Lecture
| Comprehensive Science • Natural History | |
| Physics Φυσική  |
|
| Thing studying |
Matter (in the form of matter and fields) and the most common forms of its movement, as well as the fundamental interactions of nature that govern the movement of matter. |
| Period birth |
V century BC. er - XVI century |
Physics (from ancient Greek. Φύσις - nature) is the field of natural science. The science of the simplest and at the same time the most general laws of nature, of matter, its structure and motion. The laws of physics underlie all natural science [1] .
The term "physics" first appeared in the writings of one of the greatest thinkers of antiquity - Aristotle, who lived in the IV century BC. Initially, the terms “physics” and “philosophy” were synonymous, since both disciplines were based on the desire to explain the laws of the functioning of the Universe. However, as a result of the scientific revolution of the 16th century, physics became a separate scientific field.
The word “physics” was introduced into Russian by M. V. Lomonosov, who published the first physics textbook in Russia - his own translation from German of the textbook Wolffian Experimental Physics by H. Wolf (1746). The first original textbook of physics in Russian was the course “Brief outline of physics” (1810), written by P. I. Insurance.
In the modern world, the importance of physics is extremely high. All that distinguishes modern society from the society of the past centuries was the result of the practical application of physical discoveries. Thus, research in the field of electromagnetism led to the emergence of telephones and, later, mobile telephones, discoveries in thermodynamics allowed the creation of automobiles, the development of electronics led to the advent of computers.
The physical understanding of the processes occurring in nature is constantly evolving. Most of the new discoveries will soon receive application in engineering and industry. However, new research is constantly raising new puzzles and discovering phenomena that require new physical theories to explain. Despite the enormous amount of accumulated knowledge, modern physics is still very far from explaining all the phenomena of nature.
The general scientific foundations of physical methods are developed in the theory of knowledge and the methodology of science.
Physics is the science of nature (natural science) in the most general sense (part of natural history). The subject of its study is the matter (in the form of matter and fields) and the most common forms of its movement, as well as the fundamental interactions of nature that govern the movement of matter.
Some patterns are common to all material systems, for example, energy conservation — they are called physical laws. Physics is sometimes called “fundamental science,” since other natural sciences (biology, geology, chemistry, etc.) describe only a certain class of material systems that obey the laws of physics. For example, chemistry studies the atoms, the substances formed from them and the transformations of one substance into another. The chemical properties of a substance are unambiguously determined by the physical properties of atoms and molecules, described in such branches of physics as thermodynamics, electromagnetism, and quantum physics.
Physics is closely related to mathematics: mathematics provides an apparatus with which physical laws can be precisely formulated. Physical theories are almost always formulated in the form of mathematical expressions, and more complex sections of mathematics are used than is usually used in other sciences. Conversely, the development of many areas of mathematics was stimulated by the needs of physical theories.
Physics is a natural science. It is based on an experimental study of natural phenomena, and its task is the formulation of the laws by which these phenomena are explained. Physics focuses on the study of fundamental and elementary phenomena and on answers to simple questions: what does matter consist of, how do particles of matter interact with each other, according to what rules and laws does particles move, etc.
Physical research is based on observations . The generalization of observations allows physicists to formulate hypotheses about the joint general features of these phenomena, according to which observations were made. Hypotheses are verified by means of a thought-out experiment in which the phenomenon would manifest itself in the purest possible form and would not be complicated by other phenomena. Analysis of data from a set of experiments allows us to formulate a pattern . In the early stages of research, patterns are mostly empirical, phenomenological in nature, that is, the phenomenon is described quantitatively using certain parameters characteristic of the bodies and substances under study. Analyzing the laws and parameters, physicists build physical theories that allow one to explain the phenomena being studied on the basis of ideas about the structure of bodies and substances and the interaction between their constituent parts. Physical theories, in turn, create the prerequisites for the formulation of exact experiments, during which the framework for their application is mainly determined. General physical theories allow the formulation of physical laws, which are considered common truths, until the accumulation of new experimental results requires their specification.
So, for example, Stephen Gray noticed that electricity can be transmitted for a fairly considerable distance with the help of moistened threads and began to investigate this phenomenon. Georg Ohm managed to find a quantitative pattern for him - the current in the conductor is proportional to the voltage (Ohm's law). At the same time, of course, Ohm’s experiments relied on new power sources and on new ways to measure the effect of electric current, which made it possible to quantitatively characterize it. According to the results of further research, it was possible to abstract from the shape and length of the conductors and introduce such phenomenological characteristics as the specific resistance of the conductor and the internal resistance of the power source. Ohm's law is still the basis of electrical engineering, but research has also established the scope of its application - they discovered elements of an electrical circuit with non-linear current-voltage characteristics, as well as substances that do not have electrical resistance — superconductors. After the discovery of charged microscopic particles - electrons, a microscopic theory of electrical conductivity was formulated, explaining the dependences of resistance on temperature by means of electron scattering on crystal lattice ***, impurities, etc.
