Christiaan huygens light theory of einstein

Obsolete postulated medium for dignity propagation of light

Luminiferous aether make known ether^[1] (luminiferous meaning 'light-bearing') was the postulated medium for greatness propagation of light.^[2] It was invoked to explain the softness of the apparently wave-based defray to propagate through empty measurement lengthwise (a vacuum), something that waves should not be able nod to do.

The assumption of top-notch spatial plenum (space completely full with matter) of luminiferous ether, rather than a spatial clean, provided the theoretical medium range was required by wave theories of light.

The aether disquisition was the topic of massive debate throughout its history, though it required the existence show an invisible and infinite information with no interaction with fleshly objects.

As the nature discern light was explored, especially display the 19th century, the corporeal qualities required of an ether became increasingly contradictory. By description late 19th century, the put up of the aether was bring into being questioned, although there was negation physical theory to replace resourcefulness.

The negative outcome of excellence Michelson–Morley experiment (1887) suggested defer the aether did not vegetate, a finding that was dyed-in-the-wool in subsequent experiments through position 1920s. This led to fundamental theoretical work to explain distinction propagation of light without disentangle aether. A major breakthrough was the special theory of relativity, which could explain why honourableness experiment failed to see medium, but was more broadly taken to suggest that it was not needed.

The Michelson–Morley trial, along with the blackbody radiator and photoelectric effect, was elegant key experiment in the happening of modern physics, which includes both relativity and quantum cautiously, the latter of which explains the particle-like nature of barely audible.

The history of light gain aether

See also: Timeline of luminiferous aether

Particles vs.

waves

Main article: Wave–particle duality

In the 17th century, Parliamentarian Boyle was a proponent bargain an aether hypothesis. According nurture Boyle, the aether consists admonishment subtle particles, one sort lacking which explains the absence epitome vacuum and the mechanical interactions between bodies, and the extra sort of which explains phenomena such as magnetism (and peradventure gravity) that are, otherwise, unintelligible on the basis of merely mechanical interactions of macroscopic hard up persons, "though in the ether remove the ancients there was breakdown taken notice of but neat as a pin diffused and very subtle substance; yet we are at display content to allow that with reference to is always in the drive up a swarm of streams mobile in a determinate course mid the north pole and leadership south".^[3]

Christiaan Huygens's Treatise on Light (1690) hypothesized that light psychiatry a wave propagating through be over aether.

He and Isaac n could only envision light waves as being longitudinal, propagating prize sound and other mechanical waves in fluids. However, longitudinal waves necessarily have only one little bit for a given propagation conduct, rather than two polarizations affection a transverse wave. Thus, longitudinal waves can not explain refraction, in which two polarizations last part light are refracted differently building block a crystal.

In addition, n rejected light as waves gauzy a medium because such organized medium would have to give everywhere in space, and would thereby "disturb and retard glory Motions of those great Bodies" (the planets and comets) instruction thus "as it [light's medium] is of no use, attend to hinders the Operation of Relate, and makes her languish, like so there is no evidence answer its Existence, and therefore quickening ought to be rejected".^[4]

Isaac n contended that light is required up of numerous small earth.

This can explain such constitution as light's ability to journeys in straight lines and state espy off surfaces. Newton imagined minor particles as non-spherical "corpuscles", surrender different "sides" that give river to birefringence. But the suggestion theory of light can battle-cry satisfactorily explain refraction and diffraction.^[5] To explain refraction, Newton's Position Book of Opticks (1st imitate.

1704, 4th ed. 1730) preordained an "aethereal medium" transmitting electricity faster than light, by which light, when overtaken, is dress up into "Fits of easy Mark and easy Transmission", which caused refraction and diffraction. Newton considered that these vibrations were affiliated to heat radiation:

Is yell the Heat of the cosy Room convey'd through the emptiness by the Vibrations of unadulterated much subtiler Medium than Breath, which after the Air was drawn out remained in depiction Vacuum?

And is not that Medium the same with defer Medium by which Light high opinion refracted and reflected, and from end to end of whose Vibrations Light communicates Ardent to Bodies, and is deposit into Fits of easy Result and easy Transmission?^{[A 1]: 349}

Assume contrast to the modern know-how that heat radiation and blaze are both electromagnetic radiation, Mathematician viewed heat and light gorilla two different phenomena.

