Johannes Kepler: Much more than just an Astronomer

Johannes Kepler was born December 27, 1571, in Weil der Stadt, Württemberg [Germany]. He died November 15, 1630, Regensburg)

Kepler was a German astronomer, mathematician, astrologer, natural philosopher and writer on music. He was a key person of influence in the 17th-century Scientific Revolution.

Kepler is best known for his laws of planetary motion, and his books Astronomia nova, Harmonice Mundi, and Epitome Astronomiae Copernicanae.

His work was of great influence on Isaac Newton and many others. Kepler provided the foundational theory of universal gravitation. The variety and impact of his work made Kepler one of the founders of modern astronomy, the scientific method and natural science in general.

Kepler’s God was a dynamic, creative being whose presence in the world was symbolized by the Sun’s as the dynamic force that continually moved the planets. The natural world was like a mirror that precisely reflected and embodied these divine ideas.

Inspired by Platonic notions of the soul, Kepler believed that the human mind was ideally created to understand the world’s structure.

“I used to measure the heavens,
now I shall measure the shadows of the earth.
Although my soul was from heaven,
the shadow of my body lies here”.

Kepler was not alone in believing that nature was a book in which the divine plan was written. He differed, however, in the original manner and personal intensity with which he believed his ideas to be embodied in nature. One of the ideas to which he was most strongly attached was the image of the

Christian Trinity as symbolized by a geometric sphere. The visible, created world, was literally a reflection of this divine mystery (God the Father: center; Christ the Son: circumference; Holy Spirit: intervening space).

One of Kepler’s favorite biblical passages came from John (1:14).

“And the Word became flesh and lived among us.”

For him, this signified that the divine archetypes were literally made visible as geometric forms that configured the spatial arrangement of tangible entities.

Kepler was the astronomer who discovered the three major laws of planetary motion.

1. Planets move in elliptical orbits with the Sun at one focus.
2. The time necessary to traverse any arc of a planetary orbit is proportional to the area of the sector between the central body and that arc (the “area law”).
3. There is an exact relationship between the squares of the planets’ periodic times and the cubes of their mean distances from the Sun (the “harmonic law”).

Kepler himself did not call these discoveries “laws”. It became the customary term after Isaac Newton derived them from a new and different set of general physical principles. He regarded them as celestial harmonies that reflected God’s design for the universe.

Kepler’s discoveries turned Nicolaus Copernicus’s Sun-centered system into a dynamic universe. He discovered that the Sun is actively pushing the planets around in non-circular orbits. It was Kepler’s notion of a physical astronomy that fixed a new problem for other important 17th century world-system builders, the most famous of whom was Newton.

Among Kepler’s many other achievements, he provided a new and correct account of how vision occurs. He developed a novel explanation for the behavior of light in the newly invented telescope.

The history of the telescope can be traced to before the invention of the earliest known telescope, which appeared in 1608 in the Netherlands. A patent was submitted by Hans Lippershey, an eyeglass maker. Although Lippershey did not receive his patent, news of the invention soon spread across Europe. The design of these early refracting telescopes consisted of a convex objective lens and a concave eyepiece. Galileo improved on this design the following year and applied it to astronomy.

In 1611, Kepler described how a far more useful telescope could be made with a convex objective lens and a convex eyepiece lens. By 1655, astronomers such as Christian Huygens were building powerful but unwieldy Keplerian telescopes with compound eyepieces.

Kepler discovered several new, semi-regular polyhedrons. He also offered a new theoretical foundation for astrology. The list of his discoveries, however, fails to convey the fact that they constituted for Kepler, part of a common body of knowledge. His matrix of theological, astrological, and physical ideas from which his scientific achievements emerged is unusual and fascinating in its own right.

The highly original nature of Kepler’s discoveries requires an act of intellectual empathy for modern science to understand. How could have such lasting results evolved from such an unlikely complex set of ideas. He is considered by the modern scientific community as a bit of a scientific enigma.

Although his scientific work was centered primarily on astronomy, it was classified as part of a wider subject of investigation called “the science of the stars.”

The science of the stars was regarded as a mixed science consisting of a mathematical and a physical component. It bore a kinship to other like disciplines, such as music (the study of ratios of tones) and optics (the study of light). It also was subdivided into theoretical and practical categories.

Kepler believed the theoretical principles of astrology had a corresponding practical part that dealt with the making of annual astrological forecasts about individuals, cities, the human body, and the weather. Within this framework, Kepler made astronomy an integral part of natural philosophy, but he did so in an unprecedented way.

Astronomers looking to the sky — Scanned 1870 Engraving

There was no “scientific community” as such in the late 16th century. All schooling in Germany, as elsewhere, was under the control of church institutions. This was primarily Roman Catholic or Protestant. Local rulers used the churches and the educational systems as a means to consolidate the loyalty of their populations.

One means to this end was a system of scholarships for poor boys who, once having been trained in the schools of the duchy (territory of the duke), would feel strong loyalty to the local ruler.

Kepler came from a very modest family in a small German town called Weil der Stadt and was one of the beneficiaries of the ducal scholarship. This made possible his attendance at the Lutheran Stift, or seminary, at the University of Tübingen, in 1589. It was expected that the boys who graduated from these schools would go on to become schoolteachers, ministers, or state functionaries. Kepler had planned to become a theologian.

People have always named things after people who have done great things. Most people with an interest in science and Astronomy have heard of the Kepler telescope (image on left) launched by NASA in 2009 but is no longer in service today. Here is a list of just some of the many other things that were named after Kepler out of respect for his contributions to Science and Astronomy:

Kepler conjecture Kepler triangle Kepler–Bouwkamp constant

Kepler–Poinsot polyhedron

Kepler’s laws of planetary motion

Kepler’s equation Keplerian elements Kepler problem

Kepler problem in general relativity

Kepler space telescope Kepler Launch Site

Kepler photometer Keplerian telescope Kepler refractor Johannes Kepler ATV

Kepler (lunar crater) Kepler (Martian crater) Kepler Dorsum 1134 Kepler

Kepler orbit Kepler Object of Interest Kepler-11 Kepler-22 Kepler-22b

Kepler’s Supernova Kepler Follow-up Program Kepler Input Catalog

Kepler scientific workflow system Kepler Mire Kepler Museum Kepler Track

Kepler College Johannes Kepler University Linz