A report on Luminiferous aether

The luminiferous aether: it was hypothesised that the Earth moves through a "medium" of aether that carries light

The Michelson–Morley experiment compared the time for light to reflect from mirrors in two orthogonal directions.

The postulated medium for the propagation of light.

- Luminiferous aether

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Figure 1. Michelson and Morley's interferometric setup, mounted on a stone slab that floats in an annular trough of mercury

Michelson–Morley experiment

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Figure 2. A depiction of the concept of the "aether wind"

Michelson's 1881 interferometer. Although ultimately it proved incapable of distinguishing between differing theories of aether-dragging, its construction provided important lessons for the design of Michelson and Morley's 1887 instrument.

Figure 5. This figure illustrates the folded light path used in the Michelson–Morley interferometer that enabled a path length of 11 m. a is the light source, an oil lamp. b is a beam splitter. c is a compensating plate so that both the reflected and transmitted beams travel through the same amount of glass (important since experiments were run with white light which has an extremely short coherence length requiring precise matching of optical path lengths for fringes to be visible; monochromatic sodium light was used only for initial alignment ). d, d' and e are mirrors. e' is a fine adjustment mirror. f is a telescope.

Figure 6. Fringe pattern produced with a Michelson interferometer using white light. As configured here, the central fringe is white rather than black.

Figure 7. Michelson and Morley's results. The upper solid line is the curve for their observations at noon, and the lower solid line is that for their evening observations. Note that the theoretical curves and the observed curves are not plotted at the same scale: the dotted curves, in fact, represent only one-eighth of the theoretical displacements.

Expected differential phase shift between light traveling the longitudinal versus the transverse arms of the Michelson–Morley apparatus

Figure 8. Simulation of the Kennedy/Illingworth refinement of the Michelson–Morley experiment. (a) Michelson–Morley interference pattern in monochromatic mercury light, with a dark fringe precisely centered on the screen. (b) The fringes have been shifted to the left by 1/100 of the fringe spacing. It is extremely difficult to see any difference between this figure and the one above. (c) A small step in one mirror causes two views of the same fringes to be spaced 1/20 of the fringe spacing to the left and to the right of the step. (d) A telescope has been set to view only the central dark band around the mirror step. Note the symmetrical brightening about the center line. (e) The two sets of fringes have been shifted to the left by 1/100 of the fringe spacing. An abrupt discontinuity in luminosity is visible across the step.

Figure 9. Michelson–Morley experiment with cryogenic optical resonators of a form such as was used by Müller et al. (2003).

Figure 10. 7Li-NMR spectrum of LiCl (1M) in D2O. The sharp, unsplit NMR line of this isotope of lithium is evidence for the isotropy of mass and space.

The Michelson–Morley experiment was an attempt to detect the existence of the luminiferous aether, a supposed medium permeating space that was thought to be the carrier of light waves.

Albert Einstein around 1905, the year his "Annus Mirabilis papers" were published. These included Zur Elektrodynamik bewegter Körper, the paper founding special relativity.

Special relativity

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1) The laws of physics are invariant (that is, identical) in all inertial frames of reference (that is, frames of reference with no acceleration).

Figure 2–1. The primed system is in motion relative to the unprimed system with constant velocity v only along the x-axis, from the perspective of an observer stationary in the unprimed system. By the principle of relativity, an observer stationary in the primed system will view a likewise construction except that the velocity they record will be −v. The changing of the speed of propagation of interaction from infinite in non-relativistic mechanics to a finite value will require a modification of the transformation equations mapping events in one frame to another.

Figure 4–1. The three events (A, B, C) are simultaneous in the reference frame of some observer O. In a reference frame moving at v = 0.3c, as measured by O, the events occur in the order C, B, A. In a reference frame moving at v = −0.5c with respect to O, the events occur in the order A, B, C. The white lines, the lines of simultaneity, move from the past to the future in the respective frames (green coordinate axes), highlighting events residing on them. They are the locus of all events occurring at the same time in the respective frame. The gray area is the light cone with respect to the origin of all considered frames.

Figure 5–1. Highly simplified diagram of Fizeau's 1851 experiment.

Figure 5–2. Illustration of stellar aberration

Figure 5–3. Transverse Doppler effect for two scenarios: (a) receiver moving in a circle around the source; (b) source moving in a circle around the receiver.