However, it would be wrong to assume that only an empirical approach determines the development of physics. Many important discoveries were made “at the tip of the pen,” or through experimental verification of theoretical hypotheses. For example, the principle of least action Pierre Louis de Maupertuis formulated in 1744 on the basis of general considerations, and its validity cannot be established experimentally by virtue of the universality of the principle. Currently, classical and quantum mechanics, field theory are based on the principle of least action. In 1899, Max Planck introduced the concepts of a quantum of an electromagnetic field, a quantum of action, which was also not the result of observations and experiments, but a purely theoretical assumption. In 1905, Albert Einstein published the work of the special theory of relativity, built by deductive means from the most general physical and geometric considerations. Henri Poincaré, a mathematician who was well versed in the scientific methods of physics, wrote that neither the phenomenological nor the speculative approach separately describes and can not describe physical science [2] .
Physics is quantitative science. The physical experiment relies on measurements, that is, a comparison of the characteristics of the phenomena studied with certain standards. To this end, physics has developed a set of physical units and measuring instruments. Separate physical units are combined into systems of physical units. Thus, at the present stage of development of science, the international system is the SI system, but most theorists still prefer to use the Gaussian system of units.
The experimentally obtained quantitative dependences make it possible to use mathematical methods for their processing and to construct theoretical, that is, mathematical models of the phenomena under study.
With a change in the understanding of the nature of certain phenomena, the physical units in which physical quantities are measured also change. For example, to measure the temperature, at first arbitrary temperature scales were proposed, which divided the temperature gap between characteristic phenomena (for example, freezing and boiling of water) into a certain number of smaller intervals, which were called temperature degrees. To measure the amount of heat was introduced unit - calorie, which determined the amount of heat needed to heat a gram of water by one degree. However, over time, physicists have established a correspondence between the mechanical and thermal form of energy. Thus, it turned out that the previously proposed unit of quantity of heat, calorie, is superfluous, as is the unit of measurement of temperature. And the amount of heat and temperature can be measured in units of mechanical energy. In the modern era, calories and degrees have not gone out of practical use, but there is an exact numerical relationship between these quantities and the unit of energy of Joule. Degree, as a unit of measurement of temperature is included in the SI system, and the transition coefficient from temperature to energy values — the Boltzmann constant — is considered a physical constant.
Physics is the science of matter, its properties and motion. It is one of the most ancient scientific disciplines. People tried to understand the properties of matter from ancient times: why bodies fall to the ground, why different substances have different properties, etc. People were also interested in the structure of the world, on the nature of the Sun and the Moon. At first they tried to look for answers to these questions in philosophy. Mostly philosophical theories that tried to give answers to such questions were not tested in practice. However, in spite of the fact that often philosophical theories incorrectly described observations, even in ancient times, mankind achieved considerable success in astronomy, and the great Greek scientist Archimedes even managed to give precise quantitative formulations of many laws of mechanics and hydrostatics.
Some theories of ancient thinkers, such as the ideas about atoms that were formulated in ancient Greece and India, were ahead of their time. Gradually, natural science began to secede from general philosophy, the most important part of which was physics. Already Aristotle used the name "Physics" in the title of one of his main treatises [3] . Despite a number of incorrect statements, the physicist Aristotle for centuries remained the basis of knowledge about nature.
The ability of humanity to doubt and revise the provisions that were previously considered the only true, in search of answers to new questions eventually led to an era of great scientific discoveries, which today is called the scientific revolution, which began in the middle of the XVI century. The prerequisites for these fundamental changes were formed thanks to the heritage of ancient thinkers, whose heritage can be traced back to India and Persia. These include elliptical models [ source not specified for 353 days ] of planetary orbits, based on the heliocentric model of the Solar System, developed by the Indian mathematician and astronomer Aryabhata, the basic principles of atomism proposed by Hindu and Jain philosophers, the theory of Buddhist thinkers Dignagi and Dharmakirti about is equivalent to energy particles, the optical theory of the Arab scientist Ibn al-Haytham ( Alhazen ). The Persian scientist Nasir ad-Din al-Tusi pointed out the significant shortcomings of the Ptolemaic system.