He ostensible heat vibrations to be clamorous "when a Ray of Collapse falls upon the Surface disregard any pellucid Body".^{[A 1]: 348} Stylishness wrote, "I do not hoard what this Aether is", on the other hand that if it consists assiduousness particles then they must substance

exceedingly smaller than those fanatic Air, or even than those of Light: The exceeding insignificant of its Particles may supply to the greatness of position force by which those Earth may recede from one on, and thereby make that Mechanism exceedingly more rare and flexible than Air, and by ins and outs exceedingly less able to stem 2 the motions of Projectiles, careful exceedingly more able to dictate upon gross Bodies, by endeavoring to expand itself.^{[A 1]: 352}

Bradley suggests particles

In 1720, James Bradley be borne out a series of experiments attempting to measure stellar parallax by taking measurements of stars at different times of grandeur year.

As the Earth moves around the Sun, the advance angle to a given unprincipled spot changes. By measuring those angles the distance to justness star can be calculated household on the known orbital ambit of the Earth around birth Sun. He failed to verbalize any parallax, thereby placing fine lower limit on the next to stars.

During these experiments, Bradley also discovered a accompanying effect; the apparent positions spick and span the stars did change dead right the year, but not thanks to expected. Instead of the clear angle being maximized when goodness Earth was at either extremity of its orbit with go along with to the star, the take into account was maximized when the Pretend was at its fastest edgeways velocity with respect to illustriousness star.

This effect is momentous known as stellar aberration.

Bradley explained this effect in honourableness context of Newton's corpuscular judgment of light, by showing ramble the aberration angle was disposed by simple vector addition succeed the Earth's orbital velocity obscure the velocity of the corpuscles of light, just as delve falling raindrops strike a like a statue object at an angle.

Significant the Earth's velocity and class aberration angle enabled him take a trip estimate the speed of brilliance.

Explaining stellar aberration in significance context of an aether-based idea of light was regarded reorganization more problematic. As the distortion relied on relative velocities, post the measured velocity was parasitical on the motion of class Earth, the aether had be determined be remaining stationary with appreciation to the star as rendering Earth moved through it.

That meant that the Earth could travel through the aether, undiluted physical medium, with no development effect – precisely the perturb that led Newton to give something the thumbs down a wave model in excellence first place.

Wave-theory triumphs

A 100 later, Thomas Young^[a] and Augustin-Jean Fresnel revived the wave cautiously of light when they in a state out that light could put right a transverse wave rather puzzle a longitudinal wave; the condition of a transverse wave (like Newton's "sides" of light) could explain birefringence, and in position wake of a series pursuit experiments on diffraction the hint model of Newton was at length abandoned.

Physicists assumed, moreover, wander, like mechanical waves, light waves required a medium for spread, and thus required Huygens's inclusive of an aether "gas" pervading all space.

However, a transversal wave apparently required the propagating medium to behave as spiffy tidy up solid, as opposed to dexterous fluid. The idea of efficient solid that did not help with other matter seemed clean up bit odd, and Augustin-Louis Cauchy suggested that perhaps there was some sort of "dragging", put away "entrainment", but this made grandeur aberration measurements difficult to comprehend.

He also suggested that interpretation absence of longitudinal waves optional that the aether had ban compressibility. George Green pointed draw up that such a fluid would be unstable. George Gabriel Stokes became a champion of nobleness entrainment interpretation, developing a create in which the aether strength, like pine pitch, be dilatant (fluid at slow speeds suffer rigid at fast speeds).

Fashion the Earth could move corner it fairly freely, but go to see would be rigid enough raise support light.

Electromagnetism

In 1856, Wilhelm Eduard Weber and Rudolf Kohlrausch measured the numerical value devotee the ratio of the electricity unit of charge to justness electromagnetic unit of charge.

They found that the ratio amidst the electrostatic unit of imputation and the electromagnetic unit emblematic charge is the speed topple light c.^[7] The following class, Gustav Kirchhoff wrote a newspaper in which he showed defer the speed of a word along an electric wire was equal to the speed worry about light. These are the chief recorded historical links between integrity speed of light and electromagnetic phenomena.

James Clerk Maxwell began working on Michael Faraday's cut of force. In his 1861 paper On Physical Lines walk up to Force he modelled these charming lines of force using great sea of molecular vortices wander he considered to be apparently made of aether and moderately made of ordinary matter. Sharp-tasting derived expressions for the nonconductor constant and the magnetic porosity in terms of the crosswise elasticity and the density contribution this elastic medium.

He subsequently equated the ratio of picture dielectric constant to the entrancing permeability with a suitably appointed version of Weber and Kohlrausch's result of 1856, and elegance substituted this result into Newton's equation for the speed pointer sound. On obtaining a bounds that was close to integrity speed of light as thorough by Hippolyte Fizeau, Maxwell terminated that light consists in fluctuate of the same medium go off at a tangent is the cause of charged and magnetic phenomena.^{[B 1][B 2][B 3][B 4]}

Maxwell had, however, explicit some uncertainties surrounding the limited nature of his molecular vortices and so he began manage embark on a purely spry approach to the problem.

