Date: December 17, 2009

Title: An Interview with Johannes Kepler


Podcaster: John McFarland and Thomas Covington

Links: Johannes Kepler website

Description: Thomas Covington, a middle school student, interviews Johannes Kepler. Kepler talks about his early years in Weil der Stadt including his father and his schooling. He also discusses the current astronomical beliefs between 1590 and 1605. In addition, several aspects of everyday life are covered including the Gregorian/Julian Calendar issue and the expulsion of all Protestants from southern Austria.

Bio: John McFarland is a retired school teacher living in Charleston, South Carolina. He is president and founder of the Johannes Kepler Project and splits his time between speaking to students about the Founders of Modern Astronomy as Johannes Kepler and speaking to teachers about astronomy resources. Learn more at

Today’s sponsor: This episode of 365 Days of Astronomy is sponsored by Chester Chua, who dedicates this episode to the organizers of this podcast and to everyone who is contributing to our knowledge. I’d also like to specially dedicate the podcast to my Four sons, Kebo, Neale, Samuel and Moz. May Your curiosity take you All to New and Better Worlds.


T.C. Hello, my name is Thomas Covington and I am here in Charleston, SC on assignment from my school. Today I will be interviewing one of the founders of modern astronomy, Johannes Kepler. Good morning Mr. Kepler or is it Professor Kepler.

J.K. Good morning, Thomas and good morning to everyone. I never taught at the university, just call me Herr Kepler.

T.C. Herr Kepler, we just studied about you in school and I was wondering if it’s true that that you worked for Tycho Brahe and that he had a golden nose.

J.K. Yes Thomas, I did work for Tycho and he did have a golden nose that he wore on special occasions but for everyday use he had a nose made of a lighter metal.

T.C. How did Tycho Brahe lose his nose?

J.K. While studying at the university Tycho got into an argument lead to a sword fight and during the sword fight his nose was cut clean off!

T.C. Would you tell us a few things about your life?
J.K. I was born on December 27, 1571 in a small village called Weil der Stadt in the black forest region of what you know today as Germany. My father Heindrich was a poor man, he had no skills and became a Mercenary, that’s a paid solider. He was hired by King Philip of Spain, a catholic, to go to Holland and kill Protestants. The interesting thing about this is that my grandfather, my father and I are all Protestants; today we would be considered Lutherans. My mother traveled with my father and I was raised by my grandparents. The first school I attended was the German School and then I went to the Latin School. Next I attended several protestant schools and then I was lucky enough to win a scholarship to the all protestant, University of Tubingen. It’s only a two days walk from my village. I was being educated by the church to become a Lutheran minister.
My favorite subjects at the university were mathematics and astronomy. In astronomy class we learned that the earth was not flat, it is spherical. We know this because its curved shadow can be seen on the moon during a lunar eclipse. But we were also taught that the moon, the sun, the planets and all the stars orbit the earth. This idea of the earth being the center of everything was over a thousand years old, everyone knew it was so and it does appear to be that way during the day and the night. For instance, doesn’t the sun rise, move across the sky, and set, and then it pops up the next morning to do it again. Not really but it looks that way. And at night we can see the stars moving around the earth, right? Not really but it looks that way. In reality it is the earth that is spinning. Doing the day the sun doesn’t really move and during the night the stars aren’t moving either, it’s the earth that’s spinning. During my time the thought that the earth could spin and also orbit the sun was a brand new idea first proposed by an amateur astronomer from Poland a few years before I was born. Perhaps you’ve heard of him. Nicolas Copernicus.
Although astronomy was my favorite subject I was studying to be a Lutheran minister so after graduating from the university with a BA degree I still have two years of religious studies to go. But six months before I was to become a Lutheran minister I was asked by the church to go to Graz, Austria to teach mathematics in a small protestant school. And I agreed to go! I never became a minister.
When I arrived in Graz, I discovered that I had lost 10 days. That’s because Graz was using the new Gregorian calendar named after Pope Gregory but in protestant Germany we were using the old Julian calendar named after Julius Caesar. Things were very weird in Europe, Christmas and Easter were celebrated 10 days sooner in Sweden and England than in Italy and Spain.

T.C. Why two calendars?

J.K. Well Thomas, over hundreds of years the old Julian calendar had lost time because it wasn’t accurate enough and the holidays like Easter and Christmas and the longest and shortest days of the year were no longer in synch with the seasons, everything was 10 days behind. To fix the problem Pope Gregory wanted everyone to skip forward 10 days and also to add more leap years. You’re probably thinking, why everyone didn’t just switch to the new calendar. Well, the Protestants and the Catholics didn’t like each other so the Protestants didn’t want to switch to the new calendar because the idea came from the Catholics.
But let’s get back to my favorite subject, Me. Those few years in Graz, Austrian was great years for me. I met and married my wife Barbara and I wrote my first book about astronomy, it supported the ideas of Copernicus. One of my other duties in Graz was to make the calendar for all of southern Austria each year. It took an astronomer to make a calendar because only astronomers knew how to set the date for Easter. Did you know that Easter is always the first Sunday after the first full moon after the vernal equinox?
I only taught in Graz for about two years because Graz was mostly catholic and in 1597 the young Roman Catholic archduke Ferdinand II closed all the protestant churches and schools and I lost my job. I remained in Graz for another two years earning a living by making calendars and maps. But in 1599 Ferdinand II forced all the Protestants to either become Catholics or to leave southern Austria. That’s when I left and headed north in the hopes that I could get a job in Prague with Tyco Brahe, he had just been hired as the Imperial Mathematician to the Holy Roman Emperor.
I did get a job with Tycho and my first task was to calculate a more precise orbit for the planet Mars. I thought it would take a few months to figure things out but it took much, much longer. I worked for Tycho for about a year and a half but when Tycho died in the fall of 1601 I inherited his position as imperial mathematical and then it became my job to write horoscopes for the Holy Roman Emperor and to calculate more precise orbits for the planets.
It took five years but I finally figured out why astronomers had been puzzled by the orbits of the planets for over 1000 years. People thought things in the universe were perfect and that the most perfect shape was the circle, so people thought all orbits had to be perfect circles. But that is not how things really work in space, orbits are oval shaped; in math we call this shape an ellipse. Once you know that orbits are elliptical and not circular it’s not too difficult to calculate where the planets or even comets will be in a month or a year or a century. Based on this new idea of elliptical orbits I was able to discover what you know today as Kepler’s three laws of planetary motion.

T.C. We just studied your laws did you also discover other things?

J.K. Yes Thomas. I studied the human eye and figured out what caused people to be far and near sighted. I also figured out that when a ray of light goes through a piece of curved glass, like a lens, it will bend. I also studied Galileo’s telescope and suggested ways to improve its design.

T.C. Did you know Galileo?

J.K. Yes but we never met, we exchanged letters. When Galileo discovered that Jupiter had moons, he wrote a book and became very famous. I was one of the first people to receive one of his books and within ten days I wrote a small book of my own supporting his discovery. I was the first scholar to support Galileo and his discoveries.

T.C. We are almost out of time. What is the most important thing you would like to tell people?

J.K. To be a good scientist you have to be curious about things and really like what you do but above all else you must have an open mind. Things are not always what they appear.

T.C. This is Thomas Covington reporting from Charleston, SC and I have been talking to Johannes Kepler about his life from the years 1571 to 1630. Thank you Herr Kepler!

J.K. Thank you, Thomas.

End of podcast:

365 Days of Astronomy
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