Medieval Europe for some time lost its knowledge of ancient times, but under the influence of the Arab Caliphate, the works of Aristotle saved by the Arabs returned. In the XII-XIII centuries, the works of Indian and Persian scientists found their way to Europe. In the Middle Ages, the scientific method began to take shape, in which the main role was played by experiments and mathematical description. Ibn al-Haytham is considered [by whom? ] the founder of the scientific method. In his Book on Optics, written in 1021, he described experiments designed to prove the validity of his theory of vision, which argued that the eye perceives light emitted by other objects, rather than the eye itself, emitting light, as previously believed Euclid and Ptolemy. In the experiments of Ibn al-Haysam, a camera obscura was used. With the help of this device, he tested his hypotheses regarding the properties of light: either the light propagates in a straight line, or various rays of light are mixed in the air.
The period of the scientific revolution is characterized by the approval of the scientific method of research, the isolation of physics from the mass of natural philosophy into a separate area and the development of individual branches of physics: mechanics, optics, thermodynamics, etc.
Most historians are of the opinion that the scientific revolution began in 1543, when the first printed copy of his book On the Rotation of the Celestial Spheres was brought from Nuremberg to Nicholas Copernicus.
After that, for about a hundred years, mankind has been enriched with the work of researchers such as Galileo Galilei, Christian Huygens, Johann Kepler, Blaise Pascal, and others. Galileo was the first to consistently apply the scientific method, conducting experiments to confirm his assumptions and theories. He formulated some laws of dynamics and kinematics, in particular the law of inertia, and verified them experimentally. In 1687, Isaac Newton published a book, Principia, in which he described in detail two basic physical theories: the laws of motion of bodies, known as Newton's laws, and the laws of motion. Both theories were in excellent agreement with the experiment. The book also cited the theory of fluid motion. Subsequently, classical mechanics was reformulated and expanded by Leonard Euler, Joseph Louis Lagrange, William Rowan Hamilton and others. The laws of gravity laid the foundation for what later became astrophysics, which uses physical theories to describe and explain astronomical observations. In Russia, Lomonosov was the first to make a significant contribution to the development of physical mineralogy, mathematical physics, biophysics and astronomy, in the section of the northern lights, physics of the “tails” of comets. Among the most significant scientific achievements of Lomonosov in the field of physics is his atomic-corpuscular theory of the structure of matter and matter. The works of Lomonosov and his associate G.V. Richman made an important contribution to understanding the electrical nature of thunderstorm discharges. Lomonosov not only conducted a brilliant long-term study of atmospheric electricity and established a number of empirical regularities of thunderstorm phenomena, but also in The Word about Air Phenomena, Electric Power Occurring (1753), explained the cause of the appearance of electricity in thunder clouds by convection of warm air (at the Earth’s surface) and cold air (in the upper atmosphere). Lomonosov developed the theory of light and advanced a three-component color theory, with which he explained the physiological mechanisms of color phenomena. According to Lomonosov, colors are caused by the action of three kinds of ether and three types of color-sensing matter, which forms the bottom of the eye. The theory of color and color vision, which Lomonosov made in 1756, stood the test of time and took its rightful place in the history of physical optics. After establishing the laws of mechanics by Newton, electricity became the next research field. The foundations of the creation of the theory of electricity laid the observations and experiments of such scientists of the XVII and XVIII centuries, like Robert Boyle, Stephen Gray, Benjamin Franklin. The basic concepts were formed - electric charge and electric current. In 1831, English physicist Michael Faraday showed the connection between electricity and magnetism, demonstrating that a moving magnet induces a current in an electrical circuit.Based on this concept, James Clerk Maxwell built the theory of the electromagnetic field. From the system of Maxwell's equations followed the existence of electromagnetic waves propagating at the speed of light. Experimental confirmation of this was found by Heinrich Hertz, having opened radio waves.
With the construction of the theory of the electromagnetic field and electromagnetic waves, the victory of the wave theory of light, founded by Huygens, over Newton's corpuscular theory, the construction of classical optics was completed. On this path, optics have been enriched with an understanding of the diffraction and interference of light, achieved through the work of Augustin Fresnel and Thomas Young.
В XVIII и начале XIX века были открыты основные законы поведения газов, а работы Сади Карно по теории тепловых машин открыли новый этап в становлениитермодинамики. В XIX веке Юлиус Майер и Джеймс Джоуль установил эквивалентность механической и тепловой энергий, что привело к расширенной формулировке закона сохранения энергии (первый закон термодинамики). Благодаря Рудольфу Клаузиусу был сформулирован второй закон термодинамики и введено понятиеэнтропии. Позже Джозайя Уиллард Гиббс заложил основы статистической физики, а Людвиг Больцман предложил статистическую интерпретацию понятия энтропии.
