Franz Ernst Neumann
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Franz Ernst Neumann (11 September 1798 – 23 May 1895) was a German
mineralogist Mineralogy is a subject of geology specializing in the scientific study of the chemistry, crystal structure, and physical (including optical mineralogy, optical) properties of minerals and mineralized artifact (archaeology), artifacts. Specific s ...
and
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 devised the first formulas to calculate
inductance Inductance is the tendency of an electrical conductor to oppose a change in the electric current flowing through it. The electric current produces a magnetic field around the conductor. The magnetic field strength depends on the magnitude of the ...
. He also formulated Neumann's law for molecular heat. In electromagnetism, he is credited for introducing the
magnetic vector potential In classical electromagnetism, magnetic vector potential (often denoted A) is the vector quantity defined so that its curl is equal to the magnetic field, B: \nabla \times \mathbf = \mathbf. Together with the electric potential ''φ'', the ma ...
.


Biography


Early life

Franz Ernst Neumann was born in Joachimsthal,
Margraviate of Brandenburg The Margraviate of Brandenburg () was a major principality of the Holy Roman Empire from 1157 to 1806 that, having electoral status although being quite poor, grew rapidly in importance after inheriting the Duchy of Prussia in 1618 and then came ...
(near
Berlin Berlin ( ; ) is the Capital of Germany, capital and largest city of Germany, by both area and List of cities in Germany by population, population. With 3.7 million inhabitants, it has the List of cities in the European Union by population withi ...
), the son of Ernst Neumann, a farmer who became a state agent. His mother was a Countess who was not allowed to marry Ernst, and Neumann did not meet her mother until he was 10 years old. Neumann attended a Gymnasium in Berlin, where he excelled in mathematics. However his studies were interrupted by the war with France. In 1815 he paused his education at Berlin to serve as a volunteer in the
Hundred Days The Hundred Days ( ), also known as the War of the Seventh Coalition (), marked the period between Napoleon's return from eleven months of exile on the island of Elba to Paris on20 March 1815 and the second restoration of King Louis XVIII o ...
against
Napoleon Napoleon Bonaparte (born Napoleone di Buonaparte; 15 August 1769 – 5 May 1821), later known by his regnal name Napoleon I, was a French general and statesman who rose to prominence during the French Revolution and led Military career ...
, and was wounded in the
Battle of Ligny The Battle of Ligny, in which French troops of the under the command of Napoleon I defeated part of a Prussian army under Field Marshal Blücher, was fought on 16 June 1815 near Ligny in what is now Belgium. The result was a tactical victor ...
. He later returned to finish his studies in Berlin. Subsequently, he enrolled at Berlin University in 1818 as a student of
theology Theology is the study of religious belief from a Religion, religious perspective, with a focus on the nature of divinity. It is taught as an Discipline (academia), academic discipline, typically in universities and seminaries. It occupies itse ...
, but soon turned to scientific subjects.


