Most of us are familiar with the fact that Galileo was brought to trial and censored by the church for promoting the view that the earth revolves around the sun. This trial is often viewed as a conflict between Christian faith and science. However, the situation was much more complicated than that.

In 1962 Thomas Kuhn wrote a very influential book entitled The Structure of Scientific Revolutions. In this book he describes how, historically, science has not followed a straight line path of gradual improvement, but instead there have been normal periods where science operates under a structure of shared assumptions and approaches to problems called a paradigm that in due time is interrupted by a revolutionary paradigm shift. A paradigm shift represents a radically different way of thinking about the world. It usually involves more than the rejection of a single idea, but instead it involves changes in multiple interconnected ideas. Initially the new paradigm is vigorously resisted while support for the new paradigm is being developed. Eventually there follows a new normal period where the new paradigm prevails.

Galileo was part of a major paradigm shift. Prior to the 16th century the scientific view of the universe was based primarily on the ideas of Aristotle (384–322 B.C.) and the later refinements of these ideas by Ptolemy (c.85–165 A.D.). They assumed among other things that the earth was stationary and was the center of the universe. The sun, moon, and the other planets were assumed to revolve around the earth. They also believed that the moon and everything beyond were part of a perfect, unchanging region where all the stars and planets were composed of a special weightless material called aether, unlike anything found on earth.

This way of viewing the universe was commonly accepted for almost 2000 years. Although we now know that most of the ideas of Aristotle and Ptolemy about the universe we live in were wrong, there were very powerful common-sense arguments for believing them at the time. The first real challenge to the Aristotelian view was presented by Copernicus. Nicolas Copernicus (1473–1543) developed a model for the solar system in which the earth and the other planets orbited around the sun. Although the model he developed was as complicated as that of Ptolemy and was no more accurate, it did provide better explanations of certain features. This stimulated other scientists to think about better ways of describing the heavens.

Galileo was a supporter of the Copernican view and offered several pieces of evidence against the Aristotelian viewpoint. Using the recently invented telescope he observed such things as mountains on the moon, several moons orbiting Jupiter, sun spots, and phases of Venus. Although these observations were not sufficient to completely overthrow the current paradigm, they did present significant problems for the Aristotelian viewpoint.

However, there still remained a number of common-sense objections to a sun-centered system such as

  • Why don't we feel like we are moving?
  • Why don't we feel a wind as we move through the air?
  • Why don't objects fly off a rotating earth?
  • What is powerful enough to move the earth and keep it moving?
  • Why don't we observe stellar parallax if we orbit the sun? (we'll talk about stellar parallax in more detail later on)

These objections were eventually answered, but it took a new formulation of physics by Newton (1643–1727) and more accurate measurements to provide the answers.

As you can imagine, Galileo's advocacy of the Copernican model met stiff resistance both from the academic community and the church. If anything, the resistance from the academic community was the stronger of the two. Galileo had a number of backers within the church community, but very few in the academic community. The resistance from the church stemmed from the fact that Thomas Aquinas (1225–1274) had incorporated many of Aristotle's views into a Christian theology that became part of official church doctrine. This theology was consistent with several passages in the Bible that seemed to support an earth-centered view.

The church didn't object to a sun-centered model of the universe as long as it was treated as a computational tool and was not presented as representing reality. On the other hand, members of the academic community saw this paradigm shift as a threat to the cherished beliefs on which their careers were founded.

In this paper we will look at the reason's behind the long tenure of the Aristotelian viewpoint as well as the work of Copernicus, Galileo, Kepler, Brahe, and Newton that eventually lead to its downfall. We will also look at the trial of Galileo and some of the events that led up to it. Finally, we will see how the Christian church eventually modified its interpretation of certain passages of scripture that seemed to support a stationary earth. It was realized that the language used in these passages didn't have to be taken literally, but could be interpreted in a poetic or phenomenological manner. The paradigm shift brought about changes in both science and Christian theology. In both cases the changes were resisted initially but eventually converged toward a peaceful solution.

The events described in this paper played an important part in the development of science. From this bit of history we can learn valuable lessons on the nature of science and its proper interpretation.

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