So im sitting here doing what all of us here do best and Im watching How the Earth Was Made, and I come up with this theory about how the earth was made. So stay with me. . . The center of the earth is roughly as hot as the outside of the sun. So what if the earth at one point was a star or sun? Say for some reason or another this "star" got rapidly cool whether because it was dying or something in space caused it to rapidly cool. The outside would become icey, hard, and solid much similar to the effect of lava rapidly cooling. Only lava doesnt usually make ice, but that wouldve come from rapid cooling in space. The hot magma that remained(which we now refer to as the center of earth) was left trapped inside the icey and rocky crust. It makes its orbit around our sun, and the first time it gets close to it, it melts the icey caps and form oceans. . .and life from there begins. Its just a theory, it may be out there as a theory already, but I had to type it up before I forget it.