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https://www.cambridge.org/core MicroscopyPioneers Pioneers in : Albert A. Michelson Eric Clark

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25 Sep 2021 at 22:23:46 Albert A. Michelson in his penchant for research. In 1887, he conducted a series of (1852–1931) experiments with Edward W. Morley to detect the existence The renowned Albert of ether, a hypothetical all-pervasive medium that many sci- Abraham Michelson was awarded entists believed extended throughout the . Michel- the in in 1907. son developed an interferometer, a device that uses

He spent a significant amount of interference to measure the differences in velocity of two , subject to the Cambridge Core terms of use, available at his life trying to improve upon ear- light beams. The interferometer, using mirrors, splits a beam lier scientific research and is often of light in two, sending them along perpendicular paths, and credited with the statement “The then brings them back together again. By analyzing any result- grand underlying principles have ing interference fringes due to miniscule mismatches in the been firmly established … further beams, very delicate measurements of differences in velocity truths of physics are to be looked of light can be made. Michelson intended to use the interfer- for in the sixth place of decimals.” ometer to measure the velocity of the Earth against the ether. Michelson is most widely remem- If the Earth were traveling through a medium, then the bered for his experiments in which of light traveling in the same direction as the Earth would be he proved that the hypothetical different than light traveling perpendicular to the direction of medium of light, known as “ether,” did not exist, as well as his the Earth. In what may be the most famous null result ever many attempts to accurately measure the . obtained, Michelson and Morley found no interference fringes Although Michelson was born in Strzelno, Prussia (now and, therefore, no evidence of ether.

Poland), on December 19, 1852, his family moved to the Michelson accepted a professorship at Clark University in https://www.cambridge.org/core/terms when he was only 3 years old. Landing in New 1890 but left only a few years later to teach physics and become York, the Michelson clan soon traveled westward, eventually the first department head at the newly built University of Chi- settling in San Francisco, California, where the elder Michel- cago. When World I began, Michelson volunteered for son became a successful merchant. At the age of 17, Albert military duty even though he was 65 years old and once again Michelson entered the United States Naval Academy and became a member of the United States Navy. Returning to excelled in his studies of the , although he was a less Chicago in 1918, he redirected his studies toward the field of than admirable sailor. Graduating in 1873, he began teaching astronomy. Although Armand Fizeau was the first to suggest at the Naval Academy in 1875 and remained in the that interferometry could be used to measure the size of stars, position for four years. Michelson was the first to actually use an interferometer to

. During the period of his military employment, Michelson measure the size of a stellar body. In 1920, he used a six-meter https://doi.org/10.1017/S1551929519001007 started work on what would be a driving in his life, the interferometer attached to a 254-centimeter telescope to suc- precise measurement of the speed of light. However, Michelson cessfully measure the diameter of Betelgeuse (Alpha Orionis) realized that he would need to know more about optics in order at 386,160,000 kilometers. to be able to improve on the values previously obtained by oth- Michelson died on May 9, 1931, but his research laid the ers. He traveled to Europe with the intention to study the field groundwork for further discoveries in the twentieth cen- and retired from the Navy in 1881. When he returned to North tury in the areas of the properties of light, exploration, America, he established the most accurate value of the velocity and atomic . In , in a tribute to Michelson published of light available at that , 299,853 kilometers per second. after his death, praised him justly: “Myhonored ­ The measurement remained the best for almost an entire gen- Dr. Michelson, it was you who led the into new paths, eration before he made it even more precise. and through your marvelous experimental work paved the way In 1883, Michelson became a physics at the Case for the development of the .” School of Applied Science in Cleveland, Ohio, but continued

2019 November • www.microscopy-today.com doi:10.1017/S1551929519001007 47