View source for Albert A. Michelson

{{Short description|American experimental physicist (1852–1931)}}
{{Use mdy dates|date=October 2025}}
{{Infobox scientist
| name              = Albert Michelson
| image             = Albert Abraham Michelson2.jpg
| caption           = Michelson in 1907
| birth_name        = Albert Abraham Michelson
| birth_date        = {{Birth date|1852|12|19|mf=yes}}
| birth_place       = [[Strelno]], [[Province of Posen]], [[Kingdom of Prussia]]
| death_date        = {{Death date and age|1931|05|09|1852|12|19|mf=yes}}
| death_place       = [[Pasadena, California]], US
| nationality       = American
| alma_mater        = {{Plain list|
* [[US Naval Academy]]
* [[University of Berlin]]
* [[École polytechnique]]
}}
| known_for         = [[Michelson–Morley experiment]]
| spouses           = {{Plain list|
* {{Marriage|Margaret Hemingway|1877|1898|reason=divorced}}
* {{Marriage|Edna Stanton|1899}}
}}
| children          = 6 (3 with Margaret, 3 with Edna)
| relatives         = {{Plain list|
* [[Miriam Michelson]] (sister)
* [[Harriet Lane Levy]] (cousin)
}}
| awards            = {{Plain list|
* [[Rumford Prize]] (1888)
* [[Matteucci Medal]] (1903)
* [[Copley Medal]] (1907)
* [[Nobel Prize in Physics]] (1907)
* [[Elliott Cresson Medal]] (1912)
* [[Henry Draper Medal]] (1916)
* [[Prix Jules Janssen]] (1922)
* [[Gold Medal of the Royal Astronomical Society|RAS Gold Medal]] (1923)
* [[Franklin Medal]] (1923)
* [[Albert Medal (Royal Society of Arts)|RSA Albert Medal]] (1920)
* [[Duddell Medal and Prize]] (1929)
}}
| fields            = [[Optics]]
| work_institutions = {{Plain list|
* [[Case School of Applied Science]] (1883–89)
* [[Clark University]] (1889–92)
* {{Nowrap|[[University of Chicago]] (1892–?)}}
}}
| academic_advisors = {{Plain list|
* [[Marie Alfred Cornu]]<ref name=PhysicsTree>{{Cite web|title=Albert Abraham Michelson - Physics Tree|url=https://academictree.org/physics/peopleinfo.php?pid=237|website=academictree.org|access-date=July 14, 2025}}</ref>
* [[Hermann von Helmholtz]]<ref name=PhysicsTree/>
}}
| notable_students  = {{Plain list|
* [[Henry Gale (astrophysicist)|Henry G. Gale]]<ref name=PhysicsTree/>
* [[Frank B. Jewett]]<ref name=PhysicsTree/>
}}
| module={{Infobox military person|embed= yes
| allegiance         = {{Flagu|United States|1863|size=20px}}
| branch_label       = Branch
| branch             = {{Tree list}}
* [[United States Navy]]
** [[United States Navy Reserve|Navy Reserve]]<ref name=":0" />
{{Tree list/end}}
| serviceyears_label = Years of service
| serviceyears       = 1873–1881; 1918–1921<ref name=":0" />
| rank               = [[Commander (United States)|Commander]]
}}
| signature   = Albert A Michelson Signature.svg
}}

'''Albert Abraham Michelson''' (December 19, 1852 – May 9, 1931) was an American [[experimental physicist]] known for his work on measuring the [[speed of light]] and especially for the [[Michelson–Morley experiment]]. In 1907, he received the [[Nobel Prize in Physics]], becoming the first American to win the Nobel Prize in a science. He was the founder and the first head of the physics departments of the [[Case School of Applied Science]] and the [[University of Chicago]].<ref>{{Cite web|url=https://www.lib.uchicago.edu/projects/centcat/fac/facch07_01.html|title=Albert A. Michelson, Physics|website=www.lib.uchicago.edu|access-date=August 2, 2019|archive-url=https://web.archive.org/web/20171021102316/https://www.lib.uchicago.edu/projects/centcat/fac/facch07_01.html|archive-date=October 21, 2017|url-status=dead}}</ref><ref>{{Cite web|url=https://www.lib.uchicago.edu/e/scrc/findingaids/view.php?eadid=ICU.SPCL.MICHELSON|title=Guide to the Albert A. Michelson Papers 1891–1969|website=www.lib.uchicago.edu|access-date=August 2, 2019|archive-url=https://web.archive.org/web/20190907014105/https://www.lib.uchicago.edu/e/scrc/findingaids/view.php?eadid=ICU.SPCL.MICHELSON|archive-date=September 7, 2019|url-status=dead}}</ref><ref>{{Cite web|url=https://history.aip.org/phn/11706001.html|title=Michelson, Albert A. (Albert Abraham), 1852-1931|website=history.aip.org|access-date=August 2, 2019|archive-url=https://web.archive.org/web/20190322211127/https://history.aip.org/phn/11706001.html|archive-date=March 22, 2019|url-status=dead}}</ref>

