Early life in which Milanković was born today houses the
Cultural and Scientific Center "Milutin Milanković" Milutin Milanković was born in the village of
Dalj, a settlement on the banks of the
Danube in what was then part of
Austro-Hungarian Empire. Milutin and his twin sister were the oldest of seven children raised in a
Serb family. As a result, Milutin and his siblings were raised by his mother, grandmother, and an uncle. His three brothers died of
tuberculosis at a young age. As his health was fickle, Milutin received his elementary education at home, learning from his father Milan, private teachers, and from numerous relatives and friends of the family, some of whom were renowned philosophers, inventors, and poets. He attended
secondary school (realgymnasium) in nearby
Osijek, completing it in 1896. In his third year of studies, Milanković found more free time for wider education. He paid his full attention to the monumental buildings of Vienna, thereby gradually understanding all the beauty of architecture. He also visited Viennese museums and galleries, after which he became an admirer of Raphael's
Madonna del Prato. He showed great interest in the
Vienna Opera, which he visited regularly. In addition, he devoted his attention to learning the French language by taking private lessons and attending summer French language course in
Geneva in 1899. During a stay in
Switzerland, Milankovitch visited the
Institute for the Testing Building Materials in the
Polytechnic in Zurich. In the Viennese ″Café Elisabethbrücke″, which was not fashionable but served only for reading, he spent an hour or two daily reading numerous newspapers and magazines. The professor of the science of the building bridges, , the top expert of Viennese Mechanics of that time, taught the most important subject of the fifth school year. In Brikʼs teaching, young Milankovitch found strong inspiration for later scientific work, as he describe it: ″Brikʼs lectures were very interesting to me. His mastering of mathematical analysis was excellent and would constantly apply it in his lectures. To a good mathematician it gives certain independence and freedom in solving problems.″ After graduating and spending his obligatory year in military service, Milankovitch borrowed money from an uncle to pay for additional schooling at TU Wien in engineering. At age twenty-five, his
PhD thesis was entitled
Contribution to the Theory of Pressure Curves (Beitrag zur Theorie der Druckkurven) and its implementation allowed assessment of pressure curves' shape and properties when continuous pressure is applied, which is very useful in bridge, cupola and abutment construction. His thesis was successfully defended on 3 December 1904; examination committee members were Johann Emanuel Brik,
Josef Finger,
Emanuel Czuber and
Ludwig von Tetmajer. He then worked for an engineering firm in Vienna, using his knowledge to design structures.
Middle years Structural engineering At the beginning of 1905, Milanković took up practical work and joined the firm of Adolf Baron Pittel Betonbau-Unternehmung in Vienna. He built dams, bridges, viaducts, aqueducts, and other structures in
reinforced concrete throughout Austria-Hungary. So Milankovitch verified his theoretical knowledge and design tools on numerous reinforced concrete structures that he built during his engineering service in Vienna. Milankovitch participated with structural calculations and practical work in the construction of a total of ten
hydroelectric power plants. Among them, the most notable is the one built in
Sebeș (present-day Romania) in the
Transylvania region. Milankovitch's specific task was to design a reinforced concrete
aqueduct 1200 m long, which would bring water above the
turbines of the city's hydroelectric power plant. After that, he was engaged in the construction of the
viaduct in Hirschwang (
Semmering) in 1906 and in
Pitten near Vienna in 1907. He also participated in the construction of bridges in
Krainburg, Banhilda and
Bad Ischl, then the Belgrade and
Košice sewage system, and Krupp's metal factory in
Berndorf. The bridge in Krainburg (130 meters long and seven meters wide) was particularly beautiful, set on three pillars with four arches each, 30 meters apart. It was built of reinforced concrete, but was later destroyed during
World War II. Milankovitch's great reputation was certainly contributed to by inventions of a new technology of building reinforced concrete ceiling, under the name "System Milankovitch - Kreutz", with which he became famous throughout the Austria-Hungary. He developed and patented the mentioned system of building ceilings with Theodor Kreutz. Compared to the existing ones, this ceiling stood out due to its simpler design, lower consumption of materials and the fact that it had integrated thermal and sound
insulation, which made it more aesthetically elegant. In 1905, he published the first paper on armored concrete named
Contribution to the theory of reinforced armored pillars. He published the second paper on the same subject based on new results in 1906. In 1908, he published a paper titled "On membranes of same opposition" in which he proves that the ideal shape for a
water reservoir of equally thick walls is that of a
