The World of Andrei Sakharov.

A Russian Physicist's Path to Freedom

by Gennady Gorelik with Antonina W. Bouis     

(Oxford University Press,  2005)

Contents in Detail

 

 

 

Chapter 14. From Military Physics to Peaceful Cosmology

 

Inventor or Theorist?

The Physics of the Universe

From the Atomic problem to the problems of the Universe

Symmetries in the asymmetrical Universe

Matter and Antimatter in the Universe

Sakharov's Three Conditions for the Universe

The Elasticity of Vacuum

Theorist-Inventor

 

 

 

Inventor or Theorist?

 

In explaining why he did not leave the Installation immediately in 1962 (because of the disputed double test), Sakharov named his work on banning testing as the most important reason, but not the only one.  Another reason was that he had nowhere to go. Not in the sense that there wouldn’t be a place found for him somewhere in one of the institutes of the Academy of Sciences. But what would he do there? Theoretical physics?

It was a difficult issue for him, with his honesty,  sense of personal dignity, and his manner of behaving “outwardly modestly, but in fact quite the opposite.”

After Sakharov’s election to the Academy of Sciences in 1953, Landau was asked his opinion of the young theorist. Landau asked, “Whom do you mean?” When he was told it was Sakharov, he replied, “But he’s no theorist! He’s an inventor physicist.” [1]

Landau knew him as an inventor. And Sakharov was working then, and continued for another decade, as an inventor. True, he had started out as a theorist. But there are many Russian businessmen and politicians of today who had written dissertations in physics or mathematics.

Sakharov remembered how he had come to Moscow after a few years at the Installation, and ran into Ginzburg. He told him about some purely scientific idea. “He snickered and said, ‘So, you expect to do physics as well as your little bomb?!’” In hindsight, Sakharov agreed that combining such things “turned out to be very difficult, basically impossible.”

He also remembered his father’s sorrow, a few weeks before his death in late 1961. “When you were studying at the university, you once said that discovering the mysteries of nature was what could make you happy. We do not choose our destiny. But I am sad that your destiny turned out to be different. I think that you could have been happier.”  The development of nuclear weapons is not simply far from discovering the mysteries of nature, it is contraindicated.

Sakharov watched the mathematical talent of Dmitriev fade away. Zeldovich had said that Dmitriev was “perhaps the only one among us with that spark from God. You could think that Kolya is just this quiet, modest boy. But in fact, we all tremble before him, as if he were the highest judge.” His lapidary talent for unique masterpieces was no longer needed once the Installation began mass production. And if a talent is unneeded, it is doomed to extinction.

Sakharov’s unusual—and saving—grace was his double talent. He was recognized as a theorist in the mid-1960s, when he began attending seminars at FIAN and the Institute of Theoretical and Experimental Physics. His colleagues were impressed by the juxtaposition of his two gifts as a theorist and as an inventor and designer. [2] They are as different from each other as the talents of theoretical physicist and writer. That is why such combinations are rarely encountered. [3]

Ginzburg, whose comment had hurt Sakharov’s feelings, expanded on his remark. “I can say this about him: He was undoubtedly a very talented man, he was made of the material of which great physicists are made. It’s just that…. He always had this inventive spirit.” [4]

Sakharov had a good idea of the stuff he was made of, even as a graduate student. But material alone is not enough. He describes with sober objectivity his early attempts to give the material a working shape—his successes and failures in that regard. In 1947 he lacked the spirit, intuition, and boldness to follow the path that would have led him to a major problem in theoretical physics of the time. [5] He did manage to take the first step down that road. He is being severe to himself when he sums up this way: “Everyone does the work he deserves.” However, this personal feeling does not block the general picture for him:

“Recalling that summer of 1947, I feel that I had never—before or since—had come so close to Grand science and its forefront. Of course, I regret a bit that I did not end up at the top (no objective circumstances are an excuse). But from a broader point of view I have to take joy in the progress of science—and if I had not been privy to it, I would not be able to feel it so acutely.”

His passionate preference is evident when he talks about theoretical physics. In describing his graduate work in his Memoirs, he lets fall mention about “pi-mesons” and their “isovector nature.” Hastily, he apologies in parentheses: “I do not explain certain terms in this book—let the non-physicist reader forgive me and simply regard them as misty, beautiful images.” Is there a non-physicist who would find anything but cold mist in the word “isovector”? But we can all feel the beauty of the narrator’s emotions over such intellectual matters. Especially since he was in his sixties, writing in exile under the vigilant eye of the KGB, and that the KGB had stolen the manuscript of his book several times already.

In recounting the great honor (and at first great difficulty) of an assignment --Tamm’s students had to report on the latest scientific articles at their seminars, he recalls describing the work of an American physicist and feeling “like a messenger of the gods.” When he finished, “Pomeranchuk rushed up to the board, terribly agitated, hair on end, and said something like, ‘If this is true, it’s exceptionally important; if it isn’t true, it’s also exceptionally important...’”

Pomeranchuk would later review Sakharov’s dissertation. He used the term “bubbles” for tasks that were not related to Grand science and not “exceptionally important.” Sakharov used this term when describing his first successful small theory, which he created in the spring of 1945, on the distribution of sound in water filled with air bubbles. He noted bitterly, “I often dealt with such unserious things, and in fact what I worked on between 1948 and 1968 was a very big bubble.”

We must remember that this was written in the early 1980s, in exile in Gorky, after he had switched to theoretical physics. And after he had shed his illusions about the Soviet state and anxiously wondered what use the country’s leaders might find for his inventions.

His penchant for inventing is obvious in his story of the first successful test at the cartridge factory in Ulyanovsk. In the Memoirs he relishes that period forty years earlier. He draws schematics in which "the core of a bullet slides, with light friction down the inclined copper pipe through a magnetizing coil," and explains how another, "demagnetizing coil helps determine whether the core is sufficiently tempered, consisting of steel with a reduced coercive force," and so on.

It is doubtful that more than one reader in a thousand would understand his explanation. But the remaining 999 will believe that he was “very proud” of the construction of a device to test the armor-piercing steel cores and that he was “rather sorry to leave my designing, which was beginning to come along.”

It is even easier to believe that the opportunity to invent in thermonuclear physics that would come up five years later attracted him just as much, and that if confidentiality were not required, he would have enjoyed describing his designs with the same pleasure.  That was a fascinating concept—to re-create the star’s source of energy on earth. He had complete freedom in selecting physics ideas in the construction. And he had the opportunity and even the requirement to embody the invention and test its viability.  When Sakharov called the physics of a thermonuclear blast “paradise for a theorist,” it was not just the theorist talking, but the inventor as well. Even when the duplicate test of 1962 cast a black shadow on his inventor side, Sakharov continued weapons development for another six years, and not because he was forced.

 

It is amazing that after almost twenty years Sakharov was able to return to creative work in theoretical physics, which had changed so much in those decades. Besides, physics is youth’s game, especially theoretical physics. People make their major contributions in theoretical physics when they are in their thirties. Sakharov returned to the field when he was in his forties.

Having two talents can be a help, and it can be a hindrance. Rarely, and this was the case in Sakharov, one can take turn feeding the other, keeping it from drying up. In hindsight, it is easy to speak of the benefits of switching creative energy from one field to the other. But it was hard for him to think in those terms in the early 1960s, when his inventiveness was confined to the military, and therefore harder to justify morally, and also becoming more boring. [6] Sakharov knew how quickly the train of scientific progress pulled away from the station, and he wasn’t sure that a forty-year-old could catch up and jump aboard.

