Luminiferous aether

The aether (Greek αἰθήρ [" Aether " ], the (blue ) sky ') is a hypothetical substance which has been postulated in the late 17th century as a medium for the propagation of light. Later, the concept of the optics was also applied electrodynamics and gravitation, especially around based on action at a distance to avoid assumptions.

There were insurmountable conceptual difficulties and contradictions with experimental results. Thus, Maxwell's equations could never be fully reconciled with the mechanical ether models. Similarly, the ether had one hand are defined as material solid, on the other hand, its resistance to the movement of the heavenly bodies should be imperceptibly small. Both static including entrained ether was disproved by experiments and observations. The Äthermitführung disagreed with the aberration of light. And the resting ether was disproved by the Michelson -Morley experiment. Various auxiliary hypotheses that have been introduced in order to save the concept, contradicting yourself and also appear to be arbitrary.

Since the ether does not play a role in the observable physical phenomena, had an alternative concept to be developed, in which a equipped with a state of motion medium does not exist. This happened with the special theory of relativity. With their help, the propagation of electromagnetic waves can describe for the first time consistent ( for other reasons and motivations, see the main article History of special relativity ). The relativistic electrodynamics has now been merged with quantum mechanics, the resulting relativistic quantum electrodynamics also does not require a carrier medium.

4.1 resistance
4.2 relative movement between ether and matter 4.2.1 Dormant ether
4.2.2 Full Äthermitführung

4.3.1 Experiments first order
4.3.2 Experiments second order
4.3.3 Modification of Stokes ' theory

5.1 Lorentz shear ether
5.2 Special Theory of Relativity

6.1 Pressure theories
6.2 Einstein's new definition of the ether

Early development of the light ether

The modern ether theories go back to the Aristotelian theory of the elements, which introduced the ether as a medium of uniform circular motions of the stars.

Descartes, Hooke, Huygens

In modern times, René Descartes came from the following philosophical considerations: Matter is only characterized by expansion and vice versa, there is also no expansion without matter. It follows that all of the "empty" space must be filled with matter. This he associated with the idea that all processes must be understood by direct contacts of this matter, that is, as near powers in the form of movement and pressure. He used this idea in 1637 in his theory about the nature of light by spherical particles of light postulated, where the pressure exerted by these closely pressed together particles static pressure is to be understood as light. He succeeded in doing (like in front of him Willibrord van Roijen Snell 1621), to discover the laws of refraction.

According to Descartes, there had been considerable debate as to whether an empty space is conceivable. Blaise Pascal commented: "Rather endures the nature take its demise as the smallest empty space. " Pascal thus criticized the postulate of contemporaries, they could produce a total vacuum on reduction of air pressure. He was referring in particular to Evangelista Torricelli's assumption to have created an empty space. Pascal pointed out that the lack of air was not automatically the same as a complete void of space.

In contrast to Descartes ' idea of a static pressure was Robert Hooke in 1665 of a " homogeneous medium " from where light propagates in the form of pulses and vibrations straight and uniform speed in all directions. Each light pulse can be regarded as a growing sphere, analogous to the propagation of the waves on the water surface. This means that there will be no material transport, but only the information on the motion state is transmitted. The different areas of the pulses would in the transition from one medium to another have different speeds, which Hooke Descartes ' explanation of refraction replaced. Although his theory meant in comparison to Descartes a big step forward - because he did not yet have the concepts of wave theory, he could not fully explain all the laws of refraction and reflection. Also, its related theory of colors was soon refuted by Newton.

Christiaan Huygens finally formulated 1678-1690 the first full wave theory of light, its light ether permeated the solid matter as well as the empty space of the universe according to his imagination. By designing a systematic description and explanation of the wave phenomena, he could give an elegant explanation for the reflection and refraction. This was seen as an important argument in favor of the wave theory, and thus for the airwaves.

