INTERNATIONAL GEOPHYSICAL YEAR

A. Kh. Khrgian, A. S. Britaev

The International Geophysical Year—the largest international undertaking in the entire history of geophysics—has a rather instructive history.

In 1882–1883 the so-called First International Polar Year was organized; its principal aim was to introduce a plan and a single scientific system into the geographical and geophysical investigations of the Arctic, which until then had been scattered and marked above all by a striving for sensational discoveries. In the conduct of the First IPY, besides Russia (which set up observatories on Novaya Zemlya and at the mouth of the Lena), another 10 countries took part. All the materials of the First IPY were published and became accessible to scientists throughout the world.

The Second IPY, carried out in 1932–1933, included observations not only in the Arctic but also in many mountainous regions of the globe that are physically similar to the polar regions. Biological and similar investigations, which had been included in the plan of the First IPY, were relegated to the background in comparison with geophysical ones. The idea of a unified system of geophysical observations, covering the entire globe and not only the polar regions, had finally matured. This idea formed the basis for organizing the new International Geophysical Year, which began on 1 July 1957 and will last 18 months.

Scientists from 56 states are taking part in the conduct of the IGY. Their work is directed by an international body—the Special Committee for the IGY—which, with the participation of numerous scientists from all countries, established the guiding ideas, drew up the plans for the IGY work, and prepared instructions for individual types of observations.

The chairman of the Committee is the English geophysicist S. Chapman; its secretary is the Belgian geophysicist M. Nicolet. In the Soviet Union, preparatory work for the IGY is being carried out by the Interdepartmental Committee for the IGY under the chairmanship of Academician I. P. Bardin.

The aim of the scientific investigations of the IGY is to solve the most important planetary problems of geophysics, which require simultaneous and comparable observations over the whole globe. It is obvious that in many cases the solution of such problems requires the joint application of various methods of investigation—aerological, rocket, radiophysical, magnetic, optical, and many others.

The main sections of the IGY program cover the most important areas of modern geophysics: meteorology, terrestrial magnetism, auroras and night-sky glow, the ionosphere, solar activity, cosmic rays, the determination of longitudes and latitudes, glaciology, oceanography, seismology, and gravitation. But while the instruments and methods

observations in each section are their own, the corresponding investigations are in many cases united by general ideas, about which we shall speak below.

Geophysical measurements during the IGY will be carried out by a dense network of observatories and stations distributed over the entire globe, many of which are being organized specially for the IGY. For the purpose of a more thorough study of the development of geophysical phenomena, the network of observational stations is being thickened along the meridians—\(10^\circ E\), \(75^\circ E\), \(140^\circ E\), \(140^\circ E\) and \(70\)—\(80^\circ W\). In addition, new geophysical observatories will be organized in little-studied and hard-to-reach regions of Africa, Latin America, Central Arctic, and Antarctica. A broad complex of geophysical measurements is to be carried out by numerous expeditions of various countries in the world ocean and in mountainous regions of the globe. The total number of stations at which observations will be carried out according to the unified IGY programs amounts to about 4 thousand.

During the IGY it is planned, in addition to the usual observations, to conduct supplementary measurements according to an intensified program on the so-called “regular world days,” of which two fall at the time of each new moon, and others on days of solar eclipses, increased meteor activity, and so forth. More frequent observations are also scheduled during the “world meteorological periods”—10 days in each quarter, near the equinoxes and solstices—which include the “regular world days” of the month in which that period falls. In addition, more frequent observations will be made during special world intervals of time known as “alerts.” They will begin upon a special signal given from a forecasting center approximately 12 hours before the onset of expected outstanding geophysical phenomena, such, for example, as intense auroras or magnetic and ionospheric storms caused by active solar activity, whose occurrence is difficult or impossible to predict earlier than several days in advance.

A large place in the IGY will be occupied by the largest planetary problem of meteorology and aerology—the problem of the general circulation of the atmosphere. To study it, one must know the direction, velocity, and form of motion of the principal air currents over the entire globe. Among them are the recently discovered so-called “jet streams”—relatively narrow (several hundred km wide) flows of enormous speed (up to 130–190 m/sec), encircling the globe at an altitude between 7 and 13 km. One may hope that during the IGY, in particular, the question of the presumed jet stream “at the edge of the polar night” in the polar regions will be resolved, where large temperature contrasts arise between areas illuminated and not illuminated by the sun.

