In season 1 towards the season finale, Olivia seems to cross 'Over There' unwittingly, and it seems 'Over There' is very similar to 'Over Here' but when they cross over again (Walter, Olivia and the other Cortexiphan kids) and afterwards, it seems like is a way more advanced 'Over There' than we first saw in Season 1.

Why did this happen? I'm assuming 'Over here' and 'Over there' are similar with time transcurrance.