Великий физик Исаак Ньютон - Студенческий научный форум

XI Международная студенческая научная конференция Студенческий научный форум - 2019

Великий физик Исаак Ньютон

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Isaac Newton is a talented English physicist, a famous mathematician, a famous astronomer and a genius in mechanics, one of the legendary creators of basic, classical physics, an honorary member, and then the president of the Royal Society of London.

Father - Isaac Newton, a wealthy farmer, who died before the birth of his son. Mother - Anna Eiskou, after the death of her husband, married again and abandoned her son's upbringing. The future scientist was born so painful that his relatives believed that he would not survive, but Isaac lived to a great age. Anna had three more children, but already from the second marriage. Isaac dealt exclusively with her brother, William Eskou.

While studying at Grantham School, Newton discovered outstanding abilities that were noticed by teachers. His mother took him out of school, trying to make him a farmer, but her attempts were in vain. Under the pressure of her brother and teachers, Anna allowed Isaac to finish school. After that, he successfully entered Trinity College, University of Cambridge.

While studying in college, Newton is trying to solve from a scientific point of view those phenomena in the outside world that have not been explained. He is seriously interested in mathematics and at the age of 21 he displays binomial decomposition of an arbitrary rational index and receives a bachelor's degree.

In 1665, the plague was declared in England. Quarantine lasted two years, and Newton, having left college, completely devoted himself to science. During these years, the famous law of world wide discovery was discovered, with which the legend of the physics of an apple falling on its head is connected. When the plague subsided, Isaac returned to Cambridge, where he received a master's degree.

Continuing mathematical research, he becomes a professor of mathematics in college. During these years he was engaged in the study of optics and created a reflecting telescope, which received wide popularity, as it allowed to calculate more accurate time on celestial bodies and helped sailors in navigation. This invention was for Newton a pass to the Royal Society, of which he was elected an honorary member.

Newton is in correspondence with Leibniz, arguing with the great minds of the time about the nature of light. In 1677 a fire broke out in Newton's house, which destroyed part of the scientific works of the physicist. In 1679, the mother of a scientist died after an illness.

Newton was able to summarize his scientific research in the book “Mathematical Principles of Natural Philosophy”, in which he explained the basic concepts of mechanics, introduced new physical quantities (mass, amount of motion, external force), formulated the laws of mechanics, concluded the law of Kepler, described parabolic and hyperbolic orbits of celestial bodies and expressed his views on the Copernican heliocentric system.

Isaac Newton took part in the public life of England: in 1689 he was elected to parliament. The beginning of the 90s were marked by a serious illness, general fatigue and a break in scientific activities.

In 1696, he became the caretaker of the Mint in London, and from 1699 his manager. In this position, Newton did a lot of good for the state: he became the initiator of monetary reform and actively fought counterfeiters.

In 1703, Newton became president of the Royal Society, being by that time already recognized and reputable scientist. He publishes "Optics", becomes a knight, continues his scientific research. Shortly before death, he becomes a member of the money scam and loses most of his fortune.

Newton did not leave descendants after himself, since he never married: he devoted all his free time to science, and his ordinary, gray appearance

made him inconspicuous to women. Biographers mention only one sympathy that flashed in Newton's youth: while studying in Grantham, he was in love with Miss Storey, his contemporaries, with whom he maintained warm, friendly relations until the end of his days.

In recent years, Newton spent in Kensington, where he died in a dream on March 31, 1727. Scientist buried in Westminster Abbey.

It was Newton who laid out the rainbow into seven colors. Moreover, he initially lost sight of orange and blue, but then he equalized the number of shades with the number of basic tones in the musical scale.

The great scientist was not afraid to experiment on himself. Proving that a person sees the world as a result of pressure on the retina of light, Newton, with a thin probe, pressed himself to the bottom of the eyeball, almost losing his eye. Fortunately, the eye remained unscathed, and the colored circles, which the physicist saw at the same time, proved the hypothesis put forward by him.

Newton was respected, and was an honorary member of the English House of Lords for years. He did not skip the meetings, but never spoke to them. When the third year of this social ministry went, Isaac Newton suddenly stood up and asked for the floor. Everyone was amazed - there was a dead silence in the ward. A physicist tired voice asked just close the window.

In his absentmindedness, Newton can equal only with Albert Einstein. Once he decided to boil an egg for himself, but instead he put his pocket watch in boiling water. Moreover, the physicist noticed the error only after 2 minutes, when it was necessary to pull out the "egg".

Newton owns one of the prophecies of the second coming of Christ: he called the year 2060.

