Adriaan Daniël Fokker (; 17 August 1887 – 24 September 1972) was a Dutch

physicist A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe. Physicists generally are interested in the root or ultimate cau ...

. He worked in the fields of

special relativity In physics, the special theory of relativity, or special relativity for short, is a scientific theory of the relationship between Spacetime, space and time. In Albert Einstein's 1905 paper, Annus Mirabilis papers#Special relativity, "On the Ele ...

and

statistical mechanics In physics, statistical mechanics is a mathematical framework that applies statistical methods and probability theory to large assemblies of microscopic entities. Sometimes called statistical physics or statistical thermodynamics, its applicati ...

. He was the inventor of the

Fokker organ Adriaan Daniël Fokker (; 17 August 1887 – 24 September 1972) was a Dutch physicist. He worked in the fields of special relativity and statistical mechanics. He was the inventor of the Fokker organ, a 31-tone equal-tempered (31-TET) organ. ...

, a 31-tone equal-tempered (31-TET) organ.

Life and work

Adriaan Daniël Fokker was born on 17 August 1887 in Buitenzorg,

Dutch East Indies The Dutch East Indies, also known as the Netherlands East Indies (; ), was a Dutch Empire, Dutch colony with territory mostly comprising the modern state of Indonesia, which Proclamation of Indonesian Independence, declared independence on 17 Au ...

(now

Bogor Bogor City (), or Bogor (, ), is a landlocked city in the West Java, Indonesia. Located around south of the national capital of Jakarta, Bogor is the 6th largest city in the Jakarta metropolitan area and the 14th overall nationwide.

Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania, between the Indian Ocean, Indian and Pacific Ocean, Pacific oceans. Comprising over List of islands of Indonesia, 17,000 islands, including Sumatra, ...

), the son of Anthony Herman Gerard Fokker, president of the branch of the

Netherlands Trading Society The Netherlands Trading Society ( or NHM) was a Dutch trading and financial company, established in 1824, in The Hague by King William I to promote and develop trade, shipping and agriculture. For the next 140 years the NHM developed a large int ...

Batavia, Dutch East Indies Batavia was the capital of the Dutch East Indies. The area corresponds to present-day Jakarta, Indonesia. Batavia can refer to the city proper or its suburbs and hinterland, the , which included the much larger area of the Residency of Batavia ...

, and Susanna Alida der Kinderen. He was a cousin of the

aeronautical Aeronautics is the science or art involved with the study, design, and manufacturing of air flight-capable machines, and the techniques of operating aircraft and rockets within the atmosphere. While the term originally referred solely to ''ope ...

engineer Engineers, as practitioners of engineering, are professionals who Invention, invent, design, build, maintain and test machines, complex systems, structures, gadgets and materials. They aim to fulfill functional objectives and requirements while ...

Anthony Fokker Anton Herman Gerard "Anthony" Fokker (6 April 1890 – 23 December 1939) was a Dutch aviation pioneer, aviation entrepreneur, aircraft designer, and aircraft manufacturer. He produced fighter aircraft in Germany during the First World War such ...

. Fokker studied

mining engineering Mining engineering is the extraction of minerals from the ground. It is associated with many other disciplines, such as mineral processing, exploration, excavation, geology, metallurgy, geotechnical engineering and surveying. A mining engineer m ...

at the

Delft University of Technology The Delft University of Technology (TU Delft; ) is the oldest and largest Dutch public university, public Institute of technology, technical university, located in Delft, Netherlands. It specializes in engineering, technology, computing, design, a ...

and

physics Physics is the scientific study of matter, its Elementary particle, 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 whi ...

at the

University of Leiden Leiden University (abbreviated as ''LEI''; ) is a public research university in Leiden, Netherlands. Established in 1575 by William, Prince of Orange as a Protestant institution, it holds the distinction of being the oldest university in the Neth ...

with

Hendrik Lorentz Hendrik Antoon Lorentz ( ; ; 18 July 1853 – 4 February 1928) was a Dutch theoretical physicist who shared the 1902 Nobel Prize in Physics with Pieter Zeeman for their discovery and theoretical explanation of the Zeeman effect. He derive ...

