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direction em 4 , and so on. Although, therefore, its orhit roundthe Sun is, as we have stated, nearly the same as that ofthe Earth , it is abundantly evident that the Moon will appearto an observer on the Earth to travel round and round thelatter month by mouth.
We have endeavoured to elucidate this point somewhat fully,not only because the mental effort needed to comprehend itmay, we hope, be useful to some of our readers, hut because itmay assist them in realizing the vast scale upon which the Solar System is constructed, by showing how insignificant a matterthe Moon ’s orbit round the Earth really is. The point is,moreover, one which is insufficiently explained in some astro-nomical text-hooks, in which diagrams resembling Fig . XIY.have been used to represent the paths of the Earth and of theMoon . We would fain hope that those who have perused the
preceding explanation will henceforth understand how muchthe real orhit of the Moon differs from any such wavy curve.
We may sum up the conclusions to which we have so farattained by stating that the Moon , in regard to the Earth , mayhe termed its Satellite or attendant; but iu regard to the Sun ,it should rather he termed a Planet , its orbit round the Sun being so little changed by the Earth ’s attraction that it alwaysremains concave to that great central luminary, like that of theEarth itself, although the degree of concavity is slightly lessthan in the Earth ’s orhit when the Moon is New, and greaterwhen it is Full. The very slight difference in the two orbitsalso involves the fact that the Sun attracts them both withnearly the same power, and that consequently the Moon doesnot desert the Earth , although the Sun ’s power over it is morethan twice as great as that of the Earth . It could, indeed, onlydo so, if at any time the difference between the Sun ’s power overit and over the Earth were greater than the Earth ’s attraction