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Encyclopedia > Louis Essen

Louis Essen (September 6, 1908August 24, 1997) was an English physicist whose most notable achievements were in the precise measurement of time and the determination of the speed of light. September 6 is the 249th day of the year (250th in leap years). ... 1908 (MCMVIII) was a leap year starting on Wednesday (link will take you to calendar). ... August 24 is the 236th day of the year in the Gregorian Calendar (237th in leap years), with 129 days remaining. ... 1997 (MCMXCVII) was a common year starting on Wednesday of the Gregorian calendar. ... Motto: (French for God and my right) Anthem: God Save the King/Queen Capital London (de facto) Largest city London Official language(s) English (de facto) Unification    - by Athelstan AD 927  Area    - Total 130,395 km² (1st in UK)   50,346 sq mi  Population    - 2006 est. ... ... In the fields of science, engineering, industry and statistics, accuracy is the degree of conformity of a measured or calculated quantity to its actual (true) value. ... A pocket watch, a device used to keep time There are two distinct views on the meaning of time. ... The speed of light in a vacuum is an important physical constant denoted by the letter c for constant or the Latin word celeritas meaning swiftness. It is the speed of all electromagnetic radiation in a vacuum, not just visible light. ...

Louis Essen (left center) with Udo Adelsberger (extreme left); the other two persons sitting at the table are unidentified.
Louis Essen (left center) with Udo Adelsberger (extreme left); the other two persons sitting at the table are unidentified.

Contents

Image File history File links Download high-resolution version (1006x547, 62 KB) Summary from left to right: de:Quarzuhr-Entwickler de:Udo Adelsberger, de:Pysikalische-Technische Bundesanstalt; Entwickler der präzisionsarbeitenden Quartzuhr en:Louis Essen, en:National Physical Laboratory, UK; Japaner © Dr. Klaus Adelsberger, de:Neckargemünd; BGKS Kulms, Editor... Image File history File links Download high-resolution version (1006x547, 62 KB) Summary from left to right: de:Quarzuhr-Entwickler de:Udo Adelsberger, de:Pysikalische-Technische Bundesanstalt; Entwickler der präzisionsarbeitenden Quartzuhr en:Louis Essen, en:National Physical Laboratory, UK; Japaner © Dr. Klaus Adelsberger, de:Neckargemünd; BGKS Kulms, Editor...

Early work

Born in Nottingham, Essen earned his degree in physics from the University of London in 1928, having studied at University College Nottingham. He started work at the National Physical Laboratory (NPL) the following year, under D.W. Dye, investigating the potential of tuning forks and quartz crystal oscillators for precise time measurement. His research led to his development of the quartz ring clock in 1938, the clock soon becoming a standard for time measurement at observatories throughout the world. For other uses, see Nottingham (disambiguation). ... Physics (Greek: (phúsis), nature and (phusiké), knowledge of nature) is the science concerned with the discovery and understanding of the fundamental laws which govern matter, energy, space, and time and explaining them using mathematics. ... The University of London is a university based primarily in London. ... Year 1928 (MCMXXVIII) was a leap year starting on Sunday (link will display full calendar). ... The University of Nottingham is a leading research and teaching university in the city of Nottingham, in the East Midlands of England. ... The National Physical Laboratory (NPL) is the national measurement standards laboratory for the United Kingdom, based at Bushy Park in Teddington, near London. ... A tuning fork is a simple metal two-pronged fork with the tines formed from a U-shaped bar of elastic material (usually steel). ... Quartz is one of the most common minerals in the Earths continental crust. ... A crystal oscillator is an electronic circuit that uses the mechanical resonance of a vibrating crystal of piezoelectric material to create an electrical signal with a very precise frequency. ... Year 1938 (MCMXXXVIII) was a common year starting on Saturday (link will take you to calendar). ... Molėtai Astronomical Observatory An observatory is a location used for observing terrestrial and/or celestial events. ...


