III. Tycho Brahe

IV. Kepler Joins Tycho

V. Kepler's Laws

VI. Closing Years

Appendix I.--List of Dates

Appendix II.--Bibliography

Glossary




CHAPTER I.

ASTRONOMY BEFORE 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