Paul P. Ewald, who played a key role in development of the X-ray analysis of crystal structure now widely used in chemistry and physics, died at his home in Ithaca, N.Y., on Aug. 22, 1985, after long illness. He was 97 years old.
Ewald made a major contribution to the formation and growth of crystallography.
From 1913 to 1921, He developed a new way to represent the three-dimensional properties of a crystal under X-ray analysis, the so-called reciprocal lattice approach.
Ewald remained in the forefront of developments in X-ray crystallography and also devised a graphic method of solving the equation described by Sir Lawrence Bragg in 1912, the fundamental law of X-ray scattering, which involves a geometric construction now known as Ewald's sphere.
His interest in the behavior of light waves within crystals was born while he was working on his doctoral thesis at the University of Munich in 1912. His calculations, initially applicable to visible light, led later to his major contribution: the dynamic theory of X-ray interference in crystals, now used as an analytical tool by solid-state physicists and organic chemists.
Ewald was the author of several standard texts in crystallography and was active in international scientific efforts.
After World War II he helped re-establish the International Union of Pure and Applied Physics and became its secretary general.
From 1924 to 1940 he was coeditor of Zeitschrift für Kristallogra[hie, founded by Paul von Groth. With his pupil Carl Hermann he published the first volume of Strukturbericht. 1913–1928 as a supplement to Zeitschrift für Kristallographie (1931). Six volumes covering the period to 1939 were to follow. After the war Ewald was instrumental in continuing this review work as Structure Reports. Through his initiative and with W.L. Bragg's help, the International Union of Crystallography was founded in 1947 with Bragg as its president and Ewald as its vice president. From 1948 to 1958 Ewald served as one of the editors of its journal, Acta
Ewald was the son of Paul Ewald, a Privatdozent in history at the University of Berlin, and of Clara Philippson Ewald, an internationally known portrait painter. His father died of appendicitis shortly before Paul was born.
His mother raised Ewald, and as a result of their travels he learned to speak English and French at a very early age. He was educated at the Königliches Wilhelmsgymnasium in Berlin and the Königliches Victoriagymnasium in Potsdam.
Ewald graduated from the latter in 1905 and then began to study chemistry at Gonville and Caius College, Cambridge. In 1906, after on e semester, he entered the University of Göttingen to contingen to continue studying chemistry. He was, however, disappointed by the lack of consistent theoretical connection of the various facts of chemistry and soon changed to mathematics, which he studied for three semesters (1906–1907) Although he found his first mathematics courses at Göttingen not very helpful, he was compensated during the following semesters, when he worked with David Hilbert and Ernst Hellinger on differential and integral calculus.
Ewald transferred in 1907 to the University of Munich, where his two semesters of mathematical studies included Alfred Pringsheim's lectures on functional analysis. He also attended Arnold Sommerfeld's lectures on hydrodynamics. Fascinated by the interplay of theory and experiment in physics, he became Sommerfeld's student.
In 1910 Ewald chose as the subject of his doctoral dissertation the problem of how to find the optical properties of an anistropic arrangement of isotropic resonators, an area in which Sommerfeld could offer little help. Ewald's approach was quite original.ǀInstead if investigating the reaction of the dipoles on the incident light, he focused on the electromagnetic wave field that is "dynamically possible" in the interior of a lattice arrangement of oscillators. With the help of boundary considerations and especially by explicit calculations, in the reprint of his dissertation (1916) he could explain the "compensation [extinction] of the incident wave," the "dynamically closed" state of the refracted waves (the oscillation modes in the crystal), and the existence of reflected waves outside the crystal.
Among the difficulties Ewald had to overcome in working out his thesis was the calculation of the electromagnetic field exciting the dipole oscillations of any one atom. The problem was how to subtract from the entire field the one that originated from the atom itself. This amounted to subtracting infinity from infinity.
Fruitful in another way was Ewald's attempt to discuss some details of his dissertation with Max von Laue in February 1912. His dissertation, with its underlying assumption of a regular spatial arrangement of particles in a crystal, stimulated Laue to think of the phenomena produced by light of very short wavelength (comparable with atomic distances) in the space lattice of a crystal. The personal recollections of Laue and Ewald stress the unique situation in Munich, whe re Leonhard Sohncke and Paul von Groth allegedly had kept alive the space lattice theory of crystals and Sommerfeld advocated the wave theory of X rays.
