But this conception of the circle
afterwards came to acquire superstitious tenacity, being regarded as
the perfect form, and the only one suitable for such divine natures as
the stars, and was for two thousand years an impregnable barrier to the
progress of Astronomy. To account for every new appearance, every
deviation from circular perfection, a new cycloid was supposed, till
all the simplicity of the original hypothesis was lost in a
complication of epicycles:--
"The sphere,
With centric and eccentric scribbled o'er,
Cycle and epicycle, orb in orb."
By the end of the sixteenth century the number of circles supposed
necessary for the seven stars then known amounted to seventy-four,
while Tycho Brahe was discovering more and more planetary movements for
which these circles would not account.
To push aside forever this complicated chaos and evoke celestial order
and harmony, came Kepler. Long had the sublime intuition possessed him,
that numerical and geometrical relations connect the distances, times,
and revolutions of the planets. He began his studies on the planet
Mars,--a fortunate choice, as the marked eccentricity of that planet
would afford ready suggestions and verifications of the true law of
irregularity, and on which Tycho had accumulated copious data.
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