There are five men who are principally responsible for wresting our view of the Cosmos from the province of myth and/or religion. They are Nicolaus Copernicus, Tycho Brahe, Galileo Galilei, Johann Kepler, and Sir Isaac Newton. Individual writers tend to focus on one or another of these men, such as Carl Sagan focusing primarily on Kepler and not even mentioning Galileo. But there is no doubt that the great idea which began with the view of Copernicus that the Sun was the true center of the solar system and ended with Newton's formulation of the laws of gravity could not have been achieved without the great contributions of each man. Let us take a moment to assess them.
a. Nicolaus Copernicus (1473-1543)
The six volume set
which comprised his life's work was finally published at about the same
time he died. While he formulated the basic ideas in it no later than
1514, the work was considered so controversial, because of its Sun
centered universe as opposed to the accepted Earth centered universe,
that he still hesitated to publish it in spite of an "official"
invitation to do so from the pope, issued in 1536.
The work was intended as a mathematical reinterpretation of Ptolemy.74 His stated motivation was to increase the accuracy of calendars, a goal which was seen as an acceptable one. In his books, he correctly describes such phenomena as the precession of the equinoxes being caused by the gyration of the axis of rotation of the Earth. But sadly, he clung to the erroneous idea that the orbits of the planets around the Sun had to be circular, and this caused him to devise complicated distortions, of roughly the same complexity as those of Ptolemy which he sought to supplant, to account for the observed phenomena, such as the retrograde motion of the planets.75
The views of Copernicus, that the Sun was the center of the solar system, had some other implications for our overall world view. If the Earth was not the fixed center of the universe, then the universe had to be much larger to account for the observed fixed positions of the stars. Also, the view that things "naturally" fell towards the center of the Earth (which was the center of the universe) could no longer be unquestioningly accepted, and this led eventually to Newton's laws of gravitation.
b. Galileo Galilei (1564-1642)
Galileo was born
two decades after the death of Copernicus, and by the time he began his
studies, his mind was ready to wholeheartedly accept the Sun centered
view of the universe which Copernicus had proposed. However, a 1597
letter to Kepler discloses that he feared to advocate the theory of
Galileo did not actually invent the telescope, but as a trained astronomer, he was the first to put this invention to the obvious use of studying the stars in a methodical way. What Galileo actually invented was a method for checking the curvature of the lenses, and this manufacturing technique resulted in a great demand for telescopes of his. From late in 1609, Galileo announced a series of discoveries about the Sun, the Moon, and the stars which would eventually revolutionize our understanding of the universe.
The controversy begun by these observations of Galileo, taken in combination with the book of Copernicus, led to a decree issued on March 5, 1616 which declared the book of Copernicus to be "false and erroneous" as a matter of religious faith.76 Accordingly, Galileo was careful to obtain prior approval of his 1632 book which discussed at length the two contrasting world views of Copernicus and the ancients. But thorough readers of the book noted that the conclusion he reached, that the classical system was "correct," seemed so artificial and contrived that the book would actually enhance the position of Copernicus and thereby undermine the authority of the pope and his decree. Thus, in spite of his prior license to publish, Galileo was prosecuted by the Inquisition in 1633 (many believe the principal evidence against Galileo was a forgery), forced to recant, and sentenced to house arrest for the remainder of his life. In spite of this, Galileo continued to work and correspond with other scientists right up until his death in 1642.
c. Tycho Brahe (1546-1601)
Tycho Brahe, born
three years after the death of Copernicus, was also easily able to
accept the radical ideas of the Polish astronomer. In 1576, Brahe
established a great observatory under the patronage of King Frederick
II of Denmark. Surrounded by scholars, and visited by learned travelers
from all over Europe, Brahe and his assistants collected a series of
astronomical observations which corrected nearly every known prior
record of the paths of various bodies through the heavens.
The death of Frederick in 1588, and the subsequent disputes with his heir over the funds to be allocated to his use, led eventually to his departure in 1597, and his later appointment to the court of the Holy Roman Emperor, Rudolf II, in Prague during 1599. In 1600, he was joined by Johann Kepler, who carried on his work after Brahe died the next year.
