Lost

Okay, who has a guess as to what that black cloud thing is?

I'd heard that one of the show's writers made a comment about "Notice we've never stated just WHEN this plane went down. We've given no clues as to what era it is... Think of a passage to another dimension as being what the project was about..."

So having heard that, I begin to think that Walt and the others are in a different dimension and that somewhere on the island is a passageway. I at first thought the black cloud might fit, but then it moves so oddly. I'm no longer sure.