A message about one scientific achievement of the 20th century. The most important achievements of science at the end of the 19th and beginning of the 20th centuries

In the 20th century, natural sciences developed unusually quickly: physics, chemistry, astronomy, biology, geology and many others. Science has given a lot of ideas and developments; production, in turn, has given science complex and advanced devices and instruments. All this together stimulated the development of science. The consequence of this extremely fruitful combination of science and production was the achievement of their high development, which led to the emergence of the third scientific and technological revolution in the mid-20th century.

Physics

In the 20th century, a lot was done in the field of studying the structure of matter. Famous English physicist Ernest Rutherford(1871 - 1937) experimentally established that atoms have nuclei in which almost all their mass is concentrated, and developed a planetary model of the structure of the atom (1911). This was probably the last (or perhaps the first and last) model of the atom that is relatively easy to imagine. According to the planetary model, electrons move around the stationary nucleus of an atom (like planets around the Sun) and at the same time, according to the laws of classical electrodynamics, they continuously emit electromagnetic energy. However, Rutherford's planetary model of the atom was unable to explain why electrons, moving around the nucleus in circular orbits and, therefore, constantly experiencing acceleration and therefore constantly emitting and losing their kinetic energy, do not approach the nucleus and do not fall on its surface.

Model of the atom proposed by a famous Danish physicist Niels Henrik David Bohr (1885 - 1962), although it was based on Rutherford’s planetary model, it did not contain the indicated contradiction. For this, Bohr introduced postulates that now bear his name, according to which atoms have so-called stationary orbits along which electrons move without emitting, while radiation occurs only in those cases when they move from one stationary orbit to another (in this case, change in atomic energy). Bohr's brilliant conjecture (or idea), despite its internal inconsistency, connects

The understanding of Newton's classical mechanics, used to explain the motion of electrons and the quantum restrictions on the motion of electrons that are unacceptable from its standpoint, has nevertheless found experimental confirmation.

A huge achievement in physics was the creation of quantum (wave) mechanics, according to which microparticles have a dual corpuscular-wave nature. Quantum mechanics - one of the main sections of quantum theory - the most general physical theory, not only gave new, revolutionary ideas about microparticles, but also made it possible to explain many properties of macroscopic bodies.

The prerequisites for the development of quantum mechanics were the work on the creation of quantum concepts of Planck, Einstein and Bohr. In 1924, French physicist Louis de Broglie put forward the idea of the dual corpuscular-wave nature of not only electromagnetic radiation (photons), but also other microparticles, thereby laying the foundation for quantum mechanics. Somewhat later, experiments were carried out in which diffraction of microparticles was observed - scattering of a flow of microparticles (the flow of microparticles bending around various obstacles), indicating their wave properties, which was an experimental confirmation of de Broglie's hypothesis.

In 1925, one of the creators of quantum mechanics was a Swiss theoretical physicist Wolfgang Pauli(1900 - 1958) formulated the so-called exclusion principle - a fundamental law of nature, according to which neither an atom nor a molecule can have two electrons in the same state. Austrian theoretical physicist Erwin Schrödinger(1887 - 1961) developed wave mechanics in 1926 and formulated its basic equation. German theoretical physicist Werner Heisenberg(1901 - 1976) formulated the uncertainty principle (1927), according to which the values of the coordinates and momenta of microparticles cannot be named simultaneously with a high degree of accuracy. English physicist Paul Dirac laid the foundations of quantum electrodynamics (1929) and quantum theory of gravity, developed a relativistic theory of electron motion, on the basis of which he predicted (1931) the existence of the positron - the first antiparticle (a particle in all respects similar to its “double”, in this case the electron, but different from it sign of electric charge, magnetic moment and some other characteristics), annihilation and birth of pairs. In 1932, American physicist Carl David Anderson discovered the electron's antiparticle, the positron, in cosmic rays, and in 1936, the muon.

Back in 1896, the French physicist Pierre Curie(1859 - 1906) together with his wife Marie Skłodowska-Curie(1867 - 1934) and French physicist Antoine Henri Becquerel(1852 - 1908) discovered radioactivity and radioactive transformations of heavy elements. In 1934 French physics couple Irene(daughter of P. Curie and M. Sklodowska-Curie) and Frederic Joliot-Curie(1900 - 1958) discovered artificial radioactivity. Discovery by an English physicist James Chadwick(1891 - 1974) in 1932 the neutron led to modern, proton-neutron ideas about the structure of atomic nuclei.

The development of nuclear physics and the study of nuclear reactions was greatly facilitated by the creation of charged particle accelerators. The number of known elementary particles has increased many times. Many of them are able to exist only for a negligible time. It turned out that elementary particles can undergo mutual transformations, that they are not elementary at all. According to a successful comparison by the famous Soviet physicist V.L. Ginzburg, everything happens as if we are dealing with an “infinite nesting doll”: you discover one elementary particle, and behind it “an even more elementary one,” and so on without end. It can probably be said that most modern physicists recognize the existence of special fundamental particles - quarks and corresponding antiparticles - antiquarks. It is assumed that quarks have a fractional electric charge. Quarks have not been detected experimentally, but perhaps because they cannot exist in a free, unbound state.

It is impossible not to note the enormous impact of physics on other sciences and on the development of technology. Due to the fact that this topic is truly inexhaustible, we will refer only to those sciences whose very name indicates the influence of physics: astro-, geo- and biophysics, physical chemistry and some others.

