Hermann Günther Grassmann (, ; 15 April 1809 – 26 September 1877) was a German
polymath
A polymath or polyhistor is an individual whose knowledge spans many different subjects, known to draw on complex bodies of knowledge to solve specific problems. Polymaths often prefer a specific context in which to explain their knowledge, ...
known in his day as a
linguist
Linguistics is the scientific study of language. The areas of linguistic analysis are syntax (rules governing the structure of sentences), semantics (meaning), Morphology (linguistics), morphology (structure of words), phonetics (speech sounds ...
and now also as a
mathematician
A mathematician is someone who uses an extensive knowledge of mathematics in their work, typically to solve mathematical problems. Mathematicians are concerned with numbers, data, quantity, mathematical structure, structure, space, Mathematica ...
. He was also a
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 ...
, general scholar, and publisher. His mathematical work was little noted until he was in his sixties. His work preceded and exceeded the concept which is now known as a
vector space
In mathematics and physics, a vector space (also called a linear space) is a set (mathematics), set whose elements, often called vector (mathematics and physics), ''vectors'', can be added together and multiplied ("scaled") by numbers called sc ...
. He introduced the
Grassmannian
In mathematics, the Grassmannian \mathbf_k(V) (named in honour of Hermann Grassmann) is a differentiable manifold that parameterizes the set of all k-dimension (vector space), dimensional linear subspaces of an n-dimensional vector space V over a ...
, the space which parameterizes all ''k''-dimensional linear subspaces of an ''n''-dimensional
vector space
In mathematics and physics, a vector space (also called a linear space) is a set (mathematics), set whose elements, often called vector (mathematics and physics), ''vectors'', can be added together and multiplied ("scaled") by numbers called sc ...
''V''. In linguistics he helped free language history and structure from each other.
Biography
Hermann Grassmann was the third of 12 children of Justus Günter Grassmann, an
ordained
Ordination is the process by which individuals are Consecration in Christianity, consecrated, that is, set apart and elevated from the laity class to the clergy, who are thus then authorized (usually by the religious denomination, denominationa ...
minister who taught mathematics and physics at the
Stettin
Szczecin ( , , ; ; ; or ) is the capital and largest city of the West Pomeranian Voivodeship in northwestern Poland. Located near the Baltic Sea and the German border, it is a major seaport, the largest city of northwestern Poland, and se ...
Gymnasium, where Hermann was educated.
Grassmann was an undistinguished student until he obtained a high mark on the examinations for admission to
Prussia
Prussia (; ; Old Prussian: ''Prūsija'') was a Germans, German state centred on the North European Plain that originated from the 1525 secularization of the Prussia (region), Prussian part of the State of the Teutonic Order. For centuries, ...
n universities. Beginning in 1827, he studied theology at the
University of Berlin
The Humboldt University of Berlin (, abbreviated HU Berlin) is a public research university in the central borough of Mitte in Berlin, Germany.
The university was established by Frederick William III on the initiative of Wilhelm von Humbol ...
, also taking classes in classical languages, philosophy, and literature. He does not appear to have taken courses in mathematics or
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 ...
.
Although lacking university training in mathematics, it was the field that most interested him when he returned to Stettin in 1830 after completing his studies in Berlin. After a year of preparation, he sat the examinations needed to teach mathematics in a gymnasium, but achieved a result good enough to allow him to teach only at the lower levels. Around this time, he made his first significant mathematical discoveries, ones that led him to the important ideas he set out in his 1844 paper ''Die lineale Ausdehnungslehre, ein neuer Zweig der Mathematik'', here referred to as A1, later revised in 1862 as ''Die Ausdehnungslehre: Vollständig und in strenger Form bearbeitet'', here referred to as A2.
In 1834 Grassmann began teaching mathematics at the Gewerbeschule in Berlin. A year later, he returned to Stettin to teach mathematics, physics, German, Latin, and religious studies at a new school, the Otto Schule. Over the next four years, Grassmann passed examinations enabling him to teach mathematics,
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 ...
,
chemistry
Chemistry is the scientific study of the properties and behavior of matter. It is a physical science within the natural sciences that studies the chemical elements that make up matter and chemical compound, compounds made of atoms, molecules a ...
