Johannes Kepler Essay

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Johannes Kepler was born in the midst of an exciting and confusing time for Europe. The continent was entering the Renaissance, a reawakening of thought across the continent. By the time of Keplers birth, the Renaissance had reinvigorated European culture, politics, philosophy, religion, literature, and science. The authority of the Catholic Church was challenged for the first time in centuries by the reformer Martin Luther, who pointed out the wrongs that he felt the Church had committed. Luthers rebellion spurred the Protestant Reformation, in which Luther and his followers freed themselves from the authority of the Church, creating a new sect of Christianity. Kepler, a Protestant, often found himself caught in the midst of the resulting tension between Catholicism and Protestantism. Catholics frequently persecuted him.

A similar challenge of scientific authority was also in progress, a radical shift in thought that later became known as the Scientific Revolution. Scientists in all fields were beginning to question the wisdom of the ancient philosophers who had molded their disciplines. They gradually began rely on objective facts and observation and to turn away from the mysticism, religion, and unfounded theorizing that had previously dominated the field. This drastic change in scientific practices and beliefs was most apparent in the field of astronomy. Physics and astronomy had been dominated by the work of Aristotle, a philosopher from the time of ancient Greece, and Ptolemy, an astronomer from the second century A.D. Astronomy was rooted in both philosophy and theology, and it was difficult for scientists to separate their work from that of the mystics or the clergy.

Through the work of the four fathers of the astronomical revolution, Copernicus, Kepler, Galileo, and Newton, both the practice of astronomy and mans view of the universe were transformed. Astronomers rejected the Ptolemaic view of the universe that had held court for centuries. They supplanted Ptolemys earth-centered universe with a new sun-centered system. These modern thinkers, far ahead of their time, persevered against the mockery, apathy, and anger of their peers. And eventually, through Newtons synthesis of math, physics, and astronomy, they triumphed. The work of these astronomers shook the world. They denied everything that humans had held certain for centuries. The excitement and confusion that these astronomers left in their wake in is reflected in John Donnes seventeenth century poem An Anatomy of the World The First Anniversarie. As he wrote, And new Philosophy calls all in doubt. Tis all in pieces, all coherence gone.

General Summary

Johannes Kepler was born in Germany in 1571, in the middle of the Scientific Revolution. The weak and sickly child was abandoned by his father Heinrich in early childhood. Because his family moved around so much, it took Kepler twice as long as usual to get through elementary school. He eventually graduated, moving on to a theological seminary and then to the University of Tuebingen. At the university, Kepler decided to pursue a graduate degree in theology, but he was soon distracted from that goal. A Protestant school in the Austrian town of Gratz offered him a job as a professor of math and astronomy. Although Kepler believed he had no special skills in those subjects, he took the job. Once there, he turned his attention toward deciphering the mysteries of the universe. Kepler was convinced that God had created a universe with some discernable pattern or structure, and he devoted himself to figuring out what it might be.

In 1595 Kepler decided that the planets were spaced as they were because the planetary orbits were arranged around geometric figures: the perfect solids. Perfect solids are three-dimensional figures whose sides are all identical, and Kepler was convinced that God had used these forms to build the universe. He elaborated on this view in his first book, the Mysterium Cosmographicum, or the Cosmic Mystery. Keplers theory was incorrect, but the book was the first major work in support of the Copernican system since Copernicuss death fifty years before. The book was also significant because Kepler was the first major astronomer in centuries to address physical reality, rather than being content with a mere mathematical description of the universe. Kepler could not quite get his data to fit his theory; he needed a source of more accurate data. He found this in Tycho de Brahe, a wealthy Danish astronomer.

Tycho was the best observational astronomer of his age, and Kepler decided that only Tychos observations would do. So Kepler traveled to Prague to work in Tychos lab. Tycho, an arrogant, demanding, and unpleasant employer, died after only a year. But Kepler worked for seven more years on the problem he had started on while there: constructing the orbit of Mars. Keplers work on Mars led him to discover his first two planetary laws: that the planets travel in elliptical orbits and that they sweep out equal areas of their orbits in equal times. He published his results in 1609 in the Astronomia Nova, or the New Astronomy, revolutionizing astronomy and greatly simplifying the Copernican system. Kepler was considered one of the top astronomers in Europealthough not because of his published work.

