Ether (physics)

Antique views

From the few surviving works of ancient Greek scientists one can understand that the ether was then understood as a special celestial substance, “filler of the void” in Cosmos ^[3] . Plato in the dialogue "Time" reports that God created the world from the ether. Lucretius Kar in the poem "On the nature of things" mentions that "the ether feeds the constellations," that is, the luminaries consist of a condensed ether. Anaxagoras represented the ether differently - in his opinion, the ether is similar to the terrestrial air, only more hot, dry and rarefied ^[4] .

Democritus and other atomists did not use the term ether , their world system included only atoms and emptiness ^[5] .

A somewhat more detailed picture is presented in the writings of Aristotle . He also believed that the planets and other celestial bodies consist of ether (or quintessence ), which is the "fifth element" of nature, and, unlike the rest (fire, water, air and earth), is eternal and unchanging. Aristotle wrote: “The sun is not made of fire; it is a huge accumulation of ether; the heat of the sun is caused by its action on the ether during the revolution around the earth ". The ether also fills the entire extraterrestrial Cosmos, beginning with the sphere of the Moon; From the above quotation it can be concluded that the ether of Aristotle transmits light from the sun and stars, as well as heat from the sun. The Aristotelian understanding of the term was adopted by medieval scholastics ; it lasted in science until the XVII century.

Descartes ’ether (17th century)

A detailed hypothesis about the existence of a physical ether was put forward by Rene Descartes in 1618 and was first described in the work Peace, or a Treatise on Light (1634), and later developed and published in Primary Philosophy (1644) ^[2] .

For the first time, Descartes clearly stated that the world ether possesses the usual mechanical properties of matter and revived it in the new physics, thus the notion of ether in the spirit of Anaxagoras (instead of the Aristotelian ether, discredited by this time, as a “heavenly” element). The concept of the world ether in the interpretation of Descartes was maintained until the beginning of the XX century.

In accordance with his ( Cartesian ) natural philosophy, Descartes viewed the entire Universe as indefinitely extended matter, taking various forms under the action of its inherent motion ^[6] .

Descartes denied emptiness and believed that the whole space was filled with primary material or its derivatives. He represented the first material as an absolutely dense body, each part of which occupies a part of space proportional to its size: it is not capable of stretching or compression and cannot occupy the same place with another part of matter. This matter is capable of dividing into parts of any form under the action of an applied force, and each of its parts can have any permissible movement ^[7] . Particles of matter retain their shape, as long as they have acquired movement. With the loss of motion, particles are capable of combining ^[8] . He assumed that, under the action of the applied force, the particles of the primary matter were grinding their corners in various circular motions. The spheres formed formed vortices, and the fragments filled the gaps between them.

Descartes' invisible ether filled all the space of the Universe free from matter, but did not offer resistance when real bodies moved in it. Descartes divided the "essential matter" by their properties into three categories ^[9] .

1. The element of fire is the thinnest and most penetrating liquid formed in the process of grinding particles of matter. Particles of fire are the smallest and have the highest speed. They are variously divided when confronted with other bodies and fill all the gaps between them. Of them are the stars and the sun.
2. The air element is a sphere that forms the thinnest fluid compared to visible matter, but, unlike the fire element, has a known size and shape due to the presence of axial rotation. This rotation allows the particle to remain in shape even at rest with respect to the surrounding bodies. Of these particles is a cosmos, not occupied by stars or planets, and they form the actual luminiferous ether.
3. The element of the earth is large particles of primary matter, movements in which are very small or completely absent. Planets are made up of these particles.

The mechanical properties of the ether, namely the absolute hardness of the particles of the second element and their tight fit to each other, contribute to the instantaneous propagation of changes in them. When the impulses of change reach the Earth, they are perceived by us as heat and light ^[10] .

Descartes applied the outlined system of the world to explain not only light, but also other phenomena. The cause of gravity (which he considered intrinsic only to earthly objects) was Descartes saw in the pressure of ether particles surrounding the Earth, which move faster than the Earth itself ^[11] . Magnetism is caused by the circulation around the magnet of two opposing streams of the smallest helical particles with opposite threads, so the two magnets can not only attract, but also repel each other. Band-shaped particles are similarly responsible for electrostatic phenomena ^[12] . Descartes also built an original color theory, according to which different colors are obtained due to the different rotational speeds of the particles of the second element ^{[13] [14]} .