, and
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 ...
at all secondary school levels.
In 1847, he was made an "Oberlehrer" or head teacher. In 1852, he was appointed to his late father's position at the Stettin Gymnasium, thereby acquiring the title of Professor. In 1847, he asked the Prussian Ministry of Education to be considered for a university position, whereupon that Ministry asked Ernst Kummer for his opinion of Grassmann. Kummer wrote back saying that Grassmann's 1846 prize essay (see below) contained "commendably good material expressed in a deficient form." Kummer's report ended any chance that Grassmann might obtain a university post. This episode proved the norm; time and again, leading figures of Grassmann's day failed to recognize the value of his mathematics.
Starting during the political turmoil in Germany, 1848–49, Hermann and his brother Robert published a Stettin newspaper, '' Deutsche Wochenschrift für Staat, Kirche und Volksleben'', calling for German unification under a
constitutional monarchy
Constitutional monarchy, also known as limited monarchy, parliamentary monarchy or democratic monarchy, is a form of monarchy in which the monarch exercises their authority in accordance with a constitution and is not alone in making decisions. ...
. (This eventuated in 1871.) After writing a series of articles on
constitutional law
Constitutional law is a body of law which defines the role, powers, and structure of different entities within a state, namely, the executive, the parliament or legislature, and the judiciary; as well as the basic rights of citizens and, in ...
, Hermann parted company with the newspaper, finding himself increasingly at odds with its political direction.
Grassmann had eleven children, seven of whom reached adulthood. A son, Hermann Ernst Grassmann, became a professor of mathematics at the University of Giessen.
Mathematician
One of the many examinations for which Grassmann sat required that he submit an essay on the theory of the tides. In 1840, he did so, taking the basic theory from Laplace's '' Traité de mécanique céleste'' and from
Lagrange
Joseph-Louis Lagrange (born Giuseppe Luigi LagrangiaMécanique analytique'', but expositing this theory making use of the
vector
Vector most often refers to:
* Euclidean vector, a quantity with a magnitude and a direction
* Disease vector, an agent that carries and transmits an infectious pathogen into another living organism
Vector may also refer to:
Mathematics a ...
methods he had been mulling over since 1832. This essay, first published in the ''Collected Works'' of 1894–1911, contains the first known appearance of what is now called
linear algebra
Linear algebra is the branch of mathematics concerning linear equations such as
:a_1x_1+\cdots +a_nx_n=b,
linear maps such as
:(x_1, \ldots, x_n) \mapsto a_1x_1+\cdots +a_nx_n,
and their representations in vector spaces and through matrix (mathemat ...
and the notion of a
vector space
In mathematics and physics, a vector space (also called a linear space) is a set (mathematics), set whose elements, often called vector (mathematics and physics), ''vectors'', can be added together and multiplied ("scaled") by numbers called sc ...
. He went on to develop those methods in his ''Die lineale Ausdehnungslehre, ein neuer Zweig der Mathematik'' (A1) and its later revision ''Die Ausdehnungslehre: Vollständig und in strenger Form bearbeitet'' (A2).
In 1844, Grassmann published his masterpiece (A1) commonly referred to as the ''Ausdehnungslehre'', which translates as "theory of extension" or "theory of extensive magnitudes". Since A1 proposed a new foundation for all of mathematics, the work began with quite general definitions of a philosophical nature. Grassmann then showed that once
geometry
Geometry (; ) is a branch of mathematics concerned with properties of space such as the distance, shape, size, and relative position of figures. Geometry is, along with arithmetic, one of the oldest branches of mathematics. A mathematician w ...
is put into the algebraic form he advocated, the number three has no privileged role as the number of spatial
dimension
In physics and mathematics, the dimension of a mathematical space (or object) is informally defined as the minimum number of coordinates needed to specify any point within it. Thus, a line has a dimension of one (1D) because only one coo ...
s; the number of possible dimensions is in fact unbounded.
Fearnley-Sander describes Grassmann's foundation of linear algebra as follows:
Following an idea of Grassmann's father, A1 also defined the
exterior product
In mathematics, specifically in topology,
the interior of a subset of a topological space is the union of all subsets of that are open in .
A point that is in the interior of is an interior point of .
The interior of is the complement of ...
