The newest book of facts. Volume 3 [Physics, chemistry and technology. History and archeology. Miscellaneous] Kondrashov Anatoly Pavlovich

When was the metric system of measures introduced in Russia?

The metric, or decimal, system of measures is called the aggregate of units of physical quantities, which is based on the unit of length - the meter. This system was developed in France during the 1789-1794 revolution. At the suggestion of a commission of the largest French scientists for a unit of length - a meter - one ten-millionth part of a quarter of the length of the Paris meridian was adopted. This decision was due to the desire to base the metric system of measures on an easily reproducible "natural" unit of length associated with a practically unchanged object of nature. The decree on the introduction of the metric system of measures in France was adopted on April 7, 1795. In 1799, a platinum prototype of the meter was manufactured and approved. The sizes, names and definitions of other units of the metric system of measures were chosen so that it is not national in nature and can be applied in all countries. The metric system of measures acquired a truly international character in 1875, when 17 countries, including Russia, signed the Metric Convention to ensure international unity and improve the metric system. The metric system of measures was approved for use in Russia (optional) by the law of June 4, 1899, the draft of which was developed by D.I.Mendeleev. It was introduced as a mandatory decree of the Council of People's Commissars of the RSFSR of September 14, 1918, and for the USSR - by the decree of the Council of People's Commissars of the USSR of July 21, 1925.

This text is an introductory fragment.

Metric system of measures, decimal system of measures, a set of units of physical quantities, which is based on the unit of length - meter... Initially, the Metric system of measures, in addition to the meter, included units: area - square meter, volume - cubic meter and mass - kilogram (mass of 1 dm 3 of water at 4 ° C), as well as liter(for capacity), ar(for the area of land plots) and ton(1000 kg). An important distinctive feature of the Metric system of measures was the way of education multiple units and fractional units in decimal ratios; for the formation of the names of derived units, the prefixes were adopted: kilo, hecto, soundboard, deci, centi and Milli.

The metric system of measures was developed in France during the era of the Great French Revolution. At the suggestion of a commission of the largest French scientists (J. Borda, J. Condorcet, P. Laplace, G. Monge, and others), the unit of length - a meter - was taken as a ten-millionth part of 1/4 of the length of the Paris geographic meridian. This decision was due to the desire to base the Metric system of measures in an easily reproducible "natural" unit of length associated with some practically unchanging object of nature. The decree introducing the Metric system of measures in France was adopted on April 7, 1795. In 1799, a platinum prototype of the meter was manufactured and approved. The sizes, names and definitions of other units of the Metric system of measures were chosen so that it is not national in nature and can be adopted by all countries. A truly international character The metric system of measures acquired in 1875, when 17 countries, including Russia, signed Metric convention to ensure international unity and improve the metric system. The metric system of measures was allowed for use in Russia (optional) by the law of June 4, 1899, the draft of which was developed by D.I.Mendeleev, and introduced as a mandatory decree of the SNK RSFSR of September 14, 1918, and for the USSR - SNK USSR dated July 21, 1925.

On the basis of the Metric system of measures, a number of particular ones arose, covering only certain sections of physics or branches of technology, systems of units and individual off-system units... The development of science and technology, as well as international relations has led to the creation of a single system of units based on the metric system of measures, covering all areas of measurement - International System of Units(SI), which is already accepted as mandatory or preferred by many countries.

(15. II.1564 - 8. I.1642) - an outstanding Italian physicist and astronomer, one of the founders of exact natural science, a member of the Accademia dei Lynches (1611). R. in Pisa. In 1581 he entered the University of Pisa, where he studied medicine. But, carried away by geometry and mechanics, in particular the works of Archimedes and Euclid, he left un-t with his scholastic lectures and returned to Florence, where he studied mathematics for four years on his own.

From 1589 - professor at Pisa un-that, in 1592 -1610 - of Padua, later - court philosopher of the Duke Cosimo II Medici.

He had a significant impact on the development of scientific thought. It is from him that physics as a science originates. Galileo mankind owes two principles of mechanics, which played an important role in the development of not only mechanics, but all of physics. This is the well-known Galilean principle of relativity for rectilinear and uniform motion and the principle of the constancy of the acceleration of gravity. Proceeding from the Galilean principle of relativity, I. Newton came to the concept of an inertial frame of reference, and the second principle, associated with the free fall of bodies, led him to the concept of inert and heavy mass. A. Einstein extended Galileo's mechanical principle of relativity to all physical processes, in particular to light, and derived from it consequences about the nature of space and time (in this case, Galileo's transformations are replaced by Lorentz's transformations). The combination of the second Galilean principle, which Einstein interpreted as the principle of equivalence of inertial forces to gravitational forces, with the principle of relativity led him to the general theory of relativity.

Galileo established the law of inertia (1609), the laws of free fall, the motion of a body on an inclined plane (1604 - 09) and a body thrown at an angle to the horizon, discovered the law of addition of motions and the law of the constancy of the period of oscillations of a pendulum (the phenomenon of isochronism of oscillations, 1583). The dynamics originate from Galileo.

In July 1609, Galileo built his first telescope - an optical system consisting of convex and concave lenses - and began systematic astronomical observations. This was the rebirth of the telescope, which, after nearly 20 years of obscurity, has become a powerful tool of scientific knowledge. Therefore, Galileo can be considered the inventor of the first telescope. He quickly improved his telescope and, as he wrote over time, "built himself a device so wonderful that with its help objects seemed almost a thousand times larger and more than thirty times closer than when observing with the naked eye." In his treatise "Star Messenger", published in Venice on March 12, 1610, he described the discoveries made with a telescope: the discovery of mountains on the moon, four moons of Jupiter, proof that the Milky Way is composed of many stars.

The creation of the telescope and astronomical discoveries brought Galileo wide popularity. Soon he discovers the phases of Venus, sunspots, and so on. Galileo is setting up the production of telescopes. By changing the distance between the lenses, at 1610 -14 also creates a microscope. Thanks to Galileo, lenses and optical instruments became powerful tools for scientific research. As SI Vavilov noted, "it was from Galileo that optics received the greatest stimulus for further theoretical and technical development." Galileo's optical research is also devoted to the theory of color, questions of the nature of light, and physical optics. Galileo came up with the idea of the finiteness of the speed of propagation of light and the setting (1607) of an experiment to determine it.

Galileo's astronomical discoveries played a huge role in the development of the scientific worldview, they clearly convinced of the correctness of Copernicus's teachings, the fallacy of the system of Aristotle and Ptolemy, contributed to the victory and establishment of the heliocentric system of the world. In 1632, the famous Dialogue on the Two Major Systems of the World was published, in which Galileo defended Copernicus's heliocentric system. The publication of the book infuriated the churchmen, the Inquisition accused Galileo of heresy and, having arranged the process, forced him to publicly abandon the Copernican doctrine, and imposed a ban on Dialogue. After the trial in 1633, Galileo was declared a "prisoner of the Holy Inquisition" and was forced to live first in Rome and then in Archertree near Florence. However, Galileo did not stop his scientific activity, until his illness (in 1637 Galileo finally lost his sight) he completed the work "Conversations and Mathematical Proofs Concerning Two New Branches of Science", which summed up his physical research.

