34
T
o most people in mid-15th
century Europe, questions
about Earth’s place in
the cosmos had been answered
in the 2nd century by the Greco-
Egyptian mathematician Ptolemy,
who had modified ideas first put
forward by Aristotle. These ideas
placed Earth at the center of the
cosmos, and they carried an official
stamp of approval from the Church.
Yet the first convincing challenge
to this orthodoxy was to come from
a figure within the Church, the
Polish canon Nicolaus Copernicus.A stationary Earth
According to the version of the
universe described by Aristotle and
Ptolemy, Earth was a stationary
point at the center of the universe,
with everything else circling
around it, and stars were fixed
in a large, invisible, distant
sphere, which rotated rapidly
around Earth. The sun, moon,
and planets also revolved at
different speeds around Earth.
This idea of the universe
seemed like common sense.
After all, one only had to stand
outside and look up at the sky,
and it appeared obvious thatTHE COPERNICAN MODEL
Earth stayed in one place, while
everything else rose in the east,
swung across the sky, and set in
the west. Furthermore, the Bible
seemed to state that the sun moves,
whereas Earth does not, so anyone
who contradicted this view risked
being accused of heresy.Nagging doubts
The Earth-centered, or geocentric,
model of the universe had never
convinced everyone—in fact,
doubts about it had surfaced
from time to time for more than
1,800 years. The most seriousIN CONTEXT
KEY ASTRONOMER
Nicolaus Copernicus
(1473–15 43)BEFORE
c.350 bce Aristotle places Earth
at the center of the universe.c.270 bce Aristarchus proposes
a sun-centered (heliocentric)
universe, with the stars a vast
distance away.c.150 ce Ptolemy publishes
the Almagest.AFTER
1576 English astronomer
Thomas Digges suggests
modifying the Copernican
system, removing its outer
edge and replacing it with
a star-filled unbound space.1605 Johannes Kepler discovers
that orbits are elliptical.1610 Galileo Galilei discovers
the phases of Venus, and
Jupiter’s moons, strengthening
the heliocentric viewpoint.Of all discoveries and
opinions, none may have
exerted a greater effect on
the human spirit than the
doctrine of Copernicus.
Johann von GoetheNicolaus Copernicus Nicolaus Copernicus was born in
Torun, Poland, in 1473. From 1491
to 1495, he studied mathematics,
astronomy, and philosophy at the
University of Kraków, then from
1496, canon (religious) law and
astronomy at the University of
Bologna, Italy. In 1497, he was
appointed canon of the cathedral
of Frombork, Poland, a post he
retained for life. From 1501 to
1505, he studied law, Greek,
and medicine at the University
of Padua, Italy. Subsequently,
he returned to Frombork, where
he spent much of the rest of his
life. By 1508, he had begundeveloping his sun-centered
model of the universe. He did
not complete this work until
1530, although he did publish
a summary of his ideas in- Realizing that he risked
being ridiculed or persecuted,
Copernicus delayed publishing
the full version of his theory
until the last weeks of his life.
Key works1514 Commentariolus
1543 De revolutionibus orbium
coelestium (On the Revolutions
of the Celestial Spheres)