Science 122 Program 9 Darkness & Dawn

©1998 RCBrill. All rights reserved

Darkness & Dawn

Program 9
Lesson 2.1



1. Coming Up

2. Introduction

3. Romans

4. The Church

5. St. Augustine

6. Monasteries

7. Dark Ages

8. Arabic Influences

9. Rediscovery & Conflict

10. Critical Scholarship

11. St. Thomas Aquinas

12. Scholastic Cosmology

12. Renaissance

13. Cosmological and Philosophical Problems

14. Copernican Astronomy

15. Summary

Text References

Spielberg & Anderson 34-41
Booth & Bloom 45-49


1. In what way was the Roman approach to science different from the Classical Greeks and the Hellenistic Greeks.
2. How did the early Christians feel about the physical world.
3. What kinds of activities went on in Monasteries that contributed to the continuation of the Greek ideas?
4. What did St. Augustine (354-430) and St. Thomas Aquinas (1225-1274) do in relation to the growth of knowledge?
5. What factors necessitated reform of the Church dogma beginning around the 12th century?
6. What is Scholastic Philosophy?
7. What did the Arabic world contribute to the development of physical science in the middle ages?
8. Discuss the factors which led to the Renaissance of the 15th century.
9. What did Copernicus really do?
10. Compare and contrast the Copernican and Ptolemaic systems.
11. How was the heliocentric theory of Copernicus received by his contemporaries?
12. Who was Bruno and what were his crimes?


Here are the objectives for today's lesson. These objectives are also in the study guide at the beginning of the lesson.

Before you begin to study the lesson, take a few minutes to read the objectives and the study questions for this lesson.

Look for key words and ideas as you read. Use the study guide and follow it as you watch the program.

Some students find it helpful to make a note in the margin which pertains to a particular objective or a study question.

Be sure to read these objectives in the study guide and refer to them as you study the lesson.

Focusing on the learning objectives will help you to study and understand the important concepts.

Compare the objectives with the study questions for the lesson to be sure that you have the concepts under control.

1. Be prepared to write a brief and concise response to any of the questions at the beginning of this lesson.
2. Write a short essay which traces the influence of the following on the thread of scientific heritage:

1. The Roman Empire
2. Early Christians
3. St. Augustine
4. The Monasteries

3. Write a short essay which describes the role of the Middle East during the "dark ages."
4. Write a short essay which explains the contributions of St. Thomas Aquinas in the context of "The Nature of Science."
5. Write a short essay which characterizes the Renaissance, especially as it relates to scientific knowledge.
6. Write a short essay which campares and contrasts Copernican and Ptolemaic astronomy.

1. Coming Up

Before we're done with this program we will have traveled 1600 years down the river of heritage, from the Romans, through the rise of Christianity to the Dark Ages where the river is joined by a flow of information from the Middle East. After that the water becomes turbulent and a little muddy for awhile until the sediment settles out and the waters calm.

At the stage of the river known as the Renaissance the water begins to get deeper and clearer until finally we reach a major destination, the called Copernicus. We will look at the Copernican heliocentric world view and learn what Copernicus really said, how it was received by his contemporaries, and its subsequent effects.


2. Introduction

This is the first program in section two. The title of the section is "Revolution." In this part of the course we will study the scientific revolution, which involves not only turning the geocentric paradigm inside out, but also a whole new method of analysis and synthesis, using experimentation, deductive and inductive logic, mathematical formulation, really a different sort of way of looking at the world.

Today's program focuses on the growth of the Ptolemaic system, its incorporation into the dogma of the Church, and its eventual challenge by the parsimonious system of Copernicus.

Following the rise and fall of the Roman Empire, the concept of learning, logic and speculation changed in the Western world along with the spread of Christianity and Islam. The chaos that followed Rome's tight hold on Europe and the Mediterranean created a six hundred year period during which learning was discouraged. Learning consisted largely of studying the scriptures or the nature of man During this time learning virtually disappeared in Europe. The works of the ancients were closely guarded as they were read, copied and recopied generation after generation both in Europe and the Middle East.

In the Middle East learning was not so stifled. Rules of algebra were formulated, the decimal system along with Arabic numbers and the zero were introduced into mathematics, and star catalogs were improved with the addition of many new stars.

The rediscovery in Europe of works of Aristotle and Ptolemy impressed officials of the Church in their breadth, depth, and apparent truth. An effort was made to incorporate the cosmology of Aristotle and the astronomy of Ptolemy with the dogma of the Church, culminating in the publication of Summa Theologica by Thomas Aquinas.

