Summary

Brief Biography of Kepler

     Kepler was born in 1571 to modest family. Although Kepler's father disappeared when he was 17, his mother, an intelligent woman, encouraged his curiosity. While in grammar school, Kepler displayed much interest in his education and a penchant for working things out for himself. In 1588, he was enrolled at the University of Tübingen to study theology, and studied under the mathematician Michael Mästlin in the fields of mathematics and astronomy.    Here Kepler came into contact with the Copernican system. He later abandoned his theological studies to take a job. Kepler, a Lutheran, believed that there was an order to the world instilled by God that allowed one to discover the laws that govern this universe.  According to Kepler, mathematics and geometry were the tools and principles by which God created the universe. In addition, Kepler believed that religion and science were closely tied together, and actually compared the cosmos to the Holy Trinity.

     Throughout his lifetime, Kepler published many works including the Mysterium Cosmographicum, Astronomia Nova, Harmonica Mundi, and the Rudolphine Tables. Physical cause was central in his works. The Rudolphine Tables published in 1627 were his last work.  These tables, based on the laws of planetary motion set forth in his previous works, had unprecedented accuracy. 

Mysterium Cosmographicum

    One of Kepler's first published works,  the Mysterium Cosmographicum includes the details on the construction of the universe based on the five Platonic Solids. Being an inquisitive and religious man, Kepler questioned why God chose to make six planets. Kepler came to the conclusion that God made this choice in conjuction with the five platonic solids: tetrahedron, cube, octahedron, dodecahedron, and icosahedron. These Platonic Solids nested within spheres turned out to model a fairly accurate representation of the orbital distances for the planets. In this way, Kepler began to merge mathematics and the physics of the cosmos, as the Platonic Solids not only allowed for a mathematical model of the universe, but also acted as an explanation of how and why the universe is positioned and built the way it is.  When this work reached Tycho Brahe, he was impressed and hired Kepler as one of his research assistants to work mainly with the planet Mars.  The research he did at Tycho's observatory was later the basis of his Astronomia Nova.

Astronomia Nova

     Considered to be Kepler's greatest work, the Astronomia Nova explains Kepler's new theories on planetary motion in a sun-centered universe and also the physical causes behind those motions. In the work, Kepler compares the three main astronomical systems (Ptolemaic, Copernican, Tychian) in order to draw contrasts and comparisons between them, ultimately siding with the Copernican heliocentric system. Serving as one Tycho's many assistants, he was assigned to work with Christian Severinus (Longomontanus) on a theory of Mars' orbit. This event was extremely fortunate for Kepler, as Mars is the planet whose orbit deviates enough from a perfect circle that it gave Kepler the observations that would lead him to develop his theory of elliptical planetary orbits. 

    After Tycho's death, Kepler was appointed to be his successor by the king.  Following a long legal battle with Tycho's heirs, Kepler finally had access to Tycho's detailed measurements. These data allowed Kepler to come up with a system that was both better suited to prediction and closer to today's physical truth. Due to this delay in access, the Astronomia Nova was not the book he intended to write, as James R. Voelkel argues (see reading packet).  As everything he published had to be approved by Tycho's heirs, Kepler decided to make the work so complicated that it could not be edited without harming its integrity.  In his personal, confession-style narrative, Kepler explained the problems with the older Ptolemaic system in astronomy and revealed a new system that was no longer based on uniform circular motion, but rather on elliptical motion of each planet with the sun at one focus of the ellipse. 

     In the Astronomia Nova, Kepler also explained his theory of "magnetism" present in the moon and the earth and the sun ("magnetism" being a word used for gravitational pull).  Having dismissed the arguments for a non-moving earth, Kepler went on to explain that the sun is the center of the cosmos and is also the source of the movement of the other planets.  Kepler also argued for a sun centered system on the basis of religion, which was a deep and integral part of the Astronomia Nova.  For example, Kelper argued that since the sun is very luminous, it should be in the center of the system because it is a place worthy of such a luminous body.  This way, the sun also illuminates all of the bodies in the system. Kepler based everything on physical causes in this work, uniting the astronomy and the physics of the celestial realm.

Primary Sources

 Kepler's Advice for Idiots:

"But whoever is too stupid to understand astronomical science, or too weak to believe Copernicus without affecting his faith, I would advise him that having dismissed astronomical studies and having damned whatever philosophical opinions he pleases, he mind his own business and betake himself home to scratch in his own dirt patch, abandoning this wandering about the world. He should raise his eyes (his only means of vision) to this visible heaven and with his whole heart burst forth in giving thanks and praising God the Creator." (Astronomia Nova. 24)

     A favorite quote from Kepler's Astronomia Nova.  In these two sentences, we can see several prominent features of Kepler's strong viewpoint and style of writing. He clearly adheres to a Copernican system, but still puts forth the idea that Copernicanism and Christian belief are compatible.  He also mentions eyes as "the only means of vision," referring directly back to the section of the text where he addresses the new system in the context of the Bible.  It is clear he viewed the glory of his God as the ultimate goal of his studies.  This passage also reflects Kepler's very personal writing style and his strong personality.

Key terms and Definitions

Physical Cause: Cause that one can find in nature (e.g. gravity) that explains a phenomenon