Johannes Kepler (1571-1630) was an outstanding German scientist, philosopher, mathematician, mechanic, astronomer, and optician who made a number of important discoveries. But the most famous of these are, of course, the laws of planetary motion, now known as Kepler's laws.
The scientist was born on December 27 in Weil der Stadt, a suburb of Stuttgart (Baden-Württemberg), into a poor Protestant family. From childhood, Johann showed an interest in mathematics and astronomy, impressing those around him with his abilities.
The young Kepler owed his hobbies primarily to his mother—it was she who once showed the boy a comet and a lunar eclipse (1580). After graduating from a Protestant school and a first and second degree seminary (1588), he studied at the Tübingen Academy (1589-1593). There he first heard about the ideas of Nicolaus Copernicus and immediately became a supporter of his heliocentric system, although at that time astronomy was taught based on Ptolemy's geocentric system. “Young Kepler,” said the professors, “is endowed with such an outstanding mind that we can expect great achievements from him.” In two years, he completed a course at the Faculty of Liberal Arts, where mathematics and astronomy were taught at the time, and obtained a master's degree. However, the young man did not intend to pursue a career in science and continued his education at the Faculty of Theology, which he entered in 1591. Due to his student's exceptional abilities, the university senate petitioned to keep Kepler's scholarship for the entire duration of his studies.
However, Kepler was not destined for a spiritual career. On March 13, 1594, as the best graduate, he was sent to the Austrian city of Graz to teach mathematics. During one of his lessons, when Kepler was explaining the motion of Jupiter and Saturn in the celestial sphere, he came up with the idea that the relationship between the parameters of planetary orbits is determined by the properties of certain geometric objects. He was fascinated by this idea. The result of the young scientist's further reflections was his first major work, The Secret of the Universe (1596), in which he attempted to establish a numerical relationship between the distances of the planets from the Sun and the sizes of regular polyhedrons. His work became known to Galileo Galilei, professor of mathematics at the University of Padua, and Tycho Brahe, Europe's foremost astronomer.
J. Kepler was the first in the world to conclude that all planets are subject to the force of the Sun, which causes them to move in their orbits. Although the idea does not correspond to the principles of Newtonian dynamics (planets move by inertia, and solar gravity only distorts their paths), it led Kepler to the very important conclusion that planets must move faster the closer they are to the Sun.
In 1600, due to religious persecution by Catholics, he moved to Prague. Tycho Brahe invited him to work on the archive of observations and compile tables of planetary motions based on it, which were proposed to be named after the Holy Roman Emperor and King of Bohemia, Rudolf. But in 1601, Tycho Brahe died unexpectedly. Johannes Kepler received the materials of his many years of highly accurate observations, in particular regarding the motion of Mars. They formed the basis of Kepler's theory of planetary motion and, ultimately, immortalized the name of their creator. He also became the court mathematician of Emperor Rudolf II, under whom, incidentally, he rose to the position of chief astrological advisor.
Kepler lived in Prague for 11 years – the most peaceful and productive of his life. Among the works published in Prague was a treatise on optics, “Supplement to Vitellius” (1604) on the application of optics to astronomy, in which he discussed astronomical refraction and pointed out the glow that appears around the Sun during a total solar eclipse—the solar corona—and also presented for the first time the law of diminishing illumination (inversely proportional to the square of the distance from the source). In another treatise, “Dioptrics” (1611), Kepler described the telescope he invented, the so-called “Kepler's telescope” (built in 1613 by Christoph Scheiner). It should be noted that virtually all subsequent refracting telescopes were built according to Kepler's system.
In 1609, he enriched the history of science with another Keplerian treatise. The scientist published his famous “New Astronomy,” devoted to the study of the motion of Mars based on Brahe's observations. This work contains the first two laws of planetary motion formulated by him. As a result of careful analysis, Johann Kepler concluded that the trajectory of Mars is not a circle but an ellipse, at the focus of which is the Sun—a position now known as Kepler's first law. Further analysis led the scientist to discover the second law: the farther a planet is from the Sun, the slower it moves. The publication of this book brought Kepler European fame.
In 1610, Kepler began collaborating with Galileo Galilei and even published his own telescopic observations of the moons of various planets.
In 1604, the scientist observed a new bright evening star in the starry sky and noticed a nebula around it. Such a phenomenon can only be observed once every 800 years! After this unique sight, Johannes Kepler checked the astronomical properties of the star and even began to study the celestial spheres. His calculations of parallax in astronomy brought him to the forefront of this science and strengthened his scientific reputation.
Due to life's troubles and religious misunderstandings, in 1612, Johannes Kepler moved to Linz (Austria), where he got a job as a mathematician on the condition that he would continue working on tables of planetary motions and engage in local cartography. It was here in 1619 that he wrote his “Harmony of the World,” in which he formulated the third law, which unified the theory of the motion of all planets into a coherent whole: the ratio of the cube of a planet's distance from the Sun to the period of its revolution around the Sun is a constant for all planets. This made it possible to calculate the speed and period of rotation of the planets around the Sun. Kepler also derived the “Kepler equation,” which is used in astronomy to determine the position of celestial bodies. In this treatise, the scientist pays much attention to questions of world harmony, as well as geometry and philosophy.
