Dark Matter and Cosmic Web Story

by Einasto, Jaan

  Now we had a problem — we had only one horse, and with one horse it is impossible to use our harvester (it had been left exactly at the place before our escape). Thus we had to harvest everything with scythes. Autumn 1944 was nice, almost no rain, so we managed to collect everything before October rains began. We started early in the morning and worked until the first stars appeared in the dark sky. The view of autumn evening stars with Lyra, Cygnus and Pegasus are forever in my memory. By the end of October it was possible to return to Tartu to continue studies in high-school.

  My first task was to visit the Observatory. For several weeks Tartu was a front-city. The German army held the Northern side of the river Emajõgi (Mother River), and the city was under permanent gunfire. The centre of the city was almost completely destroyed, but the main buildings of the University had suffered only little damage. The Observatory was hit and its dome started to burn, but the keeper of the Observatory was able to quench the fire. When he ran down from the dome another shell hit the dome, and through the window splinters wounded the keeper’s leg. Fortunately, his bones were not hit, and he could come down.

  Prof. Rootsmäe told me that small equipment such as chronometers had been stolen by soldiers, but major instruments were undamaged. Also the library, which was hidden in the basement, was more-or-less preserved. Only some books and pictures were befouled. The windows were already mended, and routine work had started. In summer 1945 the Solar eclipse was observed there by Prof. Kipper and his assistants.

  My gymnasium in the old-town had not been damaged. One of the oldest churches just next to our school was burned out. When I arrived at school, routine lessons had already begun. But I noticed changes. Earlier in the city center there were two gymnasiums for boys, the Real Gymnasium and the Treffner Gymnasium (a basically humanitarian one). In both schools at every level there were at least two parallel classes. Now both gymnasiums were united to form the 1st Tartu High-School (now it has the old name — Treffner Gymnasium). Instead of four classes from the two joined schools there were two classes, one level higher there was one class, and two levels higher only one half-full class. So great were the losses of Estonian young men during WW II. Boys in my class were too young to be mobilized into the German Army; the losses were mostly due to the escape of a large fraction of educated families to the West to avoid Soviet occupation. In higher classes additional losses were due to the war — boys were either killed, imprisoned by the Soviets or escaped to the West after the end of the war.

  Fig. 2.3 With my classmates around the Kalevipoeg statue in 1947. Kalevipoeg was considered as the symbol of freedom for Estonia. The statue was destroyed by Soviets in 1950 (author’s photo).

  In my class some boys formed a coterie who started to learn English in their free time (in our class foreign languages were Russian and German). I also joined this group. We organised during vacations excursions to interesting places, celebrations of birthdays and holidays. Among ourselves we used English names, so I was called John. We organised also a physics club and had reports on various topical problems. In 1947 I graduated from the school and started my studies at the University.

  In the University my first mentor was Grigori Kuzmin, a student of Ernst Öpik. He advised me on how to solve a new problem. First the problem must be simplified, so that only the main factors are taken into account. On the basis of this, one can find a preliminary answer. Thereafter other factors influencing the process under study can be taken into account, step by step. This allows one to select all important factors, and eliminate less important ones. He told me how he solved problems when he was a student. When the professor formulated the main problem during the lecture, and started to develop further steps, Grigori did not look at what professor was doing, but tried to solve the problem independently. Usually the professor finished first, as he already knew the answer, but sometimes Grigori was quicker. This habit of solving problems independently was characteristic of Ernst Öpik too. When I met Ernst Öpik during the General Assembly of the International Astronomical Union in 1970 in Brighton, Öpik was just looking for the place where a meeting of interest was to take place. I suggested asking somebody for help. Öpik’s reply was: “it is more interesting to find the location myself”.

  Fig. 2.4 My first mentors Prof. Taavet Rootsmäe (left) and Dr. Grigori Kuzmin (right) (author’s archive).