He felt the gap back in the time of his first visit to the Installation, when Zeldovich asked him to give a lecture on quantum field theory. “”Unfortunately I had fallen behind (in two years), and a great leap forward had taken place in that period. I did not know the new methods and results obtained by Schwinger, Feynman, and Dyson; my talk was on the level of the rather antiquated books of Heitler and Wentzel.”

Looking back at his scientific career, sixty-year-old Sakharov saw how lucky he had been to be able to return to theoretical physics. In a “written conversation” with his wife—hiding from the KGB bugging of their Gorky apartment—he wrote of “four years of my scientific maximum, late by usual standards. In fact, it was a gift of fate that I could do anything after special work [bomb making]. No one besides Zeldovich and myself ever managed. In the US, neither Teller nor Oppenheimer could return to pure science. The exception there was Fermi. But he died soon after, and he was a genius.” [7]

Zeldovich’s name is there for a reason. He played an important role in Sakharov’s return to pure science—one could say that Zeldovich dragged him in with him.

 

The Physics of the Universe

 

Busy with his top secret duties, Sakharov followed from afar what was happening in the discovery of nature’s mysteries. After every trip to Moscow, Tamm and Zeldovich returned with scientific news, which they related to the theorists at the Installation. But that wasn’t the same as taking part in the work.

After Tamm left the Installation in 1953, two outstanding theorists remained by Sakharov’s side—Zeldovich and Frank-Kamenetsky. They were seven and eleven years older than Sakharov, had obtained major results before the war, and while working on the nuclear project continued doing pure physics and publishing articles.

 

Illustration [ 15_1Z-S-FK ] Yakov Zeldovich, Andrei Sakharov, and David Frank-Kamenetsky at the Installation.

 

A piece of not-very-serious evidence survives about what Sakharov thought then of pure theory. It is a sheet of paper recording in his hand the bet he made in 1956 with Frank-Kamenetsky. [8]

 

 

 

This was more than pure physics, almost metaphysics or even theology. Let us leave the question of how much truth there was in the joke to the last chapter. But apparently, Sakharov’s part in the bet was greater than his calligraphy. Frank-Kamenetsky devoted a lot to the study of stars and wrote a hefty tome in that field, but it was “earthly” astrophysics, based on astronomical measurements, and somewhat close to the “astrophysical technology” that was the work of the Installation. [9] The Universe as physical object—the subject of cosmology that awaited Sakharov—was far from Frank-Kamenetsky’s interests.

It is a very special subject. You can’t experiment with stars, either, but at least there are very many stars and you can observe and compare them. But the universe as a whole is by definition unique and even to declare that you see the object and not just some tiny random portion of it required exceptional intellectual daring. Or brazenness or irrationality. That was the opinion of Vladimir Fock, who helped his teacher, Aleksandr Freidmann translate his famous 1922 article on the expansion of the universe into German and who wrote a fundamental monograph on the theory of gravity. [10] The same attitude towards cosmology in the US in the 1950s is described by Steven Weinberg, later a Nobel Prize winner. “Everyone thought that the study of the early universe was not something to which a self-respecting scientist should be devoting himself.” [11] Cosmology was at a far remove from what was important in physics.

 

Einstein had made it possible in 1917 to speak of the Universe as a physical object on the basis of his theory of gravity, which united Newton’s law of gravity and the theory of relativity. But in the subsequent four decades cosmology essentially only gave the opportunity to speak in a mathematical language, not to take physical measurements and compare them with the predictions of theories, as it should be in the physical sciences.  In the course of those decades, cosmology received only one measurable fact, albeit an important one. The story of that fact reveals the uniqueness of the greatest natural object, the Universe.

The fact had been predicted in 1922, by Aleksandr Freidmann (1888-1925), a Russian mathematician who closely followed the revolutionary renewal of physics. Regarding Einstein’s cosmological theory with the eyes of a mathematician, he realized that the great physicist had found only one—very particular—solution for his equations. If we were speaking of a pendulum, we could say that Einstein found the tension when the pendulum is motionless. But a pendulum also can be in motion. Freidmann, basing his thinking on Einstein’s equations, described the “motion” of the cosmological pendulum—the Universe. It turned out that the Universe could expand -- that is, its component galaxies could move away from one another.

Freidmann sent the article about his discovery, called “On the Curvature of Space,” to a German physics journal in the spring of 1922 from a Petrograd (not yet renamed Leningrad) ravaged by the Civil War.  The unknown Russian’s results were so unusual that it was easier for Einstein to suspect that the author had made an error in his calculations. Which is what he wrote in his commentary published in the next issue of the journal. This is the famous error of Einstein. He soon understood it and published another note, in which he said Freidmann’s results were “correct and shed new light.”

It was not that theoretical light that helped cosmology take the next step, but the very dim light from distant foggy patches. They were studied by the American astronomer Edwin Hubble with a telescope. He was not studying gravity or the curvature of space. He concentrated on nebulae, which he recognized to be distant galaxies, and discovered that they were receding from our own galaxy, the Milky Way.

The changes in the tone of a locomotive’s whistle as the train rushes past an observer allow us to judge its speed. Similarly, a sophisticated observer like Hubble can measure the speed of distant galaxies by the changes in their weak light. And determine an amazing fact: the farther away the galaxy, the greater its velocity of recession. This observation, made in 1929, is known as the Hubble Law.

Theorists following both astronomy and physics realized that this was the expanding universe predicted by Freidmann. It was the cosmological triumph of theoretical physics. No other triumphs followed, however, for another three decades. Astronomers merely made Hubble’s measurements more precise.

No one doubted Hubble’s law, but some physicists were uncomfortable with the grandeur of an expanding universe and sought a simpler explanation for his observations. They found one in the murky waters of microphysics in the making. It looked like the aging of light particles, photons, over the enormous time of their travel from galaxies to Earth. The small effect of the disintegration of photons replaced the grandiose picture of the universe flying apart in all directions.

However, the cozy hypothesis was elegantly disproved in 1936 by the Russian physicist Matvei Bronstein, who had a profound understanding of both microphysics and cosmology. As a result, the empirical basis of cosmology was strengthened. But a single point of support is not enough for stable equilibrium. It was quite different from the other areas of theoretical physics, which were based on thousands of measurements.

Neither cosmology nor gravity were needed then to study the construction of matter. The forces in microphysics are greater than gravity by an unimaginable number that is forty digits long. Only if an equally astronomical number of particles are gathered in one place would gravity be needed. But by then we move from physics into astronomy. And the theory of gravity and cosmology require a special mathematical language that was not needed in other areas of physics.

These circumstances made cosmology at best a respected but eccentric and distant cousin of the rest of the physics family. Very few physicists had the time and curiosity to maintain professional relations both with cosmology and microphysics. Among those few was Landau, who included the theory of gravity in his famous Course on Theoretical Physics.

This book might have helped Sakharov, back in the late 1940s, to keep both edges of the physics world in his field of vision. He kept a journal of articles that interested him, and next to the news of microphysics we can find a notation about the expanding universe from a 1949 Physical Review, the leading American journal. [12] The move to the Installation and H-bomb physics kept him from pursuing this for years.

