"The origin of the solar system is, you know, a mystery," replied the astronomer. "According to the nebular hypothesis we may imagine that two or more dark suns, perhaps encircled with planets, have come into collision. Burst into atoms by the stupendous shock they would fill the surrounding region with a vast nebula of incandescent gases in a state of violent agitation. Its luminous fringes would fly immeasurably beyond the present orbit of Neptune, and then rush inwards to the centre, only to be driven outwards again. Surging out and in, the fluid mass would expand and contract alternately, until in course of ages the fiery tides would cease to ebb and flow. If the impact had been somewhat indirect it would rotate slowly on its axis, and under the influence of gravity and centrifugal force acquire a globular shape which would gradually flatten to a lenticular disc. As it cooled and shrank in volume it would whirl the faster round its axis, and grow the denser towards its heart. By and by, as the centrifugal force overcame gravity, the nebula would part, and the lighter outskirts would be shed one after another in concentric rings to mould the planets. The inner rings, being relatively small and heavy, would probably condense much sooner than the large, light, outer rings. The planetoids are apparently the rubbish of a ring which has failed to condense into one body, perhaps through its uniformity or thinness. The separation of so big a mass as Jupiter might well attenuate the border." "If the planetoids were born of a single small ring, might not several planets be condensed from a large one?" "I see nothing to hinder it. A large ring might split into smaller rings, or condense in several centres." "Because it seems to me that might explain the distinction between the inner and the outer planets. Perhaps the outer were first thrown off in one immense ring, and then the inner in a smaller ring. Before separation the nebula viewed edgewise might resemble your Indian club."