== Biography ==
=== Early life ===
Albert Abraham Michelson was born on December 19, 1852, in Strelno (now [[Strzelno]], Poland), then located in the [[Kingdom of Prussia]], into a [[Polish-Jewish]] family.<ref>National Academy of Sciences, Washington, DC, 1938, Vol. XIX) quotes (on p. 128) Michelson's sister, the novelist Miriam Michelson, as having written of her parents in a letter to Millikan that "both Albert Michelson's father and mother were born of Jewish parents&nbsp;..."</ref><ref>{{cite web|url=https://www.aip.org/history/exhibits/gap/Michelson/Michelson.html|title=Albert Abraham Michelson 1852–1931|publisher=American Institute of Physics|access-date=January 27, 2016|archive-date=February 3, 2016|archive-url=https://web.archive.org/web/20160203232123/https://www.aip.org/history/exhibits/gap/Michelson/Michelson.html|url-status=dead}}</ref><ref>{{Cite web |url=https://www.aps.org/units/fip/newsletters/200805/michelson.cfm |title=APS Physics &#124; FIP &#124; Albert Abraham Michelson: "A Pole - well up in Arithmetic" |access-date=September 21, 2019 |archive-url=https://web.archive.org/web/20190921165432/https://www.aps.org/units/fip/newsletters/200805/michelson.cfm |archive-date=September 21, 2019 |url-status=dead }}</ref> He moved to the [[United States]] with his parents in 1855, at the age of 2. He grew up in the mining towns of [[Murphys, California|Murphy's Camp]], California, and [[Virginia City, Nevada]], where his father was a merchant. His family was non-religious, and Michelson himself was a lifelong [[agnostic]].<ref>{{cite book|title=Bulletin de la Société des sciences et des lettres de Łódź: Série, Recherches sur les déformations, Volumes 39–42|date=2003|publisher=Société des sciences et des lettres de Łódź|page=162|quote=Michelson's biographers stress, that our hero was not conspicuous by religiousness. His father was a free-thinker and Michelson grew up in non-religious family and have no opportunity to acknowledge the belief of his forebears. He was agnostic through his whole life and only for the short period he was a member of the 21st lodge in Washington.}}</ref><ref>{{cite book|title=The Book of Nothing: Vacuums, Voids, and the Latest Ideas About the Origins of the Universe|date=2002|publisher=Random House Digital, Inc.|isbn=978-0-375-72609-5|author=[[John D. Barrow]]|page=[https://archive.org/details/indextocriticism00glor/page/136 136]|quote=Morley was deeply religious. His original training had been in theology and he only turned to chemistry, a self-taught hobby, when he was unable to enter the ministry. Michelson, by contrast, was a religious agnostic.|url=https://archive.org/details/indextocriticism00glor/page/136}}</ref><ref>{{cite book|title=The Master of Light: A Biography of Albert A. Michelson|publisher=University of Chicago Press|first=Dorothy Michelson |last=Livingston|page=106|quote=On the religious question, Michelson disagreed with both these men. He had renounced any belief that moral issues were at stake in ...}}</ref> He spent his high school years in San Francisco in the home of his aunt, Henriette Levy (née Michelson), who was the mother of author [[Harriet Lane Levy]].<ref name="Levy-47">Levy, ''920 O'Farrell Street'', 47.</ref>
His sister was the novelist [[Miriam Michelson]].

=== Education and career ===
President [[Ulysses S. Grant]] awarded Michelson a special appointment to the [[U.S. Naval Academy]] in 1869.<ref>[http://www.usna.edu/LibExhibits/collections/michelson/ Nimitz Library's Virtual Exhibits – LibExhibits]</ref> During his four years as a [[midshipman]] at the Academy, he excelled in [[optics]], heat, [[climatology]] and [[technical drawing]]. After graduating in 1873 and two years at sea, he returned to the Naval Academy in 1875 to become an instructor in physics and chemistry until 1879, when he was posted to the Nautical Almanac Office, Washington (part of the [[United States Naval Observatory]])<ref>{{cite journal|title=Nineteenth century astronomy at the U.S. Naval Academy | journal=Journal of Astronomical History and Heritage| volume=5| issue=2| pages=165| bibcode=2002JAHH....5..165S| last1=Shankland| first1=Paul D.| last2=Orchiston| first2=Wayne| year=2002| doi=10.3724/SP.J.1440-2807.2002.02.07| s2cid=110077408| url=https://researchonline.jcu.edu.au/4957/1/4957_Shankland%26Orchiston_2002.pdf}}</ref><ref>{{cite web |url=http://www.usno.navy.mil/USNO/about-us/usno-command-history |title=USNO – Our Command History |publisher=[[United States Naval Observatory|U.S. Naval Observatory]] |access-date=June 2, 2011 |archive-date=June 6, 2011 |archive-url=https://web.archive.org/web/20110606230351/http://www.usno.navy.mil/USNO/about-us/usno-command-history/ |url-status=dead }}</ref><ref>{{cite journal |first1=Paul D. |last1=Shankland |first2=Wayne |last2=Orchiston |title=Nineteenth century astronomy at the U.S. Naval Academy |url=http://researchonline.jcu.edu.au/4957/1/4957_Shankland%26Orchiston_2002.pdf |journal=Journal of Astronomical History and Heritage |volume=5 |issue=2 |pages=165–179 |date=2002 |doi=10.3724/SP.J.1440-2807.2002.02.07 |bibcode=2002JAHH....5..165S |s2cid=110077408 |access-date=November 26, 2017 |archive-url=https://web.archive.org/web/20170808141904/https://researchonline.jcu.edu.au/4957/1/4957_Shankland%26Orchiston_2002.pdf |archive-date=August 8, 2017 |url-status=dead }}</ref> to work with [[Simon Newcomb]]. The following year, he took a leave of absence to continue his studies in Europe; he visited the universities of [[University of Berlin|Berlin]] and [[University of Heidelberg|Heidelberg]] in Germany, and the [[Collège de France]] and [[École polytechnique]] in Paris, France.

Michelson was fascinated with the sciences, in particular the problem of measuring the [[speed of light]]. While in [[Annapolis]], he conducted his first experiments on the speed of light as part of a class demonstration in 1877. His Annapolis experiment was refined, and in 1879,<ref>In 1879 a letter from James Clerk Maxwell to the astronomer [[David Peck Todd]] came to the attention of Michelson, possibly giving him considerable motivation. See the book {{cite book|author=Schwinger, J.|author-link=Julian Schwinger|title=Einstein's Legacy|year=1986|publisher=Scientific American Library}} [https://books.google.com/books/about/Einstein_s_Legacy.html?id=7EvCAgAAQBAJ 2012 e-book].</ref> he measured the speed of light in air to be {{val|299,864|51}} kilometres per second, and estimated the speed of light in vacuum as {{val|299,940|u=km/s}}, or {{val|186,380|u=mi/s}}.<ref>{{cite web|url=http://www.raman-scattering.eu/raman/texts/009_menu_vitesse.php|title=raman-scattering.eu|access-date=June 2, 2011|archive-url=https://web.archive.org/web/20120324223604/http://www.raman-scattering.eu/raman/texts/009_menu_vitesse.php|archive-date=March 24, 2012|url-status=dead}}{{failed verification|date=January 2016}}</ref><ref>{{cite journal|url=http://www.opticsinfobase.org/on/abstract.cfm?uri=on-4-4-14|title=Optics at the U.S. Naval Academy|journal=Optics News|year=1978|volume=4|issue=4|page=14|publisher=Optical Society of America|doi=10.1364/ON.4.4.000014|url-access=subscription}}</ref><ref>{{cite web|url=http://sas.uwaterloo.ca/~rwoldfor/papers/sci-method/paperrev/node6.html|title=Michelson's 1879 determinations of the speed of light|publisher=Department of Statistics and Actuarial Science, University of Waterloo (Canada)}}</ref> After two years of studies in Europe, he resigned from the [[United States Navy|Navy]] in 1881. In 1883, he was appointed Professor of Physics at the [[Case Western Reserve University|Case School of Applied Science]] in [[Cleveland]], Ohio, and concentrated on developing an improved [[interferometer]]. In 1887, he and [[Edward Morley]] carried out the famous [[Michelson–Morley experiment]], which failed to detect evidence of the existence of the [[luminiferous ether]]. He later moved on to use [[astronomical interferometer]]s in the measurement of stellar diameters and in measuring the separations of binary stars.