 

In the early 1960s cosmology unexpectedly moved from dotty spinster aunt to intriguing debutante. By 1967 Zeldovich published a book with a co-author summarizing the early years of cosmology. [13] The book recounted Bronstein’s work on physical cosmology of the 1930s, even though no one doubted the expanding universe after the discovery in 1965 of cosmic background radiation homogeneously filling the universe.

This phenomenon, like Hubble’s moving galaxies, had been predicted by Gamow in 1948 but discovered accidentally. Cosmic radiation was of the same nature as heat coming from a stove—one “heated” to minus 270 degrees Celsius, just three degrees above absolute zero. The discoverers won a Nobel Prize. Theoretical physicists saw in this radiation not only expansion of the universe but also a sign of something about the early phase of the expansion.

If the galaxies are moving apart, they must have been closer to one another at some point, and therefore once formed a solid mass that was not separated by cosmic space. It was heated to huge temperatures, and consequently permeated by intense radiation. The unexplained event that took place billions of years ago, in the very beginning of the cosmological expansion, was called the Big Bang, or the birth of the universe. As the universe expanded, the radiation cooled down. Over the billions of years, it cooled down billions of times. But a sensitive apparatus picked up the relict of Big Bang, and hence the name relict (or background) radiation.

Besides this, the most impressive cosmological discovery, in the 1960s astrophysicist discovered a few other amazing phenomena. New concepts entered the science vocabulary: quasar, pulsar, and black hole.

Zeldovich burst into the area, where the latest discoveries combined with theoretical puzzles of the distant past, with his first work on cosmology in 1961. “After him, I began thinking about 'Great Cosmology' myself,” wrote Sakharov. By then Zeldovich had written several dozen works on fundamental physics; he never gave up his connection to pure science. But Sakharov was concentrating on H-bomb physics.

 

From the Atomic problem to the problems of the Universe

 

Zeldovich and Sakharov were radically different even in the external style of their scientific lives. It is said that the predilection for polygamy or monogamy lies deep in the structure of the personality. Zeldovich had quick affairs with various scientific ideas, which he carried out to the birth of a publication. In his lifetime he published about three hundred works in pure science with several dozen co-authors.

Sakharov has only two dozen pure science works and no co-authors, except Zeldovich. This exception shows us that Zeldovich knew what he was doing when he tried to bring Sakharov into pure science. For physicists who lived outside the Installation and had to judge by his publications, Sakharov was a dark horse. Zeldovich knew, without any publications but from personal experience, that Sakharov was rather a “talking horse,” as he put it. [14] Their first joint article of 1957 went back to Sakharov’s 1948 secret report at FIAN on muon catalysis. [15] Zeldovich’s work notebooks for 1957, dealing with this work, have a notation: “Sakharov’s most profound idea.” [16] Profound ideas don’t come frequently. A physicist from the Installation recalls Zeldovich saying, “Andrei, it’s two years since you’ve had a knock-out idea.” [17]

For the self-contained Sakharov, Zeldovich was the best window into science. He could replace several seminars and the usual post-seminar scientific chat. With his acute perception, fast thinking, and erudition, Zeldovich knew about everything and was interested in everything even if he wasn’t working on it himself at the moment. In the prewar years, for instance, his work had nothing to do with cosmology, but when he heard Bronstein’s elegant theoretical construction, it stayed with him until he used it thirty years later in the first Soviet book on cosmology. History of science per se did not interest him: “The past of the Universe is infinitely more interesting that the past of science about the Universe.” [18] It may have been because science alone is not enough to understand the history of science, even the history of such a pure science as cosmology.

Explaining the sharp turn in his scientific life, in 1984 Zeldovich, then seventy, referred tactfully to the “atomic problem” that had “captured me completely.”

“In those very difficult years, the country spared nothing to create the best working conditions. For me they were happy years. Big new technology was being created in the best traditions of big science. … By the mid-fifties, some priority tasks were already resolved. … Work in the field of the theory of explosion was psychological preparation for the biggest explosion—of the Universe as a whole. … Work with Kurchatov and Khariton gave me a lot. The most important is the inner sense that I did my duty for country and people. This gave me a certain moral right to subsequently work on such issues as elementary particles and astronomy, regardless of their practical value.” [19]

There wasn’t a syllable about bombs here, but the tactful Soviet reader understood. And almost all the necessary elements for explaining the turn in Zeldovich’s scientific career are here, although some of the elements are turned around or need translation from Aesopian Soviet to ordinary language.

In the US a similar transformation took place with John Archibald Wheeler (b. 1911), the first American involved in the theoretical development of the atomic problem (through his and Bohr’s paper of 1939). He also took part in the development of the H-bomb as director of Project Matterhorn at Princeton (1951-1953). [20] It was mentioned earlier that the secret document he lost on a train in January 1953 was suspected of reaching the Soviet Union. There is more reason to suspect that Wheeler had seduced his thermonuclear counterpart Zeldovich into pure gravity.

A few years before Zeldovich became the principal cosmologist in the Soviet Union, Wheeler became the principal US theorist in gravity. One did not need to steal documents to learn that the prominent American nuclear physicist had changed profession. One merely had to read the Physical Review. But a physicist as talented as Zeldovich does not follow examples; he is motivated from within. [21]

An aptitude for leadership can explain why the two former weapons physicists became national leaders in gravitation and cosmology. But the switch in scientific orientation is tied to something else, which is the same despite the differences in socialism and capitalism.

If we spell out everything that is between the lines in what Zeldovich wrote, we get the following picture. In the late 1950s (a bit earlier in the US), theoretical physics of thermonuclear weapons had exhausted itself and was replaced by engineering physics. The priority of new technology had been solved: American and Soviet physicists had created the greatest scourge for their politicians. It was called MAD, Mutual Assured Destruction, the ability of each superpower to destroy the other even after a sudden enemy attack.

As a result, the authorities recognized the connection between new technology and science, and out of respect for those who made the connection possible, permitted them to work on whatever they wanted (probably with the thought that their impractical interests might nevertheless give rise to the next major technological breakthrough). Theoretical research did not require a lot of funding. Incomparably greater sums were spent on experimental science—particle accelerators and space ships.

“Work in the field of the theory of explosion” could be psychological preparation for cosmology only by accustoming scientists to the distance between theory and testing, and therefore to boldness in science. At the Installation, the leading physicists had to create a theory of the thermonuclear bomb without being able to test their calculations on small trial explosions in the lab. First, the complete theory, and only then a full-scale megaton blast … or a dud. This is comparable with cosmology in psychology rather than scale. You have to dare to create a theory on such a non-observable object as the Universe billions of years ago.

And then there is what Zeldovich called the moral right to take up areas “regardless of their practical value.” We can easily imagine how the physicists who created the horrifying thermonuclear mushrooms while doing their “duty for country and people” were ready to escape from their practical application.

The escape route might be prompted by the Soviet newspapers of the early 1960s. There were articles about new subjects of study—in space. The Installation’s theorists knew better than anyone else that the signals from the first sputnik and Yuri Gagarin’s smile were not really from the realm of science but from the next “big new technology,” which would deliver the technology they had invented for distances of thousands of kilometers. But they also knew that moving away from the planet’s surface by just a hundred kilometers vastly expanded the horizon -- literally. Astronomical observations made without atmospheric interference promised great discoveries. This was confirmed very quickly. The discovery of background radiation -- the remains of the hot time of the birth of the Universe—came by accident in 1965, but it was no accident that the discovery was made while working on radio communication with satellites.

