Space Pioneers Series – Johannes Kepler

A 1610 portrait of Johannes Kepler by an unknown artist

A 1610 portrait of Johannes Kepler by an unknown artist

They are the dreamers, the deep-thinkers, the “what if-ers”, the folks who have peppered our history with those tiny nuggets of brilliance which, with much blood, sweat, tears, and perseverance, have been successfully mined to launch the greatest technological developments our world has ever known. But sheer brilliance often brings on harsh criticism and negativity from others who won’t or simply can’t dare to dream.

One aspect of our technological development that has suffered at the hands of such criticism is that of space exploration. Thankfully, our world has known dreamers too tenacious to fail, even in the face of naysayers who would keep their dreams at bay—boxed up in some dark corner, never to prosper or flourish.

KnowledgeOrb will be periodically featuring some of these space pioneers, to celebrate their tenacity and capacity to dream up innovations that were far ahead of their time. We owe them our gratitude for forging ahead even in the face of ridicule and contempt, in order to bring us closer to the many incredible wonders that our beautiful, limitless universe holds.

Read:Space Pioneers Series – Robert Goddard 

Today, we honor the founder of “celestial mechanics”, Johannes Kepler.

Kepler made his way into this world on December 27, 1571, a sickly child born into a poor family in Weil der


Kepler’s model to explain the relative distances of the planets from the Sun in the Copernican System

Stadt, Germany. His childhood was far from idyllic, having contracted smallpox at age three, which left him scarred and damaged his eyes. His father was a mercenary soldier and was often away for months and sometimes even years at a time. When his mother joined his father abroad, she left him in his grandfather’s care. Although the separation from his parents was difficult, Kepler’s grandfather nurtured his inquisitive nature and his religious faith, and encouraged him to soak up as much knowledge as he could in his young life.

When Kepler’s parents returned years later, his father opened an inn, and, rather than fostering his love of learning, he saw his son as cheap labor and forced him to stop going to school so that he could work at the inn. Determined to continue his education, Kepler, with encouragement from former teachers, eventually earned a scholarship to the University of Tübingen, where he initially studied theology with the goal of becoming a Lutheran pastor. It was there that he was first exposed to the work of Nicolaus Copernicus, who would prove to have an enormous influence on his future contributions to space studies.

For a long time, I wanted to become a theologian. Now, however, behold, how through my efforts God is being glorified through astronomy.”

Kepler’s mathematics and astronomy professor, Michael Mästlin, was one of the few professors of that time who

had accepted Copernicus’ idea that the planets revolved around the sun. Almost all scholars of that era still believed that the earth was the center of the solar system. This would spark a lifelong and insatiable curiosity in Kepler, who began to be consumed with studying planetary motion and determining logical patterns amidst what was, at the time, thought to be chaos.

Kepler obtained his B.A. degree in 1588 and his M.A. degree in 1591. In 1594, he was asked to teach mathematics at the Lutheran high school in Graz, Austria. It was here that he began to cultivate his unique and controversial theories about our solar system.

While teaching in Graz, Kepler also held the position of district mathematician, which involved land surveying and calendar-making. Through his work with calendars, he began studying phases of the moon in order to help with the calendar content. At that time, it was expected that calendars include advice to farmers on when to plant and harvest crops, and other predictions such as advice to leaders of military campaigns, and matters of romance.

Dubious about the validity of astrology (versus what he deemed the more-scientific astronomy), Kepler decided that he would check the accuracy of his predictions. His results were eventually published in his book, On the More Certain Fundamentals of Astrology, which “rejected the superstitious view that the stars guide the lives of human beings”. Kepler progressively rejected other aspects of astrology as well.

Johannes was the first scientist to investigate the long term accuracy of astrology. His records showed that trusting in astrology could be a risky business.” —J. H. Tiner

Kepler’s earlier theological studies, coupled with the strong sense of faith instilled in him by his grandfather, helped formulate his belief that, “the world of nature, the world of man, the world of God—all three fit together.” He reasoned that, because the universe was designed by an intelligent Creator, a logical pattern of order should be apparent. The thought that the universe was instead governed by chaos seemed to him to be inconsistent with God’s teachings.

We see how God, like a human architect, approached the founding of the world according to order and rule and measured everything in such a manner.”

It was with this thought in mind that he set out to discover patterns behind the motion of planets, basing his work on philosophy and mathematics of the ancient Greeks. He discussed his theories in his 1595 book, Cosmic Mystery, which put him on the radar of renowned Danish astronomer, Tycho Brahe.