In 1889, Michelson became a professor at [[Clark University]] at [[Worcester, Massachusetts|Worcester]], [[Massachusetts]], and in 1892 was appointed Professor and the first head of the Department of Physics at the newly organized [[University of Chicago]]. In 1902, he was elected a Member of the [[American Philosophical Society]].<ref>{{Cite web|title=APS Member History|url=https://search.amphilsoc.org/memhist/search?year=1902;smode=advanced;startDoc=1|access-date=May 19, 2021|website=search.amphilsoc.org}}</ref>

In 1907, Michelson had the honor of being the first American to receive the [[Nobel Prize in Physics]] "for his optical precision instruments and the spectroscopic and metrological investigations carried out with their aid".  He also won the [[Copley Medal]] in 1907, the [[Henry Draper Medal]] in 1916, and the [[Gold Medal of the Royal Astronomical Society]] in 1923.  A [[Impact crater|crater]] on the [[Moon]] is named after him.{{citation needed|date=September 2022}}

He returned to military service in the closing months of [[World War I|World War One]] as a [[Lieutenant commander (United States)|Lieutenant Commander]] in the [[United States Navy Reserve|Naval Reserve]], serving in the [[Bureau of Ordnance]]. He was promoted to [[Commander (United States)|Commander]] in the reserve in May 1919 and was recalled briefly to active duty in the [[9th Naval District]] before being released from service on September 30, 1921.<ref name=":0">{{Cite web |title=Michelson |url=https://www.history.navy.mil/research/histories/ship-histories/danfs/m/michelson.html |url-status=live |archive-url=https://web.archive.org/web/20210725001445/https://www.history.navy.mil/research/histories/ship-histories/danfs/m/michelson.html |archive-date=July 25, 2021 |access-date=August 17, 2022 |website=www.history.navy.mil |language=en-US}}</ref>

=== Death and honors ===
Michelson died on May 9, 1931, in [[Pasadena, California]], at the age of 78.<ref>In November 1929, at the French Academy of Sciences, Michelson's death was erroneously announced, see http://cnum.cnam.fr/CGI/fpage.cgi?4KY28.118/97/100/598/5/588 and http://cnum.cnam.fr/CGI/fpage.cgi?4KY28.118/183/100/598/5/588</ref> The University of Chicago Residence Halls remembered Michelson and his achievements by dedicating 'Michelson House' in his honor. Case Western Reserve has dedicated a Michelson House to him, and Michelson Hall (an academic building of science classrooms, laboratories and offices) at the [[United States Naval Academy]] also bears his name. Michelson Laboratory at [[Naval Air Weapons Station China Lake]] in Ridgecrest, California, is named for him. There is a display in the publicly accessible area of the Lab which includes facsimiles of Michelson's Nobel Prize medal, the prize document, and examples of his diffraction gratings. In 2017, a newly renovated physics research center at the University of Chicago was renamed in honor of Michelson as well.<ref>{{cite web |title=UChicago names building after pioneering physicist Albert Michelson |url=https://news.uchicago.edu/story/uchicago-names-building-after-pioneering-physicist-albert-michelsonhttps://news.uchicago.edu/story/uchicago-names-building-after-pioneering-physicist-albert-michelson |website=UChicago News |publisher=University of Chicago |access-date=January 22, 2021 }}{{Dead link|date=January 2021 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>

Numerous awards, lectures, and honors have been created in Albert A. Michelson's name.<ref>{{cite web|url=https://www.usna.edu/Library/sca/ve-collections/michelson/remembered.php|title=Michelson Remembered|publisher=Nimitz Library, US Naval Academy|access-date=October 22, 2017|archive-url=https://web.archive.org/web/20171022085706/https://www.usna.edu/Library/sca/ve-collections/michelson/remembered.php|archive-date=October 22, 2017|url-status=dead}}</ref> Some of the current awards and lectures named for Michelson include the following: the Bomem-Michelson Award and Lecture annually presented until 2017 by the Coblentz Society;<ref>{{cite web |title=The ABB Sponsored Bomem-Michelson Award |url=http://www.coblentz.org/awards/the-bomem-michelson-award |publisher=[[Coblentz Society]] |date=2017 |access-date=October 22, 2017 |archive-url=https://web.archive.org/web/20171023010420/http://www.coblentz.org/awards/the-bomem-michelson-award |archive-date=October 23, 2017 |url-status=dead }}</ref> the [[Michelson–Morley Award]] and Lecture, along with the Michelson Lecture Series,<ref>{{cite web |title=Michelson Lectures |url=http://www.phys.cwru.edu/events/michelson.php |publisher=[[Case Western Reserve University]] |date=2017 |access-date=October 22, 2017 |archive-url=https://web.archive.org/web/20170513172116/http://www.phys.cwru.edu/events/michelson.php |archive-date=May 13, 2017 |url-status=dead }}</ref> and the Michelson Postdoctoral Prize Lectureship,<ref>{{cite web |title=Michelson Postdoctoral Prize Lectureship |url=http://www.phys.cwru.edu/events/mppl.php |publisher=Case Western Reserve University |date=2017 |access-date=October 22, 2017 |archive-url=https://web.archive.org/web/20170513172115/http://www.phys.cwru.edu/events/mppl.php |archive-date=May 13, 2017 |url-status=dead }}</ref> all of which are given annually by [[Case Western Reserve University]]; the A.A. Michelson Award presented every year by the [[Computer Measurement Group]];<ref>{{cite web |title=Awards & Scholarships: AA Michelson Award Winners |url=https://www.cmg.org/about-cmg/awards-scholarships/ |publisher=[[Computer Measurement Group]] |date=2017 |access-date=October 22, 2017 |archive-url=https://web.archive.org/web/20171022141509/https://www.cmg.org/about-cmg/awards-scholarships/ |archive-date=October 22, 2017 |url-status=dead  }}</ref> the Albert A. Michelson Award given by the [[Navy League of the United States]];<ref>{{cite web |title=Albert A. Michelson Award |url=https://navyleague.org/programs/michelson-award.html |publisher=[[Navy League of the United States]] |date=2016 |access-date=December 25, 2018 |archive-url=https://web.archive.org/web/20181019001541/https://navyleague.org/programs/michelson-award.html |archive-date=October 19, 2018 |url-status=dead  }}</ref> and the Michelson Memorial Lecture Series<ref>{{cite web |title=Michelson Memorial Lecture Series |url=https://www.usna.edu/MathSci/michelson-lecture.php |publisher=[[United States Naval Academy|U.S. Naval Academy]] |date=2017 |access-date=October 22, 2017 |archive-url=https://web.archive.org/web/20171022141933/https://www.usna.edu/MathSci/michelson-lecture.php |archive-date=October 22, 2017 |url-status=dead }}</ref> presented annually by the Division of Mathematics and Science at the [[United States Naval Academy|U.S. Naval Academy]].

