Johannes Kepler
Johannes Kepler (ˈkɛplɐ; December 27, 1571 – November 15, 1630) was a German
The Germans are a Germanic ethnic group native to Central Europe. The English term Germans has referred to the German-speaking population of the Holy Roman Empire since the Late Middle Ages....

A mathematician is a person whose primary area of study is the field of mathematics. Mathematicians are concerned with quantity, structure, space, and change....

, astronomer
An astronomer is a scientist who studies celestial bodies such as planets, stars and galaxies.Historically, astronomy was more concerned with the classification and description of phenomena in the sky, while astrophysics attempted to explain these phenomena and the differences between them using...

 and astrologer
An astrologer practices one or more forms of astrology. Typically an astrologer draws a horoscope for the time of an event, such as a person's birth, and interprets celestial points and their placements at the time of the event to better understand someone, determine the auspiciousness of an...

. A key figure in the 17th century scientific revolution
Scientific revolution
The Scientific Revolution is an era associated primarily with the 16th and 17th centuries during which new ideas and knowledge in physics, astronomy, biology, medicine and chemistry transformed medieval and ancient views of nature and laid the foundations for modern science...

, he is best known for his eponym
An eponym is the name of a person or thing, whether real or fictitious, after which a particular place, tribe, era, discovery, or other item is named or thought to be named...

ous laws of planetary motion
Kepler's laws of planetary motion
In astronomy, Kepler's laws give a description of the motion of planets around the Sun.Kepler's laws are:#The orbit of every planet is an ellipse with the Sun at one of the two foci....

, codified by later astronomers, based on his works Astronomia nova
Astronomia nova
The Astronomia nova is a book, published in 1609, that contains the results of the astronomer Johannes Kepler's ten-year long investigation of the motion of Mars...

, Harmonices Mundi, and Epitome of Copernican Astronomy. These works also provided one of the foundations for Isaac Newton
Isaac Newton
Sir Isaac Newton PRS was an English physicist, mathematician, astronomer, natural philosopher, alchemist, and theologian, who has been "considered by many to be the greatest and most influential scientist who ever lived."...

's theory of universal gravitation
Newton's law of universal gravitation
Newton's law of universal gravitation states that every point mass in the universe attracts every other point mass with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them...


During his career, Kepler was a mathematics teacher at a seminary
A seminary, theological college, or divinity school is an institution of secondary or post-secondary education for educating students in theology, generally to prepare them for ordination as clergy or for other ministry...

 school in Graz
The more recent population figures do not give the whole picture as only people with principal residence status are counted and people with secondary residence status are not. Most of the people with secondary residence status in Graz are students...

, Austria, where he became an associate of Prince Hans Ulrich von Eggenberg
Hans Ulrich von Eggenberg
Hans Ulrich von Eggenberg was an Austrian statesman, a son of Seyfried von Eggenberg and great-grandson of Balthasar Eggenberger of the House of Eggenberg.- Biography :...


Discover the force of the heavens O Men: once recognised it can be put to use.

De Fundamentis [On the more Certain Fundamentals of Astrology or On Giving Astrology Sounder Foundations] (1601)

He who will please the crowd and for the sake of the most ephemeral renown will either proclaim those things which nature does not display or even will publish genuine miracles of nature without regard to deeper causes is a spiritually corrupt person… With the best of intentions I publicly speak to the crowd (which is eager for things new) on the subject of what is to come.

De Fundamentis (1601)

Nature uses as little as possible of anything.

Viking Book of Aphorisms: A Personal Selection (1920) by W. H. Auden and Louis Kronenberger, p. 98; also in The Infinite Cosmos: Questions from the Frontiers of Cosmology (2006) by Joseph Silk

We do not ask for what useful purpose the birds do sing, for song is their pleasure since they were created for singing. Similarly, we ought not to ask why the human mind troubles to fathom the secrets of the heavens. The diversity of the phenomena of nature is so great and the treasures hidden in the heavens so rich precisely in order that the human mind shall never be lacking in fresh nourishment.

As quoted in Cosmos (1980) by Carl Sagan.

In Terra inest virtus, quae Lunam del.

There is a force in the earth which causes the moon to move.

Geometry has two great treasures; one is the Theorem of Pythagoras; the other, the division of a line into extreme and mean ratio. The first we may compare to a measure of gold; the second we may name a precious jewel.

As quoted in The Golden Ratio : The Story of Phi, the World's Most Astonishing Number (2003) by Mario Livio, p. 62

I much prefer the sharpest criticism of a single intelligent man to the thoughtless approval of the masses.

As quoted in (K)new Words: Redefine Your Communication (2005) by Gloria Pierre, p. 147

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.

Epitaph he composed for himself a few months before he died, as quoted in Calculus. Multivariable (2006) by Steven G. Krantz and Brian E. Blank. p. 126