Newton's criticism

Isaac Newton criticized that the wave theory could explain neither the rectilinear propagation, nor the polarization of light. That's why he assumed that light consists of particles or corpuscles is to interpret the rectilinear propagation and reflection phenomena can mechanically, where he made no specific statements about the nature of these corpuscles. Newton was able to explain the refraction and diffraction phenomena satisfactorily with this model. That's why Newton kept while in his influential book Opticks (1704), the Korpuskularauffassung the light when combined these with an ether, which is to be responsible for the transfer of heat. This medium is to lose in close to the matter somewhat in density, and by interaction of the particle with this medium, either heat is generated and on the other hand achieve effects such as diffraction and refraction. He wrote:

" If not, the heat of a room through the vibrations of a much finer medium transported in the vacuum remaining in the vacuum after evacuation of the air? And this medium is not the same as that is refracted and reflected by the light and by the vibrations of the light transfers heat to form bodies, and is thereby placed in conditions easier reflection and transmission? "

Although Newton in the second book of his main work " Principia Mathematica " all ( always based on an ether hypothesis ) vortex theories to explain the planetary motions had refuted - a then widely accepted hypothesis was published in 1644 by Descartes - he rejected the ether never final, but known - the last time in 1704 - in Opticks only:

" For what is the ether, I do not know. "

Light ether as a solid

With some exceptions, such as Benjamin Franklin and Leonhard Euler, the corpuscular theory was preferred by most physicists at that time due to the large Newton's authority. This was confirmed in particular by James Bradley's discovery (1728) of the aberration of light, which could be very easily associated with the particle nature.

Only from 1800 to 1804 was Thomas Young help the wave theory to break through. Young was able to prove the first that the wave theory of light could explain some phenomena that could not be reconciled with the corpuscular theory of Newton in line. He explained, for example, Newton's rings by the principle of interference and was the first to the double-slit experiment, the result clearly in favor of the wave nature of light, and thus for the existence of the ether. Also, Young was unable to agree on the effect of polarization of the wave model. In 1817 he also solved this problem by assuming that light waves behave like transverse waves - which was unusual, as it had introduced in analogy to the sound, the light waves as longitudinal waves.

Augustin Jean Fresnel, it was finally, gave an elaborate and in many cases up to the present time valid theory of optical phenomena on the basis of the luminiferous ether. He headed it from 1816 to 1819 on the model of mechanics properties of the ether. According to his theory, the aether behaves opposite transverse waves as an elastic solid. This means, in empty space, the ether is at rest and the light propagates at the same speed in all directions.

The theories of the elastic ether was ( in various forms ) and Others by Claude Louis Marie Henri Navier (1827 ), Augustin Louis Cauchy (1828), Siméon Denis Poisson (1828), James MacCullagh (1837 ), Franz Ernst Neumann (1837 ), George Green (1838 ) continued. On the one hand, these models were very helpful and useful in the development of the theory of solids, on the other hand there were also many partial ( from today's perspective ) fantastic hypotheses about the mechanical ether constitution.

For example, based MacCullaghs ether model from 1839 to mechanical distortions with respect to absolute space in an elastic solid, yielding equations of motion that correspond exactly to the then-unknown Maxwell equations in their form. Despite this amazing match, the model had to be discarded because of various contradictions in explaining optical phenomena. Until 40 years later, George Francis FitzGerald had then pointed out that MacCullogh with its 1839 presented equations anticipated the 1864 published Maxwell equations in a sense.

Electromagnetic ether

After several ether pressure models for the explanation of magnetism and electricity were developed in the 16th and 17th century, the triumph of the Newtonian theory of gravitation led to a long-distance effect was assumed without ether for these phenomena. It emerged as the major theories of Charles Augustin de Coulomb and André- Marie Ampère. It already by Wilhelm Eduard Weber ( 1856) and others has been noted that the speed of light plays a significant role within the electromagnetism.

One interpretation of this relationship then first succeeded Michael Faraday. This concluded that there are lines of force in the ether, which transmit the electromagnetic effects with finite velocity. By Maxwell 's equations, the James Clerk Maxwell had developed 1861 to 1864, after the unification of optics and electrodynamics could be achieved. The ether was thus the carrier of all electromagnetic phenomena, including the optics, of its effectiveness Maxwell was convinced. In the written by him entry in the Encyclopædia Britannica, it is at the end to sum up:

" What are the difficulties we have to develop a consistent picture of the nature of the ether: There can be no doubt that the interplanetary and interstellar space is not empty, but that both are filled with a material substance, which certainly the most extensive and probably most consistent matter, of which we know. "

The link between the electrodynamic and optical phenomena was the speed of light, which was considered a limiting velocity relative to the ether. Maxwell himself and others formulated several mechanical ether models such as the widely discussed model of molecular vortices of Maxwell (pictured right). This could, as well as Maxwell himself noted, only some aspects are explained, because these models often contradicted each other - what was certain were the mathematical results which culminated in Maxwell's equations.

