The three-starred (the three golden stars of a Hero of Socialist Labor) Yakov Zeldovich.

Source: Courtesy of Olga Zeldovich, Moscow.

2
Yakov Zeldovich
SOVIET PROMETHEUS

Yakov B. Zeldovich (1914–1987) was one of the most intelligent participants of the Soviet nuclear program. He went from secondary school directly to postgraduate studies, skipping university education. Most of his career he spent on weapons and explosives, but never abandoned basic science. During the last two decades of his life, he focused on astrophysics and cosmology. His contributions often followed up discoveries by others. He recognized the need for higher mathematics for scientists and engineers and wrote outstanding books to enhance mathematical literacy.

He was patriotic in strengthening the defense of the Soviet Union, and was recognized by three stars of Hero of Socialist Labor, four Stalin Prizes, and other awards. He was not a “dissident,” avoided taking stands, and appeared expedient, but was devastated when he realized that the leaders of the country might use its weapons for purposes that he condemned. He thrived on his successes, enjoyed life, and died when he seemed still full of energy and plans. Today, there is no public remembrance in Russia of this most decorated giant of the Soviet era.¹

Yakov Borisovich Zeldovich^* loved to give lectures and was a popular speaker, vigorous and businesslike. On one occasion he arrived in a packed lecture hall a few minutes before the start of his presentation, took off his jacket, placed it on a chair, and went to see some people in the building. The audience was left with his jacket with the three Hero of Socialist Labor stars on it. Some daring youths tried on the jacket with the three stars. We cannot know whether he purposely left his jacket there on display before his presentation, but it is known that he prominently displayed his distinctions when he wanted to impress some bureaucrats with whom he had to deal.

The three stars were awarded to Zeldovich, one each in 1949, 1953, and 1956, during a seven-year period marked by three important events in the development of the Soviet Union’s nuclear weapons capabilities: the first atomic bomb, the first hydrogen bomb, and the perfection of the hydrogen bomb with the application of radiation implosion. The latter was Andrei Sakharov’s “third idea,” which may have emerged from a discussion between Zeldovich and Sakharov. Zeldovich’s career was almost a miracle, but it was yet more miraculous that he could embark on it in spite of his family background. His maternal grandparents and his mother’s sister lived in Paris. His father’s sister was arrested in 1936. His brother-in-law was executed in 1937 during the Great Purge, and his sister-in-law lived in America. But he was among the most valuable assets of Arzamas-16, the secret project developing the Soviet nuclear weapons, and the project served as his protection.

Many considered Zeldovich to be the most intelligent of all the scientists of the Soviet nuclear elite. He was exceptionally versatile and changed fields almost as others changed topics in a conversation. He maintained that when entering a new field, it took considerable effort to learn 10 percent of the general information on the new subject; but even that 10 percent made it possible for him to begin independent work in it. Then, it was not difficult to reach a 90 percent understanding of the new subject and that level of knowledge carried pleasure and facilitated creativity. The next 9 percent was almost impossible to learn, according to Zeldovich, who added meekly that not everybody had the ability to master it. The last 1 percent he considered hopeless. His advice was, rather, to switch fields again after the first 90 percent.2

It appears that Zeldovich did not think it was too hard to move from one field to another, but, of course, it takes a good scientist who is capable of independent thinking in the first place to do this. About such changes, he was in accord with the evaluation by another outstanding theoretical physicist Walter Gilbert. The Nobel laureate stated that the only special trait required to make one capable of such changes was the ability to make correct decisions, that is, to distinguish between right and wrong. If one has this ability, the rest, acquiring knowledge of a new field, is not difficult.³ Of course, again, this is true for a Gilbert or a Zeldovich, but not necessarily for the majority of people engaged in scientific research.

Zeldovich was one of the most decorated Soviet scientists, so it is surprising that his only public commemoration, in the form of a bust, is in Minsk, the capital of Belarus, one of the independent successor states of the Soviet Union. The explanation for the Minsk sculpture is that he was born in that city. It was Soviet law that the birthplace of two-time heroes of the Soviet Union or of Socialist Labor was obliged to erect a bust in their honor. Russia today is full of the most diverse forms of commemoration of Soviet-era heroes, not only scientists but military leaders and even communist politicians. Commemoration of many of Zeldovich’s peers can be found in the names of research institutes, streets, and squares, where busts and statues of them abound. But there is none for Zeldovich in Russia proper, with the exception of his tombstone in the Novodevichy Cemetery.

Zeldovich was born in Minsk on March 8, 1914; however, his family moved to St. Petersburg within half a year. St. Petersburg was renamed Petrograd as World War I broke out because the Russian czar did not want the capital of his empire to carry a German-sounding name. The next name change came under the Soviets, when the city was renamed Leningrad. The name was changed back to St. Petersburg in 1991.

Zeldovich came from an intellectual Jewish family. His father, Boris Naumovich Zeldovich, was a lawyer and his mother, Anna Petrovna Zeldovich, was a graduate of the Sorbonne, the famous university in Paris. She was a translator from French and was a member of the Writers’ Union. One of Zeldovich’s daughters, Marina Ovchinnikova, characterized her as “small and energetic, sharp and quick-witted, our restless grandmother.”4 Zeldovich acquired a deep love and knowledge of literature at home and often cited poetry in his scientific articles. Boris Pasternak was his favorite poet; it was therefore appropriate that his attitude toward science in general and discoveries in particular were compared to Pasternak’s, whom Anna Akhmatova described as follows (in Stanley Kunitz’s translation)⁵:

He has been rewarded by a kind of eternal childhood,
With the generosity and brilliance of the stars;
The whole of the earth was his to inherit
And his to share with every human spirit.