Theories of Light after Descartes

Descartes' doctrine of light was substantially developed by Huygens in his Treatise on the Light ( Traité de la lumière , 1690). Huygens viewed light as waves in the ether and developed the mathematical foundations of wave optics.

At the end of the 17th century, several unusual optical phenomena were discovered which should be coordinated with the luminiferous ether model: diffraction (1665, Grimaldi ), interference (1665, Hook ), birefringence (1670, Erasmus Bartolin , studied by Huygens), light velocity estimate ( 1675 , Römer ) ^[15] . There are two variants of the physical model of light:

• Emission (or corpuscular) theory: light is a stream of particles emitted by a source. The straightness of the propagation of light, on which the geometrical optics is based, spoke in favor of this opinion, but diffraction and interference did not fit well into this theory.
• Wave: light is a splash in the air. It is necessary to take into account that the wave then was understood not as an infinite periodic oscillation, as in the modern theory, but as a single impulse ^[16] ; for this reason, the explanations of light phenomena from the wave positions were little plausible.

It is interesting to note that the concept of Descartes – Huygens' luminiferous ether soon became generally accepted in science and did not suffer from the disputes between Cartesians and atomists ^{[17] [18]} , as well as supporters of emission and wave theory, which developed in the 17th — 18th centuries. Even Isaac Newton , who tended rather to the emission theory, admitted that ether also participates in these effects ^[19] . In the writings of Newton, the ether is mentioned very rarely (mainly in his early works), although in personal letters he sometimes allowed himself to “invent hypotheses” about the possible role of the ether in optical, electrical and gravitational phenomena. In the last paragraph of his main work, "The Mathematical Principles of Natural Philosophy, " Newton writes: "Now we should add something about a certain thinnest ether that penetrates all solid bodies and is contained in them." Further, he lists the examples of the physical role of the ether assumed at that time:

Particles of bodies at very small distances mutually attract each other, and upon contact they interlock, electrified bodies act over long distances, both pushing away and attracting close small bodies, light is emitted, reflected, refracted, deflected and heats the body, all feelings are excited, forcing the members of animals to move at will, being transmitted precisely by the vibrations of this ether from the external sense organs to the brain and from the brain to the muscles.

Newton, however, does not comment in any way on all these hypotheses, limiting himself to a remark: “But this cannot be stated briefly, moreover, there is not a sufficient stock of experiments, with which the laws of action of this ether would be precisely defined and shown” ^[20] .

Thanks to the authority of Newton, the emission theory of light in the eighteenth century became generally accepted. Ether was considered not as a carrier, but as a carrier of light particles, and the refraction and diffraction of light were explained by a change in the density of the ether — near bodies (diffraction) or when light passes from one medium to another (refraction) ^[21] . In general, the ether as part of the world system relegated to the background in the 18th century, however, the theory of ether vortices remained, and there were unsuccessful attempts to use it to explain magnetism and gravity ^[22] .

The development of models of the ether in the XIX century

Wave Theory of Light

At the beginning of the 19th century, the wave theory of light, which considered light as waves in the ether, won a decisive victory over emission theory. The first universalist scientist Thomas Jung delivered the first blow to the emission theory. In 1800, he developed the wave theory of interference (and introduced the term itself) on the basis of the principle of wave superposition formulated by him. According to the results of his experiments, he rather accurately estimated the wavelength of light in different color ranges.

At first, Jung's theory was met with hostility. Just at this time, the phenomenon of birefringence and polarization of light was deeply studied, perceived as decisive evidence in favor of emission theory. But here in support of the wave model (knowing nothing about Jung), Augustin Jean Fresnel spoke out. In a series of witty experiments, he demonstrated purely wave effects completely inexplicable from the standpoint of corpuscular theory, and his memoir containing a comprehensive study from wave positions and a mathematical model of all then known properties of light (except polarization) won the Paris Academy of Sciences competition ( 1818 ). A funny incident is described by Arago : at a meeting of the commission of academicians, Poisson spoke out against Fresnel's theory, since it indicated that under certain conditions a brightly lit area could appear in the center of the shadow from an opaque circle. At the next meeting, Fresnel showed members of the commission this effect.

Jung and Fresnel initially considered light as elastic (longitudinal) vibrations of a rarefied, but extremely elastic ether, similar to sound in air. Any light source triggers elastic oscillations of the ether, which occur at a gigantic frequency, nowhere else noted in nature, which results in their spreading at a tremendous speed ^[23] . Any material body attracts ether, which penetrates into the body and condenses there. The refractive index of light depended on the density of ether in a transparent body ^[24] .