Brahe was quite impressed with Kepler’s application of mathematics to astronomy, and he invited him to join his team of astronomers. And so in 1600, Kepler joined Brahe at his observatory in Prague. Brahe’s team had charted planet paths for many years, they could not see any logical order in the data they had collected. Kepler was charged with the task of studying the orbit of Mars.



Johannes Kepler’s original drawing depicting the location of the Stella nova explosion , in the constellation of the Serpentarius, marked with an N (8 grid squares down, 4 over from the left) and a Hubble Space Telescope view of the remnants of it.

During his investigations, Kepler began to see that the widely-accepted theory that planetary motion was circular could not be true. He started trying “noncircular paths” until he hit upon the notion of elliptical orbits. This was his first law of planetary motion:

Planets move in ellipses with the Sun at one focus.

He went on to demonstrate that planets do not move equal distances at constant speeds, balking another popular theory. Instead, he was able to show that a planet travels faster when it’s closer to the sun, establishing his second law of planetary motion:

The radius vector describes equal areas in equal times.

It would take ten years for him to establish his third law of planetary motion. This principle used math to relate the time a planet takes to complete an orbit of the sun to the average distance away from the sun:

The squares of the periodic times are to each other as the cubes of the mean distances.

Kepler’s two first laws were published in a 1609 book, The New Astronomy. In 1619, he published the third law in the book, Harmony of the Worlds. He used this book as a mouthpiece for his faith as well, noting that, “Great is God our Lord, great is His power and there is no end to His wisdom.”

Kepler was a devoted family man, but his personal life was filled with tragedy. After enduring an unhappy and sickly childhood, he suffered the deaths of three of his six children during their own childhoods, as well as the death of his first wife. He was the victim of repeated religious persecution, as he refused to abandon his own beliefs when they differed from those who were in power at the time. He was shunned by the Catholic church and excommunicated from the Lutheran church. To add to his burdens, Kepler’s mother, always a superstitious woman, was tried for witchcraft, and would have suffered torture and burning at the stake if it weren’t for his skillful arguments on her behalf.

Through it all, his faith remained unshaken; in fact, it seemed to fuel his work and allowed him to become the founder of celestial mechanics, as we know him today. While Kepler’s laws of planetary motion were his greatest contributions to science, he made a great impact in other areas as well:

  • Discovered a new star (a supernova);
  • Analyzed how the human eye works
  • Made improvements to the telescope
  • Published accurate data on the positions of stars and planets which were of immense value to navigators.
  • Made various contributions to mathematics, including faster methods of calculation, and investigated the volume of many solid bodies.
  • In addition, he wrote a story called The Dream which is credited as being the first modern science-fiction story.

Today, NASA honors this space pioneer with his namesake mission, Kepler, which is NASA’s first mission capable of finding Earth-size planets around other stars

Read:Over One Thousand Exoplanets found in Two Decades 

The Kepler instrument is a specially designed telescope called a photometer. Its large field of view, as compared to other astronomical telescopes, allows it to observe the large number of stars. The photometer fixates on the same star field for the entire mission, and continuously monitors the brightness of more than 100,000 stars. The large diameter of the telescope allows it to measure small changes in brightness of an Earth-like transit.

When a planet passes in front of his parent star, it blocks a fraction of the light from that star, which is known as transiting. If repeated transits are observed, a planet has been discovered. The change in the brightness also allows astronomers to determine the size of the planet, and the time between transits allows them to learn more about the size of the planet’s orbit and its temperature, both of which are determining factors when looking at whether or not the planet could sustain life.

Since the search began in 2009, astronomers, using the planet-hunting Kepler spacecraft, have discovered 2,740 planet candidates orbiting other suns.

“…the ways by which men arrive at knowledge of the celestial things are hardly less wonderful than the nature of these things themselves.”

Johannes Kepler died on November 15, 1630, in Regensberg, Germany, died after battling an illness. It is said that he died with fellow scientists Galileo Galilei and Isaac Newton seating near him. He wrote his own epitaph prior to his death; it is both poetic and pragmatic—the perfect legacy for this troubled, yet gifted man, to which we owe a debt of gratitude for his amazing contributions to space studies.

I used to measure the heavens, now I measure the shadows of Earth. Although my mind was heaven-bound, the shadow of my body lies here.”

About the author

Writer for many journals and publications. Professional in the aerospace industry.