, also called "combinatorial product" (in German: ''kombinatorisches Produkt'' or ''äußeres Produkt'' “outer product”), the key operation of an algebra now called
exterior algebra
In mathematics, the exterior algebra or Grassmann algebra of a vector space V is an associative algebra that contains V, which has a product, called exterior product or wedge product and denoted with \wedge, such that v\wedge v=0 for every vector ...
. (One should keep in mind that in Grassmann's day, the only
axiom
An axiom, postulate, or assumption is a statement that is taken to be true, to serve as a premise or starting point for further reasoning and arguments. The word comes from the Ancient Greek word (), meaning 'that which is thought worthy or ...
atic theory was
Euclidean geometry
Euclidean geometry is a mathematical system attributed to ancient Greek mathematics, Greek mathematician Euclid, which he described in his textbook on geometry, ''Euclid's Elements, Elements''. Euclid's approach consists in assuming a small set ...
, and the general notion of an
abstract algebra
In mathematics, more specifically algebra, abstract algebra or modern algebra is the study of algebraic structures, which are set (mathematics), sets with specific operation (mathematics), operations acting on their elements. Algebraic structur ...
had yet to be defined.) In 1878,
William Kingdon Clifford
William Kingdon Clifford (4 May 18453 March 1879) was a British mathematician and philosopher. Building on the work of Hermann Grassmann, he introduced what is now termed geometric algebra, a special case of the Clifford algebra named in his ...
joined this exterior algebra to
William Rowan Hamilton
Sir William Rowan Hamilton (4 August 1805 – 2 September 1865) was an Irish astronomer, mathematician, and physicist who made numerous major contributions to abstract algebra, classical mechanics, and optics. His theoretical works and mathema ...
's quaternions by replacing Grassmann's rule ''epep'' = 0 by the rule ''epep'' = 1. (For quaternions, we have the rule ''i''2 = ''j''2 = ''k''2 = −1.) For more details, see
Exterior algebra
In mathematics, the exterior algebra or Grassmann algebra of a vector space V is an associative algebra that contains V, which has a product, called exterior product or wedge product and denoted with \wedge, such that v\wedge v=0 for every vector ...
.
A1 was a revolutionary text, too far ahead of its time to be appreciated. When Grassmann submitted it to apply for a professorship in 1847, the ministry asked Ernst Kummer for a report. Kummer assured that there were good ideas in it, but found the exposition deficient and advised against giving Grassmann a university position. Over the next 10-odd years, Grassmann wrote a variety of work applying his theory of extension, including his 1845 ''Neue Theorie der Elektrodynamik'' and several papers on
algebraic curve
In mathematics, an affine algebraic plane curve is the zero set of a polynomial in two variables. A projective algebraic plane curve is the zero set in a projective plane of a homogeneous polynomial in three variables. An affine algebraic plane cu ...
s and surfaces, in the hope that these applications would lead others to take his theory seriously.
In 1846, Möbius invited Grassmann to enter a competition to solve a problem first proposed by Leibniz: to devise a geometric calculus devoid of coordinates and metric properties (what Leibniz termed ''analysis situs''). Grassmann's ''Geometrische Analyse geknüpft an die von Leibniz erfundene geometrische Charakteristik'', was the winning entry (also the only entry). Möbius, as one of the judges, criticized the way Grassmann introduced abstract notions without giving the reader any intuition as to why those notions were of value.
In 1853, Grassmann published a theory of how colors mix; his theory's four color laws are still taught, as Grassmann's laws. Grassmann's work on this subject was inconsistent with that of Helmholtz. Grassmann also wrote on
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 ...
,
electromagnetism
In physics, electromagnetism is an interaction that occurs between particles with electric charge via electromagnetic fields. The electromagnetic force is one of the four fundamental forces of nature. It is the dominant force in the interacti ...
, and
mechanics
Mechanics () is the area of physics concerned with the relationships between force, matter, and motion among Physical object, physical objects. Forces applied to objects may result in Displacement (vector), displacements, which are changes of ...
.