It remained to understand the mechanism of polarization. As early as 1816, Fresnel discussed the possibility that the ether light vibrations are not longitudinal, but transverse. This would easily explain the phenomenon of polarization. Jung at this time also came to this idea. However, transverse oscillations were previously encountered only in incompressible solids, while ether was considered close in properties to gas or liquid. In 1822-1826, Fresnel presented memoirs describing new experiments and a complete theory of polarization, which retains its significance even today.

Cauchy-Stokes model

Interest and confidence in the concept of the ether in the XIX century have increased dramatically. The following (after the 1820s) nearly a hundred years are marked by the triumphant success of wave optics in all areas. Classical wave optics was completed, at the same time raising the most difficult question: what is ether?

When it turned out that the light oscillations are strictly transverse, the question arose of what properties the ether must possess in order to allow lateral vibrations and eliminate longitudinal ones. A. Navier in 1821 received the general equations of the propagation of disturbances in an elastic medium. The Navier theory was developed by O. L. Cauchy (1828), who showed that, generally speaking, longitudinal waves should also exist ^[25] .

Fresnel hypothesized that the ether is incompressible, but allows lateral shifts. This assumption is difficult to reconcile with the full permeability of the ether in relation to the substance. DG Stokes explained the difficulty by the fact that the ether is like a resin: with fast deformations (light emission) it behaves like a solid body, and with slow (say, with the movement of the planets) it is plastic. In 1839, Cauchy perfected his model by creating the theory of a contracting (labile) ether, later modified by W. Thomson .

So that all these models were not considered as purely speculative, one should formally deduce from them the main effects of wave optics. However, such attempts had little success. Fresnel suggested that the ether consists of particles whose magnitude is comparable with the length of the light wave. With this additional assumption, Cauchy was able to justify the phenomenon of dispersion of light . However, attempts to link, for example, the Fresnel theory of the refraction of light with any model of the ether were unsuccessful ^[26] .

Ether and Electromagnetism

Faraday was skeptical about the ether and expressed uncertainty about its existence ^[27] . With the discovery by Maxwell of the equations of classical electrodynamics, the theory of ether has received a new content.

In earlier works, Maxwell used the hydrodynamic and mechanical models of the ether, however, he emphasized that they serve only to explain with the help of a visual analogy. It must be borne in mind that vector analysis did not yet exist, and Maxwell needed the hydrodynamic analogy, first of all, to clarify the physical meaning of differential operators ( divergence , rotor , etc.). For example, in the article “On the Faraday Power Lines” (1855), Maxwell explained that the imaginary fluid used in the model “is only a collection of fictitious properties designed to present some theorems of pure mathematics in a form that is more visual and more easily applicable to physical tasks than a form that uses purely algebraic symbols " ^[28] . Later (since 1864), Maxwell excluded from his work the arguments by analogy ^[29] . Maxwell did not develop specific models of the ether and did not rely on any properties of the ether, except for the ability to maintain the bias current , that is, the movement of electromagnetic oscillations in space.

When the experiments of G. Hertz confirmed Maxwell's theory, the ether began to be considered as a common carrier of light, electricity and magnetism. Wave optics has become an organic part of Maxwell's theory, and there was a hope to build a physical model of the ether on this foundation. The largest scientists of the world were engaged in research in this area. Some of them (for example, Maxwell himself, Umov and Helmholtz ), although she wrote about the properties of ether, actually studied the properties of the electromagnetic field . Another part (for example, D. G. Stokes , W. Thomson ) tried to reveal the nature and properties of the ether itself - to estimate the pressure in it, the density of its mass and energy, to associate with atomic theory.

Chemism in an attempt to understand the ether (DI Mendeleev)

In the writings of DI Mendeleev, this question is directly related to his understanding of the physical causes of periodicity . Since the properties of the elements are periodically dependent on atomic weights (mass), the scientist intended to use these patterns to solve this problem, by determining the causes of the forces of the force and by studying the properties of the medium transmitting them. ^[thirty]

As already noted, it was assumed that the "ether" that fills the interplanetary space is the medium transmitting light, heat and gravity. In the context of such representations, the study of highly rarefied gases seemed possible to the determination of the named substance, when the properties of the “ordinary” substance could no longer hide the properties of the “ether” ^[30] .