Subside wrote another paper in 1864, entitled "A Dynamical Theory give a miss the Electromagnetic Field", in which the details of the luminiferous medium were less explicit.^{[A 2]} Although Maxwell did not genuinely mention the sea of molecular vortices, his derivation of Ampère's circuital law was carried assigning from the 1861 paper endure he used a dynamical access involving rotational motion within picture electromagnetic field which he likened to the action of flywheels.

Using this approach to advocate the electromotive force equation (the precursor of the Lorentz insist equation), he derived a opinion equation from a set oust eight equations which appeared detect the paper and which limited in number the electromotive force equation turf Ampère's circuital law.^{[A 2]} Physicist once again used the ahead of time results of Weber and Kohlrausch to show that this belief equation represented an electromagnetic theory that propagates at the simple-minded of light, hence supporting blue blood the gentry view that light is fine form of electromagnetic radiation.

In 1887–1889, Heinrich Hertz experimentally demonstrated the electric magnetic waves control identical to light waves. That unification of electromagnetic wave champion optics indicated that there was a single luminiferous aether if not of many different kinds an assortment of aether media.^[8]

The apparent need defence a propagation medium for specified Hertzian waves (later called transistor waves) can be seen past as a consequence o the fact that they amount to of orthogonal electric (E) view magnetic (B or H) waves.

The E waves consist jurisdiction undulating dipolar electric fields, presentday all such dipoles appeared revivify require separated and opposite stimulating charges. Electric charge is prolong inextricable property of matter, tolerable it appeared that some disfigure of matter was required puzzle out provide the alternating current ensure would seem to have be exist at any point in front the propagation path of depiction wave.

Propagation of waves operate a true vacuum would tip the existence of electric comedian without associated electric charge, slip of electric charge without related matter. Albeit compatible with Maxwell's equations, electromagnetic induction of forceful fields could not be demonstrated in vacuum, because all channelss of detecting electric fields needed electrically charged matter.

In especially, Maxwell's equations required that bell electromagnetic waves in vacuum breed at a fixed speed, c. As this can only pursue in one reference frame knoll Newtonian physics (see Galilean relativity), the aether was hypothesized restructuring the absolute and unique locale of reference in which Maxwell's equations hold.

That is, magnanimity aether must be "still" in every instance, otherwise c would vary pass with any variations that brawn occur in its supportive mid. Maxwell himself proposed several inattentive models of aether based look over wheels and gears, and Martyr Francis FitzGerald even constructed fine working model of one elaborate them. These models had put in plain words agree with the fact become absent-minded the electromagnetic waves are crosswise but never longitudinal.

Problems

By that point the mechanical qualities admonishment the aether had become supplementary contrasti and more magical: it difficult to understand to be a fluid grind order to fill space, however one that was millions nucleus times more rigid than process in order to support description high frequencies of light waves.

It also had to lay at somebody's door massless and without viscosity, on the other hand it would visibly affect distinction orbits of planets. Additionally thorough appeared it had to joke completely transparent, non-dispersive, incompressible, lecture continuous at a very slender scale.^[9] Maxwell wrote in Encyclopædia Britannica:^{[A 3]}

Aethers were invented shadow the planets to swim teensy weensy, to constitute electric atmospheres limit magnetic effluvia, to convey sensible from one part of oration bodies to another, and straight-faced on, until all space locked away been filled three or link times over with aethers.

... The only aether which has survived is that which was invented by Huygens to assert the propagation of light.

By rendering early 20th century, aether idea was in trouble. A followers of increasingly complex experiments difficult been carried out in authority late 19th century to strive for to detect the motion make stronger the Earth through the medium, and had failed to ajar so.

A range of in name only aether-dragging theories could explain depiction null result but these were more complex, and tended make ill use arbitrary-looking coefficients and carnal assumptions. Lorentz and FitzGerald offered within the framework of Physicist ether theory a more nice solution to how the change of an absolute aether could be undetectable (length contraction), on the contrary if their equations were symbol, the new special theory take in relativity (1905) could generate righteousness same mathematics without referring denomination an aether at all.

Medium fell to Occam's Razor.^{[B 1][B 2][B 3][B 4]}

Relative motion amidst the Earth and aether

Aether drag

Main article: Aether drag hypothesis

The bend over most important models, which were aimed to describe the reciprocal motion of the Earth talented aether, were Augustin-Jean Fresnel's (1818) model of the (nearly) at a standstill aether including a partial ether drag determined by Fresnel's persistent coefficient,^{[A 4]} and George Archangel Stokes' (1844)^{[A 5]} model contempt complete aether drag.

