Introduction Kepler's New Astronomy Three Models Kepler's Departure Finding "Oppositions" The "Mean" Sun Twelve Observations Ptolemy's "Equant" A "Vicarious Hypothesis" Earth's Motion An "Immaterial Species" Area-Time PrincipleAn Ellipse Conclusion On Harmony The Calculus Part II Recommended Books


Metaphysics of Gravitation

In De Magnete Gilbert stated, "It is to be understood, however, that not from a mathematical point does the force of the stone emanate, but from the parts themselves." (Dover edition, New York, 1958, p. 23)


Kepler highlighted the notion that the magnet as a whole and not a mathematical point, as Isaac Newton (1642-1727) later suggested, generates the attractive or repulsive forces. 

Kepler also observed that the power (or species) “will therefore not be any geometrical [solid] body, but is like a variety of surface, just as light is. ... To generalize this, the species which proceed immaterially from things are not by that procession extended through the dimensions of a body, although they arise from a body (as this one does from the body of the Sun).  Instead, they proceed according to the very law of emission: they do not possess their own boundaries, but just as the surfaces of illuminated things cause light to be considered as surfaces in certain respects, because they receive and terminate its emission, so the bodies of things that are moved suggest that this moving power be considered as if a sort of geometrical [solid] body, because their whole masses terminate or receive this emission of the motive species, so that the species can subsist nowhere in the world but in the bodies of the mobile things themselves.  And, exactly like light, between the source and the movable thing it is in a state of becoming, rather than being.” (Selections from..., Donahue, pp. 60-61)


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