Nicholas Copernicus was born into a well-to-do family on February 19, 1473. His father, a copper merchant, died when Copernicus was ten, and the boy was taken in by an uncle who was a prince and bishop.
Copernicus was well able to afford a good education. He entered the University of Cracow in 1491 and studied mathematics and painting. In 1496 he went to Italy for ten years where he studied medicine and religious law. Two things happened in the year 1500 that influenced Copernicus: he attended a conference in Rome dealing with calendar reform and, on November 6, 1500, witnessed a lunar eclipse.
The tables of planetary positions that were in use at the time were very complex and inaccurate. Predicting the positions of the planets over long periods of time was haphazard at best, and the seasons were out of step with the position of the Sun. Copernicus realized that tables of planetary positions could be calculated much more easily, and accurately, if he made the assumption that the Sun, not the Earth, was the center of the solar system and that the planets, including the Earth, orbited the Sun. He first proposed this theory in 1507.
Copernicus was not the first person to introduce such a radical concept. Aristarchus had come up with the idea in ancient Greece long before, but the teachings of Ptolemy had been dominant for 1,300 years. Ptolemy claimed the Earth was at the center of the universe, and all the planets (including the Sun and Moon) were attached to invisible celestial spheres that rotated around the Earth.
Copernicus not only wished to refute Ptolemy's universe, he claimed that the Earth itself was very small and unimportant compared to the vast vault of the stars. This marked the beginning of the end of the influence of the ancient Greek scientists.
Copernicus was not an especially good astronomical observer. It is said he never saw the planet Mercury (which never gets very far from the Sun), and he made an incorrect assumption about planetary orbits--he decided they were perfectly circular. Because of this, he found it necessary to use some of Ptolemy's cumbersome epicycles (smaller orbits centered on the larger ones) to reduce the discrepancy between his predicted orbits and those observed. It wasn't until Johannes Kepler 's time that this was corrected and the true nature of planetary orbits was understood.
Even so, the heliocentric model developed by Copernicus fit the observed data better than the ancient Greek concept. For example, the periodic "backward" motion (called retrograde motion) in the sky of the planets Mars, Jupiter, and Saturn and the lack of such motion for Mercury and Venus was more readily explained by the fact that the former planets' orbits were outside the Earth's. Thus, the Earth "overtook" them as it circled the Sun. Planetary positions could also be predicted much more accurately using Copernicus 's model.
Copernicus was very reluctant to make his ideas public. He fully realized his theory not only contradicted the Greek scientists, it went against the teachings of the Church, the consequences of which would be at best severe, and at worst mortal. In 1530 he allowed a summary of his ideas to circulate among scholars, who received it with great enthusiasm, but it was not until just shortly before his death in 1543 that his entire book was published. It took the efforts of the mathematician Rheticus to convince Copernicus to grant him permission to print it. Unfortunately, Rheticus had fallen afoul of official doctrine himself, and found it wise to leave town. Overseeing the publication for Copernicus's book was transferred to the hands of a Lutheran minister named Andreas Osiander (1498-1552).
Osiander now found he was in a tight spot; Martin Luther (1483-1546) had come out firmly against Copernicus' new theory, and Osiander was obligated to follow him. "This Fool wants to turn the whole Art of Astronomy upside down," Luther had said. Copernicus had dedicated his book to Pope Paul III, perhaps to gain favor, but Osiander went one step further; he wrote a preface in which he stated the heliocentric theory was not being presented as actual fact, but just as a concept to allow for better calculations of planetary positions. He did not sign his name to the preface, making it appear that Copernicus had written it and was debunking his own theory. Copernicus, suffering from a stroke and close to death, could do nothing to defend himself. It is said he died only hours after seeing the first copy of the book. (Kepler discovered the truth about the preface in 1609 and exonerated Copernicus.)
The immediate reaction to the book, De Revolutionibus Orbium Coelestium (Revolution of the Heavenly Spheres), was subdued. This was primarily due to Osiander's preface which weakened Copernicus' reputation. In addition, only a limited number of books were printed, they were very expensive and, consequently, had limited circulation. The book did achieve a number of converts, but one had to be a mathematician to fully understand the theories. Still, it was placed on the Roman Catholic Church's list of prohibited books where it remained until 1835.
Almost as significant as proving the heliocentric solar system was possible, was Copernicus's questioning of the ancient Greek scientists. Ptolemy had bent the facts to fit his preconceived theory and his teachings had been accepted, without question, for centuries. Copernicus, on the other hand, did his best to develop his theory to match observed facts. It was the dawning of modern scientific methods.