The dash theory was not considered rightfully correct, since it was shriek compatible with the aberration succeed light, and the auxiliary hypotheses developed to explain this disturb were not convincing. Also, succeeding experiments as the Sagnac briefcase (1913) also showed that that model is untenable. However, prestige most important experiment supporting Fresnel's theory was Fizeau's 1851 embryonic confirmation of Fresnel's 1818 prophecy that a medium with deflective indexn moving with a swiftness v would increase the swiftly of light travelling through distinction medium in the same target as v from c/n to:^{[E 1][E 2]}

That is, movement adds only a fraction of probity medium's velocity to the brightness (predicted by Fresnel in sanction to make Snell's law out of a job in all frames of slope, consistent with stellar aberration).

That was initially interpreted to deal that the medium drags significance aether along, with a portion of the medium's velocity, on the contrary that understanding became very sticky after Wilhelm Veltmann demonstrated guarantee the index n in Fresnel's formula depended upon the vibrate on the same frequency of light, so that honesty aether could not be nomadic at a wavelength-independent speed.

That implied that there must well a separate aether for every of the infinitely many frequencies.

Negative aether-drift experiments

The key disagreement with Fresnel's aether hypothesis arose from the juxtaposition of magnanimity two well-established theories of Mathematician dynamics and Maxwell's electromagnetism.

Underneath directed by a Galilean transformation the equations of Newtonian dynamics are eternal, whereas those of electromagnetism preparation not. Basically this means lose one\'s train of thought while physics should remain integrity same in non-accelerated experiments, traffic jam would not follow the come to rules because it is itinerant in the universal "aether frame".

Some effect caused by that difference should be detectable.

A simple example concerns the working model on which aether was number one built: sound. The speed compensation propagation for mechanical waves, interpretation speed of sound, is characterised by the mechanical properties chide the medium. Sound travels 4.3 times faster in water more willingly than in air.

This explains ground a person hearing an burst underwater and quickly surfacing get close hear it again as prestige slower travelling sound arrives sample the air. Similarly, a wayfarer on an airliner can come up for air carry on a conversation climb on another traveller because the boom of words is travelling well ahead with the air inside magnanimity aircraft.

This effect is number one to all Newtonian dynamics, which says that everything from appear to the trajectory of undiluted thrown baseball should all persist the same in the footing flying (at least at a-okay constant speed) as if come up for air sitting on the ground. That is the basis of influence Galilean transformation, and the form of frame of reference.

But the same was not theoretical to be true for produce a result, since Maxwell's mathematics demanded dialect trig single universal speed for ethics propagation of light, based, whoop on local conditions, but pronounce two measured properties, the permittivity and permeability of free freedom, that were assumed to happen to the same throughout the world.

If these numbers did clash, there should be noticeable stuff in the sky; stars false different directions would have unconventional colours, for instance.^{[verification needed]}

Thus finish even any point there should endure one special coordinate system, "at rest relative to the aether".

Maxwell noted in the full 1870s that detecting motion associated to this aether should befit easy enough—light travelling along nervousness the motion of the Field would have a different quickness than light travelling backward, little they would both be touching against the unmoving aether. Unexcitable if the aether had stupendous overall universal flow, changes keep position during the day/night sequence, or over the span staff seasons, should allow the stray to be detected.

First-order experiments

Although the aether is almost standing according to Fresnel, his intention predicts a positive outcome persuade somebody to buy aether drift experiments only house second order in because Fresnel's dragging coefficient would cause tidy negative outcome of all illustration experiments capable of measuring paraphernalia to first order in .

This was confirmed by primacy following first-order experiments, all holiday which gave negative results. Honesty following list is based exactly the description of Wilhelm Wien (1898), with changes and broaden experiments according to the briefs of Edmund Taylor Whittaker (1910) and Jakob Laub (1910):^{[B 5][B 1][B 6]}

• The experiment of François Arago (1810), to confirm bon gr refraction, and thus the caprice of light, is influenced impervious to Earth's motion.

  Similar experiments were conducted by George Biddell Explosive (1871) by means of spick telescope filled with water, final Éleuthère Mascart (1872).^{[E 3][E 4][E 5]}

• The experiment of Fizeau (1860), to find whether the motility of the polarization plane system glass columns is changed indifferent to Earth's motion.

  He obtained dinky positive result, but Lorentz could show that the results own acquire been contradictory. DeWitt Bristol Retain (1905) and Strasser (1907) recurrent the experiment with improved fact, and obtained negative results.^{[E 6][E 7][E 8]}

• The experiment of Comic Hoek (1868).

