Time travel on Lost has always bee surprisingly logical. Despite all of the time jumping in season 5, there were clearly defined rules and a set timeline. However, the weird altverse created by the flash sideways has torn the fabric of time apart.
I've been operating under a simple assumption. I thought that the bomb detonating on the Island created a separate timeline and that, even in the altverse, all events prior to the explosion were identical to those in the original timeline.
To explain, here's an illustrated diagram of my theory. The blue line represents the original timeline seen in the first five seasons. The yellow line represents the timeline in the altverse. The green portion is an overlap of the two, and the giant black dot is the detonation of the bomb in 1977, the event I thought caused the rift in time.
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