drop of water. His six patents were officially recognized and his reputation in the profession was enormous, bringing abundant financial wealth. In 1908, the Austro-Hungarian Empire decided to
annex Bosnia and Herzegovina after 30 years of occupation. This was the height of a
crisis with the neighboring Kingdom of Serbia, which did not agree with this act. And, there was even a growing danger of war and invasion. Milanković continued to practice civil engineering in Vienna until 1 October 1909 when he was received an offer
University of Belgrade to work as an associate professor at the Department of
Applied Mathematics that comprised three basic branches:
rational,
celestial mechanics, and
theoretical physics. Though he continued to pursue his investigations of various problems pertaining to the application of reinforced concrete, he decided to concentrate on fundamental research. Although this was the turning point in Milankovitch's career, he still does not abandon his "passion for the entire range of construction work, from theoretical ideas to craftsmanship", and continues to engage in design and construction, in parallel with his scientific work. Thus, after arriving in the
Kingdom of Serbia, Milanković accepted the design and construction of the first reinforced concrete bridges on the
Niš -
Knjaževac railway, in the
Timok Valley through the Nisevac Gorg, at the request of his friend and collegemate from TU Wien and civil engineer Petar Putnik. This undertaking was unique in that, at the suggestion of engineer Putnik, the type construction of a reinforced concrete bridge was applied for the first time in Serbia. The project of the 30-meter-span bridge, which rests on rocky shores, was done by Milanković with the aim of easier and faster construction of the railway on the route of which the construction of 19 bridges was planned. Thanks to this simple approach, the construction of all 19 bridges is solved with one project. That is precisely why Putnik's construction company won this job at the public procurement in 1912, when construction began. Milanković participated in the construction of the first of the nineteen bridges, which was located near Svrljig, where he fully immersed himself in the work and took care of how "the concrete is mixed, distributed over the formwork and compacted". Meanwhile, Milankovitch was granted citizenship of the Kingdom of Serbia in 1910.
Planet's insolation His first papers were in the field of celestial mechanics,
Properties of motion in a specialized three-body problem (1910),
On general integrals of the n-body problem (1911),
On kinematic symmetry and its application to qualitative solutions of dynamics problem (1912), but from 1912 Milankovitch began to be interested in cosmic climatology or solar climate. He began working on it in 1912, after he had realized that "most of meteorology is nothing but a collection of innumerable empirical findings, mainly numerical data, with traces of physics used to explain some of them... Mathematics was even less applied, nothing more than elementary calculus... Advanced mathematics had no role in that science..." The possibility of astronomically-forced climate changes was first considered in the 19th century, by astronomers such as
John Herschel and geologists like
Louis Agassiz. Milanković studied the works of
Joseph Adhemar, whose pioneering theory on the astronomical origins of ice ages were formally rejected by his contemporaries, as well as the janitor-turned-scientist,
James Croll, whose work was effectively forgotten after an initial acceptance by contemporaries such as
Charles Darwin. His next paper was entitled "''Distribution of the sun radiation on the earth's surface
" and was published in June 1913. In December of that year, this paper was read by Wilhelm Wien, and was soon published in the German journal Annalen der Physik''. He correctly calculated the intensity of
insolation and developed a mathematical theory describing Earth's climate zones. His aim was an integral, mathematically accurate theory which connects thermal regimes of the planets to their movement around the Sun. He wrote: "...such a theory would enable us to go beyond the range of direct observations, not only in space, but also in time... It would allow reconstruction of the Earth's climate, and also its predictions, as well as give us the first reliable data about the climate conditions on other planets." He published a paper entitled "The problem of the astronomical theory of ice ages" in 1914. Milankovitch married Kristina Topuzović, an amateur opera singer, on 14 June 1914. They decided to go on their honeymoon to Switzerland, but before that they stopped in Milankovitch's native village of Dalj in Austria-Hungary, where they heard that
Franz Ferdinand had been assassinated in Sarajevo which was the cause of the
July crisis. Meanwhile, the Austro-Hungarian Empire began massing troops in the
Balkans near the border with the Kingdom of Serbia in
preparation for an invasion. Milankovitch was soon arrested by the Austro-Hungarian authorities because he was a reserve officer in the Royal Serbian Army and at first he spent six weeks under house arrest, but was eventually imprisoned and later sent to a prisoner-of-war camp (K. u. K. Interienirungslager) in Nezsider, Hungary (today
