Co77?ets from Fiction to Fact                       2 7

professor of mathematics at ^^'ittenburg and Altdorf, was one of
several who rejected the crystal spheres associated with the Ptolo¬
maic system. He did not reject the entire system, but concluded
that the sphere of air must extend all the way to the fixed stars.
Such a concept made it possible for some to retain the idea that
comets were born of the earth, but others found it hard to believe
that earthly exhalations could rise as high as the moon. Because of
such doubts, one common view divided comets into two classes,
those located above the moon (to which various celestial causes
were assigned) and those located in the sphere of air.

All of these concepts could be accommodated if necessary
within the basic tenets of the Ptolomaic system. On Tycho,
though, the new observations exercised a more extreme and per¬
haps their most important direct effect. It was largely his observa¬
tions of the nova of 1572 and the comet of 1577 which led Tycho
to reject Ptolomy and formulate his own cosmology. Tycho could
never bring himself to accept the Copernican system (and in fact
attempted to dissuade his protege, Kepler, from espousing it).
Instead, he devised a system with the sun and moon revolving
around a stationary earth, but with other planets circling the sun.
In this scheme, comets travelled around the sun in roughly circu¬
lar paths outside the orbit of Venus. The Tychonic system never
gained great popularity, but for a time it provided an acceptable
alternative for some who «'ere uncomfortable with Copernicus'
more controversial ideas.

The more far-reaching effects of the observations of these com¬
ets may well have been produced at a greater remove. As men¬
tioned before, one of the more accurate and insightful observers
of the comet of 1577 was a 27 year old German astronomer,
Michael Maestlin. Like Tycho, Maestlin not only surmised the
comet's distance, but attempted to plot its path as well. For the
16th century, the idea of computing cometary orbits was revolu¬
tionary, inspired to a large extent by their new association with the
other heavenly bodies, as opposed to ephemeral meteorological