In addition to Maxwell also presented other research on various models. Particularly well known were those in which vertebrae were used to represent molecular and electromagnetic effects. Hermann von Helmholtz ( 1858) showed that vortex rings are indestructible in a perfect fluid. Kelvin ( 1867) subsequently established a theory in which the atoms of matter are just such vortices. The interactions of matter are then comparable to the interaction of smoke rings, which always form new compounds. But this theory had to be discarded because the connections could not remain stable. Another variant was Kelvin's Vortex Sponge theory, cooperate in certain sections of the ether in both rotating -rotating parts. It also came here does not go beyond analogies, so that it ultimately failed to create a unified mechanical ether theory, which explains the whole electromagnetic field and matter.

While British researchers relatively quickly the theory of Maxwell took over and further developed ( as Joseph John Thomson, Oliver Heaviside, George Francis FitzGerald, John Henry Poynting, Joseph Larmor ), one remained in the German-speaking area in action at a distance theories in the sense of Weber's and Neumann. That changed in 1888, when Heinrich Hertz proved the predicted by Maxwell finite speed of propagation of electromagnetic forces directly. He brought the contemporary view over the airwaves to the point:

"Take from the world's electricity, and the light disappears; take out of the world the light transmitting ether, and the electrical and magnetic forces can not exceed the space. "

Hertz developed here 1887-1890 's electrodynamics of moving bodies. Prior to or simultaneously with Hertz a similar theory was also developed by Oliver Heaviside. It was important the formulation of Maxwell's equations which Hertz had laid his theory as a postulate based, and later in the form of " Maxwell - Hertzian equations " had great influence - which equations are their modern form were eventually given by Heaviside.

Problems of ether theories

Resistance

A fundamental problem of the ether theory was that a mechanical ether would oppose a moving body in a resistance movement. To solve this problem, suggested George Gabriel Stokes ( 1845) that the ether behave like bad luck: This shatters when hit very quickly it with a hammer. However, a heavy weight will sink like a viscous fluid. This would explain that when vibrations such as those of the light of ether as an elastic solid body behaves, and massive, slow objects such as the planets like a liquid. Meanwhile, investigations had led to the ether theory to believe that the etheric matter about 1.5 · 1011 must be times lighter than atmospheric air.

Other physicists were more radical: They assumed that the ether is the primal matter and visible matter is merely a form of excitation of the ether. In analogy to vibrations which propagate with constant velocity through a medium - the problem of resistance would not be standing here. Some examples: According to Lord Kelvin, the ether is a liquid and matter can be regarded as a vortex, which propagates in the ether. After Lorentz matter is merely a " modification" of the ether, after Joseph Larmor, they must be regarded as torsion of the ether, and Paul Langevin defines it as mere liquefaction of the ether, which continue to move these points of liquefaction and the ether solidifies behind them.

Relative movement between ether and matter

It was now a question of the relative motion between matter and ether. The aberration of light spoke loudly Young and Fresnel for the adoption of a dormant or uninfluenced by matter and ether contradicted the full Äthermitführung through matter.

Resting ether

The above explanation of the aberration by means of stationary ether only works when light behaves like a particle in the ether. Since the light was regarded as a wave, there was the following problem: Due to the earth's motion through the ether at rest no deflection of the wave planes takes place - that is, the position of the wavefront does not change and there is no aberration. The problem can be solved if the following from the electromagnetic theory of light Poynting vector is taken into account, indicating the direction of energy transport and the radiation paths in the waves. This direction is a function of the relative movement of the source and observer, and thus results in the aberration. A simpler explanation ( which goes back to Fresnel ) arises when considering certain wave groups are "cut out" of the wave front that it comes into the lens for interference, and the back. Since wave groups behave analogously to particles also results from the corresponding aberration.

Already in 1810 checked François Arago experimentally the possibility of an influence of the motion of a prism on the refraction of light, which should lead to a change in angle of aberration, but the result was negative. [E 1] Fresnel (1818 ) explained the result now with the assumption that the speed of light will be modified in the bodies by partial entrainment of the ether. This entrainment arises in that compressed in the bodies of ether and was therefore slightly denser, with exactly this excess of ether density - with the exception of the range of normal density - will be carried by the bodies. The entrainment coefficient (where the velocity of the medium and n is the refractive index ) is obtained with.