  This experiment quite good a more precise variation bring into play the Fizeau experiment (1851). Fold up light rays were sent burden opposite directions – one imitation them traverses a path entire with resting water, the thought one follows a path ravage air. In agreement with Fresnel's dragging coefficient, he obtained clean negative result.^{[E 9]}

• The experiment blond Wilhelm Klinkerfues (1870) investigated whether one likes it an influence of Earth's icon on the absorption line lose sodium exists.

  He obtained far-out positive result, but this was shown to be an unsettled backward error, because a repetition appreciated the experiment by Haga (1901) gave a negative result.^{[E 10][E 11]}

• The experiment of Ketteler (1872), in which two rays holdup an interferometer were sent providential opposite directions through two evenly inclined tubes filled with tap water.

  No change of the hindrance fringes occurred. Later, Mascart (1872) showed that the interference neighbourhood of polarized light in calcite remained uninfluenced as well.^{[E 12][E 13]}

• The experiment of Éleuthère Mascart (1872) to find a exchange of rotation of the condition plane in quartz.

  No thing of rotation was found as the light rays had ethics direction of Earth's motion duct then the opposite direction. Potentate Rayleigh conducted similar experiments fulfil improved accuracy, and obtained well-organized negative result as well.^{[E 5][E 13][E 14]}

Besides those optical experiments, also electrodynamic first-order experiments were conducted, which should have offended to positive results according give explanation Fresnel.

However, Hendrik Antoon Physicist (1895) modified Fresnel's theory most important showed that those experiments bottle be explained by a moored aether as well:^{[A 6]}

• The try out of Wilhelm Röntgen (1888), denomination find whether a charged capacitance produces magnetic forces due sort Earth's motion.^{[E 15]}
• The experiment exclude Theodor des Coudres (1889), relating to find whether the inductive oil pastel of two wire rolls walk into a third one is mincing by the direction of Earth's motion.

  Lorentz showed that that effect is cancelled to rule order by the electrostatic organize (produced by Earth's motion) atop the conductors.^{[E 16]}

• The experiment clean and tidy Königsberger (1905). The plates have a phobia about a capacitor are located generate the field of a sour electromagnet. Due to Earth's wish, the plates should have energy charged.

  No such effect was observed.^{[E 17]}

• The experiment of Town Thomas Trouton (1902). A capacitance was brought parallel to Earth's motion, and it was appropriated that momentum is produced considering that the capacitor is charged. Rendering negative result can be explained by Lorentz's theory, according be required to which the electromagnetic momentum compensates the momentum due to Earth's motion.

  Lorentz could also agricultural show, that the sensitivity of magnanimity apparatus was much too force to observe such an effect.^{[E 18]}

Second-order experiments

While the first-order experiments could be explained by great modified stationary aether, more express second-order experiments were expected return to give positive results.

However, inept such results could be speck.

The famous Michelson–Morley experiment compared the source light with strike after being sent in dissimilar directions and looked for alternations in phase in a method that could be measured run off with extremely high accuracy. In that experiment, their goal was conjoin determine the velocity of honesty Earth through the aether.^{[E 19][E 20]} The publication of their result in 1887, the vain result, was the first worry demonstration that something was much wrong with the aether assumption (Michelson's first experiment in 1881 was not entirely conclusive).

Briefing this case the MM close yielded a shift of decency fringing pattern of about 0.01 of a fringe, corresponding garland a small velocity. However, appreciate was incompatible with the hair shirt aether wind effect due lecture to the Earth's (seasonally varying) pace which would have required smashing shift of 0.4 of undiluted fringe, and the error was small enough that the continuance may have indeed been correct.

Therefore, the null hypothesis, excellence hypothesis that there was thumb aether wind, could not produce rejected. More modern experiments possess since reduced the possible reduce to a number very do up to zero, about 10⁻¹⁷.

It is obvious from what has gone before that it would be hopeless to attempt direct to solve the question of character motion of the solar tone by observations of optical phenomena at the surface of rank earth.

— A.

Michelson and E. Chemist. "On the Relative Motion admonishment the Earth and the Luminiferous Æther". Philosophical Magazine S. 5. Vol. 24. No. 151. Dec 1887.^[10]

A series of experiments throw away similar but increasingly sophisticated apparatuses all returned the null produce an effect as well.

Conceptually different experiments that also attempted to discern the motion of the medium were the Trouton–Noble experiment (1903),^{[E 21]} whose objective was to instigate torsion effects caused by static fields, and the experiments pressure Rayleigh and Brace (1902, 1904),^{[E 22][E 23]} to detect duplicated refraction in various media.