Zeldovich started as a prodigy and learned more via self-education than from formal instruction. He was ten years old when he entered secondary school (high school in American terminology), and sixteen when he graduated. He was too young for college. Already at the age of twelve he was considering his future, and he talked with his father about the different branches of knowledge. Mathematics, physics, and chemistry attracted him, but characteristic of his realistic assessment of his abilities, he felt he would not be exceptional in mathematics. He vacillated between physics and chemistry and, finally, did not have to decide between them. But it is interesting that his school experience gave him the impression that physics was a closed subject, with all the fundamental theories in place. His physics teacher presented it as a classical subject, reciting Newton’s laws in both Russian and Latin. In contrast, chemistry did not have a fundamental theory; students learned about concepts such as catalysis and valence, and to Zeldovich, it seemed too empirical. He felt that a bridge was missing between physics and chemistry. He finally discovered the connection in the atomic theory discussed in Ya. I. Frenkel’s book Structure of Matter.

With this background, it is not surprising that Zeldovich found his intellectual home at Nikolai Semenov’s Institute of Chemical Physics. Semenov’s goal was to establish the connection between physics and chemistry, exactly what Zeldovich had found wanting. However, Zeldovich started out as a laboratory assistant at the Institute of Mechanical Processing of Mineral Resources, which was concerned with a plethora of different fields in the geosciences, mineralogy, chemistry, and technology. Zeldovich developed great respect for the great scientists in these areas. Even in his later writings, he singled out A. E. Fersman, whose most important contribution was mapping and discovering various metals, minerals, and other useful materials in the extended territories of the Soviet Union. He found radium and uranium ores, among others, and his research included radiation geochemistry and geo-energetics. Years later, the availability of uranium ores would be among the factors determining the success or failure of the Soviet atomic bomb program. The field impressed Zeldovich, but he did not continue his studies in the geosciences.

Although at the Institute of Mechanical Processing of Mineral Resources, he was only one of the technical personnel, his tasks were far from routine, and he felt that there were possibilities for growth. He was genuinely interested in experimental observations and captivated by visible effects. His broad interest in science was expressed by his participation in excursions to other research institutes. In one such excursion, he visited Semenov’s department of chemical physics (as it was then) of the Leningrad Institute of Physical Technology headed by Abram Ioffe (today, it is the Ioffe Institute). Zeldovich was so much taken by what he saw that he decided to work there in his free time.

Things progressed quickly, and within a couple of months he became an employee of what had already become the Institute of Chemical Physics, with Semenov as its director. When Zeldovich announced his intention to change fields, his previous work place asked the Institute of Chemical Physics for a vacuum pump in exchange for him, and the pump was duly delivered. In Semenov’s Institute, Zeldovich felt as though he was in the midst of scientific progress on a world scale. In 1932, for example, James Chadwick’s telegram informed the attendees of an institute seminar about the discovery of neutrons, and the seminar responded with an enthusiastic telegram. At that time the Soviet scientists were still part of the international community. One of Zeldovich’s senior colleagues, Yulii Khariton, had been Chadwick’s doctoral student in Cambridge, England.

Zeldovich felt that he would need further formal education, He signed up for a correspondence course at the Faculty of Physics and Mathematics of Leningrad University. This allowed him to continue in his job. However, his previous misgivings proved correct; to him, the speed and scope of structured instruction was too confining and inadequate. He ended his studies and never graduated. Instead, he learned from the excellent associates of Semenov’s institute, including Simon Roginskii, Yulii Khariton, Matvei Bronshtein, and Semenov himself. Zeldovich participated in experiments, read about theories to interpret the experiments, and attended the seminars. He learned a lifelong lesson about the usefulness of learning about experiments even though he preferred doing theoretical work.

Skipping university graduation, he pursued a PhD equivalent, the Candidate of Science degree, on the basis of his research on adsorption and catalysis. When he defended his dissertation in September 1936 he was twenty-two years old. His road to becoming a scientist seems more unorthodox today than it was at the time, and it was not unique either. At that time, in Germany, for example, to earn a doctorate in physics, one did not need a formal university diploma; rather, students could go directly for their doctorates. In contrast, doctoral studies in chemistry had to be preceded by a university diploma. Zeldovich used to be asked if he felt uncomfortable because of not having a university diploma, and his response was that he often did, but not after his election to the Science Academy.

Zeldovich continued his steep rise in the scientific hierarchy, and it was fortunate for him that his field was the fast-moving area of explosives and detonations. His next step was to earn the Doctor of Science degree, which bears only a superficial resemblance to the German Habilitation, the requirement for being allowed to deliver courses at university level. The Doctor of Science degree was more a certificate about significant achievements in independent research. Zeldovich chose the theory of nitrogen oxidation as the topic of his dissertation, which he defended at the end of 1939. One of the reviewers of his dissertation was the famous electrochemist Aleksandr Frumkin (today, there is a Frumkin Institute of Electrochemistry in Moscow). Zeldovich was only twenty-five years old. It is noteworthy that his colleagues wanted him to be elected corresponding member of the Soviet Academy of Sciences even before he earned his prerequisite higher doctorate. It did not happen, but it was a sure sign of his recognition as a scientist among his peers.

It is to Zeldovich’s credit that his success in making jumps in his education and career never made him conceited. Even much later in life, his close colleague and equally exceptional physicist, Andrei Sakharov noticed that “it often seemed to him [Zeldovich] that he was a dilettante and was not sufficiently professional in regard to some questions and he made enormous efforts in order to overcome his deficiencies.” Sakharov spoke these words when he delivered a eulogy on December 7, 1987, at a meeting devoted to Zeldovich’s memory.6

Young Yakov Zeldovich.

Source: Courtesy of Olga Zeldovich, Moscow.

In Semenov’s Institute, Zeldovich became a member of Khariton’s laboratory, which excelled both in experiment and in theory. As a theoretician, Zeldovich considered himself to be Lev Landau’s pupil, although they were not connected organizationally. Landau and his group operated in Petr Kapitza’s Institute of Physical Problems (Institut Fizicheskikh Problem [IFP]). But Landau had a nationwide impact on the development of theoretical physics in the Soviet Union. His “teorminimum” exam—a set of comprehensive, tough tests in theoretical physics and mathematics—were famous, and physicists were welcome to take it regardless of their affiliation. Zeldovich did not take the exam, but he was at the level of those who had. Looking back, Zeldovich characterized Landau’s talent as “harmonious, and his judgment harsh, but almost always fair.”7

Even when he was already a much-decorated physicist, around 1960, Zeldovich enjoyed visiting Landau’s theoretical physics course at Moscow State University. At the time, Zeldovich was still at Arzamas-16, but there was a moratorium on nuclear testing, and his schedule was more flexible than usual. Also, he was feeling increasingly that he should be moving away from nuclear physics and Arzamas-16, and back to Moscow and fundamental research.