, where he earned his

doctorate A doctorate (from Latin ''doctor'', meaning "teacher") or doctoral degree is a postgraduate academic degree awarded by universities and some other educational institutions, derived from the ancient formalism '' licentia docendi'' ("licence to teach ...

in 1913. He continued his studies with

Albert Einstein Albert Einstein (14 March 187918 April 1955) was a German-born theoretical physicist who is best known for developing the theory of relativity. Einstein also made important contributions to quantum mechanics. His mass–energy equivalence f ...

Ernest Rutherford Ernest Rutherford, 1st Baron Rutherford of Nelson (30 August 1871 – 19 October 1937) was a New Zealand physicist who was a pioneering researcher in both Atomic physics, atomic and nuclear physics. He has been described as "the father of nu ...

and William Bragg. In his 1913 thesis, he derived the

Fokker–Planck equation In statistical mechanics and information theory, the Fokker–Planck equation is a partial differential equation that describes the time evolution of the probability density function of the velocity of a particle under the influence of drag (physi ...

along with

Max Planck Max Karl Ernst Ludwig Planck (; ; 23 April 1858 – 4 October 1947) was a German Theoretical physics, theoretical physicist whose discovery of energy quantum, quanta won him the Nobel Prize in Physics in 1918. Planck made many substantial con ...

. After his

military service Military service is service by an individual or group in an army or other militia, air forces, and naval forces, whether as a chosen job (volunteer military, volunteer) or as a result of an involuntary draft (conscription). Few nations, such ...

during

World War I World War I or the First World War (28 July 1914 – 11 November 1918), also known as the Great War, was a World war, global conflict between two coalitions: the Allies of World War I, Allies (or Entente) and the Central Powers. Fighting to ...

he returned to

Leiden Leiden ( ; ; in English language, English and Archaism, archaic Dutch language, Dutch also Leyden) is a List of cities in the Netherlands by province, city and List of municipalities of the Netherlands, municipality in the Provinces of the Nethe ...

as Lorentz' and Ehrenfest's assistant. Fokker became a physics teacher at the Gymnasium of Delft after 1918 and was appointed in 1923 as the first professor of Applied Physics at the Technische Hoogeschool Delft (today Delft University of Technology). In 1928 Fokker succeeded

as director of research at

Teylers Museum Teylers Museum () is an Art museum, art, Natural history museum, natural history, and science museum in Haarlem, Netherlands. Established in 1778, Teylers Museum was founded as a centre for contemporary art and science. The historic centre of the ...

Haarlem Haarlem (; predecessor of ''Harlem'' in English language, English) is a List of cities in the Netherlands by province, city and Municipalities of the Netherlands, municipality in the Netherlands. It is the capital of the Provinces of the Nether ...

. Fokker made several contributions to

, and some less well-known contributions to

general relativity General relativity, also known as the general theory of relativity, and as Einstein's theory of gravity, is the differential geometry, geometric theory of gravitation published by Albert Einstein in 1915 and is the current description of grav ...

, particularly in the area of geodetic precession, the phenomena of precession of a freely falling gyroscope in a gravitational field. Fokker began to study

music theory Music theory is the study of theoretical frameworks for understanding the practices and possibilities of music. ''The Oxford Companion to Music'' describes three interrelated uses of the term "music theory": The first is the "Elements of music, ...

during the

Second World War World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...

, when the University of Leiden was closed; partly this was due to a desire to convince the

Nazis Nazism (), formally named National Socialism (NS; , ), is the far-right politics, far-right Totalitarianism, totalitarian socio-political ideology and practices associated with Adolf Hitler and the Nazi Party (NSDAP) in Germany. During H ...

he would be of no use to the war effort, and partly it was a response to reading the work of

Christiaan Huygens Christiaan Huygens, Halen, Lord of Zeelhem, ( , ; ; also spelled Huyghens; ; 14 April 1629 – 8 July 1695) was a Dutch mathematician, physicist, engineer, astronomer, and inventor who is regarded as a key figure in the Scientific Revolution ...

on the

31 equal temperament In music, 31 equal temperament, which can also be abbreviated (31 tone ) or (equal division of the octave), also known as tricesimoprimal, is the tempered scale derived by dividing the octave into 31 equally-proportioned steps (e ...

. In 1938, Fokker – along with

Dirk Coster Dirk Coster (5 October 1889 – 12 February 1950) was a Dutch physicist. He was a professor of physics and meteorology at the University of Groningen. Coster is known as the co-discoverer of hafnium (element 72) in 1923, along with George de ...

and

Otto Hahn Otto Hahn (; 8 March 1879 – 28 July 1968) was a German chemist who was a pioneer in the field of radiochemistry. He is referred to as the father of nuclear chemistry and discoverer of nuclear fission, the science behind nuclear reactors and ...