  There was an active social life in the University. Students interested in sciences joined the Students Science Society (SSS). When I became a student I organised a Students Astronomical Society, which was later transformed to the Estonian Branch of the All-Union Society of Astronomy and Geodesy. I was also rather active in the SSS, and was elected the secretary of the Society. I continued my activity in this Society for several years. But then I understood that this takes too much time, and when starting to write my diploma thesis, I stopped all my activity in the SSS.

  The other activity was among my own course-mates in the mathematics group. We continued close friendships after the University, celebrated family birthdays, and organised walking and bike excursions.

  In Tartu University I was the only student in my group interested in astronomy, so I had to make a choice to join either the physics or the mathematics group. I prepared an individual plan for study, taking as basis the program in the Moscow University at this time, where astronomy was in the mathematics faculty. Most astronomical disciplines I learned from textbooks, such as spherical astronomy, geodesy, stellar statistics and dynamics etc. Also I often visited the Sternberg Astronomical Institute in Moscow, the Institute where Ernst Öpik studied as a student of the Moscow University. There I met Professor Pavel Parenago, the leader of the Soviet School of stellar statistics and dynamics. When discussing possible topics for my diploma thesis he suggested a detailed study of the kinematics of stars of the main sequence. He had just discovered that the main sequence is kinematically inhomogeneous, and wanted to have more detailed information on this effect. This problem was very close to my own interests, as well as to the topic of the research of Prof. Rootsmäe, so I agreed. This resulted in my diploma thesis (Einasto, 1952), as well as my PhD thesis (Einasto, 1955).

  Together with students from the Sternberg Institute in 1951 I visited the Abas-tumani Observatory in Georgia. Here we had lot of time to discuss various topics of interest. The supervisor from the Sternberg Institute was Alla Massewich. Once, during observations, we discussed the stellar evolution problem, which was the main subject of her studies. Alla was a supporter of the old Russell concept of stellar evolution and criticised the work by Öpik as too complicated. Probably the modern stellar evolution concept was generally accepted only after Martin Schwarzschild (1958) confirmed earlier results by Öpik, Gamow and other authors. In his early papers (Hen & Schwarzschild, 1949; Oke & Schwarzschild, 1952) the first reference is to the classic Öpik (1938) paper.

  In 1952 I graduated from Tartu University and started my work in Tartu Observatory as junior scientist. Here I stayed for my whole astronomical life. My first work was to help Grigori Kuzmin in his calculations of a new model of the Galaxy (Kuzmin, 1952a). During this work I found a way for a better extrapolation of the mass distribution to larger distances, to avoid infinite or zero total mass and negative spatial densities. This simple trick was the starting point for my future work on galactic modelling which led finally to the understanding of the dark matter phenomenon, a work which is not finished even today.

  2.2.4 Liia

  There were not many physics and mathematics students after the war, so we had some lectures common to students of various grades, and had common new-year celebrations. Among the students one grade higher from my own was a very nice and charming maiden, Liia Tiit. First I did not catch sight of her. Then, one evening we met in the hall of the University in a classical music concert. The hall has very good acoustics and is used as a concert hall for chamber music. We started to discuss the concert, and I accompanied her home. We discovered many common interests.

  In sum
mer 1950 Liia rented a room in Elva, a small town near Tõravere within a forest. Once I visited her — and stayed there for the whole summer vacation. We had long walks in the pine forest of Elva and bathed in the Elva river. We discovered that we have a lot of common interests and dispositions. We found that we wanted to live together the whole coming life.

  On March 10, 1951 it was the day to register the marriage. It was a usual working day, I was in the Observatory, and had a discussion with Grigori Kuzmin. He talked at length on a topic. I looked at my watch, it was already time to go to meet Liia, but Grigori did not stop talking. Then I said quietly that I have to go to register my marriage, and I am already late. Grigori looked at me with a surprised face, apologised, and let me go. I hurried to Liia’s home, she was already a bit excited and thought that something had happened with me. Together with her parents we walked through the Toome hill to the Office of Marital Status. It was a sunny day, and the first spring water rills trickled down the hill. My parents and brother Mart were already there, together with the son of Liia’s uncle Valdur Tiit. After the official procedure we had a joint lunch in Liia’s parents’ home. Thereafter we came together to our house.