When in 1962, soon after Landau’s tragic car accident (see chapter 5), Zeldovich visited Landau, he wished him a fast recovery and that he “become the former Landau again.” Landau’s response reflected his old self: “I’m not sure whether or not I will become the former Landau, but at least, surely, I will become Zeldovich.”⁸ Landau meant, of course, that even if he were not able to become his old great self, he was certainly be able to become at least a lesser physicist. It was as witty a response as it was unfair.

In reality, Landau held Zeldovich in high esteem. In 1946, Landau gave Zeldovich a helpful recommendation, contributing to his election to corresponding member of the Soviet Academy of Sciences. Landau did not make such recommendations lightly, and his endorsement carried weight. Zeldovich was thirty-two years old when Landau wrote these words about him:⁹

Ya. B. Zeldovich is without doubt one of the most gifted theoretical physicists of the USSR. The big set of his works in the field of the theoretical investigation of burning is especially worthy of mention. These studies are the best and most important in this field and not only in the USSR but world-wide.

His works are characterized, along the application of the “usual” techniques of theoretical physics by invoking also hydrodynamics. It is very rare among theoretical physicists that someone might be able to exploit both areas, but this is characteristic and a valuable feature of Zeldovich’s activities, enabling him to attack problems that neither the experts of hydrodynamics, nor the “typical” theoretical physicists might do.

It is stressed that Zeldovich’s scientific activities are yet far from their zenith. On the contrary, his works demonstrate continuous scientific development.

Zeldovich had a long engagement with nuclear physics, which started years before the Soviet nuclear weapons program had begun. Right after the discovery of nuclear fission at the end of 1938, he and Khariton started working on this topic on their own initiative and outside their official work hours. They were intrigued by the new direction in physics and its possible applications. It was also a natural continuation of studies at the Institute of Chemical Physics that were related to chain reactions and, in particular, to branched chain reactions (see chapter 8). The process generated by the neutron bombardment of uranium was a branched chain reaction. They dealt with a variety of aspects of nuclear fission, including the question of critical mass. They began publishing papers in 1939, but by the time they had immersed themselves in this area, such works had become classified and could no longer be published.

Scheme of a branched nuclear chain reaction: the large spheres represent uranium-235 nuclei and the small ones, neutrons. The products of the fission of uranium are two smaller nuclei that are not shown in the scheme.

During the first two years of the war, 1941–1943, Zeldovich was involved with a broad range of traditional weapons. First, he perfected the charges for antitank weapons to ensure their penetration of the tank’s armor. When he reported on his innovations to the artillery officers, they suggested that he work on improving the famous powder-charged rockets, known by their popular name Katyushas. Here, Zeldovich and his colleagues, including another outstanding physicist, Ovsei Leipunskii, applied their fundamental physics to making the Katyushas the fearsome weapons of the Red Army.10

The Institute of Chemical Physics was evacuated, moving from Leningrad to Kazan for the most critical period of the war. When it was decided to move it back, it did not return to Leningrad; rather, Moscow became its seat of operation. This facilitated the concentration of nuclear research under the general direction of Igor Kurchatov, who invited Semenov, Khariton, and Zeldovich when he started recruiting participants. The first Soviet uranium-graphite reactor began operating on December 25, 1946, almost exactly four years after the American one on December 2, 1942, in Chicago.

Soon after the Institute of Chemical Physics re-established itself in Moscow, Zeldovich was appointed as head of its theoretical department, and he served in this position between 1946 and 1948. In this period, he was also a professor at the Moscow Engineering Physics Institute. In 1948, there were big changes in Zeldovich’s life. During the preceding years, he had continued publishing papers on nonclassified research, and his publishing activity got him into trouble at this time, although it might be argued that this was merely an excuse to construct accusations against him. It was part of the anti-Semitic campaign, which was not officially spelled out as being against Jews; rather, it was against “cosmopolites.” Zeldovich and Leipunskii were accused of disclosing state secrets in their publications. Even their non-Jewish superior at the institute was accused of overlooking those secrets and issuing the permission to publish. Although Zeldovich by then worked mostly in the secret nuclear laboratory, he was fired from the Institute of Chemical Physics, and moved full time to Arzamas-16. Leipunskii who was a lesser name in the atomic bomb project, was ordered by the director of the institute to move to the far-away Semipalatinsk Proving Ground in Eastern Kazakhstan, which became a good hiding place for him.

Both Zeldovich and Leipunskii became members of projects under the top government figure Lavrentii Beria, whose direct supervision served to protect them. Beria’s priority was the success of the atomic bomb project; he was not interested in concocted accusations against its scientists. However, even Beria could not have stopped the anti-Semitic measures in which some of his subordinates in the secret police participated with zest. The initiator of the campaign had been Stalin himself.

Zeldovich became the principal theoretical physicist of the Soviet atomic bomb project at Arzamas-16. He also gave a presentation about the possibilities of nuclear fusion reactions on December 17, 1945, at a meeting about the development of the hydrogen bomb. His coauthors were I. I. Gurevich, I. Ya. Pomeranchuk, and Khariton. At the time, the Soviet leadership had not yet reached a decision to go forward with this development. They wanted to focus on the creation of their atomic bomb, which was subsequently successfully tested at the end of August 1949. The Soviet decision to develop the hydrogen bomb was made on February 26, 1950, a mere four weeks following President Truman’s announcement on January 31, 1950, about the continuation of research in the United States on all atomic weapons, including the hydrogen bomb.

The initial Soviet model was similar to the American “Super,” as the Americans often called the hydrogen bomb in the initial stage of their work. In this design, an atomic bomb at one end of the device would start the thermonuclear reaction. Extensive calculations were performed for this model—just as in the American program. The work was conducted under the leadership of Zeldovich, and a large group of physicists and mathematicians assisted him. Like the Americans, the Soviet scientists eventually found that this initial model lacked feasibility.

