Salv.You have good cause for your doubt: and when we come to treat of the other Motion, you shall see how far Copernicus excelled Ptolomey in clearness and sublimity of wit, in that he saw what the other did not, I mean the admirable harmony wherein that Motion agreed with all the other Cœlestial Bodies. But for the present we will suspend this particular, and return to our first consideration; touching which I will proceed to propose (begining with things more general) those reasons which seem to favour the mobility of the Earth,Why the diurnal motion more probably should belong to the Earth, than to the rest of the Universe. and then wait the answers which Simplicius shall make thereto. And first, if we consider onely the immense magnitude of the Starry Sphere, compared to the smalness of the Terrestrial Globe, contained therein so many millions of times; and moreover weigh the velocity of the motion which must in a day and night make an entire revolution thereof, I cannot perswade my self, that there is any man who believes it more reasonable and credible, that the Cœlestial Sphere turneth round, and the Terrestrial Globe stands still.
Sagr.If from the universality of effects, which may in nature have dependence upon such like motions, there should indifferently follow all the same consequences to an hair, aswell in one Hypothesis as in the other; yet I for my part, as to my first and general apprehension, would esteem, that he which should hold it more rational to make the whole Universe move, and thereby to salve the Earths mobility, is more unreasonable than he that being got to the top of your Turret, should desire, to the end onely that he might behold the City, and the Fields about it, that the whole Country might turn round, that so he might not be put to the trouble to stir his head. And yet doubtless the advantages would be many and great which the Copernican Hypothesis is attended with, above those of the Ptolomaique, which in my opinion resembleth, nay surpasseth that other folly; so that all this makes me think that far more probable than this. But haply Aristotle, Ptolomey, and Simplicius may find the advantages of their Systeme, which they would do well to communicate to us also, if any such there be; or else declare to me, that there neither are or can be any such things.
Salv.For my part, as I have not been able, as much as I have thought upon it, to find any diversity therein; so I think I have found, that no such diversity can be in them: in so much that I esteem it to no purpose to seek farther after it.Motion, as to the things that equally move thereby, is as if it never were, & so far operates as it hath relation to things deprived of motion. Therefore observe: Motion is so far Motion, and as Motion operateth, by how far it hath relation to things which want Motion: but in those things which all equally partake thereof it hath nothing to do, and is as if it never were. And thus the Merchandises with which a ship is laden, so far move, by how far leaving London, they passby