  My parents gave for us two rooms in our family house, and our joint life started. At this time we were both students and lived from our stipend, which was rather low. Thus we lived very modestly. After we both graduated our financial situation improved a bit. However, in order to buy something needed for the household, we had to collect money for at least a full year. In the first year we bought a queen-size bed, in the next year a radio, in the third year bikes for the both of us. On summer weekends we made long bike-trips together.

  Here our first children, daughters Riina and Maret, were born. Our two rooms were incommodious, and we decided to build our own house in the garden of my parents. I spent two years to build the house. However, my financial possibilities were very limited, and the building was slow. Then it was decided that for astronomers apartments will be built in the new observatory in Tõravere. So I decided to make use of this possibility, and sold the half-built house. On May 1961 we moved to our apartment in Tõravere. Here our family has spent the rest of our life.

  In Tõravere our third child was born, son Indrek. A nursery school was organised, first in the apartments of one of the houses, and a few years later a special house for 50 children was built. Conditions for children in Tõravere are very good — after nursery school they can stay in fresh air and play until dusk, on the Observatory grounds and in the nearby forest.

  Liia’s first job was teaching mathematics at Tartu University. In the early 1960’s in the Observatory a computer center was organised, and programmers were needed. We already had three children, and it was not so easy for Liia to go daily to Tartu, so she applied for a job in the computer center. She got the job. In the 1960’s and early 1970’s she participated in our study of the structure and evolution of galaxies.

  We continued in summer time bike-trips, first with Liia, and later together with Maret and Indrek. Also we had a garden in the Observatory. Here we planted apple and pear trees, raspberry, blackcurrant and redcurrant, so we could eat these fruits fresh and make jam for winter. Liia loved gardening very much and spent much time thinking about how to do it all better.

  Our joint hobby was music. Liia played the piano, and we both liked to listen to classical music. In 1955 I bought our first vinyl record player, and started to buy records. Good classical recordings were not available in Estonia, so I used my trips to Moscow to find good records. Soon the manager of one Moscow record shop asked where I was from, as it was clear that I was not Russian. When the manager hear that I am from Estonia, she started to reserve for me good records, which usually disappear from the shelf rapidly. When I was next in Moscow and visited the shop, I was able to buy the best examples of classical music, played by the best musicians. So I have the full set of Mozart’s piano concerts, played by Daniel Barenboim, the full set of Beethoven’s piano sonatas, played by Maria Grinberg, and many other very good records. Maria Grinberg, Svjatoslav Richter and other top Soviet musicians often gave concerts in Tartu University hall, and Liia and I always listened.

  In 1972 I had my first visit to West Germany, and was able to buy a stereo player. Since then I collected only stereo records. In 1985, also in a visit to Germany, I was able to buy my first CD-player. At that time they were very expensive, I think that this player was the first in Estonia, so that even Estonian Radio people once came to me to make a copy of a rare CD (Mozart’s ‘Requiem’).

  In the late 1990’s I started to convert my collection of vinyl records into CDs. This is a time consuming work — all records must be played one at a time to bring the music to the computer, then cleaned from noise, clicks and other defects using special programs. Initially I converted vinyl records into CDs, but then I discovered that it is possible to compress the recordings to the mp3 file format, which takes much less room in the computer. Now I have almost my whole music collection on my iPhone, and can listen to it everywhere.

  After retirement Liia’s health worsened. She had problems with memory, and needed my help in the household. So I cancelled all my planned visits and stayed home. We had a lot of time to be together, and enjoyed this very much. One winter day she fell down so badly that a strong brain hemorrhage occurred. She was hospitalised but lost consciousness. On May 1, 2003 she died. She is buried at Elva cemetery, located in a pine forest. In the same forest we walked and got to know each other. Here I shall be buried when it is my time.