Ewald did postdoctoral work at the University of Göttingen, where he was assistant to David Hilbert. In 1913, soon after his marriage to Elisa Berta (Ella) Philippson, he returned to Munich, at first sharing the post of assistant to Sommerfeld with Wilhelm Lenz. He had learned to operate X-ray equipment for medical purposes, so during World War I he was a field X-ray technician on the northern Russian front. By the autumn of 1915 fighting had practically ceased there, so he had time to continue his work on the crystal optics of X rays, which contains the elaborate dynamical theory of X-ray diffraction in perfect crystals.
In 1918 Ewald became Privatdozent at the University of Munich. He was named extraordinary professor of theoretical physics at the Technische Hochschule (now the University) of Stuttgart in 1921, and was appointed professor in 1922. While there, following the work of Richard Glocker, who as early as 1919 had done intensive experimental work on X-ray analysis of metal structures. Ewald helped to create a center of X-ray research and solid state physics.
Ewald was appointed rector at Stuttgart in 1932. In his inaugural address, he urged his audience to strive for social and political harmony, and he ended pathetically with the famous verse of the national anthem "Deutschland über alles." The following year, however, the National Socialists' "law for the restoration of the civil service" caused him to resign the rectorship because his wife was Jewish and he was part Jewish. However, his service at the front in World War I and the Nuremberg redefinition of "part Jewish," and a succession of nominal National Socialists as rectors, allowed him to continue his work as professor. In 1936. when a young Nazi teaching corps leader read a government paper denying the value of an "objective" science, Ewald walked out of the assembly. The new rector, an ardent National Socialist, urged Ewald to resign and had him pensioned off three weeks later.
In 1937 Ewald left Germany, a step he had been considering since 1933. With the help of William Lawrence Bragg, he was able to continue research at Cambridge, supported by a grant. In 1939 he was appointed lecturer, and later professor, of mathematical physics at Queen's University, Belfast. The financial circumstances of the family—there were four children—improved when Ewald accepted the latter post and, from 1949, when he was professor of physics and head of the department at the Polytechnic Institute of Brooklyn. He retired in 1959.
Ewald was a member or fellow of the American Academy of Arts and Sciences, the Royal Society, and the Deutsche Akademie der Naturforscher (Leopoldina). He received honorary doctorates from the University of Stuttgart in 1954, from the University of Paris in 1958, and from the University of Munich in 1968. In 1978 the Deutsche Physikalische Gesellschaft awarded him the Max Planck Medal, and the following year he received the first Gregori Aminoff Medal of the Royal Swedish Academy.
Dr. Ewald is survived by his wife, the former Ella Phillippson; two sons, Lux and Arnold; two daughters, Rose Bethe and Linde Davidson, and eight grandchildren and two great grandchildren.
Information from the American Academy of Sciences; The New York Times, September 7, 1985
Born in Berlin, Maaßenstraße 31, Ortsteil Schöneberg, Bezirk Tempelhof-Schöneberg, Bundeshauptstadt, Regierungssitz, Germany on 23. Januar 1888 to Julius Moritz Paul Ewald and Clara Marie Ottilie Bertha Philippson.
Peter Paul Ewald married Elise Ella Berta Phillippson and had 2 children. He passed away on 23 Aug 1985 in Ithaca, Tompkins, NY, USA.
Information from Ancestry
Biographical materials contributed by Starfishin [#48860385]
Ewald made a major contribution to the formation and growth of crystallography.
From 1913 to 1921, He developed a new way to represent the three-dimensional properties of a crystal under X-ray analysis, the so-called reciprocal lattice approach.
Ewald remained in the forefront of developments in X-ray crystallography and also devised a graphic method of solving the equation described by Sir Lawrence Bragg in 1912, the fundamental law of X-ray scattering, which involves a geometric construction now known as Ewald's sphere.
His interest in the behavior of light waves within crystals was born while he was working on his doctoral thesis at the University of Munich in 1912. His calculations, initially applicable to visible light, led later to his major contribution: the dynamic theory of X-ray interference in crystals, now used as an analytical tool by solid-state physicists and organic chemists.
Ewald was the author of several standard texts in crystallography and was active in international scientific efforts.
After World War II he helped re-establish the International Union of Pure and Applied Physics and became its secretary general.
