Well my take on about the island is that it can't be seen unless by some kind of chance sighting like Namoi said. But if any kind of craft try to get to the island(s) they wreck by some type of force shield if you want to call it that. I kind of figure it like this some on the island(s) pulls certain things to it. That's how I figure the Black Rock ship got there, maybe cause Desmond wasn't there to put the numbers in is what brought down the airplane as it flew near the island(s). But if that's the case then how were they Ben's people able to quickly put together a fake airline crash site and getting all this information about the people from flight 815. So now I'm thinking maybe because every has some kind of connection to each by somebody in their past they were all planted to be on the plane at the same time. So could it be two 815 flights left at same time they both crash one is a setup that's found and investagated by blah blah agency of whatever from wherever okay. So these people are brought together and they're there to learn and find out that they are connected to each other in certain ways. And then they are put to test like Locke was about his dad (I'm still having a hard time believing that is Locke's real dad, another story for another time)to see how they'll deal with whatever it is. Like Locke couldn't kill his dad in front of all those people then he was given information about someone who is a possible killer who'll do what Locke couldn't do. I know I'm getting off from what I started at sorry I'll shut up and head back out to the rest of the herd moooovin along now.

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Standing in the ocean with the sun burning low in the west
Like a fire in the cavernous darkness at the heart of the beast
With my beliefs and possessions, stopped at the frontier in my chest
At the edge of my country, my back to the sea, looking east