A detailed confirmation of the osmotic drag coefficient was made possible by the Fizeau experiment by Hippolyte Fizeau ( 1851). He used an interferometer arrangement in which the speed of light was measured in the water. Fizeau's result in even more accurate form of Michelson and Morley (1886 ) was confirmed. [ E2 ] [ E3 ] The weakness of the Declaration Fresnel was that due to the dependence of the ether density is also a function of the coefficient of the color or frequency should be - what could not vote. Thus, although Fresnel's formula and the basic idea of a stationary ether of many were accepted, but the exact processes in the ether, which resulted in the partial entrainment remained unclear and could only be treated very speculative. Fresnel's theory was later due to various experiments, the second order for v / c contained are not maintained, however, it formed the basis of the theory of a stationary ether, which Lorentz 1892-1895 aufstellte (see section " Lorentz ether theory ").

Full Äthermitführung

For George Gabriel Stokes ( 1845) and later Hertz ( 1890) was the idea of an ether, which was hardly or not at all influenced by the movement of matter, very unnatural. Also, starting from an elastic ether represented Stokes hence the idea of a complete entrainment of the ether within and - with the removal decreasingly - also outside the body. In order to obtain the same effects as Fresnel for the explanation of the aberration of light and Fresnelschens osmotic drag coefficient, Stokes had to introduce additional hypotheses complicated.

The main problem was the aberration of light: While Young and Fresnel were able to derive the effect of the fundamental assumptions of almost stationary ether with a low osmotic drag coefficient (pictured above, left) seemed so specified in a completely entrained ether. Because here occurs at the surface of the earth or within a telescope, no relative motion between the Earth and aether, and hence there would be no reason for an aberration of light (pictured above, right). Stokes therefore had to assume that the ether is incompressible and with complete retention on the surface of the earth is still irrotational. These circumstances would now lead to a refraction of light in the entrained ether, which could reproduce the effect of the aberration. For the Fresnel osmotic drag coefficient and thus the explanation of Arago experiment (and later of the Fizeau experiment ) he assumed that, although the entire ether is carried along, but the speed of the ether is slightly modified in the body.

But Lorentz (1886 ) showed that Stokes ' assumptions about the aberration itself and contradict the mechanical laws: all conditions can not be fulfilled simultaneously. Due to the inconsistency and artificiality of these hypotheses to Stokes ' theory could not prevail against Fresnel successful theory.

Null results of the ether wind experiments

Experiments first order

Fresnel Mitführungkoeffizient meant in ether drift experiments, ie in experiments to determine the relative velocity of the earth and the ether were to expect any positive results in the order of, where v is the relative velocity of earth - ether and c is the speed of light is. This was confirmed by the following experiments, the following list on the description of Wilhelm Vienna (1898 ) is based, with changes and further experiments according to the descriptions of Edmund Taylor Whittaker (1910) and Jakob Laub ( 1910):

The experiment Arago (1810 ), which should prove whether the refraction, and thus the aberration of the light of the fixed stars, is influenced by the earth moving. Similar experiments were, inter alia, by George Biddell Airy (1871 ) using a water-filled telescope, and Eleuthère Mascart (1872 ) adjusted, which could also find no effect. [E 1] [ E4 ] [ E5 ]

The experiment of Fizeau (1860 ) to examine whether the rotation of the plane of polarization is changed by glass pillars of the earth's motion. He received a positive result, but could Lorentz show that the results were contradictory. DeWitt Bristol Brace (1904) and Strasser (1907 ) repeated the experiment with greater accuracy, and actually found a negative result. [ E6 ] [ E7 ] [E 8]

The experiment of Martin Hoek (1868 ): This is a more accurate version of the Fizeau experiment, where two light beams are transmitted on opposite rectangular paths, being located in one arm of the experimental arrangement still water. Again, results from the Fresnel's entrainment coefficient a negative result. [E 9]

The experiment of Wilhelm Klinkerfues (1870 ) to examine whether an influence of the earth's motion is to the absorption line of sodium vapor. In fact, he was able to achieve a positive result. But it was obviously observation error, because a repetition of the experiment by Haga (1901 ) gave a negative result. [ E10 ] [ E11 ]

In the experiment, von Ketteler (1872 ), the two beams of the interferometer were sent in opposite directions by two filled with water, oppositely inclined tubes. There was no change in the interference fringes. And Mascart (1874 ) showed that the interference fringes of polarized light in Kalkspanplatten also remained unaffected. [ 12 E ] [E 13]

