Introduction
AA Michelson was not only the first American to win a Nobel prize for science, the nature of the man behind the science was an object of some mystery – even to members of his own family. Many facets of his character were in fact brought to light by Elizabeth, a daughter of his second marriage as revealed in her book ‘The Master of Light’. This was, however, a difficult task. The character of Michelson was like an iceberg. For what appeared on the surface in his thoughts and perceptions, there were always much more by way of hidden depths.
Family Beginnings
Michelson had been born in Strzelno, Poland in December, 1852. The prevalent levels of anti semitism, however, led the family to emigrate to America through the gateway of New York. It was while staying there with relatives of his mother, Rosalie, that it was determined to travel west to link up with the prosperity of the California gold rush where all sorts of goods were in demand and his father, Samuel, anticipated opening a general store.
It was, however, no easy task to cross America from east to west before the completion of the railway system. The perilous journey that followed was to take them by steamer to the isthmus of Panama, overland to the Pacific coast through jungles and by canoe on river and then a long wait in the notorious lawless town of Porto Bello before eventually linking with a streamer to San Francisco. Eventually home was made in Murphy’s Camp some 150 miles east of San Francisco.
This ‘lively’ town with its legacy of sudden changes of fortune was home to Michleson from the time he was around four to around twelve, when in 1864 it was considered appropriate to send him to a ‘proper’ school in San Franscisco. Michleson was to spend two years at the
Lincoln Grammar School followed by some three years at what is now termed Lowell High School. Following has graduation there, efforts were eventually successful to enroll him in the Naval Academy at Annapolis as a candidate from the state of Nevada.
Naval Attachment
In 1869 the American Navy reflected some very conservative thinking. Training at sea was undertaken essentially in sailing vessels. There had been, however, the introduction of a solid core of mathematics and science within the college curriculum. It was within science – and in particular optics – that Michelson showed the most interest and aptitude. This enthusiasm, however, was to draw some criticism from his college superiors who anticipated that his country would be better served by more gunnery practice than delving into the mysteries of light. After a two year period aboard a range of ships Michelson was able to continue his naval career in December 1875 as an instructor in Physics and Chemistry at Annapolis.
It was while thus engaged in his duties that he was to meet his future first wife – Margaret Heminway – a niece of the wife of Commander Sampson with whom Michelson worked. The young couple were married in April 1877.
Michelson had been given a brief of demonstrating techniques of measurement of the speed of light as part of the college physics course. This provided an opportunity to review the techniques used so far by the eminent French scientists Foucault and Fizeau. Fizeau’s method had been to use a spinning toothed wheel and detect the extinction of light reflected from a mirror a distance of several kilometers. Foucault’s method had been to detect deflection of light by a rotating mirror. Michelson was able to design a technique which not only provided greater accuracy and but could be implemented using low cost optical components. Michelson’s modification allowed light to travel in a greater path length compared with Foucault’s method and produce a resultant greater deflection. The equivalent value of speed of light in air that Michelson determined was only about +0.2% different from the absolute values now accepted. Michelson’s experiment was probably the first such experiment ever to have been made in America.
Even today, students of science can still review the data of the 100 value observations recorded by Michelson in 1878 – as evidence of measurement technique and methodical approach to scientific observation. This clear thinking, methodical approach to science – often requiring the utmost patience and dedication – was one of the key elements which set him apart from most of his contemporaries. These measurements were also being made in an era where America was as yet very much the junior partner in science. It was Europe, with the notable inclusion of British luminaries such as Lord Raleigh and Lord Kelvin that retained the leading edge in scientific discovery and theory.
Not being established as yet within the scientific community, it was his father-in-law who provided funding for the next phase of development by way of $2,000 for improved optical equipment to make further determinations. An additional series of measurements were made during the spring of 1879 over an optical path length of around 2000 feet. An eventual revised figure of 299910 +- 50 km/s was identified – approximately +0.12% adrift from absolute values now accepted. Word was now spreading of his achievements. His parents now living in Virginia City read extracts in their local newspaper of reports of their son’s work cited in the New York Times.
