Nicolaus Copernicus

Nicolaus Copernicus

Nicolaus Copernicus presented an alternative model of the universe that broke with that proposed by Ptolemy in the second century c.e. and thus with the prevailing assumptions of astronomers in his own time. Although he did no observations and lacked advanced mathematical skill, he nonetheless ushered in the “new” science and physics of Galileo and Isaac Newton.

The Latinized name Copernicus belonged to the man born in Torun, Poland, as Mikolaj Kopernik. His wealthy merchant father died when his son was only 10 or 11 years old; Copernicus spent his youth in the household of his maternal uncle, Lucas Waczenroade, who was also bishop of Ermeland.

He therefore received a good education that enabled him to succeed when he went on to the University of Krakow in 1491. He developed an interest in astronomy while in Krakow, but he instead pursued law and medicine while in Bologna and Padua. He became a doctor of canon law in 1503.

His participation in the broader humanist movement was made manifest by his 1519 publication of his translation from the Greek into Latin of letters by a seventh-century Byzantine poet. His uncle appointed him canon at Frombork Cathedral in 1503, but Copernicus did not reestablish residency in Poland until 1506. He served his uncle as secretary and physician until the bishop died in 1512.


Thereafter, Copernicus devoted his time to astronomy, along with his responsibilities as canon, physician, and local mathematician. In the latter capacity, he developed a plan for currency reform. He also took command of a castle at Allenstein in 1520 after the Teutonic Knights invaded the region.

Copernicus did not at first widely disseminate the ideas that later made him famous, even though he had developed them by 1510. His doubts about the Ptolemaic model of the universe focused on a few weak points that had also been identified by other astronomers. First, the Ptolemaic system required the Moon’s orbit to be offset from the Earth to explain apparent variations in the speed of the Moon’s motion around the Earth.

The magnitude of this offset would entail equally dramatic variations in the apparent size of the Moon, dependent on its distance from the Earth. No observer had witnessed anything of the kind. Second, Copernicus disliked the complexity and incoherence of Ptolemy’s model.

He expected that a single principle governed the organization of the universe, whereas Ptolemy dealt with each planet, the Sun, and the Moon individually and gave each body its own epicycles and own offset from the Earth. Copernicus aspired to formulate a far more elegant model that would better evidence the unity of what he believed to be God’s creation.

Shortly after he first became interested in astronomy, Copernicus read a book published by German natural philosopher Johannes Mueller, known as Regiomontanus. Regiomontanus published Epitome in 1496. In this work, he provided a summary of the Almagest, included new observational data, and added critical textual commentary. For example, he highlighted the dilema of the Ptolemaic model with regard to the apparent size of the Moon.

Copernicus circulated his own model among close friends soon after 1510 in the form of a manuscript, called Commentariolus. It attracted the interest of various astronomers, and it was mentioned by papal secretary Johan Widmanstadt in a lecture at the Vatican given to an audience that included the pope and cardinals.

Cardinal Nicholas von Schönberg requested that Copernicus publish his ideas; his letter was reproduced at the beginning of Copernicus’s De revolutionibus orbium coelestium (On the Revolution of the Celestial Spheres), published in 1543.

Copernicus remained somewhat dissatisfied with his model; that may in part explain his reluctance to publish. Although placing the Sun at the center and arranging the orbits of the planets around it had several advantages (for example, it accounted for observations of the planets and allowed estimates of their distance from each other), it did not completely satisfy his desire for unity and order.

Nicolaus Copernicus Statue

The Moon orbited around the Earth, for instance. Also, he could not explain the seeming acceleration and deceleration of planets in their orbits because he assumed that orbits were perfectly circular (rather than elliptical) and that the universe could have an exact center.

Further, Copernicus continued to believe that the stars were fastened upon a crystalline sphere beyond the spheres that carried the planets. If the Earth was moving, he and other astronomers anticipated that an observer on Earth should see the stars appear to move.

The absence of the so-called parallax effect results from the fact that the stars lie thousands of times farther than the outermost planet, such that the parallax is too small to be seen by all but the most careful observers using sophisticated telescopes not available until the 19th century at the earliest. Last, Copernicus offered no explanation for why people on Earth perceive no evidence that the planet constantly moves, such as a wind.

After much hesitation and work on other tasks, Copernicus yielded to the request of mathematics professor Georg Joachim von Lauchen (called Rheticus), who arrived at Frombork in spring 1539 to meet with him. He agreed to allow Rheticus oversee the publication of his work.

Rheticus published First Account of the Revolutionary Book by Copernicus in 1540, but he left his post at Wittenberg for one at Nuremberg before he could complete preparations for De revolutionibus. Rheticus left the project to Andreas Osiander, whose unsigned preface made explicit that Copernicus offered a model, not an assertion of fact.

Osiander, a Lutheran minister, would have known that Martin Luther had condemned the notion of a Sun-centered universe as contrary to the cosmology hinted at in the Bible. Leaders of the Roman Catholic Church expressed no concerns about the theory at the time, however.

Published Work

Copernicus died before he could read the published version of his book. De revolutionibus did not have many readers, in fact: All of its first edition of 400 copies did not sell. In England, an astronomer by the name of Thomas Digges discussed the Copernican model in his book of 1576, but the theory did not gain much additional attention until the declared heretic Giordano Bruno was executed in 1600.

Bruno subscribed to an assortment of heterodox beliefs and to the cult of Hermes Trismegistus, which worshiped the Sun; he claimed that the Egyptian religion was the true faith. Bruno also happened to believe in the Copernican model of the universe, a circumstance that may have brought the idea into disfavor with the church in a form of guilt by association. The Vatican placed De revolutionibus on the Index of Forbidden Books in 1616 (it was removed in 1835).

When Johannes Kepler derived his laws of planetary motion after postulating a Sun-centered universe and after Galileo defended the theory as a description of reality and confronted the church with new evidence, Copernicus’s ideas began to exercise an important influence on the course of scientific inquiry. As with any useful theory, that of Copernicus directed research in particular directions and could be tested by observation.