The experiment of Eleuthère Mascart (1872) for detecting the rotation of the polarization plane in the crystal, showed no change in rotation, when the light beams, then once had the direction of the earth moving the opposite direction. Lord Rayleigh performed similar experiments in 1902 with significantly higher precision, and also received a negative result. [ 5 E ] [ E 13 ] [ E 14 ]

In addition, electro-dynamic experiments were conducted first order. The negative results of the following tests can be explained by Lorentz 's theory of a stationary ether:

The experiment of Wilhelm Conrad Roentgen (1888 ) should prove whether a charged capacitor due to the earth's motion generates magnetic forces. [ E 15 ]

The experiment of Theodor des Coudres (1889 ) should determine whether the induction effect of two coils of wire is influenced to a third by the direction of Earth's motion. Lorentz showed that this effect is at most second order, as that developed due to the earth moving electrostatic charge on the conductors cancels the effect of the first order. [ E 16 ]

The experiment of Frederick Thomas Trouton (1902 ). Here, a capacitor is positioned so that its plates are parallel to the ground motion. The negative result can be explained because of the following from Lorentz's theory of the electromagnetic pulse. [ E 17 ]

The experiment of Konigsberg (1905 ). The plates of a capacitor are in a strong electromagnet field. Due to the earth's motion in the ether, the boards should receive loads, which was not observed. [ E 18 ]

Experiments second order

→ Main article: Michelson - Morley experiment

In the experiments which were able to show effects in the order of, there should necessarily be positive results according to the theory of Fresnel and Lorentzian. The Michelson - Morley experiment (1887 ) was the first experiment of its kind, it was found that the velocity of the earth ( at the surface ) is relative to the presumed aether either approximately equal to zero and the ether is completely carried. That is, the temperature measured by the Michelson result corresponded to about 5-8 km / s, which given the expected speed of 30 km / s could not be interpreted as ether wind. In addition, put various cosmic velocities ( rotation of the Milky Way, movement relative to the rest frame of the cosmic microwave radiation) a speed of about 368 km / s close to what the insignificance of the result demonstrates even more clearly. Further, to date carried out reps with lasers and masers have actually brought complete zero results. Exceptions such as the experiments of Dayton Miller ( 8-10 km / s) could not be confirmed, whereby various sources of error in Miller's experiment could be demonstrated (see Michelson -Morley Experiment # Further experiments ). Further experiments that could determine the second order, were the Trouton -Noble experiment ( 1902), the experiments of Rayleigh and Brace (1904 ), the Trouton - Rankine experiment (1908), and the Kennedy - Thorndike experiment (1932 ). These are all delivered zero results. [ E 19 ] [ 20 E ] [ E 21 ] [ 22 E ] [ E 23 ]

The results of the second-order experiments were very strange, for those days, because they were ' tolerated theory - but Lorentz had 1886, the inadmissibility of Stokes ' only with Stokes pointed theory. On the other hand, Fresnel's entrainment coefficient and thus the theory of a stationary ether by the experiments of the first order had been very accurately confirmed what was in direct contradiction to the result of the MM experiment. [ E 24 ]

Modification of Stokes ' theory

The interference experiments by Oliver Lodge (1893, 1897) and Ludwig Zehnder (1895 ) had shown that the ether is not carried by the movement of different masses. Lodge used while rotating disks, and observed that between the discs occurred no influence of the interference pattern. [ E25 ] [ E26 ] [ E27 ] ( Later it was through the Hammar experiment ( 1935), an even greater accuracy can be achieved. here is an arm was surrounded in a lead sheath, while the other was free. the result was also negative. ) [ e 28 ]

To circumvent these problems, should according to Theodor des Coudres and Wilhelm Wien (1898 ), the Äthermitführung done proportional to the mass or gravity of the body. For large masses like the Earth entrainment would therefore be complete, which explains the negative results of resting on the ground experimental setups such as the Michelson - Morley experiment (1887 ). On the other hand, the positive results of moving on the ground arrays are declared as in the Fizeau experiment (1851 ), or the Sagnac effect (1913), and the negative results of Lodge, etc., as in both cases the effect of gravity of the case instruments used is not sufficient to carry the ether sufficient. But here, too, gave the same Aberrationsprobleme as Stokes. Still trying Max Planck ( 1899) to save this idea with the assumption that could take place, a condensation of the ether near the earth by gravity, so that the ether is replaced by similar properties as needed Stokes for his theory ( " Stokes - Planck theory " ). Lorentz (1899 ) pointed out that, under this assumption, even a 50000- compression of the ether no appreciable influence on the electromagnetic phenomena have - which is extremely unlikely.