Successful as St. Thomas was in incorporating Aristotle's cosmology into Church doctrine, and it was a major intellectual achievement, it was difficult to reconcile the geometry of Ptolemy with the cosmology of Aristotle. The predicted positions of the planets were far from agreement with those predicted by calculations performed according to the Ptolemaic prescription. And the Ptolemaic formulae themselves had been modified in unknown ways, intentionally or otherwise, having been bounced around in three different languages for one thousand years.

By the time of Copernicus, the calendar was off by some unknown amount and the seasons didn't occur at the right times, thereby affecting seasonal religious days such as Christmas and Easter, but also affecting the timing of planting and harvesting of crops.

Contrary to popular belief, the Church did not disapprove of the Copernican calculations. In fact the more accurate way of calculating the positions was welcomed by the Church, especially since Copernicus dedicated his book to the Pope and professed it to be only a model, not intended to represent reality. It was just a more convenient and more consistent way to predict the locations of the planets and to bring the calendar back into synch with the stars.

At the same time, the text of the book clearly shows that Copernicus had a preference for a cosmology as well as astronomy and a geometry which were all heliocentric, spherical and parsimonious.

Although the book was not published with the intention of starting a revolution, it provoked much thought and discussion half a century later.

3. Romans

The Romans picked up the pieces of the shattered Macedonian empire and controlled the Mediterranean by 200 B.C. Unlike the Greeks, for whom philosophy and metaphysics was an important part of the culture, the Romans were practical empire builders with only a casual interest in philosophy and natural law. Good engineers, the Romans were not good scientists and their role in the development of science would be minimal were it not for the influence exerted on the cultures on which they imposed themselves for six hundred and seventy five years before their own empire crumbled.

3.1. controlled Mediterranean by 200 B.C.
3.2. values different from Greeks
3.3. practical Empire builders
3.4. only casual interest in philosophy and natural laws

4. The Church

Out of the Roman exploitation and oppression of those who were conquered Christianity arose. In the midst of the Roman dominion the ideals expressed by the prophet brought hope and dignity to the oppressed, who for understandable reasons had even less interest in science and learning than their oppressors.

The early Church organizers, fighting to save man from the corruption and excesses of Rome, directed attention away from the physical world towards God and the afterlife.

With the disintegration of order that marked the demise of Rome, the Church understandably became concerned with preservation of existing knowledge rather than new discoveries. As a growing institution the Church required schools for the training of priests where the emphasis was on the Scriptures and where liberal and scientific studies were frowned upon.

4.1. brought hope and dignity to common people
4.2. had even less interest in science and letters than Roman oppressors
4.3. fought to save man from corrupt civilization
4.4. directed attention away from physical towards God and afterlife
4.5. was concerned with preservation of knowledge rather than discovery
4.6. required schools for training of priests
4.7. liberal and scientific studies were frowned upon

5. St. Augustine (354 - 430 A.D.)

One of the creators of the early Christian doctrine was St. Augustine, (A.D 354-430), Christian theologian and philosopher. Augustine's Confessions is an intimate psychological self-portrait of a spirit in search of ultimate purpose. Augustine believed he had found this through his conversion to Christianity in 386. According to the doctrine of his Enchiridion (421), he emphasized the corruption of human will, and the freedom of the divine gift of grace. The City of God (426), perhaps his most enduring work, was a model of Christian apologetic literature. Of the Four Fathers of the Latin Church, which also included Ambrose, Jerome and Gregory, Augustine is considered by many to be the greatest.

Augustine's doctrine combined elements of Pythagorean mysticism and Platonism with the emerging Christian doctrine to forge a paradigm which persevered for seven hundred years. This paradigm discouraged the acquisition of external knowledge, encouraging one to "know thyself" as Socrates had proclaimed. According to Augustine, the only kind of knowledge which was relevant was that given by God in the scriptures, and the internal knowledge attained by philosophical musings. Augustine tells us, "Go not out of doors. Return into thyself for in the inner man dwells truth."

5.1. combined Platonic and Pythagorean mysticism with Christianity
5.2. Discouraged seeking external reality

5.2.1. "Go not out of doors. Return into thyself. In the inner man dwells truth".

5.3. two kinds of knowledge

5.3.1. God-given (scriptures) and internal (philosophy)

6. Monasteries

The need to educate and train Monks in the scriptures and sacred rites of the Church led to the growth of the monastery as a refuge for the preservation and schooling of the ancient traditions. Here reading and writing were kept alive in Europe as monks copied, preserved, cataloged and analyzed the old manuscripts. Old volumes were transcribed as the paper decayed and the ink faded on the old documents. Embellishments and flourishes abounded as elaborate artwork was added to the new copies. There can be no doubt that embellishments were added to the text as well, although in principle they were copied verbatim.

