Petrus Josephus Wilhelmus Debije (March 24 1884 – November 2 1966) was a Dutch physical chemist. He later legally changed his name to Peter Joseph William Debye.

Peter "Pie" Debye was born in Maastricht, The Netherlands, and, after attending local schools in Maastricht, went to the Aachen University of Technology, Germany, only 30 km from Maastricht, in 1901. He studied mathematics and classical physics, and, in 1905, received a degree in electrical engineering. In 1907, he published his first paper, a mathematically elegant solution of a problem involving eddy currents. At Aachen, he studied under the theoretical physicist Arnold Sommerfeld, who later claimed that his most important discovery was Peter Debye.

In 1906, Sommerfeld received an appointment at Munich, Germany, and took Debye with him as his assistant. He got his Ph.D. with a dissertation on radiation pressure in 1908. In 1910, he derived the Planck radiation formula using a method which Max Planck agreed was simpler than his own method.

In 1911, when Albert Einstein took an appointment as a professor at Prague, Czechoslovakia, Debye took his old professorship at Zürich, Switzerland. This was followed by moves to Utrecht in 1912, Göttingen in 1913, back to Zürich in 1920, to Leipzig in 1927, and to Berlin in 1934, where he became director of the Physics section of the Kaiser Wilhelm Institute, saw to the construction of new laboratories, and developed it into what is the now-world-regarded Max Planck Institute. He was awarded the Lorentz Medal in 1935. From 1937 to 1939 he was the president of the Deutsche Physikalische Gesellschaft.

In 1913, he married Mathilde Alberer. They had a son and a daughter; their son, Peter P. Debye, became a physicist and collaborated with Debye in some of his researches.

* children = Peter Paul Rupprecht (b. 1916), Mathilde Maria (b. 1921)

*His first major scientific contribution was the application of the concept of dipole moment to the charge distribution in asymmetric molecules in 1912, developing equations relating dipole moments to temperature, dielectric constant, debye relaxation, etc. In consequence, molecular dipole moments are measured in debyes, a unit named in his honor. *Also in 1912, he extended Albert Einstein's theory of specific heat to lower temperatures by including contributions from low-frequency phonons. See Debye model. *in 1913, he extended Niels Bohr's theory of atomic structure, introducing elliptical orbits, a concept also introduced by Arnold Sommerfeld. *In 1914-1915, he calculated the effect of temperature on X-ray diffraction patterns of crystalline solids with Paul Scherrer. (The "Debye-Waller" factor) *In 1923, with his assistant Erich Hückel, he developed an improvement of Svante Arrhenius' theory of electrical conductivity in electrolytic solutions. Although an improvement was made to the Debye-Hückel equation in 1926 by Lars Onsager, the theory is still regarded as a major forward step in our understanding of electrolytic solutions. *Also in 1923, he developed a theory to explain the Compton effect, the shifting of the frequency of X-rays when they interact with electrons. *In 1930, he obtained the Rumford Medal for his work relating to specific heats and X-ray spectroscopy. *In 1936, Debye was awarded the Nobel Prize in Chemistry (entry at nobelprize.org) "for his contributions to the study of molecular structure," primarily referring to his work on dipole moments and X-ray diffraction.

From 1934 to 1939 Debye was director of the physics section of the prestigious Kaiser Wilhelm Institute in Berlin. These were years that Hitler ruled over Germany and, from 1938 onward, also over Austria.

In 1939 Debye was offered a chance to give a series of lectures at Cornell University in Ithaca, New York and he traveled to the United States of America. After leaving Germany in early 1940, Peter Debye remained at Cornell University until his death in 1966.

In January 2006, a book (in Dutch) appeared in The Netherlands, written by Sybe Rispens, entitled Einstein in the Netherlands. One chapter of this book treats the relationship between Einstein and Debye. Rispens discovered documents that, as he believed, were new and proved that, during his directorship of the KWI, Debye was actively involved in cleansing German science institutions from Jewish and other "non-Aryan elements". Rispens records that on December 9 1938, Debye wrote in his capacity as chairman of the Deutsche Physikalische Gesellschaft (DPG) to all the members of the DPG:

In light of the current situation, membership by German Jews as stipulated by the Nuremberg laws, of the Deutsche Physikalische Gesellschaft cannot be continued. According to the wishes of the board, I ask of all members to whom these definitions apply to report to me their resignation. Heil Hitler!