These factors came into play only because the theory of gravity and cosmology offered intriguing questions—real mysteries of nature in pure form. And only pure science could find the answers.

In describing his return to pure science, Zeldovich does not mention Sakharov’s name in his 1984 autobiography. It was the fifth year of Sakharov’s exile, and the Soviet censors kept a sharp eye for the bad name. [22] But Sakharov and Zeldovich came to cosmology together twenty years earlier.

 

Zeldovich called what he was doing “relativistic astrophysics,” that is, the physics of cosmic phenomena that required the theory of relativity for an explanation. Relativistic astrophysics covers the physics of exotic objects in space, and the physics of the exotically single object -- the Universe as a whole .

We can imagine quasars, pulsars, and black holes among the luminous stars in the sky. And it is easy to imagine how telescopes show these objects with greater magnification and in greater detail. But no telescope can show the entire Universe. Here only the eye of the intellect can help.

If we judge by their publications, Zeldovich began before Sakharov. By the time Sakharov published his first work on cosmology (1965), Zeldovich had written over two dozen. But if we look into their informal communication, a different picture arises.

Think of the bet Sakharov made with Frank-Kamenetsky in 1956, five years before Zeldovich’s first publication on cosmology. The brief text of the bet makes clear that Sakharov already saw “the Universe for all degrees of freedom for all times.” Sakharov’s serious style excludes the possibility that he would put together such seemingly incongruous words without consideration. Therefore he was thinking of the Universe as a physical object as early as 1956. In that era, it was an extremely exotic object for a working physicist. And no one in Sakharov’s circle seems likely to have helped him develop that viewpoint.

V. Ritus, wrote of Tamm in his memoirs (without mentioning Sakharov’s name): “When one of his senior students got interested in cosmology and put forward several rather abstract ideas, Tamm shared his surprise and regret with me, saying that these hypotheses were impossible to prove or disprove in the visible future.” [23]

Knowing Zeldovich’s attitude toward Sakharov’s “profound” and “knock-out” ideas, we can assume that Sakharov’s confidence in treating the universe as a physical object strengthened Zeldovich’s resolve to take that object into his arsenal.

Ten years after the cosmological bet made by his friends at the Installation, Zeldovich had a wonderful idea: to fill all the space in the Universe with vacuum. But when he brought it up at a seminar, he was met with ruthless criticism. He called Sakharov, who liked the new idea so much that he took the next step. According the Wheeler, it was an incredibly bold one.

Sakharov was emboldened by the pure science work he took up after a long hiatus in 1963. He worked following the direction of Zeldovich’s thoughts, and he thanked him for “numerous discussions that led to the problem’s formulation as a whole and enriched the work with many idea.” [24] Following Zeldovich, in that work Sakharov assumed the hypothesis of the “cold” early Universe. The discovery of the cosmological background radiation proved, however, that the early Universe was hot. And so Sakharov’s first work on cosmology went to the archives of “unemployed ideas” created in theoretical physics (perhaps up to 95% of new theoretical ideas end up in these archives).

Nevertheless, the work was a turning point for Sakharov, and he even remembered the day he found the solution to a difficult question—April 22, 1964. “I believed once again in my powers as a theoretical physicist. It was a kind of psychological warm up, that made possible my subsequent work of those years.”

His new confidence shored up his Program for 16 Years, which he wrote for himself on a single sheet of paper in 1966. Why for sixteen years? Perhaps because he had spent the previous sixteen at the Installation, removed from Grand science. Apparently for the same reason, the program included sixteen topics beginning with the solemn “Photon + Gravitation” and ending with the mysterious “Megabittron.”

 

Illustration [ 15_3_16letka_66 ] “Program for 16 Years, which Sakharov created for himself in 1966. Why 16? Perhaps because he had spent the previous sixteen at the Installation, removed from Grand science. Apparently for the same reason, the program included sixteen topics. Of particular interest is point 14. Apparently, after deciding to find 16 tasks, he pondered at this point, put a question mark, remembered how resistant science is to planning, and added: “This is just what I’ll probably be doing.” He turned out to be right, and he took up “just that,” the unplanned, soon after, and even wrote two of his brightest theoretical works for that point. In thinking about complex physics-mathematical materials, the academician skipped point 8. Otherwise, he would have had to come up with one more task. But that turnes point 14 into 13, which may explain its special nature.

 

Of particular interest is point 14. Apparently, after deciding to find 16 tasks, he pondered on this point, put a question mark, remembered how resistant science is to planning, and added: “This is just what I’ll probably be doing.” He turned out to be right, and he took up “just that” soon after, and even wrote two of his brightest theoretical works on that point.

First he found an explanation for why there are many more elementary particles in the Universe than antiparticles -- in the language of physics, he proposed a way to explain the baryon asymmetry of the Universe. That was the most successful of his ideas in pure physics.

Rivaling it in beauty and unexpectedness was his new approach toward gravitation. In the old universal gravity he discerned a manifestation of ultramicroscopic qualities of space-time itself.

The two ideas that Sakharov encountered in 1966-67 deserve further discussion.

 

Symmetries in the asymmetrical Universe

 

Finding a definition for “beauty” is a thankless task. Of its synonyms, the one most appropriate in the sciences is “symmetry.” The concept can be expressed with mathematical precision and it is visible. The symmetry of a butterfly’s wings is the simplest (and most appealing) example.

This simple quality from the everyday world moved into geometry, where it received a mathematical description. Symmetry is the rule of form that keeps the form unchanged under specific circumstances. If you reflect a butterfly’s right wing in a mirror and put it in place of the left, no entomologist would be able to tell the difference.

Armed with the power of mathematics, the concept of symmetry became an instrument of theoretical physics in the study of the deep structure of nature. Physics traveled a long way before finding in its laws manifestations of the Universe’s symmetries. Everyone knew that a spinning top will remain upright in one spot and not fall. It does not fall because, we could put it this way, it does not know where to fall: All directions perpendicular to its axis are equal -- that is, all directions in space are symmetrical relative to that axis. In the language of physics, that sort of symmetry determines the law of conservation of angular momentum, the main law for the spinning top.

Symmetry is one of the most workable concepts in physics. The behavior of a top or a single atom or a thermonuclear blast is determined by symmetry. A theorist always begins with the most symmetrical simplification of his problem. Every fundamental law of physics reveals a symmetry in nature. If an asymmetry is found in natural phenomena, the theorist sees a difficult but fascinating problem: to find a place for that asymmetry in the harmony of the universe.

“It is known that Maxwell’s electrodynamics—as usually understood at the present time—when applied to moving bodies, leads to asymmetries which do not appear to be inherent in the phenomena.”  This is the beginning of Einstein’s first article on the theory of relativity. With that theory he overcame the asymmetry that is not inherent to the phenomena themselves— he created a description in which that asymmetry is merely one facet of the profound symmetry of nature.