For the hydrogen bomb program, another theoretical group joined Arzamas-16. It was from the Physical Institute of the Academy of Sciences (Fizicheskii Institut Akademii Nauk, [FIAN]); it was led by Igor Tamm and included Andrei Sakharov. They contributed fruitfully to the development of the Soviet hydrogen bomb (discussed in chapter 3).

Zeldovich was involved both in the development of the first the atomic bomb, and, subsequently, the hydrogen bomb. The principal task was creating ever-more-powerful nuclear charges and making them lighter, smaller, more easily deliverable, and economical. The need to economize was always an important consideration with the especially precious tritium.

Zeldovich remained at Arzamas-16 until October 1965. He dreamed about returning to pure science. Even during the years of the most intense weapons work, he continued fundamental research, traveled to Moscow from Arzamas-16 to visit research institutes, attended seminars, and gave presentations there. He kept up with world literature in his fields, and when he was finally freed from Arzamas-16, he was able to immediately rejoin world-level science. He started asking for release from classified work at the end of the 1950s, and finally, Khariton helped him by reassuring the Soviet leadership that Zeldovich had done what was expected of him. By then, Zeldovich was a full member of the Science Academy.

However, Zeldovich’s road to the full membership had not been smooth. In 1953 most leading physicists who had participated in the creation of nuclear weaponry were elected full members. Zeldovich was an exception, and no explanation has been found for this slight. It embarrassed his colleagues, especially Sakharov, who was elected on this occasion to full membership, skipping the corresponding member stage.

The next time, in 1958, the directives of the Communist Party categorically opposed Zeldovich’s election, but the Academy membership did not follow them. There was a tremendous difference between 1953 and 1958. In 1958, he was elected unanimously by the Division of Physical-Mathematical Sciences. It was not only the nonparty members Landau, Tamm, Leontevich, and Artsimovich but also the party member Kurchatov who supported Zeldovich and called him a genius.¹¹ The party representatives criticized Kurchatov for not following the party line, not even trying to mask the fact that they possessed information from the secret police about the scientists, especially those who participated in the nuclear programs. Such information was collected by wiretapping and by informers, and it left no doubt about the negative views of these outstanding scientists concerning the Soviet leadership. Nonetheless, this could not be the sole reason for what happened to Zeldovich; he was always rather careful, certainly more so than, for example, Landau, who was elected full member of the Academy in 1946, skipping corresponding membership.

When in 1958 Zeldovich was elected full member of the Academy, he was still only forty-four years old. Given his versatility, an intriguing question was whether he himself singled out any one among his achievements. The question came up when some of his colleagues considered nominating him for the Nobel Prize. According to Alfred Nobel’s will, one discovery or invention had to be singled out, rather than lifetime achievement. The nominators and Zeldovich agreed that the achievement to be singled out should be his work on self-organizing systems in active media, that is, on phenomena including flames, ignition, and detonation. Zeldovich considered most of his other work to be of more transient significance. The nominators thought that understanding the phenomena mentioned had been interesting to people from prehistoric times, and in this respect they likened Zeldovich to Prometheus. The nomination had been complied and submitted, alas, Zeldovich was not selected for the award.

Zeldovich always enjoyed strong support from his family. His first wife, Varvara Pavlovna Konstantinova was a scientist in her own right and worked at the Institute of Crystallography of the Academy. They met in 1932 when he was eighteen, and she twenty-five. They had two daughters, Olga and Marina, and one son, Boris. Their life together lasted thirty-nine years, from 1937 till her death. Their family backgrounds were strikingly different. He came from a well-organized family and she came from a cheerful, seemingly disorganized one with many children and relatives. Zeldovich became especially friendly with one of Varvara’s brothers, Boris Konstantinov, a future academician and vice president of the Academy; but this was yet far in the future. In 1937, another of her brothers, also a scientist, fell victim to Stalin’s terror. This is why, at the time, the marriage was considered by a family member “an act of courage” on Zeldovich’s part.12

Varvara Pavlovna formed “a cult” for Zeldovich at home; she guarded his working conditions, and the “magic words, ‘Papa is working’ stopped any fussing or noise.”¹³ No wonder the children “were rather afraid and shy” of their father.¹⁴ Daughter Marina noted that he did not have time for his children, whereas he was very relaxed with his colleagues. It was always their mother who went to the parents’ meetings at school, which was just as well, because the daughters shivered at the thought that he might go and let the teachers see his “complete orthogonality” to what they did in school.¹⁵ All in all, though, Zeldovich’s children remember a “happy childhood.”¹⁶ In later years, son Boris and Zeldovich were often seen together immersed in discussions of physics.¹⁷ Boris was a student of the Faculty of Physics of Moscow State University, as his sisters had been, and became a successful scientist and a corresponding member of the Academy. After the collapse of the Soviet Union, he moved to Florida and became a professor at University of Central Florida.

Zeldovich’s letters to the family from Arzamas-16 showed “happiness, warmth, and certainty in his love” for them.18 But the long separation, even if broken by frequent visits to Moscow, took its toll on Zeldovich’s private life. He had his youngest daughter, Annushka, from a relationship in Sarov. Annushka’s mother, O. K. Shiryaeva, an architect, was a political prisoner. She was sent to the infamous Kolyma in Eastern Siberia, where their daughter was born in 1951. Zeldovich supported Shiryaeva and eventually achieved her and her daughter’s liberation.¹⁹ Zeldovich had a total of six children, all of whom he recognized as his children. All of them were trained as physicists.²⁰

After the death of Zeldovich’s first wife, he married Anzhelika Yakovlevna Vasileva. She guarded her husband’s working conditions by keeping away everybody whom she considered a disturbance to him. She did not live long, and Zeldovich married for the third time; his third wife was Inna Yurevna Chernyakhovskaya.