Invented the thermoscope, which is the prototype thermometer, engineered (1586) hydrostatic balance to determine the specific gravity of solids, determined the specific gravity of air. He put forward the idea of using a pendulum in a clock. Physical research is also devoted to hydrostatics, strength of materials, etc.

Blaise Pascal, atmospheric pressure concept

(19. VI.1623 - 19. VIII.1662) - French mathematician, physicist and philosopher. R. in Clermont-Ferrand. Received education at home. In 1631 he and his family moved to Paris. At E. Pascal and some of his friends - M. Mersenne, J. Roberval and others - mathematicians and physicists gathered every week. These meetings eventually became scientific. meetings. Paris was created on the basis of this circle. AN (1666). From the age of 16, P. took part in the work of the circle. At this time, he wrote his first work on conic sections, in which he expressed one of the important theorems of projective geometry: the intersection points of opposite sides of a hexagon inscribed in a conical section lie on one straight line (Pascal's theorem).

Physical research relates mainly to hydrostatics, where in 1653 he formulated its main law, according to which pressure on a liquid is transmitted by it evenly without changing in all directions - Pascal's law (this property of a liquid was known to his predecessors), established the principle of operation of a hydraulic press. He rediscovered the hydrostatic paradox, which became widely known thanks to him. Confirmed existence atmospheric pressure, repeating in 1646 Torricelli's experience with water and wine. He expressed the idea that atmospheric pressure decreases with height (according to his idea, an experiment was carried out in 1647, which indicated that at the top of the mountain the level of mercury in the tube is lower than at the base), demonstrated the elasticity of air, proved that air has weight, discovered that the readings of the barometer depend on the humidity and temperature of the air, and therefore it can be used to predict the weather.

In mathematics, he devoted a number of works to arithmetic series and binomial coefficients. In the "Treatise on the Arithmetic Triangle" gave the so-called. Pascal's triangle - a table in a cut coefficient. the expansions (a + b) n for different n are arranged in the form of a triangle. Binomial coefficients formed, according to the method developed by him, a complete mat. induction - this was one of his most important discoveries. It was also new that the binomial coefficients. acted here as numbers of combinations of n elements in m and then were used in problems of probability theory. Until that time, none of the mathematicians calculated the probability of events. Pascal and P. Fermanashli are the key to solving such problems. In their correspondence, the theory of probability and combinatorics are scientifically substantiated, and therefore Pascal and Fermat are considered the founders of a new field of mathematics - the theory of probability. He also made a great contribution to the development of the infinitesimal calculus. Studying the cycloid, he proposed general methods for determining the quadratures and centers of gravity decomp. curves, discovered and applied such methods, which give reason to consider him one of the creators of the infinitesimal calculus. In "Treatise on the sines of a quarter circle", calculating the integrals of trigonometric functions, in particular the tangent, he introduced elliptic integrals, which later played an important role in analysis and its applications. In addition, he proved a number of theorems concerning the change of variables and integration by parts. In Pascal, there are, albeit in an undeveloped form, ideas about the equivalence of the differential as the main linear part of the increment to the increment itself and about the properties of equivalent infinitesimal quantities.

Back in 1642 he constructed a calculating machine for two arithmetic operations. The principles underlying this machine later became the starting point in the design of calculating machines.

The unit of pressure is named after him - the pascal.

Alessandro Volt, inventor of the Voltaic pillar, electrophore, electrometer

Alessandro Volta was born on February 18, 1745 in the small Italian town of Como, located near Lake Como, near Milan. An interest in the study of electrical phenomena awakened in him early. In 1769 he published a work on the Leyden bank, two years later - on an electric machine. In 1774 Volta became a physics teacher at a school in Como, invented the electrophore, then the eudiometer and other devices. In 1777 he became professor of physics at Pavia. In 1783 he invents an electroscope with a capacitor, and since 1792 he is intensively engaged in "animal electricity". These studies led him to the invention of the first galvanic cell.

In 1800 he built the first electric current generator - volt pole... This invention brought him worldwide fame. He was elected a member of the Paris and other academies, Napoleon made him count and senator of the Italian kingdom. But after his great discovery, Volta did not do anything significant in science. In 1819 he left his professorship and lived in his hometown of Como, where he died on March 5, 1827 (on the same day with Laplace and in the same year with Fresnel).

Volt pillar

Having begun work on "animal electricity" in 1792, Volta repeated and developed Galvani's experiments, fully adopting his point of view. But already in one of the first letters sent from Milan on April 3, 1792, he points out that the frog's muscles are very sensitive to electricity, they "react amazingly to electricity", completely elusive even for Bennett's electroscope, the most sensitive of all (made from two strips of the finest sheet of gold or silver). This is the beginning of Volta's subsequent statement that "the prepared frog represents, so to speak, an animal electrometer, incomparably more sensitive than any other most sensitive electrometer."

Volta, as a result of a long series of experiments, came to the conclusion that the cause of muscle contraction is not "animal electricity", but the contact of dissimilar metals. “The original cause of this electric current,” writes Volta, “whatever it may be, is the metals themselves, due to the fact that they are different. It is they in the proper sense of the word that are pathogens and engines, while the animal organ, the nerves themselves, are only passive. " Electrification on contact irritates the nerves of the animal, sets the muscles in motion, causes a sensation of sour taste on the tip of the tongue, placed between the sheet metal paper and a silver spoon, when silver and tin come into contact. Thus, Volta considers the causes of "galvanism" to be physical, and physiological actions as one of the manifestations of this physical process. If we briefly formulate Volta's thought in modern language, then it boils down to the following: Galvani discovered the physiological effect of electric current.

Naturally, controversy broke out between Galvani and Volta. Galvani tried to completely exclude physical reasons to prove his innocence. Volta, on the other hand, completely eliminated physiological objects, replacing the frog's leg with his electrometer. On February 10, 1794, he writes:

“What do you think of the so-called animal electricity? As for me, I have long been convinced that all action arises primarily as a result of the touch of metals to some wet body or to the water itself. Due to this contact, the electric fluid is driven into this wet body or into water from the metals themselves, from one more, from the other less (most of all from zinc, least of all from silver). When a continuous communication is established between the corresponding conductors, this fluid makes a constant circulation. "

Volta devices

This is the first description of a closed circuit of electric current. If the chain is broken and a viable frog nerve is inserted as a connecting link in the place of the break, then "the muscles controlled by such nerves begin to contract as soon as the circuit of conductors is closed and an electric current appears." As you can see, Volta already uses such a term as "closed circuit of electric current." He shows that the presence of a current in a closed circuit can also be detected by gustatory sensations if the tip of the tongue is inserted into the circuit. “And these sensations and movements are the stronger, the farther apart are the two metals used in the row in which they are placed here: zinc, tin foil, ordinary tin in plates, lead, iron, brass and bronze of various qualities, copper, platinum, gold, silver, mercury, graphite. " This is the famous "Volta series" in its first draft.