For an excellent fictional treatment of the life in a monastery, read the mystery novel by Umberto Eco, called The Name of the Rose which is also a movie available on video

6.1. kept reading and writing alive in Europe
6.2. copied, preserved and analyzed manuscripts
6.3. could not (or would not) combat tide of superstition
6.4. The Name of the Rose by Umberto Eco

7. Dark Ages

The Dark Ages were dark not for the absence of light, but for the absence of enlightenment. Following the decline of Rome, order decayed rapidly in the satellite territories. Anarchy reigned. Ancient ethnic conflicts, and continued raids by marauding armies from the east kept the chaos from settling. As a result learning virtually disappeared in Europe until the twelfth century or so. Meanwhile the center of Western civilization shifted to the Middle East with the rise of Islam and Christianity as contrasting religious and political forces.

During the dark ages in Europe, civilization thrived in the mid East where some of the works of Aristotle were preserved and used as background for more research.

The Crusades were holy wars launched in attempts to invade the holy land and take control of it. In a series of assaults over a period of several hundred years the two religious groups battled.

7.1. learning virtually disappeared in Europe
7.2. until twelfth century
7.3. center of Western civilization shifted to Middle East
7.4. Byzantine and Arabic worlds maintained records and documents
7.5. Crusade kept contact open

8. Arabic Influences

The Moslem world maintained records and documents with a different perspective than was common in Europe. Here the works of Aristotle and Ptolemy were translated into Arabic and widely read. In addition to this role of preserving and cataloging documents, important progress was made in other areas. Advances were made in mathematics such as the Arabic numbers (still in use today), incorporation of the concept of zero (as opposed to nothing), and the rules and operations of algebra (x and y representing generic numbers). Astronomical advances included identifying and naming new stars, collecting data on planetary movements, star catalogs and tables of planetary movements. All the while, the knowledge of Alchemy was growing. This will play a role in our discussion of the development of chemistry in later lessons.

8.1. Preservation of records and documents

8.1.1. Almagest
8.1.2. Aristotle's writings

8.2. algebra

8.2.1. (numbers, zero, algebraic operations, new stars & catalogs)

8.3. astronomy

8.3.1. new stars, catalogs, better data

9. Rediscovery & Conflict

The wars and battles of the Crusade, bloody as they were, allowed for much contact between the Christian and Muslim worlds. As a result contacts were established along a front extending inland from the northern Mediterranean from Italy through Spain. Gradually the old documents made their way westward and into Europe for the first time. Slowly Church scholars in Europe became aware of a body of ancient knowledge which, pagan though it was, was vastly superior to their own. Many of the documents were in ancient Greek and needed to be translated into Latin, the official language of the Church. Ptolemy's works were fairly common in Europe by 1100, and Aristotle's by 1300.

9.1. wars brought much contact between the two civilizations
9.2. contacts established along front (Italy/Spain)
9.3. many old documents discovered
9.4. European scholars became aware of a body of knowledge of pagan origin yet vastly superior to their own
9.5. translated into Latin from Greek
9.6. Ptolemy by 1100, Aristotle by 1300

10. Critical Scholarship

Critical scholarship, that is seeking new knwledge really began with the necessity fo translate the ancient Greek texts into Latin.

Beginning in the latter part of the eleventh century a new attitude towards learning emerged in Europe as Church scholars carefully examined the ancient writings. Much work was required to remove inconsistencies which had appeared over the centuries of translations and transcriptions. Different versions of a given work used different wording and sometimes contradicted one another. Eventually Aristotelian cosmology was integrated with Ptolemaic astronomy and Christian theology.

This fusion of philosophies had both direct and indirect effects on the development of science. For one thing it was a reformation which prepared the way for radical ideas and changes. At the same time it created stable communities of scholars centered around a university with the goal of acquiring new knowledge.

10.1. appeared in 11th century
10.2. a new attitude towards learning emerged
10.3. church scholars examined Aristotle's writings carefully
10.4. to remove inconsistencies in inherited patterns of philosophy
10.5. eventually integrated Aristotelian Science with Christian Theology
10.6. prepared the way for radical ideas
10.7. created Universities and stable communities

11. St. Thomas Aquinas (1225-1274)

The new views of learning and the new cosmology were expressed in an incredible work published by St. Thomas Aquinas (1225-1274).

In Summa Theologica (1267) science became a field of study as part of the Thomistic Natural Theology, also called Scholastic Philosophy. Later we will study the views on motion which were part of the physics of the scholastics. Summa Theologica incorporated Aristotle's cosmology and Ptolemy's astronomy into Christian doctrine while establishing a standard method for acquiring new information. It established Aristotle as the authority in all philosophical and scientific matters. It also provided a detailed account of the structure of heaven and hell, and created many of our common Western images of of heaven, hell, angels, and a flat earth supported upon pillars at its four corners. The architecture was described in The Divine Comedy by Dante Alighieri (1265-1321), Italian poet and nobleman, written in exile after his downfall as the ruler of Florence.