Throughout his life, Zeldovich was never a director of a big institute; never had a pretentious office with an army of secretaries protecting their boss; he thrived on constant interactions with his colleagues. In the period 1941–1943 numerous institutes of science and education were evacuated to Kazan, and most evacuees from the Moscow and Leningrad academic institutions occupied a modest three-storey building. There were great names among them, such as Kapitza, Sergei Vavilov, Landau, Tamm, Grigory Landsberg, Semenov, Frumkin, and many others, including Zeldovich.

He always had close interactions with other outstanding physicists, especially Khariton and Sakharov. They were friends who respected each other and were united not only in their interest in physics but also in belonging to the elite of Soviet society. The friendship of Khariton and Zeldovich had its roots in their youth. When the two appeared together at a festive celebration, as, for example, the 1982 fiftieth anniversary of the Institute of Chemical Physics, each wearing his three stars of Hero of Socialist Labor, it was quite a scene.

Zeldovich was a sportsman, yet his physical attributes were not very impressive. From a distance he did not strike anybody as extraordinary. He was short, stocky, and round-faced; he wore round glasses, was not handsome, and did not appear distinguished even when wearing his three-starred jacket. However, as soon as people interacted with him, their impression of him changed. He captivated his partners in conversation. I met him only once; it was in April 1987, at a conference at the Institute of Crystallography in Moscow. During a break I was having a conversation with the director of the institute, Boris Vainshtein. Zeldovich appeared unannounced; he needed to discuss something with Vainshtein. It was obvious that Vainshtein was impressed that Zeldovich had approached him. Both were full members of the Academy, and Vainshtein was also an institute director, but Zeldovich was Zeldovich. I do not remember a word of our conversation, but I remember the man as if I had met him yesterday. I find it difficult to express in words what was so memorable about him; the encounter made a lasting impression on me.

He was an enthusiastic lecturer who had a natural ability to convey his passion for science and captivate his audience. “Zeldovich appeared in the auditorium in simple clothing, a plaid shirt with unbuttoned collar. Without any board, he began to speak very simply and intelligibly. His emotions caught up the audience, and the contact with the listeners was complete. Before us was a man all caught up, lively, like a little bouncing ball.”21 He has been described as vivid, charming, with a good sense of humor and shining eyes, often with some mischievousness in them. He was a devoted friend and a caring colleague but could appear intolerant because of his inability to compromise, and sometimes this led to the cooling off of his friendships.²²

Considering the plethora of his scientific achievements and the large number of different areas of physics in which he was involved, some foreign scientists supposed that “Zeldovich” was a collective label for a whole group of researchers, just as the name N. Bourbaki was. This perception was facilitated by the fact that for a long time Zeldovich could not travel and did not appear at meetings. For Zeldovich, foreign travel gained mystical power, perhaps because it proved unattainable until the last years of his life. In this he was not alone in the Soviet Union and Eastern Europe. And he was not alone among Soviet big-name scientists, who meticulously marked on a world map all the locations from where they had received invitations, but were never allowed to visit.²³

There have been conflicting observations about the extent of Zeldovich’s unwillingness to enter into conflict with the authorities. But the notion is quite generally held that he avoided politics, even in his conversations. He preferred following instructions to disobeying them. For example, it was forbidden to carry letters away from Arzamas-16. The purpose of this rule was to keep everything under the control of censorship; whereas the purpose of breaking it was to speed up interactions with friends and family. Zeldovich observed the rule, and many interpreted this as unfriendly cowardice. But to break it would have indeed represented a risk for him, especially since he traveled to Moscow more often than most, and his carefulness was probably justified. It was known that the secret police tried to trap scientists preparing for such travel, by asking them to take a letter or a package with them, only to “unmask” them as violating the rules of the installation.

Zeldovich also preferred to let his articles be censored at the manuscript stage rather than fight for leaving them intact. It was characteristic of his general demeanor when he reasoned that “it’s not worth getting involved in!”²⁴ In 1962, there was a conference in Tartu about modern physics and astronomy, for which Zeldovich prepared with great enthusiasm. During the meeting, there was a campaign to collect signatures protesting atmospheric nuclear testing by the Soviet Union. Zeldovich disappeared before he could be asked for his signature. He later told a colleague that he could not reconcile signing such a protest while working on the very tests the signatories were protesting against.25

Just as he avoided political discussions, he taught his son how to evade topics that made him uncomfortable. Zeldovich’s advice was to always have a few simple jokes or anecdotes to tell that would divert attention from the undesired topics. But in debates on scientific issues he was not at all conformist; he was one of the few who could stand up to Landau. When in 1952 Semenov was being attacked for ostensibly falling for idealism in his work, Zeldovich came to the meeting and made a strong statement in Semenov’s defense. On his jacket, he conspicuously displayed his star of Hero of Socialist Labor (he had only one at the time). The audience was duly impressed by his distinction, which at that time was quite rare. The fact that Zeldovich’s award had not been announced in the media, although such things as a rule were, only enhanced the impact, because the secrecy implied that he had received it for something extraordinary. In fact, the awardees of classified programs were discouraged from wearing their stars in public lest it invite curiosity about their activities.

He liked wearing his stars, especially when they were supposed to help a cause, as when he came to Semenov’s defence, or, for example, when he appeared at the trial of the father of one of his colleagues. He hoped to impress the judge, not so much to gain favor, but to steer the procedure in the direction of fairness. This happened in 1957, and the “crime” was criticism directed at N. S. Khrushchev. Another occasion on which he displayed his stars—by then, he had three—was when Zeldovich (supposedly) went to visit Mosfilm, the Soviet Hollywood, and wanted to impress the actresses. Alas, he was barred from entering because the guards were sure that having three stars could not be for real.²⁶

Zeldovich, as most of the other Soviet physicists, considered it his patriotic duty to participate in creating nuclear weapons for the Soviet Union. They did not question whether or not the development of these horrific weapons was justified. However, when the first Soviet nuclear explosion was executed at the end of August 1949, among the physicists observing the test, Zeldovich and also Kurchatov stayed quiet. Others expressed their joy; some shouted “long live Comrade Stalin!”²⁷ Zeldovich felt grave responsibility for his seminal contribution to the creation of Soviet nuclear weaponry, which most probably strengthened Stalin’s recklessness in international affairs. In 1950, soon after the first Soviet atomic bomb was exploded, North Korea invaded South Korea. Zeldovich was tormented by the thought that the Korean War might have not happened had the scientists not placed atomic bombs in Stalin’s hands.²⁸

Marina Ovchinnikova supposed that his feelings of responsibility hastened his departure from Arzamas-16. She makes a strong case for Zeldovich’s psychological troubles when she described his visit to a psychiatrist, ostensibly suffering because bodyguards—euphemistically labeled “secretaries”—were shadowing him. The psychiatrist must have had a hard time making a politically correct diagnosis.29 On the other hand, Zeldovich was known to play tricks on his bodyguards. For example, he swam far into the Irtysh River, in the vicinity of the Semipalatinsk proving ground, knowing that his frightened bodyguard could not swim (a surprising deficiency for a bodyguard).