Volta divided the conductors into two classes. He attributed metals to the first, and liquid conductors to the second. If you make a closed circuit of dissimilar metals, then there will be no current - this is a consequence of Volta's law for contact voltages. If "a conductor of the second class is in the middle and comes into contact with two conductors of the first class of two different metals, then as a result of this there is an electric current of one direction or another."

It is quite natural that it was Volta who had the honor of creating the first electric current generator, the so-called voltaic pillar (Volta himself called it an "electric organ"), which had a tremendous impact not only on the development of the science of electricity, but also on the entire history of human civilization. The Voltaic pillar heralded the onset of a new era - the era of electricity.

Electrophore Volta

The triumph of the Voltaic pillar ensured Volta's unconditional victory over Galvani. History was wise in defining a winner in this dispute, in which both sides were right, each from their own point of view. "Animal electricity" does exist, and electrophysiology, of which Galvani was the father, now occupies an important place in science and practice. But at the time of Galvani, electrophysiological phenomena were not yet ripe for scientific analysis, and the fact that Volta turned Galvani's discovery on a new path was very important for the young science of electricity. By eliminating life, this most complex natural phenomenon, from the science of electricity, giving physiological actions only a passive role of a reagent, Volta ensured the rapid and fruitful development of this science. This is his immortal merit in the history of science and mankind.

Heinrich Rudolf Hertz, inventor of the "Hertz vibrator"

HEINRICH RUDOLF HERZ(1857-1894) was born on February 22 in Hamburg, the son of a lawyer who later became a senator. Hertz studied well and was an unsurpassed student in intelligence. He loved all subjects, loved to write poetry and work on a lathe. Unfortunately, Hertz was hampered all his life by poor health.

In 1875, after graduating from the gymnasium, Hertz entered the Dresden and then the Munich Higher Technical School. Business went well as long as general subjects were studied. But as soon as specialization began, Hertz changed his mind. He does not want to be a narrow specialist, he is eager for scientific work and enters the University of Berlin. Hertz was lucky: Helmholtz turned out to be his direct mentor. Although the famous physicist was an adherent of the theory of long-range action, but as a true scientist he unconditionally recognized that the ideas of Faraday-Maxwell about short-range action and the physical field give excellent agreement with experiment.

Once at the University of Berlin, Hertz with a great desire aspired to classes in physics laboratories. But only those students who were engaged in solving competitive problems were allowed to work in the laboratories. Helmholtz proposed to Hertz a problem from the field of electrodynamics: does an electric current have kinetic energy? Helmholtz wanted to direct Hertz's forces into the field of electrodynamics, considering it the most confusing.

Hertz is accepted for the solution of the task, calculated for 9 months. He makes the devices himself and debugs them. When working on the first problem, the features of a researcher inherent in Hertz were immediately revealed: perseverance, rare diligence and the art of an experimenter. The problem was solved in 3 months. The result, as expected, was negative. (Now it is clear to us that the electric current, which is the directed motion of electric charges (electrons, ions), has kinetic energy. In order for Hertz to detect this, it was necessary to increase the accuracy of his experiment thousands of times.) The result obtained coincided with the point of view Helmholtz, although erroneous, he was not mistaken in the abilities of the young Hertz. “I saw that I was dealing with a student of a completely unusual talent,” he later noted. Hertz's work was awarded a prize.

Returning from the summer vacation of 1879, Hertz secured permission to work on a different topic:<0б индукции во вращающихся телах«, взятой в качестве докторской диссертации. Это была теоретическая работа. Он предполагал завершить ее за 2-3 месяца, защитить и получить поскорее звание доктора, хотя университет еще не был закончен. Работая с большим подъемом и воодушевлением, Герц быстро закончил исследование. Зашита прошла успешно, и ему присудили степень доктора с «отличием» - явление исключительно редкое, тем более для студента.

From 1883 to 1885, Hertz headed the Department of Theoretical Physics in the provincial town of Kiel, where there was no physics laboratory at all. Hertz decided to deal with theoretical questions here. He corrects the system of equations of electrodynamics of one of the brightest representatives of Neumann's long-range action. As a result of this work, Hertz wrote his own system of equations, from which Maxwell's equations were easily obtained. Hertz is disappointed, because he was trying to prove the universality of the electrodynamic theories of representatives of long-range action, and not Maxwell's theory. “This conclusion cannot be considered an exact proof of the Maxwellian system as the only possible one,” he makes for himself an essentially reassuring conclusion.

In 1885, Hertz accepts an invitation from the technical school in Karlsruhe, where his famous experiments on the propagation of electrical force will be carried out. Back in 1879, the Berlin Academy of Sciences set the task: "To show experimentally the presence of some connection between electrodynamic forces and the dielectric polarization of dielectrics." Hertz's preliminary calculations showed that the expected effect would be very small even under the most favorable conditions. Therefore, apparently, he abandoned this work in the fall of 1879. However, he did not stop thinking about possible ways of solving it and came to the conclusion that this requires high-frequency electrical oscillations.

Hertz carefully studied everything that was known by this time about electrical oscillations, both theoretically and experimentally. Having found a pair of induction coils in the physics office of a technical school and conducting lecture demonstrations with them, Hertz discovered that with their help it was possible to obtain fast electrical oscillations with a period of 10 -8 C. As a result of experiments, Hertz created not only a high-frequency generator (a source of high-frequency oscillations) , but also the resonator is the receiver of these vibrations.

The Hertz generator consisted of an induction coil and wires connected to it, forming a discharge gap, a resonator, of a rectangular wire and two balls at its ends, which also form a discharge gap. As a result of the experiments, Hertz found that if high-frequency oscillations occur in the generator (a spark jumps in its discharge gap), then in the discharge gap of the resonator, which is even 3 m away from the generator , small sparks will skip too. Thus, the spark in the second circuit was generated without any direct contact with the first circuit. What is the mechanism of its transmission Or is it electric induction, according to Helmholtz's theory, or an electromagnetic wave, according to Maxwell's theory In 1887, Hertz still does not say anything about electromagnetic waves, although he had already noticed that the effect of the generator on the receiver is especially strong in the case of resonance (the oscillation frequency of the generator coincides with the natural frequency of the resonator).

Having carried out numerous experiments at various mutual positions of the generator and receiver, Hertz comes to the conclusion about the existence of electromagnetic waves propagating with a finite speed. Will they behave like a light And Hertz is conducting a thorough test of this assumption. After studying the laws of reflection and refraction, after establishing polarization and measuring the speed of electromagnetic waves, he proved their complete analogy with light. All this was stated in the work "On the Rays of Electric Force", published in December 1888. This year is considered the year of the discovery of electromagnetic waves and the experimental confirmation of Maxwell's theory. In 1889, speaking at the congress of German natural scientists, Hertz said: “All these experiments are very simple in principle, nevertheless they entail the most important consequences. They destroy any theory that believes that electrical forces jump over space instantly. They signify a brilliant victory for Maxwell's theory. How unlikely her view of the essence of light seemed earlier, it is so difficult now not to share this view.