11.1. Scholastic Philosophy expressed in Summa Theologica (1267)
11.2. Science became a field of study in Thomistic "Natural Theology"
11.3. Aristotle and Ptolemy's views incorporated into doctrine
11.4. established Aristotle as authority in the philosophical and scientific matters
11.5. most of current concepts such as good/evil, Heaven/Earth/Hell
11.6. expressed as Dante's Inferno in "The Divine Comedy"

12. Scholastic Cosmology

In this cosmology, the architecture of the universe is an expression of the Divine plan for salvation. Earth is composed of gross, corruptible matter which is subject to perpetual change (Aristotle). These changes seek the lowest level due to the low nature and evil tendencies of man which led to expulsion from the Garden of Eden and have been a problem ever since. The heavens, on the other hand are changeless, incorruptible, made of quintessence, and subject to a different set of rules (Aristotle).

There is a sharp distinction between the sublunar and celestial spheres, and everything has its Aristotelian place. Man's lower nature is dragged towards Hell at the center of the earth while our higher nature seeks a union with God in a heaven beyond the stars, while in between earth and heaven is the angel's realm. The angels, which have become cherubic and friendly after hundreds of years of being dark, fearsome and aggressive, are in charge of the motion of the heavens and for transferring messages from heaven.

It is clear that this model reflects the three tiered Pythagorean model containing Aristotle's imperfect sublunar with the addition of Hell at the center. Cosmos and Olympos are easily associated with Heaven and the heavens.

It also conviently places Hell much closer and more easily attainable than heaven which was separated from earth by the crystal spheres which contained the planets moving in Ptolemy's epicycles. This also fit in nicely with the Christian theology.

12.1. Spherical, Earth-centered universe
12.2. architecture of universe is expression of divine plan for salvation
12.3. Earth has gross, corruptible matter subject to perpetual change,
12.4. seeks lowest level
12.5. heavens are changeless, incorruptible, made of different substance, subject to different rules
12.6. Sharp distinction between sublunar and celestial spheres
12.7. everything has its Aristotelian place
12.8. man's lower nature dragged to Hell at center of Earth
12.9. higher nature seeks union with God in heaven beyond the stars
12.10. between Earth and Heaven is angel's realm (in charge of motion)

13. Renaissance

The renaissance was the beginning of the age of enlightenment. The reawakening of learning was due to many factors sparked by the rediscovery of the ancient writings. Indignation with corruption in the Church was preparation the Reformation which was a rebellion within the Church which would ultimately lead to the establishment of the Protestant faiths. Additionally Europe was recovering from a cultural breakdown during the Bubonic Plague epidemic of the early fourteenth century. There was also renewed interest in paganism, art, nature, music, and languages from the ancient world, and already a resistance to the rigidity of scholastic philosophy. There was rapid economic advance and political change as civilization began to rebuild. And of course, there were many new manuscripts.

13.1. recovery from great cultural breakdown during Plague of early 1300s
13.2. indignation with corruption in Church
13.3. preparation for Reformation
13.4. fresh interest in paganism, art, nature, music
13.5. new study of languages
13.6. resistance to rigid scholastic philosophy
13.7. economic advance and political change
13.8. many new manuscripts

14. Cosmological and Philosophical Problems

As new manuscripts of the old documents showed up there were more and more discrepancies. Various versions of the documents and writings showed significant differences in content. This is not suprising considering that by that time these documents were nearly two thousand years old . They had been copied and recopied, and in many cases had been translated back and forth between Greek, Latin, and Aragic. There was little clue as to which documents had been translated and which had not. Manuscripts in the original Greek showed significant differences from those in Arabic and it was impossible to determine what had been added or deleted from the original texts.

14.1. Aristotle vs. Ptolemy

Besides that when the writings of Aristotle and Ptolemy were compared, scholars found significant differences in their ideas. Remember that more than six hundred years and a cultural boundary separated the two. Many changes had taken place between the Athens of Aristotle's time in 500 B.C. and the Alexandria of Ptolemy in 140 A. D. Six hunderd years is a long time in any culture and it was one of the failings of Renaissance scholars to recognize those changes.

