ON THE THIRTIETH ANNIVERSARY OF SOVIET PHYSICS*

SOVIET PHYSICISTS AND PRE-REVOLUTIONARY PHYSICS IN RUSSIA

A. F. Ioffe

At the very beginning of the twentieth century, sharp changes occurred in physics. The era encompassing the period 1895–1912 is characterized by the establishment of the fundamental principles of atomic physics. The atomic structure of electricity was proved, the charge and mass of the electron were determined, the atomic structure of matter was established, the number of atoms in a given body and the number of electrons contained in each atom were measured, as was the arrangement of atoms in a crystal. Brownian motion gave to the statistical conception of the thermal motion of molecules the same reality that had previously belonged only to directly observed macroscopic phenomena.

Persistent attempts to give a theory of radiant energy led Planck to the necessity of introducing a new universal constant—the quantum of action. It became clear that in the nature of light, besides its long-known wave properties, there is another, quantum aspect. Decisive in this direction was Einstein’s work, which showed that the basic facts in the field of the photoelectric effect and fluorescence testify to the quantum structure of the electromagnetic waves themselves, and not only of the phenomena of emission and absorption of light. Finally, Einstein’s theory of relativity constituted one of the most important directions in the physics of this epoch.

The basis of the physics of the prewar years was formed by two tasks—to learn the structure of the atom and to understand the physical meaning of quanta. Each new fact connected with atomic physics was used to construct a new hypothesis of the atom. One such hypothesis—the planetary atom—was proposed at this time by O. D. Khvolson. But only from 1912, when Rutherford’s idea appeared of electrons rotating around

* The series of articles devoted to surveys of the achievements of Soviet physics over 30 years is not concluded in the present issue, but will be continued in 1948.

of the positive nucleus, and, following this, its further development in Bohr’s quantum model—this problem found its solution. In the same year, 1912, the discovery of the interference of X-rays in crystals revealed the atomic structure of crystals and laid the foundation for X-ray spectroscopy. In Moseley’s works these spectra were connected with the structure of the atom.

The structure of atoms and crystals, the X-ray and optical spectra of atoms, and the riddle of superconductivity—these were what physics lived on in the period before the First World War.

What did we have at that time?

When I began working in Petersburg (this was in 1906), the traditions of the nineteenth century, and even rather of its middle, of the school of F. F. Petrushevsky were still strong there. The teaching of physics in higher education proceeded along the line of so-called measurement physics—methods of measurement as the basis of exact knowledge.

In all the higher schools of St. Petersburg the first course was devoted to the description of measuring instruments, and only from the second year were laws from the fields of heat, electricity, magnetism, optics, and acoustics presented. Theoretical—or, more precisely, mathematical—physics at the university was reduced to the phenomenological formulation of laws and the solution of partial differential equations from the fields of heat conduction and electrostatics.

The professors and teachers of physics in the higher schools possessed extensive erudition, but paid little attention to creative activity. The scientific works of those who remained at the university were often reduced to repetitions of published works.

The brilliant, but also predominantly phenomenological, lectures of O. D. Khvolson were well attended, but did not create an impulse toward scientific creativity. Such, too, was his remarkable multivolume course in physics, which fully and didactically clearly encompassed the whole body of physical knowledge of that time and was translated into a number of foreign languages.

Scientific work in the physical institute of Petersburg University was at a low level. Its state may be illustrated by the admonition which, after the death of the principal head of the physical institute, I. I. Borgman, was given to me and to D. S. Rozhdestvensky, as his successors in the direction of scientific work: “Of course, J. J. Thomson or Rutherford create new paths in science, but an ordinary physicist cannot invent some new problems; therefore the task of the physical institute is to raise the knowledge and experimental skill of its collaborators.”

However, at the same time in Petersburg D. S. Rozhdestvensky was carrying on his work; he had created the “hook method” and had already completed his remarkable investigation of dispersion in sodium vapor.

Another brilliant physicist of that time in Petersburg was D. A. Rozhanskii, whose dissertation (a study of the spark) attracted universal attention by the freshness of its physical ideas.

An equally vivid phenomenon was the dissertation of V. F. Mitkevich on the mechanism of the voltaic arc, where the role of electrons was demonstrated with particular clarity. In the field of optics, interest was aroused by the work of S. I. Pokrovskii on interference and of A. L. Gershun on optotechnology.

The interesting studies of N. A. Gezehus and N. N. Georgievskii on electrification by friction have not been sufficiently appreciated.

Next, permit me to name myself: having returned to Petersburg from Munich, where I had worked with Röntgen, I set myself the goal of experimentally proving the existence of electrons and light quanta, the obviousness of which had been clear to me from the very beginning. Along with this I continued the investigations, begun in Munich, of the electrical properties of crystals.