== Speed of light ==
{{more citations needed section|date=May 2017}}
[[File:Michelson - Experimental Determination of the Speed of Light, p 1.jpg|thumb|210px|Page one of Michelson's ''Experimental Determination of the Velocity of Light'']]
[[File:Michelson - Experimental Determination of the Speed of Light, conclusion.jpg|thumb|210px|Concluding page of Michelson's ''Experimental Determination of the Velocity of Light'']]

=== Early measurements ===
Michelson was fascinated by light all his life.  Once asked why he studied light, he reputedly said, "because it's so much fun".<ref>{{cite web|title=The Master of Light|url=https://www.theattic.space/home-page-blogs/2019/12/13/the-master-of-light|website=The Attic|access-date=January 7, 2020|archive-url=https://web.archive.org/web/20200202073206/https://www.theattic.space/home-page-blogs/2019/12/13/the-master-of-light|archive-date=February 2, 2020|url-status=dead}}</ref>

As early as 1869, while serving as an officer in the [[United States Navy]], Michelson started planning a repeat of the rotating-mirror method of [[Léon Foucault]] for measuring the speed of light, using improved optics and a longer baseline. He conducted some preliminary measurements using largely improvised equipment in 1878, about the same time that his work came to the attention of [[Simon Newcomb]], director of the Nautical Almanac Office who was already advanced in planning his own study.

Michelson's formal experiments took place in June and July 1879. He constructed a frame building along the north sea wall of the Naval Academy to house the machinery.<ref>Michelson, Albert A. "[https://www.gutenberg.org/files/11753/11753-h/11753-h.htm Experimental Determination of the Velocity of Light Made at the U.S. Naval Academy, Annapolis]".</ref> Michelson published his result of 299,910&nbsp;±&nbsp;50&nbsp;km/s in 1879 before joining [[Simon Newcomb|Newcomb]] in Washington DC to assist with his measurements there. Thus began a long professional collaboration and friendship between the two.

[[Simon Newcomb]], with his more adequately funded project, obtained a value of 299,860&nbsp;±&nbsp;30&nbsp;km/s, just at the extreme edge of consistency with Michelson's. Michelson continued to "refine" his method and in 1883 published a measurement of 299,853&nbsp;±&nbsp;60&nbsp;km/s, rather closer to that of his mentor.

[[File:Albert Abraham Michelson 1918.jpg|thumb|230px|[[Lieutenant commander (United States)|Lt. Cmdr.]] Albert A. Michelson while serving in the [[U.S. Navy]]. He rejoined the U.S. Navy in World War I,<ref name="Nobel">{{cite web |title=Albert A. Michelson – Biographical |url=https://www.nobelprize.org/prizes/physics/1907/michelson/biographical/ |url-status=live |archive-url=https://web.archive.org/web/20211222043500/https://www.nobelprize.org/prizes/physics/1907/michelson/biographical/ |archive-date=December 22, 2021 |access-date=July 9, 2022}}</ref> when this portrait was taken.]]

=== Mount Wilson and Lookout Mountain ===
In 1906, a novel electrical method was used by [[Edward Bennett Rosa|E. B. Rosa]] and the [[National Bureau of Standards]] to obtain a value for the [[speed of light]] of 299,781&nbsp;±&nbsp;10&nbsp;km/s. Though this result has subsequently been shown to be severely biased by the poor electrical standards in use at the time, it seems to have set a fashion for rather lower measured values.

From 1920, Michelson started planning a definitive measurement from the [[Mount Wilson Observatory]], using a baseline to [[Lookout Mountain (Los Angeles County, California)|Lookout Mountain]], a prominent bump on the south ridge of [[Mount San Antonio]] ("Old Baldy"), some 22 miles distant.

In 1922, the [[United States Coast and Geodetic Survey]] began two years of painstaking measurement of the baseline using the recently available [[invar]] tapes. With the baseline length established in 1924, measurements were carried out over the next two years to obtain the published value of 299,796&nbsp;±&nbsp;4&nbsp;km/s.<ref>
{{cite journal
  | url = http://www.pvaa.us/nightwatch/GeodeticMeasurementOfUnusuallyHighAccuracy.pdf
  | last = Garner  | first = C. L.
  | title = A Geodetic Measurement of Unusually High Accuracy
  | journal = Coast and Geodetic Survey Journal
  | date = April 1949
  | pages = 68–74
  | access-date = August 13, 2009
| archive-url = https://web.archive.org/web/20090325034419/http://www.pvaa.us/nightwatch/GeodeticMeasurementOfUnusuallyHighAccuracy.pdf
  | archive-date = March 25, 2009
| url-status = dead
}}</ref>

Famous as the measurement is, it was beset by problems, not least of which was the haze created by the smoke from forest fires which blurred the mirror image. It is also probable that the intensively detailed work of the [[geodetic survey]], with an estimated error of less than one part in 1 million, was compromised by a shift in the baseline arising from the [[1925 Santa Barbara earthquake|Santa Barbara earthquake]] of June 29, 1925, which was an estimated magnitude of 6.3 on the [[Richter magnitude scale|Richter scale]].