Few of his peers recognized the importance of his planetary laws, and few even accepted that they were true. It was difficult for his colleagues to recognize him as a scientist of the modern age, when his work remained mired in the mysticism of the past. The years just before and after the Astronomia Nova were a professional triumph for Kepler he was well known and well respected. He spent these years researching lenses, as well as astronomy, adding several major contributions to the field of optics. At the same time, his personal life was taking a turn for the worse. In quick succession, Keplers wife and favorite son died, and his patron went insane and abdicated the throne. His new home, Prague, was torn apart by civil war, and his mother was accused of being a witch. Through it all, Kepler continued to work toward his greatest goal: finding a way to explain the structure of the universe. He had been forced to abandon most of his theory of the perfect solids, and needed something new to replace it. After years of thought, he came up with a new idea: the theory of universal harmonies.

Kepler decided that the planets were spaced around the harmonic ration of another set of geometrical figures. Once again, he believed he had looked directly into the mind of God. Once again, his theory was completely wrong. Butthe pursuit of an incorrect theory led him to a stroke of scientific genius. In 1618, Kepler published the Harmonice Mundi, or the Harmony of the World, in which he explained his new harmonic theory. Keplers third law offered a specific mathematical relationship between the distance of a planets orbit from the sun and the time it took a planet to circle the sun. Kepler thought little of this law, as did his peers, because it made little sense to him at the time. It was only later, when Sir Isaac Newton created the theory of universal gravitation, that the fundamental importance of this law became clear.

Kepler continued to publish important works. In 1619, he published Epitome Astronomiae Copernicanae, a summary of the Copernican system, adjusted to accommodate Keplers laws. The Copernican system as we now know it is basically the one offered in the Epitome. Then, in 1627, Kepler published the Tabulae Rudolphine, or the Rudolphine Tables, a comprehensive list of astronomical observations, predictions, and explanations, all based on Tychos data and Keplers discoveries. Keplers final publication came a few years after his death. Though filled with scientific explanations, it is not actually a scientific work instead, it is a science fiction story. Somnium, or Dream, tells the story of a young boys trip to the moon. Much of the story seems to be a thinly veiled autobiography.

However, the Somnium was also packed with notes on the scientific ramifications of Keplers discoveries. The accuracy of his prediction of what a lunar journey would be like reveals what remarkable physical intuition he had. Kepler is perhaps the least known of the major figures of the Scientific Revolution. His lack of fame may be due to the fact that he is difficult to classify he seems less modern than the other scientists of the time, and he relies on mysticism and religion. His scientific contributions are themselves harder to simplify than those of Copernicus or Newton. But while he may be less known than his peers, Kepler is no less important. Physics and astronomy had been separated for two thousand years before Keplers birth. It was an incredible leap for him to put the two together and in doing so, he paved the way for the Newtonian revolution that was to come.

Important People, Terms, and Events


Copernicus Copernicus was a Polish astronomer and clergyman who, in 1543, introduced a new heliocentric system of the universe. In Copernicuss system, the planets revolved on a complex system of epicycles, but they all revolve around the sun. This was a revolutionary idea in the sixteenth century. Everyone was firmly convinced that the earth was motionless at the center of the universe. To imagine that it moved around the sun seemed ridiculous. It took several decades for the Copernican system to become fully accepted by astronomers and the public. Kepler was the first major astronomer to publicly acknowledge his support of it. Tycho de Brahe Tycho de Brahe was a Danish nobleman who made a name for himself in the late sixteenth century as Europes best observational astronomer. He kept a closely guarded collection of astronomical observations, the most accurate astronomical data available at the time.

Eager to use Tychos figures to develop his own system, Kepler traveled to Prague to work in Tychos lab. In addition to being a brilliant astronomer, Tycho was also an arrogant and temperamental man. Tycho and Kepler had a love-hate relationship; they respected one another, but each was also jealous of the others achievements and potential. Several times, Kepler fled the lab, only to return full of apologies. When Tycho died, he expressed a hope that Kepler would use his data to develop the Tychonic system of the universe, in which the planets orbited the sun, which orbited the earth. Instead, Kepler applied Tychos observations to the Copernican system, which led him to discover his first two laws. Galileo Galilei Galileo was an Italian astronomer who discovered the moons of Jupiter. Galileo was the first major astronomer to use a telescope to observe the heavens.