Hertz's hard work did not go unpunished for his already frail health. At first, the eyes refused, then the ears, teeth and nose ached. Soon, general blood poisoning began, from which the famous scientist Heinrich Hertz, already at the age of 37, died.

Hertz completed the enormous work begun by Faraday. If Maxwell transformed Faraday's representations into mathematical images, then Hertz turned these images into visible and audible electromagnetic waves, which became an eternal monument to him. We remember G. Hertz, when we listen to the radio, watch TV, when we rejoice at the TASS report about new launches of spacecraft, with which stable communication is maintained using radio waves. And it is no coincidence that the first words transmitted by the Russian physicist A. S. Popov through the first wireless connection were: "Heinrich Hertz."

"Very fast electrical vibrations"

Heinrich Rudolf Hertz, 1857-1894

Between 1886 and 1888, Hertz studied the emission and reception of electromagnetic waves in the corner of his physics study at the Karlsruhe Polytechnic School (Berlin). For these purposes, he invented and constructed his famous emitter of electromagnetic waves, later called "Hertz's vibrator". The vibrator consisted of two copper rods with brass balls fixed at the ends and one large zinc sphere or square plate each, which played the role of a capacitor. There was a gap between the balls - a spark gap. The ends of the secondary winding of the Rumkorf coil, a low voltage DC to high voltage AC converter, were attached to the copper rods. With pulses of alternating current, sparks jumped between the balls and electromagnetic waves were emitted into the surrounding space. By moving the spheres or plates along the rods, the inductance and capacitance of the circuit, which determine the wavelength, were regulated. To catch the emitted waves, Hertz invented the simplest resonator - a wire open ring or a rectangular open frame with the same brass balls at the ends of the "transmitter" and an adjustable spark gap.

Hertz vibrator

The concept of a Hertz vibrator is introduced, a working diagram of a Hertz vibrator is presented, the transition from a closed loop to an electric dipole is considered

Through a vibrator, resonator and reflective metal screens, Hertz proved the existence of the electromagnetic waves predicted by Maxwell, propagating in free space. He proved their identity to light waves (the similarity of the phenomena of reflection, refraction, interference and polarization) and was able to measure their length.

Thanks to his experiments, Hertz came to the following conclusions: 1 - Maxwell's waves are "synchronous" (the validity of Maxwell's theory that the speed of propagation of radio waves is equal to the speed of light); 2 - you can transfer the energy of the electric and magnetic field without wires.

In 1887, upon completion of the experiments, Hertz's first article "On very fast electrical oscillations" was published, and in 1888 - an even more fundamental work "On electrodynamic waves in air and their reflection."

Hertz believed that his discoveries were no more practical than Maxwell's: “It is absolutely useless. This is just an experiment that proves that Maestro Maxwell was right. We just have mysterious electromagnetic waves that we cannot see with the eye, but they are. " "So what's next?" one of the students asked him. Hertz shrugged his shoulders, he was a modest man, without pretensions and ambitions: "I suppose - nothing."

But even at the theoretical level, Hertz's achievements were immediately noted by scientists as the beginning of a new "electric era".

Heinrich Hertz died at the age of 37 in Bonn from blood poisoning. After Hertz's death in 1894, Sir Oliver Lodge remarked: “Hertz did what the eminent English physicists could not do. In addition to confirming the truth of Maxwell's theorems, he did so with discouraging modesty. "

Edward Eugene Desair Branly, inventor of the Branly sensor

Edouard Branly's name is not particularly well known in the world, but in France he is considered one of the most important contributors to the invention of radiotelegraph communication.

In 1890, Edouard Branly, a professor of physics at the Catholic University of Paris, became seriously interested in the possibility of using electricity in therapy. In the mornings, he went to Paris hospitals, where he performed medical procedures with electric and induction currents, and during the day he studied the behavior of metal conductors and galvanometers when exposed to electric charges in his physics laboratory.

The device that made Branly famous was "a glass tube freely filled with metal filings" or "Branly gauge"... When the sensor was connected to an electrical circuit containing a battery and a galvanometer, it worked as an insulator. However, if an electric spark appeared at some distance from the circuit, the sensor began to conduct current. When the tube was slightly shaken, the sensor again became an insulator. The reaction of the Branley sensor to a spark was observed within the laboratory premises (up to 20 m). The phenomenon was described by Branley in 1890.

By the way, a similar method of changing the resistance of sawdust, only coal, with the passage of an electric current, until recently, was widely used (and in some houses is still used today) in telephone microphones (the so-called "carbon" microphones).

According to historians, Branley never considered the possibility of transmitting signals. He was mainly interested in the parallels between medicine and physics, and sought to offer the medical world an interpretation of nerve conduction, modeled with the help of tubes filled with metal filings.

For the first time, the British physicist Oliver Lodge publicly demonstrated the connection between the conductivity of the Branley sensor and electromagnetic waves.

Lavoisier Antoine Laurent, inventor of the calorimeter

Antoine Laurent Lavoisier was born on August 26, 1743 in Paris in the family of a lawyer. He received his initial education at the College of Mazarin, and in 1864 he graduated from the law faculty of the University of Paris. Already while studying at the University of Lavoisier, in addition to jurisprudence, he was thoroughly engaged in the natural and exact sciences under the guidance of the best Parisian professors of that time.

In 1765, Lavoisier presented a work on the theme set by the Paris Academy of Sciences - "On the best way to illuminate the streets of a big city." When performing this work, the extraordinary persistence of Lavoisier in pursuit of the intended goal and accuracy in research - the advantages that make up a distinctive feature of all his works, affected. For example, to increase the sensitivity of his vision to subtle changes in luminous intensity, Lavoisier spent six weeks in a dark room. This work by Lavoisier was awarded a gold medal by the academy.

In the period 1763-1767. Lavoisier makes a number of excursions with the famous geologist and mineralogist Guettard, helping the latter in compiling a mineralogical map of France. Already these first works by Lavoisier opened the doors of the Paris Academy for him. On May 18, 1768, he was elected to the academy as an adjunct in chemistry, in 1778 he became a full member of the academy, and from 1785 he was its director.

In 1769, Lavoisier joined the Company of ransoms, an organization of forty large financiers, in exchange for the immediate transfer of a certain amount to the treasury, which received the right to collect state indirect taxes (on salt, tobacco, etc.). As a tax-farmer, Lavoisier made a huge fortune, part of which he spent on scientific research; however, it was his participation in the Company of the Bribes that became one of the reasons why Lavoisier was sentenced to death in 1794.

In 1775, Lavoisier became director of the Office of Powder and Saltpeter. Thanks to the energy of Lavoisier, the production of gunpowder in France more than doubled by 1788. Lavoisier organizes expeditions to find saltpeter deposits, conducts research on the purification and analysis of saltpeter; the methods of cleaning saltpeter, developed by Lavoisier and Baume, have survived to our time. Lavoisier managed the gunpowder business until 1791. He lived in the gunpowder Arsenal; here was also located an excellent chemical laboratory, which he created at his own expense, from which almost all the chemical works that immortalized his name came out. Lavoisier's laboratory was one of the main scientific centers of Paris at that time.