Brahe was in no way a theoretician. His great body of observations would find no practical use until Kepler would be forced by them to once again alter our view of how things worked. His contributions can be measured as three-fold: 1) the concept that man could carefully construct scientific instruments to observe natural phenomena; 2) the concept that a group of scholars could work cooperatively to produce a large body of scientific knowledge simply for the sake of having it; and 3) the concept that knowledge had a quality which was related to the precision of the scientific observations and the care with which those observations were recorded for posterity, a quality which Brahe tried to demonstrate as well by having the finest craftsmen used to print and bind the books in which his accumulated knowledge was distributed.
d. Johann Kepler (1571-1630)
Kepler started his
education with the idea of becoming a Lutheran minister, but this idea
was sidetracked by those who quickly recognized the greatness of his
mind. He tried to teach, but the principal result of his teaching was a
vision, totally erroneous, of a relationship between the six known
planets and the six so-called "perfect" solids.77
This vision was to haunt Kepler all of his life, because he could never
make it work out. But it motivated Kepler to pursue a career as an
astronomer and astrologer.
In 1600, Kepler joined the staff of Tycho Brahe in Prague, and when Brahe died the next year, Kepler was promptly appointed to replace him. In 1602, Kepler published his first book at Prague, which supported the prevailing view that the stars guide the lives of men. As a highly skilled mathematician, his horoscopes were in great demand. We tend to overlook this aspect of his life, but it is the principal factor which allowed him to survive in the harsh world of seventeenth century Europe.
Using decades of observations accumulated by Brahe and his assistants, Kepler derived the first two of his three laws of planetary motion, which he published in 1609. But before he could correctly interpret the observed results, he first had to amend our understanding of optics. His 1604 book provided the foundation for all of the advances in our understanding of the workings of the human eye, including the actual reason that eyeglasses work (even though they had been made for roughly three centuries before).
Kepler took the concept of a Sun centered solar system from Copernicus, but was forced by the accumulated effect of the observations of Brahe and his associates to discard the circular orbits which Copernicus refused to abandon. Instead, Kepler was led to an accurate description of planetary orbits as an ellipse, with the Sun at one focus of the ellipse. But an elliptical orbit was incompatible with a theory of uniform motion, which required the planets to always move at the same velocity. So, the second law of Kepler held that, instead of traversing an equal arc in an equal amount of time (uniform velocity), the planets would cover an arc which would describe an equal area as related to the focus at which lay the Sun. This requires the planets to slightly speed up and slow down as they traverse their orbits. Ten years later, in 1619, he published his third law of planetary motion, holding that the cube of the planet's average distance from the Sun was at a constant ratio to the square of the time required for the planet to complete its orbit.
Each of the above laws was derived by using the fundamentals of scientific method: carefully recorded observations; carefully calculated mathematical formulas; and a willingness to accept an answer which these two forces demanded.
However, Kepler was tragically affected by the upheavals occurring during his life. In 1620, he was forced to rush to the defense of his mother, who had been accused of witchcraft. Because of the Thirty Years' War, and various consequences thereof, he was unable to publish his final collection of his thoughts about his life's work until 1627. On his way to collect interest due to him so he could continue working, he fell ill and died on November 15, 1630. If the location of his grave was in any way recorded, the Thirty Years' War obliterated that record.
While Kepler was quick to acknowledge his debt to Galileo, who actually survived Kepler, it appears that Galileo did not return the favor and acknowledge the contributions of Kepler. Like Copernicus, Galileo was stuck on the idea of perfect circular orbits, and that myopic view even prevented Galileo from producing an even greater contribution with his final work in the field of inertia. Thus it was left to another to tie it all together.
e. Sir Isaac Newton (1643-1727)78
Sir Isaac Newton
is arguably one of the greatest geniuses which mankind has ever
produced. He invented whole new fields of mathematics because he needed
tools which would allow him to solve the great scientific questions of
his time. It was left to Newton to finally draw together the
fundamental principals of our modern view of the Cosmos.
Newton was born just months after the death of Galileo, but had a very troubled childhood which contributed an erratic nature to his interactions with other people. It is believed he was a virgin at the time of his death, having never developed a love for any person which would draw him away from his scientific studies.
When Newton arrived at Cambridge in 1661 to attend Trinity College, the schools were still mired in teaching the Earth centered universe of Aristotle and Ptolemy, even though it had been about 118 years since Copernicus had published his great work. But the rebellious students of that time, including Newton, found plenty of time and motive to study the writings of the new breed of scientists. Newton wrote: "Plato is my friend, Aristotle is my friend, but my best friend is truth." This philosophy launched Newton on his path to scientific greatness.
Beginning from the natural philosophy and geometry of René Descartes, Newton formed the foundations of the mathematics of infinite series, which we now call Calculus, and in 1669 he wrote down his first thoughts on this subject. A revised version issued two years later established Newton as the leading mathematician of Europe, in spite of the fact that his work was known to only a few savants.
