William Markowitz (February 8, 1907 in Melč,

Austrian Silesia Austrian Silesia, (historically also ''Oesterreichisch-Schlesien, Oesterreichisch Schlesien, österreichisch Schlesien''); cs, Rakouské Slezsko; pl, Śląsk Austriacki officially the Duchy of Upper and Lower Silesia, (historically ''Herzogth ...

– October 10, 1998 in Pompano Beach, Florida) was an American

astronomer An astronomer is a scientist in the field of astronomy who focuses their studies on a specific question or field outside the scope of Earth. They observe astronomical objects such as stars, planets, moons, comets and galaxies – in either ...

, principally known for his work on the standardization of

time Time is the continued sequence of existence and events that occurs in an apparently irreversible succession from the past, through the present, into the future. It is a component quantity of various measurements used to sequence events, ...

. His mother was visiting Melč near Vítkov in

(now Czech Republic) when William was born. The

Polish Polish may refer to: * Anything from or related to Poland, a country in Europe * Polish language * Poles Poles,, ; singular masculine: ''Polak'', singular feminine: ''Polka'' or Polish people, are a West Slavic nation and ethnic group, w ...

family emigrated to the

U.S. The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...

in 1910 and settled in

Chicago (''City in a Garden''); I Will , image_map = , map_caption = Interactive Map of Chicago , coordinates = , coordinates_footnotes = , subdivision_type = Country , subdivision_name ...

. William earned his doctorate from the

University of Chicago The University of Chicago (UChicago, Chicago, U of C, or UChi) is a private university, private research university in Chicago, Illinois. Its main campus is located in Chicago's Hyde Park, Chicago, Hyde Park neighborhood. The University of Chic ...

in 1931, under W.D. MacMillan. He taught at

Pennsylvania State College The Pennsylvania State University (Penn State or PSU) is a Public university, public Commonwealth System of Higher Education, state-related Land-grant university, land-grant research university with campuses and facilities throughout Pennsylvan ...

before joining the

United States Naval Observatory United States Naval Observatory (USNO) is a scientific and military facility that produces geopositioning, navigation and timekeeping data for the United States Navy and the United States Department of Defense. Established in 1830 as the Depo ...

in 1936, working under Paul Sollenberger and Gerald Clemence in the time service department. After having married Rosalyn Shulemson in 1943, Markowitz eventually became director of the department. He developed the ephemeris time scale, which had been adopted by the

IAU The International Astronomical Union (IAU; french: link=yes, Union astronomique internationale, UAI) is a nongovernmental organisation with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach ...

in 1952 on a proposal formulated by Clemence in 1948,See references (incl. citations to some of Markowitz's papers) in article Ephemeris time. as an international time standard. He subsequently worked with

Louis Essen Louis Essen FRS O.B.E. (6 September 1908 – 24 August 1997) was an English physicist whose most notable achievements were in the precise measurement of time and the determination of the speed of light. He was a critic of Albert Einstein' ...

England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...

calibrate In measurement technology and metrology, calibration is the comparison of measurement values delivered by a device under test with those of a calibration standard of known accuracy. Such a standard could be another measurement device of known ...

the newly developed

atomic clock An atomic clock is a clock that measures time by monitoring the resonant frequency of atoms. It is based on atoms having different energy levels. Electron states in an atom are associated with different energy levels, and in transitions betwe ...

s in terms of the ephemeris second. The fundamental frequency of caesium atomic clocks, which they determined as 9,192,631,770 ± 20 Hz, was used to define the second internationally since 1967. At the

International Astronomical Union The International Astronomical Union (IAU; french: link=yes, Union astronomique internationale, UAI) is a nongovernmental organisation with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreac ...

(IAU) meeting in

Dublin Dublin (; , or ) is the capital and largest city of Ireland. On a bay at the mouth of the River Liffey, it is in the province of Leinster, bordered on the south by the Dublin Mountains, a part of the Wicklow Mountains range. At the 2016 c ...

in 1955, he had proposed the system of distinguishing between variants of

Universal Time Universal Time (UT or UT1) is a time standard based on Earth's rotation. While originally it was mean solar time at 0° longitude, precise measurements of the Sun are difficult. Therefore, UT1 is computed from a measure of the Earth's angle wit ...

, as UT0 (UT as directly observed), UT1 (reduced to invariable meridian by correcting to remove effect of polar motion) and UT2 (further corrected to remove (extrapolated) seasonal variation in earth rotation rate), a system which remains in some use today. He served as President of the IAU commission on time from 1955 to 1961, and was active in the

International Union of Geodesy and Geophysics The International Union of Geodesy and Geophysics (IUGG; french: Union géodésique et géophysique internationale, UGGI) is an international non-governmental organization dedicated to the scientific study of Earth and its space environment us ...

, the

American Geophysical Union The American Geophysical Union (AGU) is a 501(c)(3) nonprofit organization of Earth, atmospheric, ocean, hydrologic, space, and planetary scientists and enthusiasts that according to their website includes 130,000 people (not members). AGU's a ...

, and the International Consultative Committee for the Definition of the Second. After retiring from USNO in 1966, Markowitz served as professor of

physics Physics is the natural science that studies matter, its fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge which r ...

Marquette University Marquette University () is a private Jesuit research university in Milwaukee, Wisconsin. Established by the Society of Jesus as Marquette College on August 28, 1881, it was founded by John Martin Henni, the first Bishop of the diocese of M ...

until 1972, and also held a post at

Nova Southeastern University Nova Southeastern University (NSU or, informally, Nova) is a private nonprofit research university with its main campus in Davie, Florida. The university consists of 14 total colleges, centers, and schools offering over 150 programs of study ...

External links

US Navy obituary
{{DEFAULTSORT:Markowitz, William American astronomers Austro-Hungarian emigrants to the United States American people of Polish descent Polish Austro-Hungarians Czech people of Polish descent People from Opava District People from Austrian Silesia 1907 births 1998 deaths