Nicolaus Copernicus (in
Latin; Polish: Mikołaj Kopernik; German: Nikolaus Kopernikus; February
19, 1473 – May 24, 1543) was a Polish astronomer, mathematician
and economist who developed the heliocentric (Sun-centered) theory of
the solar system in a form detailed enough to make it scientifically
useful. His main occupations and services rendered were in Royal
Prussia, as church canon, governor and administrator, economist, jurist,
physician, astrologer and military leader (conducting defense against
the Teutonic Order). Amid all his responsibilities, he treated astronomy
as one would a hobby. His theory about the Sun as the center of the
Universe, opposed to the traditional geocentric theory that placed Earth
at the center, is considered one of the most important discoveries ever,
and is the fundamental starting point of modern astronomy and modern
science itself (it inaugurated a scientific revolution). His theory
affected many aspects of human life, opening the door for young
astronomers, scientists and scholars to take a skeptical attitude toward
Copernicus was born in 1473 at Toruń (Thorn) in Polish Royal
Prussia. His father Nikolas, a citizen of Kraków (Cracow), then capital
of Poland, had moved to Toruń in 1460 once the war with the Teutonic
Knights was concluded, and had become a respected citizen of that city.
Copernicus was ten when his father, a wealthy businessman and copper
trader, died. Little is known of his mother, Barbara Watzenrode, who
appears to have predeceased her husband. Copernicus' maternal uncle,
Lucas Watzenrode, a church canon and later Prince-Bishop governor of
Warmia, reared him and his three siblings after the death of Copernicus'
father. Copernicus' brother Andreas became a canon at Frombork (Frauenburg).
A sister, Barbara, became a Benedictine nun, and the other sister,
Katharina, married a businessman and city councillor, Barthel Gertner.
In 1491 Copernicus enrolled at the Jagiellonian University in Kraków,
and here for the first time encountered astronomy, thanks to his teacher
Albert Brudzewski. This science soon fascinated him, as shown by his
books (later carried off as war booty by the Swedes during The Deluge,
and now at the Uppsala University Library). After four years at Kraków,
followed by a brief stay at Toruń, he went to Italy, where he studied
law and medicine at the universities of Bologna and Padua. His
bishop-uncle financed his education and wished for him to become a
bishop as well. However, while studying canon and civil law at Ferrara,
Copernicus met the famous astronomer, Domenico Maria Novara da Ferrara.
Copernicus attended his lectures and became his disciple and assistant.
The first observations that Copernicus made in 1497, together with
Novara, are recorded in Copernicus' epochal book, De revolutionibus
In 1497 Copernicus' uncle was ordained Bishop of Warmia, and Copernicus
was named a canon at Frombork (Frauenburg) Cathedral, but he waited in
Italy for the great Jubilee of 1500. Copernicus went to Rome, where he
observed a lunar eclipse and gave some lectures in astronomy or
He would thus have visited Frombork only in 1501. As soon as he arrived,
he requested and obtained permission to return to Italy to complete his
studies at Padua (with Guarico and Fracastoro) and at Ferrara (with
Bianchini), where in 1503 he received his doctorate in canon law. It has
been supposed that it was in Padua that he encountered passages from
Cicero and Plato about opinions of the ancients on the movement of the
Earth, and formed the first intuition of his own future theory. His
collection of observations and ideas pertinent to his theory began in
Having left Italy at the end of his studies, he came to live and work at
Frombork. Some time before his return to Warmia, he had received a
position at the Collegiate Church of the Holy Cross in Wrocław
(Breslau), Silesia, which he would resign a few years before his death.
Through the rest of his life he made astronomical observations and
calculations, but always in his spare time and never as a profession.
Copernicus worked for years with the Prussian diet on monetary reform
and published some studies about the value of money; as governor of
Warmia, he administered taxes and dealt out justice. It was at this time
(beginning in 1519, the year of Thomas Gresham's birth) that Copernicus
came up with one of the earliest iterations of the theory now known as
Gresham's Law. During these years he also traveled extensively on
government business and as a diplomat, on behalf of the Prince-Bishop of
In 1514 he made his Commentariolus — a short handwritten text describing
his ideas about the heliocentric hypothesis — available to friends.
Thereafter he continued gathering evidence for a more detailed work.
During the war between the Teutonic Order and the Kingdom of Poland
(1519–1524) Copernicus successfully defended Allenstein (Olsztyn) at the
head of royal troops besieged by the forces of Albert of Brandenburg.
In 1533 Albert Widmanstadt delivered a series of lectures in Rome
outlining Copernicus' theory. By 1536 Copernicus' work was already in
definitive form, and some rumors about his theory had reached scientists
all over Europe. From many parts of the continent, Copernicus received
invitations to publish, but he feared persecution for his revolutionary
work by the establishment. Cardinal Nicola Schoenberg of Capua wrote,
asking him to communicate his ideas more widely and requesting a copy
for himself; "Therefore, learned man, without wishing to be inopportune,
I beg you most emphatically to communicate your discovery to the learned
world, and to send me as soon as possible your theories about the
Universe, together with the tables and whatever else you have pertaining
to the subject." Some have suggested that this note may have made
Copernicus leery of publication, while others have suggested that the
Church wanted to ensure that his ideas were published.