From 1924 to 1940 he was coeditor of Zeitschrift für Kristallogra[hie, founded by Paul von Groth. With his pupil Carl Hermann he published the first volume of Strukturbericht. 1913–1928 as a supplement to Zeitschrift für Kristallographie (1931). Six volumes covering the period to 1939 were to follow. After the war Ewald was instrumental in continuing this review work as Structure Reports. Through his initiative and with W.L. Bragg's help, the International Union of Crystallography was founded in 1947 with Bragg as its president and Ewald as its vice president. From 1948 to 1958 Ewald served as one of the editors of its journal, Acta
Ewald was the son of Paul Ewald, a Privatdozent in history at the University of Berlin, and of Clara Philippson Ewald, an internationally known portrait painter. His father died of appendicitis shortly before Paul was born.
His mother raised Ewald, and as a result of their travels he learned to speak English and French at a very early age. He was educated at the Königliches Wilhelmsgymnasium in Berlin and the Königliches Victoriagymnasium in Potsdam.
Ewald graduated from the latter in 1905 and then began to study chemistry at Gonville and Caius College, Cambridge. In 1906, after on e semester, he entered the University of Göttingen to contingen to continue studying chemistry. He was, however, disappointed by the lack of consistent theoretical connection of the various facts of chemistry and soon changed to mathematics, which he studied for three semesters (1906–1907) Although he found his first mathematics courses at Göttingen not very helpful, he was compensated during the following semesters, when he worked with David Hilbert and Ernst Hellinger on differential and integral calculus.
Ewald transferred in 1907 to the University of Munich, where his two semesters of mathematical studies included Alfred Pringsheim's lectures on functional analysis. He also attended Arnold Sommerfeld's lectures on hydrodynamics. Fascinated by the interplay of theory and experiment in physics, he became Sommerfeld's student.
In 1910 Ewald chose as the subject of his doctoral dissertation the problem of how to find the optical properties of an anistropic arrangement of isotropic resonators, an area in which Sommerfeld could offer little help. Ewald's approach was quite original.ǀInstead if investigating the reaction of the dipoles on the incident light, he focused on the electromagnetic wave field that is "dynamically possible" in the interior of a lattice arrangement of oscillators. With the help of boundary considerations and especially by explicit calculations, in the reprint of his dissertation (1916) he could explain the "compensation [extinction] of the incident wave," the "dynamically closed" state of the refracted waves (the oscillation modes in the crystal), and the existence of reflected waves outside the crystal.
Among the difficulties Ewald had to overcome in working out his thesis was the calculation of the electromagnetic field exciting the dipole oscillations of any one atom. The problem was how to subtract from the entire field the one that originated from the atom itself. This amounted to subtracting infinity from infinity.
Fruitful in another way was Ewald's attempt to discuss some details of his dissertation with Max von Laue in February 1912. His dissertation, with its underlying assumption of a regular spatial arrangement of particles in a crystal, stimulated Laue to think of the phenomena produced by light of very short wavelength (comparable with atomic distances) in the space lattice of a crystal. The personal recollections of Laue and Ewald stress the unique situation in Munich, whe re Leonhard Sohncke and Paul von Groth allegedly had kept alive the space lattice theory of crystals and Sommerfeld advocated the wave theory of X rays.
Ewald did postdoctoral work at the University of Göttingen, where he was assistant to David Hilbert. In 1913, soon after his marriage to Elisa Berta (Ella) Philippson, he returned to Munich, at first sharing the post of assistant to Sommerfeld with Wilhelm Lenz. He had learned to operate X-ray equipment for medical purposes, so during World War I he was a field X-ray technician on the northern Russian front. By the autumn of 1915 fighting had practically ceased there, so he had time to continue his work on the crystal optics of X rays, which contains the elaborate dynamical theory of X-ray diffraction in perfect crystals.
In 1918 Ewald became Privatdozent at the University of Munich. He was named extraordinary professor of theoretical physics at the Technische Hochschule (now the University) of Stuttgart in 1921, and was appointed professor in 1922. While there, following the work of Richard Glocker, who as early as 1919 had done intensive experimental work on X-ray analysis of metal structures. Ewald helped to create a center of X-ray research and solid state physics.