The development of his skills in optical measurements, however, was becoming increasingly difficult to continue within the regimented framework of the Navy. The next phase entered upon was to be released from routine duties to provide assistance to the astronomer Professor Simon Newcomb in his separate determinations on the speed of light and where such work had attracted funding from Congress. This engaged his energies until the autumn of 1880 although the designs for the experiment did not use specific elements of his own technique. This process, however, introduced him to a wider ‘strata’ of the scientific community and would have been beneficial to managing scientific developments at the ‘human interface’ level in later work.
The Luminiferous Aether
At this time it was the view that energy such as light needed a ‘luminiferous aether’ on which to travel – much in the way that sound waves need physical atoms. This ‘luminiferous aether’ was considered as filling all space and with all physical objects – such a planets – making transit through its substance. One of the issues of deep speculation related to determining the relative speed of the earth to the ‘luminiferous aether’. Already experiments had been undertaken by famous investigators but had not detected any effects. Michelson began to speculate about how he could develop significantly better measurement techniques. There was no doubting that success in such a venture would be a pivotal achievement. Michelson resolved, however, that he needed to expand his scientific knowledge and accordingly enrolled late in 1880 at the University of Berlin where he attended the lectures in theoretical physics of Professor Herman von Helmholtz.
Thanks to a grant from Alexander Graham Bell whose interest had been aroused, Michelson was also able to make progress with a measurement system to detect the speed of the ether. Referring initially to his apparatus as an ‘interferential refractometer’ – in later years such equipment would be described by the more familiar term of ‘interferometer’.
European Interlude
It readily became apparent that the mechanical stability of the measurement system required was almost impossible to achieve within the busy city of Berlin. The developing apparatus was transported to the site of a new Astronomical observatory being constructed in Potsdam – some 25 miles from Berlin. The mechanism was so sensitive that the process of stamping on the ground some 100 metres from the apparatus would cause the interference fringes to vanish. The development of the experiment, however, was not without its cost in human terms. Michelson during this period of intense development saw very little of his wife – Margaret.
The outcome of the experiment appeared to be negative. As the apparatus was rotated, the relative movement of the fringes that Michelson could measure was around 8/100 of the distance between adjacent fringes. This was comparable to the expected difference associated with the potential movement of the ether. In practice, however, the change observed was about 1/100 of the distance between adjacent fringes. There can be no denying, however, that the process of making repeated measurements would have been a thoroughly demanding exploit. Subsequently while attending classes given by Robert Wilhelm Bunsen,at the University of Heidelberg, he became aware of the ability of elements to radiate characteristic spectra.
While in Europe, Michelson was able to spend some time in Paris – highly regarded at this time as a centre of the developing science of optics. After successfully demonstrating the fringes of his interferometer system, a former pupil of Cornu was able to indicate that the relative fringe shift expected in the ether drift experiment was not in fact 0.08 but instead 0.04 of a fringe. Being separated from Michelson at this time due to the birth of their daughter Elsa, his wife began to feel resentment at their lack of time together. Eventually, however, suitable living quarters were found for his expanded family. It was with immense relief, however, that Michelson learned in the spring of 1881 that he had received the offer of an appointment at a University in the USA – at the recently founded Case School of Applied Science in Cleveland.
The scale of the organisation at Case, however, was remarkably modest – five faculty members and a student body of seventeen. Michelson used his knowledge of the state of science in Europe at this time to order a range of specialist optical equipment items. Also, with funding from the trustees, he acquired equipment to repeat his speed of light estimations. At this time Micheson was engaged in teaching students as well as undertaking his own research. His observations in Potsdam, however, did
not feature in the lectures he conducted, though he continued to give the focus of the ether drift experiment, intense mental scrutiny.
Speed of Light: New Challenges
Michelson was soon able to continue his researching into light – and in particular in setting about making new determinations of the speed of light. His stay in Europe had allowed him to establish contacts with some of the world’s best producers of optical systems and components and funds were allocated to him to purchase a range of such equipment items. A sequence of new determinations made around 1882 established a value for the speed of light that would remain the accepted standard until Michelson made additional measurements between Mount Wilson and Mount San Antonio in California 1927.
This was a period where Michelson had a direct input to student teaching where it was noted that his lectures were ‘most elegant, absolutely clear and finished’. Although his experiments in Berlin of 1881 were not part of his lecture material, Michelson continues to speculate about changes in experimental technique that could allow a positive result in the case of the ether drift experiment.