The rapid development of nuclear physics made it possible in 1939 - 1945. take decisive steps in liberating nuclear energy. At first, this outstanding scientific discovery was used for military purposes to create nuclear and thermonuclear weapons, and then for peaceful purposes: the first nuclear power plant was built in the Soviet Union and began operating in 1954. Subsequently, dozens of powerful nuclear power plants were built in many countries around the world, where a significant portion of electricity is generated.

Based on the physics of crystals, the theory of semiconductors, which has enormous practical significance, X-ray diffraction analysis, as well as the electron microscope and the method of tagged atoms, which played a major role in the development of many fields of technology, and, perhaps, especially metallurgy, were created. Electronics owes a lot to physics and its achievements - the science of the interaction of electrons with electromagnetic fields and methods for creating electronic devices, which, in turn, is of decisive importance for many areas of technology, in particular for electronic computers.

Albert Einstein. Theory of relativity

Experiments of an American physicist Albert Abraham Michelson(1852 - 1931) by determining the speed of light (including the famous “Michelson experiment”) showed its independence from the movement of the Earth. It turned out that the speed of light in empty space is always constant and, strange as it may seem, at first glance, independent of the movement of the source or receiver of light.

Michelson's discovery could not be explained from the standpoint of the physical theories existing at that time. Firstly, from Galileo’s principle of relativity it follows that if two coordinate systems move relative to each other rectilinearly and uniformly, i.e., in the language of classical mechanics, the systems are inertial, then all the laws of nature will be the same for them. Moreover, no matter how many such systems there are (two or much more), there is no way to determine in which of them the speed can be considered as absolute. Secondly, in accordance with classical mechanics, the velocities of inertial systems can be transformed one relative to another, i.e., knowing the speed of a body (material point) in one inertial system, one can determine the speed of this body in another inertial system, and the values of the velocities of this body in different inertial coordinate systems are different.

Obviously, the second position contradicts Michelson's experiment, according to which, we repeat, light has a constant speed regardless of the movement of the source or receiver of light, i.e., regardless of in which inertial coordinate systems the counting is carried out.

This contradiction was resolved with the help of the theory of relativity - a physical theory, the basic laws of which were established by A. Einstein in 1905 (private or special theory of relativity) and in 1907-1916. (general theory of relativity).

Great theoretical physicist Albert Einstein(1879 - 1955) was born in Germany (Ulm). From the age of 14 he lived in Switzerland with his family. He studied at the Zurich Polytechnic Institute and, graduating in 1900, taught at schools in the cities of Schafhausen and Winterthur. In 1902, he managed to get a position as an expert at the Federal Patent Office in Bern, which suited him more financially. The years of work in the bureau (from 1902 to 1909) were years of very fruitful scientific activity for Einstein. During this time, he created the special theory of relativity, gave a mathematical theory of Brownian motion, which, by the way, remained unexplained for about 80 years, developed the quantum concept of light, he carried out research in statistical physics and a number of other works.

Only in 1909 did Einstein’s already enormous scientific achievements become widely known, were appreciated (far from fully), and he was elected professor at the University of Zurich, and in 1911 - at the German University in Prague. In 1912, Einstein was elected head of the department at the Zurich Polytechnic Institute and returned to Zurich. In 1913, Einstein was elected a member of the Prussian and Bavarian Academies of Sciences, and he moved to Berlin, where he lived until 1933, being the director of the Institute of Physics and a professor at the University of Berlin. During this period of time, he created the general theory of relativity (most likely completed, since he began working on it in 1907), developed the quantum theory of light, and carried out a number of other studies. In 1921, Einstein was awarded the Nobel Prize for his work in the field of theoretical physics, especially for the discovery of the laws of the photoelectric effect (a phenomenon involving the release of electrons from a solid or liquid as a result of the action of electromagnetic radiation).

In 1933, due to attacks on him by the ideologists of German fascism as a public figure - a fighter against war and a Jew, Einstein left Germany, and later, as a sign of protest against fascism, he refused membership in the German Academy of Sciences. Einstein spent the entire final part of his life in Princeton (USA), working at the Princeton Institute for Basic Research.

The theory of relativity rests on the fact that the concepts of space and time, in contrast to Newtonian mechanics, are not absolute. Space and time, according to Einstein, are organically connected with matter and with each other. We can say that the task of the theory of relativity comes down to determining the laws of four-dimensional space, three coordinates of which are the coordinates of a three-dimensional volume (x, y, z), and the fourth coordinate is time (t).

The constancy of the speed of light, proven by experience, forces us to abandon the concept of absolute time.

The speed of light, equal, as we know, to a huge value - 300 thousand km/s, is the limit. The speed of any object cannot be higher.

In 1905, Einstein combined the concepts of space and time. Eleven years later, he was able to show that Newtonian gravity is a manifestation of this bold unification in the sense that Newtonian gravity means the presence of curvature in a single space-time manifold.

Einstein came to the conclusion that real space is non-Euclidean, that in the presence of bodies creating gravitational fields, the quantitative characteristics of space and time become different than in the absence of bodies and the fields they create. So, for example, the sum of the angles of a triangle is greater than π, time flows more slowly. Einstein gave a physical interpretation of N.I.’s theory. Lobachevsky. The foundations of the general theory of relativity are expressed in the equation of the gravitational field obtained by Einstein.