With the work of Newton is associated a new era in physics and mathematics. He completed the creation of theoretical physics begun by Galileo, based, on the one hand, on experimental data, and on the other, on a quantitative-mathematical description of nature. In mathematics there are powerful analytical methods. In physics, the main method of studying nature becomes the construction of adequate mathematical models of natural processes and the intensive study of these models with the systematic involvement of the entire power of the new mathematical apparatus. Subsequent centuries proved the exceptional fruitfulness of this approach.

Newton resolutely rejected the approach of Descartes and his Cartesian followers, which was popular at the end of the 17th century, and who, when building a scientific theory at first with “insight of the mind,” found the “root causes” of the phenomenon under investigation. In practice, this approach often led to the development of contrived hypotheses about "substances" and "hidden properties" that are not amenable to experimental testing. Newton believed that in "natural philosophy" (that is, physics), only such assumptions are permissible ("principles", now prefer the name "laws of nature"), which directly follow from reliable experiments, summarize their results; he called hypotheses assumptions that were not sufficiently substantiated by experiments. “Everything ... that is not derived from phenomena should be called a hypothesis; the hypotheses of metaphysical, physical, mechanical, hidden properties have no place in experimental philosophy. ” Examples of principles are the law of the law and the three laws of mechanics in the "Principles" the word “principles” (Principia Mathematica, traditionally translated as “mathematical principles”) is also contained in the title of its main book.

In a letter to Pardis, Newton formulated the “golden rule of science”:

The best and safest method of philosophizing, it seems to me, must first be a diligent study of the properties of things and the establishment of these properties through experimentation, and then a gradual movement towards hypotheses explaining these properties. Hypotheses can be useful only in explaining the properties of things, but there is no need to charge them with the responsibility to determine these properties outside the limits revealed by experiment ... after all, many hypotheses can be devised explaining any new difficulties.

Such an approach not only placed speculative fantasies outside of science (for example, Cartezian’s reasoning about the properties of “subtle matters” that supposedly explain electromagnetic phenomena), but was more flexible and fruitful because it allowed mathematical modeling of phenomena for which the root causes had not yet been discovered. This happened with the theory of light - their nature cleared up much later, which did not interfere with the successful centuries-old use of Newtonian models.

The famous phrase “I do not invent hypotheses” (Latin Hypotheses non fingo), of course, does not mean that Newton underestimated the importance of finding “root causes”, if they are unequivocally confirmed by experience. Experimental general principles and the consequences of them must also pass an experimental test, which may lead to an adjustment or even a change of principles. "The whole difficulty of physics ... consists in recognizing the forces of nature by the phenomena of motion, and then explaining the other phenomena by these forces."

Newton, like Galileo, believed that the basis of all processes of nature is mechanical motion:

It would be desirable to deduce from the beginnings of mechanics and other natural phenomena ... for much leads me to assume that all these phenomena are caused by certain forces with which particles of bodies, due to reasons as far as unknown, either tend to each other and interlock in regular figures, or mutually repel and move away from each other. Since these forces are unknown, so far the attempts of philosophers to explain the phenomena of nature have remained fruitless.

Newton formulated his scientific method in the book “Optics”:

Both in mathematics and in the testing of nature, in the study of difficult questions, the analytical method must precede the synthetic. This analysis is that from experiments and observations by induction they draw general conclusions and do not allow any objections against them that would not have come from experiments or other reliable truths. For hypotheses are not considered in experimental philosophy. Although the results obtained through induction from experiments and observations cannot yet serve as evidence of universal conclusions, it is still the best way to draw conclusions that the nature of things allows.

In the third book, "The Beginning" (since the 2nd edition), Newton put a number of methodological rules against the Cartesians; the first of these is the variant of Occam's razor:

Rule I. There should be no other reasons in nature beyond those that are true and sufficient to explain phenomena ... nature does nothing in vain, but it would be in vain for many to do what can be done less. Nature is simple and does not luxuriate with unnecessary causes of things ...

Rule IV. In experimental physics, sentences derived from occurring phenomena with the help of guidance [induction], despite the possibility of nasty assumptions, should be honored for being true or accurate, or approximately, until such phenomena are found that will further refine them or turn out to be exceptions.

Newton's mechanistic views turned out to be wrong — not all natural phenomena stem from mechanical motion. However, his scientific method was established in science. Modern physics successfully explores and applies phenomena whose nature has not yet been clarified (for example, elementary particles). Beginning with Newton, natural science develops, firmly convinced that the world is knowable, because nature is organized according to simple mathematical principles. This confidence became the philosophical base for the tremendous progress of science and technology.