In the early 1770s. Lavoisier began systematic experimental work on the study of combustion processes, as a result of which he came to the conclusion that the phlogiston theory was inconsistent. Having received oxygen in 1774 (following K.V.Sheele and J.Pristley) and being able to realize the significance of this discovery, Lavoisier created an oxygen theory of combustion, which he expounded in 1777. Lavoisier proves the complex composition of air, which, in his opinion, consists of "clean air" (oxygen) and "suffocating air" (nitrogen). In 1781, together with the mathematician and chemist J. B. Meunier, he also proved the complex composition of water, having established that it consists of oxygen and "combustible air" (hydrogen). In 1785, they also synthesize water from hydrogen and oxygen.

The doctrine of oxygen, as the main agent of combustion, was initially met with very hostility. The renowned French chemist Mackeur makes fun of the new theory; in Berlin, where the memory of the creator of the phlogiston theory, G. Stahl, was especially revered, Lavoisier's works were even burnt. Lavoisier, however, wasting no time at first on polemics with the view, the failure of which he felt, step by step, persistently and patiently established the foundations of his theory. Only after carefully studying the facts and finally clarifying his point of view, Lavoisier in 1783 openly criticized the doctrine of phlogiston and showed its precariousness. Establishing the composition of water was a decisive blow to the phlogiston theory; her supporters began to go over to the side of the teachings of Lavoisier.

Based on the properties of oxygen compounds, Lavoisier was the first to give a classification of "simple bodies" known at that time in chemical practice. Lavoisier's concept of elementary bodies was purely empirical: Lavoisier considered as elementary those bodies that could not be decomposed into simpler components.

The basis for his classification of chemical substances, together with the concept of simple bodies, were the concepts of "oxide", "acid" and "salt". Lavoisier's oxide is a combination of a metal with oxygen; acid - a compound of a non-metallic body (for example, coal, sulfur, phosphorus) with oxygen. Organic acids - acetic, oxalic, tartaric, etc. - Lavoisier considered as compounds with oxygen of various "radicals". Salt is formed by combining an acid with a base. This classification, as further studies soon showed, was narrow and therefore incorrect: some acids, such as hydrocyanic acid, hydrogen sulfide, and the corresponding salts, did not fit these definitions; Lavoisier considered hydrochloric acid to be a combination of oxygen with a still unknown radical, and considered chlorine as a combination of oxygen with hydrochloric acid. Nevertheless, this was the first classification, which made it possible to survey with great simplicity a whole series of bodies known at that time in chemistry. She gave Lavoisier the opportunity to predict the complex composition of such bodies as lime, barite, caustic alkalis, boric acid, etc., which were considered elementary bodies before him.

In connection with the rejection of the phlogiston theory, it became necessary to create a new chemical nomenclature, which was based on the classification given by Lavoisier. Lavoisier developed the basic principles of the new nomenclature in 1786-1787. together with C.L. Berthollet, L.B. Guiton de Morveaux and A.F. Furcroix. The new nomenclature brought great simplicity and clarity to the chemical language, clearing it of the complex and confusing terms that were bequeathed to alchemy. Since 1790, Lavoisier also took part in the development of a rational system of measures and weights - metric.

The subject of Lavoisier's study was also thermal phenomena closely related to the combustion process. Together with Laplace, the future creator of Celestial Mechanics, Lavoisier gave rise to calorimetry. They create ice calorimeter, with the help of which the heat capacity of many bodies and the heat released during various chemical transformations are measured. Lavoisier and Laplace in 1780 establish the basic principle of thermochemistry, formulated by them in the following form: "Any thermal changes that any material system undergoes, changing its state, occur in the reverse order, when the system returns to its original state."

In 1789 Lavoisier published the textbook "Elementary Course of Chemistry", entirely based on the oxygen theory of combustion and the new nomenclature, which became the first textbook of new chemistry. Since the French Revolution began in the same year, the revolution accomplished in chemistry by the labors of Lavoisier is commonly referred to as the "chemical revolution".

The creator of the chemical revolution, Lavoisier, however, became a victim of the social revolution. At the end of November 1793, the former participants in the ransom were arrested and brought to trial by the revolutionary tribunal. Neither a petition from the "Advisory Bureau of Arts and Crafts", nor well-known services to France, nor scientific fame saved Lavoisier from death. "The republic does not need scientists," said the president of the Coffinal tribunal in response to a petition from the bureau. Lavoisier was accused of participation "in a conspiracy with the enemies of France against the French people, with the aim of stealing from the nation huge sums necessary for the war against despots," and sentenced to death. “It was enough for the executioner to cut off this head,” the famous mathematician Lagrange said about the execution of Lavoisier, “but it will not be a century long to give another one the same ...” In 1796, Lavoisier was posthumously rehabilitated.

Since 1771, Lavoisier was married to the daughter of his comrade-in-law, Benez. In his wife, he found himself an active assistant in his scientific works. She kept his laboratory journals, translated scientific articles from English for him, drew and engraved drawings for his textbook. After Lavoisier's death, his wife in 1805 remarried the famous physicist Rumford. She died in 1836 at the age of 79.

Pierre Simon Laplace, inventor of the calorimeter, the barometric formula

French astronomer, mathematician and physicist Pierre Simon de Laplace was born in Beaumont-en-Auge, Normandy. He studied at the Benedictine school, from which he left, however, a convinced atheist. In 1766 Laplace arrived in Paris, where J. D'Alembert five years later helped him to get the position of professor at the Military School. He actively participated in the reorganization of the higher education system in France, in the creation of the Normal and Polytechnic Schools. In 1790 Laplace was appointed chairman of the Chamber of Weights and Measures, supervised the introduction of the new metric system of measures. Since 1795 he was a member of the leadership of the Bureau of Longitudes. Member of the Paris Academy of Sciences (1785, adjunct from 1773), member of the French Academy (1816).

Laplace's scientific legacy belongs to the field of celestial mechanics, mathematics and mathematical physics, Laplace's works on differential equations, in particular on integration by the method of "cascades" of partial differential equations, are fundamental. The spherical functions introduced by Laplace have various applications. In Laplace algebra, there is an important theorem on the representation of determinants by the sum of products of complementary minors. To develop the mathematical theory of probability created by him, Laplace introduced the so-called generating functions and widely used the transformation that bears his name (Laplace transform). The theory of probability was the basis for the study of all kinds of statistical laws, especially in the field of natural science. Before him, the first steps in this area were taken by B. Pascal, P. Fermat, J. Bernoulli and others. Laplace brought their conclusions into a system, improved the methods of proof, making them less cumbersome; proved the theorem that bears his name (Laplace's theorem), developed the theory of errors and the method of least squares, which make it possible to find the most probable values of the measured quantities and the degree of reliability of these calculations. Laplace's classic work "Analytical Theory of Probabilities" was published three times during his lifetime - in 1812, 1814 and 1820; as an introduction to the latest editions, the work "Experience of the Philosophy of the Theory of Probability" (1814) was placed, in which the main provisions and significance of the theory of probability are explained in a popular form.