If the special theory of relativity was not only confirmed experimentally, during the creation and operation of microparticle accelerators and nuclear reactors, but has already become a necessary tool for the corresponding calculations, then with the general theory of relativity the situation is different.

The lag in the field of experimental verification of general relativity is due to both the smallness of the effects accessible to observation on Earth and within the Solar system, and the comparative inaccuracy of the corresponding astronomical methods.

The founder of quantum theory is the famous German physicist, member of the Berlin Academy of Sciences, Honorary Member of the USSR Academy of Sciences Max Planck (1858-1947). Planck studied at the Universities of Munich and Berlin, listening to lectures by Helmholtz, Kirchhoff and other prominent scientists. He worked mainly in Kiel and Berlin. Planck's main works, which inscribed his name in the history of science, relate to the theory of thermal radiation.

The decisive step was taken by Planck in 1900, when he proposed a new (completely inconsistent with classical ideas) approach: to consider the energy of electromagnetic radiation as a discrete value that can only be transmitted in separate, albeit small, portions (quanta). As such a portion (quantum) of energy, Planck proposed the value E = hv, erg is a portion (quantum) of energy of electromagnetic radiation, sec -1 is the frequency of radiation, h=6.62*10 -27 erg*sec - a constant, which later received the name Planck’s constant or Planck’s quantum of action.

Planck's guess turned out to be extremely successful, or better yet, brilliant. Planck not only managed to obtain an equation for thermal radiation that corresponded to experience, but his ideas became the basis of quantum theory - one of the most comprehensive physical theories, which now includes quantum mechanics, quantum statistics, and quantum field theory.

Structure of matter. Quantum theory

Atomic physics as an independent science arose on the basis of the discovery of the electron and radioactive radiation. The electron - a negatively charged microparticle with a mass of only about 9 * 10 -28 g - one of the main structural elements of matter - was discovered by the famous English physicist Joseph John Thomson (1856 - 1940), member (1884) and

President (1915 - 1920) of the Royal Society of London, foreign honorary member of the USSR Academy of Sciences.

In 1896, French physicists Pierre Curie, Marie Sklodowska-Curie and A. Becquerel first discovered the radioactivity of uranium salts. The phenomenon of radioactivity, which finally refuted the idea of the indivisibility (intransformability) of the atom, consists in the spontaneous transformation of unstable atomic nuclei into the nuclei of other elements (other atoms), which occurs as a result of nuclear radiation. It also turned out (this was extremely important for medicine) that the rays discovered by Becquerel could penetrate deep into matter and therefore were a means of obtaining photographs, for example, of human internal organs.

Pierre Curie and his wife Marie Skłodowska-Curie also dealt with issues of radioactivity and other elements. They discovered new elements in 1898: polonium and radium. It was found that radioactive radiation can be of two types: either the nucleus of a radioactive element emits an alpha particle (the nucleus of a helium atom with a positive charge 2e) or a beta particle (an electron with a negative charge -e). In both cases, an atom of a radioactive element turns into an atom of another element (this depends both on the original radioactive substance and on the type of radioactive radiation).

In radioactivity research, the joint work of the famous English physicist Ernest Rutherford and the famous English chemist was of great importance Frederica Soddy (1877 - 1956), carried out in 1899-1907. They used uranium, thorium and actinium as initial radioactive elements. So-called isotopes were discovered, i.e. varieties of the same chemical element that have the same chemical properties and occupy the same place in Mendeleev’s periodic table of elements, but differ in the mass of atoms.

E. Rutherford, member of the Royal Society of London, honorary member of the USSR Academy of Sciences, was born in 1871 in New Zealand into the family of a small farmer, the fourth of 12 children. Graduated from the University of New Zealand (Christchurch). In 1894 he moved to England and was accepted into the Cavendish Laboratory at the University of Cambridge, where he began research under the direction of J. J. Thomson. Rutherford spent most of his life (with some interruptions while working at the Universities of Montreal and Manchester) in Cambridge, being director of the Cavendish Laboratory from 1919. He trained a large number of highly qualified physicists.

Based on experiments, Rutherford came to the conclusion that atoms contain nuclei - positively charged microparticles, the size of which (approximately 10 -12 cm) is very small compared to the size of atoms (about 10 -8 cm), but the mass of an atom is almost completely concentrated in its core,

An α particle abruptly changes the direction of its path when it hits a nucleus.

The discovery of atomic nuclei was a very major event in the development of atomic physics. But Rutherford's planetary model of the atom turned out to be incompatible with Maxwell's electrodynamics.

Bohr's next model of the atom was based on quantum theory. One of the greatest physicists of the 20th century. - Dane Niels Bohr(1885 - 1962) was born and graduated from the University of Copenhagen. He worked at the University of Cambridge under the leadership of J. J. Thomson and at the University of Manchester under the leadership of Rutherford. In 1916 he was elected head of the department of theoretical physics at the University of Copenhagen, from 1920 and until the end of his life he headed the Institute of Theoretical Physics that he created in Copenhagen, which now bears his name. In 1943, during the occupation of Denmark by the Nazis, Bohr, seeing that reprisals were being prepared against him, with the help of the Resistance organization, moved by boat to Sweden, and then moved to the United States. After the end of the war he returned to Copenhagen.

The model of the atom created by Bohr was based on Rutherford’s planetary model of the atom and on the quantum theory of atomic structure developed by him himself in 1913.