Professional career

Neumann's early work was primarily centered around
crystallography Crystallography is the branch of science devoted to the study of molecular and crystalline structure and properties. The word ''crystallography'' is derived from the Ancient Greek word (; "clear ice, rock-crystal"), and (; "to write"). In J ...
. His researched gained him recognition, leading to his appointment as
Privatdozent ''Privatdozent'' (for men) or ''Privatdozentin'' (for women), abbreviated PD, P.D. or Priv.-Doz., is an academic title conferred at some European universities, especially in German-speaking countries, to someone who holds certain formal qualifi ...
at the
University of Königsberg The University of Königsberg () was the university of Königsberg in Duchy of Prussia, which was a fief of Poland. It was founded in 1544 as the world's second Protestant Reformation, Protestant academy (after the University of Marburg) by Duke A ...
. In 1828 he became extraordinary, and in 1829 ordinary, professor of
mineralogy Mineralogy is a subject of geology specializing in the scientific study of the chemistry, crystal structure, and physical (including optical mineralogy, optical) properties of minerals and mineralized artifact (archaeology), artifacts. Specific s ...
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 ...
. His 1831 study on the
specific heat In thermodynamics, the specific heat capacity (symbol ) of a substance is the amount of heat that must be added to one unit of mass of the substance in order to cause an increase of one unit in temperature. It is also referred to as massic heat ...
s of compounds included what is now known as Neumann's law: the molecular heat of a compound is equal to the sum of the atomic heats of its constituents. Devoting himself next to optics, he produced memoirs which earned him a high place among early searchers of a true dynamical theory of light. In 1832, by the aid of a particular hypothesis as to the constitution of the ether, he reached by a rigorous dynamical calculation results agreeing with those obtained by
Augustin Louis Cauchy Baron Augustin-Louis Cauchy ( , , ; ; 21 August 1789 – 23 May 1857) was a French mathematician, engineer, and physicist. He was one of the first to rigorously state and prove the key theorems of calculus (thereby creating real a ...
, and succeeded in deducing laws of double refraction closely resembling those of
Augustin-Jean Fresnel Augustin-Jean Fresnel (10 May 1788 – 14 July 1827) was a French civil engineer and physicist whose research in optics led to the almost unanimous acceptance of the wave theory of light, excluding any remnant of Isaac Newton, Newton's c ...
. In studying double refraction, with his deduction of the elastic constants (on which the optical properties depend) Neumann employed the assumption that the symmetry of the elastic behavior of a crystal was equal to that of its form. In other words, he assumed that the magnitudes of the components of a physical property in symmetric positions are equivalent. This assumption substantially reduced the number of independent constants and greatly simplified the elastic equations. However, four decades passed before Neumann elaborated his application of symmetry in a course on elasticity in 1873. This principle was later formalized by his student
Woldemar Voigt Woldemar Voigt (; 2 September 1850 – 13 December 1919) was a German mathematician and physicist. Biography Voigt was born in Leipzig, and died in Göttingen. He was a student of Franz Ernst Neumann. Voigt taught at the Georg August Universi ...
(1850–1918) in 1885: "''the symmetry of the physical phenomenon is at least as high as the crystallographic symmetry''", which became a fundamental postulate of crystal physics known as Neumann’s principle. In 1900, Voigt attributed this principle to Neumann's 1832 paper even though, at most, all that was present in that work was an implicit assumption that the symmetry of the phenomenon was equal to that of the crystal. Bernhard Minnigerode (1837–1896), another student of Neumann, first expressed this relation in written form in 1887 in the journal ''Neues Jahrb. Mineral Geol. Paleontol''. (Vol. 5, p. 145). In 1845, Neumann introduced the
magnetic vector potential In classical electromagnetism, magnetic vector potential (often denoted A) is the vector quantity defined so that its curl is equal to the magnetic field, B: \nabla \times \mathbf = \mathbf. Together with the electric potential ''φ'', the ma ...
to discuss
Ampère's circuital law In classical electromagnetism, Ampère's circuital law, often simply called Ampère's law, and sometimes Oersted's law, relates the circulation of a magnetic field around a closed loop to the electric current passing through the loop. James ...
. Later, Neumann attacked the problem of giving mathematical expression to the conditions holding for a surface separating two crystalline media, and worked out from theory the laws of double refraction in strained crystalline bodies. He also made important contributions to the mathematical theory of electrodynamics, and in papers published in 1845 and 1847 established mathematically the laws of the induction of electric currents. His last publication, which appeared in 1878, was on
spherical harmonics In mathematics and physical science, spherical harmonics are special functions defined on the surface of a sphere. They are often employed in solving partial differential equations in many scientific fields. The table of spherical harmonics co ...
(''Beiträge zur Theorie der Kugelfunctionen''). With the mathematician
Carl Gustav Jacobi Carl Gustav Jacob Jacobi (; ; 10 December 1804 – 18 February 1851) was a German mathematician who made fundamental contributions to elliptic functions, dynamics, differential equations, determinants and number theory. Biography Jacobi was ...
, he founded in 1834 the ''Mathematisch-physikalisches Seminar'' which operated in two sections for mathematics and for
mathematical physics Mathematical physics is the development of mathematics, mathematical methods for application to problems in physics. The ''Journal of Mathematical Physics'' defines the field as "the application of mathematics to problems in physics and the de ...
. Not every student took both sections. In his section on mathematical physics Neumann taught mathematical methods as well as the techniques of an exact experimental physics grounded in the type of precision measurement perfected by his astronomer colleague
Friedrich Wilhelm Bessel Friedrich Wilhelm Bessel (; 22 July 1784 – 17 March 1846) was a German astronomer, mathematician, physicist, and geodesist. He was the first astronomer who determined reliable values for the distance from the Sun to another star by the method ...
. The objective of his seminar exercises was to perfect one's ability to practice an exact experimental physics through the control of both constant and random experimental errors. Only a few students actually produced original research in the seminar; a notable exception was
Gustav Robert Kirchhoff Gustav Robert Kirchhoff (; 12 March 1824 – 17 October 1887) was a German chemist, mathematician, physicist, and spectroscopist who contributed to the fundamental understanding of electrical circuits, spectroscopy and the emission of black-body ...
who formulated Kirchhoff's laws on the basis of his seminar research. This seminar was the model for many others of the same type established after 1834, including Kirchhoff's own at
Heidelberg University Heidelberg University, officially the Ruprecht Karl University of Heidelberg (; ), is a public research university in Heidelberg, Baden-Württemberg, Germany. Founded in 1386 on instruction of Pope Urban VI, Heidelberg is Germany's oldest unive ...
. Neumann retired from his professorship in 1876, and died at
Königsberg Königsberg (; ; ; ; ; ; , ) is the historic Germany, German and Prussian name of the city now called Kaliningrad, Russia. The city was founded in 1255 on the site of the small Old Prussians, Old Prussian settlement ''Twangste'' by the Teuton ...
(now
Kaliningrad Kaliningrad,. known as Königsberg; ; . until 1946, is the largest city and administrative centre of Kaliningrad Oblast, an Enclave and exclave, exclave of Russia between Lithuania and Poland ( west of the bulk of Russia), located on the Prego ...
,
Russia Russia, or the Russian Federation, is a country spanning Eastern Europe and North Asia. It is the list of countries and dependencies by area, largest country in the world, and extends across Time in Russia, eleven time zones, sharing Borders ...
) in 1895 at the age of 96.


