Johannes Kepler: Biography, Laws And Other Contributions

Johannes Kepler (1571-1630) was a German astronomer whose main contribution was the fundamental laws of the movement of the planets. He himself did not consider them laws, but part of a heavenly harmony that reflected God’s influence in the universe.

Kepler’s discoveries made it go from the Nicolas Copernicus model – with the Sun as the center of the Universe – to a dynamic Universe, with planets revolving around the Sun in non-circular orbits.

In addition, he developed an explanation of the behavior of light, discovered new semi-regular polyhedra, and proposed new principles for astrology.



Johannes Kepler was born in Weil der Stadt, Würtemburg, Germany, on December 27, 1571 and died in Regensburg (Regensburg in German), a city located in German Bavaria, on November 15, 1630.

He grew up in a once-renowned Protestant Lutheran family, but was in decline when Kepler was born.

His father, Heinrich Kepler, was a mercenary in the service of the Duke of Alba. Her mother Katharina Guldenmann, was the daughter of an innkeeper and worked as a healer.

Kepler was a sickly child and at age 3 he nearly died from smallpox, which left him with poor eyesight throughout his life. However, he overcame the consequences of an unfortunate childhood thanks to his tenacity and intelligence.


Motivated by his parents, from a very young age he was immersed in the study and observation of the stars and the universe.

Due to the difficult economic situation of the family, he had to leave school to work as a day laborer, but he was always a student. In 1584 he entered the Protestant seminary at Adelberg.

His intelligence and fascination with the Universe were so great that he won a scholarship to study at the University of Tübingen. There he studied philosophy, mathematics, ethics, astronomy, and physics, among others. Later he studied human sciences and theology.

In 1591, his professor, the astronomer Michael Maestlin, taught him the heliocentric system of Nicolaus Copernicus, which contradicted the Ptolemaic system.

In 1594 he interrupted his studies in theology and traveled to Graz (Austria), where he served as a mathematics teacher in the Protestant school. During his time as a teacher in Graz, he published a calendar with astrological predictions.

Elliptical orbits

In July 1595, Kepler had an important revelation and developed a complex geometric hypothesis to explain the distances between the planetary orbits, concluding that their orbits are elliptical.

He claimed that the Sun exerted a force that drives the planets to move around their orbits.

In 1596, he published a treatise entitled The Cosmic Mystery , defending the Copernican system. In it he explains all his doctrines related to cosmology with his vision of the existence and wisdom of God in the cosmological model.


On April 27, 1597 he married Bárbara Müller. Soon after, an edict of Archduke Ferdinand against the Protestants forced him to leave Austria, and in October 1600 he moved to Prague hosted by the Danish astronomer Tycho Brahe.

Relationship with Tyho Brahe

Tycho Brahe was a builder mathematician at the Prague Observatory, where the best observations of the Solar System were made. When Kepler arrived in Prague, Tycho Brahe gave him the study of the orbit of Mars .

Brahe and Kepler had reached a perfect collaborative relationship that was sadly interrupted by Brahe’s unexpected death.

When Brahe died in 1602, Kepler replaced him as Rudolf II’s imperial mathematician and as an astrological adviser, an occupation to which he frequently appealed to survive.

Kepler’s Laws

One of his most important works during this period was Astronomy Nova , published in Prague in 1609, where he explained the result of his studies for 5 years to calculate the orbit of Mars and planetary motion. Kepler’s first two Laws are presented in this book.

After conducting several studies based on his first two laws, he related the trajectory of the planets to each other, also known as the law of planetary motion, and formulated his third law.

Second matrimony

In 1612 the Lutherans were expelled from Prague, so Kepler moved to Linz after the recent death of his wife and two children. Later he remarried but had many personal and financial problems.

In 1617, his mother Katharina was accused of being a witch. Thanks in part to the extensive legal defense that Kepler prepared for her, she was released in October 1621.

In 1621, Kepler completed the last of seven volumes of his textbook on astronomy gathering and expanding on his work on the Copernican system.


When King Rudolf II died, and his brother Matthias of Habsburg ascended to the throne, Kepler was appointed professor of mathematics at Linz, where he resided until 1626.