Together with A. Lavoisier in 1779-1784. Laplace was engaged in physics, in particular, the question of the latent heat of fusion of bodies and work with the created by them ice calorimeter... They used a telescope for the first time to measure the linear expansion of bodies; studied the combustion of hydrogen in oxygen. Laplace actively opposed the erroneous phlogiston hypothesis. Later he returned to physics and mathematics. He published a number of papers on the theory of capillarity and established the law that bears his name (Laplace's law). In 1809 Laplace took up the problem of acoustics; derived a formula for the speed of sound propagation in air. Laplace belongs barometric formula to calculate the change in air density with height above the earth's surface, taking into account the effect of air humidity and the change in the acceleration of gravity. He was also engaged in geodesy.

Laplace developed the methods of celestial mechanics and completed almost everything that his predecessors did not succeed in explaining the motion of bodies of the solar system on the basis of Newton's law of universal gravitation; he managed to prove that the law of universal gravitation fully explains the motion of these planets, if we represent their mutual perturbations in the form of rows. He also proved that these disturbances are of a periodic nature. In 1780 Laplace proposed a new way of calculating the orbits of celestial bodies. Laplace's research proved the stability of the solar system for a very long time. Then Laplace came to the conclusion that the ring of Saturn cannot be continuous, because in this case it would be unstable, and predicted the discovery of a strong contraction of Saturn at the poles. In 1789 Laplace considered the theory of motion of Jupiter's satellites under the influence of mutual perturbations and attraction to the Sun. He obtained complete agreement between theory and observations and established a number of laws for these movements. One of Laplace's main achievements was the discovery of the reason for the acceleration in the motion of the moon. In 1787, he showed that the average speed of the Moon depends on the eccentricity of the earth's orbit, and the latter changes under the influence of the attraction of the planets. Laplace proved that this disturbance is not secular, but long-period, and that subsequently the Moon will move slowly. From the inequalities in the motion of the moon, Laplace determined the magnitude of the compression of the earth at the poles. He also belongs to the development of the dynamic theory of tides. Celestial mechanics owes much to the works of Laplace, which were summarized by him in the classic work A Treatise on Celestial Mechanics (vols. 1-5, 1798-1825).

Laplace's cosmogonic hypothesis was of great philosophical significance. It was presented by him in the appendix to his book "Exposition of the system of the world" (vols. 1-2, 1796).

In his philosophical views, Laplace was close to the French materialists; Laplace's answer to Napoleon I is known that, in his theory of the origin of the solar system, he did not need a hypothesis about the existence of God. The limitations of Laplace's mechanistic materialism manifested itself in an attempt to explain the whole world, including physiological, mental and social phenomena, in terms of mechanistic determinism. Laplace regarded his understanding of determinism as a methodological principle for the construction of any science. Laplace saw the model of the final form of scientific knowledge in celestial mechanics. Laplace's determinism has become a household name for the mechanistic methodology of classical physics. Laplace's materialistic worldview, vividly expressed in scientific works, contrasts with his political instability. In every political coup, Laplace went over to the side of the victors: at first he was a republican, after Napoleon came to power - the minister of the interior; then he was appointed a member and vice-president of the Senate, under Napoleon received the title of count of the empire, and in 1814 he cast his vote for the deposition of Napoleon; after the restoration the Bourbons received the peerage and the title of marquis.

Oliver Joseph Lodge, inventor of the coherer

Among Lodge's major merits in the radio context are his enhancements to the Branley radio wave sensor.

Coherer Lodge, first demonstrated to the audience of the Royal Institution in 1894, made it possible to receive Morse code signals transmitted by radio waves and made it possible to record them with a recording apparatus. This allowed the invention to soon become the standard wireless telegraph apparatus. (The sensor went out of use only ten years later, when magnetic, electrolytic and crystal sensors were developed).

Lodge's other work in the field of electromagnetic waves is no less important. In 1894, Lodge, in the pages of the London Electrician, discussing the significance of Hertz's discoveries, described his experiments with electromagnetic waves. He commented on the phenomenon of resonance or tuning that he discovered:

... some circuits are inherently “vibrating ... They are capable of sustaining the oscillations that have arisen in them for a long period, while in other circuits the oscillations are rapidly damped. A damped receiver will respond to waves of any frequency, as opposed to a fixed frequency receiver that only responds to waves with its natural frequency.

Lodge found that the Hertzian vibrator "emits very powerfully," but "because of the radiation of energy (into space), its vibrations are rapidly damped, so in order to transmit a spark, it must be tuned to match the receiver."

On August 16, 1898, Lodge received Patent No. 609154, which proposed "the use of a tunable induction coil or antenna circuit in wireless transmitters or receivers, or both." This “syntonic” patent was significant in the history of radio as it laid out the principles of tuning to the desired station. On March 19, 1912, this patent was acquired by the Marconi company.

Subsequently, Marconi said this about Lodge:

He (Lodge) is one of our greatest physicists and thinkers, but his work in the field of radio is especially significant. From the earliest days, after the experimental confirmation of Maxwell's theory of the existence of electromagnetic radiation and its propagation through space, very few people had a clear understanding of the solution to this one of the most hidden secrets of nature. Sir Oliver Lodge possessed this understanding far more than any of his contemporaries.

Why didn't Lodge invent radio? He himself explained this fact:

I was too busy with work to take on the development of the telegraph or any other direction of technology. I didn’t have enough understanding to feel how extraordinarily important this would turn out to be for the navy, trade, civilian and military communications.

For his contribution to the development of science in 1902, King Edward VII knighted Lodge.

The further fate of Sir Oliver is interesting and mysterious.

After 1910, he became interested in spiritualism and became an ardent supporter of the idea of communication with the dead. He was interested in the connection between science and religion, telepathy, the manifestation of the mysterious and the unknown. In his opinion, the easiest way to communicate with Mars would be to move giant geometric shapes across the Sahara Desert. At the age of eighty, Lodge announced that he would try to contact the living world after his death. He deposited a sealed document with the English Society for Psychical Research, which, he said, contained the text of a message that he would transmit from the other world.

Luigi Galvani, inventor of the galvanometer

Luigi Galvani was born in Bologna on September 9, 1737. He studied first theology, and then medicine, physiology and anatomy. In 1762 he was already a professor of medicine at the University of Bologna.