Ewald was appointed rector at Stuttgart in 1932. In his inaugural address, he urged his audience to strive for social and political harmony, and he ended pathetically with the famous verse of the national anthem "Deutschland über alles." The following year, however, the National Socialists' "law for the restoration of the civil service" caused him to resign the rectorship because his wife was Jewish and he was part Jewish. However, his service at the front in World War I and the Nuremberg redefinition of "part Jewish," and a succession of nominal National Socialists as rectors, allowed him to continue his work as professor. In 1936. when a young Nazi teaching corps leader read a government paper denying the value of an "objective" science, Ewald walked out of the assembly. The new rector, an ardent National Socialist, urged Ewald to resign and had him pensioned off three weeks later.
In 1937 Ewald left Germany, a step he had been considering since 1933. With the help of William Lawrence Bragg, he was able to continue research at Cambridge, supported by a grant. In 1939 he was appointed lecturer, and later professor, of mathematical physics at Queen's University, Belfast. The financial circumstances of the family—there were four children—improved when Ewald accepted the latter post and, from 1949, when he was professor of physics and head of the department at the Polytechnic Institute of Brooklyn. He retired in 1959.
Ewald was a member or fellow of the American Academy of Arts and Sciences, the Royal Society, and the Deutsche Akademie der Naturforscher (Leopoldina). He received honorary doctorates from the University of Stuttgart in 1954, from the University of Paris in 1958, and from the University of Munich in 1968. In 1978 the Deutsche Physikalische Gesellschaft awarded him the Max Planck Medal, and the following year he received the first Gregori Aminoff Medal of the Royal Swedish Academy.
Dr. Ewald is survived by his wife, the former Ella Phillippson; two sons, Lux and Arnold; two daughters, Rose Bethe and Linde Davidson, and eight grandchildren and two great grandchildren.
Information from the American Academy of Sciences; The New York Times, September 7, 1985
Born in Berlin, Maaßenstraße 31, Ortsteil Schöneberg, Bezirk Tempelhof-Schöneberg, Bundeshauptstadt, Regierungssitz, Germany on 23. Januar 1888 to Julius Moritz Paul Ewald and Clara Marie Ottilie Bertha Philippson.
Peter Paul Ewald married Elise Ella Berta Phillippson and had 2 children. He passed away on 23 Aug 1985 in Ithaca, Tompkins, NY, USA.
Information from Ancestry
Biographical materials contributed by Starfishin [#48860385]
Paul P. Ewald, who played a key role in development of the X-ray analysis of crystal structure now widely used in chemistry and physics, died at his home in Ithaca, N.Y., on Aug. 22, 1985, after long illness. He was 97 years old.
Ewald made a major contribution to the formation and growth of crystallography.
From 1913 to 1921, He developed a new way to represent the three-dimensional properties of a crystal under X-ray analysis, the so-called reciprocal lattice approach.
Ewald remained in the forefront of developments in X-ray crystallography and also devised a graphic method of solving the equation described by Sir Lawrence Bragg in 1912, the fundamental law of X-ray scattering, which involves a geometric construction now known as Ewald's sphere.
His interest in the behavior of light waves within crystals was born while he was working on his doctoral thesis at the University of Munich in 1912. His calculations, initially applicable to visible light, led later to his major contribution: the dynamic theory of X-ray interference in crystals, now used as an analytical tool by solid-state physicists and organic chemists.
Ewald was the author of several standard texts in crystallography and was active in international scientific efforts.
After World War II he helped re-establish the International Union of Pure and Applied Physics and became its secretary general.
From 1924 to 1940 he was coeditor of Zeitschrift für Kristallogra[hie, founded by Paul von Groth. With his pupil Carl Hermann he published the first volume of Strukturbericht. 1913–1928 as a supplement to Zeitschrift für Kristallographie (1931). Six volumes covering the period to 1939 were to follow. After the war Ewald was instrumental in continuing this review work as Structure Reports. Through his initiative and with W.L. Bragg's help, the International Union of Crystallography was founded in 1947 with Bragg as its president and Ewald as its vice president. From 1948 to 1958 Ewald served as one of the editors of its journal, Acta
Ewald was the son of Paul Ewald, a Privatdozent in history at the University of Berlin, and of Clara Philippson Ewald, an internationally known portrait painter. His father died of appendicitis shortly before Paul was born.
His mother raised Ewald, and as a result of their travels he learned to speak English and French at a very early age. He was educated at the Königliches Wilhelmsgymnasium in Berlin and the Königliches Victoriagymnasium in Potsdam.
