Kepler

In order to emphasise the importance of the reforms introduced into
astronomy by Kepler, it will be well to sketch briefly the history of
the theories which he had to overthrow. In very early times it must
have been realised that the sun and moon were continually
changing their places among the stars. The day, the month, and the
year were obvious divisions of time, and longer periods were
suggested by the tabulation of eclipses. We can imagine the respect
accorded to the Chaldaean sages who first discovered that eclipses
could be predicted, and how the philosophers of Mesopotamia must
have sought eagerly for evidence of fresh periodic laws. Certain of
the stars, which appeared to wander, and were hence called planets,
provided an extended field for these speculations. Among the
Chaldaeans and Babylonians the knowledge gradually acquired was
probably confined to the priests and utilised mainly for astrological
prediction or the fixing of religious observances.