The now-famous [[Michelson–Morley experiment]] also influenced the affirmation attempts of peer [[Albert Einstein]]'s theory of [[general relativity]] and [[special relativity]], using similar optical instrumentation. These instruments and related collaborations included the participation of fellow physicists [[Dayton Miller]], [[Hendrik Lorentz]], and [[Robert S. Shankland|Robert Shankland]].
[[File:1921 Albert Abraham Michelson.jpg|thumb|[[Autochrome Lumière|Autochrome]] portrait by [[The Archives of the Planet|Auguste Léon]], 1921]]

=== Michelson, Pease, and Pearson ===
The period after 1927 marked the advent of new measurements of the speed of light using novel [[electro-optics|electro-optic]] devices, all substantially lower than Michelson's 1926 value.

Michelson sought another measurement, but this time in an evacuated tube to avoid difficulties in interpreting the image owing to atmospheric effects. In 1929, he began a collaboration with [[Francis G. Pease]] and Fred Pearson to perform a measurement in a 1.6&nbsp;km tube 3 feet in diameter at the Irvine Ranch near Santa Ana, California.<ref>{{cite journal |title=Michelson's Last Experiment |journal=[[Science (journal)|Science]] |date=May 22, 1931 |volume=73 |issue=1899 |pages=10–14 |doi=10.1126/science.73.1899.10|pmid=17843974 }}</ref><ref name="1935 paper" /> In multiple reflections the light path was increased to 5 miles. For the first time in history the speed of light was measured in an almost perfect vacuum of 0.5&nbsp;mm of mercury. Michelson died with only 36 of the 233 measurement series completed and the experiment was subsequently beset by geological instability and condensation problems before the result of {{val|299,774|11|u=km/s}}, consistent with the prevailing [[electro-optics|electro-optic]] values, was published posthumously in 1935.<ref name="1935 paper">{{cite journal |url=http://adsbit.harvard.edu/full/1935CMWCI.522....1M |title=Measurement of the velocity of light in a partial vacuum |journal=Contributions from the Mount Wilson Observatory |date=1935 |volume=522 |pages=100–1 |last1=Michelson |first1=A. A. |last2=Pease |first2=F. G. |last3=Pearson |first3=F. |issue=2091 |doi=10.1126/science.81.2091.100-a |pmid=17816642 |bibcode=1935Sci....81..100M |s2cid=28035563 |via=[[Astrophysics Data System]]|url-access=subscription }}</ref>

=== Application of basic statistical principles in Michelson's study of speed of light ===
During June and early July 1879, Michelson refined experimental arrangements from those developed by [[Hippolyte Fizeau]] and [[Léon Foucault]]. The experimental setup was as follows: Light generated from a source is directed towards a rotating mirror through a slit on a fixed plate; the rotating mirror reflects the incoming light and at a certain angle, towards the direction where another fixed flat mirror is placed whose surface is perpendicular to the incoming ray of light; the rotating mirror should have rotated by an angle&nbsp;''α'' by the time the ray of light travels back and is reflected again towards the fixed plate (the distance between the fixed mirror and the rotating one is recorded as&nbsp;''D''); a displacement from the slit is detected on the plate which measures&nbsp;''d''; the distance from the rotating mirror to the fixed plate is designated as the radius ''r'' while the number of revolutions per second of the mirror is recorded as ''ω''. In this way, {{nowrap|1=tan(2''α'') = ''d''/''r''}}; {{nowrap|1=Δ''t'' = (''α''/2{{pi}})/''ω''}}; speed of light can be derived as&nbsp;{{nowrap|1=''c'' = 2''D''/Δ''t''}}.

While at plain sight, four measured quantities are involved: distance ''D'', radius ''r'', displacement ''d'' and rotating mirror revolution per second&nbsp;''ω'', which seems simple; yet based on the limitation of the measurement technology at that time, great efforts were made by Michelson to reduce [[Observational error|systematic errors]] and apply subsequent corrections. For instance, he adopted a steel measuring tape with a said length of 100 feet and he intended to measure tens of times across the distance; still, he measured its length against a copy of the official standard yard to find out it as 100.006 feet, thus eliminating a systematic error, albeit small.

Aside from the efforts to reduce as much as possible the systematic errors, repeated measurements were performed at multiple levels to obtain more accurate results. As R.J.&nbsp;MacKay and R.W.&nbsp;Oldford remarked in their article,<ref>{{Cite journal|last1=Oldford|first1=R. W.|last2=MacKay|first2=R. J.|date=August 2000|title=Light|journal=Statistical Science|volume=15|issue=3|pages=254–278|doi=10.1214/ss/1009212817|issn=0883-4237|doi-access=free}}</ref> 'It is clear that Michelson appreciated the power of averaging to reduce variability in measurement', it is clear that Michelson had in mind the property that averages vary less which should be formally described as: the standard deviation of the average of ''n'' independent random variables is less than that of a single random variable by a factor of the square root of&nbsp;''n''. To realize that, he also strived to have each measurement not influencing each other, thus being mutually [[independent random variables]].