IGY observations will make it possible not only to determine the kinetic energy of the general circulation (which, according to very approximate estimates, reaches, in the northern hemisphere, \(8.6 \cdot 10^{26}\) ergs in July and \(43.6 \cdot 10^{26}\) ergs in January), but also to resolve the question of the origin of this energy. This highly debated question in geophysics is now interpreted in different ways. Sometimes the sources of energy are sought in tropical latitudes, where the condensation of an enormous quantity of water vapor and the release of latent heat create pressure gradients that can probably set the whole atmospheric machine in motion. Other geophysicists (denying the great significance of processes occurring in the tropical belt) believe that internal energy (including the latent heat of water vapor) is converted into kinetic energy chiefly at the fronts of cyclones of temperate latitudes.

This “engine” of the atmosphere works chiefly in its lower layers (down to 4–5 km) in the winter of the corresponding hemisphere, and it will be very important to ascertain how its action is transmitted to the other hemisphere. One or another solution of this dispute will be of great importance for forecasting air currents, etc.

Of special interest in the scheme of the general circulation is Antarctica, where, probably, an intense cooling of air masses occurs to a degree found nowhere else; these masses settle there and spread out from there in all directions. Soviet radiosonde observations have detected there, at high altitudes, temperatures down to \(-70^\circ\), and equally low temperatures at the Earth’s surface.

The study of the general circulation requires knowledge not only of winds, but also of the pressure, temperature, and humidity of the air in the atmosphere. These are measured chiefly by radiosondes—small instruments lifted by balloons (rubber, polyethylene, etc.) filled with hydrogen or helium to an altitude of 25–30 km. These instruments transmit by radio the values of the measured quantities to the ground. Optical or radar observations of the flight of radiosondes provide information on the direction and speed of the wind at various altitudes. In particular, in the USSR during the IGY about 100 radiosonde stations will be in operation. A special radio-theodolite has been designed for them and is already being used. In 1956 in Payerne (Switzerland) international comparisons of radiosondes were carried out, including a Soviet one, in order to achieve uniformity throughout the world network of radiosonde sounding.

Connected with the problem of the general circulation of the atmosphere is another task of the IGY—at first glance rather remote—the precise determination of time and longitudes by astronomical methods. It is now definitely known that the speed of the Earth’s rotation (which has always served as the standard of time) is not constant. It slowly decreases over the centuries. This slowing is caused by tidal friction (the action of tidal waves), chiefly in shallow seas. In addition, it has become clear that there are fairly regular annual fluctuations in the length of the day. In March the day is longest—by 0.0010 sec. longer than average; in August it is shorter by 0.0012 sec. The maximum and minimum length of the day may sometimes occur later or earlier.

Since the angular momentum of the Earth (rotating from west to east), together with the atmosphere and the sea, is constant, it may be assumed that either the moment of inertia of the Earth as a whole changes—by approximately \(2 \cdot 10^{-8}\) of its value—or the relative angular velocity of the atmosphere changes. In the latter, the prevailing flow is directed, as is known, also toward the east. Both assumptions were considered in 1949–1953 by Belgian and Soviet scientists. The second cause proved the more effective—the transfer of part of the rotational momentum from the Earth to the atmosphere in winter and back in summer. Its contribution explains a change in the rotation rate of \(1.5 \cdot 10^{-8}\), with changes in the wind in the stratosphere above 20 km playing a significant role.

The transfer of angular momentum occurs owing to the force of friction by tangential stresses in the wind flow, depending on the coefficient of turbulence in the near-surface layer of air. Thus these forces, insignificant at first glance, produce large effects.

To achieve still better agreement between theory and observations, it is necessary to take into account the distribution of the actual (and not calculated geostrophic) wind velocities throughout the entire atmosphere. A task on such a scale can be solved only within the framework of the IGY.

A comparison of the longitudes of a number of observatories (12 of which are located in the USSR) on five continents will make it possible finally to resolve the question: are the continents moving relative to one another? Are appreciable deformations of the Earth’s crust taking place in our time? Perhaps, for comparison, it will be necessary in the future to carry out yet another “geophysical year.” In exactly the same way, very precise determinations of gravity will make it possible to find out whether tides and other motions exist in the solid body of the Earth and what its elastic properties are. Repeated many years later, these gravimetric observations will make it possible to verify whether gravity on the Earth is constant.