  2.2.5 Tartu Observatory after the war, and the building of the new observatory

  All classical universities have an astronomical observatory. Tartu University was founded in 1632 by the Swedish king Gustav Adolf, but was closed during the Great Northern War between Sweden and Russia. Estonia and Livonia became provinces of the Russian Empire in 1710. In 1802 Tartu University was reopened, and in 1810 the building of the Observatory was finished. Soon it became one of the most advanced university observatories of the Russian Empire. Its director, Friedrich Georg Wilhelm Struve, was an outstanding astronomer, the pioneer of double star studies, one of the first to determine the distance to a star (Vega). But its location near the centre of the city made astronomical observations difficult, and several times during the first half of the 20th century plans were made to build a new observatory outside the city limits.

  In 1946 the Estonian Academy of Sciences was reopened after the war, and many scientific institutes were founded on the basis of departments of Tartu University and Tallinn Technical University. So in 1950 Tartu Observatory was moved to the Academy, to the institute which was soon named the Institute of Physics and Astronomy. The chair of astronomy in Tartu University was joined with the chair of geophysics, and Taavet Rootsmäe continued as before as the head of the chair and professor of astronomy. But most of his former collaborators joined the new Institute, among them also Grigori Kuzmin and Vladimir Riives, an expert on comets. Prof. Harald Keres, an expert on theoretical physics, was appointed as head of the astronomy division.

  The director of the Institute, Prof. Aksel Kipper, initiated plans to build a new observatory outside the town. To discuss the problem he invited Viktor Ambartsumian to Tartu. Ambartsumian was the director of the recently built Byu-rakan Observatory in Armenia, and a leading astrophysicist of the USSR. Soon after this visit two Tartu astronomers, Harald Keres and Grigori Kuzmin, made a trip to the Krim, Abastumani and Byurakan Observatories to see how a modern observatory functions.

  Fig. 2.5 Viktor Ambartsumian visiting Tartu to discuss the building of a new observatory (1948). From left Prof. T. Rootsmäe, Viktor Simm (management director of Institute of Physics and Astronomy), Viktor Ambartsumian, Vladimir Riives, Harald Keres, Aksel Kipper (author’s photo).

  To find the finances, Kipper considered it necessary to secure the support of the astronomical community. For that, a meeting of the Astronomical Council of the USSR Academy of Sciences was held in Tartu in spring
1953 (Fig. 2.6). During the preparations I was in the Sternberg Astronomical Institute in Moscow to collect data for my research. On Moscow’s side one of the organisers was professor Pavel Parenago. We discussed the program of the meeting, in which reports by the astronomers of Tartu and Moscow were assigned about equally. The main speaker on Moscow’s side was Parenago himself, who had just finished a cycle of studies that was very close to Kuzmin’s. On our side the main speakers were professor Aksel Kipper and Grigori Kuzmin.

  The presentations by Tartu astronomers left a deep impression. Kipper spoke about the theory of the radiation of gaseous nebulae that he developed, which enabled him to explain the structure of planetary nebulae with much more accuracy than before. But the focus of interest were the presentations by Parenago and Kuzmin which were dedicated to very similar problems. Parenago was a brilliant lecturer and presented his results with characteristic clarity and simplicity. Kuzmin, on the other hand, was at this time a young researcher. It seemed that for him, competing with the leading astronomers of Moscow was hopeless. Indeed, Kuzmin’s presentation (see Fig. 2.7) lacked the shine that was so characteristic of Parenago. In a quiet voice, he elaborated his model step by step, explaining his innovations and comparing the model to the previous ones, especially Parenago’s. As the presentation progressed, it became apparent that his approach was much wider in reach and more insightful, and that his model was at a completely new level in studying the structure of the Galaxy. Ultimately, everyone had the feeling that astronomy at Tartu Observatory is top class. To the credit of the men of Moscow it should be said that they did not become envious. They acknowledged the high level of the astronomy in Tartu and gave strong support for our plans to develop the new observatory.