A [[statistical model]] for repeated measurements with the assumption of independence or identical distributions is unrealistic. In the case of light speed study, each measurement is approached as the sum of quantity of interest and measurement error. In the absence of systematic error, the measurement error of speed of light can be modeled by a random sample from a distribution with unknown expectation and finite variance; thus, the speed of light is represented by the expectation of the model distribution and the ultimate goal is to estimate the expectation of the model distribution on the acquired dataset. The law of large numbers suggests to estimate the expectation by the sample mean.<ref>{{Cite book|title=A Modern Introduction to Probability and Statistics: Understanding Why and How|year=2005|isbn=978-1852338961|pages=248|last1=Dekking|first1=F. M.|last2=Kraaikamp|first2=C.|last3=Lopuhaä|first3=H. P.|last4=Meester|first4=L. E.|publisher=Springer }}</ref>

=== Michelson–Morley experiment ===
{{main|Michelson–Morley experiment}}

In 1887, he collaborated with colleague [[Edward Morley|Edward Williams Morley]] of Western Reserve University, now part of [[Case Western Reserve University]], in the [[Michelson–Morley experiment]]. Their experiment for the expected motion of the [[Earth]] relative to the [[luminiferous aether|aether]], the hypothetical medium in which light was supposed to travel, resulted in a [[null result]]. Surprised, Michelson repeated the experiment with greater and greater precision over the next years, but continued to find no ability to measure the aether. The Michelson–Morley results were immensely influential in the physics community, leading [[Hendrik Lorentz]] to devise his now-famous [[Lorentz contraction]] equations as a means of explaining the null result.

There has been some historical controversy over whether [[Albert Einstein]] was aware of the Michelson–Morley results when he developed his theory of [[special relativity]], which pronounced the aether to be "superfluous". In a later interview, Einstein said of the Michelson–Morley experiment, "I was not conscious it had influenced me directly&nbsp;... I guess I just took it for granted that it was true."<ref>Swenson, Loyd S. Jr., ''The Ethereal Aether: A History of the Michelson–Morley–Miller Aether-Drift Experiments, 1880–1930'', University of Texas Press, 1972</ref>  Regardless of Einstein's specific knowledge, the experiment is today considered the canonical experiment in regards to showing the lack of a detectable aether.<ref>Note that while Einstein's 1905 paper ''[[On the Electrodynamics of Moving Bodies]]'' appears to reference the experiment on first glance—"together with the unsuccessful attempts to discover any motion of the earth relatively to the 'light medium', suggest that the phenomena of electrodynamics as well as of mechanics possess no properties corresponding to the idea of absolute rest"—it has been shown that Einstein was referring to a different category of experiments here.</ref><ref>[[Gerald Holton|Holton, Gerald]], "Einstein, Michelson, and the 'Crucial' Experiment", ''Isis'', Vol. 60, No. 2 (Summer, 1969), pp. 133–197 {{doi|10.1086/350468}}</ref>

The precision of their equipment allowed Michelson and Morley to be the first to get precise values  for the [[fine structure]] in the atomic spectral lines<ref>AA.  Michelson  and  E.  W.  Morley,  Amer. J.  Sci.34,  427  (1887);  Phil  Mag.  24,  463 (1887).</ref> for which in 1916 [[Arnold Sommerfeld]] gave a theoretical explanation, introducing the [[fine-structure constant]].

== Astronomical interferometry ==
=== Optical ===
[[Image:Hooker interferometer.jpg|right|thumb|300px|The horizontal structure mounted at the top of the [[Hooker Telescope]] implements Michelson's stellar interferometer (1920). Mirrors on that stage (not visible in picture) redirect starlight from two smaller apertures up to 20 feet (6m) apart into the telescope.]]
In 1920 Michelson and [[Francis G. Pease]] made the first measurement of the diameter of a star other than the Sun. Michelson had invented [[astronomical interferometry]] and built such an instrument at the [[Mount Wilson Observatory]] which was used to measure the diameter of the [[red giant]] [[Betelgeuse]]. A periscope arrangement was used to direct light from two subpupils, separated by up to 20 feet (6m), into the main pupil of the 100 inch (2.5m) [[Hooker Telescope]], producing interference fringes observed through the eyepiece. The measurement of stellar diameters and the separations of binary stars took up an increasing amount of Michelson's life after this.

Beginning in the 1970s, astronomical interferometry was revived, with the configurations using two (or more) separate apertures (with diameters small compared to their separation) being often referred to as "Michelson Stellar Interferometry". This was to distinguish it from [[speckle interferometry]], but should not be confused with the [[Michelson interferometer]] which is one common ''laboratory'' interferometer configuration of which the interferometer used in the Michelson–Morley experiment was an instance. Michelson's concept of interfering light from two relatively small apertures separated by a substantial distance (but with that distance, or ''baseline'', now often as long as hundreds of meters) is employed at [[List of astronomical interferometers at visible and infrared wavelengths|modern operational observatories]] such as [[VLTI#Interferometry and the VLTI|VLTI]], [[CHARA array|CHARA]] and the U.S. Navy's [[Navy Prototype Optical Interferometer|NPOI]].

=== Gravitational wave ===
[[Gravitational waves]] are detected using a Michelson interferometer with a laser light source. In 2020 there were three Michelson interferometer gravitational wave detectors operational, and a fourth under construction. These Michelson interferometers have arms 4 kilometers in length, set at 90 degree angles to each other, with the light passing through 1&nbsp;m diameter vacuum tubes running their entire length. A passing gravitational wave will slightly stretch one arm as it shortens the other. This is precisely the motion to which these Michelson interferometers are most sensitive. As of 2020 fifteen [[List of gravitational wave observations#List of gravitational wave events|gravitational wave events]] had been observed using these Michelson interferometers.

== Harmonic analyzer ==
{{main|Ball-and-disk integrator#Invention and early use}}
In the 1890s Michelson built a mechanical device called the harmonic analyzer, for computing coefficients of [[Fourier series]] and drawing graphs of their partial sums. He and [[Samuel Wesley Stratton|S.&nbsp;W.&nbsp;Stratton]] published a paper about this machine in the ''[[American Journal of Science]]'' in 1898.<ref>{{cite journal|first1=Albert A.|last1= Michelson|first2= Samuel W.|last2= Stratton|author-link2=Samuel Wesley Stratton|title= A New Harmonic Analyzer|journal=[[American Journal of Science]]|year=1898|volume= 5|issue= 25|page= 1|doi= 10.2475/ajs.s4-5.25.1|bibcode= 1898AmJS....5....1M}}</ref><ref>{{cite book|first1= Bill|last1= Hammack|author-link=William S. Hammack|
first2= Steve|last2= Krantz|author-link2=Steven G. Krantz|first3= Bruce |last3=Carpenter|title=Albert Michelson's Harmonic Analyzer|publisher= Blurb|year= 2014|isbn= 978-0983966166}}</ref>