It was an expression of courage that Zeldovich never wavered in unambiguously identifying himself with Jewish causes. The overt anti-Semitism in the Soviet Union during the last years of Stalin’s reign began in 1947–1948. The famous actor of the Moscow Jewish Theater and well-known leader of the Jewish Anti-Fascist Committee, Solomon Mikhoels, was assassinated in January 1948—his death was attributed to a road accident.³⁰ It was the deed of Stalin and the secret police, but nobody could openly accuse them of the crime. When Zeldovich learned about the tragic event, he and a friend, as a token of solidarity, went to the Jewish Theater to attend the farewell for Mikhoels.

Zeldovich’s departure from the secret project did not reduce his feelings of responsibility for his participation in the creation of the atomic bomb and later the hydrogen bomb. In October 1973, at the time of the Yom Kippur War between Israel and its Arab neighbors, he heard gossip at the Ministry of Medium Machine Building (the authority for nuclear projects) about the possible deployment of a Soviet atomic bomb against Israel. Zeldovich decided that he would commit suicide if this were to happen. He composed a letter to leave behind, but knew that the letter would disappear if it fell into the hands of the authorities. He wanted to be sure that the reason for his suicide became known, and so he left a copy of his suicide note with his good friend, the physicist academician Ilya Lifshits. As is known, no atomic bomb was used against Israel in the Yom Kippur War, and after the war ended, Zeldovich collected the copy of his suicide note.³¹

Zeldovich’s demeanor may have also changed with time. Back in the early 1950s, there was a controversial story, which has become known as the Agrest Affair. It has been interpreted as an example of negative behavior on the part of Zeldovich, when in reality it was the regime and the atmosphere in which the scientists all existed that was reprehensible. Mattes Agrest was the head of the mathematics section in the theoretical division at Arzamas-16. He was a religious Jew with a large family. When the anti-Semitic upheaval reached the atomic project, he became a thorn in the eyes of the security organs. Just being a Jew did not suffice as a reason for dismissal because at that time it meant that the leading echelons would have been to a large extent emptied. As Agrest’s past was scrutinized, it came out that he had studied Judaism and had graduated as a rabbi. He may also have had relatives in Israel, and this finally served as official pretext for his dismissal. On January 13, 1951, he was told that he had twenty-four hours to leave the installation.

Having relatives in Israel at that time seemed a valid reason for dismissal even to Agrest’s most sympathetic colleagues. However, they found the twenty-four-hour time limit cruel. Tamm and others protested, and the time limit was extended to one week. On the day of the Agrests’ departure, Tamm left work early, announcing that he was off to help the Agrests to pack their belongings. Sakharov—he was far yet from becoming a “dissident”—made two gestures. He shook Agrest’s hand, which was a demonstration of solidarity, and he offered Agrest and his family to stay in his unoccupied Moscow apartment.32 Two of Agrest’s Jewish colleagues, however, appeared indifferent to his plight: his immediate superior, Zeldovich, and the scientific director of Arzamas-16, Khariton. Zeldovich’s and Khariton’s reactions to Agrest’s plight was in sad contrast with the solidarity expressed overtly by Tamm and Sakharov. It may be argued, though, that it was easier for the non-Jewish Tamm and Sakharov to express solidarity with Agrest than for the Jewish Khariton and Zeldovich. Agrest subsequently found employment doing other classified work.

Zeldovich had nothing to do with Agrest’s dismissal, but Sakharov “heard that Zeldovich (although Zeldovich denied this) had upset Agrest greatly by making him work on the Sabbath.”³³ Apparently, Agrest tried to reconcile observing the Sabbath with his work schedule at Arzamas-16 in such a way that though he came to work on Saturdays, he restricted his activities to discussions; he would not write anything. In 1981, that is, three decades after the events, Zeldovich wrote a letter to Agrest concerning their encounter on a Saturday.³⁴ Zeldovich was nonreligious and for him Saturday was like any other day; he never paid attention to whether any day was a holiday or a workday. On that particular occasion, the two were having a prolonged discussion during which—resisting Zeldovich’s prodding—Agrest could not bring himself to write anything on the board with a piece of chalk.

The episode kept tormenting Zeldovich. Eventually, Agrest expressed regret that he did not inform Zeldovich that he did not write on the Sabbath.³⁵ We can sympathize with Agrest for his plight, but the humiliation Khariton and Zeldovich must have felt also elicits sympathy. They felt unable to stand up for a Jew, because they themselves were Jews. Both Khariton and Zeldovich understood the prevailing anti-Semitic sentiments and actions during the last years of Stalin’s reign. Many years later, Zeldovich told the mathematician A. D. Myshkis “about a group of young people who were trying to revive Jewish customs, right down to their clothing, keeping the Sabbath, and so forth. [Myshkis] expressed doubts about the reasonableness of this, but [Zeldovich] talked with certainty about people’s right to behave this way.”³⁶

Yakov Zeldovich and Valentine Telegdi in 1960, during the High Energy Physics Conference in Kiev.

Source: Courtesy of Olga Zeldovich, Moscow.