In one of his hypotheses, DI Mendeleev was guided by the fact that the specific state of highly rarefied air gases could be “ether” or some unknown inert gas with a very low weight, that is, the lightest chemical element. The scientist writes on the imprint of the Basics of Chemistry, on the sketch of the 1871 periodical system : “The lighter is the ether, millions of times”; in the workbook of 1874, he expresses his thoughts more clearly: “With zero pressure, air has some density, this is ether!”. But in his publications of that time these thoughts were not reflected. The discovery of inert gases at the end of the 19th century actualized the question of the chemical nature of the world ether. At the suggestion of William Ramsay, Mendeleev includes a zero group in the periodic table , leaving room for elements that are lighter than hydrogen . According to Mendeleev, the group of inert gases could be supplemented with a coronium and the lightest, as yet unknown element, named by him newtonium , which constitutes the world ether ^[31]

In April 1902, he expounded his views in the essay “An Attempt of Chemical Comprehension of the World Ether” (published in English in 1904, in Russian - in 1905). In the final part of this work, DI Mendeleev writes ^{[30] [32]} :

Representing the ether with a gas possessing the indicated signs and belonging to the zero group, I strive first of all to extract from the periodic law what it can give, to really explain the reality and the general distribution of the essential substance throughout nature and its ability to penetrate all substances not only gas or vaporous, but also solid and liquid, since the atoms of the lightest elements of which our ordinary substances consist are still millions of times heavier than ethereal and, as one should think, they will not change much of their relationship from utstviya light atoms so, what are atoms or ether. It goes without saying that then I have a whole lot of questions myself, that for most of them it seems to me impossible to answer, and that in presenting my attempt I did not think to raise them or try to answer those that seem to me solvable. He did not write his own “attempt” for this, but only to express himself in a question about which many, I know, think, and about which one should start talking.

Even in his early works, DI Mendeleev arrived at methodological principles and principles that were developed in his subsequent studies. He seeks to approach the solution of a particular issue, following these general principles, creating a philosophical concept within which specific data will be analyzed. This is also characteristic of research concerning this topic, which were expressed by results that have no direct relation to it. ^[33] Driven by the idea of ​​detecting ether, DI Mendeleev experimentally began to study rarefied gases, and, addressing this topic, formulated or confirmed the principles of kinetic theory and thermodynamics , theoretically substantiated the conditions for the behavior of compressed gases ^[34] : he obtained the ideal gas equation containing the universal gas constant derived by him, and obtained virial expansions , which are in complete agreement with the first approximations in the now known equations for real gases . Very valuable, but somewhat premature, was the proposal of DI Mendeleev to introduce a thermodynamic temperature scale ^[30] .

Lorentz's ether theory

In the period 1892-1904 Hendrik Lorenz developed the theory of "electron-ether", in which he introduced a strict separation between matter (electrons) and ether. In his model, the ether is completely immobile and is not set in motion by weighty matter. In contrast to earlier electronic models, the electromagnetic field of the ether acts as an intermediary between electrons, and changes in this field cannot propagate faster than the speed of light.

The fundamental concept of the Lorentz theory in 1895 was the “theorem of the corresponding states” for terms of order v / c ^{[A 1]} . This theorem states that an observer moving relative to the ether makes the same observations as the resting observer (after a suitable change of variables). Lorenz noted that it is necessary to change the space-time variables when changing reference systems and introduce two concepts:

• physical Lorentz contraction (1892) ^{[A 2]} to explain the Michelson-Morley experiment;
• the mathematical concept of local time (1895) to explain the aberration of light and the Fizeau experience .

This led to the formulation of the so-called Lorentz transformations by Larmor (1897, 1900) ^{[A 3] [A 4]} and Lorentz (1899, 1904), ^{[A 5] [A 6]} , where (this was noted by Larmor) the complete wording of local time accompanied by a certain slowdown in the time of electrons moving in the ether. As Lorenz (1921, 1928) noted later, he considered the time indicated by the clock, resting on the air as “true” time, while local time was considered by him as a heuristic working hypothesis and a purely mathematical technique ^{[A 7] [A 8]} . Therefore, the Lorentz theorem is considered by modern authors as a mathematical transformation from a “real” system resting on the air into a “dummy” system in motion ^{[B 1] [B 2] [B 3]} .