In 1924, one of the greatest events in the history of physics occurred: the French physicist Louis de Broglie(1892 - 1983) put forward the idea of the wave properties of matter, thereby laying the foundation for quantum mechanics. He argued that wave properties, along with corpuscular ones, are inherent in all types of matter: electrons, protons, molecules and even macroscopic bodies.

The further development of quantum mechanics - this new unusually fruitful direction - was mainly achieved in the late 20s - early 30s through the works of famous physicists - Max Born (Germany, 1882 - 1970), Werner Heisenberg (Germany, 1901 - 1976), Dirac fields (England, b. 1902), Erwin Schrödinger (Austria, 1887 - 1961), as well as Wolfgang Pauli (Switzerland, 1900 - 1958), Enrico Fermi (Italy, 1901 - 1954), Vladimir Alexandrovich Fok (1898 - 1974) and many others.

Separate sections of quantum mechanics included atomic physics, the theory of radiation, the theory of the structure of molecules (which is sometimes called quantum chemistry), the theory of solids, the theory of interaction of elementary particles, the theory of the structure of the atomic nucleus, etc.

In quantum mechanics there is a so-called uncertainty relation established by Heisenberg. The mathematical expression of the uncertainty relationship is very simple:

where Δx is the inaccuracy in determining the electron coordinate; Δp - inaccuracy in determining the electron momentum; h is Planck's constant.

From this expression it is clear that it is impossible to simultaneously determine the position of an electron in space and its momentum. Indeed, if Δx is very small, i.e. the position of the electron in space is known with a high degree of accuracy, then Δp is relatively large and, consequently, the magnitude of the momentum can be calculated with such a low degree of accuracy that in practice it has to be considered as an unknown quantity. And vice versa, if Δp is small and therefore the electron momentum is known, then Δx is large; and, therefore, the position of the electron in space is unknown. Of course, the uncertainty principle is valid for any particle, not just the electron.

From the point of view of classical mechanics, the uncertainty relation is absurd. From the standpoint of “common sense” it seems, at least, very strange, and it is impossible to imagine how all this could “really” be.

But we must not forget that we live in the macrocosm, in the world of large bodies that we see with our own eyes (or even with the help of a microscope) and can measure their size, mass, speed of movement and much more. On the contrary, the microworld is invisible to us; we cannot directly measure either the size of the electron or its energy. In order to better imagine the phenomena of the microworld, we always want to build an adequate mechanical model, and this has sometimes been possible to do. Recall, for example, Rutherford's planetary model of the atom. It is to a certain extent similar to the Solar System, which in this case is a mechanical model for us. Therefore, the planetary model of the atom is easily perceived.

But for most objects and phenomena of the microworld it is impossible to build a mechanical model, and therefore the provisions of quantum mechanics are often perceived with great difficulty. Try, for example, to build a mechanical model of an electron that has particle-wave properties, or a mechanical model that explains why it is impossible to simultaneously determine its mass and momentum for an electron. That is why in these cases the emphasis should be on “understand” and not on “imagine.”

One of the leading Soviet physicists said well on this matter Lev Davidovich Landau(1908 - 1968): “The greatest achievement of human genius is that man can understand things which he can no longer imagine.”

To what has been said, we can add that the uncertainty principle (uncertainty relation) is a fundamental position of quantum mechanics.

Famous English physicist, student of Rutherford James Chadwick discovered the neutron, a neutral particle that enters the nucleus of an atom along with protons and played such an important role in the creation of ways to use nuclear energy.

After the discovery of the electron, proton, photon and, finally, in 1932, the neutron, the existence of a large number of new elementary particles was established - a total of about 350. Among them: the positron, as the antiparticle of the electron; mesons - unstable microparticles (these include μ-mesons, π ± -mesons and heavier π 0 -mesons); various types of hyperons - unstable microparticles with masses greater than the mass of a neutron; resonance particles having an extremely short lifetime (about 10 -22 ... 10 -24 s); a neutrino-stable, electrically chargeless particle, apparently with zero rest mass, with almost incredible permeability; antineutrino - antiparticle of a neutrino, differing from a neutrino in the sign of the lepton charge, etc.

Currently, elementary particles are understood as the “building blocks” of the Universe, from which everything that we know in nature can be built. The world of elementary particles is complex, and the theory of elementary particles is at the beginning of its development. Perhaps the coming years will bring a lot of new things into it.

Chemistry

Chemistry belongs to the natural sciences. In its sphere are the transformations of chemical substances, which are a collection of identical atoms (elements) and more complex substances consisting of identical molecules. Modern chemistry is closely related to other natural sciences, primarily physics. Therefore, such sciences as physical chemistry, biochemistry, geochemistry, etc. appeared and were widely developed. Chemistry is also divided into inorganic, the subject of which is substances whose molecules do not contain carbon, and organic, the scope of which includes substances whose molecules necessarily contain carbon.

From the first steps of its development, chemistry is closely connected with production. Long before the new era, processes such as metallurgy, textile dyeing, leather dressing and others, which had long been considered chemical, arose.

Back in the second half of the 17th century. famous English physicist and chemist R. Boyle gave probably the first scientific definition of a chemical element, laid the foundation for chemical analysis, and showed the inconsistency of alchemy.

In 1748 M. V. Lomonosov experimentally discovered the law of conservation of mass in chemical reactions. Somewhat later, but independently of it, the same law established A. Lavoisier - one of the founders of chemistry.