A great influence on all the Petersburg physicists, and in particular on me, was exerted by Paul Sigismund Ehrenfest, whose extraordinary creative and public activity raised scientific interests and scientific criticism to a great height.

One must not forget that in the same Petersburg University, in the chemistry department, there was a powerful center of physical and chemical thought headed by the great Mendeleev.

One of the most important hindrances for physicists of that time was the university system of master’s examinations, which had to be passed in order to gain access to scientific work at the university. This ugly system was a stumbling block which, over the course of many years in Petersburg, not a single physicist overcame. The mathematicians made no distinction between scholars with mathematical interests and physicists for whom mathematics was an auxiliary method in their work, and not the essence of their activity.

Such was the physics of the capital, St. Petersburg.

Matters stood differently in Moscow. Here there arose the first Russian school of physicists, the school of Petr Nikolaevich Lebedev, from which a number of leading scholars emerged. Lebedev’s school, in its subject matter and scientific organization, represented the most gratifying phenomenon of pre-revolutionary physics. It could not, however, develop fully under the conditions of tsarist Russia. I remember well the years 1907–1909, when I had occasion to visit Lebedev in Moscow. His scientific laboratories were housed in the basement of the physical institute, because the main floors were intended for other purposes. Yet even from the basement he had to leave when Moscow University, protesting against the dismissal of progressive professors, came into conflict with the reactionary tsarist government. A considerable number of professors left the university; Lebedev left together with them. Although he tried to organize a laboratory in a small private apartment, at that time it was not possible to make a real large institute out of it.

could not grow; he did not live to see the completion of the construction of the new institute.

Lebedev was joined by his comrade, the brilliant physicist and teacher Aleksandr Aleksandrovich Eikhenvald, author of the classic investigation of the magnetic field of a moving charge and of displacement currents, who greatly contributed to raising the scientific level of Moscow physicists, and by Lebedev’s closest pupil—Petr Petrovich Lazarev, who organized scientific work in the field of biophysics and geophysics.

From Lebedev’s laboratory there emerged a number of interesting lines of work: first of all, the remarkable works of Lebedev himself on the light pressure on solids and gases, the works of Lazarev and Timiryazev on the kinetic theory of gases, the acoustic measurements of V. D. Zernov and others, and the work in the field of radio waves by V. K. Arkad’ev and V. I. Romanov. From this same school came S. I. Vavilov, B. V. Il’in, and many others. In the provinces, individual major scholars worked, among them such figures as Gol’dgamer and Ul’yanin in Kazan, Rozhanskii and Kravets in Kharkov, Kasterin in Odessa, Kosonogov and Shiller in Kiev, and also Umov and Sokolov in Moscow.

And in Petersburg, besides the university, there were individual major physicists: Gezekhus, Egorov, Gershun, Mitkevich, the Smirnov brothers; but they did not create schools. At the Academy of Sciences there worked one of the founders of seismometry, B. B. Golitsyn, and later also A. N. Krylov.

In the past, Russian physics could name a series of outstanding names, beginning with Lomonosov, Petrov, Lenz, and ending with Stoletov and Mendeleev, as well as such technical achievements as Petrov’s voltaic arc, Jacobi’s electroplating, Yablochkov’s candle, Lodygin’s incandescent lamps, and Popov’s radio signaling.

Before the October Revolution we had many educated physicists, but the only large scientific school was the school of Petr Nikolaevich Lebedev, who had by that time died. He was replaced by P. P. Lazarev. Only just before the revolution, in Leningrad, did our group stand out, which included P. L. Kapitsa, Ya. I. Frenkel, N. N. Semenov, P. I. Lukirskii, Ya. G. Dorfman, and several others. From this school the Physico-Technical Institute later grew.

There existed a physical society, where physicists gathered and where, in addition to scientific discussions, sharp political conflicts not infrequently arose. The Petersburg Physical Society numbered a little more than 100 members, and the Moscow one about the same number, but a considerable portion of the two overlapped; moreover, among the members of the society there were amateurs of physical knowledge who were not engaged in scientific work. I think it would be correct to estimate the number of scholarly physicists of that time at approximately 100 persons.

We had the journal of the Physico-Chemical Society, consisting of two parts: physical and chemical. In the physical part there were two sections—original papers and reviews, but all this was on a very small scale—9 slim issues a year.

Training personnel at Petersburg University was determined by the program of state examinations, which had been drawn up by officials who had taken the place of progressive Moscow professors. I had occasion to take part in state examinations at Petersburg University and at the Higher Courses for Women. I often asked the question: “Why does the needle of an ammeter deflect when a current passes?” For the most part the question caused perplexity, and sometimes the answer was: “The electric needle, because of this, deflects.” Physics and technology were not linked in university teaching, and were even set in opposition to one another.