As later Georg Joos (1934 ) pointed out, contradicts a complete entrainment through the earth to the positive result of the Michelson - Gale -Pearson experiment ( 1925), which is a variation of the Sagnac experiments. [ E 29 ] Here an attempt was made the rotation to measure the earth itself, that is, in contrast to the usual Sagnac experiments rests on the arrangement of the earth; therefore in a complete entrainment a positive result would not be expected, for it is hardly conceivable that the ether should be influenced by the translation, but not by the rotation of the earth though.

The same problems also had Hertz ' " Electrodynamics of moving bodies " (1889 ), which also included a full Äthermitführung. Meanwhile theory was also rejected because it provided only when moving in the electromagnetic field conductors correct results, but not with moving insulators. Because as from oak Forest (1903) and Wilson (1905 ) found that correspond to effects of moving insulators only a partial dielectric displacement, not a complete shift in accordance with Stokes and Hertz. [ 30 e ] [ e 31 ]

From ether theory of relativity

Due to the negative results of the second-order experiments, and since the idea of the fully entrained ether was exposed to many difficulties had to Fresnel's theory of ( approximately ) stationary aether be modified or the ether idea ever be discarded either. The latter was with exceptions such as Emil Cohn (1901 ) and Alfred Bucherer (1903 ) hardly considered as a classical electrodynamics without ether for most seemed unthinkable. Therefore, retained the vast majority of physicists at the airwaves thoughts. Albert Einstein also tried at a young age (1894/1895) the airwaves in his considerations into account. These efforts culminated in 1905 that he rejected the ether.

Lorentz shear ether

Between 1892 and 1906 developed Hendrik Lorentz and Henri Poincaré theory, the combined Fresnel's ether theory with the Maxwell equations and the electron theory of Rudolf Clausius. Lorentz led for a strict separation between matter (electrons) and ether. In his model, the ether is assumed to be completely unmoved. In this variant of an abstract electromagnetic aether is thus dispensed with a mechanical explanation in terms of the older models ether. Max Born then identified the Lorentz ether with the absolute space of Isaac Newton. The condition of this ether can by the electric field E and the magnetic field H can be described in terms of the Maxwell -Lorentz electrodynamics, these fields have been interpreted as caused by the charges of the electron excitation states or vibrations in the ether. Unlike Clausius, who assumed that the electrons interact through long-range effect, acts as intermediary between the electrons on this same electromagnetic field of the ether in which effects can propagate at a maximum speed of light. Lorentz could explain, for example, with his theory of the Zeeman effect in theory, for which he received the Nobel Prize in 1902. It should be mentioned that Joseph Larmor simultaneously with Lorentz designed a similar electron or ether theory, which was based on a mechanical ether.

In the Lorentz ether theory (as well as in the theory of Larmor ) where the opposition to the Michelson - Morley experiment on the introduction of Lorentz transformations is dissolved. The length contraction and time dilation are seen as processes that relative to an ether moving rods and clocks are subjected, while space and time remain unchanged. Thus, these effects are considered to be asymmetric, that is, moving standards are actually shorter and actually clocks go slower. A moving observer estimates dormant standards, although in an identical manner as the shorter and slower than a stationary clock. This assessment is interpreted as deception, because she wins the moving observer using falsified rods and clocks. The symmetry of the observations and thus the apparent validity of the Poincaré particularly highlighted, phenomenological relativity principle is interpreted as a consequence of a rather random symmetry of the underlying dynamic processes. It prevents the ability to determine your speed relative to the ether, and thus makes it a principle inaccessible size in theory.

Special Theory of Relativity

In the special relativity theory (SRT ) succeeded Einstein, the Lorentz transformation and the other parts of the theory solely from the adoption of two principles - the principle of relativity and the constancy of the speed of light - derived. These principles have been used in part of Poincaré and Lorentzian. Unfortunately, they did not recognize that the theories are sufficient to justify a closed theory without the use of ether or any assumed characteristics of matter. This is precisely one of the main conclusions of Einstein:

"The introduction of a" luminiferous ether " will be so far prove to be superfluous, introduced as after to be developed opinion, neither one with special properties equipped " absolute space ", yet, in which electromagnetic processes take place a point of the empty space, a velocity vector is assigned. "

In SRT length contraction and time dilation are now a consequence of the properties of space and time and not by material rods and clocks. The symmetry of these effects is therefore no coincidence, but a consequence of the equivalence of the observers as the underlying principle of relativity theory. All sizes of the theory are experimentally accessible. Starting from these principles could then Einstein also derived the equivalence of mass and energy. A considerable extension of the theory formed Hermann Minkowski (1907 ) elaboration of the Poincaré (1906 ) suggested idea of a four-dimensional space-time continuum. This all culminated later with respect to further principles in the general theory of relativity.