Ewald graduated from the latter in 1905 and then began to study chemistry at Gonville and Caius College, Cambridge. In 1906, after on e semester, he entered the University of Göttingen to contingen to continue studying chemistry. He was, however, disappointed by the lack of consistent theoretical connection of the various facts of chemistry and soon changed to mathematics, which he studied for three semesters (1906–1907) Although he found his first mathematics courses at Göttingen not very helpful, he was compensated during the following semesters, when he worked with David Hilbert and Ernst Hellinger on differential and integral calculus.
Ewald transferred in 1907 to the University of Munich, where his two semesters of mathematical studies included Alfred Pringsheim's lectures on functional analysis. He also attended Arnold Sommerfeld's lectures on hydrodynamics. Fascinated by the interplay of theory and experiment in physics, he became Sommerfeld's student.
In 1910 Ewald chose as the subject of his doctoral dissertation the problem of how to find the optical properties of an anistropic arrangement of isotropic resonators, an area in which Sommerfeld could offer little help. Ewald's approach was quite original.ǀInstead if investigating the reaction of the dipoles on the incident light, he focused on the electromagnetic wave field that is "dynamically possible" in the interior of a lattice arrangement of oscillators. With the help of boundary considerations and especially by explicit calculations, in the reprint of his dissertation (1916) he could explain the "compensation [extinction] of the incident wave," the "dynamically closed" state of the refracted waves (the oscillation modes in the crystal), and the existence of reflected waves outside the crystal.
Among the difficulties Ewald had to overcome in working out his thesis was the calculation of the electromagnetic field exciting the dipole oscillations of any one atom. The problem was how to subtract from the entire field the one that originated from the atom itself. This amounted to subtracting infinity from infinity.
Fruitful in another way was Ewald's attempt to discuss some details of his dissertation with Max von Laue in February 1912. His dissertation, with its underlying assumption of a regular spatial arrangement of particles in a crystal, stimulated Laue to think of the phenomena produced by light of very short wavelength (comparable with atomic distances) in the space lattice of a crystal. The personal recollections of Laue and Ewald stress the unique situation in Munich, whe re Leonhard Sohncke and Paul von Groth allegedly had kept alive the space lattice theory of crystals and Sommerfeld advocated the wave theory of X rays.
Ewald did postdoctoral work at the University of Göttingen, where he was assistant to David Hilbert. In 1913, soon after his marriage to Elisa Berta (Ella) Philippson, he returned to Munich, at first sharing the post of assistant to Sommerfeld with Wilhelm Lenz. He had learned to operate X-ray equipment for medical purposes, so during World War I he was a field X-ray technician on the northern Russian front. By the autumn of 1915 fighting had practically ceased there, so he had time to continue his work on the crystal optics of X rays, which contains the elaborate dynamical theory of X-ray diffraction in perfect crystals.
In 1918 Ewald became Privatdozent at the University of Munich. He was named extraordinary professor of theoretical physics at the Technische Hochschule (now the University) of Stuttgart in 1921, and was appointed professor in 1922. While there, following the work of Richard Glocker, who as early as 1919 had done intensive experimental work on X-ray analysis of metal structures. Ewald helped to create a center of X-ray research and solid state physics.
Ewald was appointed rector at Stuttgart in 1932. In his inaugural address, he urged his audience to strive for social and political harmony, and he ended pathetically with the famous verse of the national anthem "Deutschland über alles." The following year, however, the National Socialists' "law for the restoration of the civil service" caused him to resign the rectorship because his wife was Jewish and he was part Jewish. However, his service at the front in World War I and the Nuremberg redefinition of "part Jewish," and a succession of nominal National Socialists as rectors, allowed him to continue his work as professor. In 1936. when a young Nazi teaching corps leader read a government paper denying the value of an "objective" science, Ewald walked out of the assembly. The new rector, an ardent National Socialist, urged Ewald to resign and had him pensioned off three weeks later.
In 1937 Ewald left Germany, a step he had been considering since 1933. With the help of William Lawrence Bragg, he was able to continue research at Cambridge, supported by a grant. In 1939 he was appointed lecturer, and later professor, of mathematical physics at Queen's University, Belfast. The financial circumstances of the family—there were four children—improved when Ewald accepted the latter post and, from 1949, when he was professor of physics and head of the department at the Polytechnic Institute of Brooklyn. He retired in 1959.
