[nooni]

heres a good explanation provided by someone named John McKinnon on facebook. he did a very good job and i have to give credit where credit is due....

Chart 1:



This chart represents our timeline. I know the writers said that there are no parallel realities, but I believe that they were purposely being ambiguous when they said this. They were trying to make the point that the flashforwards were definitely going to happen, so when they said "there are no parallel realities" I believe they meant parallel realities cannot be maintained. (In other words, course-correction) Face it, we have seen two series of "parallel events" when Desmond goes to the ring shop.

So, let's look at Desmond's consciousness as it moves through time. Des leads a pretty normal life, travelling along what we'll call "the main timeline" (the straight, dark green one) and ignoring all other realities. When he finally reaches 2004, he turns the failsafe key and his consciousness is sent back in time (dotted green line) to 1996.

Now Desmond is reliving the same point in time, but he is privy to extra knowledge, making him behave differently. These alternate actions on his part create an alternate set of events (represented by the red line). The way that the universe works, however, is by "course-correcting"...ie it fixes any changes made by the time traveller and returns the universe to its pre-destined path. Those changes still happened, but they are irrelevent because they have no long-lasting effect. This course-correction is represented by the purple line.

In Desmond's case, the red line is created by him buying the ring, visiting his physicist friend, talking to Charlie, and numerous other things he does differently. His purple line begins when Ms. Hawking tries to convince him to give the ring back. Desmond wants to stay on the red line, control his own fate, but the universe wins and he throws the ring away (purple line here).

As the alternate events begin to grow closer to the "original events", Desmond is knocked out in a bar and his consciousness returns to 2004, just after the blast. Presumably, back in 1996, Des wakes up in the bar, unaware of anything that's just happened (since his 1996 mind has returned) and the timeline moves smoothly along as if Desmond had never time travelled in the first place.