My speculation on what Galactica will find when it finds Earth in the final fourth season: I expect they’ll find a dead planet that is somehow identifiable as Earth, and with Cylons closing in behind them, they will find some way to go way, way back in time, thus arriving on Earth many hundreds of centuries ago, safe from Cylons. And the implication would be that when they come to appreciate how far back in time they are, they’d eventually decide to leave Earth and found the twelve colonies with the hope that history won’t repeat. But it will, a bit differently each time, but it will. The Galactica folks would themselves cause the belief that “life here (on the 12 colonies) began out there”. It also avoids the problem of having to interact with our modern, real-life Earth. I realize this doesn’t take Kobal into account, so, I am suggesting this as a rough sketch. The key point is that there will be a loop.