In 1791, Galvani's famous discovery was described in his "Treatise on the Forces of Electricity in Muscular Movement". The phenomena themselves, discovered by Galvani, for a long time in textbooks and scientific articles were called "Galvanism"... This term is still preserved in the name of some devices and processes. Galvani himself describes his discovery as follows:

“I cut and dissected the frog ... and, with something completely different in mind, I placed it on the table on which there was an electric machine ... with the latter completely disconnected from the conductor and at a fairly large distance from him. When one of my assistants with the tip of a scalpel accidentally very lightly touched the internal femoral nerves of this frog, then immediately all the muscles of the limbs began to contract so that they seemed to have fallen into severe tonic convulsions. Another of them, who helped us in experiments on electricity, noticed how he it seemed that it succeeded when a spark was drawn from the conductor of the car ... Surprised by the new phenomenon, he immediately drew my attention to it, although I was planning something completely different and was absorbed in my own thoughts. Then I was kindled with incredible zeal and a passionate desire to explore this phenomenon and bring to light what was hidden in it. "

This description, which is classic in terms of accuracy, has been repeatedly reproduced in historical works and has generated numerous comments. Galvani honestly writes that it was not he who first noticed the phenomenon, but his two assistants. It is believed that "another of those present" who pointed out that muscle contraction occurs when a spark skips in a car, was his wife Lucia. Galvani was busy with his thoughts, and at this time someone began to rotate the handle of the machine, someone touched the drug "lightly" with a scalpel, someone noticed that muscle contraction occurs when a spark slipped. This is how a great discovery was born in a chain of accidents (all the characters could hardly have conspired with each other). Galvani distracted himself from his thoughts, "he himself began to touch with the tip of a scalpel one or the other femoral nerve, while one of those present pulled out a spark, the phenomenon occurred in exactly the same way."

As you can see, the phenomenon was very complex, three components came into action: an electric machine, a scalpel, a frog's leg preparation. What is essential? What happens if one of the components is missing? What is the role of a spark, scalpel, frog? Galvani tried to get an answer to all these questions. He set up numerous experiments, including on the street during a thunderstorm. “And so, sometimes noticing that the dissected frogs, which were suspended on an iron lattice that surrounded the balcony of our house, with the help of copper hooks stuck in the spinal cord, fell into usual contractions not only in a thunderstorm, but sometimes also in a calm and clear sky I decided that these reductions were caused by changes occurring during the day in atmospheric electricity. " Galvani goes on to describe how he waited in vain for these reductions. "Tired, at last, of vain waiting, I began to press the copper hooks stuck in the spinal cord to the iron lattice" and here I found the desired contractions, which occurred without any changes "in the state of the atmosphere and electricity."

Galvani transferred the experiment to a room, placed the frog on an iron plate, to which he began to press a hook passed through the spinal cord, muscle contractions immediately appeared. This was the decisive discovery.

Galvani realized that something new had opened before him, and decided to thoroughly investigate the phenomenon. He felt that in such cases “it is easy to make a mistake with research and consider what we want to see and find seen and found,” in this case the effect of atmospheric electricity. He transferred the drug “into a closed room, placed it on an iron plate and began to press it a hook passed through the spinal cord ”. At the same time, "the same contractions, the same movements appeared." So, there is no electric machine, no atmospheric discharges, and the effect is observed, as before "Of course," Galvani writes, "such a result aroused considerable surprise in us and began to arouse in us some suspicion about the electricity inherent in the animal itself." To check the validity of such a "suspicion", Galvani performs a series of experiments, including a spectacular experiment, when a suspended foot, touching a silver plate, contracts, pushes up, then falls, contracts again, etc. "So this foot, - writes Galvani, - to the great admiration of those watching her, it seems that he begins to compete with some kind of electric pendulum.

Galvani's suspicion turned into confidence: the frog's leg became the carrier of "animal electricity" for him, like a charged Leyden jar. "After these discoveries and observations, it seemed to me possible without any delay to conclude that this dual and opposite electricity is in the animal preparation itself." He showed that positive electricity is in the nerve, negative electricity in the muscle.

It is quite natural that the physiologist Galvani came to the conclusion about the existence of "animal electricity". The whole atmosphere of the experiments pushed to this conclusion. But the physicist, who first believed in the existence of "animal electricity", soon came to the opposite conclusion about the physical cause of the phenomenon. This physicist was Galvani's famous compatriot Alessandro Volta.

John Ambrose Fleming, inventor of the wave meter

English engineer John Fleming made significant contributions to the development of electronics, photometry, electrical measurements and radiotelegraphy. Best known for his invention of a radio detector (rectifier) with two electrodes, which he called a thermionic lamp, also known as a vacuum diode, a kenotron, an electronic lamp, and a Fleming lamp or diode. This device, patented in 1904, was the first electronic radio wave detector to convert AC radio signals into direct current. Fleming's discovery was the first step in the era of tube electronics. An era that lasted almost until the end of the 20th century.

Fleming studied at University College London and Cambridge under the great Maxwell, for many years he worked as a consultant in the London companies of Edison and Marconi.

He was a very popular teacher at University College and the first to be awarded the title of professor of electrical engineering. He has authored over a hundred scientific articles and books, including the popular Principles of Electrical Wave Telegraph Communication (1906) and The Propagation of Electric Currents in Telephone and Telegraph Wires (1911), which have been leading books on the topic for many years. In 1881, as electricity began to gain widespread attention, Fleming joined the Edison Company in London as an electrical engineer, which he held for nearly ten years.

It was natural that Fleming's work on electricity and telephony should sooner or later lead him into the nascent radio engineering. For more than twenty-five years, he served as a scientific advisor to the Marconi company and even took part in the creation of the first transatlantic station at Poldu.

For a long time, the controversy over the wavelength at which the first transatlantic transmission was conducted did not subside. In 1935, in his memoirs, Fleming commented on this fact:

“In 1901, the wavelength of electromagnetic radiation was not measured, because by that time I had not yet invented wave meter(invented October 1904). The antenna suspension height in the first version was 200 feet (61 m). In series with the antenna, we connected a transformer coil or "jiggeroo" (damped oscillation transformer). I estimated the original wavelength should have been at least 3,000 feet (915 m), but later it was much higher.

At the time, I knew that diffraction, the bending of waves around the earth, would increase with increasing wavelength, and after the first success I constantly urged Marconi to increase the wavelength, which was done when commercial transmissions began. I remember that I developed special wavemeters to measure waves of about 20,000 feet (6096 m). "

Pold's triumph belonged to Marconi, and Fleming became famous for the "small electric incandescent lamp" - Fleming's diode. He himself described this invention as follows:

“In 1882, as an electrical advisor to the Edison Electric Light Company of London, I solved numerous problems with incandescent lamps and began to study the physical phenomena occurring in them with all the technical means at my disposal. Like many others, I noticed that incandescent filaments broke easily with small blows and after the lamps burned out, their glass bulbs changed color. This glass change was so common that it was accepted by everyone for granted. It seemed a trifle to pay attention to it. But in science, all the little things must be taken into account. Little things today and tomorrow can make a huge difference.

Asking why the incandescent bulb was getting dark, I began to investigate this fact and found that in many of the burned out bulbs there was a strip of glass that did not change color. It looked like someone had taken a smoked flask and wiped off the plaque, leaving a clean, narrow strip. I found that lamps with these strange, sharply defined clear areas were covered in precipitated carbon or metal elsewhere. And the clean strip was certainly U-shaped, repeating the shape of the carbon thread, and just on the side of the flask opposite from the burnt thread.

It became obvious to me that the undisturbed part of the filament acted as a screen, leaving that very characteristic strip of clean glass, and that charges from the heated filament bombarded the lamp walls with molecules of carbon or vaporized metal. My experiments in late 1882 and early 1883 proved that I was right. "

Edison also noticed this phenomenon, by the way, called the "Edison effect", but could not explain its nature.