Figure 5–4. Comparison of the measured length contraction of a cube versus its visual appearance.

Figure 5-5. Galaxy M87 streams out a black-hole-powered jet of electrons and other sub-atomic particles traveling at nearly the speed of light.

Figure 10–1. Orthogonality and rotation of coordinate systems compared between left: Euclidean space through circular angle φ, right: in Minkowski spacetime through hyperbolic angle φ (red lines labelled c denote the worldlines of a light signal, a vector is orthogonal to itself if it lies on this line).

Figure 10–2. Three-dimensional dual-cone.

The incompatibility of Newtonian mechanics with Maxwell's equations of electromagnetism and, experimentally, the Michelson-Morley null result (and subsequent similar experiments) demonstrated that the historically hypothesized luminiferous aether did not exist.

The Lorentz factor γ as a function of velocity. It starts at1 and approaches infinity as v approaches c.

Speed of light

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Universal physical constant that is important in many areas of physics.

Event A precedes B in the red frame, is simultaneous with B in the green frame, and follows B in the blue frame.

The blue dot moves at the speed of the ripples, the phase velocity; the green dot moves with the speed of the envelope, the group velocity; and the red dot moves with the speed of the foremost part of the pulse, the front velocity.

A beam of light is depicted travelling between the Earth and the Moon in the time it takes a light pulse to move between them: 1.255 seconds at their mean orbital (surface-to-surface) distance. The relative sizes and separation of the Earth–Moon system are shown to scale.

Measurement of the speed of light using the eclipse of Io by Jupiter

Aberration of light: light from a distant source appears to be from a different location for a moving telescope due to the finite speed of light.

One of the last and most accurate time of flight measurements, Michelson, Pease and Pearson's 1930–35 experiment used a rotating mirror and a one-mile (1.6 km) long vacuum chamber which the light beam traversed 10 times. It achieved accuracy of ±11 km/s.

Electromagnetic standing waves in a cavity

An interferometric determination of length. Left: constructive interference; Right: destructive interference.

Rømer's observations of the occultations of Io from Earth

Hendrik Lorentz (right) with Albert Einstein

This invariance of the speed of light was postulated by Einstein in 1905, after being motivated by Maxwell's theory of electromagnetism and the lack of evidence for the luminiferous aether; it has since been consistently confirmed by many experiments.

Lodge's ether machine. Light from a sensitive common path interferometer was guided between the rapidly rotating disks.

Aether drag hypothesis

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Complete aether dragging is inconsistent with the phenomenon of stellar aberration. In this illustration, imagine the stars to be infinitely distant. Aberration occurs when the observer's velocity has a component that is perpendicular to the line traveled by the light incoming from the star. As seen in the animation on the left, the telescope must be tilted before the star will appear in the center of the eyepiece. As seen in the animation of the right, if the aether is dragged in the vicinity of the earth, then the telescope must be pointed directly at the star for the star to appear in the center of the eyepiece.

In the 19th century, the theory of the luminiferous aether as the hypothetical medium for the propagation of light waves was widely discussed.

Lorentz boost of an electric charge, the charge is at rest in one frame or the other.

Lorentz transformation

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In physics, the Lorentz transformations are a six-parameter family of linear transformations from a coordinate frame in spacetime to another frame that moves at a constant velocity relative to the former.

Early in 1889, Oliver Heaviside had shown from Maxwell's equations that the electric field surrounding a spherical distribution of charge should cease to have spherical symmetry once the charge is in motion relative to the luminiferous aether.

Hendrik Lorentz

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Dutch physicist who shared the 1902 Nobel Prize in Physics with Pieter Zeeman for the discovery and theoretical explanation of the Zeeman effect.

Painting of Hendrik Lorentz by Menso Kamerlingh Onnes, 1916.

Lorentz' theory of electrons. Formulas for the Lorentz force (I) and the Maxwell equations for the divergence of the electrical field E (II) and the magnetic field B (III), La théorie electromagnétique de Maxwell et son application aux corps mouvants, 1892, p. 451. V is the velocity of light.