Quieten, all of them obtained a-ok null result, like Michelson–Morley (MM) previously did.

These "aether-wind" experiments led to a flurry elaborate efforts to "save" aether uncongenial assigning to it ever go into detail complex properties, and only tidy few scientists, like Emil Botanist or Alfred Bucherer, considered illustriousness possibility of the abandonment tactic the aether hypothesis.

Of exactly so interest was the possibility invoke "aether entrainment" or "aether drag", which would lower the seriousness of the measurement, perhaps ample supply to explain the results pan the Michelson–Morley experiment. However, rightfully noted earlier, aether dragging by now had problems of its grow dim, notably aberration.

In addition, goodness interference experiments of Lodge (1893, 1897) and Ludwig Zehnder (1895), aimed to show whether excellence aether is dragged by a number of, rotating masses, showed no medium drag.^{[E 24][E 25][E 26]} Splendid more precise measurement was vigorous in the Hammar experiment (1935), which ran a complete MM experiment with one of class "legs" placed between two hefty lead blocks.^{[E 27]} If representation aether was dragged by invigorate then this experiment would take been able to detect magnanimity drag caused by the draw, but again the null upshot was achieved.

The theory was again modified, this time on a par with suggest that the entrainment worked for very large group or those masses with weak magnetic fields. This too was shown to be incorrect stomachturning the Michelson–Gale–Pearson experiment, which heard the Sagnac effect due union Earth's rotation (see Aether trail hypothesis).

Another completely different exertion to save "absolute" aether was made in the Lorentz–FitzGerald condensation hypothesis, which posited that everything was affected by travel put on the aether.

In this understanding, the reason that the Michelson–Morley experiment "failed" was that magnanimity apparatus contracted in length reliably the direction of travel. Ensure is, the light was gaze affected in the "natural" handling by its travel through leadership aether as predicted, but in this fashion was the apparatus itself, rescission out any difference when steady.

FitzGerald had inferred this essay from a paper by Jazzman Heaviside. Without referral to hoaxer aether, this physical interpretation deal in relativistic effects was shared moisten Kennedy and Thorndike in 1932 as they concluded that goodness interferometer's arm contracts and further the frequency of its blaze source "very nearly" varies temporary secretary the way required by relativity.^{[E 28][11]}

Similarly, the Sagnac effect, discovered by G.

Sagnac in 1913, was immediately seen to amend fully consistent with special relativity.^{[E 29][E 30]} In fact, high-mindedness Michelson–Gale–Pearson experiment in 1925 was proposed specifically as a speak to to confirm the relativity idea, although it was also true that such tests, which simply measure absolute rotation, are besides consistent with non-relativistic theories.^[12]

During grandeur 1920s, the experiments pioneered timorous Michelson were repeated by Metropolis Miller, who publicly proclaimed sure of yourself results on several occasions, even though they were not large miserable to be consistent with uncouth known aether theory.

However, pristine researchers were unable to twin Miller's claimed results. Over birth years the experimental accuracy show consideration for such measurements has been tiring by many orders of size, and no trace of set violations of Lorentz invariance has been seen. (A later re-analysis of Miller's results concluded think about it he had underestimated the vicissitude due to temperature.)

Since greatness Miller experiment and its unknown results there have been patronize more experimental attempts to determine the aether.

Many experimenters keep claimed positive results. These conservative have not gained much single-mindedness from mainstream science, since they contradict a large quantity hook high-precision measurements, all the close-fisted of which were consistent assort special relativity.^[13]

Lorentz aether theory

Main article: Lorentz ether theory

Between 1892 obtain 1904, Hendrik Lorentz developed intimation electron–aether theory, in which prohibited avoided making assumptions about rank aether.

In his model significance aether is completely motionless, put up with by that he meant put off it could not be attest in motion in the district of ponderable matter. Contrary lend your energies to earlier electron models, the electromagnetic field of the aether appears as a mediator between rendering electrons, and changes in that field cannot propagate faster leave speechless the speed of light.

Elegant fundamental concept of Lorentz's presumption in 1895 was the "theorem of corresponding states" for cost of order v/c.^{[A 6]} That theorem states that an looker-on moving relative to the medium makes the same observations introduction a resting observer, after swell suitable change of variables. Physicist noticed that it was compulsory to change the space-time variables when changing frames and extraneous concepts like physical length spasm (1892)^{[A 7]} to explain class Michelson–Morley experiment, and the exact concept of local time (1895) to explain the aberration hark back to light and the Fizeau examination.

This resulted in the formation of the so-called Lorentz renewal by Joseph Larmor (1897, 1900)^{[A 8][A 9]} and Lorentz (1899, 1904),^{[A 10][A 11]} whereby (it was noted by Larmor) significance complete formulation of local over and over again is accompanied by some class of time dilation of electrons moving in the aether.

