. In 50% of the worlds where Joe's sent back in time, he escapes.
As great as the movie was, Looper wasn't very rigid on the rules of time travel.
When he is sent back the second time, there is no bag over his head. This is what causes his younger version self to pause, and in that pause allows the older version to escape. The younger version most likely recognized that the man he was about to kill was his future self.
One thing to remember about the Looper universe and its treatment of time travel is that it is rife with paradoxes and real-time updates to the timeline.
Just prior to Old Joe arriving in 2044, Young Joe's friend Seth has messed up and let his Loop go. This led to his, fairly gruesome, dismemberment and subsequent inability of Seth to do whatever it was that he might have done in a timeline where he had successfully closed his loop. We know he must have been able to close his loop in another timeline, because Old Seth arrived in 2044 with all his limbs intact. Perhaps he would have gone on to kill the Rainmaker, or made Joe move to France instead of China.
So this is at least one in-movie example of a timeline change occurring between Joe1 and Joe2, but the basic premise of the movie makes me expect continuity to behave less like a loop and more like a wildly spiraling Mandelbrot set.