An extremely important role in the development of chemistry belongs to the English scientist John Dalton (1766 - 1844) - the creator, as they sometimes say now, of chemical atomism. In 1803, he established the law of multiple ratios, introduced the concept of “atomic weight” and determined its values for some elements, taking the atomic weight of the lightest element, hydrogen, as one. Italian scientist Amadeo Avogadro(1776 - 1856) and French scientist Andre Marie Ampere(1775 - 1836) at the beginning of the 19th century. introduced the idea of a molecule consisting of atoms connected to each other by chemical forces. Then the Swedish scientist Jens Jacob Berzelius(1779 - 1848), who did a lot as an experimental chemist, compiled a more accurate table of atomic weights than Dalton managed to do, which already included 46 elements, and introduced the signs of the elements that are currently used. He discovered new elements unknown to him: cesium (Cs), selenium (Se), thorium (Th). Berzelius also created the electrochemical theory, on the basis of which he built a classification of elements and compounds.

French chemist Charles Frederic Gerard(1816 - 1856) in the mid-19th century. proposed the so-called theory of types, which was a system of classification of organic compounds, and also introduced the idea of homologous series - groups of related organic compounds, which was important in the classification of not only organic compounds, but also the reactions inherent in them.

In the middle of the 19th century. another important discovery was made. English chemist Edward Frankland(1825 - 1899) introduced the concept of valence - the ability of an atom of a given chemical element to combine with other atoms. He also introduced the term “valency”. It turned out that atoms of one substance can combine with atoms of other substances only in strictly defined proportions. The reactivity (valency) of hydrogen was taken as the unit of valence. For example, the combination of carbon with hydrogen - methane 2 CH 4 indicates that carbon is tetravalent.

Famous Russian chemist Alexander Mikhailovich Butlerov(1828 - 1886) in 1861 created the theory of the chemical structure of matter. According to this theory, the chemical properties of a substance are determined by its composition and the order (nature) of the bonds of atoms in the molecule of the substance.

As described in detail above, the outstanding Russian chemist D. I. Mendeleev in 1869 he discovered the periodic law of chemical elements and created the Periodic System of Elements - a table in which the then known 63 chemical elements were distributed into groups and periods in accordance with their properties (he attached a special role to atomic weight and valency). It is necessary to especially note Mendeleev’s versatility as a scientist (over 500 scientific papers he wrote dealt with issues of the theory of solutions, chemical technology, physics, metrology, meteorology, agriculture, economics and many others) and his constant interest in issues of industry, primarily chemical. The name of D.I. Mendeleev is firmly entrenched in the history of science.

Name German Ivanovich Hess (1802 - 1850), a Russian scientist of German origin, is well known for his work in the field of thermochemistry - a science that deals with the thermal effects accompanying chemical reactions. Hess established the law that bears his name, from which it follows that when a circular chemical process is carried out, when the reacting chemical substances participating in the reaction are in the original composition at the end of the process, the total thermal effect of the reaction is zero.

Hess's research in the field of thermochemistry was continued by the French scientist Pierre Eugene Marcelin Berthelot(1827 - 1907), who also worked on issues of organic chemistry, chemical kinetics and some others, Danish chemist Hans Peter Thomsen(1826 - 1909) and Russian scientists Nikolai Nikolaevich Beketov(1827 - 1911), who also worked in the field of metal chemistry.

Second half of the 19th century. was marked by work in the field of electrochemistry, as a result of which the Swedish physical chemist Svanet by August Arrhenius(1859 - 1927) the theory of electrolytic dissociation was formulated. At the same time, the doctrine of solutions - mixtures of two or more substances evenly distributed in a solvent in the form of atoms, ions or molecules - was further developed. Almost all liquids are solutions. This, by the way, is the “secret” of the so-called “magnetic fluids”. In this regard, the names of D. should be mentioned. I. Mendeleev, the Dutch physical chemist Van't Hoffe, the Russian physical chemist N. S. Kurnakov.

In the 19th century The effect of catalysts, which are so important for practice - substances that increase the rate of a reaction, but, in the end, do not take part in it, was clarified. At the end of the 19th century. K. Guldberg And P. Waage the law of mass action was discovered, according to which the rate of a chemical reaction is proportional to the concentration of the substances involved in powers equal to their stoichiometric numbers in the equation of the reaction in question. From the law of mass action it follows that reactions always occur in both directions (from left to right and from right to left). When chemical equilibrium is reached, the reaction continues, but the composition of the reacting mixture remains (for a given temperature) unchanged. Consequently, chemical equilibrium is dynamic in nature.

For the 20th century Particularly characteristic is the high pace of development of chemical science, which is closely related to major achievements in physics, and the rapid growth of the chemical industry.

It was found that the atomic number of a chemical element in the periodic table is numerically equal, as mentioned above, to the charge of the atomic nucleus of the element, or, what is the same, to the number of electrons in the shell of the atom. Thus, as the atomic number of an element increases, the number of external electrons in an atom increases, and this happens with the periodic repetition of similar external electronic structures. This explains the periodicity of the chemical, as well as many physical properties of elements established by Mendeleev.

The development of quantum mechanics has made it possible to establish the nature of the chemical bond - the interaction of atoms, which determines their combination into molecules and crystals. In general, it should be said that the development of chemistry in the 20th century. based on the achievements of physics, especially in the field of the structure of matter.

