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Michelson’s Experiment

The Michelson-Morley experiment attempted to detect the motion of matter relative to ether wind. However, this experiment failed and consequently it is referred as the failed experiment. The negative results obtained from the experiment provided evidence that opposed the prevalent ether theory. The failure of the experiment was the root of research that led to the special relativity. Further experiments have been performed from the time of Michelson but, all have proved that there is no ether wind at 10-17 level. The experiment struggled to establish the “wavelength of light as a standard of length.” Luminiferous ether was used in the experiment, and interferometric techniques were used to measure its properties. Initially, the experiment was set up using monochromatic light. It resulted into a uniform fringe pattern. To take the actual measurements, switching to white light was done. This was done since the results were virtually recorded. At the time there were no means of controlling the temperature, these prompted the experimentalists to set their interferometer in the basement. The observer faced external challenges that made the fringes disappear. The miscount provided by the observer was one source of error. The white light used solved some of these problems as it produced a distinct coloured pattern. According to Dayton miller, “White light fringes were chosen for the observations because they consist of a small group of fringes having a central, sharply defined black fringe forming a permanent zero reference mark for all readings.” During the initial alignment, partially monochromatic light was used as it enabled the researchers to determine the position of equal path length. It was mainly preferred as determining the location of equal path length was easy. When the path was accurately determined, they would switch to white light.

A mercury pool was used to reduce the effects of inertia. It allowed the device to be easily turned such that it would cover the entire angles of the ether wind. During the rotation, measurements were manually taken by observing through the eyepiece. The experiment worked under the assumption that an effect would be observed as the arms were to face in different directions. One was facing the direction of the wind while the other away. This effect was to be graphed as a sine wave with two peaks and troughs each time the device was rotated. This was true since during every rotation, the arms of the device were parallel and perpendicular to the wind twice. The earth’s rotation was another factor that affected the results of the experiment. The wind was not constant as it showed periodic changes in direction and magnitude. The vastness of the experiment predicted detectable yearly changes in the data obtained.

The conclusion provided by Michelson and Morley after their experiment depicted a contradiction to the former ether theory. Displacement is directly proportional to the square of the velocity. However, this experiment failed to prove this as it reported a small change in displacement for a large value of velocity. They estimated that the measured velocity was less than one-sixth of the Earths velocity in orbit. The measured velocity was considered to lie within the range of an experimental error that was equal to considering the speed as zero. This is because it was too small to small to be considered relevant for equating the speed of the ether. The failure of the ether experiment prompted Michelson and Morley to shift their calculations to the use of a technique that establishes the wavelength of light as a standard of length. The ether model experiments carried out during the time of Michelson and Morley refuted each other. The redo of the Fizeau experiment by Michelson and Morley opposed it theory of ether dragging. This was further contrary to an accurate experiment carried out in 1887. The 1887 experiment was further cemented by the results of the Trouton-Noble and Rayleigh experiments that showed complete ether dragging. These failures in science to come to an amicable and complete conclusion gave way to the development of the special relativity and Lorentz transformation theories.

The spatial relativity theory was proposed by Albert Einstein in 1905 as the physical theory of measurement in an internal frame of reference. He was extending the Galileo’s principle of relativity which states;”The laws of motion are similar in all internal frames.” Einstein was motivated to account for the speed of light that the Michelson experiment had failed to prove. This was based on the laws of physics both in mechanics and electrodynamics. Experiments have been carried out to verify the consequences of the theory. Some of these experiments are counter-intuitive such as the time dilation and length contraction theory. The postulates of special relativity theory merge with the laws of physics to provide the notion of invariant time and space interval. It is used to predict the mass and energy as they appear in the equivalence of mass and energy formula E=mc2. The speed of light in a vacuum is represented by c. The theory of special relativity reveals that the velocity of light is a fundamental feature that reflects the way space and time are unified. These predictions of special relativity augur well with the Newton’s mechanics and their area of application. A proof by this theory shows that it is impossible for any particle that posses rest mass to be accelerated at the speed of light. The theory applied the principle of relativity to inertial reference frames. Einstein provided a more general principle for application in general coordinate transformations. These general cases mainly refer to cases where gravity does not occur.

Based on Maxwell’s equations, many scientists believed that light was a modulation of some kind of medium. This was called the luminiferous ether and was used to distinguish it from any type of liquid. This ether was believed to lack molecules of matter that move around. Prior to Michelson experiment, it was thought to be rigid. Assumptions were made that the ether was stationary and that the earth orbited through it was opposed by the experiment. The Michelson Morley experiment had a direct influence on Einstein’s theory. The ether dragging effect proposed by Michelson was opposed by the stationary conclusion that Einstein provided. However, the contradiction was resolve as Einstein was able to proof the stationary theory. Einstein incorporated time as a factor to the coordinate system previously proposed by Michelson. It was the inclusion of this variable that made the construction of space time available. The revolution of this is that time flow in the universe differs depending on one’s reference frame.

Failures in experiments provide a framework for further scientific research. It was the failed Michelson Morley experiment that motivated Albert Einstein establishes the mathematical framework that described the propagation of light through space-time. It was also the basis for the Lorentz, Poincare and Fitzgerald experiments. The experiment also marked the turning point in the history of physics. The design of the interferometer was unique due to it precision with which it performed the experiments. The apparatus had the ability of detecting with approximation, one hundred million in average speed of light travel along the arms of the interferometer. Modern applications of the Michelson experiment include the interferometer that is used to measure the wavelengths of unknown monochromatic light. Another later development from the Michelson Morley experiment is the Michelson Interferometer for passive Atmospheric Sounding (MIPAS). Developed in 2002, the device provides detailed information concerning the chemistry of the atmosphere. It does this by observing the emission spectra in the near to the far mid-infrared range.

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