A report on Luminiferous aether, Light and Michelson–Morley experiment

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

A triangular prism dispersing a beam of white light. The longer wavelengths (red) and the shorter wavelengths (blue) are separated.

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

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

The electromagnetic spectrum, with the visible portion highlighted

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.

Beam of sun light inside the cavity of Rocca ill'Abissu at Fondachelli-Fantina, Sicily

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.

$Due to refraction, the straw dipped in water appears bent and the ruler scale compressed when viewed from a shallow angle.$

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

Hong Kong illuminated by colourful artificial lighting.

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.

$Thomas Young's sketch of a double-slit experiment showing diffraction. Young's experiments supported the theory that light consists of waves.$

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.

Luminiferous aether or ether ("luminiferous", meaning "light-bearing") was the postulated medium for the propagation of light.

- Luminiferous aether

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.

- Michelson–Morley experiment

The negative outcome of the Michelson–Morley experiment (1887) suggested that the aether did not exist, a finding that was confirmed in subsequent experiments through the 1920s.

- Luminiferous aether

He proposed that light was emitted in all directions as a series of waves in a medium called the luminiferous aether.

- Light

The existence of the hypothetical substance luminiferous aether proposed by Huygens in 1678 was cast into strong doubt in the late nineteenth century by the Michelson–Morley experiment.

- Light

1 related topic with Alpha

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

All forms of electromagnetic radiation, including visible light, travel at the speed of light.

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.

Observations of the emissions from nuclear energy levels as a function of the orientation of the emitting nuclei in a magnetic field (see Hughes–Drever experiment), and of rotating optical resonators (see Resonator experiments) have put stringent limits on the possible two-way anisotropy.