The speed of light

During World War II, Essen worked on radar and developed a number of instruments, including the cavity resonance wavemeter. It was this work that suggested to Essen the possibility of a more precise measurement of the speed of light. In 1946, in collaboration with A.C. Gordon-Smith, he used a microwave cavity, of precisely known dimensions, and exploited his expertise in time-measurement to establish the frequency for a variety of its normal modes. As the wavelength of the modes was known from the geometry of the cavity and from electromagnetic theory, knowledge of the associated frequencies enabled a calculation of the speed of light. Their result, 299,792±3 km/s, was substantially greater than the prevailing sequence of optical measurements that had begun around the start of the 20th century and Essen had to withstand some fierce criticism and disbelief. Even NPL director Sir Charles Galton Darwin, while supporting the work, observed that Essen would get the correct result once he had perfected the technique. Moreover, W.W. Hansen at Stanford University had used a similar technique and obtained a measurement which was more consistent with the conventional (optical) wisdom. However, a combination of Essen's stubbornness, his iconoclasm and his belief in his own skill at measurement (and a little help with calculations from Alan Turing) inspired him to refine his apparatus and to repeat his measurement in 1950, establishing a result of 299,792.5±1 km/s, . This was the value adopted by the 12th General Assembly of the Radio-Scientific Union in 1957. Most subsequent measurements have been consistent with this value. In 1983, the 17th Conférence Générale des Poids et Mesures adopted the standard value, 299,792.458 km/s for the speed of light. Combatants Allied powers: China France Great Britain Soviet Union United States and others Axis powers: Germany Italy Japan and others Commanders Chiang Kai-shek Charles de Gaulle Winston Churchill Joseph Stalin Franklin Roosevelt Adolf Hitler Benito Mussolini Hideki Tōjō Casualties Military dead: 17,000,000 Civilian dead: 33,000... This long range Radar antenna, known as ALTAIR, is used to detect and track space objects in conjunction with ABM testing at the Ronald Reagan Test Site on the Kwajalein atoll[1]. Radar is a system that uses radio waves to determine and map the location, direction, and/or speed... It has been suggested that this article or section be merged into resonator. ... The speed of light in a vacuum is an important physical constant denoted by the letter c for constant or the Latin word celeritas meaning swiftness. It is the speed of all electromagnetic radiation in a vacuum, not just visible light. ... 1946 (MCMXLVI) was a common year starting on Tuesday. ... Sine waves of various frequencies; the bottom waves have higher frequencies than those above. ... Various normal modes in a 1D-lattice. ... The wavelength is the distance between repeating units of a wave pattern. ... Maxwells equations are the set of four equations, attributed to James Clerk Maxwell, that describe the behavior of both the electric and magnetic fields, as well as their interactions with matter. ... km redirects here. ... Look up second in Wiktionary, the free dictionary. ... (19th century - 20th century - 21st century - more centuries) Decades: 1900s 1910s 1920s 1930s 1940s 1950s 1960s 1970s 1980s 1990s As a means of recording the passage of time, the 20th century was that century which lasted from 1901–2000 in the sense of the Gregorian calendar (1900–1999... Sir Charles Galton Darwin. ... William Webster Hansen (May 27, 1909 - May 23, 1949) was a US physicist who was one of the founders of the technology of microwave electronics. ... The Leland Stanford Junior University, commonly known as Stanford University (or simply Stanford), is a private university located approximately 37 miles (60 kilometers) southeast of San Francisco and approximately 20 miles northwest of San José in an unincorporated area of Santa Clara County. ... Alan Mathison Turing, OBE (June 23, 1912 – June 7, 1954), was an English mathematician, logician, and cryptographer. ... 1950 (MCML) was a common year starting on Sunday (link will take you to calendar). ... km redirects here. ... Look up second in Wiktionary, the free dictionary. ... The International Union of Radio Science (in French, LUnion radio-scientifique internationale - URSI) is one of 26 international scientific unions affiliated to the International Council for Science. ... 1957 (MCMLVII) was a common year starting on Tuesday of the Gregorian calendar. ... 1983 (MCMLXXXIII) was a common year starting on Saturday of the Gregorian calendar. ... The General Conference on Weights and Measures is the English name of the Conférence générale des poids et mesures (CGPM, sometimes written in English Conférence Générale des Poids et Mesures). ... km redirects here. ... Look up second in Wiktionary, the free dictionary. ...


Atomic clocks

Essen earned his Ph.D. (1941) and D.Sc. (1948) from the University of London before becoming interested in the possibility of using the frequency of atomic spectra to improve time measurement. The feasibility of measuring time using caesium as an atomic reference had been demonstrated by the US National Bureau of Standards. In 1955, he developed,[1] in collaboration with Jack Parry, the first practical atomic clock by integrating the caesium atomic standard with conventional quartz crystal oscillators to allow calibration of existing time-keeping. For the movie, see 1941 (film). ... Year 1948 (MCMXLVIII) was a leap year starting on Thursday (the link is to a full 1948 calendar). ... The University of London is a university based primarily in London. ... Electromagnetic spectroscopy a. ... General Name, Symbol, Number caesium, Cs, 55 Chemical series alkali metals Group, Period, Block 1, 6, s Appearance silvery gold Atomic mass 132. ... As a non-regulatory agency of the United States Department of Commerce’s Technology Administration, the National Institute of Standards (NIST) develops and promotes measurement, standards, and technology to enhance productivity, facilitate trade, and improve the quality of life. ... 1955 (MCMLV) was a common year starting on Saturday of the Gregorian calendar. ... Atomic clock Chip-Scale Atomic Clock Unveiled by NIST An atomic clock is a type of clock that uses an atomic resonance frequency standard to feed its counter. ...