It was the occasion of a landmark meeting of the British Association of the Advancement of Science in 1884 in Montreal that gave Michelson an occasion to learn at first hand from the like of Lord Rayleigh and Lord Kelvin about current perception on the key issues of science. Later Lord Kelvin would deliver a separate series of lectures in Baltimore that would leave a lasting impression on those who witnessed them. It was within this latter forum that Michelson would meet Morlely, a research chemist and discuss plans to try to detect changes to the speed of light of water travelling in a waveguide. Before this could be developed, however, Michelson’s health failed due to overwork and was unable to work between September and December of 1885. During this time, however, a ‘replacement’ had been found for his teaching position in the faculty at Case and the gulf between himself and his wife Margaret widened considerably although the marriage would last another thirteen years. More withdrawn as an individual, however, his means of coping with the world at large was to place even greater effort into this research work. A serious fire, however, in October of 1876, however, effectively destroyed the laboratory facilities and Michelson had to spend future months reconstructing his experiments in Morley’s laboratory. The gloom was somewhat lifted when Lord Rayleigh suggested that it was time that Michelson’s ether experiment in Potsdam was repeated. This gave impetus to Michelson and Morley to set about constructing a specialist interferometer to try to detect the ether drift effect.
The Cleveland interferometer exhibited some significant enhancements compared to the original system. The path length of light had been increased by a factor of around 10. The whole apparatus was floated on liquid mercury. Observations were undertaken of relative light fringe positions as the apparatus was rotated though 360 degrees. Key observations were made in the July of 1987 which confirmed the absence of any change of light velocity with direction of light. This was the key discovery that was to form the basis for the explosion of theory of ‘the new physics’ in years to come. Michelson was inclined to interpret the findings that the ether was moving with the earth and so no relative motion could be detected. In attempts to rationalise the findings, scientists such as George FitzGerald and Lorentz were advancing theories about how objects contracted their dimensions when in motion – i.e. the ‘FitzGerald-Lorentz contraction’.
With the key findings of the Michelson-Morley experiment consigned to history, Michelson’s new research interest became the investigation of the use of light spectra to define a standard of length. Before moving to the newly formed Clark University in Massachusetts, Michelson designed and had built a device called a ‘comparator’ which allowed the expression of a physical length as a finite number of wavelengths of light. While at Clark University, Michelson was able to make significant scientific progress with designs for interferometers to measure the diameter of astronomical objects. During 1891 he was able to make observations of the moons of Jupiter to determine their diameter using interferometer methods. It was not long, however, that disagreements at Clark University provided a springboard for most of the Professors – including Michelson – to be purloined by the University of Chicago in 1892.
Before taking up the offer at Chicago, however, previous contacts at the International Bureau of Weights and Measures in Paris materialised into a formal invitation to express the standard length of the metre in wavelengths of light. At that time the standard existed as a bar constructed of platinum, iridium and palladium and was kept in a sealed vault. The measurements took longer than expected due to the damage to key optical components which had been damaged in transit. The process involved dividing the metre length into a number of ‘etalons’ or sections and counting the number of fringes of light equivalent within an etalon. The figure produced using Cadmium light was 1553163.5.
On returning to take up his appointment at Chicago, Michelson benefited from the emergent stimulating environment – in particular in astrophysics. Michelson expressed a keen interest in the invention of the spectroheliograph by George Ellery Hale for observation of the sun’s corona. Michelson also used the more highly developed laboratory facilities to develop a machine to rule diffraction gratings using diamond cut glass. This exercise was in effect an opportunity to replicate the grating skills of Rowland which Michelson had always admired. The ultra high level of precision involved, however, proved very time consuming – with efforts lasting around ten years to perfect the techniques.
One of the key developments at this time was the construction of the Yerkes telescope with two 42 inch optical lenses. During this period, Michelson was increasingly presented with awards from academic institutions and in 1899 presented to the public the series of public Lowell Lectures on his investigation of light. Michelson also successfully demonstrated his echelon spectroscope at the Paris Exposition of 1900. Also, Michelson was a key member in founding of the American Physical Society in 1899.