The work of Lorentz was mathematically substantiated and improved by Henri Poincaré , who formulated the universal Principle of Relativity and tried to reconcile it with electrodynamics. He declared simultaneity to be no more than a convenient agreement, which depends on the speed of light, so that the constancy of the speed of light would be a useful postulate in order to make the laws of nature as simple as possible. In 1900 and 1904 ^{[A 9] [A 10],} he physically interpreted Lorentz's local time as the result of clock synchronization using light signals. In June and July 1905 ^{[A 11] [A 12]} he declared the principle of relativity a general law of nature, including gravity. Poincaré corrected some Lorentz errors and proved the Lorentz invariance of the equations of electrodynamics. Nevertheless, he used the notion of ether as a real, but completely undetectable medium, and distinguished between apparent and real time, so most historians of science believe that Poincaré could not create a special theory of relativity ^{[B 1] [B 4] [B 2]} .

Ether and Gravity

During the seventeenth and nineteenth centuries, numerous attempts were made to link the ether with gravity and to bring the physical foundation under the Newtonian law of world wideness . Historical reviews mention more than 20 such models of varying degrees of development. The following ideas were expressed more often than others ^{[35] [36] [37]} .

• Hydrostatic model: since the ether was thought to accumulate inside the material bodies, its pressure in the space between the bodies is lower than at a distance from these bodies. Excessive pressure on the side "pushes" the body to each other.
• The result is the propagation through the ether of oscillations ("pulsations") of atoms of matter.
• There are “sources” and “drains” on the air, and their mutual influence manifests itself as an agony.
• The ether contains many randomly moving microparticles (corpuscles), and the two bodies are caused by the fact that each body "shields" the other from these particles, thereby creating an imbalance of forces (pushing corpuscles more than pushing).

All these models were subject to well-argued criticism and failed to achieve widespread scientific recognition ^[36] .

Hydrostatic model

For the first time this model was published in the list of problems and questions that Newton placed at the end of his work "Optics" (1704). Newton himself never spoke in support of this approach, limiting himself to the well-known statement: “I still could not deduce the cause of these properties of the force of power from phenomena, but I do not invent hypotheses.” This idea has never received any serious development ^[36] .

Another variant of this model was proposed by Robert Hook : attraction is caused by the oscillations of atoms transmitted from body to body through the ether. This idea was developed in the XIX century in the form of "pulsation" theories ^[36] .

“Pulsation” Theories

Among the "pulsation" theories, the model of the Norwegian physicist Karl Bjerknes , who was one of the first to try to create a unified theory of all fields, occupies the most prominent place. Bjerknes's publications (1870s) developed the following idea: bodies in the air behave like synchronous pulsating bodies in an incompressible fluid, between which, as we know, an attraction occurs that is inversely proportional to the square of the distance. The concept of Bjerknes was supported by English physicists Frederick Guthrie ( Frederick Guthrie ) and William Hicks ( William Mitchinson Hicks ), the latter theoretically described "negative matter", whose atoms oscillate in antiphase, and antigravity. In 1909, the theory of Bjerknes was developed by Charles V. Burton , who attributed pulsations to electrons inside bodies ^[38] .

“Pulsation” models were sharply criticized, the following objections were raised against them ^[38] .

1. The ether theory, which was generally accepted at the end of the 19th century, considered it as an elastic medium; therefore, the incompressibility property should either be somehow substantiated or the existence of two radically different types of ether should exist.
2. The reasons for the synchronization of atomic vibrations are not clear.
3. In order to maintain undamped pulsations, some external forces are needed.

Sources / sinks on air

The main authors of this group of models were British scientists K. Pearson ( K. Pearson ) and George Adolph Schott ( George Adolphus Schott ). Pearson, a specialist in hydrodynamics, first supported pulsation theories, but in 1891 he proposed a model of the atom as a system of ether jets, with the help of which he hoped to explain both electromagnetic and gravitational effects ^[39] :

The primary substance is a liquid non-rotating medium, and the atoms or elements of matter are the jets of this substance. It is impossible to say where these jets come from in three-dimensional space; in the possibility of knowing the physical universe, the theory is limited to their existence. Maybe their occurrence is associated with a space of a higher dimension than our own, but we cannot know anything about it, we are dealing only with streams into our environment, with jets of ether, which we have proposed to call “matter”.