14.1.1. Aristotle's homocentric spheres and Ptolemy's devices were at odds

.Aristotle's homocentric spheres and Ptolemy's devices were at odds. Although Ptolemy offerered a superior astronomy, he profferred no cosmology. In abandoning Aristotle's qualitative simplicity for quantitative precision, Ptolemy offered a more complex system which was extremely inconsistent and difficult to use, but which had given reasonably accurate predictions of the motion of the planets. Besides that, it was becoming increasingly clear that Aristotle's views on motion had many flaws. Aristotle offered a whole cosmology which was qualitatively satisfying Ptolemy abandoned Aristotle's simplicity and unity with a system which was quantitatively accurate

14.1.2. Aristotle's views on motion had many flaws

For one thing, by 1400 it was clear to most scholars who cared that Aristotle was not an authority on motion. But the study of motion was not of great interest to most scholars, just as the study of subatomic particles is not of interest to most of us today.

Additionally, Aristotle had taught that mathematics was of no use in describing change and yet Ptolemy's methods used complicated mathematics, uknown in Aristotle's time, to do just that.

Ptolemy's methods did not actually use mathematics to describ change so much as it predicted the results of the changes in positions of the planets. Even this was not considered to possible in Aristotle's reasoning. by 1400 it was clear that Aristotle was not an authority on motion study of motion was not of interest to most scholars Aristotle believed that mathematics was of little use in describing change

14.1.3. Ptolemaic Theory no longer matched observations

On top of all of theat, calculations using the Ptolemaic method no longer matched observations. The planets were not where they were supposed to be.

The long time period since the original observations had magnified errors, and the modifications which had been made to Ptolemy's methods was unknown, having been obscured by nearly one thousand years of translations, transcriptions, and additions.

Because Ptolemy's methods were based on observations, they were inherently prone to drift. By that we mean that they would be like a watch which ran slow or fast. This is not a problem with watches because you can always compare it to another watch. But what if there is only one watch?

To add to the confusion, the planets to not move like clockwork, not like the moon, sun, and stars. Their apparent motion through the background stars is irregular. They speed up and slow down, they change direction, and there is that annoyingly irregular retrograde motion.

With the irregularities of planetary motion, a little error means a lot of discrepency. long time period magnified errors Arabic modifications unknown errors and embellishments not known planets are irregular

14.2. Jean Buridan

One important critic of Aristotle's work was Jean Buridan, a professor at the University of Paris . He taught that there was no motion in nature that was properly described by Aristotle. Buridan himself openly criticized Aristotle and questioned his ideas of projectile motion.

Buridan's students would become among the most influential men in Europe as the University of Paris became the institution of choice among the wealthy and powerful of Europe. Many of his students went on to become Church officials, others became noted scholars and university leaders.

These critiques did not present a serious challenge to the authority of Aristotle. In fact he Church paid very little attention to the whole thing. The study of motion itself was not of interest to most scholars. The positions of the planets were important for religious purposes, but there was no relationship of any interest among them. Ptolemy's methods did not assume that the moti0n of one planet was in any way related to any other.

To the the scholastics who considered, along with Aristotle, that mathematics was of little use in describing change, the study of motion, heavenly or otherwise, was not a potentially fruitful pursuit for shcolarly studies.

14.3. Roger Bacon

Another important contributor to the development of science was Roger Bacon (c. 1214-94), English scholastic philosopher, Franciscan monk, and scientist. He was known as the Admirable Doctor. He studied languages, mathematics, alchemy, and astronomy at Oxford and later taught there. As a professor, he pugnaciously into many puqrrels with other learned men and was in constant trouble for his radical ideas.

In the Opus majus (Major Work), written for Pope Clement IV, he argued that science was complimentary to faith and not opposed to it. He urged that extensive studies of these areas be included in university curriculums. Clement died before acting on this proposal but the idea remained alive and was eventually incorporated, influencing the course of higher education forever. Our modern universities reflect Bacon's ideas in our curricula.

Because we wrote about alchemy he became somewhat legendary on those topics such that many works on alchemy and magic have been attributed to him. Among other things, he is often falsely given credit for the invention of gunpowder, and there have been some rumors that he had a telescope or a microscope, although it is highly unlikely that he had either.

In modern time Bacon is best remembered for his interest in natural science, experiments and observations. For scholarship he favored inductive method using experiments and observations to ascertain the laws of nature from watching the behavior of matter.

15. Food For Thought: What Makes A Good Theory Good?

In order for a theory to be a good one it must do more than just explain the facts. There may be many ways to explain the facts, a truth well known to courtroom dramatists. Although part of the scientific method, an explanation is not enough by itself. Over the years as our knowledge of the world has advanced we can look back and see what other qualities a good theory has.

First and foremost, a theory must be feasible, that is it must be consistent with a current paradigm. It also must provide a convenient and easily visualized model, whether or not that model can be built mechanically. A good theory must organize the known information in such a way to show relationships between different parts of the model. It must also provide a basis for the prediction of outcomes based upon specific inputs.