== Family ==
In 1877, Michelson married Margaret Hemingway, daughter of a wealthy New York stockbroker and lawyer and the niece of his commander [[William T. Sampson]]. They had two sons and a daughter.<ref>James, I. (2009). Driven to Innovate: A Century of Jewish Mathematicians and Physicists p. 101. {{ISBN|978-1-906165-22-2}}. "In 1877, he married Margaret Hemingway, daughter of a wealthy New York stockbroker and lawyer. This marriage lasted twenty years and produced two sons and a daughter."</ref><ref name=ANB>{{Cite ANB |title=Michelson, Albert Abraham |id=1301131 |first=Marten |last=den Boer}}</ref>

In 1899, Michelson married Edna Stanton. They raised three daughters.<ref name=ANB/>

He is a great uncle of physicist [[Peter Michelson]].<ref>{{cite web |url=https://web.stanford.edu/~peterm/links.htm |title=Links}}</ref>

== Michelson in popular culture ==
[[File:Strzelno tablica pamiatkowa Albert A Michelson 2017 03 27 054.jpg|thumb|150px|"Albert Abraham Michelson was born in this city on December 19, 1852. He was a professor at the University of Chicago, a Nobel laureate, who, with his famous experiments on the speed of light, started a new era in the development of physics. This plaque, for the commemoration of the great physicist was founded by Polish Physical Society." A commemorative plaque in [[Strzelno]], Poland, installed by the [[Polish Physical Society]].]]
In Season 3 Episode 26 of the television series ''[[Bonanza]]'' ("Look to the Stars", broadcast March 18, 1962), Ben Cartwright ([[Lorne Greene]]) helps the 16-year-old Michelson (portrayed by 25-year-old Douglas Lambert (1936–1986)) obtain an appointment to the [[U.S. Naval Academy]], despite the opposition of the bigoted town schoolteacher (played by [[William Schallert]]).  ''Bonanza'' was set in and around [[Virginia City, Nevada]], where Michelson lived with his parents prior to leaving for the Naval Academy.  In a voice-over at the end of the episode, Greene mentions Michelson's 1907 Nobel Prize.

The home in which Michelson lived as a child in [[Murphys, California|Murphys Camp, California]], was in the store of his father, first on Main Street, across from the Sperry & Perry Hotel, and after the 1859 fire in a store next to the hotel. His aunt Bertha Meyers owned a house on Main Street toward the east end of town and Michelson probably visited her family there frequently.

New Beast Theater Works in collaboration with High Concept Laboratories produced a 'semi-opera' about Michelson, his obsessive working style and its effect on his family life. The production ran from February 11 to 26, 2011, in Chicago at The Building Stage. Michelson was portrayed by [[Jon Stutzman]]. The play was directed by [[David Maral]] with music composed by [[Joshua Dumas]].{{citation needed|date=October 2014}}

[[Norman Fitzroy Maclean]] wrote an essay "Billiards Is a Good Game"; published in ''The Norman Maclean Reader'' (ed. O. Alan Weltzien, 2008), it is an appreciation of Michelson from Maclean's vantage point as a graduate student regularly watching him play billiards.<ref>{{cite web |url=https://mag.uchicago.edu/science-medicine/billiards-good-game |title=Billiards is a good game |last=Maclean |first=Norman F. |date=Summer 1975 |publisher=The University of Chicago Magazine |access-date=August 16, 2018 |archive-url=https://web.archive.org/web/20180817092237/https://mag.uchicago.edu/science-medicine/billiards-good-game |archive-date=August 17, 2018 |url-status=dead }}</ref>

== Awards ==
[[File:Michaelson experiment annapolis.JPG|thumb|230px|A monument at [[United States Naval Academy]] marks the path of Michelson's experiments measuring the speed of light.]]

* 1888 – [[Rumford Prize]]
* 1903 – [[Matteucci Medal]]<ref>{{Cite web |title=Medals |url=https://www.accademiaxl.it/en/activities/medals/ |access-date=August 10, 2025 |website=Accademia delle Scienze detta dei XL |at=Matteucci Medal. Elenco Premiati |language=it}}</ref>
* 1907 – [[Copley Medal]]
* 1907 – [[Nobel Prize in Physics]]<ref name=Nobel/>
* 1912 – [[Elliott Cresson Medal]]
* 1916 – [[Henry Draper Medal]] from the [[United States National Academy of Sciences|National Academy of Sciences]]<ref name=Draper>{{cite web|title=Henry Draper Medal |url=http://www.nasonline.org/about-nas/awards/henry-draper-medal.html |publisher=National Academy of Sciences |access-date=February 19, 2011 |url-status=dead |archive-url=https://web.archive.org/web/20130126003930/http://www.nasonline.org/about-nas/awards/henry-draper-medal.html |archive-date=January 26, 2013 }}</ref>
* 1920 – [[Albert Medal (Royal Society of Arts)|Albert Medal]]
* 1922 – [[Prix Jules Janssen]], the highest award of the [[Société astronomique de France]], the French astronomical society.
* 1922 – Honorary Member of the [[Optica (society)|Optical Society of America]]<ref>{{Cite web |title=Albert Michelson {{!}} Optica |url=https://www.optica.org/history/biographies/bios/albert-michelson/ |access-date=September 13, 2024 |website=www.optica.org}}</ref>
* 1923 – [[Gold Medal of the Royal Astronomical Society]]
* 1923 – [[The Franklin Institute Awards|Franklin Medal]]
* 1929 – [[Duddell Medal and Prize]]

Michelson was a member of the [[Royal Society]], the [[National Academy of Sciences]], the [[American Physical Society]],  and the [[American Association for the Advancement of Science]].

The [[Computer Measurement Group]] gives an annual [[Computer Measurement Group#Awards|A. A. Michelson Award]].

