Michelson-Morley Experiment

10 Key excerpts on "Michelson-Morley Experiment"

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  Special Relativity

  • A.P. French(Author)
  • 2017(Publication Date)
  • CRC Press

    (Publisher)

  It is this refined version of the experiment, performed in 1887, 2 that has long been regarded as one of the main experimental pillars of special relativity. See pages 52 and 53 for a diagram of the Michelson-Morley apparatus and a sample of the results. 1 A. A. Michelson, Am. J. Sci, 122, 120 (1881). 2 A. A. Michelson and E. W. Morley, Am. J. Sci., 134, 333 (1887). Concluding Remarks The phenomena we have described in this chapter are such as to cause a strong sense of frustration in anyone who wishes to hold to the picture of light as waves in the ether. Every experiment designed to reveal our motion through this medium has the same result as though no motion existed or as though the medium itself did not exist. The result of the Michelson-Morley Experiment, like stellar aberration, is readily explained in terms of a ballistic model of light, in which the speed is uniquely defined with respect to the source, not with respect to a medium. It would be in perfect accord with what Galileo first recognized—that motions on a uniformly moving ship or other inertial reference frame do not, as observed within that frame, reveal any information about the velocity with which the whole system is translated. But in the view of most physicists at the end of the 19th century a particle model was not relevant; one had to seek the explanations in the context of what seemed to be clearly a problem in wave propagation. 1 And looking at the evidence, one could see that the only observations which did not give null results were those in which well-defined relative velocities were involved. In stellar aberration it was the velocity of the earth at some point in its orbit relative to the velocity at some other point. In the Fizeau experiment it was the velocity of the flowing water relative to the rest of the apparatus

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  Philosophy and the New Physics

  • Jonathan H Powers(Author)
  • 2023(Publication Date)
  • Routledge

    (Publisher)

  Thus the Michelson-Morley Experiment has had a checkered history. The practical problems with it were not completely sorted out until seventy-six years after it had first been performed, and in any event the result was capable of being explained in a variety of ways. We have met three aether-theoretic explanations of the result: Stokes’s entrained aether hypothesis, FitzGerald’s contraction hypothesis and Lorentz’s later theory. In addition to these Walther Ritz proposed a quite different kind of explanation in 1908, according to which light should be envisaged as a stream of energy whose velocity is dependent on the velocity of the source. Thus the speed of the light emitted by the lamp on the Michelson-Morley apparatus remains constant relative to the apparatus no matter what its state of motion. In principle it would have been open for someone to argue that the experiment undid the Copernican Revolution and showed that the earth might after all be at rest in the centre of the universe! Obviously one would wish to limit the damage done by interpreting the experiment and any suggestion of a return to an earth-centred astronomy would have been ludicrous. But there were viable alternative explanations at the turn of the century, and one of them - Lorentz’s later theory -remained unscathed by the experimental results which finally cut down the others. Whence, then, the resilience of the official account which gives the Michelson-Morley Experiment the credit for the overthrow of the aether and the proof of Einstein’s Light Postulate?

  Some have argued that the official account arises from a commitment to ‘experimentalism’,42 the dogma that all theoretical postulates must be directly derivable from experimental results. Those who have wanted to wean scientific education away from a treadmill of traditional laboratory work and restore the role of imagination in science, have made much of the fact that Michelson was a life-long believer in the aether, and that amongst Einstein’s equivocal remarks on the subject is the assertion that it had a ‘negligible influence’ on relativity.43

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  Gravity from the Ground Up

  An Introductory Guide to Gravity and General Relativity

  • Bernard Schutz(Author)
  • 2003(Publication Date)
  • Cambridge University Press

    (Publisher)

  And it is being developed further today to detect one of the most significant predictions of general relativity: gravitational waves. We will look closely at this instrument in the next section. This discussion will prepare us for studying gravitational waves and their detection, in Chapter 22. Michelson invented the interferometer to perform his first experiment on light in 1881. This produced such an unexpected result that he repeated it with greater precision with his American collaborator Edward W Morley (1838–1923) in 1887. The aim was to show that light had a different speed relative to the laboratory when it traveled in the direction of the Earth’s motion than when it moved in a perpen- dicular direction. In fact, Michelson expected it to be slower along the Earth’s motion than across The Michelson-Morley Experiment: light presents a puzzle 185 it. From Maxwell’s theory, physicists knew that light was a wave, and that it was just a short-wavelength version of radio or other electromagnetic waves. For most physicists, if something was a wave then it had to be a vibration in something, and they called this medium the ether. This was a hypothetical substance whose vibrations were light waves. The problem with the ether was that it had to be everywhere, in order to carry light to us from the distant stars, and yet there was no independent evidence for it. For example, if the planets were moving through the ether on their orbits around the Sun, why did it not slow them down? Why did the planets follow Newton’s laws so exactly? To get around this, physicists had to assume that the ether was frictionless, unlike any other substance known. Many physicists were uncomfortable with such implausible properties, and in fact it was Einstein’s own discomfort that led him to throw out the idea of the ether and embrace the invariance of the speed of light. But in the 1880s physicists were not ready for this.