When these observations yielded findings that the scientific community was reluctant to believe, Kepler lent him public support Galileo later became a symbol of sciences break from religion during the scientific revolution. He was put on trial by the Catholic Church and convicted of heresy for his support of the Copernican system Heinrich Kepler Keplers father, Heinrich, was an itinerant criminal who repeatedly abandoned his family. At one point he owned a tavern, at another, he was nearly hanged for an alleged crime. One of Keplers younger brothers was forced to run away from home when Heinrich threatened to sell him. Heinrich left for good in 1588 he was not missed. Katherine Kepler Katherine Kepler, Keplers mother, was born Katherine Guldenmann. She was the daughter of an innkeeper and the niece of a woman who had been burned at the stake as a witch. Kepler later described her as a petty, angry, quarrelsome woman.

She came back into Keplers life in 1615, when her fellow villagers accused her of being a witch. Kepler was quick to come to her defense. After five years of argument and negotiation, Katherine was interrogated under threat of torture. When she continued to deny being a witch, she was finally released. She was driven from her town and died six months later. Michael Maestlin Michael Maestlin was Keplers most influential teacher at the University of Tuebingen. Maestlin was the first to teach Kepler about the Copernican system. In the classroom, Maestlin was a strong supporter of the Copernican system, but on paper, he continued to propound the Ptolemaic system. Kepler turned to Maestlin for help and advice throughout his life, but Maestlin seems to have grown tired of his troublesome student.

He often ignored Keplers letters for years at a time. Barbara Muehleck Kepler married Barbara Muehleck in 1597. It was a marriage of convenience, not love. Keplers friends had decided it was time for him to marry and had chosen Barbara as a good mate; Kepler acquiesced. They were married for fourteen years and had four children. Barbara died in 1611 of the Hungarian fever. Susanna Pettinger Two years after his first wife died, Kepler married the 24-year-old Susanna Pettinger. They had eleven children together and Kepler had nothing negative to say about her in later life a ringing endorsement considering the way he described most of his family members. Ptolemy Ptolemy, an astronomer from the second century A.D., formulated a system of the universe that lasted for over one thousand years after his death.

His system placed the earth at the center of the universe, with the planets and the stars revolving around it. Ptolemy insisted that the planets in his system moved with uniform circular motion. Because this is not actually how the planets move, he was forced to introduce the following mathematical devices. The deferent is the main circle around which each planet orbits the earth. An epicycle is a smaller circle around which the planet orbits the deferent. Finally, the equant is an imaginary point in the exact center of the planetary orbits. Ptolemys system was so complex that, by the time of Copernicus, it contained somewhere between forty and eighty epicycles.


Astronomia Nova · The Astronomia Nova, or the New Astronomy was Keplers masterpiece. Published in 1609, it was the result of over eight years of work. Kepler spent those years trying to work out the shape of the orbit of Mars. Using Tychos data about the motion of the planets, Kepler was finally able to determine the shape of the orbit more accurately than anyone who had come before him. This resulted in the formation of his first two laws, which were published in the Astronomia Nova. Geocentric · A geocentric system is one in which the earth is at the center of the universe. For thousands of years, scientists, philosophers, and theologians believed that the universe was geocentric. They were unwilling to believe Copernicus when he challenged that assumption. Harmonice Mundi · The Harmonice Mundi, or Harmony of the World was the culmination of Keplers life-long study of the structure of the universe. Published in 1618, it described a system in which the spacing between the planets was determined by universal harmonies. The theory was wrong, but the book is nonetheless important, as it marks the first appearance of Keplers third law. Heliocentric · A heliocentric system is one in which the sun is at the center of the universe.

The system that Copernicus introduced was a heliocentric system. This was not a completely original idea some of the philosophers of ancient Greece had imagined that the universe might be constructed in this way. However, the dominant view had always been that the universe was geocentric, so Copernicuss claims were a shock to the European system. Keplers Three Laws · Kepler is best known today for his contribution of the three planetary laws, which were instrumental in Newtons later development of his theory of universal gravitation. They are as follows: 1. The planets travel around the sun in elliptical orbits with the sun located at one focus. 2. As the planets travel around their orbits, they sweep out the same amount of area per unit of time, no matter where they are on the orbit.