The Great October Revolution sharply changed the fate of Russian physics. Already in 1918 Soviet physics began to be organized—along paths different from those followed by prerevolutionary physics. The Soviet government created large scientific centers, of which there had been almost none before the revolution. (The Physical Laboratory of the Academy, headed by B. B. Golitsyn, was devoted to seismology; the physical laboratory was small.)

In the course of 1918 alone three large institutes were formed. In Moscow—the Institute of Physics and Biophysics: after the death of P. N. Lebedev the institute intended for him was headed by P. P. Lazarev and acquired a strong bias toward biology, but also engaged in molecular physics, optics, geophysics, and other branches of physics. In Leningrad, in October 1918, the Physico-Technical Institute was organized and soon, there too, the Optical Institute, which later grew into the largest institute in the world, serving as the scientific base of the optical industry of the Soviet Union.

Each of these three institutes set itself the goal both of developing physics itself and of linking it with the corresponding branches of life. The Institute of Physics and Biophysics, naturally, gravitated toward medicine. The Physico-Technical Institute—toward electrical engineering, power engineering, metallurgy. The Optical Institute set and solved the task of creating in the Soviet Union an industry of optical glass and optical instruments. In addition, each institute became a large school in which personnel of a new type began to grow.

In the first years of Soviet power the Soviet Union was cut off from abroad, and our scientific work was conducted in isolation from world science. The principal directions and scientific interests, as later became clear, were the same as abroad. What was new was their connection with the tasks of building the first socialist society in the world.

The war found physics in a period of stormy flowering of the Bohr atom and of the Laue method. From these positions we also began to develop our work. D. S. Rozhdestvensky organized an atomic commission, whose task was to develop the theory of the Bohr atom and draw from it all the necessary conclusions. For the comprehensive use of the Laue method

was organized at the Physico-Technical Institute as a molecular commission. The work of the first was based on Bohr’s atom, that of the second on the Laue method.

In the atomic commission there arose Rozhdestvensky’s advanced magnetic theory of spectral doublets. The molecular commission led to the discovery of the mechanism of plastic deformations and textures in the cold working of metals.

At the beginning of 1921 D. S. Rozhdestvensky and I were asked to restore scientific ties with foreign countries, and for this purpose, as well as to purchase equipment, we were sent abroad. A. N. Krylov and P. L. Kapitsa went with us. We were received with extraordinary benevolence, and the report on the results of our work during that period caused a sensation. No one expected that in a “wild country of Bolsheviks” science could develop and produce results, in some cases going beyond what had been achieved in Western countries. In the very first years Soviet physics took a worthy place in world science.

The purpose of our trip was to provide the new institutes with equipment, because in those years it was impossible to expect equipment from our factories. And this second task was fulfilled by me and D. S. Rozhdestvensky. Our institutes received excellent equipment, so abundant that when a whole series of institutes separated from the Physico-Technical Institute, many of them continued to use part of this equipment.

After our return the institutes grew stronger. Both institutes obtained independent buildings. On February 4, 1923, our institute moved from the Polytechnic Institute into its own specially equipped building, and at approximately the same time the Optical Institute began to move from the university.

Looking back over this entire period, I consider it a great merit of Soviet physicists that, instead of a random selection of topics, sometimes brought from abroad, Soviet physicists began to develop their own scientific directions. Many of the problems posed here interested foreign laboratories and in some cases received considerable development there; but it is important to note that our subject matter was built on the foundation that had been laid at the very beginning of the Soviet period, under conditions of complete isolation from Western science.

I shall begin with the Physico-Technical Institute, which is close to me. Here the problem of the strength and plastic deformation of crystals and of their electrical properties received broad development. These questions also began to be intensively studied in the West—in England, Germany, and the USA. Some of our conclusions became the subject of a lively discussion; not all of them have fully retained their significance, but nevertheless the leading role belonged to us. Here, together with Ivan Vasilievich Obreimov, an ingenious method for obtaining single crystals was developed. At that time many foreign laboratories, having turned to the study of single-

crystals, used Obreimov’s method, and sometimes his crystals as well. Obreimov’s work on cleavage forces in mica, and later on a new type of twinning formed during plastic deformation, was also of great importance.

The appearance of a number of other directions, having their roots in Soviet physics and spreading to laboratories throughout the world, also belongs to this time.

Nikolai Nikolaevich Semenov, already in his student years, sought to combine physics with chemistry. Beginning with the study of electric fields by the heated-probe method, he used these data to improve the technique for measuring ionization and dissociation energies. Having created the theory of the so-called thermal breakdown of dielectrics, he transferred the basic ideas of this theory to chemical phenomena and arrived at the theory of chain reactions, which opened a new stage in chemical kinetics and yielded a whole series of most important practical results.