Neusiedl am See, Austria). He described his first day in prison, where he waited to be taken to the
Esseg fortress as a prisoner of war, in the following words: ... Sat on the bed, I looked around and started synchronizing with my new social position .... In the suitcase I had my printed works and my notes on the cosmic problem, there was clean paper too and I started writing. It was far past midnight when I stopped. I looked around the room, wondering where I was. It felt like I was in a roadhouse on my trip through the Universe. Milanković spent four years in Budapest, almost the entire war. He knew the size of Mars and its distance from the Sun, but also that it has a similar rotation speed and axis orientation as Earth. Milanković calculated that the average temperature in the lower layers the atmosphere on
Mars is and the average surface temperature is . Also, he concluded that: "This large temperature difference between the ground and lower layers of the atmosphere is not unexpected. Great transparency for solar radiation makes that is the climate of Mars very similar to altitudes climate of our Earth." In any case, Milanković's work suggested that Mars has a harsh climate, and calmed mounting enthusiasm concerning the prospect of discovering the presence of liquid water on the surface of Mars. According to his own words, Milankovitch did not know the speed of rotation of Venus, the orientation of the axis, as well as the
thickness and composition of the atmosphere. He was awere with
Schiaparelli's suggestion that Venus has a slow rotation period equal to the duration of its orbits around the Sun, but he was skeptical because he thought that Venus would lose its atmosphere during a long-term day due to the effects of solar radiation. At the last, he accepted
spectroscopy observations from that time that suggested a shorter rotation period similar to Earth's. So he considered a
greenhouse effect (water vapor) on Venus calculated the temperature in the outer limit of the atmosphere , the upper layer , the middle layer and the lower layer of the atmosphere as well as a ground temperature of . In his literary work
Through Distant Worlds and Times, he described of Venus in the following words: Here we are in the temple of Isis and Osiris, more magnificent than Schinkel himself imagined. From its huge dome, covered with a gently mother-of-pearl mosaic, a white mysterious light spills over the interior of this home. That dome, that's the sky of Venus. The Sun is never visible on it, only the Sun's silvery glow. Not a single star twinkles in this sky; no messenger of the universe reaches this sanctuary...What is this? A storm is raging in my head, blood vessels are beating like sledgehammers, I'm out of breath. You are pale, dear miss, your legs are wobbly - you have completely fainted... Half unconscious, I carry you, in my arms, to our Earth... He also discussed the possibility of
life on Venus. He thought that the mystery of this planet lies in the answer to the question about its axis, the speed of rotation or how long a day lasts on Venus. His calculations of the surface temperature conditions on the neighboring
Moon are particularly significant. Milankovitch knew that the moon rotates on its axis in 27.32 days, so lunar daytime on one side of the moon last about 13.5 Earth days. Milankovitch calculated that the temperature after a long moon night, in the early morning on the Moon, or before the rise of the Sun over horizon, was . At noon, it rises on , only to reach its maximum value one Earth day later . At sunset, the temperature drops . According to Milankovitch, a sudden cooling occurs during the night. From 1912 to 1917, he wrote and published seven papers on mathematical theories of climate both on the Earth and on the other planets. He formulated a precise,
numerical climatological model with the capacity for reconstruction of the past and prediction of the future, and established the astronomical theory of climate as a generalized mathematical theory of insolation. When these most important problems of the theory were solved, and a firm foundation for further work built, Milanković finished the manuscript under the title
Mathematische Grundlagen der kosmischen Strahlungslehre that he sent to his Professor Czuber in Vienna at the summer of 1917. Czuber contacted a publishing house in
Leipzig, but since there was a shortage of paper in early 1918, the printing of the book was cancelled. In the fall of 1917, Milankovitch got a job in a construction bureau in Budapest, where he worked on detailed projects of reinforced concrete constructions of a new six-story tuberculosis
sanatorium built in the
High Tatras, as well as on other important projects. After the
Great War, the Austro-Hungarian Empire disintegrated and new states such as the
Kingdom of Serbs, Croats and Slovenes,
Republic of Austria,
Kingdom of Hungary and
Czechoslovak Republic were formed on its remains. Milanković returned from Budapest to Belgrade with his family after a three-day trip by
steamboat ″Gizella″ on 19 March 1919. That same year, he was elected a corresponding member of the
Serbian Royal Academy of Sciences in Belgrade and the Yugoslav Academy of Science and Arts in Zagreb.
