L’inclinaison Moyenne Des Orbites Des Comètes Sur La Figure De La Terre Et Sur Les Fonctions

One of the most extraordinary phenomena which the system of the world offers to us is the movement of the planets and of their satellites in the same sense and very nearly in the same plane; if we picture to ourselves in fact all these stars describing from west to east some nearly circular orbits and very little inclined to the ecliptic, while the comets seem to be moved indifferently in every sense and with every possible inclination in some very eccentric eclipses, we perceive a quite marked separation between the planets and the comets, such that, in the movement of these great bodies, nature does not follow this gradation by insensible nuances which she always observes when its march is not interrupted by some particular causes. We count in all six planets and ten satellites; now, if we suppose that they have been launched at random, it is easy to see that the probability that they will rotate all in the same sense is 1 2 = 1 32768 , so that there is odds 32767 against unity, that this will not happen. If we multiply the fraction 1 32768 by that which expresses the probability that the orbits will be contained in a likewise small zone as that which contains them, we will see that the actual disposition of our planetary system would be infinitely less probable if it were due to chance, and that it announces consequently, with a certitude equivalent or even superior to that of a great number of events of which it would seem absurd to us to doubt, the existence of a regular cause which has determined the planets and their satellites to be moved in the same sense and nearly in the same plane; I suppress that analysis, that M. Daniel Bernoulli has given a long time ago, and which besides is quite simple.1 Now what is the cause which is able to have determined thus the movement of the planets and of the satellites? Has it been particular to these stars, or indeed has it had an influence on the movement of all those which rotate around the sun? The first of these questions seems to me quite difficult to resolve; and I confess that after having reflected