Petr Ivanovich Lukirskii laid the beginning of an important direction in the field of electronics and the photoelectric effect. Having created the spherical-condenser method, he was the first to determine the distribution of electron velocities in a metal. For a long time Petr Ivanovich was also scientific consultant to the laboratory of our principal plant in this field, “Svetlana.”

Aleksandr Alekseevich Lebedev, at the Optical Institute, by his careful investigations of the processes of glass annealing, contributed to a considerable degree to the creation of the optical-glass industry, sharing this part with Grebenshchikov and Kachalov.

Among the new directions in the field of molecular physics, great importance was acquired by the X-ray textures of matter, which characterize changes in the crystal lattice during deformations and cold working. In 1918, M. V. Kirpicheva and I published the first radiographs of deformed crystals.

In Moscow this question was studied by N. E. Uspenskii, formerly also a collaborator of the Physico-Technical Institute, and in Leningrad by Selyakov and Kurdyumov. It is often forgotten that the basic conception of radiographs as the result of the reflection of X-rays from atomic planes in the crystal lattice was put forward by the remarkable Russian physicist-crystallographer Yuri Viktorovich Wulff, who unfortunately died early, before Bragg and, of course, independently of him. At that time Yu. V. Wulff was also a collaborator of the Physico-Technical Institute.

D. V. Skobeltsyn, by placing a Wilson chamber in a magnetic field, was able to measure electron velocities. By this method he studied the spectra of gamma rays and discovered the fast electrons of cosmic rays.

An outstanding representative of Soviet science of the first period was the prematurely deceased professor of the Physico-Mechanical Faculty Aleksandr Aleksandrovich Fridman, author of the theory of relativity with negative curvature, which acquired such important

significance. A. A. Fridman created an advanced school of dynamical meteorology, from which came Kochin, Kibel, Izvekov, and others.

To this same period belongs also the stream of new ideas introduced into physics by Ya. I. Frenkel. Among them especially notable are the idea of the displacement of free sites, of the viscosity of liquids, of the motion of charges in solids, of the surface tension of metals, and of the quantum electronic states of conduction electrons in metals. Especially great importance was acquired by Frenkel’s conception of the transfer of current and diffusion by means of the displacement of empty sites in a completely filled medium. This idea was extended by Frenkel to the displacement within a crystal of excited states (which received the name of excitons) of atomic electrons.

A new current in the study of the photoelectric effect was introduced by I. E. Tamm, who established that the external photoelectric effect has a dual origin—surface and volume. He also showed wherein lies the fundamental force retaining electrons in a metal. General recognition was gained by L. D. Landau’s work on the diamagnetic and paramagnetic properties of electrons in a metal.

Of great importance was the transfer of the Physical Institute of the Academy of Sciences, headed by S. I. Vavilov, to Moscow. Here there joined it the scientific school of Leonid Isaakovich Mandelstam. Both for Mandelstam himself and for his school (G. S. Landsberg, S. E. Khaikin, A. A. Andronov, M. A. Leontovich) a characteristic feature was the combination of profound theory with brilliant experiments. It considerably deepened our knowledge in the field of molecular physics through the study of the fine mechanism of viscosity, friction, and the dispersion of sound.

All Soviet physicists know well that it is precisely Mandelstam and Landsberg who have the honor of the first observation and correct explanation of the combination scattering of light, which is called the Raman effect. The same Mandelstam, together with the inseparably associated with him Nikolai Dmitrievich Papaleksi, laid the foundation of the theory of nonlinear oscillations and its various applications. Another kind of combination scattering was later discovered and studied by E. F. Gross.

V. K. Arkad’ev and his collaborators studied the magnetic properties of iron at high frequencies. Although the explanation of magnetic spectra could not be fully preserved, these works yielded many valuable results, including a phenomenological theory of the magnetic properties of ferromagnets. A. A. Glagoleva-Arkad’eva and M. A. Levitskaya were pioneers in the production of electromagnetic waves overlapping the infrared spectrum. In the “mass radiator” Glagoleva-Arkad’eva found an original and ingenious way of solving an extremely difficult technical problem.

At the Optical Institute, under the direction of Dmitrii Sergeevich Rozhdestvenskii, a strong school of spectroscopists grew up: S. E. Frish, V. M. Chulanovskii, V. K. Prokof’ev, E. F. Gross, and others.

The idea of Rozhdestvensky concerning the magnetic origin of doublets had a great influence on the development of the theory of spectra. His method of hooks was widely used in the study of dispersion. From his school came the works of A. N. Terenin, which initiated a new approach to the study of the mechanism of chemical reactions and the luminescence of gases. Under the influence of D. S. Rozhdestvensky, optotechnics, illuminating engineering, and the industry of optical glass and optical instruments developed. Unfortunately, the significance of Rozhdestvensky’s scientific and organizational activity was for a time underestimated.