In the 20th century The chemical industry developed at an unprecedented rate. At first, chemical technology was primarily based on isolating simpler substances needed for practical use from complex natural substances. For example, metals from ores, various salts from more complex compounds. The production of so-called intermediate substances (sulfuric, hydrochloric and nitric acids, ammonia, alkalis, soda, etc.) for the production of final chemical products has been and is widely used. Then, the synthesis of complex chemical products, including those that have no analogues in nature, such as ultra-pure, ultra-strong, heat-resistant, heat-resistant, semiconductor, etc., became increasingly used. The production of many of them requires the creation of very high or very low temperatures, high pressure, electric and magnetic fields and other, as they are often called, extreme conditions.

The production and use of polymers - substances whose molecules consist of a very large number of repeating structures - have become widespread; The molecular weight of polymers can reach many millions. Polymers are divided into natural (biopolymers: proteins, nucleic acids, etc.), from which the cells of living organisms are built, and synthetic, for example polyethylene, polyamides, epoxy resins, etc. Polymers are the basis for the production of plastics, chemical fibers and many other important materials. substance practices. It should be noted that the research in the field of chain reactions by the outstanding Soviet chemist and physicist is of particular importance for the development of polymer chemistry (as well as for many other branches of the chemical industry). N. N. Semenova and famous American scientist S. Hinshelwood.

Both inorganic chemical technology, in particular the production of chemical fertilizers for agriculture, and organic chemical technology, such as the refining of oil, natural gas and coal, the production of dyes and medicines, as well as the production of synthetic polymers mentioned above, have received widespread development.

Although the first polymer products (phenoplasts - plastics used as corrosion-resistant structural materials, and rubber-like substances) were obtained at the end of the 19th century, the basic ideas about the nature and properties of polymers were formed not so long ago - approximately by the beginning of the 40s20 V. It was by this time that the idea of the synthesis of polymeric substances was also formed. It became clear that one of the main conditions for the successful production of polymers is a very high purity of the starting substances (monomers), since the presence of even a very small amount of foreign molecules (contaminants) can interrupt the polymerization process and stop the growth of polymer molecules.

By the beginning of the 40s of the 20th century. All the main polymer materials were created (polystyrene, polyvinyl chloride, polyamides and polyesters, polyacrylates and organic glass), the production of which in subsequent years acquired a very large scale. Then, in the 30s, under the leadership of academician Sergei Vasilievich Lebedev(1874 - 1934) large-scale production of synthetic rubber was created. Around the same time, organosilicon polymers were discovered, an important property of which is good dielectric characteristics, and a technology for their production was developed; the main credit for this belongs to the academician Kuzma Andrianovich Andrianov(1904 - 1978). Development of N.N. Semenov's theory of chain reactions is associated with the mechanism of radical polymerization. Free radicals in chemistry are understood as very reactive kinetically independent particles (atoms or atomic groups) with unpaired electrons, for example H, CH 3, C 6 H 5.

Later it was found that the properties of polymers are determined not only by the chemical composition and size of the molecules, but also to a large extent by the structure of the molecular chain. For example, it turned out that the difference between the properties of synthetic rubber and natural rubber is determined not by the chemical composition and size of the molecules, but by their structure. On this occasion, the famous Soviet chemist Valentin Alekseevich Kargin(1907 - 1969) wrote: “If in the first period of the development of polymer chemistry the main attention was paid to the size and chemical composition of the resulting molecules, then over time the structure of the molecular chain began to attract increasing interest. After all, the molecular groups included in it can be arranged in different ways relative to each other, forming a large number of isomeric forms. So, for example, if any side groups are attached to the chain of main valences, then they can be located regularly or irregularly, on one or on different sides of the chain molecule, and can form different configurations. Consequently, with the same composition, the chemical structure of the chain can be very different, and this greatly affects the properties of the polymers.”

In addition to polymers needed for practical use in very large quantities, such as plastics, fibers, films, rubbers and rubbers, which are now produced on a huge scale, polymers that have unique, sometimes completely unexpected properties, have also become extremely important, for example: the ability to exist at high temperatures, while maintaining the necessary strength, having semiconductor properties or electrical conductivity, photosensitivity, physiological activity, etc. New broad prospects are opening up, for example, obtaining artificial blood based on physiologically active polymers, obtaining dyes, surfactants, electrolytes and many others.

As can be seen from the above, the production and widespread use of polymers with a variety of properties is one of the largest achievements of chemistry in the mid-20th century.

Biology

The term "biology" was introduced in 1802. J.B. Lamarck And G. R. Treviranus independently of each other.

The first studies that can be considered as the origins of modern biology date back to ancient times. It is known that the ancient Greek scientist and doctor Hippocrates, who lived in the 5th - 4th centuries. BC, is considered the famous physician of Ancient Greece, the father of scientific medicine and at the same time a keen observer of biological phenomena. An ancient Greek scientist who lived more than half a century later Aristotle, whose interests covered all the branches of knowledge that existed in his time, perhaps, most of all, in modern terms, dealt with issues of biology. In any case, he showed great interest in descriptive biology, the study of plants and animals, their systematics, physiology and embryology.

Outstanding ancient Roman scientist and physician Galen(approx. 130 - 200) is known mainly as an outstanding physician. In his classic work “On the Parts of the Human Body,” an anatomical and physiological description of the human body as a whole was given for the first time. Galen summarized the ideas about the human body that had been made before him, laid the foundations for diagnosing diseases and their treatment, and introduced animal experiments into practice.