The mass, according to Pearson, is determined by the average speed of the jets of ether. From these general considerations, Pearson managed to deduce the Newtonian law of aggression. Pearson did not explain from where and where the etheric streams flow. This aspect tried to clarify Schott, assuming that the radius of the electron increases with time, and this “inflation” is the source of the movement of the ether. In the variant Schott, the constant of change is changing with time ^[39] .

Lesage Theory

The idea of ​​this ingenious mechanical model appeared in the times of Newton ( Nicola Fatio de Duile , 1690), the author of the developed theory was the Swiss physicist Georges Louis Lesage , whose first publication appeared in 1782 ^[40] . The essence of the idea is shown in the figure: the space is filled with some rapidly and randomly moving etheric corpuscles, their pressure on a single body is balanced, while the pressure on two close bodies is unbalanced (due to partial shielding from the side of the bodies), which creates the effect of mutual attraction. An increase in body weight means an increase in the number of atoms constituting this body, due to which the number of collisions with the corpuscles and the amount of pressure on their part increases proportionally, so the force of attraction is proportional to the body mass. From here Lesage derived the law of Newton ^[41] .

Critics of the theory of Lesage noted many of its weak points, especially from the point of view of thermodynamics . James Maxwell showed that in the model of Lesage, energy will certainly turn into heat and quickly melt any body. As a result, Maxwell concluded ^[42] :

We have devoted more space to this theory than it seems to deserve, because it is ingenious and because it is the only theory about the cause of the cause, which was so extensively developed that it was possible to discuss the arguments for and against it. Apparently, she cannot explain to us why the temperature of bodies remains moderate, while their atoms withstand a similar bombardment.

Henri Poincare calculated (1908) that the speed of the corpuscles must be many orders of magnitude higher than the speed of light, and their energy would incinerate all the planets ^[41] . There were also insurmountable logical difficulties ^[36] :

• If the screening is caused by shielding, then the Moon, when it is between the Earth and the Sun, should significantly influence the force of gravity of these bodies and, accordingly, on the trajectory of the Earth, but nothing like this is observed in reality.
• A fast moving body should experience excessive pressure from the corpuscles in front.

An attempt by George Darwin to replace corpuscles with waves in the air was also unsuccessful ^[43] . In the 1910 survey, the Lesage model is confidently characterized as untenable ^[41] .

Difficulties in the theory of the ether (end of XIX - early XX century)

In 1728, the English astronomer Bradley discovered the aberration of light : all the stars in the sky describe small circles with a period of one year. From the point of view of the aetheric theory of light, this meant that the ether was motionless, and its apparent displacement (when the Earth moves around the Sun) on the principle of superposition rejects the images of stars. Fresnel, however, admitted that the ether inside the moving substance was partially entrained. This view seemed to be confirmed in the experiments of Fizeau .

In 1868, Maxwell proposed a scheme of decisive experience, which, after the invention of the interferometer, was implemented in 1881 by the American physicist Michelson . Later, Michelson and Edward Morley repeated the experiment several times with increasing accuracy, but the result was invariably negative - there was no “ether wind”.

In 1892, G. Lorenz and, independently of him, J. Fitzgerald suggested that the ether is stationary, and the length of any body shortens in the direction of its movement, due to which the “ether wind” becomes more difficult to detect. However, the question remained unclear - why the length is reduced exactly to the extent that the detection of the ether (more precisely, movement relative to the ether) is impossible. At the same time, the Lorentz transformations were discovered, which were initially considered specific to electrodynamics. These transformations explained the Lorentz contraction of length, but were incompatible with classical mechanics based on Galilean transformations . Henri Poincaré showed that the Lorentz transformations are equivalent to the principle of relativity for an electromagnetic field; He believed that the ether exists, but in principle can not be detected.

The physical essence of the Lorentz transformations was revealed after the works of Einstein . In an article in 1905, Einstein considered two postulates: the universal principle of relativity and the constancy of the speed of light. The Lorentz transformations (not only for electrodynamics), the reduction of length and the relativity of simultaneity of events immediately flowed out of these postulates. In the same article, Einstein pointed out the uselessness of the ether, since he failed to attribute any reasonable physical attributes, and everything that was considered the dynamic properties of the ether absorbed the kinematics of the special theory of relativity (STR). From this point on, the electromagnetic field was considered not as an energy process in the ether, but as an independent physical object.