There are two other aspects of a good theory which are often overlooked. A good theory will also point out previously unsuspected facts and suggest new relationships and new outcomes which can be tested or observed.

15.1. is consistent with paradigms
15.2. provides a convenient, easily visualized model
15.3. organizes known information
15.4. provides a basis for prediction of outcomes
15.5. points out unsuspected facts
15.6. suggests new relationships

16. Copernican Astronomy

16.1. Copernicus (1473 - 1543)

Copernicus (1473-1543) was a Polish cleric and astronomer. Born Mikotaj Kopernik, he preferred the Latin name Nicholas Copernicus in respect for the official Church language.

Copernicus was a minor Church bureaucrat and renaissance man who was infused with Pythagorean mysticism and Scholastic philosophy. He was well educated in Poland and Italy, and was a student when Columbus sailed into the Western Hemisphere. He studied theology, law, medicine, math, economics, classics and took a prolonged study of astronomy. He made very few observations himself, but he returned to Poland with an ambitious project in mind.

He intended to redo the Ptolemaic system , bring the calendar back in synch with the stars, and figure out a better way to predict planetary motions. A skilled mathematician, and with the help of mathematics sophistication much better than that of Ptolemy's time, Copernicus went to work with Ptolemy's methods and the latest detailed observations, most of which dated from the Arab era more than five hundred years earlier. After laborious calculations he found it easier and more efficient to place the sun as a common center of motion for all of the planets, including Earth.

His treatise De Revolutionibus Orbium Caelestium (1543) expounded the Copernican system and laid the foundations of modern astronomy. He is often associated with the term Copernican Revolution for his role in the transformation from the geocentric to the heliocentric world-view. The story is not quite as simple as that.

Copernicus was not a revolutionary in the strict sense of the word. He did not intend to overthrow the geocentric system and replace it with the heliocentric. It's not like discarding an old pair of socks and buying new ones. As far as the revolution is concerned, the main contribution of Copernicus was the seeds that he planted and the thought his works stimulated.

16.1.1. minor church bureaucrat and renaissance man
16.1.2. infused with Pythagorean mysticism, Platonic Geometry and Scholastic philosophy
16.1.3. well educated in Poland, Italy
16.1.4. a student when the New World was discovered
16.1.5. theology, law, medicine, math, economics, classics
16.1.6. prolonged study of astronomy
16.1.7. returned to Poland with ambitious project in mind
16.1.8. made only a few observations himself

16.2. Ptolemaic System seemed "top heavy"

To Copernicus, the Ptolemaic System seeded "top heavy." He was concerned with Plato's Question on how to fit the motions of the planets into the fewest possible circular motions. An advocate of parsimony, after Ockham's Razor, Copernicus was looking for the simplest solution to the problem.

In Copernicus' time there was considerable discrepancy between observation and prediction of planetary positions. The calendar was out of date and the exact length of the year was in doubt. The Church, which was highly dependent on rituals, such as Passover, lent, Easter, etc. needed an accurate and reliable calendar to schedule events. It was hard to designate Easter as the first Sunday after the first full moon after the vernal equinox when there was uncertainty about when the vernal equinox actually occurred and besides you couldn't see the moon sometimes because it was too cloudy.

Copernicus also did not like Ptolemy's inconsistent use of the devices, and did not like the use of the equant at all, thinking it to be too much of a deviation from the circular paradigm. Trying to improve the accuracy, he laboriously calculated and rechecked Ptolemy's calculations and found many errors. This is not surprising considering that in Ptolemy's time the concept of the zero, the rules of arithmetic, and the use of numbers had not yet been invented. Imaging trying to perform detailed and arduous calculations using Roman Numeral, let alone the Greek system which used various combinations of letters of the alphabet to designate numbers.

16.2.1. concerned with Plato's Question
16.2.2. fewest possible uniform circular motions
16.2.3. Ockham's Razor (parsimony)
16.2.4. considerable discrepancies between observation and prediction of planetary positions
16.2.5. exact length of year was in doubt
16.2.6. calendar was out of date
16.2.7. didn't like inconsistent use of devices, especially the equant
16.2.8. laboriously calculated and rechecked Ptolemy's calculations

16.3. De Revolutionibus Orbium Celestium (1543)

The major work of Copernicus, he waited until his death bed to publish it, presumably to avoid controversy. He, or his publishers, took special care to avoid igniting the wrath of the Church which one might expect from contradicting the paradigm. For one thing the book was dedicated to Pope Paul III. For another the preface to the book contained a disclaimer which stated that the work was not being offered as a cosmology, but rather as a more parsimonious method for calculating planetary locations. It is clear upon reading that he was justifying it and showing its feasibility while denying the physical reality of it. Although the system was sun centered, and suggested that the earth moved, it was still circular, and still used epicycles and eccentrics. Besides it was a little more accurate and easier to use and allowed the development of a calendar which was tuned to the heavens once again.