Another large group of IGY tasks is connected with the problem of the radiation received by the Earth from the Sun—thermal, light, and corpuscular.

Soviet geophysicists proposed including in the IGY program a large network of observations of the radiation and heat balance of the atmosphere. This includes determination of solar (direct and diffuse) radiation, which is of particular interest because in recent years the question of the magnitude of the Sun’s thermal radiation (the so-called solar constant) has been fundamentally reconsidered. The heat exchange of the Earth’s surface and the atmosphere will be studied with the aid of so-called gradient observations in the near-ground layer of air, the methodology of which has been worked out in great detail in the USSR.

Equally interesting is the question of the reflection of solar radiation by the Earth (the magnitude of the albedo). As is known, astronomers have provided a method for determining the albedo of the terrestrial globe in visible rays from the intensity of the so-called ashen light of the Moon, and have discovered noticeable fluctuations of this albedo depending on the weather and cloudiness in the hemisphere turned toward the Moon. Observations of this kind will also be organized during the IGY.

Glaciological observations of the accumulation and melting, advance and retreat of glaciers in mountainous countries are, by their very nature, closely connected with the study of the heat balance and long-term changes in solar radiation and fluctuations of climate. The development of glaciers is promoted both by a lowering of temperature and by an increase in the amount of precipitation. The period of gradual warming observed in Europe and North Asia from approximately the middle of the nineteenth century until 1940 corresponded to a general (though not everywhere uniform) retreat of the glaciers of the Alps, the Caucasus, and so on. The slight lowering of temperatures that has appeared in the last decade may perhaps soon affect the advance of the glaciers of the Caucasus and other mountain ranges. An increase in areas occupied by ice increases the Earth’s albedo and contributes to a lowering of temperatures.

As already stated, observations of the formation and melting of glacier ice are a variety of observations of the heat balance. Of especially great importance for the life of glaciers are the absorption of solar heat and turbulent heat exchange with the atmosphere. The methodology of work of this kind is well known in the USSR, but it has been applied to the study of glaciers only in a few places on the globe.

In 1957–1958, in many countries a large topographic or aerial photogrammetric survey of glaciers will be carried out. It will make it possible to study their development on a large scale and to compare it with what was recorded during the Second IPY (when, in particular, the glacier regions of the Caucasus were studied in detail). In the USSR, in this way, surveys will be made of the glaciers of the Polar Urals, the Suntar-Khayata Range, the Caucasus, the Pamirs, the Tien Shan, and so on. Of special interest are the colossal glaciers of Antarctica, where a layer of ice 2–3 and possibly more km thick lies on ...

in many places on the sea floor (below sea level) and constitutes a significant part of what we call the Antarctic continent. It would be interesting to establish to what extent the high albedo and the low absorption of solar heat by this white massif are responsible for the exceptionally low temperatures and cold winds of Antarctica.

The ultraviolet part of the Sun’s spectrum in the region 2000–2600 Å is wholly absorbed already in the upper layers of the atmosphere, chiefly by oxygen. There it causes dissociation of \(O_2\) molecules into atoms; above 105 km this dissociation is almost complete, while below it is partial. From atoms and molecules of oxygen, ozone is formed, mainly in the layer between 20 and 50 km. Measurement of the ozone content in the atmosphere and of its distribution is of great interest. Although the ozone content is negligible (the equivalent thickness of the ozone layer ranges from 0.15 cm to 0.45 cm, depending on place, time, and meteorological conditions), its significance is exceedingly great. As is known, the arrival at the Earth of the Sun’s ultraviolet rays, active in biological and photochemical respects, in the spectral region from 2900 Å to 3300 Å depends on ozone present in the atmosphere chiefly at altitudes of 20–60 km. Absorption by ozone of long-wave radiation in the spectral region near 9.5 μ noticeably reduces the thermal radiation of the Earth into outer space and is an important factor in the energy balance of the atmosphere.

The total ozone content and its distribution with height also depend on turbulence and the movement of air currents in the troposphere, which opens up the possibility of using ozone observations for forecasting purposes and for studying the general circulation.