Another triumph of symmetry in physics was achieved by Paul Dirac. In the late 1920s he took on a purely theoretical problem. There were two fundamental theories at work at that time: the theories of relativity and quantum mechanics. The first provided description of phenomena with velocities up to the speed of light. The second described the behavior of microscopic particles. But nature does not keep its phenomena is separate compartments, and Dirac wanted to find out what directed the motion of the electron when both theories were necessary at the same time. He managed to unite the theory of relativity and quantum mechanics in one elegant, albeit unusual-looking, equation for the electron.

There was only one impediment. Dirac’s equation required the existence of another particle, in some way quite similar to the electron, in others completely the opposite. The particle had to be exactly like the electron in mass, but the opposite in charge. And a meeting of the two would lead to mutual destruction -- annihilation.

Even though no other particles were known to physics then but the electron and proton, Dirac believed in the symmetry of his equation and, in 1931, predicted a new particle, which he called the anti-electron. A few months later, it was found in studying cosmic radiation. In honor of its positive charge the experimenter discoverer, Carl Anderson, called it the positron, but this name does not reflect the particle’s main quality—being the anti-copy of the electron. Later other elementary particles and their anti-copies would be named properly: antiproton, antineutron, anti-sigma-hyperon, and so on (or anti-so-on).

The main relationship between a particle and its antiparticle is that they annihilate each other when they meet, giving birth to particles of light, or photons, which have no charge and inherit the energy of the parent pair. Conversely, if a photon has enough energy, it can turn into a particle and its antiparticle.

The power of the symmetry of equations in explaining the real world prompted Dirac to persuade many of his colleagues that “Physical laws should have mathematical beauty.” The story of his success is a favorite among theoretical physicist. In any case, Sakharov kept the story of the anti-electron close at hand. When he once was showing his ability to do mirror writing, he wrote “Electron + Positron = 2 photons.”

 

Illustration [ 15_4e+p_mirr ] A summary of Dirac's success story in Sakharov's mirror writing and in English translation. Plain English for the Greek letter gamma is "photon"

 

He also demonstrated his ability to write in different directions simultaneously with both hands, writing his hostess’s name. When Lydia Chukovskaya, who kept his examples of writing, tried to repeat his trick, she failed, as we can see.

 

Illustration [ 15_5KL-LK_hand79 ] Sakharov demonstrated his ability to write simultaneously with both hands, writing his hostess’s name and patronymic. When Lydia Chukovskaya, who kept his examples of writing, tried to repeat his trick, she failed, as we can see. And if she had been ambidextrous like Sakharov and if they both had written in English, they would have come up with something resembling the butterfly shown on the right.

 

Mirror symmetry—the symmetry of the butterfly—like mirror asymmetry, embodied in the double autograph shown above, has something to do with Sakharov’s most significant idea in cosmology.

 

Matter and Antimatter in the Universe

 

In 1966, soon after Sakharov made himself a scientific plan for the next sixteen years, he noticed an asymmetry in nature that was becoming evident in those years: There were many more particles in the Universe than antiparticles.

Every since Dirac predicted the existence of antiparticles in 1931, matter and antimatter had an equal right to exist as far as physicists were concerned—in theory. In practice, after Carl Anderson discovered the first antiparticle, the anti-electron, aka positron, in 1932, it took another three decades to observe the next antiparticle, the antiproton. And it was only a few years ago that physicists managed to create the first simple anti-atoms—anti-hydrogen atoms—out of antiprotons and antielectrons. They made nine. The first anti-atoms existed for only billionths of a second before they met with normal matter and were annihilated.

In a popular article on antimatter, Sakharov gave this example: “The annihilation of 0.3 g of antimatter with 0.3 g of matter will give the effect of the blast of an A-bomb.” [25] That was his second profession speaking. The contact of two small tablets would cause the same blast as twenty thousand tons of ordinary explosives.  That could made one lose any sympathy for the experimental physicists creating anti-atoms. Just imagine if antimatter were easy to create.

But sympathy for the theoretical physicists could increase. All the experiments with antiparticles did not change a thing in the theoretical equality of matter and antimatter that the theorists understood back in the 1930s. How could the empirical and theoretical results be made to match? What was the explanation for the fact that matter and antimatter were so inequitably represented in the Universe?

The most tangible part of matter are nuclear particles—protons, neutrons, and their close relatives. Physicists gave them a family name—baryons. And the apparent absence of antibaryons is called the baryon asymmetry of the Universe.

As long as physicists regarded the Universe merely as a collection of various astronomical objects, they could think that matter predominated in the cosmic neighborhood of Earth and that farther away there were stars and planets of antimatter. Astrophysicists looked for signs of antimatter in the space. Science fiction writers created dramatic encounters between spaceships from earth with extraterrestrial ones made of antimatter. There was even a joke that the best way to tell if a spaceship had come from an anti-world was if most of the physicists on board were anti-Semites.

The situation changed dramatically after the 1965 discovery of cosmological background radiation. Even skeptics had to believe the Universe could be treated as a single physical object with its history determined by the laws of physics. It was clear that the Universe had once been very hot. The remaining background radiation had cooled to a temperature only three degrees above absolute zero, but there was a lot of it -- it filled the entire space of the Universe. Ordinary matter was concentrated in the stars and planets, separated by enormous distances.

If radiation and matter were recalculated in particles—photons and baryons—then we would see that now for each baryon there about one billion photons, today’s “barely warm” photons. But what had been the case yesterday? When the Universe was smaller in size, the photons, according to the laws to radiation, were warmer. And if we go back far enough, there was a time when the energy of the average photon was enough to give birth to a baryon and antibaryon pair. Until that moment, photons easily turned into such pairs, and the pairs upon meeting just as easily turned into photons, by annihilation. In that hot period, there were approximately as many such pairs as there were photons. And that means that there were a billion times more baryon-antibaryon pairs than the excess of baryons over antibaryons that is observable today. These are the baryons that remained after all the baryon-antibaryon pairs were annihilated into photons, which in the process of expansion cooled so much that they lacked the energy to create new pairs.

That means that in the very young and hot Universe, there was only one billionth part more baryons than antibaryons. Thus the asymmetry in nature is not simply small but challengingly small.

Sakharov had “trouble imagining” that originally, in the nature of things, for every 1,000,000,000 photons there were just as many antibaryons, 1,000,000,000, and only one more baryon—1,000,000,001.  These starting numbers, in Sakharov’s view, “offend the eye: ‘it couldn’t have happened that way.’ It was this circumstance (as the reader sees, intuitive rather than deductive) that was the stimulus for a lot of studies on baryon asymmetry, including my own.”

It was a stimulus for Steven Weinberg, 1979 Nobel Laureate and author of a best-seller on the first three minutes of the Universe. In 1977 he wrote: “The baryon number per photon might have started at some reasonable value, perhaps around one, and then dropped to its present low value as more photons were produced. The trouble is that no one has been able to suggest any detailed mechanism for producing these extra photons. I tried to find one some years ago, with utter lack of success.” [26]

Therefore, Weinberg decided to ignore all “nonstandard possibilities” and accepted baryon asymmetry as an inexplicable fact. By the time Weinberg’s book came out in Russian in 1981, it was clear that he should not have ignored the nonstandard possibility indicated by Sakharov in his paper of 1967 [27]  (and presented in the next paragraphs). Zeldovich, who was editor of the Russian translation, devoted a special appendix to that possibility.