Science historians like Robert Rynasiewicz or Jürgen Renn are additionally believe that considerations of quantum theory ( as described by Planck ( 1900) and Einstein ( 1905) was introduced ), also played a role in the rejection of the ether. These possible contexts of the 1905 work of Einstein ( Annus mirabilis ) with respect to electrodynamics of moving bodies and the hypothesis of light quanta described by race as follows:

" S. 179: Einstein's reflections on the light quantum hypothesis had also reversed far-reaching consequences for his work on electrodynamics of moving bodies, because they transformed his original tentative reflections on abolition of the ether in an indispensable prerequisite for its further research. "

This interpretation was based on analyzes of the 1905 work, from letters of Einstein, as well as a work from 1909. Several of Einstein in 1905 decisively influenced hypotheses ( light quanta, equivalence of mass - energy, relativity principle, constant light, etc.) have, according to this assumption it influenced each other and had the following consequences: that radiation and fields can exist as independent objects that no static aether exists and that certain radiation phenomena for an ether- free corpuscular theory (which, taken alone, also is false ), while others spoke in favor of the wave theory - which the SRT is compatible with both the wave and the particle concept.

Gravitational ether

Pressure theories

The ether was also used in an attempt to explain the law of gravitation by the aid of basic mechanical processes, such as shocks, without having to resort to the concept of action at a distance.

Nicolas Fatio de Duillier ( 1690) and Georges -Louis Le Sage (1748 ) proposed the Le Sage gravitation before a Korpuskelmodell and used it a shield or Abschattungsmechanismus. A similar model was developed by Hendrik Antoon Lorentz, who used electromagnetic rays instead corpuscles. René Descartes ( 1644) and Christiaan Huygens ( 1690) used to explain the gravity aether vortex. Robert Hooke ( 1671) and James Challis (1869 ) hypothesized that every body emits waves in all directions and tighten these waves the other body. Isaac Newton (1675 ) and Bernhard Riemann ( 1853) suggested ether streams, which flow towards the body and infecting the other body. Again, Newton ( 1717) and Leonhard Euler ( 1760) proposed a model in which the ether near bodies loses density, which should lead to an attractive force between them. Lord Kelvin (1871 ) and Carl Anton Bjerknes (1871 ) designed a model in which each body the surrounding ether placed in pulsation, and thus attempted to explain the electrical charges. These models could not prevail and will no longer viewed as a viable explanation of gravitation.

Einstein's new definition of the ether

The current standard model for describing the gravitational without action at a distance is 1915 accomplished by Einstein General Relativity (GR ). In a letter to Einstein ( 1916) now suspected Lorentz, that in this theory basically the ether had been reintroduced. In his reply, Einstein wrote that one can certainly speak of a "new ether", but should not be applied to him the concept of motion. This train of thought, he led in several semi -popular work (1918, 1920, 1924, 1930) on.

As he wrote in 1920 in the work " Ether and Relativity ", that the special theory of relativity the aether does not necessarily exclusive, since one must ascribe physical qualities of the space to explain effects such as rotation and acceleration. And in general relativity theory, space can not be conceived without gravitational potential, so one could speak of a " gravitational ether" in the sense of " ether of the general theory of relativity ". This is fundamentally different from all the mechanical ether models or the Lorentzian ether, since (as mentioned in the letter to Lorentz ) to him the concept of motion could not be applied:

" Meanwhile, teaches a more accurate reflection that this denial of the ether is not necessary required by the special principle of relativity. [ ... ] According to the general theory of relativity space is equipped with physical qualities; So there exists an ether in this sense. According to the general theory of relativity space without ether is unthinkable; for in such it would not only be no propagation of light, but also no possibility of existence of rods and clocks, so no spatio-temporal distance in the sense of physics. This ether may not be thought with the characteristic of ponderable media property but to consist of trackable by the time parts; the concept of motion may not be applied to him. "