In the further development of biology, much attention was paid to various medicinal herbs. As can be seen from the above, at the dawn of its development, biology was especially closely connected with medicine. In the 16th century and the first half of the 17th century. multi-volume works appeared, in particular an encyclopedia on zoology: the Swiss scientist K. Gesner“History of Animals” in five volumes, a series of monographs (in thirteen volumes) by an Italian zoologist U. Aldrovani and many others.

During the Renaissance, great advances were made in the anatomy of the human body. In this regard, it is necessary to note the achievements of the Flemish natural scientist A. Vesalius, one of the first to begin studying the human body through dissections and was persecuted for this by the church. In 1543, Vesalius published his work “On the Structure of the Human Body,” in which, in particular, he showed the inconsistency of Galen’s views in the field of blood circulation and came close to the conclusion about the existence of a pulmonary circulation. The honor of the discovery of this latter belongs to the Spanish scientist Miguel Servet(1509 or 1511 - 1553) and independently of him to the Italian scientist R. Columbus(1559).

Famous English scientist and doctor William Harvey(1578 - 1657) is the founder of modern physiology and embryology, who gave a description of the systemic and pulmonary circulation, and in his work “Anatomical study of the movement of the heart and blood in animals” (1628) outlined the general doctrine of blood circulation in animals.

Creation in the 17th century. microscope made it possible to establish the cellular structure of animals and plants, to see the world of microbes, red blood cells (red blood cells - non-nuclear cells that carry oxygen from the lungs to the tissues and carbon dioxide from the tissues to the respiratory organs), the movement of blood in the capillaries and much more.

Above we talked in detail about the creation in the first half of the 18th century. Swedish scientist K. Linnaeus the so-called binary (with a double name - by genus and species) system of classification of flora and fauna. Although Linnaeus recognized the immutability of the world, his system played a major role in the development of biology. It should also be noted the research of the French scientist Georges Louis Leclerc Buffon(1707 - 1788), who created the “Natural History”, in 36 volumes of which a description of animals, humans, minerals is given, and the history of the Earth is also outlined. Buffon's ideas about the history of the Earth contained an assumption about the kinship of similar animal forms.

English materialist scientist Joseph Priestley (1733 - 1804), who conducted experiments with plants, showed that green plants emit gas necessary for respiration and, on the contrary, absorb gas that interferes with respiration. Plants, according to Priestley, seem to correct the air spoiled by breathing. French scientists A. Lavoisier, P. Laplace And A. Seguin determined the properties of oxygen and its role in the processes of combustion and respiration. Dutch doctor J. Ingenhouse and Swiss scientists J. Senebier And N. Saussure at the end of the 18th - beginning of the 19th century. established the role of sunlight in the process of oxygen release by green leaves.

Jean Baptiste Lamarck believed that the ladder of beings is a consequence of the evolution of living organisms from lower to higher. He believed that the reason for evolution is the inherent property of living organisms - the desire for perfection. As for the external environment and its impact on living organisms, then, according to Lamarck, such an impact exists and it occurs either through direct influence of the environment, which is characteristic of plants and lower organisms, or through intense, or, conversely, very weak exercise of certain organs, in this case higher animals.

For the time when Lamarck lived and worked, his views on the development of flora and fauna were progressive. As for the justification of evolution, revealing the reasons that give rise to it, Lamarck did not give an explanation for this, limiting himself only to a reference to some incomprehensible (and essentially idealistic) desire of organisms for improvement.

Outstanding French scientist Louis Pasteur (1822-1895) is considered the founder of modern microbiology, immunology and stereochemistry. He refuted the theory of spontaneous generation of microorganisms and discovered the nature of fermentation (a process that occurs without air access under the influence of microorganisms). But Pasteur’s works in the field of medicine, as well as in agriculture and the food industry, are most famous.

Pasteur discovered the role of microorganisms in infectious diseases of animals and humans, developed special vaccinations that both prevent this type of infectious disease (creating immunity) and are intended to help the body in the fight against an infectious disease.

The essence of the matter, in brief, boils down to the following. In mammals, especially in warm-blooded animals, immunity can manifest itself in two ways. In one case, so-called antibodies are formed in the blood against foreign, harmful proteins - antigens. In response to the introduction of an antigen (they can be not only foreign proteins, but also other large molecules), after some time (one to two weeks) antibodies appear in the blood - special proteins belonging to the group of immunoglobulins, specifically binding only to the antigen that caused their appearance. Each antibody molecule has two identical active centers, which allows them to bind two antigen molecules. Antibodies are synthesized in B lymphocytes, and the acquired ability to form a certain type of antibody (immunity) remains in the body for years, often throughout life. In another case, incompatibility between the cells of one organism (recipient host) and the cells of another organism (donor) occurs. By the way, it is the incompatibility of the cells of two different organisms that is most often the cause of complications and failures of transplantation - the transplantation of organs and tissues from one animal or person to another. Thus, the beneficial property of the body - the ability to create immunity (resist the action of harmful agents) in the case of transplantation causes great difficulties.

Russian plant physiologist and microbiologist Dmitry Iosifovich Ivanovsky(1864-1920), who first discovered the tobacco mosaic virus, is the founder of virology - a science that studies the structure and properties of viruses, diagnosis and treatment of diseases caused by them.

