What I think really happened at the end of... The End (and what is the Flash-sideways timeline) by Peter

I liked the finale, a lot. And the fact that we didn’t get the answers to every single mystery doesn’t bother me at all. The mysteries after all were an inherent aspect of the show.

The only thing that bothered was the revelation of what the flash-sideways universe (fsU) is. The conflict between science and fate can be traced back to the very first season. However a spiritual ending just ignores the science part.

The majority of people believe that the Flash-sideways world is purgatory, the afterlife, or something similar. Well, I disagree. Not just because I am a “man of science”, but because there are things that just don’t add up.

First of all it seems to be a rather too complex world if it is just a “step before Heaven”. If they just created the fsU just to find the others, why didn’t they have any recollection of the island events from the beginning? Why did they create so many people that were unimportant to them (like Omar, or even the people in the streets or the airport)?

Also Daniel believed the life they lived just wasn’t meant to be, and somehow by detonating Jughead they change their “real” life.
Moreover Desmond “travelled” to the fsU even he didn’t have a near death experience.

We’ve also seen people die in the flash-sideways. How can they die if they are already dead?

So I think that detonation of Jughead resulted in creating the incident AND a parallel universe.
The producers themselves said they use the term flash-sideways, and that this world is equally real with the one we already knew. I tend to believe that they meant what they said. They even decided to show us (even with crappy CGI) that the island is underwater.
So for me, they detonated the bomb so as to change their lives. And that did happen. However what was really important in the end, was the experiences they had on the island, and the time they spent with their fellow Losties. Their lives were flawed, so the island gave them the chance to redeem themselves.
The same thing applies to the fsU, which gave them opportunity to also fight their demons. However they were destined for greater things, they were destined to find each other. And because of that the two parallel universes merged. Hence the flashes they had. As a result the consciousness of the original Losties was transferred to the fsU Losties. And because the lifespan of each one of them was different, after the “transfer” everyone was there but from different points in time. Some of them died pretty much early, and others (i.e. Ben & Hurley) a thousand years later. All of them however, were present at the church.
So they created the fsU (be detonating Jughead), and they found each other even if they were all of them dead (in the Original Universe).
The only 2 things that seem to contradict this theory is the presence of Christian, and the white light that came through the door. We’ve seen though weird and mystical light before (swan implosion, time travelling, Jughead explosion, the heart of the island). And lots of people apart from Smokey have appeared in places where they shouldn’t (Walt, whispering Michael,etc). Christian himself appeared to Michael on the freighter (and at least then he wasn’t the Man in Black), so maybe he is also in a way special, or at least a representative of the Island (?). I don’t know. But I prefer not to know where Christian or the light came from, than believing that 1/3 of Season 6 was a dream, purgatory, nirvana, afterlife, or anything equally weird that doesn’t seem to follow the plot, and the major philosophical points the show made, over the last 6 years.
I hope that some of you agree with me (even partially), and the fact that English isn’t my first language (I’m Greek), didn’t present any problems understanding what I’m trying to say.