It was also shown indisputably, that it would have been impossible for successive rings to have been abandoned at certain definite intervals by a contracting nebula, and granted a ring could have been formed it would have been impossible for it to condense into a planet, since forces residing in the sun would offset the gravitation of its parts.
When La Place advanced his famous theory it was, to use his own words, "with that distrust which everything ought to inspire that is not a result of observation or of calculation."
Were La Place living today he would be, we believe, the first to abandon a theory that is now known to be in accord neither with observation nor calculation.
Deprived of a theory that has served to explain the outstanding features of the solar system more or less adequately for one hundred and twenty-five years, astronomers are seeking in the light of recent observations and discoveries to formulate a satisfactory theory of the origin of the solar system.
In the planetesimal theory of Chamberlin and Moulton and the recently suggested theory of the well-known English mathematician, Jeans, _a second sun passing close to our own sun is assumed to have been the cause of the origin of the planetary system_.
The effect of the close approach of such a sun would be the ejection of a stream of matter from our sun, as we term it, in the direction of the passing body and also in a diametrically opposite direction. This ejection would be continuous as long as the stars remained near one another, the height attained by the ejected stream decreasing as the passing star receded. The result would be the formation of a _spiral nebula_ in which the motion of the ejected particles--planetesimals--would be across the spiral arms, toward and away from the passing star. After the sun had receded so far as to have no further effect upon these ejected particles they would revolve about the sun in more or less elliptical orbits which would gradually be reduced to nearly circular forms by repeated collisions between planetesimals. Larger nuclei would be formed and these would gradually sweep up smaller fragments and become the planets of the present system. Smaller nuclei in the vicinity of larger ones would become their satellites and in the course of many millions of years all of the larger fragments would be swept up by the planetary nuclei and their satellites--leaving only the asteroids, comets and meteors as survivors of the original spiral system.