The merit of Newton is the solution of two fundamental problems.

• Creating an axiomatic basis for mechanics, which actually translated this science into the category of rigorous mathematical theories.

Creation of dynamics linking body behavior with characteristics of external influences on it (forces).

In addition, Newton finally buried the notion that had taken root from ancient times that the laws of motion of earthly and celestial bodies are completely different. In his model of the world, the entire Universe is subject to uniform laws that allow mathematical formulation.

Newton's axiomatics consisted of three laws, which he himself formulated in the following form.

Newton's first law

Every body continues to be kept in a state of rest or a uniform and rectilinear motion, until and because it is not forced by the applied forces to change this state.

Newton's Second Law

In the inertial reference system, the acceleration that the material point receives is directly proportional to the resultant of all forces applied to it and inversely proportional to its mass.

The change in the amount of motion is proportional to the applied driving force and occurs in the direction of the straight line along which this force acts.

Newton's third law

There is always an equal and opposite reaction to action, otherwise, the interactions of two bodies on each other are equal and directed in opposite directions.

Some contemporaries of Newton considered him an alchemist. He was the director of the Mint, established a monetary business in England, headed the Prior-Zion society, and studied the chronology of the ancient kingdoms. Several theological works (mostly unpublished) devoted to the interpretation of biblical prophecies.

The first law (the law of inertia), in a less clear form, was published by Galileo. It should be noted that Galileo allowed free movement not only in a straight line, but also along a circle (apparently, from astronomical considerations). Galileo also formulated the most important principle of relativity, which Newton did not include in his axiomatics, because for mechanical processes this principle is a direct consequence of the equations of dynamics (a consequence of V in the Principles). In addition, Newton considered space and time to be absolute concepts, the same for the whole Universe, and clearly indicated this in his "Beginnings".

Newton also gave rigorous definitions of such physical concepts as the amount of motion (not quite clearly used by Descartes) and strength. He introduced to physics the concept of mass as a measure of inertia and, at the same time, gravitational properties. Previously, physicists used the concept of weight, but the weight of the body depends not only on the body itself, but also on its environment (for example, on the distance to the center of the Earth), so a new, invariant characteristic was needed.

Completed mathematization mechanics Euler and Lagrange.

Aristotle and his supporters considered the gravity of the desire of the bodies of the "sublunary world" to their natural places. Some other ancient philosophers (among them Empedocles, Plato) considered the severity of the desire of related bodies to join. In the XVI century, this view was supported by Nicolaus Copernicus, in whose heliocentric system the Earth was considered only one of the planets. Close views were held by Giordano Bruno, Galileo Galilei. Johann Kepler believed that the cause of the fall of the bodies is not their inner aspirations, but the force of attraction from the Earth, and not only the Earth attracts the stone, but also the stone attracts the Earth. In his opinion, gravity extends at least to the moon. In his later works, he expressed the view that gravity decreases with distance and mutual attraction of all the bodies of the solar system. The physical nature of gravity tried to unravel Rene Descartes, Gilles Roberval, Christian Huygens and other scientists of the XVII century.

The same Kepler first suggested that the movement of the planets is controlled by forces emanating from the sun. In his theory there were three such forces: one, circular, pushes the planet in orbit, acting tangentially to the trajectory (due to this force, the planet moves), the other attracts or pushes the planet away from the Sun (due to the planet’s orbit is an ellipse) and the third acts across the ecliptic plane (thanks to which the orbit of the planet lies in the same plane). He considered a circular force to decrease inversely proportional to the distance from the Sun. None of these three forces were identified with gravity. Keplerov's theory was rejected by the leading astronomer-theoretician of the mid-seventeenth century, Ismael Bulliald, who believed, firstly, the planets move around the Sun not under the influence of the forces emanating from it, but because of internal aspiration, and , it would fall back to the second degree of distance, and not the first, as Kepler believed. Descartes believed that the planets are transported around the sun by gigantic whirlwinds.

The assumption about the existence of the force emanating from the Sun, which controls the movement of the planets, was expressed by Jeremy Horrocks. According to Giovanni Alfonso Borelli, three forces emanate from the Sun: one advances the planet in orbit, the other attracts the planet to the Sun, the third (centrifugal), on the contrary, pushes the planet away. The elliptical orbit of the planet is the result of the confrontation of the last two. In 1666, Robert Hooke suggested that the force of attraction to the Sun alone is enough to explain the movement of the planets, it is just necessary to assume that the planetary orbit is the result of a combination (superposition) of falling on the Sun (due to the force of attraction) tangent to the trajectory of the planet). In his opinion, this superposition of movements determines the elliptical form of the trajectory of the planet around the Sun. Close views, but in a rather vague form, expressed by Christopher Rehn. Hooke and Ren guessed that the strength of the force decreases inversely with the square of the distance to the Sun.