In the mid-1970s, the already three-starred academician Zeldovich suffered anti-Semitic attacks in the guise of criticism of his immensely popular mathematics book, Higher Mathematics for Beginners.37 The book had appeared in several editions, both at home and internationally, and had grown out of Zeldovich’s unhappiness about how mathematics was being taught. He found it unsatisfactory that the subject came too late in the curriculum after other subjects that needed mathematics were already being taught. He likened the situation to serving lunch, but making the salt and pepper for it available only at the time of the afternoon tea.³⁸ In the book, Zeldovich did not follow all the rigorous approaches of pure mathematicians, but it was a highly didactic volume that brought life to a subject that many outside the field dreaded. Encouraged by the book’s success, Zeldovich cooperated with Myshkis in producing two further volumes, Elements of Applied Mathematics and Elements of Mathematical Physics.

Zeldovich had an excellent testing ground for pedagogy in his own family, where virtually everybody was a physicist, and they held family seminars. When his daughters went to school, he hired S. S. Gershtein, a future academician, to tutor them. The girls were excellent students who could still learn from Gershtein, but it was not lost on the young physicist that this engagement came in handy for him during a difficult period of unemployment.

Zeldovich has been characterized on occasion as accommodating toward the communist regime. However, he never joined the Communist Party, and he never signed any letter condemning Sakharov for his “dissident” activities. When Sakharov was in exile, it was forbidden to make references to his work—it was common practice under the Soviets to make any undesirable person into a nonperson. When Steven Weinberg’s book The First Three Minutes was to appear in Russian translation, Zeldovich was asked to prepare a supplement. In it, he made a reference to Sakharov, which the censors wanted to remove. Zeldovich’s response was that if the reference went, his supplement would go with it. On another occasion, the censor threw out a reference in the manuscript of a popular article prepared for the large-circulation magazine Priroda (Nature) on the grounds that the editors should not show Sakharov in a positive light in a paper read by so many people. A compromise was reached: instead of being included in the more conspicuous list of references, it was mentioned in a footnote, making it less likely that the readers would notice it; but the reference to Sakharov stayed in the piece.

Nonetheless, as Sakharov noted, “hurt feelings and mutual coldness crept in” between the former close colleagues, Zeldovich and Sakharov, especially in the period of Sakharov’s exile to Gorky.39 Sakharov perceived that Zeldovich “strongly disapproved” of Sakharov’s social activism and was puzzled why Zeldovich did not support him. Their close relationship was never re-established during the short period of time after Sakharov’s return from exile and before Zeldovich’s death.

Yakov Zeldovich is a shining example of the level of physicists who participated in the Soviet nuclear program. It was characteristic of him that during his period at Arzamas-16, he stayed versed in the progress of basic science. Not only did he keep up with the literature, but he also contributed to it. Had it not been known that his principal engagement between 1947 and the early 1960s was the nuclear weapons program, it would have been difficult to discern that he was absent from ordinary academia for such a long time. As one of his colleagues remarked, Zeldovich’s “lifespan encompassed several scientific biographies.”⁴⁰ It was not only that Zeldovich benefited from staying abreast of the happenings in modern physics; he helped others to do the same. He transmitted knowledge and information in a creative way. This is why Sakharov noted that “in the area of fundamental physics, much of my research arose from my contacts with him, under the influence of his work and ideas.”⁴¹ Both Sakharov and Zeldovich were exceptional physicists, but Sakharov’s name has gained additional eminence because of his human rights activism, which has been recognized by a Nobel Peace Prize. There are some who believe that Sakharov’s glory may have pushed Zeldovich back into the shadows.⁴²

Zeldovich was fifty years old when he finally returned to pure science in full force, becoming an associate of the Institute of Applied Mathematics of the Soviet Academy of Sciences. Mystislav Keldysh was the director of the institute, who in 1961 had followed Aleksandr Nesmeyanov as the president of the Science Academy. As a mathematician Keldysh was involved in the nuclear weapons program as well as in the space program. He greatly supported Zeldovich, who created a division of astrophysics in the institute, and took up cosmology, which had always been among his interests.43 By doing so, he reached back to a Russian scientist in the early twentieth century, Alexandr Friedman, who around 1920 had created a theory of the expanding universe that contradicted Einstein’s views of cosmology. Einstein originally rejected Friedman’s theory but later accepted it. Friedman died prematurely in 1925, without realizing that his two brief papers would considerably impact the development of modern cosmology.

Zeldovich’s associates contributed significantly to the question about the origin of the universe and were quoted in the Nobel lectures about the discovery of remnant heat in outer space. The existence of this remnant heat served as unambiguous evidence of the correctness of Gamow and his associates’ Big Bang model. Nuclear physics and astrophysics are not so far from each other as they seem at first glance. Many of the processes theoretical physicists investigated on paper and later by computer had been going on in space from the start of the existence of the universe. The joint application of astrophysics and nuclear physics made it possible to understand how the universe began and how the chemical elements had formed.

A closer look at this topic may be instructive to learn a little about Zeldovich’s approach to fundamental problems in science. Regarding the beginning of the universe, Zeldovich was fond of the model that supposed a cold start and subsequent development. This was one alternative. Another was the scheme originated by Gamow and his associates, which has become known as the Big Bang model, a name originally coined to ridicule it. The Big Bang model started with an initial explosion producing enormously high temperatures. Zeldovich correctly understood that gaining evidence about the presence or absence of a relic (background) radiation in outer space would be decisive in demonstrating the correctness of the cold model or the hot model. He formed a small research group consisting of three people: himself, A. G. Doroshkevich, and I. D. Novikov. Once the question about the relic radiation had been resolved, their pioneering approach received recognition in Arno Penzias’s Nobel lecture. Referring to the contribution of the Soviet scientists, Penzias said that it was “the first published recognition of the relict radiation as a detectable microwave phenomenon.”⁴⁴

Penzias and Robert Wilson discovered this relic radiation by serendipity and and only their subsequent literature search uncovered Doroshkevich and Novikov’s relevant paper.⁴⁵ In contrast, Doroshkevich and Novikov were so thoroughly familiar with the literature that not only did they point to the possibility of detecting relic radiation—if it existed in the first place—but suggested using a specific instrument used at Bell Laboratories for this purpose. Unfortunately though, Doroshkevich and Novikov misinterpreted the then-available measurements published by the associates of Bell Labs, and in 1964 they deduced that there was no relic radiation.⁴⁶ The conclusion from this misinterpretation was the easier than the Big Bang model to accept because it was consistent with Zeldovich’s cold universe model.