Above all, what the work accomplished was to show that celestial motion could be represented by a combination of uniform circular motions in a sun centered system.

16.3.1. dedicated to Pope Paul III
16.3.2. waited to publish to avoid controversy
16.3.3. saw the first copy on his deathbed
16.3.4. careful to point out it was a utility for calculation
16.3.5. denied physical reality while justifying it
16.3.6. proved that celestial motions could be represented by a
16.3.7. combination of uniform circular motions in a sun-centered system
16.3.8. still used epicycles and eccentrics

16.4. Uniform Circular Motion

Uniform circular motion was, after all, in the Platonic tradition. Copernicus himself stated that any type of celestial motion other than circular was "obviously impossible". In fact, he said that "the intellect recoils with horror" at any other suggestion and that "it would be unworthy to suppose such a thing in a Creation constituted in the the best possible way." Considering that most of the objections to a moving earth were traceable to Aristotle's views on motion which were commonly held, largely due to Buridan, to be less than absolutely correct.

16.4.1. the Pythagorean/Platonic tradition
16.4.2. any type of celestial motion other than circular was "obviously impossible"
16.4.3. "the intellect recoils with horror" at any other suggestion
16.4.4. "it would be unworthy to suppose such a thing in a Creation constituted in the the best possible way"

16.5. Copernican Astronomy

In the Copernican solar system, earth is a planet which, like the others is in a circular orbit around the sun. The moon circles the earth. The motion of all of the planets, including earth is truly circular and at a uniform speed, but the actual center of the main circles had to fall a little to one side of the unmoving sun. The sun was not really at the center, but offset a little from it.

Compared to Ptolemy's system, which required 80 spheres and had some of the epicycles rotating backwards, the Copernican system used only 46 epicycles and eccentrics, all of which turned in the same directions. Planets nearer the sun moved faster than those further out, but each planet moved at a constant speed on each of its spheres.

Copernicus did mention that retrograde is an optical illusion caused by the combined motions of the earth and another planet. He even presented a picture which showed how the optical illusion came about. Isn't it strange that he would do this considering the contention that the model represented nothing more than a parsimonious tool for calculating planetary positions?

16.5.1. Earth is planet like others in circular orbit around sun
16.5.2. moon circles Earth
16.5.3. truly circular and uniform motion of all planets, including Earth, with respect to their own centers
16.5.4. common center of the main spheres had to fall a little to one side of the unmoving sun
16.5.5. only 46 spheres (vs. 80 for Ptolemy)
16.5.6. all epicycles and eccentrics had the same direction of motion
16.5.7. planets nearer to sun have faster uniform motion

16.6. Retrograde motion is optical illusion

16.6.1. larger motion ==> nearer
16.6.2. caused by joint motion of Earth and planet

Here's an animation of two planets showing that the apparent retrograde motion of the outer planet is an illusion caused by the faster moving inner planet overtaking and passing the slower outer planet.

(This animated gif was obtained from Astronomy 161 web site at The University of Tennesee, Knoxville.)

16.7. Jupiter/Saturn conjunction

Although the Copernican system was easier to use, it wasn't much easier. The mathematics was still beyond the average scholar, let alone the average citizen. Not only was it not much easier, it also was not much better. A conjunction (alignment) of Jupiter and Saturn occurred one month earlier than predicted by Ptolemaic calculations, but only several day earlier than Copernicus predicted. It is true that the calculations were done based on old data, the accuracy of which was questionable. At the time they had no way of knowing whether the errors were the result of bad data, bad calculation, coincidence, or all three. The fact that the Copernican method was slightly easier and slightly more accurate gave it the edge despite the cosmological problems that lay not so cleverly concealed in it.

16.7.1. heliocentric method gave only slightly better results
16.7.2. occurred one month earlier than Ptolemaic calculations
16.7.3. occurred several days earlier than heliocentric calculations
16.7.4. based on old, possibly inaccurate data

16.8. Reception Of Copernican Theory

Despite the seemingly justified concerns of Copernicus and his publishers, the publication of Revolutionibus caused no particular stir. It was used by the Church to determine the Gregorian calendar which still in use today with a few modifications. This brought the calendar back into synchronization with the stars. The Copernican system was not taken as a serious physical model anyway and the addition by Copernicus of moving devices obscured its simplicity. Along with the disclaimer in the preface the obtuse writing style and the difficult mathematics obscured the physical reality.

Another factor which contributed was that the Copernican system simply could not be true because it contradicted the widely held views of Aristotle on motion. These had become incorporated into the paradigm and were simply seen as axiomatic, requiring no proof. There was nothing in the Copernican model which pointed to significant contradictions with the geocentric paradigm.