In 1861, Grassmann laid the groundwork for Peano's axiomatization of arithmetic in his ''Lehrbuch der Arithmetik''. In 1862, Grassmann published a thoroughly rewritten second edition of A1, hoping to earn belated recognition for his theory of extension, and containing the definitive exposition of his
linear algebra
Linear algebra is the branch of mathematics concerning linear equations such as
:a_1x_1+\cdots +a_nx_n=b,
linear maps such as
:(x_1, \ldots, x_n) \mapsto a_1x_1+\cdots +a_nx_n,
and their representations in vector spaces and through matrix (mathemat ...
. The result, ''Die Ausdehnungslehre: Vollständig und in strenger Form bearbeitet'' (A2), fared no better than A1, even though A2 manner of exposition anticipates the textbooks of the 20th century.
Response
In the 1840s, mathematicians were generally unprepared to understand Grassmann's ideas. In the 1860s and 1870s various mathematicians came to ideas similar to that of Grassmann's, but Grassmann himself was not interested in mathematics anymore.
Adhémar Jean Claude Barré de Saint-Venant developed a vector calculus similar to that of Grassmann, which he published in 1845. He then entered into a dispute with Grassmann about which of the two had thought of the ideas first. Grassmann had published his results in 1844, but Saint-Venant claimed that he had first developed these ideas in 1832.
One of the first mathematicians to appreciate Grassmann's ideas during his lifetime was
Hermann Hankel
Hermann Hankel (14 February 1839 – 29 August 1873) was a German mathematician. Having worked on mathematical analysis during his career, he is best known for introducing the Hankel transform and the Hankel matrix.
Biography
Hankel was born on ...
, whose 1867 ''Theorie der complexen Zahlensysteme''.
In 1872 Victor Schlegel published the first part of his ''System der Raumlehre'', which used Grassmann's approach to derive ancient and modern results in plane geometry.
Felix Klein
Felix Christian Klein (; ; 25 April 1849 – 22 June 1925) was a German mathematician and Mathematics education, mathematics educator, known for his work in group theory, complex analysis, non-Euclidean geometry, and the associations betwe ...
wrote a negative review of Schlegel's book citing its incompleteness and lack of perspective on Grassmann. Schlegel followed in 1875 with a second part of his ''System'' according to Grassmann, this time developing higher-dimensional geometry. Meanwhile, Klein was advancing his Erlangen program, which also expanded the scope of geometry.
Comprehension of Grassmann awaited the concept of
vector space
In mathematics and physics, a vector space (also called a linear space) is a set (mathematics), set whose elements, often called vector (mathematics and physics), ''vectors'', can be added together and multiplied ("scaled") by numbers called sc ...
s, which then could express the
multilinear algebra
Multilinear algebra is the study of Function (mathematics), functions with multiple vector space, vector-valued Argument of a function, arguments, with the functions being Linear map, linear maps with respect to each argument. It involves concept ...
of his extension theory. To establish the priority of Grassmann over Hamilton, Josiah Willard Gibbs urged Grassmann's heirs to have the 1840 essay on tides published. A. N. Whitehead's first monograph, the ''Universal Algebra'' (1898), included the first systematic exposition in English of the theory of extension and the
exterior algebra
In mathematics, the exterior algebra or Grassmann algebra of a vector space V is an associative algebra that contains V, which has a product, called exterior product or wedge product and denoted with \wedge, such that v\wedge v=0 for every vector ...
. With the rise of
differential geometry
Differential geometry is a Mathematics, mathematical discipline that studies the geometry of smooth shapes and smooth spaces, otherwise known as smooth manifolds. It uses the techniques of Calculus, single variable calculus, vector calculus, lin ...
the exterior algebra was applied to
differential form
In mathematics, differential forms provide a unified approach to define integrands over curves, surfaces, solids, and higher-dimensional manifolds. The modern notion of differential forms was pioneered by Élie Cartan. It has many applications ...
s.
In 1995 Lloyd C. Kannenberg published an English translation of The Ausdehnungslehre and Other works. For an introduction to the role of Grassmann's work in contemporary
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 ...
Roger Penrose
Sir Roger Penrose (born 8 August 1931) is an English mathematician, mathematical physicist, Philosophy of science, philosopher of science and Nobel Prize in Physics, Nobel Laureate in Physics. He is Emeritus Rouse Ball Professor of Mathematics i ...
.