By the end of the XIX century, physicists came to a significant discovery - experimental confirmation of the existence of the atom. At this time, the role of physics in society changed significantly. The emergence of new technology (electricity, radio, car, etc.) required a large amount of applied research. Doing science has become a profession. General Electric was the first to open its own research laboratories; the same laboratories began to appear in other firms.
Конец девятнадцатого, начало двадцатого века был временем, когда под давлением новых экспериментальных данных физикам пришлось пересмотреть старые теории и заменить их новыми, заглядывая все глубже в строение материи. Эксперимент Майкельсона — Морли выбил основу из-под ног классического электромагнетизма, поставив под сомнение существование эфира. Были открыты новые явления, такие как рентгеновские лучи и радиоактивность. Не успели физики доказать существование атома, как появились доказательства существования электрона, эксперименты с фотоэффектом и изучение спектра теплового излучения давали результаты, которые невозможно было объяснить, исходя из принципов классической физики. В прессе этот период назывался кризисом физики, но одновременно он стал периодом триумфа физики, сумевшей выработать новые революционные теории, которые не только объяснили непонятные явления, но и многие другие, открыв путь к новому пониманию природы.
In 1905, Albert Einstein built a special theory of relativity, which demonstrated that the concept of ether is not required when explaining electromagnetic phenomena. At the same time, it was necessary to change the classical mechanics of Newton, giving it a new formulation, valid at high speeds. The concepts of the nature of space and time have also changed radically. Einstein developed his theory into the general theory of relativity, published in 1916. The new theory included a description of gravitational phenomena and opened the way to the formation of cosmology - the science of the evolution of the Universe.
Рассматривая задачу о тепловом излучении абсолютно черного тела, Макс Планк в 1900 году предложил невероятную идею, что электромагнитные волны излучаются порциями, энергия которых пропорциональна частоте. Эти порции получили название квантов, а сама идея начала построение новой физической теории — квантовой механики, которая еще больше изменила классическую ньютоновскую механику, на этот раз при очень малых размерах физической системы. В том же 1905-м году Альберт Эйнштейн применил идею Планка для успешного объяснения экспериментов с фотоэффектом, предположив, что электромагнитные волны не только излучаются, но и поглощаются квантами. Корпускулярная теория света, которая, казалось, потерпела сокрушительное поражение в борьбе с волновой теорией, вновь получила поддержку.
Спор между корпускулярной и волновой теорией нашел свое решение в корпускулярно-волновом дуализме, гипотезе, сформулированной Луи де Бройлем. По этой гипотезе не только квант света, а любая другая частица проявляет одновременно свойства, присущие как корпускулам, так и волнам. Гипотеза Луи де Бройля подтвердилась в экспериментах с дифракцией электронов.
В 1911 году Эрнест Резерфорд предложил планетарную теорию атома, а в 1913 году Нильс Бор построил модель атома, в которой постулировал квантовый характер движения электронов. Благодаря работам Вернера Гайзенберга, Эрвина Шредингера, Вольфганга Паули, Поля Дирака и многих других квантовая механика нашла свое точную математическую формулировку, подтверждённую многочисленными экспериментами. В 1927 году была создана копенгагенская интерпретация, которая открывала путь для понимания законов квантового движения на качественном уровне.
With the discovery of radioactivity, Henri Becquerel began the development of nuclear physics, which led to the emergence of new sources of energy: atomic energy and nuclear fusion energy. New particles discovered during nuclear reaction studies: the neutron, proton, neutrino, gave rise to elementary particle physics. These new discoveries at the subatomic level turned out to be very important for physics at the level of the Universe and made it possible to formulate a theory of its evolution - the Big Bang theory.
There was a final division of labor between theoretical physicists and experimental physicists. Enrico Fermi was perhaps the last outstanding physicist, successful both in theory and in experimental work.
Передний край физики переместился в область исследования фундаментальных законов, ставя перед собой цель создать теорию, которая объясняла бы Вселенную, объединив теории фундаментальных взаимодействий. На этом пути физика получила частичные успехи в виде теории электрослабого взаимодействия и теории кварков, обобщённой в так называемой стандартной модели. Однако, квантовая теория гравитации до сих пор не построена. Определенные надежды связываются с теорией струн.
Начиная с создания квантовой механики, быстрыми темпами развивается физика твердого тела, открытия которой привели к возникновению и развитию электроники, а с ней и информатики, которые внесли коренные изменения в культуру человеческого общества.