In accordance with the recommendations of the ozone commission of the International Meteorological Organization, the principal instrument for measuring ozone is the Dobson-type photoelectric spectrophotometer. In this instrument, ozone is determined by photometering two portions of the ultraviolet spectrum of scattered light coming from the zenith region of a clear sky: one of the portions, with a wavelength of approximately 3110 Å, is absorbed, while the other, with a wavelength of about 3290 Å, is little absorbed by atmospheric ozone. In addition to determining ozone from its absorption in the ultraviolet part of the spectrum (with Dobson instruments and spectrophotometers carried aloft by balloon sondes or rockets), during the IGY electrochemical methods will be tested for measuring the ozone concentration at a given altitude, as well as methods for determining the vertical distribution of ozone from absorption of radiation in the infrared part of the spectrum.

The corpuscular radiation of the Sun is the cause of the occurrence of auroras and of the glow of the night sky, closely connected with the properties of the upper atmosphere. The theory of auroras, proposed at the beginning of the twentieth century by K. Størmer, explains them as the glow of the upper layers of the atmosphere caused by occasional streams of charged particles of solar origin. The latter are concentrated by the Earth’s magnetic field, chiefly in certain annular zones around the northern and southern magnetic poles of the Earth. This theory explains many properties of auroras, for example their great frequency in the belt of geomagnetic latitudes 60–69°, their form as rays, arcs, and draperies, their connection with phenomena on the Sun and with magnetic storms, etc. Proceeding from it, A. P. Nikolsky recently explained the spiral form of certain regions of auroras, as well as the existence of a second zone of frequent auroras, discovered by him, at geomagnetic latitude 78–80°.

According to another theory, proposed by Alfvén, streams of charged particles only create around the Earth a strong electric field, in which a special form of gas discharge arises in the rarefied layers of the atmosphere. All this makes it necessary during the IGY to pay special attention to the form of each aurora, its height and position in space, to its motion (propagation), its change during the night, etc. It will be desirable to repeat attempts to detect the influence of the wind (“ionospheric wind”) on the form and motion of auroras.

Visual and photographic observations of auroras will have to be conducted simultaneously at many points, in order to determine accurately the heights and distances to the auroras. For the same purpose, radar sets with wavelengths of 4–10 m will be used in the Arctic. Similar work will be carried out in the USSR, Norway, Alaska, Scotland, etc. Of particular interest are observations of auroras where they are rare—in tropical latitudes (cases are known when auroras of special intensity, for example on 25.IX 1909, covered almost the whole globe) and on the oceans, where there are few observing stations.

Experiments on the study of atmospheric ionization in the region of auroras are relatively new. The occurrence of auroras is associated with the appearance of anomalous scattering and reflection of radio waves (at oblique incidence) and even with their noticeable absorption. At some observatories this ionization will be studied by measuring the absorption of radio emission from cosmic sources. Rocket observations (such as, for example, the United States proposes to carry out in northern Canada) may provide additional information on ionization and on the magnetic field near auroras.

Very important are studies of the spectra of auroras, which provide almost the only possibility of judging the composition of the upper layers of the atmosphere. With their aid atomic oxygen and nitrogen, hydrogen arising from cosmic-ray protons, nitrogen oxide, etc., have already been detected there. It may be that IGY observations will make it possible to solve the riddle of the enhancement of auroras (especially of the spectral lines with \(\lambda = 6300\) Å and \(\lambda = 3914\) Å) in regions of the atmosphere illuminated by the Sun.

Closely connected with those described above will be organized observations of the glow of the night sky—a phenomenon related to auroras. Its intensity, fluctuations, spectrum, etc., will be studied at high latitudes and in the south of the USSR. It is known that observations of the distribution of the brightness of the night sky make it possible to refine data on the height and thickness of the emitting layers. The spectrum of the night-sky glow also gives important indications of the composition of the upper layers, in particular of the presence in them of hydroxyl OH (discovered precisely in this way), sodium, etc.

The radiation of the Sun in the more remote ultraviolet part of the spectrum \((\lambda < 1300\) Å), the X-ray radiation of the solar corona and, perhaps, the corpuscular radiation of the Sun create the ionosphere—one of the most important objects of IGY research. There is no need to speak of the significance of this object. Let us note only that during the IGY the radiophysical and electrical properties of the ionosphere will be studied in close combination with its other properties—density and temperature, the appearance of meteors and auroras, the motion and even turbulence of the atmosphere.