Lorentz' theory of electrons. Formulas for the curl of the magnetic field (IV) and the electrical field E (V), La théorie electromagnétique de Maxwell et son application aux corps mouvants, 1892, p. 452.

Albert Einstein and Hendrik Antoon Lorentz, photographed by Ehrenfest in front of his home in Leiden in 1921.

Lorentz (left) at the International Committee on Intellectual Cooperation of the League of Nations, here with Albert Einstein.

His published university lectures in theoretical physics. Part 1. Stralingstheorie (1910-1911, Radiation theory) in Dutch, edited by his student A. D. Fokker, 1919.

Lorentz-monument Park Sonsbeek in Arnhem, the Netherlands

In 1892 and 1895, Lorentz worked on describing electromagnetic phenomena (the propagation of light) in reference frames that move relative to the postulated luminiferous aether.

Lorentz ether theory

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What is now often called Lorentz ether theory (LET) has its roots in Hendrik Lorentz's "theory of electrons", which was the final point in the development of the classical aether theories at the end of the 19th and at the beginning of the 20th century.

Portrait of Newton at 46 by Godfrey Kneller, 1689

Isaac Newton

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English mathematician, physicist, astronomer, alchemist, theologian, and author (described in his time as a "natural philosopher"), widely recognised as one of the greatest mathematicians and physicists of all time and among the most influential scientists.

Replica of Newton's second reflecting telescope, which he presented to the Royal Society in 1672

Illustration of a dispersive prism separating white light into the colours of the spectrum, as discovered by Newton

Facsimile of a 1682 letter from Isaac Newton to Dr William Briggs, commenting on Briggs' A New Theory of Vision.

Engraving of a Portrait of Newton by John Vanderbank

Newton's own copy of his Principia, with hand-written corrections for the second edition, in the Wren Library at Trinity College, Cambridge.

Isaac Newton in old age in 1712, portrait by Sir James Thornhill

Coat of arms of the Newton family of Great Gonerby, Lincolnshire, afterwards used by Sir Isaac.

Newton's tomb monument in Westminster Abbey

A Wood engraving of Newton's famous steps under the apple tree.

Newton statue on display at the Oxford University Museum of Natural History

Newton (1795, detail) by William Blake. Newton is depicted critically as a "divine geometer".

In his Hypothesis of Light of 1675, Newton posited the existence of the ether to transmit forces between particles.

Portrait of "Augustin Fresnel"
from the frontispiece of his collected works (1866)

Augustin-Jean Fresnel

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French civil engineer and physicist whose research in optics led to the almost unanimous acceptance of the wave theory of light, excluding any remnant of Newton's corpuscular theory, from the late 1830s until the end of the 19th century.

Monument to Augustin Fresnel on the facade of his birthplace at 2 Rue Augustin Fresnel, Broglie (facing Rue Jean François Mérimée), inaugurated on 14 September 1884. The inscription, when translated, says: "Augustin Fresnel, engineer of Bridges and Roads, member of the Academy of Sciences, creator of lenticular lighthouses, was born in this house on 10 May 1788. The theory of light owes to this emulator of Newton the highest concepts and the most useful applications."

Nyons, France, 19th century, drawn by Alexandre Debelle (1805–1897)

$Ordinary refraction from a medium of higher wave velocity to a medium of lower wave velocity, as understood by Huygens. Successive positions of the wavefront are shown in blue before refraction, and in green after refraction. For ordinary refraction, the secondary wavefronts (gray curves) are spherical, so that the rays (straight gray lines) are perpendicular to the wavefronts.$

Altered colors of skylight reflected in a soap bubble, due to thin-film interference (formerly called "thin-plate" interference)

$Printed label seen through a doubly-refracting calcite crystal and a modern polarizing filter (rotated to show the different polarizations of the two images)$

Bas-relief of Fresnel's uncle Léonor Mérimée (1757–1836), on the same wall as the Fresnel monument in Broglie

Replica of Young's two-source interference diagram (1807), with sources A and B producing minima at C, D, E, and F

Fresnel's double mirror (1816). The mirror segments M1 and M2 produce virtual images S1 and S2 of the slit S. In the shaded region, the beams from the two virtual images overlap and interfere in the manner of Young (above).