But even Zeldovich, who was the first to learn of Sakharov’s work, long considered it too strange to be correct. Sakharov recalls a conversation in 1967: “Zeldovich asked which of my purely theoretical works I liked best. I said: “Baryon Asymmetry of the Universe.” He winced and said, “Is that the work where the baryon number is not conserved and time flows backward?’ ‘Yes, that’s the one.’ Zeldovich said nothing, but it was clear that he had great doubts about the value of my ideas.” [28]

Sakharov’s new idea seemed “fantastic and crazy” even to Feinberg. When he received a copy of the article with the author’s inscription, he thought, “Well, sure, Sakharov can indulge himself in anything, even fantasy like this.” [29]

The inscription was in verse:

 

With S. Okubo’s effect

And at high heat,

A skewed coat was made to fit

And on the Universe look neat.

 

What fantastic craziness lay behind the verse?

 

Illustration [ 15_6Okubo67 ] Poem expressing the idea of baryon asymmetry (on a copy of the 1967 article given to E. Feinberg)

 

We know that the figure of the universe is (baryonically) skewed and we know that theoretical physicists were bothered by that fact it was only slightly skewed, by one billionth part. No tailor would alter a suit to accommodate a difference of one millimeter between right and left shoulders. Cosmologists were worried by a difference a million times smaller—but only because that difference seemed to be related to the very genesis of the Universe.

 

Sakharov's Three Conditions for the Universe

 

The American theorist Susumu Okubo was not thinking about cosmology. In the mid-1950s he was working on the physics of elementary particles when mysterious asymmetries surfaced. Before then the unspoken understanding was that everything in the world of elementary particles had to be extremely symmetrical. These minimal components of matter seemed to have nothing like right and left hands. And therefore there could be nothing like the asymmetry of the right-handed and left-handed in the world of people. In the world of elementary particles, it was assumed that mirror symmetry ruled—total parity of right and left, or P-symmetry, like the wings of an ideal butterfly.

Illustration [ 15_7P-babochk ] P-symmetrical butterfly

 

To be more accurate, it was believed that if a phenomenon was possible in the world of elementary particles, then if that phenomenon were reflected in the mirror—switching right and left—we would get a phenomenon that was just as possible.

In 1956 a momentous event occurred: It was discovered that the world of elementary particles is not fully P-symmetrical. That is, there were phenomena whose mirror image was not as likely. This observed asymmetry in the microworld disconcerted physicists. They began looking at two other symmetries, which until then had been considered as certain. Operation C replaces any elementary particle with its antiparticle, that is, any charge with its opposite. Operation T turns time backward, that is, replaces any movement with movement in the opposite direction. Let us imagine all particles as white billiard balls and their antiparticles as black ones. Then operation C changes the color of the balls to the opposite and operation T changes the collision of the balls, as recorded on video tape, to what it would be if the tape were played in reverse.

Each one, P, C, and T are like the wave of a magic wand. So, in 1956 physicists learned to their surprise that a wave of P-wand changes the microworld. What did follow from the basic principles was that waving all three wands at the same time changed nothing in physics. They called that CPT-symmetry.

But how about separately? For a few decades, physicists had been certain that the microworld was symmetrical for any of the C, P, T magic wands. It might have been easier being a theorist in such a world -- if people’s right and left hands were the same, making gloves would be twice as simple. However, it is probably impossible to understand humans if you ignore the differences between the right and left hemispheres of the brain, the imaginative and logical locations. Simplicity can be worse then theft, as the Russian saying goes. An oversimplification of the world steals the possibility to comprehend it.

The problem is that there is no formula for avoiding oversimplification. The only reliable instructor in the matter is the experiment or the wise question skillfully posed. The mirror unevenness of the microworld, shown by experiments, pushed physicists to build castles in the air, in which the asymmetrical out-building was part of a symmetrical universe. Within a year, one castle was completed. Landau found that all then-known P asymmetrical phenomena were subordinated to combined CP- symmetry, and he proclaimed that symmetry a new law of nature: The simultaneous waving of the C- and P- wands does not change the world. [30] In other words, Landau proposed that the butterfly of the microworld had a form that did not change if you simultaneously switched the right and left and black to white -- that is, the particles switch places with the antiparticles and the right switches places with the left.

 

Illustration [ 15_8CP-babochk ] CP-symmetrical butterfly

 

Landau’s cutting edge work drew a lot of attention. It was his first work sent to Nuclear Physics, and according to Okubo, the editor of the journal, Leon Rosenfeld, “was so pleased to have received a paper from such an eminent physicist as Landau directly from Russia, that he published it immediately without any delay instead of its being sent for refereeing as was normally done.” [31]

A scientific paper’s importance can be measured by how much it helps pose new questions to nature, and – if the answers are negative—helps to disprove itself. Landau’s work helped Okubo ask: What if even CP-symmetry is not all-powerful in the microworld? And he figured out how to pose that question to nature. In his two-page article in 1958 he pointed out that if CP-symmetry is not valid, then a particle and an antiparticle with the same lifetimes could end their lives differently—breaking down differently into other particles. [32]

This remained a purely theoretical possibility until 1964, when it was discovered that CP-symmetry was not absolute. It, too, was violated, albeit rarely.

 

Strangely enough, the main Soviet theorist in thermonuclear weapons followed these pure subtleties unrelated to his work. This is evinced in Sakharov’s evaluation of Landau’s works on CP symmetry, by request of the Lenin Prize committee (and sent on 18 December 1958). He summed up by saying, “In his influence on the development of science in our country and the entire world, Landau is one of the top figures.” [33]

Landau was not then awarded the Lenin Prize, and probably not because the Central Committee of the Party had a different view of the CP-symmetry problem. They had in their possession a lengthy KGB report that Landau had dared to name Lenin "the first fascist.” [34] How could they give him the Lenin Prize?!

For all his disagreement then with Landau’s anti-Lenin formulation, Sakharov was unlikely to have considered it relevant to an assessment of Landau’s work. And it did not matter that Landau’s 1957 hypothesis on combined CP-symmetry was disproved by experiments in 1964. The main thing was that his work had moved forward the search for scientific truth.

 

In 1966 it was Sakharov’s turn to move the search forward. He began thinking of the experiments on violations of CP-symmetry and the Okubo effect in combination with the fact of the baryon asymmetry of the universe. And he came to the idea of a microphysical genesis of that asymmetry—the skewed figure of the universe. He began with the fact that in the microworld only the most general CPT-symmetry worked and the butterfly of the microworld looked like this:

 

Illustration [ 15_9CPT-babochk ] CPT-symmetrical butterfly

 

It does not change only if all three switches are done simultaneously: left and right, particle and its antiparticle, past and future.

Next to this butterfly of the microworld Sakharov placed the butterfly of the expanding hot Universe.

 

Illustration [ 15_99Cosmic-babochk ] Butterfly of the expanding Universe   [Note to art director: It would be good to make this butterfly resemble the preceding ones in form and that the viewpoint would show it at an angle, so that the second wing would be disappearing into the distant blue. The “caterpillars” are the spiral galaxies in the process of formation: the ones closer to the beginning are more shapeless.]