At the Institute of Physics and Biophysics, Petr Petrovich Lazarev created a physico-chemical theory of the transmission of nervous excitation and established the laws of adaptation of sight and hearing. He also carried out an investigation of the Kursk magnetic anomaly.

To this same time also belongs the beginning of work in the field of technical physics, which first unfolded under Soviet power. Alongside the successful activity of the Optical Institute, in the Physico-Technical Institute a laboratory of electrophysics was created by the late Academician Chernyshev, a laboratory of acoustics by Nikolai Nikolaevich Andreev, and a laboratory of heat engineering by Mikhail Viktorovich Kirpichev, where a method for modeling thermal installations was developed. Here, too, N. N. Davidenkov’s school on the mechanical properties of metals developed.

The first decade (from 1919 to 1928) in the development of Soviet physics thus created a whole series of new scientific directions, brought forth large schools that made Soviet physics a full-fledged member of world science, linked it with the progress of Soviet technology, and included it in the vigorous flowering of socialist culture. From this time onward, new physico-technical institutes began to grow in Tomsk, Kharkov, Dnepropetrovsk, Sverdlovsk, and Gorky.

The following period is better known; therefore I shall confine myself only to a brief enumeration of newly created scientific trends.

The study of amorphous bodies, their mechanical and electrical properties, the connections between these and other properties, and the physical investigation of polymers and their specific features were developed by P. P. Kobeko and A. P. Aleksandrov.

In ferromagnetism and in the influence of anisotropy on the phenomenon of ferromagnetism we have the works of N. S. Akulov and E. I. Kondorsky at Moscow State University; the works of Dorfman, Kikoin, and Vonsovsky in Sverdlovsk introduced new features into questions of the theory of magnetism. Akulov’s collaborators in Moscow, and Yanus and Khalileev in Sverdlovsk, developed new methods of magnetic defectoscopy.

Investigations of nonlinear oscillations by Mandelstam and Papaleksi created a new field in the theory of oscillations and led to the construction of electrical machines of parametric resonance. A new

By these methods N. M. Krylov and N. N. Bogolyubov developed the theory of nonlinear oscillations.

The luminescence of liquids is a field created entirely by Sergei Ivanovich Vavilov, V. L. Levshin, and their collaborators. To them also belongs the establishment of the laws of phosphor decay and their use for important practical purposes.

Together with a number of collaborators, in recent years I have been engaged at the Physico-Technical Institute with semiconductors, their physical nature and practical use, hoping in this way to solve the general problem of the electrical properties of solids. Considerable clarity has been brought into this field.

The Kiev (Goldman) and Odessa (Kirillov) schools of physicists worked in the same direction. Kikoin and Noskov discovered a new photomagnetic effect in semiconductors. In the works of D. I. Blokhintsev, V. P. Zhuze, B. I. Davydov, A. V. Ioffe, and S. I. Pekar, the nature of the rectifying properties of boundary layers was elucidated. Rectifiers, photoelements, and thermoelements were improved many times over, and new types of them were created. Semiconductor alloys of metals and liquid electronic semiconductors were studied for the first time.

An unexpected discovery in the classical domain of the electromagnetic theory of light was made by Cherenkov in the laboratory of S. I. Vavilov and under his direction. Cherenkov discovered the directional radiation of fast secondary electrons, knocked out by gamma rays, moving in a substance with velocities exceeding the phase velocity of light. The theory of this phenomenon, given by Frank and Tamm, completely explained all the details of the observed phenomena and was also confirmed by direct experiments with fast electrons carried out in the USA.

A major event in Soviet physics was Pyotr Leonidovich Kapitsa’s discovery of the phenomenon of the superfluidity of helium-II (the so-called superconductivity), which led to Landau and Peshkov’s subsequent discovery of second sound in the same helium-II.

In addition to the great fundamental significance of this new, striking manifestation of quantum laws discovered by Kapitsa, his investigations open the way to a further approach to absolute-zero temperatures. Kapitsa’s turbodecompressor and vortex expansion of gases created a new technique for low temperatures. Of no small importance also is the elucidation by Landau and Shalnikov of the nature of the intermediate state between superconductivity and normal conductivity. In Kharkov, interesting results were obtained by the cryogenic laboratory under Lazarev’s direction.

An extensive school for the study of the mechanical properties of solids was created during the years of Soviet power by V. D. Kuznetsov in Tomsk. The five-volume monograph published by him covers both Soviet and foreign work in this field. Particularly great successes have been achieved, in addition to Kuznetsov, by his collaborators Bolshanin and Kudryavtseva.