However, no one before Newton was able to clearly and mathematically conclusively relate the law of aggression (the force inversely proportional to the square of the distance) and the laws of motion of the planets (the laws of Kepler). Moreover, it was Newton who first realized that gravity acts between any two bodies in the Universe; the motion of a falling apple and the rotation of the moon around the earth are controlled by the same force. Finally, Newton did not just publish the proposed formula of the law of world wideness, but in fact proposed a holistic mathematical model:

law of aggression;

the law of motion (Newton's second law);

system of methods for mathematical research (mathematical analysis).

Together, this triad is sufficient to fully explore the most complex movements of celestial bodies, thereby creating the foundations of celestial mechanics. Thus, it is only with the works of Newton that the science of dynamics begins, including when applied to the movement of celestial bodies. Prior to the creation of the theory of relativity and quantum mechanics, no fundamental amendments to this model were needed, although it turned out that the mathematical apparatus needed to be significantly developed.

The first argument in favor of the Newtonian model was the rigorous conclusion on its basis of Kepler’s empirical laws. The next step was the theory of the motion of comets and the moon, set out in the "Principles". Later, with the help of Newtonian, all the observed movements of celestial bodies were explained with high accuracy; in this great merit of Euler, Klero and Laplace, who developed for this perturbation theory. The foundation of this theory was laid by Newton, who analyzed the motion of the moon, using his usual method of decomposition in a series; on this path, he discovered the causes of the then known irregularities (inequalities) in the motion of the moon.

The law allowed to solve not only the problems of celestial mechanics, but also a number of physical and astrophysical problems. Newton indicated a method for determining the mass of the Sun and the planets. He discovered the cause of the tides: the attraction of the moon (even Galileo considered the tides to be a centrifugal effect). Moreover, after processing the long-term data on the height of tides, he calculated the mass of the Moon with good accuracy. Another consequence of the precession was the earth axis. Newton found out that due to the flattening of the Earth at the poles, the earth's axis under the action of the attraction of the Moon and the Sun makes a constant slow displacement with a period of 26,000 years. Thus, the ancient problem of “anticipation of the equinoxes” (first noted by Hipparch) found a scientific explanation.

The Newtonian theory of agony caused long-term debates and criticism of the long-range concept adopted in it. However, the outstanding successes of celestial mechanics in the 18th century approved the opinion of the adequacy of the Newtonian model. The first observed deviations from Newton's theory in astronomy (the displacement of the perihelion of Mercury) were discovered only 200 years later. Soon these deviations were explained by the general theory of relativity (GTR); Newtonian theory turned out to be its approximate version. GR also filled the theory of physical content, indicating the material carrier of gravity - the metric of space-time, and allowed to get rid of long-range action.

Newton owns the fundamental discoveries in optics. He built the first mirror telescope (reflector), which, unlike pure lens telescopes, lacked chromatic aberration. He also investigated the dispersion of light in detail, showed that when white light passes through a transparent prism, it decomposes into a continuous series of rays of different colors due to different refractions of rays of different colors, thereby Newton laid the foundations of the correct theory of colors. Newton created the mathematical theory of the open Hwinkofferferencing rings, which have since received the name "Newton's rings". In a letter to Flemsteed, he outlined a detailed theory of astronomical refraction. But his main achievement is the creation of the foundations of physical (not only geometric) optics as a science and the development of its mathematical base, the transformation of the theory of light from an unsystematic set of facts into a science with a rich qualitative and quantitative content that is experimentally well founded. Newton's optical experiments for decades have become a model of deep physical research.

During this period there were many speculative theories of light and chromaticity; Aristotle’s point of view (“different colors are a mixture of light and dark in different proportions”) and Descartes (“different colors are created when light particles rotate at different speeds”) basically struggled. Hooke in his "Micrograph" (1665) proposed a variant of Aristotelian views. Many believed that color is an attribute not of light, but of an illuminated object. General discord exacerbated the cascade of discoveries of the 17th century: diffraction (1665, Grimaldi), interference (1665, Hook), double refraction (1670, Erasmus Bartolin, studied by Huygens), light velocity estimation (1675, Römer). A theory of light compatible with all these facts did not exist.