As if his contributions to mathematics were not enough, while forced to sit idly at home during the plague years of 1665-1667 he developed his inverse square law79 and an essay on Color. The essay was eventually expanded to a university course in optics, which he taught from 1670-1672. His work on refractive analysis led him to believe that lenses would always distort the colors passing through them, so he designed the first reflecting telescope based upon a large curved mirror. This telescope came to the attention of the Royal Society of London in 1671, and by 1672, Newton had been elected as a member and had presented his first paper on optics to that society. However, less than a year later, the irrational rage grew within Newton, who could not take any criticism of his work from anyone, and beginning in 1672, Newton withdrew into virtual isolation. By 1678, Newton had apparently suffered a complete nervous breakdown, and he would only most grudgingly return answers to correspondence directed to him.
Nonetheless, during this period of isolation, Newton continued to think about the subject of the orbital dynamics of planetary motion. After a 1684 visit from Edmund Halley, Newton wrote a short piece titled "On Motion." While working on a revision to that piece, Newton finally embraced the idea of inertia which had eluded Galileo, and this led to his first two laws of motion: 1) a body at rest remains at rest unless compelled to change by an outside force; and 2) when a force acts on a body, the change in the motion (meaning velocity times mass) of the body is proportional to the force impressed on the body. Eventually, the third law of motion was added: 3) to every action, there is an equal and opposite reaction. Analyzing these three laws in light of Kepler's third law and the known facts about the moons of Jupiter and our own moon eventually led Newton to the law of universal gravitation: every particle of matter in the universe attracts every other particle of matter in the universe with a force which is proportional to the product of their masses and inversely proportional to the square of the distances between their centers. This all grew into the culminating work of his life, Mathematical Principles of Natural Philosophy, first published in 1687.
After the publication of the first edition of his greatest work, Newton became involved with the Protestant resistance to the attempt of King James II to restore the Roman Catholic faith in England. This involved him with politics, and exposed him to the excitement of life in a big city, London. No longer content with the quiet of an academic cloister, in 1696 Newton obtained an appointment as warden and then master of the mint, a position which gave him a considerable income of up to £2,000 per year. With his move to London secure, his creative years were essentially at an end. But he began to receive recognition for his accomplishments, including a knighthood bestowed by Queen Anne in 1705. He continued to revise and publish new editions of his scientific works until his death. However, if there was any intellectual passion remaining in him, he devoted that to studies of religion. In fear of persecution as an unbeliever, he refused to allow any of his religious writings to be published until after his death. But it must be seen that this attempt to apply the rules of scientific inquiry to a study of the bible, its origins, and its chronology would have far reaching implications for Western Civilization, implications which we have not yet fully digested to this day.
74 Very little is known of the life of Ptolemy. Working backwards from modern mathematical models of the universe, it is possible to date his observations to the second century, a. d. A contemporary wrote that Ptolemy was actively working at the library in Alexandria during 127 a. d. through 145 a. d., with possible activity as late as 151 a. d. (see Encyclopaedia Britannica.) His thirteen volume work of astronomical observations and the mathematical description of his Earth centered universe was of such great value to three civilizations, Classical, Arabian, and Western, that it survives to this day. In fact, the Christian church was so enamored of the erroneous Earth centered universe that it used all its power to suppress opposing points of view, thereby contributing mightily to roughly fourteen centuries of no progress in the sciences.
75 The word "planet" comes from the Greek word meaning "wanderer." The planets were "stars" which appeared to "wander" through the heavens. An observer on the Earth will see a planet moving along gradually in the night sky, proceeding from one constellation to another. Retrograde motion occurs when the Earth, as it moves through its own orbit, overtakes the current position of another planet, causing the other planet to make an apparent "loop the loop" through the constellations. This looping action, now well understood, was quite disturbing to ancient thinkers.
76 The "false and erroneous" declaration was due to the challenge to Aristotle and Ptolemy and their Earth centered universe, not due to the errors which modern science can show.
77 The six solids are the sphere, the tetrahedron, the cube, the octahedron, the dodecahedron, and the icosahedron. The sphere has no sides, and each of the other has all of its edges as exactly the same length. Given that constraint, no other solids are possible.
78 Remember, a stated motivation for Kepler was to produce a more accurate calendar. In 1582, Pope Gregory XIII promulgated the calendar still in use today, but it was not adopted in England or its colonies until the eighteenth century. Nonetheless, I have given the "new style" date of birth here.
79 The inverse square law holds that any force acting radially on a planet decreases with the square of the distance of the planet from the Sun. This law was the first step in the development of his law of universal gravitation.
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