Fokker made several contributions to special relativity, and some less well-known contributions to general relativity, particularly in the area of geodetic precession, the phenomena of precession of a freely falling gyroscope in a gravitational field.[4]
Fokker began to study music theory during the Second World War, when the University of Leiden was closed; partly this was due to a desire to convince the Nazis he would be of no use to the war effort, and partly it was a response to reading the work of Christiaan Huygens on the 31 equal temperament.
"Fokker and Coster both knew that university positions were virtually unavailable for foreigners. Laboratory space was not a problem, however, either in Groningen or Haarlem. 'Perhaps we can tap colleagues for regular contributions,' Coster suggested. Fokker set a goal of f.20,000, enough to support Meitner for five years, and immediately began contacting colleagues for advice and donations."
They were unsuccessful in obtaining funding, but Fokker succeeded in getting official permission for Meitner to leave, although he was unable to telegraph that to her due to secrecy. She escaped barely in time to evade arrest.[5]
The year 1942 consequently marked a turning point in his life; after then he wrote many pieces in 31-equal, which are notable for using the 7th harmonic 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.
He died on 24 September 1972, at the age of 85, in Beekbergen near Apeldoorn.
Musical instruments
Schematic representation of Fokker's microtonal keyboard for a 31EDO pipe organ (Fokker organ) with two manuals and pedal, built by him.
Fokker designed and had built a number of keyboard instruments capable of playing microtonal scales via a generalized keyboard. 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 and it moved to the Bamzaal in Muziekgebouw aan 't IJ. Regularly concerts take place on this instrument in the Bamzaal.
Hendrik Antoon Lorentz was a Dutch theoretical physicist who shared the 1902 Nobel Prize in Physics with Pieter Zeeman for his theoretical explanation of the Zeeman effect. He derived the Lorentz transformation of the special theory of relativity, as well as the Lorentz force, which describes the combined electric and magnetic forces acting on a charged particle in an electromagnetic field. Lorentz was also responsible for the Lorentz oscillator model, a classical model used to describe the anomalous dispersion observed in dielectric materials when the driving frequency of the electric field was near the resonant frequency of the material, resulting in abnormal refractive indices.
Pieter Zeeman was a Dutch physicist who shared the 1902 Nobel Prize in Physics with Hendrik Lorentz for his discovery of the Zeeman effect.
Willem de Sitter was a Dutch mathematician, physicist, and astronomer. The De Sitter universe is a cosmological model named after him.
Teylers Museum is an art, 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 museum is the neoclassical Oval Room (1784), which was built behind the house of Pieter Teyler van der Hulst (1702–1778), the so-called Fundatiehuis. Pieter Teyler was a wealthy cloth merchant and banker of Scottish descent, who bequeathed his fortune for the advancement of religion, art, and science. He was a Mennonite and follower of the Scottish Enlightenment.
Hendrik Anthony "Hans" Kramers was a Dutch physicist who worked with Niels Bohr to understand how electromagnetic waves interact with matter and made important contributions to quantum mechanics and statistical physics.
Dirk Coster was a Dutch physicist. He was a professor of physics and meteorology at the University of Groningen.
Wander Johannes de Haas was a Dutch physicist and mathematician. He is best known for the Shubnikov–de Haas effect, the De Haas–Van Alphen effect and the Einstein–de Haas effect.
In music, 31 equal temperament, 31 ET, which can also be abbreviated 31 TET or 31 EDO, also known as tricesimoprimal, is the tempered scale derived by dividing the octave into 31 equally-proportioned steps. Each step represents a frequency ratio of 31√2 , or 38.71 cents.
Petrus Leonardus Rijke was a Dutch physicist, and a professor in experimental physics at the University of Leiden. Rijke spent his scientific career exploring the physics of electricity, and is known for the Rijke tube. On 1 July 1852 he married Johanna Hamaker. They had 6 sons and 6 daughters.
Jacob Gijsbertus Samuël van Breda was a Dutch biologist and geologist.
Volkert Simon Maarten van der Willigen, sometimes referred to as Volcardus Simon Martinus van der Willigen, was a Dutch mathematician, physicist and professor.
Abraham de Vries was a Dutch Mennonite minister, author on literature and member of several societies, mainly literary ones.
Johannes Enschedé was a Dutch printer, owner of Royal Joh. Enschedé and collector.
Adriaan Justus Enschedé was a Haarlem archivist, collector, owner of the Joh. Enschedé printing company, philanthropist and a member of Teylers Tweede Genootschap.
Adriaan van der Willigen Pz. was a 19th-century medical doctor and historian from the Northern Netherlands.
Johannes Enschedé III was a Haarlem newspaper editor and printer.
The Huygens-Fokker Foundation is a "centre for microtonal music" founded on February 15, 1960, housed in the Muziekgebouw aan 't IJ, and named for Christiaan Huygens and Adriaan Fokker. The Foundation's library possesses a large archive of correspondence, scores, books, and other publications. The Foundation presents frequent concerts presenting contemporary, early, popular, and improvised microtonal music. They maintain contact with other organizations dedicated to microtonality including Tonalsoft, the Harry Partch Institute, the Logos Foundation, and individuals such as Kyle Gann. They published the journal Thirty-One and presented MicroFest Amsterdam 2011. They house the 31-tone Fokker organ with new MIDI-connections in the BAM Hall. The current director is Sander Germanus.
Cornelis Jacobus (Cor) Gorter was a Dutch experimental and theoretical physicist. Among other work, he discovered paramagnetic relaxation and was a pioneer in low temperature physics.
Jacob Leonard de Bruyn Kops, was a Dutch liberal economist, politician, and professor in political economy and administrative law at the Delft University of Technology.
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