Newton's Principia : $b The mathematical principles of natural philosophyNewton, Isaac
General
Newton's Principia : $b The mathematical principles of natural philosophy
Newton, Isaac
Celestial mechanics -- Early works to 1800; Mechanics -- Early works to 1800
From the first law of Kepler, namely, the proportionality of[Pg 34] the areas
to the times of their description, our author inferred that the force
which retained the planet in its orbit was always directed to the sun;
and from the second, namely, that every planet moves in an ellipse with
the sun in one of its foci, he drew the more general inference that the
force by which the planet moves round that focus varies inversely as
the square of its distance therefrom: and he demonstrated that a planet
acted upon by such a force could not move in any other curve than a
conic section; showing when the moving body would describe a circular,
an elliptical, a parabolic, or hyperbolic orbit. He demonstrated, too,
that this force, or attracting, gravitating power resided in every,
the least particle; but that, in spherical masses, it operated as
if confined to their centres; so that, one sphere or body will act
upon another sphere or body, with a force directly proportional to
the quantity of matter, and inversely as the square of the distance
between their centres; and that their velocities of mutual approach
will be in the inverse ratio of their quantities of matter. Thus he
grandly outlined the Universal Law. Verifying its truth by the motions
of terrestrial bodies, then by those of the moon and other secondary
orbs, he finally embraced, in one mighty generalization, the entire
Solar System—all the movements of all its bodies—planets, satellites
and comets—explaining and harmonizing the many diverse and theretofore
inexplicable phenomena.
Guided by the genius of Newton, we see sphere bound to sphere, body
to body, particle to particle, atom to mass, the minutest part to the
stupendous whole—each to each, each to all, and all to each—in the
mysterious bonds of a ceaseless, reciprocal influence. An influence
whose workings are shown to be alike present in the globular dew-drop,
or oblate-spheroidal earth; in the falling shower, or vast heaving
ocean tides; in the flying thistle-down, or fixed, ponderous rock;
in the swinging pendulum, or time-measuring sun; in the varying and
unequal moon, or earth's slowly retrograding poles; in the uncertain
meteor, or blazing comet wheeling swiftly away on its remote, yet
determined round. An influence, in fine, that may link system to system
through all the star-glowing firmament; then firmament to firmament;[Pg 35]
aye, firmament to firmament, again and again, till, converging home, it
may be, to some ineffable centre, where more presently dwells He who
inhabiteth immensity, and where infinitudes meet and eternities have
their conflux, and where around move, in softest, swiftest measure, all
the countless hosts that crowd heaven's fathomless deeps.
Public-domain text, read in full here on John Shaqi.
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