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  Relativistic Flight Mechanics and Space Travel

  • Richard F. Tinder, Richard Tinder(Authors)
  • 2022(Publication Date)
  • Springer

    (Publisher)

  Phenomenologically, this was viewed as a “drag” on the velocity of light which either increased or decreased a little from the stationary liquid value of c / n depending on the liquid flow with or against the propagation direction of light, respectively. These experiments provided the backdrop for the famed Michelson–Morley experiment that follows. In 1887, about 36 years following Fizeau’s experiments, the physicist Albert Michelson and his assistant Edward Morley set about to show that the velocity of light would change if that light were to propagate through an ether wind thought to exist by virtue of the earth’s motion about the sun. The thinking of the time was that the influence of the ether wind (see Glossary) would affect the velocity of light in a manner similar to the effect on the light propagation through a moving liquid as demonstrated by Fizeau. Hence, if no ether wind existed, no velocity change would be observed. To better understand the Michelson–Morley experiment, we consider a thought exper- iment featuring two round trips of a boat in a river. First, let the round trip be between two points A and B parallel to the bank of the river, then let the second round trip be between two points on opposite sides of the river. These two round trips are depicted in Figs. 2.1(a) and (b), respectively, where v is the surface velocity of the river, V is the velocity of the boat, and L is the distance between the two points A and B and between the two points A and B. In Fig. 2.1(a) the time for the round trip is easily found to be t A ↔B = L V + v + L V − v = 2 L/ V (1 − v 2 / V 2 ) (2.3) for v < V . Now, if the boat is launched at point A to reach point B in Fig. 2.1(b), it must move along a path to point C so as to compensate for river current, v, when the boat velocity is again set at V . Noting that distances and velocities form similar right triangles, it follows that BC / AC = v/ V so that ( AC ) 2 = ( AB) 2 + ( BC ) 2 = ( AB) 2 + ( AC ) 2 · v 2 V 2 .

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  Michelson–Morley Experiments

  An Enigma for Physics and the History of Science

  • Maurizio Consoli, Alessandro Pluchino(Authors)
  • 2018(Publication Date)
  • WSPC

    (Publisher)

  v respectively so that

  where β = v/c. On the other hand, if the same path length D were in the perpendicular direction the corresponding time would now be1 t2 = 2D/c. Therefore, by estimating the velocity of the earth in the ether to be comparable to its orbital velocity v ∼ 30 km/s, and expanding in powers of β2 = v2 /c2 , one finds a relative difference

  This effect was considered by Maxwell too small to be observed. However, later on, Maxwell’s idea was taken seriously by Michelson and became the great challenge of his research.

  3.2 Albert A. Michelson and his first 1881 experiment

  Albert Abraham Michelson was born in Strzelno (now Poland at that time Prussia) on December 19, 1852 into a Polish-Jewish family. In 1855 the family emigrated to United States, first to New York City and then to San Francisco where he attended the high school. In 1869 he entered the U. S. Naval Academy where he graduated in 1873. After spending two years on board of different ships, Michelson served as a physics teacher at Annapolis where he made his first determination of the speed of light with a demonstration for the students in November 1877. In 1879 he was transferred to the Nautical Almanac Office in Washington D. C. . There Simon Newcomb was the leading scientist who provided ample support for all Michelson’s subsequent researches.

  Robert Shankland [97 ] observes that, perhaps, the most important event occurring for Michelson while he was at the Nautical Almanac Office was his opportunity to study a letter dated 19 March 1879 from James Clerk Maxwell to David Peck Todd, then also a researcher associated with the same Office. The most relevant part of this letter was Maxwell’s statement that “in the terrestrial methods of determining the velocity of light, the light comes back along the same path again, so that the velocity of the earth with respect to the ether would alter the time of the double passage by a quantity depending on the square of the ratio of the earth velocity to that of light, and this is quite too small to be observed” [97

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  The Basics of Physics

  • Richard L. Myers(Author)
  • 2005(Publication Date)
  • Greenwood

    (Publisher)

