AP European History

Chapter 14: New Directions in Thought and Culture in the Sixteenth and Seventeenth Centuries Notes Nicolaus Copernicus Rejects an Earth-Centered Universe

Biographical information

Polish priest and scientist

educated at the University of Krakow

wrote On the Revolutions of the Heavenly Spheres in 1543

Commissioned to find astronomical justification so that the papacy could change the calendar so that it could correctly calculate the date of Easter, Copernicus’s work provided an intellectual springboard from which scientist could posit questions about Earth’s position in the universe. Ptolemaic System

Ptolemy, a Roman citizen of Greek ancestry, wrote the Almagest (150CE) was considered the authority on astronomy throughout the Middle Ages and it suggested a geocentric model of the universe. Ptolemaic World System

Above the earth lay a series of concentric spheres, probably fluid in character, one of which contained the moon, another the sun, and still others the planets and the stars. The outer realm contains God and angels

The problem of the motions of the planets was something astronomers struggled to chart. Ptolemy believed that the planets moved uniformly about a small circle called an epicycle and the center of the epicycle moved about a larger circle—called a deferent—with the earth at or near its center. The circles in Ptolemy’s system were not orbits but rather components of mathematical calculations meant to predict planetary positions. Copernicus’s Universe

Copernicus’s Model adopted many elements in the Ptolemaic model, but transferred them to a heliocentric model, which assumed the earth moved about the sun in a circle. He proposed that the farther planets are away from the sun, the longer they took to revolve around it which enabled astronomers to rank the planets in terms of distance from the sun. Although very few astronomers embraced the Copernican system—at least for a century—it did allow other people who were not satisfied with the Ptolemaic view to think in new directions.

Tycho Brahe (1546-1601) and Johannes Kepler (1571-1630) Make New Scientific Observations Brahe’s contributions to science

He did not believe Copernicus’s view and spent much of life advocating for a geocentric system. He posited that Mercury and Venus revolved around the sun but that the moon, the sun, and other planters revolved around the earth. He collected very detailed data of his observations.

Kepler’s contributions to science

He studied under Brahe and was given his data when he died.

Kepler, unlike Brahe was a convinced Copernican who found mathematical proof of a sun-centered universe. He found that in order for heliocentrism to be true, planets must have an elliptical, rather than circular orbiti. Kepler published his findings in a book called The New Astronomy (1609) in which he used Copernicus’s sun-centered model and Brahe’s empirical data to solve the problem of planetary motion. Galileo Galilei Argues For A Universe of Mathematical Laws

In 1609, he used a recently invented telescope to observe the skies and he saw stars where none had been before, mountains on the moon, spots moving across the sun, and moons orbiting Jupiter. In The Starry Messenger (1610) and Letters on Sunspots (1613), he used his rhetorical skills to argue that his new evidence—particularly in the phases of Venus—required a Copernican interpretation of the heavens. Galileo taught at the University of Padua before being hired by the Grand Duke of Tuscany, who was a Medici. He popularized the Copernican system and articulated the concept of a universe subject to mathematical laws. Copernicus had thought that the heavens conformed to mathematical regularity; Galileo saw this regularity throughout all physical nature. For many people, the power of the mathematical arguments that appeared irrefutable proved more persuasive than the new information from physical observation that produced so much...