Prominent among these are Soviet works on X-ray diffraction patterns and phase transformations in metals, headed by G. V. Kurdyumov and S. T. Konobeevsky. The investigations of N. N. Davidenkov’s school (Vitman, Fridman, Yakutovich, Shevandin) on impact strength, of A. V. Stepanov on plasticity, of A. P. Komar on diffusion, and of M. O. Kornfeld on the hardness of liquids acquired great significance. S. A. Vekshinsky proposed and carried out a new method for obtaining alloys of continuously varying composition by sublimating metals in a vacuum from different centers.

Another leading Soviet school embraces the theory of electrical insulation. The works of P. P. Kobeko, B. M. Vul, and others initiated new scientific trends and led to new technical materials: escapon, polystyrene, and barium titanate. I. V. Kurchatov, together with P. P. Kobeko and B. V. Kurchatov, discovered a new physical phenomenon, an electrical analogue of ferromagnetism, which they named ferroelectricity. A further development of this discovery is represented by B. M. Vul’s investigations of barium titanates.

In the field of electronic phenomena, major advances were made by the works of V. E. Lashkarev, L. A. Artsimovich, and L. A. Kubetsky, who first realized a photoelectric tube with multiple amplification by means of secondary emission. New types of photocells with a barrier layer were developed by B. T. Kolomiets and Gelman. New methods of mathematical physics in the field of electrical phenomena and electron optics were created by G. A. Grinberg.

In acoustics there grew up the school of N. N. Andreev, to which belonged B. P. Konstantinov, A. A. Kharkevich, A. I. Belov, and A. V. Rimsky-Korsakov, who greatly developed the acoustics of musical instruments. D. I. Blokhintsev developed the theory of the acoustics of moving media.

After the death of D. S. Rozhdestvensky, the world’s largest Optical Institute developed under the direction of S. I. Vavilov and occupied a leading place in the solution of a number of optical problems. S. I. Vavilov created a new method for observing and measuring extremely weak light and, with its aid, clearly demonstrated the existence of photons. Here Brumberg produced a reflecting ultraviolet microscope; here A. A. Gershun developed the theory of the light field; the investigations of T. P. Kravets and M. A. Sevostyanova on the photographic process were carried out; new astronomical instruments were created by D. D. Maksutov; A. I. Tudorovsky’s work on the calculation of optical systems was widely expanded; Linnik’s ingenious interference instruments were developed; and A. A. Lebedev constructed an electron microscope. During the Patriotic War the Optical Institute supplied the Soviet Army with domestic optics.

At the Institute of Chemical Physics, the theory of explosions and combustion received a new foundation under the leadership of N. N. Semyonov and his collaborators B. Ya. Zeldovich and Yu. B. Khariton.

L. D. Landau gave a general thermodynamic theory of phase transitions.

We began to concern ourselves with the problem of the atomic nucleus somewhat late, but nevertheless we had a number of serious successes—in the work of I. V. Kurchatov on nuclear isomerism; in the investigations of A. I. Alikhanov, who, combining the method of magnetic spectroscopy with coincidence counters, measured a number of spectra and established the properties of beta decay of radioactive nuclei; in the work of Artsimovich, Leipunsky, Sinyelnikov, and others on the scattering of fast electrons; and of Frank and Dobrotin—on neutrons. Flërov and Petrzhak discovered the spontaneous fission of uranium nuclei. New data of great fundamental importance were also obtained in the study of cosmic rays by D. V. Skobeltsyn and V. I. Veksler in the Pamirs, and by Alikhanian and Alikhanov on Alagez. The phenomenon of the disintegration of atomic nuclei under the influence of cosmic rays was discovered by Zhdanov by means of the thick-layer photographic plates first developed by L. V. Mysovsky at the Radium Institute. V. I. Veksler is responsible for the idea of the synchrotron, which opens new paths for obtaining particles of ultra-high energies.

The basic lines of quantum mechanics were not created here; however, the method developed by Fock became the leading one for the problem of atomic electrons. Our present conception of protons and neutrons as the sole elements of the atomic nucleus belongs to D. D. Ivanenko. The ideas of I. E. Tamm were of great importance for the development of our conceptions of nuclear forces.

Ideas on the thermal motion of the elements of the nucleus and on the stretching of uranium nuclei were first put forward by Ya. I. Frenkel. A quantitative theory of cosmic showers was given by L. D. Landau.

The successes of Soviet physicists are especially great on the borders with neighboring scientific fields. Besides the kinetics of chemical reactions, which is one of the most brilliant extensions of physics beyond its own limits, another bridge from physics to chemistry has also been thrown down among us. Terenin and Kondrat’ev, on the basis of spectral analysis, solved a number of important chemical problems. The participation of physicists (Aleksandrov, Kobenko, Bresler, Zhurkov) in the study of high-molecular compounds opened new paths in this field and exerted an influence on English and American scientific thought.