– helped Jewish-born physicist

Lise Meitner Elise Lise Meitner ( ; ; 7 November 1878 – 27 October 1968) was an Austrian-Swedish nuclear physicist who was instrumental in the discovery of nuclear fission. After completing her doctoral research in 1906, Meitner became the second woman ...

escape from Austria to the Netherlands. Historian

Ruth Lewin Sime Ruth Lewin Sime is an American author, educator and scientific researcher, best known for publishing works on history of science.harmonic In physics, acoustics, and telecommunications, a harmonic is a sinusoidal wave with a frequency that is a positive integer multiple of the ''fundamental frequency'' of a periodic signal. The fundamental frequency is also called the ''1st har ...

as a consonant interval (31-equal has a much better approximation of the 7th harmonic than the ubiquitous 12-equal). He also made notable contributions to music theory, such as the Fokker periodicity block. In 1949 he became member of the

Royal Netherlands Academy of Arts and Sciences The Royal Netherlands Academy of Arts and Sciences (, KNAW) is an organization dedicated to the advancement of science and literature in the Netherlands. The academy is housed in the Trippenhuis in Amsterdam. In addition to various advisory a ...

. He died on 24 September 1972, at the age of 85, in

Beekbergen Beekbergen (; or ''Beekbargen'') is a village and former municipality in the Dutch province of Gelderland. It is located in the municipality of Apeldoorn on the edge of the Veluwe. The rural area on the southwestern side of the village is domi ...

near

Apeldoorn Apeldoorn (; Dutch Low Saxon: ) is a municipality and city in the province of Gelderland in the centre of the Netherlands. The municipality of Apeldoorn, including the villages of Beekbergen, Loenen (Apeldoorn), Loenen, Ugchelen and Hoenderloo ...

Musical instruments

Fokker designed and had built a number of keyboard instruments capable of playing microtonal scales via a

generalized keyboard Generalized keyboards are musical keyboards, a type of isomorphic keyboard, with regular, tile-like arrangements usually with rectangular or hexagonal keys, and were developed for performing music in different tunings. They were introduced by R ...

. The best-known of these is his 31-tone equal-tempered organ, which was installed in Teyler's Museum in Haarlem in 1951. It is commonly called the Fokker organ. The Fokker organ is currently property of the

Huygens-Fokker Foundation The Huygens-Fokker Foundation () is a "centre for microtonal music" founded on February 15, 1960, housed in the Muziekgebouw aan 't IJ (Amsterdam, Netherlands), and named for Christiaan Huygens and Adriaan Fokker (inventor of 31 equal temperamen ...

and it moved to the Bamzaal in

Muziekgebouw aan 't IJ Muziekgebouw aan 't IJ ( English: "Music Building on the IJ") is the main concert hall for contemporary classical music on the IJ in Amsterdam, Netherlands. The building opened in 2005 and is located above the IJtunnel, a ten-minute walk from ...

. Regularly concerts take place on this instrument in the Bamzaal.

References and notes

External links

Fokker organ
Huygens-Fokker Foundation.
Oral history interview transcript with Adriaan Fokker on 1 April 1963, American Institute of Physics, Niels Bohr Library & Archives

Adriaan Fokker and the Archiphone on '120 Years Of Electronic Music'
from the

Huygens–Fokker Foundation The Huygens-Fokker Foundation () is a "centre for microtonal music" founded on February 15, 1960, housed in the Muziekgebouw aan 't IJ (Amsterdam, Netherlands), and named for Christiaan Huygens and Adriaan Fokker (inventor of 31 equal temperament ...

* H.A.M. Snelders,
Fokker, Adriaan Daniël (1887–1972)
, in Biografisch Woordenboek van Nederland. 3-03-2008 {{DEFAULTSORT:Fokker, Adriaan 1887 births 1972 deaths 20th-century Dutch physicists 20th-century Dutch inventors Microtonal musicians Dutch music theorists Delft University of Technology alumni Leiden University alumni People from Bogor Musicians from West Java Members of the Royal Netherlands Academy of Arts and Sciences Members of Teylers Tweede Genootschap 20th-century musicologists Dutch people of the Dutch East Indies

Life and work

Musical instruments

See also

References and notes

External links