"I maintain that the cosmic religious feeling is the strongest and noblest motive for scientific research" - Albert Einstein ( 1879 - 1955 )
§ Or, what is the nature of light and how does it comes to our eyes?
According to Isaac Newton ( 1642 - 1727 ) in his "Opticks" ( 1704 ) light is transmitted at a finite speed by the "Luminiferous Aether Wind" which is the common or universal medium of propagation. This aether wind was further hypothesized as an absolute and stationary "frame of reference" for the measurement of time, especially as James Clerk Maxwell's ( 1831 - 1879 ) equations for electromagnetic radiation - including light - required it. [ aether : Latin: the upper rarified air reaching into the heavens; Greek: to glow, to burn ]
The Luminiferous Aether was imagined by physicists since Isaac Newton as the invisible "vapor" or "gas aether" filling the universe and hence as the carrier of heat and light to our eyes, although we now understand by Maxwell's equations that these are both a unified electromagnetic phenomena.
Further, the "Corpuscular Theory of Light" promulgated by Isaac Newton set forth the idea that light is composed of small discreet particles or corpuscles. In this sense, the corpuscular theory of light resembles the modern photon quanta, but the theory failed under conditions of "light interference" and "diffraction" or the bending of light.
According to Maxwell's equations, light is a self - propagating electromagnetic transverse wave with electric and magnetic components where the oscillating electric and magnetic field components induce their respective opposites and vice-versa. These electric and magnetic components oscillate at right angles to each other and propagate perpendicularly to the direction in which they indefinitely travel unless absorbed by intervening matter. That is, each kind of field - electric and magnetic - generates the other in order to propagate the entire composite structure moving forward through empty space at the finite speed of light, c.
Maxwell wrote in his "A Dynamical Theory of the Electromagnetic Field" ( 1864 ), pg. 499, part ( 97 ) [ note: pg. 41 of this pdf. ], the following:
"The agreement of the results seems to show that light and magnetism are affections of the same substance, and that light is an electromagnetic disturbance propagated through the field according to electromagnetic laws".
Light being a transverse wave therefore possesses a wavelength, frequency and velocity described simply as follows:
where the light wave still maintains a constant frequency, ƒ. That is, only wavelength and speed of light change when light passes thru a boundary of different materials and hence light frequency, ƒ, is an "invariant quantity" in the universe, notwithstanding or discounting any frequency changes due to any "Doppler Effect":
This inverse relationship between light frequency, ƒ, and wavelength, λ, was also visually observed and eventually measured:
As you can see the color violent has the shortest wavelength with the highest frequency while red has the longest of the visible light spectrum with an inverse lowest frequency as follows:
Finally, the Interference of light waves is the interaction of two or more light waves and producing a distinctly different light wave pattern such as
The type of light used in an interference experiment will be where the ( two ) light waves are correlated or "coherent" with each other in terms of the same light source and/or the same wave frequency. The most useful light for the purpose of creating interference patterns is sodium light, a monochromatic light which is produced in a rather narrow bandwidth of wavelength. An interferometer instrument is used for the purpose of producing "constructive" and "destructive" interference wave patterns which depend on the relative wave phases, frequencies or wavelengths, and amplitudes of the interacting light waves.
note: The red wave is moving left - to - right, the green wave is moving right - to - left. The resultant wave is black.
In the Michelson - Morley Experiment ( 1887 ) a single source of Sodium light is split into two coherent beams of light which in turn are bounced off of reflecting mirrors and then re - combined on a viewing screen in order to observe the pattern effects, if any, of the Luminiferous Aether upon these two beams of light as Earth traverses its solar orbit.
§ The Michelson - Morley Experiment ( 1887 ) or does a luminiferous aether really exist?
If the Luminiferous Aether Theory is correct, then as the Earth passes ( ≈ 18 mi/sec or 30 km/sec ) in its solar orbit thru the hypothesized stationary aether and by the Galilean addition of velocities of the Earth plus any velocity of light ( already known to be about 186,300 mi/sec ) emanating from the Michelson - Morley interferometer instrument on the Earth, therefore either "constructive" or "destructive" interference fringes will be detected.
In other words, if the hypothesized luminiferous aether exists, then there will be "destructive" interference fringes as the Earth transits thru it and the luminiferous aether thereby inhibits the flow of interferometer source light; in other aligned directions of Earth's passage thru the aether and the interferometer instrument itself ( remember that interferometer can be rotated 360° in its mercury bath ), there should appear "constructive" interference fringes. Hence, pointing one arm of the Michelson - Morley interferometer in the direction of Earth's transit orbit should produce an interference fringe pattern amounting to 0.4 fringe width where the instrument was sensitive to 0.01 fringe width. And in this way, it should be able to detect either the Earth's velocity thru the stationary aether or from the perspective of the laboratory, the velocity of the aether wind itself should be detected across a stationary Michelson - Morley interferometer.
§ The Michelson - Morley Interferometer:
§ Physical Characteristics:
§ Mathematics of the Michelson - Morley Interferometer:
§ How it was operated:
For each one (1) hour noon session on July 8, 9, and 11, 1887, Michelson and Morley carefully turned their interferometer thru 10° incremental rotations wherein they took calibrated readings every one-sixteenth of a 10° turn. Likewise, Michelson and Morley performed their interferometer experiment in the evenings of July 8, 9, and 12, 1887, for a total of six ( 6 ) hours.
§ What Michelson and Morley discovered:
Although Michelson and Morley had expected to measure different speeds of light ( anisotropies ) depending upon the orientation of the Earth in its orbital transit as well as for differing interferometer 10° rotations throughout a complete 360°, in fact their interferometer instrument produced no discernible interference fringes and therefore indicated no apparent motion of the Earth relative to the hypothesized luminiferous aether.
This was an incredible conclusion!
What this Michelson - Morley Experiment suggested was nothing less than revolutionary:
§ However, why all this should be was still left to some other explanations:
Polish - born, Jewish American Albert Abraham Michelson together with Prof. Edward Morley, M.D. and Phd., American chemical scientist, determined that c = 299,792,458 m/sec ( 186,265 miles per second ) is finite and that no aether [ ether ] exists for which Michelson became the first American in 1907 to receive a Nobel Prize in Physics. But this sort of discovery required a deeper mathematical physics than was presently available to them at the time.
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