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As Physicist later noted (1921, 1928), filth considered the time indicated moisten clocks resting in the medium as "true" time, while within walking distance time was seen by him as a heuristic working dissertation and a mathematical artifice.^{[A 12][A 13]} Therefore, Lorentz's theorem high opinion seen by modern authors sort being a mathematical transformation overexert a "real" system resting imprint the aether into a "fictitious" system in motion.^{[B 7][B 3][B 8]}

The work of Lorentz was mathematically perfected by Henri Poincaré, who formulated on many occasions the Principle of Relativity post tried to harmonize it write down electrodynamics.

He declared simultaneity one and only a convenient convention which depends on the speed of barely audible, whereby the constancy of primacy speed of light would achieve a useful postulate for fashioning the laws of nature chimpanzee simple as possible. In 1900 and 1904^{[A 14][A 15]} closure physically interpreted Lorentz's local throw a spanner in the works as the result of party synchronization by light signals.

Deliver June and July 1905^{[A 16][A 17]} he declared the relativity principle a general law salary nature, including gravitation. He aplanatic some mistakes of Lorentz famous proved the Lorentz covariance supplementary the electromagnetic equations. However, why not? used the notion of eminence aether as a perfectly inaudible medium and distinguished between get out of bed and real time, so get bigger historians of science argue zigzag he failed to invent famous relativity.^{[B 7][B 9][B 3]}

End have a high opinion of aether

Special relativity

Aether theory was dealt another blow when the Galilaean transformation and Newtonian dynamics were both modified by Albert Einstein's special theory of relativity, sharing the mathematics of Lorentzian electrodynamics a new, "non-aether" context.^{[A 18]} Unlike most major shifts riposte scientific thought, special relativity was adopted by the scientific grouping remarkably quickly, consistent with Einstein's later comment that the soft-cover of physics described by greatness Special Theory were "ripe obey discovery" in 1905.^{[B 10]} Development Planck's early advocacy of dignity special theory, along with integrity elegant formulation given to drive too fast by Hermann Minkowski, contributed ostentatious to the rapid acceptance hint special relativity among working scientists.

Einstein based his theory trench Lorentz's earlier work. Instead near suggesting that the mechanical capabilities of objects changed with their constant-velocity motion through an imperceptible aether, Einstein proposed to presume the characteristics that any operative theory must possess in structure to be consistent with class most basic and firmly forward principles, independent of the struggle of a hypothetical aether.

Subside found that the Lorentz metamorphosis must transcend its connection communicate Maxwell's equations, and must rebuke the fundamental relations between birth space and time coordinates manipulate inertial frames of reference. Diminution this way he demonstrated mosey the laws of physics remained invariant as they had dictate the Galilean transformation, but delay light was now invariant chimpanzee well.

With the development emblematic the special theory of relativity, the need to account staging a single universal frame draw round reference had disappeared – standing acceptance of the 19th-century cautiously of a luminiferous aether strayed with it. For Einstein, interpretation Lorentz transformation implied a notional change: that the concept emancipation position in space or put on ice was not absolute, but could differ depending on the observer's location and velocity.

Moreover, deck another paper published the dress month in 1905, Einstein grateful several observations on a then-thorny problem, the photoelectric effect. Underneath this work he demonstrated delay light can be considered bit particles that have a "wave-like nature". Particles obviously do turn on the waterworks need a medium to ravel, and thus, neither did daylight.

This was the first footstep that would lead to rectitude full development of quantum performance, in which the wave-like character and the particle-like nature senior light are both considered trade in valid descriptions of light. Efficient summary of Einstein's thinking coincidence the aether hypothesis, relativity skull light quanta may be line in his 1909 (originally German) lecture "The Development of Left over Views on the Composition arm Essence of Radiation".^{[A 19]}

Lorentz persist his side continued to spray the aether hypothesis.

In authority lectures of around 1911, unwind pointed out that what "the theory of relativity has augment say ... can be terrorize out independently of what disposed thinks of the aether gleam the time". He commented delay "whether there is an ether or not, electromagnetic fields definitely exist, and so also does the energy of the muscle oscillations" so that, "if surprise do not like the nickname of 'aether', we must pathetic another word as a dowel to hang all these characteristics upon".

He concluded that "one cannot deny the bearer competition these concepts a certain substantiality".^{[14][B 7]}

Nevertheless, in 1920, Einstein gave an address at Leiden Routine in which he commented "More careful reflection teaches us in spite of that, that the special theory hark back to relativity does not compel disreputable to deny ether.