In his magnum opus, On the Origin of Species by Means of Natural Selection (1859) Charles Robert Darwin(1809 - 1882) put forward three main factors determining the evolution of life on Earth: variability, heredity and natural selection. Darwin's theory, based on these three factors, seems so convincing and irrefutable when you read his book that it seems strange that no one said it before. You involuntarily recall the above words of the ancient Greek philosopher and writer Plutarch about the clear and understandable explanations of Archimedes, and then it becomes obvious that the indisputability and persuasiveness of Darwin’s arguments is nothing more than a consequence of the genius and enormous work of their author.

World famous scientist, Englishman Charles Robert Darwin born in England in the small town of Shrewsbury near London in the family of a doctor. Darwin himself said this about his biography: “I studied, then traveled around the world, and then studied again: here is my autobiography.”

Darwin developed an interest in botany and zoology, as well as chemistry, in his childhood, but fate decreed otherwise: first he studied at the University of Cambridge as a doctor, and then, not feeling any attraction to medical practice, under pressure from his father he transferred to the Faculty of Theology the same university. In 1831, Darwin graduated from Cambridge University, received a bachelor's degree, and all that remained was to be ordained as a priest.

But at this time, Darwin’s friend at Cambridge, Professor of Biology Henslow, having received Darwin’s consent, recommended him as a naturalist on the Beagle ship, which, under the command of Captain R. Fitzroy, was to circumnavigate the world mainly for geographical purposes.

This was perhaps the main turning point in his life. The journey lasted from 1831 to 1836. It is beautifully described in Darwin's book, A Naturalist's Voyage Around the World on the Beagle.

The Beagle's route, which began in Devonport on December 27, 1831, passed across the Atlantic Ocean all the way to the city of Bahia, located in the Southern Hemisphere, on the eastern coast of Brazil. Here the Beagle remained until March 12, 1832, then moved south along the Atlantic coast. On July 26, 1832, the expedition reached the capital of Uruguay, Montevideo, and until May 1834, that is, almost two years, it carried out work on the east coast of South America. During this time, Tierra del Fuego was visited twice, and the Falkland Islands twice. Darwin also carried out land expeditions. On May 12, 1834, the Beagle headed south, passed through the Strait of Magellan and at the end of June 1834 reached the western shores of South America. The expedition remained on the Pacific coast of South America until September 1835, that is, more than a year, during which Darwin went on land expeditions, in particular, crossed the Cordillera. In September 1835, the Beagle left South America, heading for the Galapagos Islands. Following this, the expedition moved southwest, reached the Partnership Islands, then the Friendship Islands, and on December 20, 1835, dropped anchor in the Bay of Islands off the northern island of New Zealand. The expedition's course lay further towards Australia, the southern coast of which was bypassed from Sydney, through Tasmania, to King George's Bay in the southwestern part. From there the expedition headed northwest and reached the Cocos Islands. Then the Beagle changed course, heading to the island of Mauritius, rounded the Cape of Good Hope, visited the island of St. Helena, and on August 1, 1836 dropped anchor in Bahia, completing its circumnavigation. In October 1836, the Beagle returned to England.

The material that Darwin brought from his five-year trip around the world was enormous and varied. There were herbariums and collections, a large number of different records and much more.

23 years passed from Darwin’s return from his trip around the world to the publication of his book “The Origin of Species by Means of Natural Selection, or the Preservation of Favored Races in the Struggle for Life.” Meanwhile, in 1839, Darwin’s first scientific work, “Diary of Research,” was published; in 1842, he published a work on the structure and distribution of coral reefs, in which Darwin convincingly proved that the foundation of reefs is not ancient extinct volcanoes, as previously thought, and coral deposits that are underwater due to the subsidence of the sea floor. In 1842-1844. Darwin published the basic theory of evolution in his Essays.

After returning from his trip around the world, Darwin moved from London to the town of Down near London, where he bought a small estate, where he lived until the end of his days. Darwin got married before moving, and his family had many children.

So, Darwin’s main work, “The Origin of Species by Natural Selection, or the Preservation of Favored Breeds in the Struggle for Life” (briefly, “The Origin of Species”), was published in November 1859. The book convincingly, with a large number of examples, sets out the author’s ideas, which completely overturned previously existing ideas about the immutability of plant and animal life forms on Earth. Even before the book was published, Darwin wrote: “I gradually came to the realization that the Old Testament, with its attribution to God of the feeling of a vengeful tyrant, was no more trustworthy than the sacred books of the Hindus or the beliefs of some savage... So little by little it crept in there was disbelief in my soul, and in the end I became a complete unbeliever.”

He believed, firstly, that the plant and animal world is characterized by variability, that is, a variety of characteristics and properties in individual organisms and changes in these characteristics and properties for various reasons. Variation, therefore, is the basis of evolution, the first link of evolution. He believed, secondly, that heredity is a factor through which the characteristics and properties of organisms (including new ones) can be transmitted to subsequent generations. And finally, thirdly, that natural selection opens the way for those organisms that are most adapted to living conditions, to the external environment, and, conversely, “throws aside” unadapted organisms.

So, three pillars create the basis for the evolution of plant and animal organisms on Earth: variability, heredity and natural selection.

Darwin's materialistic theory of evolution, Darwinism, was a revolutionary step forward in the development of science.

The publication of Darwin's book On the Origin of Species was met with great interest. All 1,250 copies of the first edition were sold in one day. The second edition - 3,000 copies - also instantly sold out.

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