Ewald was a member or fellow of the American Academy of Arts and Sciences, the Royal Society, and the Deutsche Akademie der Naturforscher (Leopoldina). He received honorary doctorates from the University of Stuttgart in 1954, from the University of Paris in 1958, and from the University of Munich in 1968. In 1978 the Deutsche Physikalische Gesellschaft awarded him the Max Planck Medal, and the following year he received the first Gregori Aminoff Medal of the Royal Swedish Academy.
Dr. Ewald is survived by his wife, the former Ella Phillippson; two sons, Lux and Arnold; two daughters, Rose Bethe and Linde Davidson, and eight grandchildren and two great grandchildren.
Information from the American Academy of Sciences; The New York Times, September 7, 1985
Born in Berlin, Maaßenstraße 31, Ortsteil Schöneberg, Bezirk Tempelhof-Schöneberg, Bundeshauptstadt, Regierungssitz, Germany on 23. Januar 1888 to Julius Moritz Paul Ewald and Clara Marie Ottilie Bertha Philippson.
Peter Paul Ewald married Elise Ella Berta Phillippson and had 2 children. He passed away on 23 Aug 1985 in Ithaca, Tompkins, NY, USA.
Information from Ancestry
Biographical materials contributed by Starfishin [#48860385]
Ewald made a major contribution to the formation and growth of crystallography.
From 1913 to 1921, He developed a new way to represent the three-dimensional properties of a crystal under X-ray analysis, the so-called reciprocal lattice approach.
Ewald remained in the forefront of developments in X-ray crystallography and also devised a graphic method of solving the equation described by Sir Lawrence Bragg in 1912, the fundamental law of X-ray scattering, which involves a geometric construction now known as Ewald's sphere.
His interest in the behavior of light waves within crystals was born while he was working on his doctoral thesis at the University of Munich in 1912. His calculations, initially applicable to visible light, led later to his major contribution: the dynamic theory of X-ray interference in crystals, now used as an analytical tool by solid-state physicists and organic chemists.
Ewald was the author of several standard texts in crystallography and was active in international scientific efforts.
After World War II he helped re-establish the International Union of Pure and Applied Physics and became its secretary general.
From 1924 to 1940 he was coeditor of Zeitschrift für Kristallogra[hie, founded by Paul von Groth. With his pupil Carl Hermann he published the first volume of Strukturbericht. 1913–1928 as a supplement to Zeitschrift für Kristallographie (1931). Six volumes covering the period to 1939 were to follow. After the war Ewald was instrumental in continuing this review work as Structure Reports. Through his initiative and with W.L. Bragg's help, the International Union of Crystallography was founded in 1947 with Bragg as its president and Ewald as its vice president. From 1948 to 1958 Ewald served as one of the editors of its journal, Acta
Ewald was the son of Paul Ewald, a Privatdozent in history at the University of Berlin, and of Clara Philippson Ewald, an internationally known portrait painter. His father died of appendicitis shortly before Paul was born.
His mother raised Ewald, and as a result of their travels he learned to speak English and French at a very early age. He was educated at the Königliches Wilhelmsgymnasium in Berlin and the Königliches Victoriagymnasium in Potsdam.
Ewald graduated from the latter in 1905 and then began to study chemistry at Gonville and Caius College, Cambridge. In 1906, after on e semester, he entered the University of Göttingen to contingen to continue studying chemistry. He was, however, disappointed by the lack of consistent theoretical connection of the various facts of chemistry and soon changed to mathematics, which he studied for three semesters (1906–1907) Although he found his first mathematics courses at Göttingen not very helpful, he was compensated during the following semesters, when he worked with David Hilbert and Ernst Hellinger on differential and integral calculus.
Ewald transferred in 1907 to the University of Munich, where his two semesters of mathematical studies included Alfred Pringsheim's lectures on functional analysis. He also attended Arnold Sommerfeld's lectures on hydrodynamics. Fascinated by the interplay of theory and experiment in physics, he became Sommerfeld's student.
In 1910 Ewald chose as the subject of his doctoral dissertation the problem of how to find the optical properties of an anistropic arrangement of isotropic resonators, an area in which Sommerfeld could offer little help. Ewald's approach was quite original.ǀInstead if investigating the reaction of the dipoles on the incident light, he focused on the electromagnetic wave field that is "dynamically possible" in the interior of a lattice arrangement of oscillators. With the help of boundary considerations and especially by explicit calculations, in the reprint of his dissertation (1916) he could explain the "compensation [extinction] of the incident wave," the "dynamically closed" state of the refracted waves (the oscillation modes in the crystal), and the existence of reflected waves outside the crystal.