Observations by approximately 160 ionospheric stations scattered throughout the world will provide, above all, the so-called height–frequency characteristics, supplying detailed information on the concentration of ions, their distribution in the ionospheric layers, etc. Observations made in the Arctic with the onset of the polar night will make it possible to estimate the rate

recombination of ions and the decay of individual ionospheric layers. One of the important tasks of the IGY is the study of the causes of ionization of the upper layers of the atmosphere. Each of the factors (radiations) mentioned above probably makes its own contribution, but the significance of this contribution has not yet been established precisely. These factors, and together with them the properties of the ionosphere, depend noticeably on solar activity, its 11-year period, and its abrupt changes. Ionospheric storms, in which regions of the ionosphere between 100 and 400 km in altitude seem to be filled with irregularly shaped and scattered clouds of ions, are very interesting for research, especially in polar countries. General attention is now being drawn also to inhomogeneities of the ionosphere, observed even on calm, undisturbed days. From their motion, the variable speed of which sometimes reaches 200 m/sec and more, researchers are attempting to determine the wind in the ionosphere and even the presence of tidal waves in it. It is not excluded, however, that this motion is more deeply connected with hydrodynamic processes in the ionosphere, with the emergence in it of turbulent vortices whose formation time is sufficiently short, with special forms of motion of charged clouds in the Earth’s magnetic field, and so on.

Simultaneously with the observation of height-frequency characteristics in the USSR and abroad, great attention will be paid to estimating the absorption of radio waves in the ionosphere. It has a special purpose: determining the effective frequency of collisions of electrons and molecules, and from it the density and temperature in the ionosphere. Fragmentary information of this kind is already available, indicating very high temperatures (up to 4000°) at altitudes of about 400 km. These data, however, need refinement. Reliable information on temperature will make it possible to determine more precisely the height of the atmosphere as a layer, to estimate the rate of dissipation of atmospheric gases into world space, to form an idea of the relationship between the atmosphere and interstellar gas, etc.

Along with the aforementioned types of radiation there are still other, much less studied, ways in which the Sun influences geophysical phenomena. We know that in the Sun’s atmosphere there appear, sometimes in greater and sometimes in lesser numbers, dark sunspots, bright faculae and flocculi, bright chromospheric flares, visible mainly in the lines of hydrogen, and so forth. Their number changes approximately with an 11-year period, and 1958 will be the year of the maximum of this “solar activity.” This means that the number of sunspots will be maximal, and the probability of flares giving enhanced corpuscular and radio emission from the Sun and, probably, also short-wave ultraviolet radiation, will be greatest. The fact that certain properties of the ionosphere (for example, the concentration of ions in it), the Earth’s magnetic field, the number and brightness of polar auroras, and many other phenomena change with an 11-year period indicates a noticeable (although perhaps also “mediated” through a complex chain of phenomena) connection between them and solar activity.

A number of observatories in all countries that have been entrusted with “solar service” will carry out careful observations (including motion-picture photography) of flares, spots, and so forth. The observations will be divided among observatories in such a way as to ensure their continuity over a full twenty-four hours. In particular, in our country regular photometry of chromospheric flares and flocculi will be carried out by the method proposed by the Pulkovo astronomer Glukhov.

Of great interest are observations of the solar corona. Having a very high temperature (over a million degrees), it emits soft X-rays, as well as noticeable radio emission at wavelengths on the order of 1.5 m. The latter is noticeably intensified in the corona over regions of large spots.

Recording fluctuations of solar activity during the IGY will be needed first of all in order to clarify the mechanism of the connection between solar and terrestrial phenomena. Thus, for example, I. S. Astapovich, observing meteor trails, their motion and scattering, found that during periods of high solar activity the winds and turbulence in the upper layers of the atmosphere intensify. It is quite possible that these changes in the general circulation are transmitted from the upper layers of the atmosphere to the lower ones. There is a supposition that it is precisely the general circulation that is affected above all by fluctuations in the Sun’s activity, although it may not be entirely clear what radiation transmits this influence. A further step will be the study of the influence of activity on temperature, precipitation, and other weather phenomena.

Here it should be noted that the study of meteors in the Earth’s atmosphere is an important task both for astronomers and for geophysicists. Meteors ionize the upper layers of the atmosphere, and it is now believed that the sporadic layer \(E_s\) of the ionosphere, which appears from time to time, is connected precisely with meteor ionization. Therefore ionospheric observations can provide certain information about meteor activity. Quite some time ago Levin, Whipple, and others developed methods for estimating the density and temperature of the upper atmosphere from observations of the brightness, velocity, and deceleration of meteors during their flight at altitudes of \(45\)—\(110\) km. These methods have become less widespread than, for example, rocket methods (which are more reliable and systematic), but they have well confirmed the data obtained by other methods.