And in 1924 in the paper "On the Ether " Einstein used for any matter outside the existing object with physical properties of the concept of ether. So Newton's absolute space is the "ether of mechanics ", which later became the "ether of Electrodynamics " by Maxwell and Lorentz followed with his absolute state of motion. The special theory of relativity using a " Aether of Electrodynamics ", but in contrast to Newton's absolute space and the classical light ether not a preferred state of motion exists in this ether more - but it also has to be said to a preferred state of acceleration. Here is the ether of the SRT as the ether of electrodynamics to describe as absolutely as occurring in him spatio-temporal or relativistic effects are not influenced by the matter. This "absolute ether" was abolished only by the "ether of the general theory of relativity ", where its properties are influenced by the matter:

"Even after the special theory of relativity, the ether was absolute, since its influence on inertia and light propagation was thought to be independent of physical influences of every kind [ ..] The ether of general relativity therefore differs from that of classical mechanics bezw. the special theory of relativity in that it is not " absolutely ", but is determined in its locally variable properties by ponderable matter. "

He finally made up again his new definition of " ether " together:

" But even if these opportunities to mature into real theories, we are of the ether, that is equipped with physical properties of the continuum, can not do without in theoretical physics; because the general theory of relativity, at the fundamental standpoint, the physicists will probably always hold, excludes an unmediated action at a distance; Near each response theory but does require continuous fields, ie, the existence of an " aether ". "

The conformity of the relativistic ether concept with the classical aether models thus consisted only in Vorhandsein physical properties in space. Therefore also (eg according to John Stachel ) is to deny the assumption that Einstein's new ether concept was contrary to his previous rejection of the ether. Because, as Einstein himself executed, can be as required by the SRT not continue to speak of a material ether in the sense of Newtonian physics, and also the concept of motion can not be applied to him. Now this match is too low with the classic ether, as that this new ether concept in the art would be able to enforce. Also in the context of ART, he is not used to this day.

German physics

The ether concept was later used in the context of the German physics or misused for ideological reasons. There a mechanical and especially vivid justification of physics called for here. Thus spoke Philipp Lenard (1923 ) from the ether, which will be carried by the earth, and from the " Uräther ", which was unaffected by the earth's movement. This thought Lenard, both the (apparent) principle of relativity as well as being able to explain gravitation. This theory could not even prevail in circles of German physics, which, particularly as expressed in the Munich colloquy, in which a certain approach to relativity and quantum theory has been reached.

Ether and modern physics

In addition to the mentioned approaches Einstein's relation to the ART and other physicists tried the ether concept in modern physics to be transferred, for example, formulated Herbert E. Ives a Lorentz's interpretation of SRT. Paul Dirac interpreted for some time he had postulated the Dirac sea as quantum mechanical ether. These formulations could not prevail all.

There are phenomena which are still seen by some physicists as analogies to the ether concept. In his Nobel Prize speech (2006) mentioned George F. Smoot that the reference frame in which the cosmic microwave radiation is isotropic, could be called the ether ( "new aether drift experiments "). Smoot made it clear that there is no contradiction with the SRT and the Michelson - Morley experiment is present since the preference of this reference system is only to simplify the description of the expansion of the universe. Opinions outside the scientific mainstream will continue to be represented by the Nobel Laureates Robert B. Laughlin and Frank Wilczek, which in modern physics - we can speak of an ether - especially with regard to the quantum vacuum.

Because the ether is considered to be a scientific mistake for decades, he is not mentioned in most modern textbooks hardly or at all. In exceptional cases, the currently most represented at universities doctrine is quite clearly expressed. An example of this the many statements and notes are included in the " Gerthsen ", a popular German compendium of physics, even in the latest edition from the year 2006. Moreover, there are still voices that the theory of relativity or the rejection of a motion state reject equipped ether, but these opinions play in the professional world is no longer relevant, see criticism of the theory of relativity.

More ether terms

Ether, and ether, is the English word for ether in the scientific sense. It is used similar to the German word as a metaphor for the medium " radio ".
Ether is also a general historical synonym for the medium radio.
Ethernet as a medium of a given independent software and hardware protocol, which among other things by Robert Metcalfe at Xerox Palo Alto Research Center ( PARC ) was first described and built up on the radio-based ALOHANET at the University of Hawaii.
Ether as the name of the coaxial cable, which was first used for the technical realization of the Ethernet protocol. We Also welcomed the first computers were built for the Ethernet controller, " Michelson " and " Morley ".

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