On questions of the strength of engineering materials, N. N. Davidenkov and his collaborators, developing my ideas on the transition temperature from the brittle to the plastic state, gave new methods for estimating the impact strength of steels.

Aleksandrov and Zhurkov created the statistical theory of brittle strength, and Stepanov—the theory of the plastic fracture of crystals. Klassen-Neklyudova studied the new phenomenon of jump-like deformation. The idea of surface cracks as a source of failure, and of the influence of adsorption of surface-active substances, was widely used by P. A. Rebinder, who created an improved—

stemmed methods of drilling oil wells, improved methods of processing metals, the replacement of cooling liquids by aqueous solutions, etc.

Crystallography in the hands of A. V. Shubnikov yielded new, remarkable results in the field of the structure and growth of crystals and the theory of symmetry. Here new piezoelectrics, anisotropic materials of increased strength, artificial rubies, and the like were obtained.

One cannot fail to mention new directions in agrophysics, striving to make use of physics for agriculture. This task was posed by the collectivization of agriculture, under the conditions of which it became possible, on a large scale, to influence the physical conditions of the harvest.

Questions of the heat balance, structure, moisture, and thermal conductivity of soils, of the influence of the light regime on plant life and, in particular, of the role of individual parts of the spectrum at various stages of growth—all these are problems requiring modern methods of physical research for their solution. The Physico-Agronomic Institute succeeded in achieving some successes in such important practical problems as combating drought and frost, strengthening and greening sandy deserts, draining soil, and in solving a whole series of problems lying on the border between physics and agriculture. The Institute also developed a large series of measuring instruments for agrotechnical work.

Seismometry, created by B. B. Golitsyn, received broad development in our country at the Seismological Institute under the direction of P. M. Nikiforov. In this institute, approaches were also developed toward construction and blasting work and seismic prospecting.

O. Yu. Schmidt organized a new center of geophysical research, embracing the entire range of questions of the physics of the atmosphere and the solid shell of the earth, the problems of the origin of the stellar world and the formation of continents. Here various methods of geophysical prospecting for mineral deposits were developed: seismic, magnetic, electrical, and thermal. I. A. Kibel belongs the first scientifically grounded theory of weather forecasting. Continuing the work of the outstanding scientist A. A. Fridman, who died early, Kibel created a strong school of Soviet meteorologists.

V. V. Shuleikin, as a result of a systematic study of phenomena observed at sea, created a new scientific field—the physics of the sea. In particular, he discovered and studied infrasounds with a frequency on the order of 10 hertz, caused by wind on sea waves. Of great interest is his theory of the influence of the oceans on climate and his theory of atmospheric seiches.

In the field of radio engineering, new ways of using phase phenomena for measuring distances were realized by N. D. Papaleksi and L. I. Mandelstam. Of great importance for the development of radiophysics

had the works of B. A. Vvedensky and D. A. Rozhansky. The latter, together with Yu. B. Kobzarev, created methods of radiolocation earlier than they appeared abroad. G. V. Braude is responsible for an original method of television.

Soviet physics contributed much in the days of the Patriotic War. Dozens of works were adopted for use at the front, and some of them acquired great significance.

In order to assess correctly the advances that have taken place in physics over the 30 years of Soviet power, it is necessary to contrast the most important conditions that determined scientific work in pre-revolutionary Russia with their state at the present time.

Instead of a hundred physicists, among whom there were no more than 20 doctors of science, we have no fewer than 2000 scholars, including several hundred doctors. Instead of 30–40 scientific works a year, we now find annually up to 300 investigations of major scientific significance. In the physical journals alone, in condensed form, scientific output amounts to no fewer than 300 sheets a year, whereas before the revolution, in 9 issues of the journal, detailed articles barely filled 30 sheets. The number of scientific monographs and popular publications has increased tens of times.

Before the revolution, scientific work was carried on, alongside teaching, in poorly equipped university laboratories by a professor of physics and two or three of his assistants. Only in Moscow and Petersburg Universities were there physical institutes with a dozen teachers, and in the Academy of Sciences a physical laboratory with 3–5 staff members.

Now, in addition to three excellently equipped physical institutes of the Academy of Sciences of the USSR, with a total staff exceeding 1000 people, scientific work has also been developed in a number of academic and non-academic Moscow institutes, in the physico-technical institutes of Sverdlovsk, Kharkov, and Gorky, and in the institutes and laboratories of the republican academies in Kiev, Baku, Yerevan, Tashkent, Alma-Ata, and Minsk.