For observing meteors, radar is now used (usually at frequencies of \(72\) Mc/s), making it possible to detect even very small meteors—down to 8th magnitude, invisible to the naked eye. With its help, daytime meteor streams were discovered that had previously been unknown. During the IGY, 7 observatories observing meteors will operate in the USSR. Of interest to geophysicists are observations of the drift of meteor trails, made visually or with the aid of radar. From them one can judge the wind in the upper atmosphere, for example the multilayer distribution of the wind from the sometimes observed serpentine form of the trail. By following the process of disintegration of the trail into separate clumps and measuring the fading of the radio echo from it, one can judge the diffusion of ions and the turbulence at those altitudes. Geophysicists for a long time neglected this possibility, although recently they have tried to use artificial smoke clouds at altitudes of the order of \(20\) km for a similar purpose.

In the plans for geomagnetism research in the IGY, the main place is given to the study of the variable components of the Earth’s magnetic field. Continuous recording of variations of the magnetic and electric fields will make it possible to establish the connection between the time of existence, intensity, and spatial distribution of electric currents in the ionosphere that cause disturbances of the Earth’s geomagnetic field.

In view of the insufficient study of regions with increased geomagnetic activity, an increase is planned in the number of permanently operating geomagnetic stations, especially in the auroral zone and in the regions of the magnetic and geographic equator. To measure short-period variations of the geomagnetic field, some stations in the Soviet Union are being equipped with apparatus capable of recording changes in field strength of the order of hundredths of a gamma, with periods of pulsations from fractions of a hertz to several hertz. Measurements of electric currents in the ionosphere by means of rockets are planned, including measurements of the equatorial current system that causes magnetic storms at great altitudes.

Seismic observations were not originally included in the IGY program and were added to it in 1955 at the proposal of the Soviet Union. They are important for the IGY because they not only provide a method for studying the structure of the earth’s crust and the ice cover (for example, of Greenland and Antarctica), but also because certain seismic phenomena are closely connected with disturbances of the atmosphere and the seas.

During the IGY, the seismicity of little-studied and difficult-to-access regions—especially Antarctica and the adjacent seas—will be investigated in as much detail as possible. Many earthquakes are known to us there, including destructive ones, for example in the region of the South Sandwich Islands. A Soviet seismic station has already been established at Mirny; other stations have been set up in Antarctica by Australia, New Zealand, the United States, England, and other countries.

In the Arctic there is a seismically active zone running parallel to the great rise of the sea floor known as the Lomonosov Ridge. To observe earthquakes in this region, seismic stations are being established at Tiksi, Tiksi, and Apatity, as well as seven stations in the foreign Arctic. In all, 17 stations are operating in the USSR.

A special place in the work of the IGY is occupied by observations of microseisms—small, almost constantly existing oscillations of the earth’s crust with a period of 3–9 seconds and an amplitude of up to 100 μ. It has been assumed that microseisms arise either in regions of strong surf along rocky continental coasts, or in regions of cold fronts that create abrupt fluctuations in atmospheric pressure. However, it is most probable that their sources are located on the ocean floor. Where strong cyclonic storms pass, sea waves driven by winds of different directions and interfering with one another form a kind of standing wave. The variable pressure on the ocean floor at that point creates microseismic oscillations. By determining the regions from which such microseisms come, one can trace the movement of a cyclone. Although the theory of the phenomenon is complex, its practical interest is very great. For such observations the Soviet Union is setting up two groups of stations—on the Pacific Ocean at Petropavlovsk-Kamchatsky, Yuzhno-Sakhalinsk, and Vladivostok, and in the west at Barentsburg, Murmansk, and Vyborg. India, Japan, the United States, and other countries will also organize microseismic observations.

Within the limits of a short article it is impossible to give an idea even of all the main concepts that underlie the organization of the IGY. But there is no doubt that the course of the scientific work connected with the IGY will now be widely covered in the scientific press, all the more so because the organizational period of the IGY has already ended, and questions of methodology and of the placement of the network of observing observatories are gradually receding into the background in comparison with the questions of the physical investigation of the Earth.