New ideas did not win immediately, a number of physicists for several decades after 1905 made attempts to restore confidence in the ether model. In 1924, Dayton Miller announced that he had discovered the "ethereal wind." Miller’s result was not confirmed, and much more accurate measurements (using various methods) again showed that there is no “ether wind” ^[45] . Other physicists tried to use the Sagnac effect to prove the existence of the ether, but this phenomenon is fully explained in the framework of the theory of relativity ^[46] . The possible limits of applicability of the theory of relativity are also investigated ^[47] .

The main reason why the physical concept of ether was rejected was the fact that this concept, after the development of the SRT, turned out to be superfluous. Among other reasons, contradictory attributes attributed to aether are imperceptibility for a substance, transverse elasticity, inconceivable velocity of oscillations compared to gases or liquids, etc. An additional argument was the proof of the discrete ( quantum ) nature of the electromagnetic field, which is incompatible with the hypothesis of a continuous ether.

In his article “The Principle of Relativity and Its Consequences in Modern Physics” (1910), A. Einstein explained in detail why the concept of the luminiferous ether is incompatible with the principle of relativity . Consider, for example, a magnet moving across a closed conductor. The observed picture depends only on the relative motion of the magnet and the conductor and includes the appearance of electric current in the latter. However, from the point of view of the theory of ether in different reference systems, the picture is significantly different. In the reference system associated with the conductor, as the magnet moves, the magnetic field strength in the ether changes, resulting in an electric field with closed power lines, which in turn creates a current in the conductor. In the reference system associated with the magnet, the electric field does not occur, and the current is created by the direct action of a change in the magnetic field on the electrons of the moving conductor. Thus, the reality of processes in the air depends on the observation point, which is unacceptable in physics ^[48] .

Later, after creating the general theory of relativity (GTR), Einstein proposed to renew the use of the term, changing its meaning, namely, to understand the physical space of GTR ^[ by the ether ^{] [49]} . Unlike the luminiferous ether, physical space is not substantive (for example, one cannot attribute own motion and self-identity to points of space), therefore for space, unlike Lorentz-Poincare ether, there are no difficulties with the principle of relativity ^[50] . However, most physicists chose not to return to the use of the already abolished term.

Part of the scientists and after 1905 continued to support the concept of the luminiferous ether, they put forward various alternative theories and tried to prove them experimentally. However, invariably it turned out that the theory of relativity and the theory based on it are in agreement with the results of all observations and experiments, ^{[51] [52]} while there was no competitive ether theory capable of describing the whole set of experimental facts.

In modern scientific articles, the term "ether" is used almost exclusively in works on the history of science ^[53] . Nevertheless, from time to time there are proposals to revive this concept as useful for physics.

Some of these opinions are more terminological in nature. As mentioned above, Einstein also suggested calling physical space as ether to emphasize that it has not only geometric, but also physical attributes. Whittaker later wrote: “ It seems to me absurd to keep the name“ vacuum ”for a category with so many physical properties, but the historical term“ ether ”is the best suited for this purpose ” ^[54] . Nobel laureate in physics Robert B. Laughlin said so about the role of the ether in modern theoretical physics:

Paradoxically, but in the most creative work of Einstein (the general theory of relativity ) there is a need for space as a medium, whereas in its initial premise ( special theory of relativity ) there is no need for such an environment ... The word "ether" has an extremely negative connotation in the theoretical physics because of his past association with the opposition of the theory of relativity. This is sad because it fairly accurately reflects how most physicists actually think about vacuum ... Relativity actually does not say anything about the existence or non-existence of matter permeating the universe ... But we are not talking about this because it is taboo . ^[55]

These proposals did not receive substantial support ^{[56] [57] [58]} . One of the reasons for this is that ether associates with mechanical models that are characterized by the velocity of the medium at each point (three- or four-dimensional vector), and the known physical fields do not have similar properties, for example, the metric field is a tensor , not a vector field, and Standard model calibration fields have additional indices.

The term aether is rarely used in scientific work in the creation of new terminology. For example, in A. de Gouvêa, Can a CPT violating ether solve all electron (neut) neutrino puzzles? Phys. Rev. D 66, 076005 (2002) ( hep-ph / 0204077 ), “ CPT-violating ether” means only certain types of terms in the potential of the neutrino Lagrangian .

More radical constructions in which ether acts as a substance (medium) come into conflict with the principle of relativity ^[51] . Such an ether due to a very weak interaction with the ordinary world can lead to some phenomena, the main of which is a weak violation of the Lorentz invariance of the theory. Links to some of these models can be found in the SLAC Spiers Database .