  The experiment relied on Michelson's knowl- edge of measuring the speed of light. The Michelson interferometer is depicted sche- matically in Figure 15.5. Michelson had perfected his interferometer over the years to make very precise measurements. The actual interferometer Michelson used had a number of mirrors so that the light beams were reflected several times across the inter- ferometer, extending the path length to 11 m before arriving at the detector. The interfer- ometer was mounted on a square sandstone block that measured 1.5 m on each side. The sandstone block rested on a wooden disk and floated in a pool of mercury contained in a cast iron tank. The massive block resting in mercury allowed the apparatus to be rotated through 360° with very little vibration. In the summer of 1887, Michelson and Morley made measurements with the interferometer in the basement of Western Reserve University. The specific measure- ment that was made was to observe the inter- ference pattern created by the light waves at the detector. If the light wave arrived at dif- ferent times, interference fringes would be observed. Michelson and Morley observed the interference pattern with the instrument in different positions. An observation was made, and then the interferometer would be rotated to a new position and another observation made. Since the Earth orbited Relativity 279 the Sun at 30 km/s, it was believed that light traveling with and against the ether wind would travel slower than light that traveled perpendicular to the ether wind. Michelson and Morley were unable to detect the ether wind no matter how the instrument was oriented or what time of the year the experiment was conducted. The inability to detect the ether puzzled both Michelson and Morley. Michelson thought there may have been an unknown flaw in the experiment.

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  The Science of Light

  From Galileo’s Telescope to Quantum Physics

  • Serge Haroche(Author)
  • 2023(Publication Date)
  • Odile Jacob

    (Publisher)

  Light played an essential role in this revolution in physics. The resolution of the mysteries hidden behind Lord Kelvin’s clouds would not only illuminate light in a new way, but also apply to all phenomena in physics, radically altering the stage on which physicists observed the world. The symbiosis between theory and experimentation, between blue sky research based on pure curiosity and advances in technology, were also essential in this revolution, as it was in previous centuries. Progress was decisive in instrumentation, from radiation detectors such as bolometers, which measure the heat exchange between light and matter, to those based on the newly discovered photoelectric effect. Advances in interferometers for measuring very small displacements of interference fringes played an important role as well. And, as always, so did luck.

  Luck was certainly behind the arrival in our story of a young employee of the Swiss Patent Office in Bern, who had a brilliant intuition and in a few years found himself propelled into the firmament of physics. At the beginning of the twentieth century, Albert Einstein orchestrated the great changes that the theories of relativity and of quanta would bring about. His imprint on modern physics is so strong that for over a century there would be hardly a discovery or an invention that did not, in one aspect or another, lead us back to him. Proof of his genius also lies in the great questions about our universe, still unresolved, that he helped formulate. Of course, Einstein was not alone in this adventure, which unites a great many remarkable scientists. But to give unity to our story I will place Einstein at its center, and describe this physics through the prism of his thought.

  Michelson and the puzzle of the aether

  Let’s start with Lord Kelvin’s first cloud. The American physicist Albert Michelson, with the aid of his compatriot Edward Morley, had attempted, in a series of experiments between 1881 and 1887, to measure the velocity of the Earth relative to the luminiferous aether, as the medium in which light supposedly propagated at the speed c of 300,000 km/s was known. The experiment, similar to the one Fizeau had done in 1852 to measure the velocity of light in a flowing liquid, was performed using a special interferometer that Michelson developed and which has since been named for him.

  A light beam was divided into two branches by a semi-reflective beam splitter, creating two beams that propagated at right angles to each other toward two mirrors that reflected the light back to the beam splitter. The light beams which recombined on the beam splitter interfered with each other. When the interferometer was adjusted so that the wavefronts from the two beams coincided exactly, one would ideally see behind the beam splitter, in the output path orthogonal to the input, a flat tint, bright when the path difference between the two beams was an integer number of wavelengths and dark when this path difference was an odd number of half wavelengths.

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  New Perspective On Relativity, A: An Odyssey In Non-euclidean Geometries

  An Odyssey in Non-Euclidean Geometries

  • Bernard H Lavenda(Author)
  • 2011(Publication Date)
  • World Scientific

    (Publisher)

  Only observations which do not give a null effect are those in which absolute velocities are involved, as in the Fizeau experiment. 3.2 Michelson–Morley Null Result: Is Contraction Real? The experimental set-up shown in Fig. 3.2 appeared in the ‘classic’ 1887 paper of Michelson and Morley. Light is emitted from a source and is reflected by a mirror at distance 1 . The time it takes for the forward and backward journeys can be found in any text, t 1 = 1 c + u + 1 c − u = 2 1 / c (1 − u 2 / c 2 ) , (3.2.1) A Brief History of Light, Electromagnetism and Gravity 113 Fig. 3.2. Monochromatic, yellow light is split by a mirror into two beams. These beams cover equal distances to mirrors b and c where they are reflected back to a , and then combined to produce interference fringes. The paths lengths ab = ac = 11 m. A rotation of the apparatus by 90 degrees gave no displacement of the interference fringes that was expected because the beam traveling along ab is parallel to the Earth’s motion through the aether while the ray along ac was normal to it. where u is the speed that Michelson’s apparatus is moving with respect to the inertial frame defined by the aether. To calculate the time of transit of the light ray perpendicular to the ‘aether wind,’ the Galilean composition of velocities is used. If c is the hypotenuse with base u , the decrease in velocity between the interferometer and the second mirror is √ ( c 2 − u 2 ). The time of transit of the outward and backward journeys from the second mirror is t 2 = 2 2 √ ( c 2 − u 2 ) . (3.2.2) From (3.2.1) and (3.2.2) Michelson determined the time difference. This time difference was compared to that which is resulted when the whole apparatus is rotated by 90 ◦ , which interchanges 1 with 2 . The dif-ference between the time differences would produce a shift in the inter-ference pattern, which is calculated in terms of the number of fringes, just 114 A New Perspective on Relativity as in the Fizeau experiment.