Orbital variations and ice ages As a consequence of the
Russian Civil War, with the arrival of Russian scientists – emigrants, the personnel base of the Faculty of Philosophy at the University of Belgrade was expanded. Thus, from 1920 Anton Bilimovich (1879–1970), a distinguished scientist, who came from
Odessa, took over the lectures on rational mechanics, and from 1925 the lectures on theoretical physics and vector theory were taken over by the newly elected assistant professor Wenceslas S. Jardetzky (1896–1962). Between the two wars, Milankovitch taught celestial mechanics and occasionally the theory of relativity, and after the Second World War until 1955, when he retired, he taught celestial mechanics and the history of astronomy. Milankovitch's works on astronomical explanations of ice ages, especially his curve of insolation for the past 130,000 years, received support from the climatologist
Wladimir Köppen and from the geophysicist
Alfred Wegener. Köppen noted the usefulness of Milanković's theory for
paleoclimatological researchers. Milanković received a letter on 22 September 1922 from Köppen, who asked him to expand his studies from 130,000 years to 600,000 years. He accepted Köppen's suggestion that cool summers were a crucial factor for
glaciation and agreed to calculate the secular progress of insolation of the Earth at the outer limit of the
atmosphere for the past 650,000 years for parallels of 55°, 60° and
65° northern latitude, where the most important events of the
Quaternary glaciations occurred. Milankovitch, in his early works, used the astronomical values of
Stockwell-
Pilgram. In September of that year, he attended the lecture given by Alfred Wegener at Congress of German Naturalist in
Innsbruck. That same year, he was elected a full member of the Serbian Royal Academy of Sciences. The Meteorological service of the
Kingdom of Yugoslavia became a member of
International Meteorological Organization – IMO (founded in
Brussels in 1853 and in
Vienna in 1873) as a predecessor of present
World Meteorological Organization, WMO. Milanković served as a representative of the Kingdom of Yugoslavia there for many years. Milanković put the Sun at the center of his theory, as the only source of heat and light in the Solar System. He considered three cyclical movements of the Earth:
eccentricity,
axial tilt, and
precession. Each cycle works on a different time-scale and each affects the amount of solar energy received by the planets. Between 1925 and 1928 Milanković wrote the popular-science book
Through Distant Worlds and Times in the form of letters to an anonymous woman. The work discusses the history of astronomy, climatology and science via a series of imaginary visits to various points in space and time by the author and his unnamed companion, encompassing the formation of the Earth, past civilizations, famous ancient and renaissance thinkers and their achievements, and the work of his contemporaries, Köppen and Wegener. In the "letters", Milanković expanded on some of his own theories on astronomy and climatology, and described the complicated problems of celestial mechanics in a simplified manner. Köppen proposed to Milanković on 14 December 1926 to extend his calculations to a million years and to send his results to
Barthel Eberl, a geologist studying the Danube basin, as Eberl's research had unearthed some evidence of previous Ice Ages from before over 650,000 years ago. Eberl published all this in Augsburg in 1930 together with Milanković's curves. In 1927, Milanković received an offer from Köppen to collaborate on the Handbook of Climatology (Handbuch der Klimatologie), which was edited by Köppen himself. That same year, Milanković asked his colleague and friend,
Vojislav Mišković, to collaborate in the work and calculate astronomical values based on the
Le Verrier method. Mišković was a well-established astronomer from the
Nice Observatory, who became the head of the
Astronomical Observatory of the University of Belgrade and a professor of Theoretical and Practical Astronomy. Milanković used these values in his later works. This textbook used
vector calculus systematically to solve problems of celestial mechanics. His original contribution to celestial mechanics is called Milanković's system of vector elements of planetary orbits. He reduced six
Lagrangean-
Laplacian elliptical elements to two vectors determining the mechanics of planetary movements. The first specifies the planet's orbital plane, the sense of revolution of the planet, and the orbital ellipse parameter; the second specifies the axis of the orbit in its plane and the orbital eccentricity. By applying those vectors he significantly simplified the calculation and directly obtained all the formulas of the classical theory of secular
perturbations. Milanković, in a simple but original manner, first deduced Newton's law of gravitation from Kepler's laws. Then Milanković treated the two-body and the many-body problems of celestial mechanics. He applied vector calculus from
quantum mechanics to celestial mechanics. Meanwhile, in 1936 he attended the Third symposium of the
International Union for Quaternary Research (INQUA) in Vienna. Milanković became convinced that the continents 'float' on a somewhat fluid subsurface and that the positions of the continents with respect to the axis of rotation affect the
centrifugal force of the rotation and can throw the axis off balance and force it to move. Wegener's tragedy additionally motivated Milankovich to persevere in solving the problem of polar wandering. Milanković began working on the problem of the shape of the Earth and the position of the Earth's poles in 1932 and 1933 at the suggestion of Alfred Wegener. The Earth as a whole he considered as a
fluid body, which in the case of short-duration forces behaves as a
solid body, but under an influence behaves as an
elastic body. He drew a map of the path of the poles over the past 300 million years and stated that changes happen in the interval of 5 million years (minimum) to 30 million years (maximum). He found that the secular pole trajectory depends only on the configuration of the
terrestrial outer shell and the instantaneous pole position on it, more precisely on geometry of the Earth mass. In his conclusion about this problem, he wrote: For an extraterrestrial observer, the displacement of the pole takes place in such a way that the ... Earth's axis maintains its orientation in space, but the Earth's crust is displaced on its substratum. Milankovitch's trajectory of polar wandering was a topic of discussion after World War II. In the 1950s, paleomagnetic data showed different results than Milankovitch's theoretical numerical values for polar wandering trajectory.