Many biographies published before Rispens' work, state that Debye moved to the US because he refused to accept German citizenship forced on to him by the Nazis. He planned his departure from Germany during a visit with his mother in Maastricht in late 1939, boarded a ship in Genoa in January 1940 and arrived in New York in early February 1940. He immediately sought a permanent position in the US and accepted such an offer from Cornell in June 1940. That month, he crossed the US border into Canada and returned within days on an immigration visa. He was able to get his wife out of Germany and to the US by December 1940. Although his son already was in the US before he departed, Peter Debye's 19 year old daughter and sister-in-law did not leave. They lived in his official residence in Berlin and had them supported by his official Berlin wages (he carefully maintained an official leave of absence for this purpose).

Furthermore, an article appeared 18 years before Rispens' book about Debye's letter. It describes the missive in more detail and presents a very favorable picture of Peter Debye in his efforts to resist the Nazi activists. Moreover, this article points out that Max von Laue, well known for his anti-Nazi views, gave his approval to the letter from the DPG chairman.

Further, Rispens alleges that Albert Einstein in the first half of 1940 actively tried to prevent Debye from being appointed in the United States at Cornell University. Allegedly Einstein wrote to his American colleagues: "I know from a reliable source that Peter Debye is still in close contact with the German (Nazi) leaders" and, according to Rispens, Einstein called upon his colleagues to do "what they consider their duty as American citizens". To underpin this, Rispens refers to a well-known letter from Debye to Einstein and Einstein's response to this letter. Van Ginkel investigated 1940 FBI reports on this matter and traced the "reliable source" to a single letter directed to Einstein and written by somebody whose name is lost. This somebody was not known personally to Einstein and, according to Einstein, probably did not know Debye personally either. Moreover, this accusative letter did not reach Einstein directly but was intercepted by British censors who showed it to Einstein. Einstein sent the British agent with the letter to Cornell and the Cornell authorities told Debye about the affair. Thereupon Debye wrote his well-known 1940 letter to Einstein to which Einstein answered. The latter two letters can be found in the published Einstein correspondence.

Rispens alleges that Debye sent a telegram to Berlin on 23 June 1941 informing his previous employers that he was able and willing to resume his responsibilities at the Kaiser Wilhelm Institut, presumably in order to maintain his leave of absence and keep the Berlin house and wages available for the support of his daughter. A copy of this telegram has not been recovered thus far. In summer 1941, Debye filed his intent to become a US citizen and quickly was recruited in the US to participate in the Allied War research.

It has been well documented in many biographies and also in Rispens' book that Peter Debye and Dutch colleagues helped his Jewish colleague Lise Meitner in 1938-1939 (at great risk to himself and his family) cross the Dutch-German border to escape Nazi prosecution and eventually landing a position in Sweden.

Debye's son, Peter P. Debye, interviewed in 2006 at age 89 recollects that his father was completely apolitical and that in the privacy of their home politics were never discussed. According to his son Debye just wanted to do his job at the Kaiser Wilhelm Institute and that as long as the Nazis did not bother him he was able to do so. He recalls that his mother urged him (the son) to stay in the US in the event war would break out. He had come to the US on a planned 2-month vacation during the Summer of 1939 and never returned to Germany because war did, indeed, break out.

The accusations of Rispens were considered harmful enough by the Board of Directors of the University of Utrecht to announce on February 16 2006 a name change for the Debye Institute. This was done after consultation with NIOD.

In an opinion article published on the Debye Institute website, Dr. Gijs van Ginkel, until April 2007 Senior Managing Director of the VM Debye Instituut in Utrecht deplored this decision. In his article he cites scholars who point out that the DPG was able to retain their threatened staff as long as could be expected under increasing pressure from the Nazis. He also puts forward the important argument that when Debye in 1950 received the Max Planck medal of the DPG, nobody objected, not even the known opponent of the national socialists Max von Laue, who would be in a position to object. Also Einstein, with his enormous prestige, was still alive, as were other Jewish scientists such as Meitner and James Franck who both knew Debye intimately. None of them protested against Debye receiving the highest German scientific distinction.

