What that power is we shall try to find out as we consider the application of Kepler's Laws to this onward movement of the sun. If, then, the sun is moving through space with this enormous velocity, the question arises as to what is the shape of the path or orbit which it describes? Sir Wm. Herschel attacked this question from a mathematical standpoint, and came to a certain conclusion, as we shall see. We will, however, attack the problem solely from the philosophical standpoint, by applying to it the Rules of Philosophy given in our first chapter, and we will then see whether our result is in harmony with the conclusions arrived at by Sir Wm. Herschel. Now what has experience and observation to tell us regarding the orbit which any body moving in space assumes? Take, for example, our moon as illustrating the movement of all satellites, and our earth as illustrating all planetary motion. What does observation teach us as to the orbits which these bodies describe? If it teaches us anything at all, it teaches us that every satellite and planet moves with varying velocity in a varying orbit around some central body. So far as our observation goes, then, in relation to planetary motion, or the motion of satellites, we learn that every body which moves in space fulfils Kepler's First Law, and describes an orbit round a central body, that body occupying one of the foci. Thus, wherever we get any body moving in space, if there be any truth in philosophy which is based on experiment and observation, that body ought also to move in similar elliptic orbits, and be subject to exactly similar conditions governing those orbits. But we have learned that the sun moves through space with a velocity of about five miles per second, therefore it follows, philosophically, that the sun must also move around some other central body, and the path of such movement is that of an elliptic orbit, with the central body around which it moves occupying one of the foci. In other words, the sun obeys the first of Kepler's Laws, the same as all the planets and satellites do. Suppose, for a moment, that it is denied that the sun moves in an elliptic orbit! What path would it pursue in place of that? Would the path be that of a straight line towards the constellation of Hercules? Such an assumption would be altogether unphilosophical, as it is contrary to all experience and observation, and is therefore untenable. Before such an assumption can be made, it must be proved that every planet and satellite moves in a straight line, and not till that has been done can it be assumed that the sun moves in a straight line, or indeed in any other path than that stated in the first of Kepler's Laws.