Copernicus was still completing his work (even if he was not convinced
that he wanted to publish it) when in 1539 Georg Joachim Rheticus, a
great mathematician from Wittenberg, arrived in Frombork. Philipp
Melanchthon had arranged for Rheticus to visit several astronomers and
study with them. Rheticus became a disciple of Copernicus' and stayed
with him for two years, during which he wrote a book, Narratio prima,
outlining the essence of the theory.
In 1542, in Copernicus' name, Rheticus published a treatise on
trigonometry (later included in the second book of De revolutionibus).
Under strong pressure from Rheticus, and having seen that the first
general reception of his work had not been unfavorable, Copernicus
finally agreed to give the book to his close friend Tiedemann Giese,
bishop of Chełmno (Kulm), to be delivered to Rheticus for printing at
Legend says that the first printed copy of De revolutionibus was placed
in Copernicus' hands on the day he died, so that he could take farewell
of his opus vitae. He supposedly woke from a stroke-induced coma, looked
at his book, and died peacefully.
Copernicus was buried in Frombork Cathedral. Archeologists searching for
his remains had failed to locate them, though they had found interesting
graves from various periods. On November 3, 2005, archeologists
announced that in August they had recovered Copernicus' skull.
The Copernican heliocentric system
Much has been written about earlier heliocentric theories. Philolaus
(4th century BC) was one of the first to hypothesize movement by the
Earth, probably inspired by Pythagoras' theories about a spherical
Aristarchus of Samos in the 3rd century BC had developed some theories
of Heraclides Ponticus (speaking of a revolution by Earth on its axis)
to propose what was, so far as is known, the first serious model of a
heliocentric solar system. His work about a heliocentric system has not
survived, so one may only speculate about what led him to his
conclusions. It is notable that, according to Plutarch, a contemporary
of Aristarchus accused him of impiety for "putting the Earth in motion."
Indian mathematicians, astronomers and physicians, most notably
Aryabhata and Bhaskara I, also anticipated Copernicus' discoveries, by
about 1,000 years. The work of the 14th-century Muslim astronomer Ibn
al-Shatir contains findings similar to Copernicus', and it has been
suggested that Copernicus might have been influenced by them.
Copernicus cited Aristarchus and Philolaus in an early manuscript of his
book which survives, stating: "Philolaus believed in the mobility of the
earth, and some even say that Aristarchus of Samos was of that opinion."
For reasons unknown, he struck this passage before publication of his
Inspiration came to Copernicus not from observation of the planets, but
from reading two authors. In Cicero he found an account of the theory of
Hicetas. Plutarch provided an account of the Pythagoreans Heraclides
Ponticus, Philolaus, and Ecphantes. These authors had proposed a moving
earth that revolved around a central sun. Copernicus did not attribute
his inspiration to Aristarchus as is sometimes stated. When Copernicus'
book was published, it contained a preface by the Lutheran theologian
Andreas Osiander. This cleric stated that Copernicus wrote his
heliocentric account of the earth's movement as a mere mathematical
hypothesis, not as an account that contained truth or even probability.
Copernicus' hypothesis contradicted the account of the sun's movement
around the earth that appears in the Old Testament (Joshua 10:13).
The Ptolemaic system
The prevailing theory in Europe as Copernicus was writing was that
created by Ptolemy in his Almagest, dating from about 150 A.D.. The
Ptolemaic system drew on many previous theories that viewed Earth as a
stationary center of the universe. Stars were embedded in a large outer
sphere which rotated relatively rapidly, while the planets dwelt in
smaller spheres between — a separate one for each planet. To account for
apparent anomalies to this view, such as the retrograde motion observed
in many planets, a system of epicycles was used, by which a planet
rotated on a small axis while also rotating on a larger axis around the
Earth. Some planets were assigned "major" epicycles (by which retrograde
motion could be observed) and "minor" epicycles (which simply warped the
A complementary theory to Ptolemy's employed homocentric spheres: the
spheres within which the planets rotated, could themselves rotate
somewhat. Also popular with astronomers were variations such as
eccentrics — by which the rotational axis was offset and not completely
at the center — or that added epicycles to epicycles.
