Astronomy of the Middle Ages

Ptolemy's Universe

Since ancient times, Astronomy was an important field of study and part of the Quadrivium, studied by all University students. Until the 15th century, Ptolemy's model of a geocentric Universe, incorporating all astronomical research and measurements noted until up to the 2nd century, was considered a reliable guide for mariners, travelers, and astronomers alike. The idea of a heliocentric universe had been proposed in ancient times (Aristarchus of Samos, 250 B.C.) but ancient astronomers objected on the grounds that no parallax shift in the location of the stars was visible over the course of a year. The ancients well understood the mathematics of using trigonometry to estimate distances, but could detect no shift in the stars location that would indicate movement of the earth relative to the sun, so they ruled out a heliocentric model based on the best science of the day.

Buridan to Copernicus (1340-1540)

By the Middle Ages, interest in astronomical studies re-emerged, especially in the monasteries and universities. During the 14th and 15th centuries, various philosophers made proposals regarding the nature of the Universe and the motion of planets, but many theories relating to the motion of planets and celestial objects were merely speculation since there were not obvious ways to prove one's theory. The custom was to discuss possibilities without drawing conclusions or directly contradicting scriptures. The church saw now harm in theories, even outlandish ones, as long as they were not presented as fact. In the early 14th century, 200 years before Newton revolutionized the science of astronomy, Jean Buridan and Albert of Saxony proposed the idea of impetus (a concept similar to Newton's inertia), to explain the movement of planets. Soon after Nicholas Oresme proposed that the earth spun on its access and provided some important proofs, while Nicholas of Cusa proposed the possible existence of other worlds and a non-geocentric universe. All of these ideas were discussed and debated openly without being restricted by the Catholic Church.

In 1543, in an atmosphere of open scientific dialogue, Copernicus published "On the Revolution of Heavenly Spheres" promoting his theory of a heliocentric universe. His work was mathematical, intended for scholars rather than the general public, and was received without particular controversy. It was not until 70 years during the Galileo controversy that the book was held to be controversial and placed on the list of Forbidden books.

Tycho Brahe to Newton (1580-1680)

In the 70 years between Copernicus and Galileo, telescope technology improved considerably, and it was the largely the ability to see moons orbiting other planets in the solar system that made Galileo certain that the Copernican model was correct, even though there were numerous unresolved problems with it. (Copernicus failed to explain the problem of parallax, and his circular orbits were inaccurate). The Galileo controversy has been blown out of proportion by anti-Catholic historians. The real story of Astronomy owes much more to the efforts of Tycho Brahe, and Kepler, both contemporaries of Galileo, than it does to the controversialist.

While Galileo was stirring up trouble and controversy, and polarizing the entire field of Astronomy, Kepler and Brahe worked quietly in Prague, making meticulous and extremely accurate measurements of planetary motion over thirty years that proved indispensable to Newton several generations later. Kepler started his career as an assistant to Brahe, but while Brahe sought to combine both the Copernican and Ptolemaic models to create a hybrid system (the planets orbit the sun, but the sun orbits a stationary earth), Kepler used the highly accurate data to propose a Copernican-like system with elliptical rather than circular orbits. Kepler's master work, "The New Astronomy" was published in 1609. It was a much improved version of the Copernican theory. This time without the problems presented by circular orbits, and with the benefit of a great deal of new observational data.

It was largely Kepler's work that inspired the landmark studies of Isaac Newton, but the contributions of other Catholic scholars were also very important. Buridan proposed that motion of Planets was self-sustaining; Oresme proposed rotating planets; several thinkers had proposed that outer space was a frictionless, Jean Picard had created methods of measuring the earth to an extreme degree of accuracy, and Riccioli had accurately measured the acceleration of gravity. But no one had the audacity to assert that the exact same force of gravity that controlled the motion of earthly objects also operated in space. It was a radical theory, but Kepler's measurements were accurate enough to prove the theory was sustainable and predict precisely the elliptical orbits observed. The whole idea of "universal" laws that effected all matter at all time was positively earth-shaking, and was the true engine of the Scientific revolution.

After Newton (1700+)

The reason Newton's laws of universal gravitation, and mathematical representations of force, mass, acceleration, and momentum were so important was that they now provided a framework within which other abstract quantities, such as pressure, and temperature could be measured and understood. The certainty that all mass, whether in liquid or solid form, whether a rock or a planet, was subject to physical laws, opened the door to sustained and systematic scientific investigation.

In the centuries after Newton's discoveries, Catholic scientists, especially Jesuits, continued to make remarkable discoveries. Even up to the 20th century, Cleric-scientists have contributed enormously to the understanding of the solar system. In 1927 a Belgian priest proposed that the Universe originated with a 'Big Bang' whose radioactive footprint was still visible. Although scorned by many of the scientists of his day, including Einstein, Lemaitre has been proven right.