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  Questioning the Universe

  Concepts in Physics

  • Ahren Sadoff(Author)
  • 2008(Publication Date)
  • Chapman and Hall/CRC

    (Publisher)

  There is one other detail that must be mentioned. Because of all the different motions the earth is undergoing, Michelson had no idea of the true direction of motion through the ether. In the words of our boat analogy, he did not know what was up- or downstream or cross stream. He fully realized this, so he mounted the interferometer in a big vat of mercury so he could easily rotate the entire apparatus. In fact, what he expected was that he would observe a time difference between dif-ferent orientations of the interferometer. Michelson performed the experiment in 1881. The result was that he could not detect any measurable time difference for any orientation. This was not what was expected. So, what do we do now? In some respect, this is similar to the predica-ment that we had when discussing beta decay in Chapter 10, where the measured energy distribution for the electrons did not agree with the expected distribution. In that case, we saw that the first explanation was that the experiment was just wrong. For the Michelson experiment the situation is somewhat different since Michelson had calibrated his intererometer introducing known time delays that he could then measure. So, he knew the apparatus was working correctly. But maybe it was not sensitive enough to measure the effect. After all, it was designed to be able to just barely measure a time difference corresponding to the speed of the earth around the sun. What if the true speed was less than that? The Theory of Relativity 129 The problem Michelson faced was how to make his interferometer more sensi-tive. If we look at Equation 12.8, we see that the only quantity that Michelson could change was d, the length of the interferometer arms; u was what he was trying to measure, and the value of c, the speed of light, is fixed by nature. The larger the value of d, the larger the time difference would be.

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  The Heavens on Earth

  Observatories and Astronomy in Nineteenth-Century Science and Culture

  • David Aubin, Charlotte Bigg, H. Otto Sibum, David Aubin, Charlotte Bigg, H. Otto Sibum, Barbara Herrnstein Smith, E. Roy Weintraub(Authors)
  • 2010(Publication Date)
  • Duke University Press Books

    (Publisher)

  45. A. A. Michelson, “A Plea for Light Waves,” Proceedings of the American Association for the Advancement of Science 37 (1889): 67–78, at 67–69. 46. Michelson, “A Plea for Light Waves,” 74. 47. For these descriptions see A. A. Michelson and E. W. Morley, “On the Feasi-bility of Establishing a Light-Wave as the Ultimate Standard of Length,” Ameri-can Journal of Science 38 (1889): 181–86; A. A. Michelson, “Comparison of the International Meter with the Wave Length of the Light of Cadmium,” Astronomy and Astrophysics 12 (1893): 556–60, at 560. 48. When his student Frank Baldwin Jewett chose to join what later became the Bell Telephone Laboratories, Michelson described such industrial research as “pros-tituted physics.” See Nathan Reingold, “Physics and Engineering in the United States, 1945–1965: A Study of Pride and Prejudice,” The Michelson Era in American Science , ed. Goldberg and Stuewer, 288–98, at 288–89; S. Weart, “The Rise of ‘Prostituted’ Physics,” Nature 262 (1976): 13–17. 49. A. A. Michelson, “Measurement by Light-Waves,” American Journal of Science 39 (1890): 115–21. 50. Ibid., 116–18. 51. Michelson was primarily concerned with the pragmatic unity of method that he could advance by promoting the interferometer as an instrument, but Maxwell’s electromagnetic theory of light had invested particular importance in understand-ing the medium that transmits electromagnetic disturbances. Later Michelson described the grand speculative framework within which much research found another form of unity, as explorations of the various manifestations of the ether. See A. A. Michelson, Light Waves and Their Uses (Chicago: University of Chicago Press, 1902), 162–63. 252 staley 52. A. A. Michelson, “On the Application of Interference Methods to Astronomical Measurements,” Philosophical Magazine 30 (1890): 1–21. 53. See David DeVorkin, “Michelson and the Problem of Stellar Diameters,” Journal for the History of Astronomy 6 (1975): 1–18; A.

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