In 1627, he completed the Rudolphine Tables which provided accurate calculations of the future positions of the planets and allowed the prediction of rare astronomical events.

Harassed by debts, in 1628 he went to the service of a Czech military nobleman, Albrecht von Wallenstein, in Sagan, Silesia, who promised to help him pay the debts.


Days before he died, he had left Silesia looking for a new job (Biographies and Lives, 2017).

Johannes Kepler died in Regensburg (Regensburg) on ​​November 15, 1630, at 58 years of age. His grave was demolished – two years after he was buried – by the Swedish army in the Thirty Years’ War.

Kepler’s three laws

Kepler took almost eight years to understand the retrograde motion of the planet Mars. Using Brahe’s detailed observations, he realized that the planets traveled in “stretched” circles known as ellipses.

The Sun is not exactly in the center of its orbit, but is moving to one side, at one of the two points known as the focus.

Some planets, like Earth, have an orbit very similar to a circle, but the orbit of Mars is one of the most elliptical. This fact that the planets travel on elliptical paths is known as Kepler’s First Law.

Kepler also noticed that a planet moved more slowly when it was farther from the Sun than when it was close.

Understanding that planets traveled in ellipses, he determined that an invisible line connecting the Sun to a planet covered an equal amount of area for the same amount of time, this being Kepler’s Second Law.

Kepler’s Third Law was published a decade later, and it recognized that the relationship between the period of two planets – the time they take to orbit the Sun – corresponds to their distance from the Sun.

While Kepler’s first two laws focus on the details of the motion of a single planet, the third law is a comparison between the orbit of two planets.

Other contributions

Although Kepler is best known for his laws that define planetary motions, he also made other notable contributions to science:

-Determined that refraction drives vision in the eye, and that the use of two eyes allows depth perception.

-He created glasses for myopia and hyperopia.

-Explained the operation of the telescope.

-He described the properties of reflection.

-He stated that gravity depends on two bodies instead of one, claiming that the Moon is the cause of the movement of the tides on Earth.

-He mentioned the rotation of the Sun and created the word “satellite.”

-He tried to use his knowledge to measure the distance to the stars.

-Made several contributions to mathematics, including the creation of faster calculation methods.

-Investigated the volume of many solid bodies.

-Calculated the year of Christ’s birth.

-He was the first to explain the principles of the telescope.

-Your book Stereometrica Doliorum was the basis of the integral calculus.

Mathematics, astronomy and astrology

In addition to teaching mathematics in Graz, Kepler became a district mathematician. In this position, he drew up the calendars of his time that were to include useful information for people’s daily lives.

The information included advice to farmers on when to plant crops, advice to leaders on military campaigns, advice on matters of romance, etc.

In Kepler’s time there was considerable confusion both in the general community and in the universities regarding the distinction between astronomy and astrology.

As part of this process, Kepler published a book in 1601 that “rejected the superstitious view that the stars guide the lives of human beings” and progressively rejected other aspects of astrology.


In recognition of Johannes Kepler’s contributions to understanding the motion of the planets, NASA named its planet-searching telescope after the German astronomer.

Kepler and God

Many of Kepler’s writings reflect his deep desire to bear witness to the glory of God. On one occasion, he wrote:

“I was simply thinking of the thoughts of God after Him. Phen we astronomers are priests of the Most High God with respect to the book of nature, it benefits us to be thoughtful, not of the glory of our minds, rather, above all, of the glory of God.

Expressing the humility that characterized, and eager to develop a personal relationship with God, Kepler reflected:

“Can I find God, who in the contemplation of the entire universe I can almost feel in my hands, also in myself?”


  1. Bellis M. Johannes Kepler – Astronomy. Recovered from
  2. DeVore E. Kepler and Mars – Understanding How Planets Move. Recovered from
  3. Fowler M. Johannes Kepler. Recovered from
  4. Lamont A. Johannes Kepler (1571-1630). Outstanding scientist and committed Christian. Recovered from
  5. Rabin S. Johannes Kepler. Recovered from
  6. Sobel D. Searching Heaven and Earth for the Real Johannes Kepler. Recovered from Discover Magazine; Nov 2008.
  7. Taylor N. Johannes Kepler: Biography. Recovered from

Add a Comment

Your email address will not be published. Required fields are marked *