Heres my idea, its based strictly on observation but it makes sense to me and I would like to hear input on the subject as to how much is already known and if the idea is possible? OK here goes,
After the Big Bang or whatever the resulting gasses and dust were put into motion. The smaller particles and dust orbiting around the larger pieces. As time progressed through the process of accretion the larger pieces did one of two things, either they accumulated so much mass that it set off a nuclear core and they became stars like our sun or if the core was not dense enough or failed to produce fission then planets were formed? Earth had a special event that caused our atmosphere and the emergence of life in that comets from the Keiper Belt and surrounding Oort cloud bombarded the Earth causing a cooling off and depositing organics in the resulting oceans. And Im not sure about this one but the temperature and density between the outer Oort cloud and the inner solar system may cause gravity?