В основе своей физика — экспериментальная наука: все её законы и теории основываются и опираются на опытные данные. Однако зачастую именно новые теории являются причиной проведения экспериментов и, как результат, лежат в основе новых открытий. Поэтому принято различать экспериментальную и теоретическую физику.
Экспериментальная физика исследует явления природы в заранее подготовленных условиях. В её задачи входит обнаружение ранее неизвестных явлений, подтверждение или опровержение физических теорий. Многие достижения в физике были сделаны благодаря экспериментальному обнаружению явлений, не описываемых существующими теориями. Например, экспериментальное изучение фотоэффекта послужило одной из посылок к созданию квантовой механики (хотя рождением квантовой механики считается появление гипотезы Планка, выдвинутой им для разрешения ультрафиолетовой катастрофы — парадокса классической теоретической физики излучения).
В задачи теоретической физики входит формулирование общих законов природы и объяснение на основе этих законов различных явлений, а также предсказание до сих пор неизвестных явлений. Верность любой физической теории проверяется экспериментально: если результаты эксперимента совпадают с предсказаниями теории, она считается адекватной (достаточно точно описывающей данное явление).
При изучении любого явления экспериментальные и теоретические аспекты одинаково важны.
From its inception, physics has always had a great practical value and developed along with the machines and mechanisms that humanity used for its needs. Physics is widely used in engineering, many physicists were at the same time inventors, and vice versa. Mechanics, as part of physics, is closely related to theoretical mechanics and the resistance of materials, as engineering. Thermodynamics is associated with heat engineering and the design of heat engines. Electricity is associated with electrical engineering and electronics, for the formation and development of which research in the field of solid state physics is very important. The achievements of nuclear physics led to the emergence of nuclear energy, and the like.
Physics also has extensive interdisciplinary communication. On the border of physics, chemistry, and engineering sciences, such a branch of science as material science emerged and is rapidly developing. The methods and tools used by chemistry, which led to the formation of two areas of research: physical chemistry and chemical physics. Biophysics is becoming ever more powerful - a field of research at the border between biology and physics, in which biological processes are studied on the basis of the atomic structure of organic substances. Geophysics studies the physical nature of geological phenomena. Medicine uses methods such as x-ray and ultrasound, nuclear magnetic resonance for diagnostics, lasers for the treatment of eye diseases, nuclear radiation in oncology, and the like.
Although physics deals with a variety of systems, some physical theories are applicable in large areas of physics. Such theories are generally considered correct with additional restrictions. For example, classical mechanics is correct if the sizes of the objects under study are much larger than the sizes of atoms, the speed is substantially less than the speed of light, and the gravitational forces are small. These theories are still being actively investigated; For example, such an aspect of classical mechanics as the theory of chaos was discovered only in the 20th century. They form the basis for all physical research. Within the framework of these theories, M. V. Lomonosov explained the reasons for the state of aggregation of substances (solid, liquid and gaseous states) and developed the theory of heat.
| Theory | Main sections | Concepts |
|---|---|---|
| Classical mechanics | Newton's Laws - Lagrange Mechanics - Hamiltonian Mechanics - Chaos Theory - Hydrodynamics — Geophysical Fluid Dynamics - Continuum Mechanics |
Substance - Space - Time - Energy - Movement - Mass - Length —Speed - Force - Power - Work - Law of Conservation - Moment of Inertia — Corner Moment - Moment of Force - Wave - Action - Dimension |
| Electromagnetism | Electrostatics - Electricity - Magnetostatics — Magnetism — Maxwell Equations — Electrodynamics — Magnetic Hydrodynamics |
Electric charge - Voltage - Current - Electric field - Magnetic field - Electromagnetic field - Electromagnetic radiation |
|
Thermodynamics and Statistical Physics |
Heat Machine - Molecular Kinetic Theory |
Temperature — Boltzmann Constant — Entropy — Free Energy — Thermodynamic Equilibrium — Statistical Sum — Microcanonical Distribution — Large Canonical Distribution |
| Quantum mechanics | Schrödinger Equation - Feynman Integral - Quantum Field Theory |
Hamiltonian - Identical particles - Planck's constant - Measurement - Quantum oscillator - Wave function - Zero energy - Renormalization |
| Theory of relativity | Special Theory of Relativity - General Theory of Relativity - Relativistic Hydrodynamics |
Principle of relativity - 4-vector - Space-time - Speed of light - Energy-momentum tensor - Space-time curvature - Black hole |
A schematic representation of atomization.
Main article: List of physical journals
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Introduction to Physics, Fundamentals
Terms: Introduction to Physics, Fundamentals