How Eloise knows about the sideways timeline by Sam

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I know Darlton have said that the sideways universe isn't an alternate timeline in the traditional sense, but I'm going to refer to it like that because it's easier :p
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In "Happily Ever After", it appeared that Eloise was aware of the alternate timeline and didn't want Desmond to find out about it (at least not yet). How does she know? I think the answer lies in the exact nature of the alternate timeline.

Most people seem to be under the impression that alternate timeline came into existence with a fully formed past, even before 1977. This is because the Losties never crashed in 2004, and so they never travelled back to the 50s and 70s, and so things were different even before Jughead was detonated.

I don't think that the writers will go in this direction, though. I think that the alternate timeline will be something like this:

Original timeline
___________________________________________________
1977
_____________________
New timeline

(Hopefully the diagram comes up right)

So up until 1977, both timelines shared the same history. When Jughead is detonated, the timeline splits into two. The alternate timeline branches off of the original timeline.

Most people are saying things like "but Ben can't have been shot by Sayid because Sayid never came to the island in this timeline!". This is true - the alternate Sayid didn't come to the island - but he doesn't need to. The original Sayid has already done it! The original Losties still travelled back to 1974/1977, and so they were still present in the alternate timeline. Juliet still detonated the bomb, but it was the original Juliet who did this.

I think it's this concept that seems to be confusing people. But it makes perfect sense, and resolves any potential paradoxes. The fact that Juliet detonated the bomb in the alt. despite never coming to the island is not a paaradox at all, because the Juliet that never comes to the island is the alternate Juliet, whilst it was the original Juliet that detonated the bomb.

So how does this all relate to Eloise? Well, she is one of the few people who would have witnessed the split in the timeline (along with Pierre Chang and perhaps Charles Widmore):

- She would remember killing her son.
- She would remember that a plan was put in action to stop this from ever happening.
- She would have Faraday's journal, which contains a complete history of events that will never happened in the alternate timeline.

From all of this, she would deduce that Faraday's plan has worked, and that the bomb had succeeded in preventing Faraday from dying and the plane from crashing. Now that the island is underwater (I'm not sure how this happens - I don't think the bomb caused it), she allows Faraday to follow his dreams and become a musician, instead of forcing him to become a scientist. She doesn't want Desmond to realise this because Faraday is alive in this timeline.

We can also assume that Pierre Chang would remember being visited by the original version of Miles. Knowing that Faraday was from the future, he may also be aware that Faraday succeeded in changing the future.

My main point is: the alternate timeline is not a complete, independent timeline. It's a branch off of the original timeline, caused by Jughead. This means that any time travelling that occurred in the original timeline prior to 1977 still happened in the alternate timeline.

Hopefully this wasn't too confusing!