$Diffraction fringes near the limit of the geometric shadow of a straight edge. Light intensities were calculated from the values of the normalized integrals C(x), S(x)$

$Shadow cast by a 5.8mm-diameter obstacle on a screen 183cm behind, in sunlight passing through a pinhole 153cm in front. The faint colors of the fringes show the wavelength-dependence of the diffraction pattern. In the center is Poisson's/Arago's spot.$

A right-handed/clockwise circularly polarized wave as defined from the point of view of the source. It would be considered left-handed/anti-clockwise circularly polarized if defined from the point of view of the receiver. If the rotating vector is resolved into horizontal and vertical components (not shown), these are a quarter-cycle out of phase with each other.

Cross-section of a Fresnel rhomb (blue) with graphs showing the p component of vibration (parallel to the plane of incidence) on the vertical axis, vs. the s component (square to the plane of incidence and parallel to the surface) on the horizontal axis. If the incoming light is linearly polarized, the two components are in phase (top graph). After one reflection at the appropriate angle, the p component is advanced by 1/8 of a cycle relative to the s component (middle graph). After two such reflections, the phase difference is 1/4 of a cycle (bottom graph), so that the polarization is elliptical with axes in the s and p directions. If the s and p components were initially of equal magnitude, the initial polarization (top graph) would be at 45° to the plane of incidence, and the final polarization (bottom graph) would be circular.

Chromatic polarization in a plastic protractor, caused by stress-induced birefringence.

$Airy diffraction pattern 65mm from a 0.09mm circular aperture illuminated by red laser light. Image size: 17.3mm×13mm$

1: Cross-section of Buffon/Fresnel lens. 2: Cross-section of conventional plano-convex lens of equivalent power. (Buffon's version was biconvex. )

$Cross-section of a first-generation Fresnel lighthouse lens, with sloping mirrors m,n above and below the refractive panel RC (with central segment A). If the cross-section in every vertical plane through the lamp L is the same, the light is spread evenly around the horizon.$

First-order rotating catadioptric Fresnel lens, dated 1870, displayed at the Musée national de la Marine, Paris. In this case the dioptric prisms (inside the bronze rings) and catadioptric prisms (outside) are arranged to give a purely flashing light with four flashes per rotation. The assembly stands 2.54 metres tall and weighs about 1.5 tonnes.

Close-up view of a thin plastic Fresnel lens

Bust of Augustin Fresnel by David d'Angers (1854), formerly at the lighthouse of Hourtin, Gironde, and now exhibited at the Musée national de la Marine

The lantern room of the Cordouan Lighthouse, in which the first Fresnel lens entered service in 1823. The current fixed catadioptric "beehive" lens replaced Fresnel's original rotating lens in 1854.

But it was equally compatible with the wave theory, as Euler noted in 1746 – tacitly assuming that the aether (the supposed wave-bearing medium) near the earth was not disturbed by the motion of the earth.

Vacuum

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Space devoid of matter.

Torricelli's mercury barometer produced one of the first sustained vacuums in a laboratory.

The Crookes tube, used to discover and study cathode rays, was an evolution of the Geissler tube.

Structure of the magnetosphere - is not a perfect vacuum, but a tenuous plasma awash with charged particles, free elements such as hydrogen, helium and oxygen, electromagnetic fields.

A glass McLeod gauge, drained of mercury

Light bulbs contain a partial vacuum, usually backfilled with argon, which protects the tungsten filament

This shallow water well pump reduces atmospheric air pressure inside the pump chamber. Atmospheric pressure extends down into the well, and forces water up the pipe into the pump to balance the reduced pressure. Above-ground pump chambers are only effective to a depth of approximately 9 meters due to the water column weight balancing the atmospheric pressure.

Deep wells have the pump chamber down in the well close to the water surface, or in the water. A "sucker rod" extends from the handle down the center of the pipe deep into the well to operate the plunger. The pump handle acts as a heavy counterweight against both the sucker rod weight and the weight of the water column standing on the upper plunger up to ground level.

A cutaway view of a turbomolecular pump, a momentum transfer pump used to achieve high vacuum

This painting, An Experiment on a Bird in the Air Pump by Joseph Wright of Derby, 1768, depicts an experiment performed by Robert Boyle in 1660.

19th century experiments into this luminiferous aether attempted to detect a minute drag on the Earth's orbit.