ocentric theory, and who was
deeply impressed with the belief that relationships exist in the
revolutions of the planetary bodies round the sun, and that these if
correctly examined would reveal the laws under which those movements
take place, devoted himself to the study of the distances, times, and
velocities of the planets, and the form of their orbits. His method
was, to submit the observations to which he had access, such as those
of Tycho Brahe, to computations based first on one and then on another
hypothesis, rejecting the hypothesis if he found that the calculations
did not accord with the observations. The incredible labor he had
undergone (he says, "I considered, and I computed, until I almost went
mad") was at length rewarded, and in 1609 he published his book, "On the
Motions of the Planet Mars." In this he had attempted to reconcile the
movements of that planet to the hypothesis of eccentrics and epicycles,
but eventually discovered that the orbit of a planet is not a circle but
an ellipse, the sun being in one of the foci, and that the areas swept
over by a line drawn from the planet to the sun are proportional to the
times. These constitute what are now known as the first and second laws
of Kepler. Eight years subsequently, he was rewarded by the discovery
of a third law, defining the relation between the mean distances of the
planets from the sun and the times of their revolutions; "the squares of
the periodic times are proportional to the cubes of the distances." In
"An Epitome of the Copernican System," published in 1618, he announced
this law, and showed that it holds good for the satellites of Jupiter as
regards their primary. Hence it was inferred that the laws which preside
over the grand movements of the solar system preside also over the less
movements of its constituent parts.

The conception of law which is unmistakably conveyed by Kepler's
discoveries, and the evidence they gave in support of the heliocentric
as against the geocentric theory, could not fail to incur the
reprehension of the Roman authorities. The congregation of the Index,
therefore, when they denounced the Copernican system as utterly contrary
to the Holy Scriptures, prohibited Kepler's "Epitome" of that system. It
was on this occasion that Kepler submitted his celebrated remonstrance:
"Eighty years have elapsed during which the doctrines of Copernicus
regarding the movement of the earth and the immobility of the sun have
bee