.

Newton had noticed that the stars within a certain territory all moved
in similar directions, and so must be acted upon by the same influences.
The Law of Gravitation!

It is held by many people in East Aurora and elsewhere that Newton's
invention is a devilish device originated for the benefit of surgeons
and crockery-dealers. But this is not wholly true.

Without this Law of Gravitation the Earth could not retain her spherical
shape: only through this constant drawing in toward the center could she
exist.

The other planets, too, must be round or they could not exist, and so
they also had this same quality of gravity in common with the Earth--a
drawing in of everything toward the center. Here was clearly a positive
discovery--this similarity of the heavenly bodies!

Every one of the heavenly bodies was exerting a constant attraction
toward all other heavenly bodies, and this attractive power must be in
proportion to the distance they were from the object acted upon. Thus
were their movements and orbits accounted for.

At this time Newton was perfectly familiar with Kepler's Law, that the
squares of the periodic times of a planet were as the cubes of its
distance from the sun. And from this, he inferred that the attraction
varied as the square of the planet's distance from the sun.

Here he was working on territory that had never been surveyed. At
first, in his exuberance, he thought to figure out the size and weight
of each planet quickly by measuring its attractive power. He did not
realize that he had cut out for himself work that would require many men
and several centuries to cover, but surely he was on the right scent--a
finite man keen upon the secrets of the Infinite!

He was still at his mother's old home in the country, without scientific
apparatus or the stimulus of colleagues, when we find by a record in his
journal that antique groan because there were only twenty-four hours in
a day, and that eight were required for sleep and eight more for
recreation!

A subject a little nearer home than planetary attraction had now
switched him off from measuring and weighing the stars. He was hard at
work in his mother's little sitting-room, with the windows darkened,
much to that good woman's perplexity.

By shutting out all light from the windows and allowing the sun's rays
to enter by a little, circular aperture, he had gotten the sunlight
captured and tamed where he could study it. This ray of light