In October 1884, William Preece was researching the "Edison effect". He decided that this was due to the emission of carbon molecules from the filament in rectilinear directions, thus confirming my initial discovery. But Pris, like Edison, also did not seek the truth. He did not explain the phenomenon and did not seek to apply it. The Edison Effect remained the secret of the incandescent lamp.

In 1888 Fleming obtained several special carbon incandescent lamps made in England by Edison and Joseph Swann and continued his experiments. He applied a negative voltage to the carbon filament and noticed that the bombardment of charged particles had stopped.

When the position of the metal plate was changed, the intensity of the bombardment changed. When, instead of a plate, a metal cylinder was placed in the flask, located around the negative contact of the filament without contact with it, the galvanometer recorded the highest current.

It became apparent to Fleming that the metal cylinder was "capturing" the charged particles emitted by the filament. Having thoroughly studied the properties of the effect, he found that the combination of a filament and a plate, called an anode, could be used as a rectifier of alternating currents not only of industrial, but also of high frequency used in radio.

Fleming's work at Marconi's company allowed him to thoroughly familiarize himself with the whimsical coherer used as a wave sensor. In search of a better sensor, he tried to develop chemical detectors, but at some time the thought came to him: "Why not try a lamp?"

Fleming described his experiment as follows:

“It was about 5 pm when the apparatus was finished. Of course, I really wanted to test it in action. In the laboratory, we set up these two circuits at some distance from each other, and I started the oscillations in the main circuit. To my delight, I saw that the arrow galvanometer showed a stable constant current. I realized that we have received in this specific form of an electric lamp, a solution to the problem of rectifying high-frequency currents. The 'missing piece' in the radio was found and it was an electric lamp! "

First, he assembled an oscillating circuit, with two Leyden banks in a wooden case and an induction coil. Then another circuit that included a vacuum tube and a galvanometer. Both circuits were tuned to the same frequency.

I immediately realized that the metal plate had to be replaced with a metal cylinder covering the entire filament in order to "collect" all the emitted electrons.

I had a variety of metal cylinder carbon incandescent lamps available and began using them as high frequency rectifiers for radiotelegraph communications.

I called this device an oscillating lamp. It was immediately put to use. Galvanometer replaced with an ordinary telephone. A replacement that could have been made at a time in the light of the advancement of technology when spark communication systems were widely used. As such, my lamp was widely used by Marconi as a wave sensor. On November 16, 1904, I applied for a patent in Great Britain.

Fleming received numerous honors and awards for his invention of the vacuum diode. In March 1929 he was knighted for "invaluable contributions to science and industry."

International decimal system measurements, which is based on the use of units such as kilograms and meters, is called metric... Various options metric system developed and used over the past two hundred years, and the differences between them consisted mainly in the choice of basic, basic units. At the moment, the so-called International system of units (SI). The elements that are used in it are identical all over the world, although there are differences in some details. International system of units very widely and actively used all over the world, both in everyday life and in scientific research.

Presently Metric system of measures used in most countries in the world. There are, however, several large states that still use the English system of units based on units such as pound, foot and second. These include the UK, USA and Canada. However, these countries have also already adopted several legislative measures aimed at moving towards Metric units.

She herself originated in the middle of the 18th century in France. It was then that scientists decided what should be created system of measures, which will be based on units taken from nature. The essence of such an approach was that they always remain unchanged, and therefore the entire system as a whole will be stable.

Measures of length

1 kilometer (km) = 1000 meters (m)
1 meter (m) = 10 decimeters (dm) = 100 centimeters (cm)
1 decimeter (dm) = 10 centimeters (cm)
1 centimeter (cm) = 10 millimeters (mm)

Area measures

1 sq. kilometer (km 2) = 1,000,000 sq. meters (m 2)
1 sq. meter (m 2) = 100 sq. decimeters (dm 2) = 10,000 sq. centimeters (cm 2)
1 hectare (ha) = 100 aram (a) = 10,000 sq. meters (m 2)
1 ar (a) = 100 sq. meters (m 2)

Volume measures

1 cubic meter meter (m 3) = 1000 cubic meters decimeters (dm 3) = 1,000,000 cubic meters. centimeters (cm 3)
1 cubic meter decimeter (dm 3) = 1000 cubic meters. centimeters (cm 3)
1 liter (l) = 1 cu. decimeter (dm 3)
1 hectoliter (hl) = 100 liters (l)

Weights

1 ton (t) = 1000 kilograms (kg)
1 centner (q) = 100 kilograms (kg)
1 kilogram (kg) = 1000 grams (g)
1 gram (g) = 1000 milligrams (mg)

Metric system of measures

It should be noted that the metric system of measure was not immediately recognized. As for Russia, in our country it was allowed to be used after it signed Metric convention... Moreover, this system of measures for a long time it was used in parallel with the national one, which was based on such units as pound, fathom and bucket.

Some old Russian measures

Measures of length

1 verst = 500 yards = 1500 yards = 3500 feet = 1066.8 m
1 fathom = 3 yards = 48 vershoks = 7 feet = 84 inches = 2.1336 m
1 arshin = 16 vershoks = 71.12 cm
1 vershok = 4.450 cm
1 foot = 12 inches = 0.3048 m
1inch = 2.540cm
1 nautical mile = 1852.2 m

Weights

1 pood = 40 lbs = 16.380 kg
1 lb = 0.40951 kg

The main difference Metric units from those that were used earlier, is that it uses an ordered set of units of measurement. This means that any physical quantity is characterized by a certain main unit, and all sub-multiples and multiples are formed according to a single standard, namely, using decimal prefixes.

The introduction of this system of measures eliminates the inconvenience to which the abundance of different units of measurement, which have rather complex rules for transforming each other, previously led. Those in metric system are very simple and boil down to the fact that the original value is multiplied or divided by a power of 10.

Rice. 148. Manufacturing of a blocking capacitor, and - collected sheets of foil and paper; below is a view of the relative position of the foil leaves; b - the ends of the foil leaves are bent outward;

with - a brass sheet holder for clamping the ends of the foil; d - finished capacitor

3. CONVERSION TABLES OF MEASURES OF DIFFERENT SYSTEMS

As we said earlier, in our presentation we tried to adhere to the currently adopted metric system of measures. However, in those cases where the old Russian or English measures have not yet become obsolete in the sale of certain types of materials, we provided data on these measures as well.

In case any of the readers still have to translate metric measures into Russian, or, with a more complete establishment of the metric system in our country, the old measures placed in the text into metric ones, we give the following tables covering all the data found in the previous ones. chapters.

Comparison of metric and Russian measures

A. Comparison of metric and Russian measures.

		kilometers	kilometer



	0.7112 meters

	44.45 mm

hundredth soot.		millimeter		46.87 are

	30.48 centimeters

	2.54 centimeters





sq. verst		square kilometers	sq. kilometer		sq. versts

		sq. meters

sq. arshin		sq. meters

	19.7580 sq. centimeters

	929,013 sq. centimeters

		sq. centimeters		0.155 sq. inch



tithe		hectares			tithes

	2197 sq. soot.