Alternate worlds were once a hallmark of the DC Universe. Various Earths existed that were strikingly alike yet distinctly unique. The modern heroes of the Justice League of America existed on Earth-One while the Justice Society of America, their Golden Age predecessors, lived on Earth-Two. Infinite other Earths existed, each with a unique difference. Это и многое другое вы найдете в книге Superman: Infinite Crisis (Joe Kelly, Marv Wolfman, Geoff Johns, Jeph Loeb)