 

He used the CPT-symmetry of microphysics to explain the asymmetry of the Universe. In the era of the Big Bang, when matter was so compressed that the elementary particles felt one another, the Universe sensed the laws of the microworld directly. It was then that the asymmetry of the Universe, according to Sakharov, formed in the processes that were taking place in every micro-point all over the cosmic space. T-asymmetry allowed the birth of now-observable C-asymmetry—the difference in content of particles and antiparticles.

Besides the wing of the Universe’s butterfly that is visible to astronomers, Sakharov could visualize the other wing that opened before the Big Bang. The cosmological butterfly is CPT-symmetrical, but it cannot be seen whole because of the brevity of human life compared to the age of the Universe.

In inventing the mechanism that creates an excess of baryons over antibaryons from the original symmetrical state, Sakharov used three gears:

1) “With the effect of S. Okubo”—the difference in decay of particles and antiparticles;

2) “at high heat for the Universe”—this condition creates the necessary cosmological effect for an ultrabrief period, while the Universe is hot enough, and then the result freezes;

3) “a coat is made” with a needle that was a new instrument for physics. Sakharov proposed that the baryon number is not conserved. This meant that the proton, the “brick of the universe” that was considered to be completely stable, had to decay on its own.

 

At the end of the paper, Sakharov thanks six physicists for discussion and advice, starting with Zeldovich. [35] Zeldovich had brought Sakharov to the Institute of Theoretical and Experimental Physics, to the students of Pomeranchuk—B. Ioffe, I. Kobzarev, and L. Okun. They knew everything about C, P, and T and so on (it was in discussions with them that Landau came up with his CP idea).

Lev Okun, who helped Sakharov with his suggestions, considers his paper on baryon asymmetry of the Universe “one of the most profound and bold articles of the twentieth century.” [36] No one doubted its boldness at the moment of its birth. Sakharov took aim at the seemingly untouchable law of conservation of baryon number.

In school we study only electric charges, whose conservation is one of the most basic properties of electromagnetic field. Conservation of baryon charge was not a result of some profound theory of baryon field, it was based only on the fact that other behavior had not been observed—the decay of the proton. This is a fact worthy of respect, and Sakharov showed his respect by estimating  the rate of decay of the proton in the theory he proposed. The decay was so "astronomically" slow that it explained why it had not been observe—it required an unthinkable precision of measurement.

Whether to respect a fact, bear it in mind, or obey it unquestioningly is a decision left to the researcher.  In the late 1960s, the great majority of physicists, among them, Zeldovich, chose absolute submission to baryon symmetry. History held a mini poll on this issue among the theorist fathers of American nuclear weapons. In 1966 articles, both Robert Oppenheimer and Edward Teller expressed full confidence in conservation of baryon charge.[37]  Teller was confident enough to suggest an explanation of quasars as a collision between a galaxy and an antigalaxy, of which there should be equal numbers in the Universe.  As the Russian bard Okudjava sang in those days, “everything is equal, everything is fair—for every wise man there is a fool, for every flow there is an ebb.” For every proton there is an antiproton and for every galaxy there is an anti-galaxy.

 

Then why did Sakharov decided to leave this unanimous chorus in 1966?  Perhaps he had understood better than the rest the lesson of CP-symmetry according to which in physics, as in a society ruled by law, everything was permitted that was not forbidden by law. Or perhaps he had a deeper understanding of the fact of cosmological asymmetry of matter and antimatter and did not try to convince himself that the asymmetry observed on Earth, locally, could somehow be made compatible with the overall symmetry of the Universe. But what we are actually talking about is the depth of scientific intuition which is based on facts and theories but is not reduced to them.

When Sakharov realized in 1948 that the H-bomb design he received from Zeldovich was leading nowhere and found a completely new path, that was his scientific intuition at work. Zeldovich “instantly appreciated the seriousness” of his discovery.  In 1966, the path proposed by Sakharov diverged too sharply from the well-worn tracks, and it took Zeldovich, who saw Sakharov’s intuition work “before his very eyes,” years to fully evaluate its seriousness. It happened when the development of the theory of elementary particles—for the so-called Grand Unification—also questioned the stability of proton.  It was only then that Sakharov’s explanation of the baryon asymmetry of the Universe took its proper place at last in the arsenal of contemporary physics.

In Okubo’s words, “Although the idea appears now to be so simple, it is due to the genius of Prof. Sakharov [that he was able] to combine many different aspects of theory into a coherent picture.” [38]

It is too soon to put this picture in a gilt frame. Physicists in many countries are checking the elements of the picture experimentally. That is the usual way of development of ideas in physics, a development in which the international physics community extracts knowledge for humanity through cooperation and competition.

We will certainly learn in this millennium where the experimental testing and development of the theory that explains the asymmetry of matter and antimatter will lead. But its more immediate prospects are described in Scientific American: “It is imaginable that the universe was born skewed—that is, having unequal numbers of particles and antiparticles to begin with. … Theorists prefer the alternative scenario, in which particles and antiparticles were equally numerous in the early universe, but the former came to dominate as the universe expanded and cooled. Soviet physicist (and dissident) Andrei Sakharov pointed out three conditions necessary for this asymmetry to develop.”[39]

In proposing the nonconservation of baryon charge—the instability of the proton—as one of those conditions, Sakharov was being a dissident in physics. He was not afraid to speak about what he saw with his own eyes when others had not yet seen it or were afraid to look. It is not yet known whether he had discovered a new law of nature. But we do know that the mysteries of nature reveal themselves only to such dissidents.

 

Sakharov’s work was not at the very center of theoretical physics or even of the part that Sakharov considered his own —“elementary particles, gravitation, and cosmology.” [40] Hundreds of theorists were working in each of the three fields. What distinguished Sakharov was that he united them. His work was the first to define a concrete characteristic of the Universe as a whole by the characteristics of the microworld.

Sakharov’s explanation of baryon asymmetry of the Universe in 1967 merely opened up a new direction for scientific research; it did not close it by being an exhaustive and complete theory. This direction is sometimes called cosmomicrophysics—the combination of the physics of the microworld and the megaworld.

To this day, revealing the decay of the proton is a goal of experimental physicists, and this goal also effects the Grand Unification Theory, which is intended to unify all fundamental forces with the exception of gravitation.

 

The Elasticity of Vacuum

 

It was gravitation that the second of Sakharov’s exceptional ideas was aimed at. Fate, as he used to say, gifted him with this idea in 1967, and Zeldovich was involved in that gift.

It started with Zeldovich's idea to fill emptiness with a vacuum. He filled the empty space-time of Einstein’s theory of gravity with the quantum vacuum of microphysics. By that time the empty space-time no longer resembled a box without walls filled with the ticking of an invisible clock. In the late 1940s experimenters confirmed what the theorists had been saying since the early 1930s: If you remove all the contents of a vessel, what would be left was not lifeless emptiness. Life seethed quietly, with particles continually being born and dying—fluctuating—and that nonstop simmer is able to change the color of a flame. The change is slight, but the experimenters noticed it. In order to get away from the old-fashioned emptiness, they used the Latin word—vacuum.

Physicists were looking at vacuums through a microscope, so to speak, but Zeldovich suggested using a telescope. He proposed that the living vacuum revealed in microphysics could have a gravitational effect on the megaworld—on the rate of expansion of the Universe. In this way he proposed to explain the new astronomical data on the strange distribution of quasars. [41]

Zeldovich spoke of his idea at a FIAN seminar and found no support. The idea contradicted the habitual viewpoint that the vacuum acted only on elementary particles and that for greater bodies, macroscopic ones, the vacuum was merely emptiness. Besides, physicists did not accept the reason that prompted Zeldovich to make such a bold statement. And in fact that “observable fact” that had aroused Zeldovich’s imagination (a peculiarity in quasars distribution)  soon vanished like a mirage amid new observations.