Later life To collect his scientific work on the theory of solar radiation that was scattered in many books and papers, Milanković began his life's work in 1939. Milanković spent two years arranging and writing the "Canon". The manuscript was submitted to print on 2 April 1941 – four days before the
attack of Nazi Germany and its allies on the Kingdom of Yugoslavia. In the
bombing of Belgrade on 6 April 1941, the printing house where his work was being printed was destroyed; however, almost all of the printed sheet paper remained undamaged in the printing warehouse. After the successful occupation of Serbia on 15 May 1941, two German officers and geology students came to Milanković in his house and brought greetings from Professor of
Freiburg. Milanković gave them the only complete printed copy of the "Canon" to send to Soergel, to make certain that his work would be preserved. Milanković did not take part in the work of the university during the occupation, and after the war he was reinstated as professor. The "Canon" was issued in 1941 by the
Royal Serbian Academy, 626 pages in quarto, and was printed in
German as "Kanon der Erdbestrahlung und seine Anwendung auf das Eiszeitenproblem".
Tower of Babel After the war, in 1947, Milanković's only son emigrated from the new communist
Yugoslavia via
Paris,
London and
Egypt to
Australia. Milanković would never see his son again and the only way of correspondence between them would be through letters. Milanković was vice president of the
Serbian Academy of Sciences (1948–1958). In 1948, the General Assembly of the
International Astronomical Union was held in
Zürich. Milankovich is listed as a member of Commission 7 for Celestial Mechanics, and "V. Mishkovitch" as member of Commission 19 for Latitude Variation and Commission 20 for Minor Planets. For a short period, he was the head of the Belgrade Observatory (1948 - 1951). At that time, the
Cold War between
nuclear powers began. In 1953, he was at the Congress of the
International Union for Quaternary Research (INQUA) held in
Rome where he was interrupted during his speech by numerous opponents since
radiocarbon dating at that time showed different results than his theory. In the same year, he became a member of the Italian Institute of
Paleontology. In November 1954, fifty years after receiving his original diploma, he received the Golden Doctor's diploma from the Technical University of Vienna. In 1955, he was also elected as a corresponding member to the
Academy of Naturalists "Leopoldina" in
Halle,
Saxony-Anhalt,
East Germany. At the same time, Milankovitch began publishing numerous books and
textbooks on the history of science, including ''Isaac Newton and Newton's Principia
(1946), The founders of the natural science Pythagoras – Democritus – Aristotle – Archimedes
(1947), History of astronomy – from its beginnings up to 1727
(1948), Through empire of science – images from the lives of great scientists
(1950), Twenty-two centuries of Chemistry
(1953), and Technology in Ancient times'' (1955). In 1955, Milankovitch retired from the position of professor of
celestial mechanics and the
history of astronomy at the University of Belgrade. In the same year, he published his last work, which is not from the natural sciences, but from his original profession of structural engineering. The paper was titled
The Tower of Babel of modern technology. Milankovitch in this work calculated the highest building possible on our Earth. He was inspired by work of
Pieter Bruegel the Elder's
Tower of Babel (older version in Vienna). The building would have a base radius of 112.84 km and a height of 21646 m. Since the building penetrates the Earth 1.4 km, it would have a height of 20.25 km above the Earth's surface. At the very top, there would be a wide platform for a meteorological and astronomical station. In September 1957, Milutin suffered a
stroke and died in
Belgrade in 1958. He is buried in his family cemetery in
Dalj. ==On the speed of light==