Linguist
Grassmann's mathematical ideas began to spread only towards the end of his life. Thirty years after the publication of A1 the publisher wrote to Grassmann: "Your book ''Die Ausdehnungslehre'' has been out of print for some time. Since your work hardly sold at all, roughly 600 copies were used in 1864 as waste paper and the remaining few odd copies have now been sold out, with the exception of the one copy in our library." Disappointed by the reception of his work in mathematical circles, Grassmann lost his contacts with mathematicians as well as his interest in geometry. In the last years of his life he turned to historical
linguistics
Linguistics is the scientific study of language. The areas of linguistic analysis are syntax (rules governing the structure of sentences), semantics (meaning), Morphology (linguistics), morphology (structure of words), phonetics (speech sounds ...
and the study of
Sanskrit
Sanskrit (; stem form ; nominal singular , ,) is a classical language belonging to the Indo-Aryan languages, Indo-Aryan branch of the Indo-European languages. It arose in northwest South Asia after its predecessor languages had Trans-cultural ...
. He wrote books on
German grammar
The grammar of the German language is quite similar to that of the other Germanic languages.
Although some features of German grammar, such as the formation of some of the verb forms, resemble those of English, German grammar differs from that o ...
, collected folk songs, and learned Sanskrit. He wrote a 2,000-page dictionary and a translation of the ''
Rigveda
The ''Rigveda'' or ''Rig Veda'' (, , from wikt:ऋच्, ऋच्, "praise" and wikt:वेद, वेद, "knowledge") is an ancient Indian Miscellany, collection of Vedic Sanskrit hymns (''sūktas''). It is one of the four sacred canoni ...
'' (more than 1,000 pages). In modern studies of the ''Rigveda'', Grassmann's work is often cited. In 1955 a third edition of his dictionary was issued.
Grassmann also noticed and presented a
phonological rule
A phonological rule is a formal way of expressing a systematic phonological or morphophonological process in linguistics. Phonological rules are commonly used in generative phonology as a notation to capture sound-related operations and computati ...
that exists in both
Sanskrit
Sanskrit (; stem form ; nominal singular , ,) is a classical language belonging to the Indo-Aryan languages, Indo-Aryan branch of the Indo-European languages. It arose in northwest South Asia after its predecessor languages had Trans-cultural ...
and Greek. In his honor, this phonological rule is known as
Grassmann's law
Grassmann's law, named after its discoverer Hermann Grassmann, is a dissimilatory phonological process in Ancient Greek and Sanskrit which states that if an Aspiration (phonetics), aspirated consonant is followed by another aspirated consonant ...
. His discovery was revolutionary for historical linguistics at the time, as it challenged the widespread notion of Sanskrit as an older predecessor to other Indo-European languages. This was a widespread assumption due to Sanskrit's more agglutinative structure, which languages like Latin and Greek were thought to have passed through to reach their more "modern" synthetic structure. However, Grassman's work proved that, in at least one phonological pattern, German was indeed "older" (i.e., less synthetic) than Sanskrit. This meant that genealogical and typological classifications of languages were at last correctly separated in linguistics, allowing significant progress for later linguists.
These philological accomplishments were honored during his lifetime. He was elected to the
American Oriental Society
The American Oriental Society is a learned society that encourages basic research in the languages and literatures of the Near East and Asia. It was chartered under the laws of Massachusetts on September 7, 1842. It is one of the oldest learned ...
and in 1876 he received an honorary doctorate from the
University of Tübingen
The University of Tübingen, officially the Eberhard Karl University of Tübingen (; ), is a public research university located in the city of Tübingen, Baden-Württemberg, Germany.
The University of Tübingen is one of eleven German Excellenc ...
American Mathematical Society
The American Mathematical Society (AMS) is an association of professional mathematicians dedicated to the interests of mathematical research and scholarship, and serves the national and international community through its publications, meetings, ...
Bra–ket notation
Bra–ket notation, also called Dirac notation, is a notation for linear algebra and linear operators on complex vector spaces together with their dual space both in the finite-dimensional and infinite-dimensional case. It is specifically de ...
Multilinear algebra
Multilinear algebra is the study of Function (mathematics), functions with multiple vector space, vector-valued Argument of a function, arguments, with the functions being Linear map, linear maps with respect to each argument. It involves concept ...