First of all… I am aware that this theory is incomplete. It is really just the first idea that made sense to me after watching the finale… Having said that, I would really appreciate your input in either adding on to this theory or completely debunking it… your choice.
The question I am attempting to answer is this:
“So if Jughead didn’t create an alternate timeline, then what did the bomb do?”….
First of all, if the bomb did in fact detonate (now that we know that there was only one timeline), Pierre Chang and Radzinsky would have died in the explosion (along with several others). But we know that Chang lived to make those DHARMA videos and Radzinsky lived to push the button in the hatch…
So the most plausible start to any theory regarding the bomb (though not automatically the correct one), is to assume that the bomb did not explode…… at least in 1977. Here’s what I think happened:
The Island flashed the Losties back into their original time frame right before Juliet could detonate the bomb. The Island had to do this as a last resort because it was the only way left for the Island to stop them from detonating it. So now, there’s an H-bomb sitting at the bottom of the very deep hole that the D.I. has drilled. We know that after the incident, the D.I. had to build a device (the button in the hatch) that would dissipate the electro-magnetic energy that was seeping out of the Island as a result of them drilling into the pocket of energy. As a fail-safe, they connected the hydrogen bomb to a keyhole and gave the failsafe key to the button-pusher. But whoever turned the key would die because no one can survive the electro-magnetic pulse created by a hydrogen bomb…Â except Desmond.
So the Losties had to go back in time not toÂ detonate the bomb, but simply to put the bomb there so that the D.I. could create a failsafe that Desmond would later utilize to save the world… After all, the bomb was rigged to detonate on impact. If it wereÂ supposed to go off in 1977, it would have gone off when it hit the ground after falling for over 100 feet.
So what was the importance of the bomb?… If they had not gone back in time and put the bomb there, the failsafe would never have been created and Locke’s failure to press the button would have lead to the end of the world… So although it didn’t create an alternate timeline as Dan had hoped (although he previously admitted several times that he knew this to be impossible), it did save the world–a feat that I would classify as “pretty damn important.”