A View of Sir Isaac Newton's PhilosophyPemberton, Henry
Science
A View of Sir Isaac Newton's Philosophy
Pemberton, Henry
Newton, Isaac, 1642-1727. Principia
12. IN the next place, from what has been now proved, our great author
has deduced this farther consequence, no less surprizing than elegant;
that each of the particles, out of which the bodies of the sun and
planets are framed, exert their power of gravitation by the same law,
and in the same proportion to the distance, as the great bodies which
they compose. For this purpose he first demonstrates, that if a globe
were compounded of particles, which will attract the particles of any
other body reciprocally in the duplicate proportion of their distances,
the whole globe will attract the same in the reciprocal duplicate
proportion of their distances from the center of the globe; provided
the globe be of uniform density throughout[251]. And from this our
author deduces the reverse, that if a globe acts upon distant bodies by
the law just now specified, and the power of the globe is derived from
its being composed of attractive particles; each of those particles
will attract after the same proportion[252]. The manner of deducing
this is not set down at large by our author, but is as follows. The
globe is supposed to act upon the particles of a body without it
constantly in the reciprocal duplicate proportion of their distances
from its center; and therefore at the same distance from the globe, on
which side soever the body be placed, the globe will act equally upon
it. Now because, if the particles, of which the globe is composed,
acted upon those without in the reciprocal duplicate proportion of
their distances, the whole globe would act upon them in the same manner
as it does; therefore, if the particles of the globe have not all of
them that property, some must act stronger than in that proportion,
while others act weaker: and if this be the condition of the globe,
it is plain, that when the body attracted is in such a situation
in respect of the globe, that the greater number of the strongest
particles are nearest to it, the body will be more forcibly attracted;
than when by turning the globe about, the greater quantity of weak
particles should be nearest, though the distance of the body should
remain the same from the center of the globe. Which is contrary to what
was at first remarked, that the globe on all sides of it acts with the
same strength at the same distance. Whence it appears, that no other
constitution of the globe can agree to it.
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