It was around this period of increasing recognition, however, that the long strained relationship with his wife Margaret, finally came adrift. Evidence of the final division appeared when early in 1897 Michelson left home and took up residence in a hotel. Divorce proceedings were presented in court in early 1898. The court sided against Michelson on being presented with accounts of Michelson’s apparent cruelty. Wheels turn, however, in most situations and the friendship with a certain Edna Stanton blossomed into marriage in December of 1899. A new young family emerged, with three girls – Madeline, Beatrice and Dorothy providing plenty of distractions for the eminent Michelson. There were, for example, trips to the his laboratories on Saturday mornings For the two older children, it was the custom to give them half hour violin lessons each morning before he departed for the laboratory.
Nobel Prize
Here is no doubt, however, that the greatest recognition was to come with the award of the Nobel prize for Physics in 1907. Prizes for physics had previously been awarded to Rontgen, Lorentz, Zeeman, Becquerel, the Curies, Rayleigh, Lenard and JJ Thompson. The Nobel committee, however, were unanimous in their verdict in making the award to Michelson out of recognition of the broad range of significant developments he had pioneered.
It was while in the role of visiting professor at the University Gottingen in Germany that Michelson became aware of how divided European scientists were concerning the ‘new’ physics of quantum theory and the ‘old’ physics of light traveling in an ether. It was very much apparent, however, that it had been the experimental genius of Michelson that had prompted Einstein to develop his theories.
With America joining the First World war in April 1917, Michelson re-established his Navy links and in June of 1918 reported to Washington to the Bureau of Ordinance. Michelson provided key technical and scientific input into development of a range of optically based systems – including a rangefinder, specialist binoculars for detecting submarines. Also, with sources of high quality German glass not available, Michelson provided key information to help America manufacture high quality glass for submarine periscopes.
Star Gazing
Subsequently Michelson was to spend more time in California – at the Mount Wilson Observatory. Previous system to measure the size of stars using interferometer techniques had been revised and Michelson’s team was able to measure the size of Betelgeuse in Orion. This indicated that this star was in fact 2300 times larger than the sun at a distance of 150 light years. In its day this measurement captured the public imagination to a surprising extent.
Additional measurements of the speed of light were undertaken in California on Mount Wilson over a distance of around 35 kilometres. This required the design of new optical structures and use a very powerful arc lamp. Based on the specific measurement configuration, the condition of correct resonance took place at a specific frequency of revolution of the revolving mirror when the light path returned to the same location as at zero deflection. A value of 299,820 km per second was obtained though it was determined that greater control of the air flow was required to improve accuracy levels.
An additional experiment was carried out in Chicago to determine if the velocity of light is affected by the rotation of the earth. Observations indicated that it was not affected. At this time, however, Michelson was recovering from a prostrate operation and it took him several months to recover better health.
Final Measurements
Considerations of effects due to turbulence of the air mass in these experiments prompted Michelson to plan an experiment within a mile long evacuated tube – with light being reflected several times form the mirror systems. An experimental installation was set up at the Irvine Ranch near Pasadena with extensive establishment funding. Due to recurrent illness, Michelson was not able to spend as much time as he would have liked to solve some nagging technical issues relating to the findings – where fluctuations of up to 12 miles per second were being observed. His last visit to the site was to be in March 1931. This also co-incided with a visit of Einstein to his hotel. Spurred on by news of Michelson’s failing health, the investigators at the Irvine Ranch work flat out to establish definitive measurements which they announced to him as 299,774 km/sec on the 7th of May. Michelson started to dictate the text of a report of the experiment but the effort exhausted him and he fell into a deep peaceful sleep. He died on the morning of the 9th of May, 1931. In fact the measurements made at Mount Wilson were closer to the accepted value of the speed of light.
Epitaph
Some of the essential perspective on AA Michelson has been provided by his daughter Dorothy who was around 30 when he died.
Some of the essential perspective on AA Michelson has been provided by his daughter Dorothy who was around 30 when he died. There can be no doubt that Michelson gave his best endeavours in the call of science and especially in development of scientific instrumentation and the science of associated measurement. He was able to develop superb instrumentation systems and provide huge support and knowledge in the expansion the scientific might of America.
Through the studies of his scientific work and the accounts of peers and colleagues which are documented, a picture emerges of an admirable individual fascinated by the lure of science and her secrets and in which the mystery of the nature and properties of light held absolute fascination.
