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Milankovitch, Milutin

Republished From: Encyclopedia of Earth

May 7, 2012, 5:08 pm
caption Milutin Milankovitch.

Milutin Milankovitch (1879-1958), a Serbian astrophysicist and geophysicist best known for his theory of ice ages, relating variations of the Earth's orbit and long-term climate change, now known as Milankovitch cycles. These ideas were derived from improved methods of calculating variations in Earth's eccentricity, precession, and tilt through time and determining their combined effects on long term climate change. Although Milankovitch cycles do appear to explain some aspects of long-term climate change, shorter term changes, like the current global warming trend on Earth, are not due to Milankovitch cycles. 

Biography

Milutin Milankovitch (1879-1958) is best known for Milankovitch cycles, long term changes in Earth’s orbit and rotation that is the leading theory to explain the comings and goings of ice sheets over the past few million years. He is one of history’s great theoretical climatologists.

Milankovitch (also spelled Milankovi?.) was born in 1879 in Dalj, a Serbian settlement on the banks of the Danube in what was then part of Austro-Hungary and is now in Croatia. Milutin and his twin sister were the oldest of seven children. Their father was a businessman and local politician who died when Milutin was eight and his mother, grandmother and an uncle then raised the children. Those three also ran the family businesses, including a general store and numerous farmland holdings.

The young Milutin was small for his age and had little interest in sports or any other physical activity but he did have a keen mind. He found school to be easy and he excelled at mathematics. At seventeen he moved to Vienna, Austria to study Civil Engineering at the Technical High School (more like a college today). Here, too, his schooling was easy for him and in his ample free time he attended the opera, theater, museums, and other cultural amenities of the great city.

After graduating and spending an obligatory year in military service, Milutin borrowed money from an uncle to pay for additional schooling at the Technical High School in engineering. He researched concrete and wrote a theoretical evaluation of it as a building material. At age twenty-five, he proudly became the first Serbian Doctor of Technical Sciences. He then worked for an engineering firm in Vienna, using his knowledge to design structures. He obtained several patents relating to methods of building with reinforced concrete.

But being a full time engineer was not to be Milutin’s profession. Working on his dissertation convinced him that he loved scientific research and he saw that as his life’s passion.  On his own, he further developed his abilities in mathematics, physics and astronomy. In 1909, Milutin left Vienna because political events made it difficult for Serbs to live in Austria. Fortunately, he was offered a ‘Chair of Applied Mathematics’ at the University of Belgrade in Serbia. There he taught rational mechanics, celestial mechanics, and theoretical physics and began scientific research. Within a year he changed his citizenship from Austro-Hungarian to Serbian.

Milutin’s research plan was to find a challenging problem in science and spend the rest of his life solving it. It also needed to use his mathematical abilities. He had limited library resources and was far removed from the scientific centers of Europe, so he knew that competing on cutting edge topics would be difficult. For this reason, Milutin sought a problem that others were not pursuing. He began to investigate meteorology, but most of the research at the time involved data analysis and not the interplay between math and physics that he found most rewarding. Two papers, however, sparked his interest. They were theoretical papers on the receipt of solar energy over Earth’s surface. He found fatal flaws in both papers and decided to pursue the subject on his own. His early research on meteorology also introduced him to the topic of ice ages and he saw an opportunity to explain the climatic variations involved in the advances and retreats of the ice sheets.

He outlined a two part ‘cosmic problem’ to solve, with an astronomical and a physical component. The orbits of the planets around the Sun are highly predictable and vary over time. Each planet’s axis of rotation also varies over time in both the angle of the tilt and the direction the axis points. Each cycle works on a different time scale and each affects the amount of solar energy received by the planets. Others had suggested that these cycles may have caused the ice ages, but Milankovitch sought to investigate the issue with enough detail to solve the problem.

The physical part of his cosmic problem was to describe how the Sun’s rays determine the temperature on Earth’s surface after passing through the atmosphere. His goal here was to develop a mathematical theory describing Earth’s climate zones. If he could achieve this for the present climates, he could use his astronomical findings to determine climates of the past and future. He began publishing papers on various aspects of his research in 1912.

In 1914, when he was thirty five years old, Milutin married Christine Topuzovi?, the thirty year old daughter of an old merchant family who had studied to be an opera singer.  After they married, though, she only sang for family and friends. Two weeks after they wed, a Serb assassinated Prince Ferdinand of Austria and the Austro-Hungarian Empire declared war on Serbia. Milutin became a prisoner of war and was sent to a camp in Hungary. Christine traveled to Vienna and asked Milutin’s former mathematics professor to intervene on his behalf. After six months in the camp, he was allowed to live in Budapest if he reported to the police every week, agreed that his correspondence would be examined, and obtained permission for any travel. There, Christine and he lived for the duration of the First World War and their son Vasko, their only child, was born in 1915. During this time Milutin pursued his scientific interests with the help of the Hungarian Academy of Sciences.