In his speech to the Royal Society, Newton refuted both Aristotle and Descartes, and convincingly proved that the white light is not primary, but consists of colored components with different “degrees of refraction”. These components are primary - no tricks Newton could change their color. Thus, the subjective sense of color received a solid objective base - in modern terminology, the wavelength of light, which could be judged by the degree of refraction.

In 1689, Newton stopped publishing in the field of optics (although he continued research) - according to a popular legend, he vowed not to print anything in this area during Hooke’s life. In any case, in 1704, the next year after Hooke’s death, the monograph “Optics” was published (in English). The preface to it contains an obvious hint of a conflict with Hooke: "Not wanting to be drawn into disputes on various issues, I would have delayed this publication and would have delayed it further, if not for the persistence of my friends." During the life of the author, “Optics”, like “Nachalo”, sustained three editions (1704, 1717, 1721) and many translations, including three in Latin.

Book One: the principles of geometric optics, the theory of the dispersion of light and the composition of white with various applications, including the rainbow theory.

Book Two: the interference of light in thin plates.

Book Three: diffraction and polarization of light.

Historians identify two groups of the then hypotheses about the nature of light.

Emission (corpuscular): light consists of small particles (corpuscles) emitted by a luminous body. The straightness of the propagation of light, on which geometric optics is based, spoke in favor of this opinion, but diffraction and interference did not fit well into this theory.

Wave: light is a wave in the invisible world ether. Opponents of Newton (Hooke, Huygens) are often called supporters of the wave theory, but it must be borne in mind that under the wave they meant not a periodic oscillation, as in modern theory, but a single impulse; for this reason, their explanations of light phenomena were a little believable and could not compete with Newtonian (Huygens even tried to refute the diffraction). Developed wave optics appeared only at the beginning of the XIX century.

Newton is often considered a supporter of the corpuscular theory of light; in fact, he, as usual, “did not invent hypotheses” and readily admitted that light could also be associated with waves on the air. In the treatise submitted to the Royal Society in 1675, he writes that light cannot be just vibrations of the ether, since then, for example, it could spread through a bent pipe, as sound does. But, on the other hand, he suggests that the propagation of light excites oscillations in the ether, which causes diffraction and other wave effects. In essence, Newton, clearly aware of the advantages and disadvantages of both approaches, puts forward a compromise wave-wave theory of light. In his works, Newton described in detail the mathematical model of light phenomena, leaving aside the question of the physical medium of light: “My teaching about light refraction and colors consists solely in establishing some properties of light without any hypotheses about its origin.” Wave optics, when it appeared, did not reject Newton’s models, but absorbed them and expanded them on a new basis.

Despite his dislike of hypotheses, Newton placed at the end of Optics a list of unsolved problems and possible answers to them. However, in these years, he could already afford this - the authority of Newton after the "Beginning" became indisputable, and very few people decided to pester him with objections. A number of hypotheses were prophetic. In particular, Newton predicted:

light deflection in the field;

the phenomenon of polarization of light;

interconversion of light and matter.

Newton owns the first conclusion of the speed of sound in gas, based on the Boyle-Mariotte law. He suggested the existence of a law of viscous friction and described the hydrodynamic compression of a jet. He proposed a formula for the law of body resistance in a rarefied medium (Newton's formula) and based on it considered one of the first problems about the most advantageous form of a streamlined body (Newton's aerodynamic problem). In The Beginnings, he expressed and argued the correct assumption that a comet has a solid core, the evaporation of which under the influence of solar heat forms an extensive tail, always directed in the direction opposite to the Sun. Newton also dealt with heat transfer, one of the results is called Newton's law - Richman.

Newton predicted the flattening of the Earth at the poles, estimating it approximately as 1: 230. At the same time, Newton used the model of a homogeneous fluid to describe the Earth, applied the law of world wideness and took into account centrifugal force. At the same time, similar calculations were carried out by Huygens, who did not believe in the long-range force and approached the problem purely kinematically. Accordingly, Huygens predicted more than half the compression than Newton, 1: 576. Moreover, Cassini and other Cartesians argued that the Earth was not compressed, but stretched at the poles like a lemon. Subsequently, though not immediately (the first measurements were inaccurate), direct measurements (Clero, 1743) confirmed Newton’s correctness; real compression is 1: 298. The reason for the difference of this value from the one proposed by Newton in the direction of Huygensovskiy is that the model of a homogeneous fluid is not completely accurate (the density increases noticeably with depth). A more accurate theory, clearly taking into account the dependence of density on depth, was developed only in the XIX century.

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