Paul Peter Ewald facts for kids

Quick facts for kids Paul Peter Ewald
Paul Peter Ewald in 1934
Born	(1888-01-23)January 23, 1888 Berlin, Germany
Died	August 23, 1985(1985-08-23) (aged 97) Ithaca, New York
Education	University of Cambridge University of Göttingen University of Munich
Known for	Ewald's sphere Ewald–Oseen extinction theorem Pendellösung Dynamical theory of diffraction
Parents	Paul Ewald (father) Clara Ewald (mother)
Scientific career
Institutions	Technische Hochschule Stuttgart Queen's University Belfast Polytechnic Institute of Brooklyn
Thesis	Dispersion und Doppelbrechung von Elektronengittern
Doctoral advisor	Arnold Sommerfeld
Other academic advisors	David Hilbert
Doctoral students	Achilles Papapetrou
Other notable students	Carl Hermann

Paul Peter Ewald was a famous German crystallographer and physicist. He was born in Berlin, Germany, on January 23, 1888, and passed away in Ithaca, New York, on August 22, 1985. Ewald was a very important scientist who helped create new ways to study materials using X-ray diffraction. He was also a Fellow of the Royal Society, which is a big honor for scientists.

Becoming a Scientist: Paul Ewald's Education

Paul Ewald started his schooling in Berlin and Potsdam. He learned many languages, including Greek, French, and English, along with his native German.

University Studies and Early Interests

In 1905, Ewald began studying physics, chemistry, and mathematics at Gonville and Caius College in Cambridge. He then moved to the University of Göttingen in 1906 and 1907. There, he became very interested in mathematics. Göttingen was a top place for math, with famous professors like Felix Klein, David Hilbert, and Hermann Minkowski.

While at Göttingen, Ewald worked for Professor Hilbert. He would take notes in Hilbert's classes and then make clean copies for the math reading room. In 1907, he continued his math studies at the Ludwig Maximilian University of Munich (LMU). He worked under Arnold Sommerfeld at his Institute for Theoretical Physics.

Doctoral Work and X-ray Discoveries

Ewald earned his doctorate degree in 1912. His main research was about how X-rays travel through crystals. After getting his degree, he continued to work as an assistant for Sommerfeld.

In 1911, Ewald was finishing his doctoral paper. He was talking to Max von Laue about his work. Ewald was studying how light waves, which are quite large, move through crystals. Laue wondered what would happen if much smaller waves were used. A few months later, in June 1912, Ewald heard that Laue and his team had successfully diffracted X-rays. X-rays have very small wavelengths, and this discovery earned Laue the Nobel Prize in Physics in 1914.

Helping Hilbert and Meeting His Future Wife

In 1912, David Hilbert asked Arnold Sommerfeld to send him a special assistant for physics. Sommerfeld sent Ewald, who was called "Hilbert's tutor for physics." Ewald helped Hilbert until 1913.

During his time in Göttingen, Ewald often visited a boarding house called El BoKaReBo. It was named after the first letters of the last names of the people living there. This is where Ewald met Ella Philippson, who later became his wife.

Studying Atomic Structure

In 1913, Niels Bohr published his famous Bohr atomic model. Later that year, Ewald attended a meeting where he heard about Bohr's model. This made Sommerfeld and his students very interested in studying atomic spectra and how atoms and molecules are built.

World War I and New Theories

During World War I, Ewald served in the German military as a medical technician. Even then, he kept thinking about physics. He developed the dynamical theory of X-ray diffraction. This theory explains how X-rays interact with crystals in a detailed way. After the war, he returned to LMU and completed his advanced degree (Habilitation) in 1917.

In 1921, Ewald published a paper about a method to study how electric fields work in crystals. This idea came to him during a skiing trip in 1911. His colleague, Peter Debye, helped him solve a difficult part of the calculation very quickly.

