History of Solar System formation and evolution hypotheses is captured by the Sun and planets form from it. In this there were 6 original planets, corresponding to 6 point-masses in the filament, with planets A and B, the 2 innermost, colliding, the former at twice the mass of Neptune, and ejecting out of the Solar System, and the latter at 1/3 the mass of Uranus, and splitting into Earth and Venus. Mars and the Moon are former moons of A. Mercury is either a fragment of B or an escaped moon of A. The collision also produced the asteroid belt and the comets. T.J.J. See was an American
Planets in science fiction and it is extremely hostile to life. Various planets of the Solar System were used as settings for science fiction stories in the first half of the 20th century; but dissatisfaction with the limits imposed by science led many writers early on to forsake the Solar System for fictional planets around distant stars. As increasing knowledge of the Solar System made the prospects of life in the vicinity of Earth marginal at best, the extrasolar planet has become almost the only venue for contemporary science fiction. In many works of science fiction, planets are only described casually, as points of