Johannes Kepler Lesson for Kids: Biography & Facts

Instructor: Deborah Stone

Deborah has taught middle level science and master's and doctorate level education leadership and environmental science.

Johannes Kepler was an astronomer and mathematician who discovered that planets and other objects travel in elliptical orbits around the sun, which led to the three laws of planetary motion. His achievements include important work in optics and math.

Who is Johannes Kepler?

Do you ever look at the night sky and see the movement of the stars and wonder how they move? Let's read further and find out how a famous astronomer and mathematician named Johannes Kepler figured it out.

Portrait of Johannes Kepler

Early Life

Johannes Kepler was born on December 27, 1571, in Weil der Stadt Würtemburg, in the Stuttgart region of Germany near France. As a child, Kepler contracted smallpox, which caused him to have poor vision. But even with poor eyesight, by age six he was extremely fascinated by the night sky. Later, around age nine, Kepler observed the Great Comet of 1577 and the lunar eclipse of 1580. These observations left him mesmerized, and these events greatly impacted his future achievements.

During his elementary years, Johannes Kepler struggled with his studies, but he worked hard and learned. Eventually, he attended college at the University of Tübengen, where he studied philosophy, astronomy, mathematics, and theology. In 1594, Johannes Kepler accepted a teaching position in Graz, Austria, where he taught mathematics and astronomy.

Kepler's Three Laws of Planetary Motion

During his time as a teacher, Kepler believed in the heliocentric model developed by Nicholas Copernicus at a time when only the Ptolemaic, or geocentric model, was allowed. The Ptolemaic model, constructed by Claudius Ptolemy in the 100s, stated that all objects revolved around the Earth. This model lasted for 1400 years, until Nicholaus Copernicus devised the heliocentric model around 1543. The heliocentric model stated that all objects revolved around the sun. Copernicus was not allowed to publish his work at the time because it was rejected by the church and other scholars, but Kepler defended it in his book Mysterium.

In 1600, Kepler met another famous astronomer, Tycho Brahe, and became his assistant. Brahe died in 1601, leaving Kepler all of his life's work and data about the orbit of the planet Mars. This is when Johannes Kepler began to realize that planets and other objects move in ellipses. By 1604, Kepler observed the supernova (an exploding star) now known as the Kepler Supernova.

Using the observation of the supernova and Brahe's work, Kepler discovered that planets move in elliptical orbits, or stretched-out ovals. This movement is now recognized as Kepler's First Law of Motion. These discoveries led to Kepler's famous Three Laws of Planetary Motion published in Astronomia Nova in 1609. Until the discovery of ellipses, most believed that planets moved in a circular path instead of elongated oval paths.


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