Anna Akhmatova’s lines apply to more than poetry:

If you could but know the trash from which poems grow,
Without the slightest shame --
Like the lowly weeds you can no longer name,
Sprouting by the fence from seeds you did not sow.

Scientific ideas sometimes also sprout by the fence.

Sakharov missed Zeldovich’s talk, but he learned from him that the FIAN theorists were “sharply negative” about the idea. “After the seminar Zeldovich called me and told me the content of his work, which I liked instantly. A few days later I called him with my own idea that was a further development of his approach.”

Life had prepared Sakharov to accept Zeldovich’s idea regardless of what had prompted its genesis. He had been thinking about the microphysical vacuum in 1948, before his “exile from Grand science.” Twenty years later he did not simply support Zeldovich. He foresaw how the vacuum in microphysics could be united with gravitation at the most profound level—where gravitation might be rooted.

Zeldovich looked at the quantum fluctuation of the vacuum through a cosmological telescope, characterizing all vacuum life with a single number—its energy density. The “astronomically small” density of vacuum energy would have a noticeable effect only on astronomically large distances.

But Sakharov tried to explain gravity as a characteristic of the continual seething going on in a quantum vacuum. [42] His paradoxical idea was that gravitation—Newton’s gravity known to all schoolchildren—does not exist. Then what does? There is the “elasticity” of the vacuum, which leads to all the known manifestations of gravity—from apples falling to the collapse of stars and the formation of black holes.

But if Sakharov’s paper “did away” with gravitation, then why did John Wheeler, one of the most prominent figures in the theory of gravitation, like it so much? He explained it enthusiastically in his books and articles. [43] Wheeler was interested not in preserving the classical Newton-Einstein theory of gravity at any cost, but in understanding it fully -- that is, in solving the difficult questions that arose from that theory but had no answers. The most important of them was quantum gravity.

Sakharov’s hypothesis opened an unexpectedly new view of the fortress long besieged by theorists. While his colleagues, settled in a military camp around the fortress, considered which catapults and battering rams to use on its thick walls, Sakharov seemed to have discovered an underground passage leading inside the fortress.

He proposed seriously considering the fact that in all points of space-time the vacuum life is pulsing and to take into consideration the effect of that life on the behavior of ordinary, macroscopic Newtonian bodies. The hope was that Einstein’s theory of gravity with its curved space-time continuum, its collapse of stars and expansion of the Universe, would become a consequence of quantum theory. And then out of Einstein’s theory, when gravity is not very strong, Newton’s law of gravity would follow.

The reader, recalling the formulation of that law in high-school textbooks,

                   F = GmM/r²,

may ask, “Well, but where will the value of the gravitational constant G come from?”

Sakharov based his approach on a new constant arising in the complete theory of the microworld, length l, which corresponds to the limit of applicability of geometric concepts known since Euclid. For distances less than l, the usual concepts of space and time must be replaced by some much more profound and less obvious concepts. Sakharov’s theory does not require elucidation of those concepts. It permits theorists to continue their search for the complete theory of elementary particles. However, they are now given a architectural plan of how to unite their search with the search of the complete theory of gravity. And if the searches are successful, then length l will determine the constant G, which governs the fall of an apple and the movement of the planets.

According to Sakharov’s idea, the gravitational constant is the result of the microscopic structure of the vacuum. He called his approach “gravitation as the elasticity of the vacuum.” What does it have in common with the ordinary, familiar elasticity?

Man dealt with elasticity when he made his first bows and arrows. Intuitively, he took into account the coefficients of wood’s elasticity. In more enlightened times elasticities were measured for various materials and encoded in tables. For the preparation of a good bow, however, it is enough to select a material with the appropriate coefficient, without thinking about how elasticity is determined by forces holding the atoms and molecules of the material. The maker of the bow needs to study the molecular structure of matter if he is not satisfied with trial and error—going through all materials—and if he wants to know how the bow will behave on the extreme edge of elasticity, before it breaks.

Just as for calculations on how an object moves in the gravitational field of the Earth or the Sun, it is enough to take the value of G. But in order to learn what will happen to a star as a result of its unlimited compression in its own gravitational field, or how the expansion of the Universe began, knowing the “molecular” structure of the vacuum is indispensable.

 

Theorist-Inventor

 

The mechanism of the formation of baryon asymmetry, invented by Sakharov in 1967, is still the only working hypothesis to explain the observable asymmetry of matter and antimatter. The mechanism he invented to explain the “formation” of gravitation from the characteristics of the microworld is still only an architectural idea. Therefore Sakharov’s colleagues in theoretical physics have to rely on a combination of reason and feeling called intuition in their assessment of his ideas. A variety of intuitions is vitally important for scientific research. But the same variety leads to differences in opinion.

For instance, Sakharov considered Zeldovich’s idea (born by the fence of astronomy), his own starting point, to be one of his best. Zeldovich, apparently, did not think so—in his 1984 scientific autobiography, he does not mention it.

Some sober-minded theorists do not give serious weight to Sakharov’s hypothesis on gravitation as the elasticity of the vacuum. They do not wish to count their chicks before they are hatched. Others consider the idea one of the most significant of Sakharov’s contributions to pure science and the next step after Einstein in discovering the nature of gravitation. [44]

Let us leave the final decision to history. But even before this decision, one can say that the theoretical physicist who in the course of a single year published two such “knockout” ideas as Sakharov did in 1967 has the right to feel proud. Especially if that physicist is also burdened with being the leading designer of thermonuclear weapons.

This astonishing combination leads us to the question that began this chapter: Was Sakharov a theorist or inventor? We can replace the “or” with a hyphen. He used the term 'theorist-inventor' when talking of his military technology work [45], but it applies to his theoretical physics as well.

Theorists differ not only in their strengths of intuition, but in their methods of work. Some start with a general alluring idea and seek a way of concrete formulation. Others begin with a simplified theory of a concrete phenomenon. Still others, with the most general physical theory that they try to apply to the given problem.

In Sakharov’s theoretical physics the inventor is visible. He devises a mechanism that nature could use in controlling its mysteries. An inventive engineer starts with scientifically known elements that he can combine. But an inventive theorist must first invent the very elements he will needs to combine into a theoretical mechanism. The inventiveness can be measured by the level of unusualness of the elements.

We can imagine how the theorist and the inventor collaborated in Sakharov: The theorist saw unusual elements that do not contradict the fundamental laws of nature. The inventor, not abashed by their unusualness, used these elements to construct a working mechanism.

A magnetic field as incorporeal walls of a vessel to hold the blazing lightning of fusion.

The flush of radiation from an A-bomb to compress fuel to produce an H-bomb.

The superweak instability of the proton in the superhot early Universe.

The theorist tells the inventor that all these elements are acceptable in fundamental science. And the inventor figures out how to turn them into a working mechanism.

That may be the way the theorist and inventor in Sakharov collaborated in his creative laboratory. But how did these collaborators regard the completely nonscientific concerns of this lab's chief?