Yakov Zeldovich and Pope John Paul II in 1980 at the Vatican.

Source: Courtesy of Olga Zeldovich, Moscow.

Yakov Zeldovich with one of his most famous associates, the academician astrophysicist R.A.Sunyaev, in the 1980s.

Source: Courtesy of Olga Zeldovich, Moscow.

It came as a great disappointment to Zeldovich when he learned about Penzias and Wilson’s observation of the remnant heat, as it signified the failure of the cold model. But it was a manifestation of Zeldovich’s devotion to scientific truth that he immediately acknowledged not only the importance of Penzias and Wilson’s observations, but also the validity of Gamow and his colleagues’ model. Incidentally, this recognition also required political courage, because ever since Gamow had defected from the Soviet Union in the early 1930s, he had become a nonperson there.

In a rare glimpse into his weapons work, Zeldovich revealed to one of his associates that his not very well-founded choice of the cold model was a reflection of the working habits in the nuclear project. There, they were often forced to make instant decisions and make a choice among possible solutions when further deliberations might have been called for.47 The discovery of the existence of relic radiation reached Zeldovich toward the end of 1965. He regrouped at once, and started giving enthusiastic lectures about the relic radiation and the hot universe—the topic seemed to fit his temperament eminently, and wherever he went, packed auditoriums greeted his presentations.

In spite of his generally cheerful demeanor, Zeldovich also experienced dark moments. For example, not long before he died, he recounted to a Western visitor, K. S. Thorne of the California Institute of Technology, the discoveries he could have made but did not—and others made them, in the West. The visitor was surprised because Zeldovich made a great many important contributions to physics and astrophysics. In fact, his work led other scientists in both the Soviet Union and the West to make significant contributions to the field.⁴⁸ P. J. E. Peebles of Princeton University, one of the major players in cosmology, noted: “Through all my career in cosmology, I could be sure that if Zeldovich was not hard on my heels it was because he was racing far ahead.”⁴⁹ However, Zeldovich’s dark moments came not only toward the end of his life. In 1967, when conversing with Sakharov about the works each liked best in their own oeuvre, Zeldovich noted, “My works too often sink without a trace.”⁵⁰

Zeldovich and Sakharov were two great physicists in the Soviet nuclear program and beyond. They lived and worked for years side by side at Arzamas-16, and they had excellent interactions. Many of their results in the project must have come out of their discussions, but no priority controversy ever surfaced about their collaboration. According to Yurii Smirnov, a close observer, Zeldovich’s talent as a physicist matched Sakharov’s, but, as noted above, Sakharov has outshined Zeldovich due to his human rights activities.⁵¹ Smirnov emphasized Zeldovich’s enormous contributions to atomic defense, physical foundations for the internal ballistics of solid-fuel rockets, scientific schools in chemical physics, hydrodynamics, the theory of combustion, nuclear physics, the physics of elementary particles, and astrophysics.

Smirnov noted that Zeldovich and Sakharov complemented each other. When Zeldovich entered a new field, he preferred to define and solve a problem and move toward generalization. He found it useful to review the new field he was entering, and from this, instructive review articles were born. Sakharov in a similar situation, when entering a new field, appeared to perceive the physical laws and the connections between various phenomena, and he could move directly toward technical innovation.52 Their ways of reasoning were very different. Sakharov was more abstract and formal; Zeldovich preferred analyzing concrete problems.⁵³

Both Sakharov and Zeldovich were characterized by “their democratic attitude, devoid of any hint of grandeur or overbearing, and their openness and accessibility; they destroyed the traditional picture of academicians as objects of universal reverence and worship.”⁵⁴ The two were very different in character and temperament, and their working habits were also very different. Zeldovich got up very early in the morning, exercised vigorously, and worked till the evening, taking only a few short breaks. He had his rest in the evening. When Sakharov worked on a problem, it grabbed him and stayed with him without a moment of interruption.

Zeldovich was sometimes compared with Enrico Fermi for his versatility and because his science was his life. In the first period of his career, Sakharov also showed complete devotion to solving the problems of physics for defense. Eventually, however, physics gradually moved to the background, yielding to his political activities. Ultimately, curing the illnesses of society became Sakharov’s principal concern, as though he felt that the physics could be accomplished by others but that his human rights and other political activities were truly unique. In this respect, Leo Szilard comes to mind. Fermi and Szilard together faced the danger that totalitarian states might acquire the most deadly weapons. Fermi contributed enormously to the physics of the American projects; for him, science was his life. For Szilard, science was a means to solve life’s most pressing problems of human society—the survival of democracies.⁵⁵ In this sense, Sakharov was closer to Szilard than to Fermi, and Zeldovich closer to Fermi than to Szilard.

Generosity was characteristic of Zeldovich. He was generous with Sakharov, for example, in sharing all he knew about the latest achievements of modern physics. Another example of his generosity was that he welcomed Tamm and his colleagues at the weapons installation rather than being upset about the arrival of another theory group, which he might have considered a threat or at least a rival. Yet another example of his generosity was discovered by Boris Gorobets among the archival materials of the late Evgenii Lifshits, shortly after Zeldovich’s unexpected death of heart failure. Gorobets found an unpublished evaluation of Lifshits’s works in cosmology written by Zeldovich. Gorobets (the son of Lifshits’s second wife) was so moved that he wrote a poem honoring Zeldovich’s memory.⁵⁶ It is quoted here in the free-style translation of chemistry Nobel laureate and poet Roald Hoffmann57:

In memory of Ya. B. Zeldovich

One hears a string orchestra.
The earth sad
and the pillared hall too.
A genius leaves, as a wave,
into a tunnel bereft of light or shade,
into a world without phonons.
While in science superstrings
are young and ripple,
canons crack.
The cosmic foam
boils up. Chopin’s March…
And the icon, his face.