Edward Linfoot
Encyclopedia
Edward Hubert Linfoot was a British mathematician
Mathematician
A mathematician is a person whose primary area of study is the field of mathematics. Mathematicians are concerned with quantity, structure, space, and change....

, primarily known for his work on optics
Optics
Optics is the branch of physics which involves the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behavior of visible, ultraviolet, and infrared light...

, but also noted for his work in pure mathematics.

Early life and career

Edward Linfoot was born in Sheffield
Sheffield
Sheffield is a city and metropolitan borough of South Yorkshire, England. Its name derives from the River Sheaf, which runs through the city. Historically a part of the West Riding of Yorkshire, and with some of its southern suburbs annexed from Derbyshire, the city has grown from its largely...

, England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...

, in 1905. He was the eldest child of George Edward Linfoot, a violinist and mathematician, and George's wife Laura, née Clayton. After attending King Edward VII School he won a scholarship to Balliol College at the University of Oxford
University of Oxford
The University of Oxford is a university located in Oxford, United Kingdom. It is the second-oldest surviving university in the world and the oldest in the English-speaking world. Although its exact date of foundation is unclear, there is evidence of teaching as far back as 1096...

.

During his time at Oxford he met the number theorist
Number theory
Number theory is a branch of pure mathematics devoted primarily to the study of the integers. Number theorists study prime numbers as well...

 G. H. Hardy
G. H. Hardy
Godfrey Harold “G. H.” Hardy FRS was a prominent English mathematician, known for his achievements in number theory and mathematical analysis....

, and after graduating in 1926, Linfoot completed a D.Phil under the supervision of Hardy with a thesis entitled Applications Of The Theory Of Functions Of A Complex Variable.

After brief stints at the University of Göttingen, Princeton University
Princeton University
Princeton University is a private research university located in Princeton, New Jersey, United States. The school is one of the eight universities of the Ivy League, and is one of the nine Colonial Colleges founded before the American Revolution....

, and Balliol College, Linfoot took a job in 1932 as assistant lecturer, and later lecturer, at the University of Bristol
University of Bristol
The University of Bristol is a public research university located in Bristol, United Kingdom. One of the so-called "red brick" universities, it received its Royal Charter in 1909, although its predecessor institution, University College, Bristol, had been in existence since 1876.The University is...

. During the 1930s Linfoot's interests slowly made the transition from pure mathematics to the application of mathematics to the study of optics, but not before proving an important result in number theory with Hans Heilbronn
Hans Heilbronn
Hans Arnold Heilbronn was a mathematician.He was born into a German-Jewish family. He was a student at the universities of Berlin, Freiburg and Göttingen, where he met Edmund Landau, who supervised his doctorate...

, that there are at most ten imaginary quadratic number fields with class number 1.

Shift to optics

The exact reasons that Linfoot chose to switch his research from pure mathematics to optics are complex and there is probably no single most important reason. John Bell has highlighted the role played by Linfoot's political awareness, in particular his relationship with Heilbronn who had been forced to flee Nazi Germany
Nazi Germany
Nazi Germany , also known as the Third Reich , but officially called German Reich from 1933 to 1943 and Greater German Reich from 26 June 1943 onward, is the name commonly used to refer to the state of Germany from 1933 to 1945, when it was a totalitarian dictatorship ruled by...

. Suspecting a second world war was imminent, and knowing his delicate constitution would not make it through military physical examinations, Linfoot decided to contribute to the future war with scientific advancements in the field of optics. Other contributing factors to this change in focus were his lifelong fondness for astronomy and, by Linfoot's own testimony, a feeling that he had reached the limits of his pure mathematical creativity.

This shift was facilitated by Dr C. R. Burch of the H. H. Wills Physics Laboratory in Bristol who led the University's optics group. Burch was a physical thinker but recognised the benefits of strong mathematical ability in understanding physics, and so encouraged Linfoot in his transition. Linfoot availed himself of the laboratory's facilities to first construct his own telescope and later to apply the theory of aspheric lens
Aspheric lens
An aspheric lens or asphere is a lens whose surface profiles are not portions of a sphere or cylinder. In photography, a lens assembly that includes an aspheric element is often called an aspherical lens....

es to create a new microscope which he would exhibit at the 1939 Annual Exhibition of the Physical Society
Physical Society of London
The Physical Society of London, England, existed from 1874 to 1921. It was a scientific society and produced the Proceedings of the Physical Society of London...

.

It was also during this time that Linfoot would marry fellow mathematician Joyce Dancer, with whom he would have two children, Margaret in 1945 and Sebastian in 1947.

During World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

 Linfoot put his skills to use for the Ministry of Aircraft Production, producing optical systems for air reconnaissance.

Cambridge astronomer

Following the war, Linfoot was awarded an ScD
Doctor of Science
Doctor of Science , usually abbreviated Sc.D., D.Sc., S.D. or Dr.Sc., is an academic research degree awarded in a number of countries throughout the world. In some countries Doctor of Science is the name used for the standard doctorate in the sciences, elsewhere the Sc.D...

 by the University of Oxford for his work in mathematics. A few months after this, Linfoot moved to the University of Cambridge, being appointed Assistant Director of the Cambridge Observatory
Cambridge Observatory
Cambridge Observatory is an astronomical observatory at the University of Cambridge in the East of England. It was first established in 1823 and is now part of the site of the Institute of Astronomy...

. He would remain at Cambridge until his retirement in 1970, eventually succeeding Dr H. A. Brück as John Couch Adams Astronomer.

During this time Linfoot took a great interest in Claude Shannon's new field of information theory
Information theory
Information theory is a branch of applied mathematics and electrical engineering involving the quantification of information. Information theory was developed by Claude E. Shannon to find fundamental limits on signal processing operations such as compressing data and on reliably storing and...

 and also in computers, writing several programs for the Electronic Delay Storage Automatic Calculator at Cambridge. He also wrote two books on optics, and seems to have planned a third.

His demonstrable skill at crafting optics was in demand, leading him to positions as a consultant for various groups and projects, including the construction of three large telescopes—the Schmidt–Cassegrain telescope, the Isaac Newton Telescope
Isaac Newton Telescope
The Isaac Newton Telescope or INT is a 2.54 m optical telescope run by the ING at Roque de los Muchachos Observatory on La Palma in the Canary Islands since 1984....

, and the Anglo-Australian Telescope
Anglo-Australian Telescope
The Anglo-Australian Telescope is a 3.9 m equatorially mounted telescope operated by the Australian Astronomical Observatory and situated at the Siding Spring Observatory, Australia at an altitude of a little over 1100 m...

—and for NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...

.

Linfoot died in Cambridge in 1982 at the age of 77.

Academic legacy

Linfoot's mathematical papers cover the period 1926–1939, all his subsequent work being on optics. These papers cover a wide range of areas in Fourier analysis, number theory, and probability, the first of these being applied later to his optical studies. His optics work was primarily concerned with synthesis, error balancing, assessment and testing. In particular he used his prodigious mathematical background to determine ways to improve and invent new optical configurations.
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