However, so far no observable physical phenomena have been found that would justify resuscitating the concept of substantial ether in any form. In the bulletin " In Defense of Science ", published by the Commission to combat pseudoscience and falsification of scientific research under the Presidium of the Russian Academy of Sciences , the theory of ether is characterized as pseudoscience ^[59] .

Radio appeared long before the term aether came out of scientific use, and many phrases related to the aether took root in the professional terminology of the media industry: the program went on the air , live on the air , etc. The term “broadcast” was used in a number of articles Of the Civil Code relating to copyright and related rights. The English version of the term ( Ether ) is present in many electronic terms (for example, “ Ethernet ”), although the word air is used for radio communications and broadcasting.

• History of the theory of relativity
• History of physics
• Newtonium
• Theory of Gravity
• Thermal Gas
• Phlogiston
• Ether (mythology)

Primary sources

1. ↑ Lorentz, Hendrik Antoon (1895), Versuch einer Theorie electrischen und optischen Erscheinungen in bewegten Körpern , Leiden: EJ Brill  
2. ↑ Lorentz, Hendrik Antoon (1892), " De relatieve beweging van de aarde en den aether ", Zittingsverlag Akad. V. Wet. T. 1: 74–79  
3. ↑ Larmor, Joseph (1897), " The Philosophical Transactions of the Royal Society , Vol. 190: 205–300 , DOI. 10.1098 / rsta.1897.0020 On the Dynamic Theory of the Electric and the Luminiferous Medium  
4. ↑ Larmor, Joseph (1900), Aether and Matter , Cambridge University Press  
5. ↑ Lorentz, Hendrik Antoon (1899), " Simplified Theory of Electrical and Optical Phenomena in Moving Systems ", Proceedings of the Royal Netherlands Academy of Arts and Sciences T. 1: 427–442  
6. ↑ Lorentz, Hendrik Antoon (1904), "The Electromagnetic Selection ", Proceedings of the Royal Netherlands Academy of Arts and Sciences T. 6: 809–831  
7. ↑ Lorentz, Hendrik Antoon (1921), " Deux Memoires de Henri Poincaré sur la Physique Mathématique ", Acta Mathematica T. 38 (1): 293–308 , DOI 10.1007 / BF02392073  
8. ↑ Lorentz, HA; Lorentz, HA; Miller, DC & Kennedy, RJ (1928), " Conference on the Michelson-Morley Experiment ", The Astrophysical Journal T. 68: 345–351 , DOI 10.1086 / 143148  
9. ↑ Poincaré, Henri (1900), " La théorie de Lorentz et le principe de réaction ", Archives néerlandaises des sciences exactes et naturelles Vol . 5: 252–278   . See also the English translation Archived June 26, 2008. .
10. ↑ Poincaré, Henri (1904/1906), " The Principles of Mathematical Physics ", in Rogers, Howard J., Congress and arts, universal exposition, St. Petersburg. Louis, 1904 , vol. 1, Boston and New York: Houghton, Mifflin and Company, p. 604–622  
11. ↑ Poincaré, Henri (1905b), " Sur la dynamique de l'électron ", Comptes Rendus T. 140: 1504–1508  
12. ↑ Poincaré, Henri (1906), " Sur la dynamique de l'électron , Rendiconti del Circolo matematico di Palermo T. 21: 129–176 , DOI 10.1007 / BF03013466  

Secondary sources

1. ↑ ^{1 2} Miller, Arthur I. (1981), Albert Einstein's special theory of relativity. Emergence (1905) and early interpretation (1905–1911) , Reading: Addison – Wesley, ISBN 0-201-046767-2  
2. ↑ ^{1 2} Darrigol, Olivier (2000), Electrodynamics from Ampére to Einstein , Oxford: Clarendon Press, ISBN 0-19-850594-9  
3. ↑ Janssen, Michel & Mecklenburg, Matthew (2007), VF Hendricks, ed., " From classical to relativistic mechanics: Electromagnetic models of the electron ", Interactions: Mathematics, Physics and Philosophy (Dordrecht: Springer): 65–134 , < http://www.tc.umn.edu/~janss011/ >  
4. ↑ Pais, Abraham (1982), Albert Einstein , New York: Oxford University Press, ISBN 0-19-520438-7