Ptolemy's unique contribution to this theory was the idea of an equant —
a complicated addition which specified that, when measuring the rotation
of the Sun, one sometimes used the central axis of the universe, but
sometimes one set at a different location. This had an overall effect of
making certain orbits "wobble," a fact that would greatly bother
Copernicus (such wobbling rendered implausible the idea of material
"spheres" in which the planets rotated). In the end, after all these
complications, the astronomers could still not get observation and
theory to match up exactly. In Copernicus' day, the most up-to-date
version of the Ptolomaic system was that of Peurbach (1423-1461) and
Copernicus' major theory was published in the book, De revolutionibus
orbium coelestium (On the Revolutions of the Heavenly Spheres) in the
year of his death, 1543, though he had arrived at his theory several
The book marks the beginning of the shift away from a geocentric (and
anthropocentric) universe with the Earth at its center. Copernicus held
that the Earth is another planet revolving around the fixed sun once a
year, and turning on its axis once a day. He arrived at the correct
order of the known planets and explained the precession of the equinoxes
correctly by a slow change in the position of the Earth's rotational
axis. He also gave a clear account of the cause of the seasons: that the
Earth's axis is not perpendicular to the plane of its orbit. He added
another motion to the Earth, by which the axis is kept pointed
throughout the year at the same place in the heavens; since Galileo
Galilei, it has been recognized that for the Earth not to point to the
same place would have been a motion.
Copernicus also replaced Ptolemy's equant circles with more epicycles.
This is the main source of the statement that Copernicus' system had
even more epicycles than Ptolemy's. With this change, Copernicus' system
showed only uniform circular motions, correcting what he saw as the
chief inelegance in Ptolemy's system. But while Copernicus put the Sun
at the center of the celestial spheres, he did not put it at the exact
center of the universe, but near it.
Copernicus' system was not experimentally better than Ptolemy's model.
Copernicus was aware of this and could not present any observational
"proof" in his manuscript, relying instead on arguments about what would
be a more complete and elegant system. From publication until about
1700, few astronomers were convinced by the Copernican system, though
the book was relatively widely circulated (around 500 copies are known
to still exist, which is a large number by the scientific standards of
the time). Many astronomers, however, accepted some aspects of the
theory at the expense of others, and his model did have a large
influence on later scientists such as Galileo and Johannes Kepler, who
adopted, championed and (especially in Kepler's case) sought to improve
it. Galileo's observation of the phases of Venus produced the first
observational evidence for Copernicus' theory.
The Copernican system can be summarized in seven propositions, as
Copernicus himself collected them in a Compendium of De revolutionibus
that was found and published in 1878:
1. Orbits and celestial spheres do not have a unique, common, center.
2. The center of the Earth is not the center of the Universe, but only
the center of the Earth's mass and of the lunar orbit.
3. All the planets move along orbits whose center is the Sun, therefore
the Sun is the center of the World. (Copernicus was never certain
whether the Sun moved or not, claiming that the center of the World is
"in the Sun, or near it.")
4. The distance between the Earth and the Sun, compared with the
distance between the Earth and the fixed stars, is very small.
5. The daytime motion of the Sun is only apparent, and represents the
effect of a rotation that the Earth makes every 24 hours around its
axis, always parallel to itself.
6. The Earth (together with its Moon, and just like the other planets)
moves around the Sun, so the motions that the Sun seems to be making
(its apparent motion during the daytime, and its annual motion through
the Zodiac) are nothing else than effects of the Earth's actual motions.
7. These motions of the Earth and of the other planets around the Sun,
can explain the stations, and all the particular characteristics of the
Whether these propositions were "revolutionary" or "conservative" was a
topic of debate in the late twentieth century. Thomas Kuhn argued that
Copernicus only transferred "some properties to the sun many
astronomical functions previously attributed to the earth." Other
historians have since argued that Kuhn underestimated what was
"revolutionary" about Copernicus' work, and emphasized the difficulty
Copernicus would have had in putting forward a new astronomical theory
relying alone on simplicity in geometry, given that he had no
De revolutionibus orbium coelestium
Copernicus' major work, On the Revolutions of the Heavenly Spheres
(1543), was the result of decades of labor. It opened with an originally
anonymous preface by Andreas Osiander, a theologian friend of
Copernicus, who urged that the theory did not necessarily have
implications outside the limited realm of astronomy. Copernicus' actual
book began with a letter from his (by then deceased) friend, the
Archbishop of Capua, urging Copernicus to publish his theory. Then, in a
lengthy introduction, Copernicus dedicated the book to Pope Paul III,
explaining his ostensible motive in writing the book as relating to the
inability of earlier astronomers to agree on an adequate theory of the
planets, and noting that if his system increased the accuracy of
astronomical predictions it would allow the Church to develop a more
accurate calendar (calendar reform then being an important question and
one of the major reasons for Church funding of astronomy).
The work itself was then divided into six books.
The first book comprises a general vision of the heliocentric theory,
and a summarized exposition of his idea of the World.
The second book is mainly theoretical and presents the principles of
spherical astronomy and a list of stars (as a basis for the arguments
developed in the subsequent books).
The third book is mainly dedicated to the apparent motions of the Sun
and to related phenomena.
The fourth book gives a similar description of the Moon and its orbital
The fifth and sixth books comprise a concrete exposition of the new