3. The distance a planets orbit is from the sun, cubed, is directly proportional to the time it takes the planet to travel around the orbit, squared. Mathematically, this can be stated as a 3/p 2 = K where a is the distance a planets orbit is from the sun, p is the period, the time it takes for a planet to revolve around the sun once, and K is a constant. Mysterium Cosmographicum · Published in 1597, the Mysterium Cosmographicum, or Mysteries of the Cosmos, was Keplers first major work. It described his theory of the perfect solids, which, although he never fully admitted it, was completely wrong. More importantly, the Mysterium was Keplers first step to rejoining physics and astronomy, as he grasped for physical explanation for the structure of the universe. He was the first astronomer in centuries to do so.

It is in the Mysterium that Kepler first proposes that the sun be moved to the exact, physical center of the universe, and that a force from the sun is responsible for moving the planets around their orbits. The Mysterium was also the major work in fifty years to support the Copernican system. Perfect solid · A perfect solid a three dimensional figure, such as a cube, whose sides are all identical. There are only five perfect solids: the tetrahedron (which has four triangular sides), cube (six square sides), octahedron (eight triangular sides), dodecahedron (twelve pentagonal sides), and icosahedron (twenty triangular sides). Each perfect solid can be inscribed in and circumscribed around a sphere. In the beginning of his career, Kepler believed that the planetary orbits could all be inscribed in one of the perfect solids.

Growing Up

Johannes Kepler was born on December 27, 1571, in the small German town of Weil- der-Stadt. He was born at the tail end of the European Renaissance, an age of intellectual, religious, cultural, and scientific transformation. But Keplers own early childhood showed no such signs of enlightenment. The young Kepler was trapped in his own period of personal depression and darkness. The Kepler family tree had distinguished roots his arrogant grandfather Sebaldus Kepler had even served as town mayor. But by the time Kepler came on the scene, the family had fallen into a state of disrepair, filled with tormented personalities, hot tempers, invalids, and criminals. Sebaldus and his wife, Katherine Mueller, had twelve children. Heinrich, Keplers father, was the oldest surviving child; three others had died in infancy. When he was twenty-four years old, Heinrich married Katherine Guldenmann Johannes was their first child. Katherine had a slightly less auspicious pedigree than Heinrich. She was an innkeepers daughter whose aunt had been accused of being a witch and had been burned at the stake. Heinrich was a restless husband who abandoned his family often.

When Kepler was only three, Heinrich left to fight the Protestant armies in the Netherlands. This was a public embarrassment for the Keplers one of many that Heinrich would cause since the Kepler family itself was solidly Protestant. Heinrich came and left frequently through Keplers youth. At one point, he was accused of a crime and almost hanged. After briefly running a tavern, the itinerant Heinrich abandoned the family for good in 1588. Johannes Kepler had six brothers and sisters, three of whom died in childhood. Of the remaining three, two grew up to be normal, law-abiding citizens. The last one, Heinrich, was an epileptic who was always either sick or in trouble. He eventually ran away from home after Heinrich Sr. threatened to sell him. Historians have an incredibly detailed sketch of Keplers childhood, thanks, in large part, to the scientist himself. At the age of twenty-six, Kepler drafted a horoscope of his entire family.

He also spent a fair amount of time analyzing his own personality. Kepler recorded everything, including the time of his conception (May 16, 1571), the length of his mothers pregnancy (224 days, nine hours, and fifty-three minutes), and his own opinions of each member of his family. The image we are left with is not a pretty one. Grandfather Sebaldus was remarkably arrogantshort tempered and obstinate and Grandmother Katherine was restless, clever, and lyingan inveterate troublemaker, extreme in her hatred, a bearer of grudges Mother Katherine is described as small, thin, swarthy, gossiping, and quarrelsome. But it is Keplers father who bears the brunt of Keplers familial criticisms. In Keplers autobiographical study, Heinrich appears as a man vicious, inflexible, quarrelsome, and doomed to a bad end.

Kepler spares no one in his autobiography, least of all himself. He portrays himself as a sickly child, weak in health and personality, always picked on by other children. He describes a miserable childhood filled with illness, injury, and skin disorders. His chronological listing of events from his early days reveals that Kepler was not one to look on the bright side the list is a recital of moments of suffering and weakness. In 1575, Kepler almost died of smallpox; in 1585, he suffered from a series of sores, wounds, and skin problems. The litany of complaints breaks for only a few events, including the sighting of a comet in 1577 and, a few years later, a sighting of a lunar eclipse. As these astronomical events marked a few bright moments in a childhood of darkness, astronomy itself would soon illuminate Keplers troubled adult life.

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