After five years, the family returned to Belgrade, which became the capital of the newly created Yugoslavia. From his research in Budapest, Milutin wrote a book and soon found an opportunity to have it published. He wrote it in German but had to translate it into French for publication. Mathematical Theory of Heat Phenomena Produced by Solar Radiation appeared in 1920 and presented his theories on both the astronomical and physical parts of his cosmic problem. In the book he calculated, using physical principles, the average yearly temperature at various latitudes on Earth and his values were reasonably close to the empirical temperature record. Satisfied that he could calculate present temperature patterns, he predicted climates over the last 130,000 years, accounting for changes in the shape of Earth’s orbit, the tilt of the axis of rotation and timing during the year of the equinoxes. He also calculated the temperatures of the other planets and the Moon.

For a short time after his book was completed, Milankovitch worked on stellar astronomy, checking Einstein’s assertion that the speed of light is constant regardless of the speed of the light source. But in 1922, he received a letter from the German climatologist Wladimir Köppen. Köppen and his son-in-law Alfred Wegener were working on climates of the past and asked Milankovitch if he would join them in the endeavor. He had already calculated past climates for 130,000 years and Köppen felt that his results matched the geomorphological evidence of glaciations in Europe. But the glaciations extended back at least 600,000 years, so Milankovitch was asked to extend his work further back in time. They agreed that he would calculate solar radiation changes at the top of the atmosphere at 55°, 60° and 65° North Latitude. Summer temperatures, they felt, were particularly important with respect to the onset of glaciations, due to the melting of winter snowfall. After he determined the correct procedure to follow, he spent 100 days doing the calculations and prepared a graph of the variations in the receipt of solar radiation. Geomorphologists then used the graph to see if it agreed or disagreed with the field evidence of glaciations.

caption Milankovitch calculated solar energy receipt during summer at 65°N for the past 600,000 years (also for 55° and 60°, but they are not shown here). The solid line shows variation in insolation relative to the present. A value of 70°, for example, shows that at that time in the past, summer insolation at 65° is the same as received at 70° today and, therefore, colder than the present. A value less than 65° represents warmer conditions than at present. At the time Milankovitch did his work, it was generally assumed that four glaciations had occurred in the Alps during the Pleistocene, named Günz, Mindel, Riss and Würm. The dashed line is Köppen and Milankovitch’s schematic estimation of these glaciations and intervening interglacials. Glaciologists have since determined that many more than four glaciations have occurred and that the Pleistocene is one to two million years old, not 600,000. (Adapted from Figures 48 and 49 of Milankovitch, 1941.)

In 1923, Milutin found himself with a new line of research. The Eastern Orthodox Churches met to discuss reform of the Julian Calendar, which, due to the complication of leap years, was thirteen days behind the Gregorian Calendar used in the West. Milankovitch was asked to revise the calendar to make it more consistent astronomically, including a way to determine the date of Easter each year. His proposal was accepted but, for various bureaucratic reasons, never was implemented. Eventually, most of the Eastern Orthodox regions converted to the Gregorian Calendar.

Milankovitch first met Wegener in 1924 while attending a conference in Innsbruck, Austria and the two spent a late night at a beer garden discussing their work. Wegener gave an outline of his theories of continental drift and past climates the next day. His discussion of climatic changes during the Quaternary drew heavily on Milankovitch’s work. The next year, Milutin and his family vacationed in a small town in Austria near Graz, where Wegener and Köppen lived. The three became close friends, both personally and professionally.

The next year, Milutin tried his hand at popular writing with a series of magazine articles on astronomy and astronomers. Each month for three years he wrote a letter to an imaginary friend about visiting something in the universe or journeying to the past to visit an astronomer. These were published in a Serbian magazine and later collected in a book, Through Distant Worlds and Times, published in Serbian and later in German. It was the best selling book of his career. He thoroughly enjoyed this literary deviation from his research work.

In 1926, Milutin was asked to supervise the construction of twelve large hangars for the Yugoslav Air Force, to be made of reinforced concrete. He worked again as a civil engineer, part time, for the next ten years. This improved his financial situation, at least somewhat. He felt that the engineering work gave him a break from science and re-invigorated his intellectual abilities. He also felt that he did some of his best science during this time.

Köppen asked Milankovitch to write the introductory portion of a multivolume Handbook of Climatology in 1927. Köppen felt that Milankovitch’s theoretical approach to solar energy was the logical topic to begin the series. Milutin used this as an opportunity to expand his theory of the effects of the atmosphere on solar energy. He also considerably improved and expanded his work on the three astronomical cycles and their effects on climate. When he finished his section, the publisher decided that it was important enough to warrant its own book and published it in 1930, in German, as Mathematical Climatology and Astronomical Theory of Climate Change.

Conversations with Wegener got Milankovitch interested in the interior of the Earth and the movement of the Poles and he told his friend that he would investigate polar wandering. Unfortunately, Wegener died in 1930 during a research expedition to Greenland, but Milutin carried out his promise. He 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. He drew a map of the path of the North Pole over the past 300 million years, but carefully pointed out all of the simplifying assumptions he had to make in order to make his predictions. Unlike his climate studies, Milankovitch’s polar wandering work is not particularly influential in modern geophysical research.

