An introduction to mathematics, by A. N. Whitehead.

CONIC SECTIONS 137
were found to be the necessary key with
which to attain the knowledge of one of the
most important laws of nature.
Meanwhile the entirely distinct study of
astronomy had been going forward. The
great Greek astronomer Ptolemy (died 168
A.D.) published his standard treatise on the
subject in the University of Alexandria, explaining the apparent motions among the
fixed stars of the sun and planets by the conception of the earth at rest and the sun and
the planets circling round it. During the
next thirteen hundred years the number and
the accuracy of the astronomical observations increased, with the result that the description of the motions of the planets on
Ptolemy's hypothesis had to be made more
and more complicated. Copernicus (born
1473 A.D. and died 1543 A.D.) pointed out
that the motions of these heavenly bodies
could be explained in a simpler manner if the
sun were supposed to rest, and the earth and
planets were conceived as moving round it.
However, he still thought of these motions as
essentially circular, though modified by a set
of small corrections arbitrarily superimposed
on the primary circular motions. So the
matter stood when Kepler was born at Stuttgart in Germany in 1571 A.D. There were
two sciences, that of the geometry of conic
sections and that of astronomy, both of which