Nicholas Copernicus proposed a revolutionary heliocentric model of the solar system where the Sun, not the Earth, was at the center. In 1543, just before his death for fear of persecution, Copernicus published his book "On the Revolutions of the Heavenly Spheres" which put forth his heliocentric theory. Though it contradicted the widely accepted geocentric model of Aristotle and Ptolemy, Copernicus' proposal that the planets revolved around the Sun was a major breakthrough, though not fully accepted until improved upon later.

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NICHOLAS COPERNICUS’ HELIOCENTRISM
Cosmic Adventure 3.05

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The Geocentric Universe
Ancient astronomers thought that the earth was the center of the
universe. The other heavenly bodies—the sun, moon, planets, and stars—
all moved round the earth. This geocentric theory of the universe has a
long history.
It was authorized by Aristotle in
ancient Greece and was fully
supported and documented by
the famous astronomer Ptolemy
in the 2nd century AD. It was
unanimously accepted by most
people, particularly the religious
leaders who made a doctrine
out of it.

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Nicholas Copernicus
After 1,300 years of popular
acceptance, the theory of an
earth-centered universe began
to meet its challenge in the
16th century. The man who
started the demolition work of
the misconception was named
Nicholas Copernicus (1473-
1543), a Renaissance Polish
lawyer-astronomer and
Catholic cleric.

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Published upon Death
Copernicus was known for his great
contribution to science is his critical
reappraisal of the existing theories of
cosmology and the development of a
new model of the solar system.
In 1543, Copernicus published his
book called “De revolutionibus orbium
coelestium libri VI” (“Six Books
Concerning the Revolutions of the
Heavenly Orbs”). This was the year of
his death for fear of persecution by
the Church.

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Copernican Revolution
The main aim of the book was
to expound and promote the
heliocentric system. He said
that it was the sun, not the
earth, that was the center of
our universe. Copernicus still
thought the planets orbited the
sun in perfect circles like
Aristotle and Ptolemy. But the
fact that he put the sun at the
center was a revolutionary idea
in the astronomy of the time.

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But people were so entrenched in
the prevalent geocentric concept
that they found the heliocentric
idea unacceptable.

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The Church also began to find the idea revoking and classified it as a
heresy. Thus the new theory was opposed mainly on religious grounds.
That’s also why the theory was released only after Copernicus’s death.
The geocentric universe The heliocentric universe

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THE ELLIPTICAL ORBITS OF
JOHANNES KEPLER
To be continued in Cosmic Adventure 3.06