Children

Neumann had four children with his wife Luise Florentine Hagen (born 1800): Carl Gottfried Neumann (1832–1925), Franz Ernst Christian Neumann (1834–1818), (1835-1910), and Luise Neumann (1837-1934). His son Carl, became a mathematician and physicist; his younger son, Ernst became professor of medicine in Königsberg.


Works


Beiträge zur Krystallonomie
(Mittler, Berlin, 1823)
Beiträge zur Theorie der Kugelfunctionen
(B. G. Teubner, Leipzig, 1878) * * * *
Franz Neumanns Gesammelte werke (2 vols.)
(B. C. Teubner, Leipzig, 1906–1928)


See also

* Chemical crystallography before X-rays * Faraday's law of induction * Plane of vibration *
International System of Electrical and Magnetic Units The International System of Electrical and Magnetic Units is an obsolete system of units used for measuring electrical and magnetic quantities. It was proposed as a system of practical international units (e.g., the international ampere, the interna ...
*
Physical crystallography before X-rays Physical crystallography before X-rays describes how physical crystallography developed as a science up to the discovery of X-rays by Wilhelm Conrad Röntgen in 1895. In the period before X-rays, crystallography can be divided into three broad are ...


Notes


References

* * Olesko, Kathryn M. ''Physics as a Calling: Discipline and Practice in the Koenigsberg Seminar for Physics''. Ithaca, NY & London: Cornell University Press, 1991.


External links

* *
Primary sources on Neumann
{{DEFAULTSORT:Neumann, Franz Ernst 1798 births 1895 deaths People from Barnim People from the Margraviate of Brandenburg 19th-century German mathematicians 19th-century German physicists German mineralogists Humboldt University of Berlin alumni Academic staff of the University of Königsberg Foreign members of the Royal Society Members of the Prussian Academy of Sciences Members of the French Academy of Sciences German military personnel of the Napoleonic Wars Recipients of the Pour le Mérite (civil class) Recipients of the Copley Medal Scientists from the Kingdom of Prussia