No Explosion = No Island by Jacob4Jesus

I want to write a short theory because I think people are constantly debating something and getting it wrong over and over again as to the whole bomb going off / not going off issue.

As some of have said, the jughead detonation did not sink the island and create the "new" timeline. The jughead detonating did the exact opposite. I thought the show was quite clear on this to the point I didn't realy think it was a question as to what effect the bomb detonation had. So I guess I'll explain it here, as "a theory" even though it seemed clear enough to me that this mystery was solved in the opening minutes of the premiere.

First, the bomb exploded in the "main" timeline and a split second after, Kate, Jack, and all the 1977 Losties were transported to 2007. This is what's heard just as Kate is shown waking up in the tree at the beginning of season 6. If the sound of the bomb going off wasn't enough of a "clue," then Kate's and Miles' ears ringing from the explosion should be enough to drive the point home. Miles was correct in the season 5 finale, when he said that the incident was the Losties setting the bomb off. So, the on island Season 6 is what happened because jughead detonated. I don't think this conclusion really is a "theory" because it has been so clearly shown. Whatever the bomb did, at minimum it diffused the Swan energy long enough to build the hatch and setup the button. It was a bolder that blocked up the Swan energy, and continued forward the timeline that was Seasons 1-5.

Second, the bomb NOT exploding is what caused the island to be underwater. (This could be considered a theory as maybe something else caused the island to "sink" but there is no hint whatsoever that anything else caused it). The pocket of energy under the Swan kept expanding/growing after pulling in everything around the Swan construction site to the point that it either moved the island (like the donkey wheel) or destroyed the land under island causing the it to sink/teleport to the ocean floor in 1977. From what was shown in the Season 6 premiere, this is by far the simplest explanation as to the sunken island. The island could have slowly gone down, and thus, allowed everyone to get off. This would explain how Ben didn't die on the island and went on to become a middle school history teacher. Still, ultimately, without the detonation, the Island was "not protected" and ceased to exist, because something covered with water is not, by definition, an "island."

Ok, so I just wanted to clear up the apparent confusion about what timeline the bomb explosion existed in.