Among the difficulties Ewald had to overcome in working out his thesis was the calculation of the electromagnetic field exciting the dipole oscillations of any one atom. The problem was how to subtract from the entire field the one that originated from the atom itself. This amounted to subtracting infinity from infinity.
Fruitful in another way was Ewald's attempt to discuss some details of his dissertation with Max von Laue in February 1912. His dissertation, with its underlying assumption of a regular spatial arrangement of particles in a crystal, stimulated Laue to think of the phenomena produced by light of very short wavelength (comparable with atomic distances) in the space lattice of a crystal. The personal recollections of Laue and Ewald stress the unique situation in Munich, whe re Leonhard Sohncke and Paul von Groth allegedly had kept alive the space lattice theory of crystals and Sommerfeld advocated the wave theory of X rays.
Ewald did postdoctoral work at the University of Göttingen, where he was assistant to David Hilbert. In 1913, soon after his marriage to Elisa Berta (Ella) Philippson, he returned to Munich, at first sharing the post of assistant to Sommerfeld with Wilhelm Lenz. He had learned to operate X-ray equipment for medical purposes, so during World War I he was a field X-ray technician on the northern Russian front. By the autumn of 1915 fighting had practically ceased there, so he had time to continue his work on the crystal optics of X rays, which contains the elaborate dynamical theory of X-ray diffraction in perfect crystals.
In 1918 Ewald became Privatdozent at the University of Munich. He was named extraordinary professor of theoretical physics at the Technische Hochschule (now the University) of Stuttgart in 1921, and was appointed professor in 1922. While there, following the work of Richard Glocker, who as early as 1919 had done intensive experimental work on X-ray analysis of metal structures. Ewald helped to create a center of X-ray research and solid state physics.
Ewald was appointed rector at Stuttgart in 1932. In his inaugural address, he urged his audience to strive for social and political harmony, and he ended pathetically with the famous verse of the national anthem "Deutschland über alles." The following year, however, the National Socialists' "law for the restoration of the civil service" caused him to resign the rectorship because his wife was Jewish and he was part Jewish. However, his service at the front in World War I and the Nuremberg redefinition of "part Jewish," and a succession of nominal National Socialists as rectors, allowed him to continue his work as professor. In 1936. when a young Nazi teaching corps leader read a government paper denying the value of an "objective" science, Ewald walked out of the assembly. The new rector, an ardent National Socialist, urged Ewald to resign and had him pensioned off three weeks later.
In 1937 Ewald left Germany, a step he had been considering since 1933. With the help of William Lawrence Bragg, he was able to continue research at Cambridge, supported by a grant. In 1939 he was appointed lecturer, and later professor, of mathematical physics at Queen's University, Belfast. The financial circumstances of the family—there were four children—improved when Ewald accepted the latter post and, from 1949, when he was professor of physics and head of the department at the Polytechnic Institute of Brooklyn. He retired in 1959.
Ewald was a member or fellow of the American Academy of Arts and Sciences, the Royal Society, and the Deutsche Akademie der Naturforscher (Leopoldina). He received honorary doctorates from the University of Stuttgart in 1954, from the University of Paris in 1958, and from the University of Munich in 1968. In 1978 the Deutsche Physikalische Gesellschaft awarded him the Max Planck Medal, and the following year he received the first Gregori Aminoff Medal of the Royal Swedish Academy.
Dr. Ewald is survived by his wife, the former Ella Phillippson; two sons, Lux and Arnold; two daughters, Rose Bethe and Linde Davidson, and eight grandchildren and two great grandchildren.
Information from the American Academy of Sciences; The New York Times, September 7, 1985
Born in Berlin, Maaßenstraße 31, Ortsteil Schöneberg, Bezirk Tempelhof-Schöneberg, Bundeshauptstadt, Regierungssitz, Germany on 23. Januar 1888 to Julius Moritz Paul Ewald and Clara Marie Ottilie Bertha Philippson.
Peter Paul Ewald married Elise Ella Berta Phillippson and had 2 children. He passed away on 23 Aug 1985 in Ithaca, Tompkins, NY, USA.
Information from Ancestry
Biographical materials contributed by Starfishin [#48860385]
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