However, the scale of scientific work in the field of physics and its applications is by no means limited to this. Physical work is being conducted in hundreds of industrial research institutes, some of which, such as, for example, the Optical, Electrotechnical, and Metallurgical institutes, are powerful centers of physical research. The physics departments of universities and higher technical schools put forward and solve a considerable number of purely physical questions. Special mention should be made of the broad development of the diverse problems of technical physics, which were practically entirely absent in tsarist Russia. The annual Stalin Prizes, prizes of the Academy of Sciences, socialist competition, and the attention of the broad public to the achievements of science are powerful stimuli of scientific creativity.

The growth of physical instrument-making set out in the plan for the new five-year period is already having an effect on the equipment of our laboratories.

Before the revolution, all the cadres of physicists, both for higher and for secondary schools, were supplied by 10 universities with faculties of physics and mathematics. Now secondary schools are provided for by a system of pedagogical higher educational institutions. In a number of universities independent physics faculties have been established, training research physicists; to these must be added the physics-mechanics and physics-technical faculties of Leningrad and Moscow.

Before the revolution, the universities retained a few students who had completed the course “for preparation for the title of professor” and sent them abroad for this purpose. Now in our higher schools and research institutes hundreds of postgraduate students and doctoral candidates improve their knowledge and acquire experience in scientific work. The defense of a master’s and especially of a doctoral dissertation was a rare event in pre-revolutionary Russia. Now many dozens of candidate and doctoral dissertations are defended every year.

The growth of scientific personnel is not limited to postgraduate study. In our country there are up to 1000 research institutes, where creative scientific work is widely developed, where problems of science are discussed at seminars and scientific councils. All this creates favorable conditions for the scientific growth of staff members.

Congresses of physicists and annual conferences: on polymers and spectroscopy, magnetism and luminescence, on semiconductors and on acoustics, etc., etc., not only make it possible to assess the scope of the scientific activity of our laboratories, but also serve as a school for physicists. As a typical example I shall point out that more than 60 physical and chemical institutes and laboratories take part in conferences on polymers. Popular journals, books, and lectures attract broad strata of working people, awaken their thought and inventiveness, and arouse interest in physical knowledge.

However vivid the facts and quantitative comparisons of the present and the past cited above may be, they do not give an idea of the main thing that the October Revolution gave—of the new paths of development of Soviet science, of its qualitative superiority over bourgeois science.

The history of Soviet science is inseparably connected with the general flourishing of culture and the national economy. Under the conditions of socialist society, science acquires the new content of one of the instruments of the struggle for the happiness of our people and of all humanity. All his knowledge, all his experience, the Soviet scientist gives to the people. Together with the people he defends his Motherland in the years of war and creates advanced technology in the period of industrialization.

From a side occupation of teachers of the higher school, scientific activity has become the affair of an army of researchers put forward by the working people. The gap between pure and applied science is disappearing; they merge in the unified plan of the socialist state.

Scattered scientific interests are replaced by a broad, prospective plan, concentrating the best forces on the central leading problems and at the same time ensuring the development of all fields of knowledge. Nourished by its own roots, Soviet science is blazing new trails; reverence for bourgeois science is disappearing, and patriotic self-awareness is growing.

The narrow confines of individual scientific disciplines are being overlapped by the development of boundary fields linking mathematics with astronomy, physics and chemistry; physics with chemistry, geology, astronomy, biology, engineering, and agriculture, and so on.

The individual works of scientists are growing into the collective creativity of institutes and academies that advance science and solve the most important problems of the national economy.

Criticism and self-criticism, socialist competition, the advanced scientific methodology of dialectical materialism, ideological orientation, and the guidance and active assistance of the Party and the government create the soil on which talents flourish, and discoveries and inventions grow and multiply.

Such is Soviet science, and such is Soviet physics.

In 30 years it has encompassed the entire range from mechanics to nuclear physics, almost without gaps, and has gone far beyond its own limits into the fields of chemistry, biology, electrical engineering, heat engineering, agronomy, geophysics, the study of the sea, and geology. Across this entire broad front, Soviet physicists have blazed new trails and created new scientific directions and scientific schools that have gained recognition throughout the world. I have attempted to characterize the most important of these schools in the present essay. In the era of the Patriotic War, physicists showed themselves to be worthy sons of their homeland.

A characteristic feature of Soviet physics is the close connection between theory and practice, a clear Marxist methodology, the planned development of the areas of physics most important for the national economy, and the collective character of scientific creativity. The favorable conditions created by the era of the rapid construction of socialist industry and agriculture have led to the powerful growth of our science. The working class and the collective-farm peasantry have brought forth from their midst thousands of talented, highly qualified physicists. The volume and scope of scientific creativity have increased many times over; its ideological level has been raised high in comparison with the pre-revolutionary past. Year after year, the Stalin Prizes cannot encompass all the worthy candidates put forward by the country.