Aristotle's concepts of motion, which we will study in greater detail in a later lesson, required certain effects which ought to have been detectable if the earth were indeed spinning on its axis and orbiting the sun. The inability to observe these phenomena was taken as a priori proof that the earth could not be moving, thereby confirming the nature of the Copernican theory as a convenient tool rather than a physical theory.

Aristotle had claimed, for example, that if the earth was moving fast enough to complete a revolution per day then the air would be rushing by, similar to the way the wind blows through the open window of a car. Obviously birds would be unable to fly because they would be left behind like a leaf in a rapidly flowing stream.

Additionally, according to Aristotle, if the earth was spinning, a person who jumped would not land in the same place because the earth would move out from under them. And besides, there is no reason or cause for the earth to move and nothing to sustain its motion.

It is important to note here that regardless of how much sense these ideas make to us, they were the paradigm and Aristotle was the authority on natural philosophy and so one doesn't need to question Aristotle.

There were other factors, some of which had already been used against Aristarchus in 250 B.C.. No parallax of stars had been observed, Venus doesn't show phases, and earth is sublunar so it can't be a planet.

The idea of a sun centered universe was seen by many as a return to the pagan sun worship which the Church had worked hard to overcome.

16.8.1. Caused no particular stir
16.8.2. used to determine Gregorian calendar (1582)
16.8.3. brought calendar back into synch with stars
16.8.4. Was not taken as a serious physical model
16.8.5. addition of moving devices obscured simplicity
16.8.6. writing style obscured the physical reality
16.8.7. Contradicted Aristotle's concept of motion breezes, sense of motion, no cause, nothing to sustain it Aristotle is correct without question

16.8.8. no parallax of stars observed
16.8.9. no phases of Venus observed
16.8.10. calculated sizes of stars was too big
16.8.11. Earth is sublunar so cannot be planet
16.8.12. Sun centered ==> return to pagan sun worship

17. Bruno (1547 - 1600)

Although not revolutionary in the strict sense, Copernican ideas did provoke some thought. It was the speculations that followed which caused most of the trouble with the Church.

One such was Bruno (1547 - 1600). Bruno was a Renaissance man who began to speculate on the architecture of a Copernican universe. If the stars don't rotate, he wrote, then they need not be all the same distance away on the celestial curtain. The stars could be spread throughout space and be very far away. Stars might be like our sun, only far enough away to be pinpoints of light. They might be self luminous like the sun and not merely pinpricks in the fabric separating heaven from the cosmos. They might have planets like earth and life.

And if earth is not the center then maybe the sun is not either. In fact, Bruno speculated the universe might even be infinite is size and infinite in time.

These ideas are very similar to our modern views of the universe, having been substantiated by more than three centuries of observation and science. But like so many others before and after, Bruno was too far ahead of his time.

Bruno was burned at the stake in 1600, nine years before Galileo turned his telescope to the heavens, and one year before Brahe hired Kepler.

17.1. stars don't rotate ==> could be spread through space
17.2. stars are like sun: self luminous, with planets and life
17.3. Earth is not center, then neither is the sun necessarily
17.4. universe is infinite is size ==> could be infinite in time

18. Summary

In this program we traced the river of our cultural heritage in physical science from the Roman Empire, to Copernicus, his heliocentric theory, and the reaction to it.

Along the way we watched the growth of the Church as the authority on everything, including physical science; we saw the influence and importance of contributions from the Arabic world; we examined the conflict that arose when the works of Aristotle and Ptolemy were compared one thousand years after they were written.

We watched the reemergence of learning exemplified by the Scholastic Philosophy and later by the Renaissance.

We studied the contributions of several important indivuals. St. Ausustine, St. Thomas Aquinas, Jean Buridan, and Roger Bacon.

Out of that productive era of art, literature, and music,came Copernicus who planted the seeds of a thought revolution whether he intended to or not.

Intending to rework the Ptolemaic system, Copernicus found it easier to put the sun at the center of things for purposes of calculation. His book The Revolutions of Heavenly Objects, published on his deathbed in 1543, described the heliocentric system and the methods of calculation of the planetary positions. These were slightly more accurate that those of Ptolemy. Although heliocentric, the Copernican system still used circles and devices, much like Ptolemy's method. Because it was circular and because it contained the disclaimer that it was intended to be arithmetic and not cosmology, the Church accepted the method, dedicated as it was to the Pope, and used it to reset the calendar, which was ten days out of date. .In doing so he stimulated curiositry and aroused speculation from the likes of Bruno, who was executed at the stake for heresy nearly sixty years later.