Biografie[ bewerken brontekst bewerken ] Michelson werd geboren in een joods gezin. Op driejarige leeftijd emigreerde hij met zijn ouders, Samuel en Rosalie Przlubska Michelson naar de Verenigde Staten. Tijdens zijn middelbareschooljaren verbleef hij bij zijn tante, Henriette Levy — de moeder van schrijfster Harriet Lane Levy. In verkreeg hij van president Ulysses S. Grant een speciale aanstelling bij de United States Naval Academy. Gedurende zijn vier jaren als adelborst aan de academie excelleerde Michelson in optica, warmte, klimatologie en tekenkunst.
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Because light can travel through a vacuum, it was assumed that even a vacuum must be filled with aether. Because the speed of light is so great, and because material bodies pass through the aether without obvious friction or drag, it was assumed to have a highly unusual combination of properties. Designing experiments to investigate these properties was a high priority of 19th century physics. A depiction of the concept of the "aether wind" According to the stationary and the partially-dragged aether hypotheses, Earth and the aether are in relative motion, implying that a so-called "aether wind" Fig.
By analyzing the return speed of light in different directions at various different times, it was thought to be possible to measure the motion of the Earth relative to the aether. The expected relative difference in the measured speed of light was quite small, given that the velocity of the Earth in its orbit around the Sun has a magnitude of about one hundredth of one percent of the speed of light. A number of physicists therefore attempted to make measurements of indirect first-order effects not of the speed of light itself, but of variations in the speed of light see First order aether-drift experiments.
The Hoek experiment , for example, was intended to detect interferometric fringe shifts due to speed differences of oppositely propagating light waves through water at rest. The results of such experiments were all negative. Partial aether-dragging would thwart attempts to measure any first order change in the speed of light.
As pointed out by Maxwell , only experimental arrangements capable of measuring second order effects would have any hope of detecting aether drift, i. In , while teaching at his alma mater, the United States Naval Academy in Annapolis, Michelson conducted his first known light speed experiments as a part of a classroom demonstration. In , he left active U. Naval service while in Germany concluding his studies. In that year, Michelson used a prototype experimental device to make several more measurements.
The device he designed, later known as a Michelson interferometer , sent yellow light from a sodium flame for alignment , or white light for the actual observations , through a half-silvered mirror that was used to split it into two beams traveling at right angles to one another. After leaving the splitter, the beams traveled out to the ends of long arms where they were reflected back into the middle by small mirrors.
They then recombined on the far side of the splitter in an eyepiece, producing a pattern of constructive and destructive interference whose transverse displacement would depend on the relative time it takes light to transit the longitudinal vs. If the Earth is traveling through an aether medium, a light beam traveling parallel to the flow of that aether will take longer to reflect back and forth than would a beam traveling perpendicular to the aether, because the increase in elapsed time from traveling against the aether wind is more than the time saved by traveling with the aether wind.
He did not observe the expected shift; the greatest average deviation that he measured in the northwest direction was only 0. Definitive measurement of the aether wind would require an experiment with greater accuracy and better controls than the original.
Nevertheless, the prototype was successful in demonstrating that the basic method was feasible. This figure illustrates the folded light path used in the Michelson—Morley interferometer that enabled a path length of 11 m. Michelson suffered a nervous breakdown in September , from which he recovered by October Morley ascribed this breakdown to the intense work of Michelson during the preparation of the experiments.
Michelson and Morley created an improved version of the Michelson experiment with more than enough accuracy to detect this hypothetical effect. The experiment was performed in several periods of concentrated observations between April and July , in the basement of Adelbert Dormitory of WRU later renamed Pierce Hall, demolished in At this length, the drift would be about 0.
To make that easily detectable, the apparatus was assembled in a closed room in the basement of the heavy stone dormitory, eliminating most thermal and vibrational effects.
Vibrations were further reduced by building the apparatus on top of a large block of sandstone Fig. They estimated that effects of about 0. Figure 6. Fringe pattern produced with a Michelson interferometer using white light. As configured here, the central fringe is white rather than black. Michelson and Morley and other early experimentalists using interferometric techniques in an attempt to measure the properties of the luminiferous aether, used partially monochromatic light only for initially setting up their equipment, always switching to white light for the actual measurements.
The reason is that measurements were recorded visually. Purely monochromatic light would result in a uniform fringe pattern. Lacking modern means of environmental temperature control , experimentalists struggled with continual fringe drift even when the interferometer was set up in a basement.
Because the fringes would occasionally disappear due to vibrations caused by passing horse traffic, distant thunderstorms and the like, an observer could easily "get lost" when the fringes returned to visibility.
The advantages of white light, which produced a distinctive colored fringe pattern, far outweighed the difficulties of aligning the apparatus due to its low coherence length.
As Dayton Miller wrote, "White light fringes were chosen for the observations because they consist of a small group of fringes having a central, sharply defined black fringe which forms a permanent zero reference mark for all readings. The hypothesis of aether drift implies that because one of the arms would inevitably turn into the direction of the wind at the same time that another arm was turning perpendicularly to the wind, an effect should be noticeable even over a period of minutes.
The expectation was that the effect would be graphable as a sine wave with two peaks and two troughs per rotation of the device. This result could have been expected because during each full rotation, each arm would be parallel to the wind twice facing into and away from the wind giving identical readings and perpendicular to the wind twice. Because of the motion of the Earth around the Sun, the measured data were also expected to show annual variations.
Most famous "failed" experiment[ edit ] Figure 7. 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.
After all this thought and preparation, the experiment became what has been called the most famous failed experiment in history. The expected deviation of the interference fringes from the zero should have been 0. The Fizeau experiment and its repetition by Michelson and Morley apparently confirmed the stationary aether with partial aether dragging, and refuted complete aether dragging.
On the other hand, the much more precise Michelson—Morley experiment apparently confirmed complete aether dragging and refuted the stationary aether. These problems and their solution led to the development of the Lorentz transformation and special relativity.
After the "failed" experiment Michelson and Morley ceased their aether drift measurements and started to use their newly developed technique to establish the wavelength of light as a standard of length. It passes through the half-silvered mirror at the origin at T.
Esperimento di Michelson-Morley
Interferômetro de Michelson
Introducción al experimento de Michelson y Morley
Experimento de Michelson y Morley