Board Thread:New on Arrowverse Wiki/@comment-807326-20160206040643/@comment-26412696-20160310213628

8th Hero of Olympus wrote: Well, in that case, the synopsis has confirmed the theory - Barry is on Earth-1, while Kara is on Earth-S. Which we've more or less known for ages now, but it's always nice to have official confirmation.

By the way, I hate to revive this argument from about halfway up the thread, but Earth-2 is an alternate reality, not a separate timeline within Earth-1.