The Maastricht University also announced it was reconsidering its position on the Peter Debye Prijs voor natuurwetenschappelijk onderzoek (Peter Debye Prize for scientific research)

In a reply on the DPG website, Dieter Hoffmann and Mark Walker also conclude that Debye was not a Nazi activist. They remark that the aforementioned Max von Laue was also required and obliged (as a civil servant) to sign letters with Heil Hitler. They also state that the DPG was one of the last scientific societies to purge the Jewish members and only very reluctantly. They quote the response of the Reich University Teachers League (a National Socialist organization) to the Debye letter:

Obviously the German Physical Society is still very backward and still clings tightly to their dear Jews. It is in fact remarkable that only "because of circumstances beyond our control" the membership of Jews can no longer be maintained In May 2006, the Dutch Nobel Prize winner Martinus Veltman who had written the foreword to the Rispen book, renounced the book's description of Peter Debye, withdrew his foreword, and asked the Board of Directors of Utrecht University to rescind their decision to rename the Debye Institute.

Various historical investigations, both in The Netherlands and in the US, have been carried out subsequent to the actions of the University of Maastricht. The earliest of these investigations, carried out by the Cornell University's department of Chemistry and Chemical Biology is now complete. The report of the Cornell investigation, released on 31 May 2006, states that:

Based on the information to-date, we have not found evidence supporting the accusations that Debye was a Nazi sympathizer or collaborator or that he held anti-Semitic views. It is important that this be stated clearly since these are the most serious allegations.

It goes on to declare:

Thus, based on the information, evidence and historical record known to date, we believe that any action that dissociates Debye's name from the Department of Chemistry and Chemical Biology at Cornell is unwarranted.

In June 2006, it was reported that the scientific director of the (formerly) Debye Institute had been reprimanded by the Board of Directors of the University of Utrecht for a new publication on Debye's war years on the grounds that it is was too personally biased with respect to the institutes naming dispute. According to the board, the book should not have been published as a Debye Institute publication but as a personal one. The book was banned by the University of Utrecht and both Directors of the (former) Debye Institute were forbidden to have any further contact with the press.

In May 2007 the universities of Utrecht and Maastricht announced that a new committee headed by Jan Terlouw will advise them regarding the name-change. An official report by the NIOD authorized by the Dutch Education Ministry is expected fall 2007 .

Debye ended up staying at Cornell, became a professor (and, for 10 years, chairman of the chemistry department, and member of Alpha Chi Sigma) there, and in 1946 became an American citizen. Unlike the European phase of his life, where Debye moved from city to city every few years, in the United States he remained at Cornell for the whole remainder of his career. He retired in 1952, but continued research until his death.

Much of his work at Cornell concerned the use of light-scattering techniques (derived from his X-ray scattering work of years earlier) to determine the size and molecular weight of polymer molecules. This started as a result of his work during World War II on synthetic rubber, but was extended to proteins and other macromolecules.

In April 1966, he suffered a heart attack, and in November of that year a second, which proved fatal. He is buried in the Pleasant Grove Cemetery (Ithaca, New York, USA).

* Debye shielding - In plasma physics, the process by which a plasma "shields" an electric charge by redistributing charged particles of the plasma around it. * Debye length - The typical distance in a plasma required for full Debye shielding. * Debye model - A model of the heat capacity of solids as a function of temperature * Debye - a unit of electric dipole moment * Debye relaxation - The dielectric relaxation response of an ideal, noninteracting population of dipoles to an alternating external electric field. * Debye sheath - The non-neutral layer, several Debye lengths thick, where a plasma contacts a material surface. * Debye-Hückel equation - A method of calculating activity coefficients * Debye function - A function used in the calculation of heat capacity. * Debye-Waller factor - A measure of disorder in a crystal lattice. * 30852 Debye - A minor planet (originally named 1991 TR6). * Lorenz-Mie-Debye theory Theory of light scattering by a spherical particle.

*Debye Biography - Institute of Chemistry, Hebrew University *Debye Biography - Nobel Prize *Debye Biography - NNDB *Debye Biography - IUCR * Museum Boerhaave Negen Nederlandse Nobelprijswinnaars * Link to DPG * Link to Kennislink * Link to Dr. Rispens research * Website Debye institute