Did anyone see Another Earth, an indie film done about 5 years ago? It concerns the discovery of a second identical Earth right next to ours the night a tragic accident happens to the MC and the open question throughout is what would your life would be if you could live it slightly differently? The theme has certainly been explored many times in SF, but I found this particular story very affecting. The "other Earth" is just a mechanism for the characters to explore themselves, which, to me, is a lot more interesting than blowing up space ships. Plus it stars the amazing Brit Marling.