He considered the world to be the realization of a certain numerical harmony. In 1611, Kepler published a treatise entitled “On the Six-Cornered Snowflake,” which marked the beginning of research in the field of regular and irregular structures (Hilbert's 18th problem, the solution to which was only obtained in 1998 with the help of computer calculations). In 1619, Kepler published his work “On Comets.”
Kepler's work “A Compendium of Copernican Astronomy” (1622, in three volumes) contains the conclusion that the first two laws established for Mars apply to all planets and to the motion of the Moon around the Earth, and the third law also applies to the four satellites of Jupiter. It presented Copernicus' astronomy in detail. Here, the scientist outlined the theory and methods of predicting solar and lunar eclipses. Kepler included this work in the description of his discoveries in astronomy.
The scientist worked in Linz for over 14 years.
Johannes Kepler lived in poverty during the last years of his life. The Thirty Years' War and the intensification of persecution of Protestants forced him to seek refuge in Ulm. There, in 1627, he completed his last major work, Rudolphine Tables, which summarized his many years of work processing Brahe's observations. The tables made it possible to calculate the positions of the planets with high accuracy for any moment in time in a convenient form. The ephemerides calculated by Kepler on the basis of these tables allowed him to predict the passage of Venus across the Sun's disk, which took place in 1631.
During his lifetime, Johannes Kepler earned some extra money by compiling horoscopes. In 1628, he became an astrologer for the military commander Duke Albrecht Wallenstein and lived in the town of Zagan (now Żagań, Poland) until 1630. In August 1630, Wallenstein was removed from his post without paying Kepler the promised salary.
Johannes Kepler died on November 15, 1630, at the age of 59 in Regensburg, having caught a cold on the road, which he had set out on in the hope of recovering at least part of the money he had earned. This happened just before he was to observe the passage of Mercury and Venus, which he had been eagerly awaiting.
Kepler's last work, the fantasy novel “The Dream,” was published after his death in 1634. It tells the story of a journey to the moon. It was probably the first science fiction work in world literature...
Kepler published many books and articles. His remarkable mathematical abilities were evident not only in his astronomical works, but also in his determination of the volumes of bodies (New Stereometry of Wine Barrels, 1615). To do this, he used elements of integral calculus. These were the first steps on the path to the analysis of infinitesimals and the invention of mathematical analysis. Using original methods, he found the volumes of many rotating bodies. Immediately after the discovery of logarithms, Kepler formulated a detailed theory of their use for calculations (1614) and compiled tables of logarithms, similar in structure to modern ones (1624). He also made his mark on the history of projective geometry, as he was the first to introduce the important concept of an infinitely distant point.
In physics, Kepler used the term “inertia” to describe the natural property of bodies to resist applied force. He reasoned about the force of gravity acting between celestial bodies and explained the tides of the Earth's oceans by the influence of the Moon. The scientist said: "I define gravity as a force similar to magnetism—mutual attraction. The force of gravity is greater when both bodies are closer to each other."
His entire life was devoted to substantiating and developing Copernicus' heliocentric theory. Kepler's laws became the basis of theoretical astronomy and were explained in Newton's mechanics, in particular in the law of universal gravitation.
Finally, Kepler's idea of explaining the properties of the universe on the basis of fundamental geometric symmetries has been revived in modern particle physics.
It is difficult to imagine that such an extraordinary scientific achievement belongs to only one person who lived and worked almost half a millennium ago.
In honor of J. Kepler, a university in Linz, craters on the Moon and Mars, asteroid 1134, and the supernova SN 1604 (Kepler's Supernova) described by him were named after him.
It is symbolic that a space telescope launched by NASA on March 6, 2009, to search for and study planets outside the Solar System was named in his honor. Thus, Kepler continued his exploration of the depths of space into the 21st century!
The life and work of the scientist were studied in the 20th century by K. L. Baev ("The Creators of New Astronomy. Copernicus. Bruno. Kepler. Galileo,“ 1955), O. P. Moroz (”Is Truth Beautiful?“ 1989), V. E. Beloruchkin (”Kepler, Newton, and Everything Else..." 1990), and others. In 1972, Yu. M. Medvedev wrote and published the historical novel “Captain of the Starry Ocean. Kepler.” These books are available in the collections of the G. I. Denisenko Scientific and Technical Library of the KPI.
Among other works, the library's collections also include Kepler's works. These are “New Stereometry of Wine Barrels” (translated by G. M. Sveshnikov, 1935) and “On Hexagonal Snowflakes” (published by the USSR Academy of Sciences, 1982). Thus, Kepler's research is available to our contemporaries and future generations of scientists.