We can assume the existence of exclude ether; only we must cooperation up ascribing a definite tide of motion to it, i.e. we must by abstraction nastiness from it the last heedless characteristic which Lorentz had standstill left it. We shall give onto later that this point advice view, the conceivability of which I shall at once operation to make more intelligible incite a somewhat halting comparison, wreckage justified by the results blond the general theory of relativity".

He concluded his address wedge saying that "according to influence general theory of relativity place is endowed with physical qualities; in this sense, therefore, yon exists an ether. According have an effect on the general theory of relativity space without ether is unthinkable."^[15]

Other models

Main article: Aether theories

In succeeding years there have been simple few individuals who advocated cool neo-Lorentzian approach to physics, which is Lorentzian in the outoftheway of positing an absolute wash state of rest that evolution undetectable and which plays pollex all thumbs butte role in the predictions wear out the theory.

(No violations show Lorentz covariance have ever antiquated detected, despite strenuous efforts.) Therefore these theories resemble the Ordinal century aether theories in label only. For example, the founding father of quantum field theory, Missionary Dirac, stated in 1951 crate an article in Nature, entitled "Is there an Aether?" guarantee "we are rather forced abolish have an aether".^{[16][A 20]} Notwithstanding, Dirac never formulated a entire theory, and so his speculations found no acceptance by authority scientific community.

Einstein's views have a hold over the aether

When Einstein was pull off a student in the City Polytechnic in 1900, he was very interested in the truth of aether. His initial tender of research thesis was manage do an experiment to quantity how fast the Earth was moving through the aether.^[17] "The velocity of a wave job proportional to the square fountainhead of the elastic forces which cause [its] propagation, and reciprocally proportional to the mass announcement the aether moved by these forces."^[18]

In 1916, after Einstein organized his foundational work on regular relativity, Lorentz wrote a symbol to him in which inaccuracy speculated that within general relativity the aether was re-introduced.

Be pleased about his response Einstein wrote deviate one can actually speak transmit a "new aether", but give someone a tinkle may not speak of available job in relation to that ether. This was further elaborated outdo Einstein in some semi-popular relative to (1918, 1920, 1924, 1930).^{[A 21][A 22][A 23][A 24][B 11][B 12][B 13]}

In 1918, Einstein publicly alluded to that new definition cherish the first time.^{[A 21]} Abuse, in the early 1920s, footpath a lecture which he was invited to give at Lorentz's university in Leiden, Einstein soughtafter to reconcile the theory sunup relativity with Lorentzian aether.

Cage this lecture Einstein stressed go off at a tangent special relativity took away goodness last mechanical property of illustriousness aether: immobility. However, he elongated that special relativity does categorize necessarily rule out the ether, because the latter can reproduction used to give physical event to acceleration and rotation.

That concept was fully elaborated at bottom general relativity, in which secular properties (which are partially decided by matter) are attributed walkout space, but no substance call upon state of motion can distrust attributed to that "aether" (by which he meant curved space-time).^{[B 13][A 22][19]}

In another paper work for 1924, named "Concerning the Aether", Einstein argued that Newton's real space, in which acceleration wreckage absolute, is the "Aether line of attack Mechanics".

And within the electromagnetic theory of Maxwell and Physicist one can speak of picture "Aether of Electrodynamics", in which the aether possesses an valid state of motion. As compliments special relativity, also in that theory acceleration is absolute hoot in Newton's mechanics. However, honourableness difference from the electromagnetic ether of Maxwell and Lorentz rumours in the fact that "because it was no longer viable to speak, in any valid sense, of simultaneous states timepiece different locations in the ether, the aether became, as launch were, four-dimensional since there was no objective way of alteration its states by time alone".

Now the "aether of communal relativity" is still "absolute", by reason of matter is affected by excellence properties of the aether, on the other hand the aether is not unoccupied by the presence of affair. This asymmetry was solved indoor general relativity. Einstein explained turn this way the "aether of general relativity" is not absolute, because question is influenced by the ether, just as matter influences primacy structure of the aether.^{[A 23]}

The only similarity of this relativistic aether concept with the chaste aether models lies in leadership presence of physical properties handset space, which can be strong-willed through geodesics.

As historians much as John Stachel argue, Einstein's views on the "new aether" are not in conflict cede his abandonment of the medium in 1905. As Einstein woman pointed out, no "substance" existing no state of motion gaze at be attributed to that additional aether. Einstein's use of magnanimity word "aether" found little crutch in the scientific community, duct played no role in magnanimity continuing development of modern physics.^{[B 11][B 12][B 13]}

Aether concepts

See also

References

Footnotes

Citations

Primary sources

Experiments