Paul Ewald's Career and Contributions

In 1921, Paul Ewald became a professor at the Technische Hochschule Stuttgart. He later used other job offers to improve his position there. In 1922, he became a full professor.

Leading Research and Publications

From 1922, Erwin Fues, another student of Sommerfeld, worked with Ewald at Stuttgart. In 1924, Ewald also became an editor for Zeitschrift für Kristallographie, a journal about crystals.

In 1929, Ewald was offered a job at another university. He used this offer to get more resources at Stuttgart. He got a second assistant and a separate building for his work. This building opened in 1930 as the Institute for Theoretical Physics, with Ewald as its director. The institute was set up like Sommerfeld's, doing both theoretical and experimental work.

In 1931, Ewald was put in charge of the physical science division.

Important Books and Concepts

Ewald wrote a detailed review of a book called Methoden der mathematischen Physik I, which was published in 1924. This book contained important math tools, like eigenvalues and eigenfunctions, that were needed for new physics theories like quantum mechanics.

Ewald's main work was in X-ray crystallography. He is known for the Ewald construction and the Ewald sphere. These are helpful ideas used to understand how X-rays diffract from crystals.

To make crystal data clearer, Ewald suggested collecting the best information into one publication. This led to the Internationale Tabellen zur Bestimmung von Kristallstrukturen, published in 1935. He also helped edit Strukturbericht Volume I (1913-1928) in 1931.

Moving to England and the United States

Ewald was chosen as the head (Rector) of Stuttgart University in 1932. However, due to growing problems with political groups in Germany, he resigned in 1933. He continued his work, but faced more difficulties. In 1937, he moved to England with his mother, the painter Clara Ewald. He worked in Cambridge and then became a lecturer at Queen's University Belfast in 1939. He later became a professor of mathematical physics there.

In 1937, Ewald's daughter, Rose, met Hans Bethe at Duke University in the United States. They got married in 1939, making Bethe Ewald's son-in-law.

Founding International Crystallography Organizations

Towards the end of World War II, Ewald worried that different countries would create their own competing journals for crystallography. So, in 1944, he suggested creating an International Union of Crystallography (IUCr). This union would be in charge of publishing all crystallography research.

In 1946, Ewald was chosen to lead the Provisional International Crystallographic Committee. He served until 1948, when the Union was officially formed. He was also nominated as the editor for the Union's journal. The first issue of Acta Crystallographica came out in 1948. That same year, Ewald led the first big meeting of the IUCr at Harvard University.

In 1952, Ewald was elected president of the American Crystallographic Association. He continued to be a leader in the IUCr, serving on its committee and as its Vice-President and President. He also edited Acta Crystallographica until 1959.

In 1949, Ewald moved to the United States and became a professor and head of the physics department at the Polytechnic Institute of Brooklyn. He retired from leading the department in 1957 and from teaching in 1959.

Honors and Awards

Paul Ewald received many awards for his important work:

• 1958 – He became a Fellow of the Royal Society.
• 1978 – He received the Max Planck medal from the Deutsche Physikalische Gesellschaft.
• 1979 – He was awarded the Gregori Aminoff Prize.
• 1986 – The International Union of Crystallography created the Ewald Prize in his honor. This prize is given for amazing contributions to the science of crystallography.

Books by Paul Peter Ewald

• Paul Peter Ewald wrote Kristalle und Röntgenstrahlen (Crystals and X-rays) in 1923.
• He co-authored The Physics of Solids and Fluids: With Recent Developments in 1930.
• Ewald also wrote Der Weg der Forschung (insbesondere der Physik) (The Path of Research, especially in Physics) in 1932.
• He edited 50 Years of X-Ray Diffraction in 1962, which was reprinted in 1999.
• In 1970, he wrote On the Foundations of Crystal Optics.

See also

• Ewald summation
• Ewald's sphere
• Multiple scattering theory
• Ewald–Oseen extinction theorem
• Pendellösung
• George Doundoulakis