== See also ==
{{Portal|Biography}}

* [[List of Jewish Nobel laureates]]
* [[List of United States Naval Academy alumni#Nobel laureates|List of Naval Academy Nobel Laureates]]
* [[List of Poles#Physics|List of Poles]]

== Biography ==
* [[Bernard Jaffe|Jaffe, Bernard]] (1960) ''Michelson and the Speed of Light'', Doubleday. New York

== Notes ==
{{reflist}}

== References ==
* {{cite book | last=Livingston | first=D. M. | title=The Master of Light: A Biography of Albert A. Michelson | date=1973 | publisher=University of Chicago Press | isbn=978-0-226-48711-3 | url-access=registration | url=https://archive.org/details/masteroflightbio0000livi }}
* {{cite book | last=Levy | first=Harriet Lane | author-link=Harriet Lane Levy | title=920 O'Farrell Street | publisher=Heyday Books | date=1996 | location=Berkeley | isbn=978-0-930588-91-5 | url=https://archive.org/details/920ofarrellstree00levy_0 }}

== Works ==
* {{Cite book|title=Light waves and their uses|volume=|publisher=University Press |location=Chicago|year=1907|language=en|url=https://gutenberg.beic.it/webclient/DeliveryManager?pid=11000649}}
* ''[https://libserv.aip.org/ipac20/ipac.jsp?session=166914R337JA5.559738&menu=search&aspect=subtab232&npp=10&ipp=20&spp=20&profile=rev-all&ri=9&source=%7E%21horizon&index=.GW&term=D%C3%A9termination+exp%C3%A9rimentale+de+la+valeur+du+m%C3%A8tre+en+longueurs+d%27ondes+lumineuses&x=18&y=6&aspect=subtab232 Détermination expérimentale de la valeur du mètre en longueurs d'ondes lumineuses]''. Paris : Gauthier-Villars et fils, 1894. (French translation of ''Experimental Determination of the Velocity of Light'')
<gallery>
File:Michelson, Albert Abraham – Light waves and their uses, 1907 – BEIC 11000649.jpg|''Light waves and their uses'' (1907)
File:Michelson-1.jpg|French translation of ''Experimental Determination of the Velocity of Light'' (1894)
</gallery>

== External links ==
{{Sister project links||wikt=no|n=no|s=|b=no|v=no|voy=no}}
* [https://www.youtube.com/watch?v=RnSG_EjMRUo Three Glimpses of Albert Abraham Michelson at the Peak of His Career] This video includes audio of Michelson speaking.
* [https://www.nasonline.org/wp-content/uploads/2024/06/michelson-a-a.pdf National Academy of Sciences Biographical Memoir]
* [https://history.aip.org/exhibits/gap/Michelson/Michelson.html Michelson's Life and Works from the American Institute of Physics] {{Webarchive|url=https://web.archive.org/web/20120716182659/http://www.aip.org/history/gap/Michelson/Michelson.html |date=July 16, 2012 }}
* [http://www.usna.edu/LibExhibits/collections/michelson/navy.html U.S. Naval Academy and The Navy]
* [http://www.usna.com/Document.Doc?id=617 From USNA to Nobel: Albert A. Michelson's Life and Contributions]{{dead link|date=January 2018 |bot=InternetArchiveBot |fix-attempted=yes }}
* [https://web.archive.org/web/20050904233217/http://michelson-house.uchicago.edu/ Michelson House at the University of Chicago]
* {{Nobelprize}} including the Nobel Lecture, December 12, 1907 ''Recent Advances in Spectroscopy''
* {{gutenberg author|id=4093|name=Albert A. Michelson}}
* {{Internet Archive author |sname=Albert Abraham Michelson}}
* [https://www.imdb.com/title/tt0529603/ IMDB: Bonanza episode ''Look to the Stars'']
* [http://www.laphamsquarterly.org/voices-in-time/norman-maclean-learns-from-the-master.php?page=all Norman Maclean: ''"Billiards Is a Good Game": Gamesmanship and America's First Nobel Prize Scientist''; reprinted in Lapham's Quarterly]
* [http://www.europa.com/~telscope/usna.doc The U.S. Naval Academy Observatory Programs and Times Gone By: A Tale of Two Domes]
* {{cite web|url=http://www.navair.navy.mil/nawcwd/nawcwd/news/2008/2008-02_michelson.htm|title=NAWS China Lake|access-date=September 3, 2010|archive-date=September 22, 2008|archive-url=https://web.archive.org/web/20080922110020/http://www.navair.navy.mil/nawcwd/nawcwd/news/2008/2008-02_michelson.htm|url-status=dead}}
* [http://eprints.jcu.edu.au/4957/1/4957_Shankland%26Orchiston_2002.pdf Nineteenth Century Astronomy at the U.S. Naval Academy]

=== Archival collections ===
* [https://www.lib.uchicago.edu/e/scrc/findingaids/view.php?eadid=ICU.SPCL.MICHELSON Guide to the Albert A. Michelson Papers 1891–1969] {{Webarchive|url=https://web.archive.org/web/20190907014105/https://www.lib.uchicago.edu/e/scrc/findingaids/view.php?eadid=ICU.SPCL.MICHELSON |date=September 7, 2019 }} at the [https://www.lib.uchicago.edu/scrc/ University of Chicago Special Collections Research Center]
* [https://www.usna.edu/Library/sca/man-findingaids/MS_347.EAD.xml USNA Guide to the Albert A. Michelson Collection, 1803–1989]
* [https://libserv.aip.org/ipac20/ipac.jsp?session=168A4841MD511.411803&limitbox_1=LO01+%3D+icos&menu=search&aspect=power&npp=10&ipp=20&spp=20&profile=rev-icos&ri=13&source=%7E%21horizon&index=.GW&term=WILLIAM+P.+JESSE+STUDENT+NOTEBOOKS%2C+1919-1921&x=16&y=13&aspect=power William Polk Jesse student notebooks, 1919–1921, Niels Bohr Library & Archives] (contains notes on the lectures of Albert A. Michelson, including courses taught by Michelson: Mechanics and Wave Motion, Electricity and Magnetism, and Physical Optics)

{{Copley Medallists 1901–1950}}
{{Nobel Prize in Physics Laureates 1901–1925}}
{{1907 Nobel Prize winners}}
{{NAS presidents}}
{{Presidents of the American Physical Society}}
{{Presidents of the American Association for the Advancement of Science}}
{{Hall of Fame for Great Americans}}
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