In the late 1930s, Milankovitch revised his theories and presented them in his most lasting work, Canon of Insolation and the Ice Age Problem. Its six parts dealt with the orbits of the planets and their mutual perturbations, Earth’s rotation, the movements of the poles, changes in the receipt of solar radiation, the relationships between solar radiation and the atmosphere, and the Ice Ages. As the book was being printed in Belgrade, Germany declared war on Yugoslavia and the city was bombed, including the printing plant. Fortunately for science, only the last thirty two pages were destroyed. They were reprinted once paper could be obtained and the book was bound and published in 1941.

Soon the Nazis occupied Belgrade and its surroundings. Finding food for his family and others less fortunate became a daily undertaking for Milankovitch but he looked for something to do to occupy the rest of his time. Since his life’s work in climatology was completed, he set out to write his memoirs and a popular history of science. His memoirs, in Serbian, were published in three volumes.  Through the Realm of Science, the history, was written as a series of personal events in the lives of great scientists.

After the War, Yugoslavia became a communist country. Milankovitch’s son Vasko and his wife escaped and eventually immigrated to Australia. Milutin and Christine, though, felt that they were too old to leave their home. Because of his international reputation, he had somewhat more independence than most of his fellow citizens.

Milutin suffered a stroke in 1957 and he died the next year. He is buried in his family cemetery in Dalj. Christine died a few years later.

Some comments from Vasko Milankovitch on his father:

Father was barely 5’7” tall (1.70 m) and of fine frame. He had a prominent forehead and bushy brows over brown eyes which are always alert and quietly smiling. …He was not the bespectacled-professor-type of scientist as he enjoyed nature and loved all things aesthetically harmonious and maintained a constant interest in history, literature, painting and sculpture. …His love for abstract pleasures did not preclude him from earthy enjoyment. He enjoyed a glass of fine wine with his meals and would later relax with a favourite cigar. He often shared a good joke, and not necessarily a clean one either. (xxvi-xxvii)

Mother was the master of our family. Father would call her the “Home Secretary,” and always showed her great respect. He was the well-looked-after guest with no household duties.
He was popular with the ladies due to his excellent manners and because he was a good raconteur. His widely read book of popular astronomy, written in the form of letters to a lady friend, added to his popularity with women. What those ladies never knew was that he really did not have a very high opinion of the fairer sex. …He thought that they are less objective than men and with a nervous system more fragile. The real thread of larger problems would somehow escape them. …in other words, he was a real male chauvinist! (xxxi)

I often recall an event of my youth…. Father and I were vacationing in Austria [where Vasko fractured his collar bone and was treated at the local hospital].
Later that afternoon and throughout dinner, father was very absent-minded which was most unusual for him. [Vasko was put to bed around 10:00 and Milutin left the door open in case Vasko needed him.] Instead of going to bed, he went to his desk, pulled some large sheets of paper from the centre drawer, lit the desk lamp and sat down. Something unusual must have happened, I thought. He never worked after dinner….

Father began writing fast, as I had never seen him before. The effect of my injection had worn off and the splint was cutting painfully into my shoulders and I could not sleep. He got up, put his foot on the chair and his elbow on his knee, took his glasses off and looked at me. He was not seeing me—he looked through me. He put the paper away, took out a new sheet and started writing again.

The woolen strap was hurting me. I called out for him to lift me and put some cotton wool under the strap, but I could see that he did not hear me.
He kept on writing and then he stopped and looked at the paper in front of him. He seemed to be revising all that he had written down, talking to himself…. Then he stopped. He then took out another sheet of paper and started writing again, but slowly this time. The tension on his face gradually dispersed and his usual calm expression returned. Finally he slowed down and then stopped altogether.

He looked up and, recalling my presence, said, “Sorry, I forgot about you. Do you need anything?” He lifted me into a comfortable position on the pillows, put pads of cotton wool behind the strap and said, “I think I’ve got it.” “You got what?” I asked. “The differential equation covering the movement of the Poles. This equation has eluded me for quite some time. I am right now.” He patted me on my sound shoulder, went into his room and, a couple minutes later, I could hear him gently snoring. (xxxiii-xxxiv)


From:
Milankovitch, V. 1982, p. xxiii-xxxiv.
 

Further Reading

  • NASA Earth Observatory. On the Shoulder of Giants: Milutin Milankovitch (1879-1958).
  • Milankovitch, M. 1941. Canon of Insolation and the Ice-Age Problem. Israel Program for Scientific Translations. Jerusalem (1969).
  • Milankovitch, V. 1982. The Memory of My Father. In, Berger, A., Imbrie, J., Hays, J., Kukla, G. and Saltzman, B. Milankovitch and Climate: Understanding the Response to Astronomical Forcing, D. Reidel Publishing Company, Dordrecht, p. xxiii-xxxiv.
  • Milankovi?, V. 1995. Milutin Milankovi? (1879-1958), From his autobiography with comments by his son, Vasko and a preface by André Berger, European Geophysical Society, Katlenburg-Lindau, Germany.
  • NOAA Paleoclimatology Program. Astronomical Theory of Climate Change.
Glossary

Citation

Lee, J. (2012). Milankovitch, Milutin. Retrieved from http://www.camelclimatechange.org/view/article/154611

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