Time standards

This work led Essen to champion the caesium spectrum as an international time standard. The ammonia molecule had already been proposed as such but Essen was convinced that caesium would prove more stable. However, the International Astronomical Union meeting in Dublin in 1955 had adopted the ephemeris time, developed by Simon Newcomb in the 19th century in terms of the Earth’s motion round the sun. The ephemeris second became a standard in 1960 but in 1967, at the 13th Conférence Générale des Poids et Mesures, the second was redefined in terms of the spectrum of caesium that had been precisely measured by Essen in collaboration William Markowitz of the United States Naval Observatory. Standardization, in the context related to technologies and industries, is the process of establishing a technical standard among competing entities in a market, where this will bring benefits without hurting competition. ... Ammonia is a compound with the formula NH3. ... In chemistry, a molecule is an aggregate of two or more atoms in a definite arrangement held together by chemical bonds [1] [2] [3] [4] [5]. Chemical substances are not infinitely divisible into smaller fractions of the same substance: a molecule is generally considered the smallest particle of a pure... Logo of the IAU The International Astronomical Union (French: Union astronomique internationale) unites national astronomical societies from around the world. ... WGS-84 (GPS) Coordinates: 53. ... 1955 (MCMLV) was a common year starting on Saturday of the Gregorian calendar. ... Ephemeris Time (ET) is a now obsolete time scale used in ephemerides of celestial bodies, in particular the Sun (as observed from the Earth), Moon, planets, and other members of the solar system. ... Simon Newcomb. ... Alternative meaning: Nineteenth Century (periodical) (18th century — 19th century — 20th century — more centuries) As a means of recording the passage of time, the 19th century was that century which lasted from 1801-1900 in the sense of the Gregorian calendar. ... 1960 (MCMLX) was a leap year starting on Friday (the link is to a full 1960 calendar). ... 1967 (MCMLXVII) was a common year starting on Sunday of the Gregorian calendar (the link is to a full 1967 calendar). ... The General Conference on Weights and Measures is the English name of the Conférence générale des poids et mesures (CGPM, sometimes written in English Conférence Générale des Poids et Mesures). ... Look up second in Wiktionary, the free dictionary. ... William Markowitz (February 8, 1907 - October 10, 1998) was a Polish-American astronomer, principally known for his work on the standardization of time. ... Aerial view of USNO. The United States Naval Observatory (USNO) is one of the oldest scientific agencies in the United States. ...


Later life

Essen spent all his working life at the National Physical Laboratory.


In 1971 he published The Special Theory of Relativity: A Critical Analysis[2] in which he questioned Einstein's theory, which apparently was not appreciated by his employers. As Essen later stated (1978) [3]: Albert Einstein ( ) (March 14, 1879 – April 18, 1955) was a German-born theoretical physicist who is widely considered to have been one of the greatest physicists of all time. ...


No one has attempted to refute my arguments, but I was warned that if I persisted I was likely to spoil my career prospects.


He retired in 1972 and died in Great Bookham, Surrey. 1972 (MCMLXXII) was a leap year starting on Saturday. ... Statistics Population: About 10,000 Ordnance Survey OS grid reference: TQ1354 Administration District: Mole Valley D.C. Shire county: Surrey Region: South East England Constituent country: England Sovereign state: United Kingdom Other Ceremonial county: Surrey Historic county: Surrey Services Police force: Surrey Police Ambulance service: South East Coast Post office... Not to be confused with Surry. ...


Honours

Russian Academy of Sciences (Росси́йская Акаде́мия Нау́к) is the national academy of Russia. ... Year 1959 (MCMLIX) was a common year starting on Thursday of the Gregorian calendar. ... Commanders Badge of the Order of the British Empire (Military division) The Most Excellent Order of the British Empire is a British order of chivalry established on 4 June 1917 by King George V. The Order includes five classes in civil and military divisions; in decreasing order of seniority... The premises of the Royal Society in London (first four properties only). ... 1960 (MCMLX) was a leap year starting on Friday (the link is to a full 1960 calendar). ... The Institute of Electrical and Electronics Engineers or IEEE (pronounced as eye-triple-ee) is an international non-profit, professional organization incorporated in the State of New York, United States. ... 1987 (MCMLXXXVII) was a common year starting on Thursday of the Gregorian calendar. ...

References

  1. ^ Essen, L., and Perry, J. V. (1955), "An atomic standard of frequency and time keeping", Nature 176, p. 280.
  2. ^ Essen, L. (1971) The Special Theory of Relativity: A Critical Analysis, Oxford University Press (Oxford science research papers, 5). , booklet in which he questioned the modern interpretation of the special theory of relativity.
  3. ^ Essen, L. (1978) "Relativity and Time Signals", Electronics and Wireless World, Oct. 1978, p. 14; compare also: Essen, L. (1988) "Relativity - Joke or Swindle?", Electronics and Wireless World 94, 126 - 127.

External links

  • "Time Lord" Louis Essen
  • Sciencemuseum: Louis Essen and atomic clocks

  Results from FactBites:
 
Louis Essen - Wikipedia, the free encyclopedia (873 words)
Louis Essen (September 6, 1908 – August 24, 1997) was an English physicist whose most notable achievements were in the precise measurement of time and the determination of the speed of light.
As the wavelength of the modes was known from the geometry of the cavity and from electromagnetic theory, knowledge of the associated frequencies enabled a calculation of the speed of light.
However, a combination of Essen's stubornness, his iconoclasm and his belief in his own skill at measurement (and a little help with calculations from Alan Turing) inspired him to refine his apparatus and to repeat his measurement in 1950, establishing a result of 299,792.5±1 km/s,.
  More results at FactBites »

 
 

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