Paul Drude

Paul Karl Ludwig Drude (July 12, 1863 – July 5, 1906) was a German physicist specializing in optics. He wrote a fundamental textbook integrating optics with Maxwell's theories of electromagnetism.Drude was the son of a medical doctor in Brunswick. He attended the local Gymnasium and then went on to study at the University of Göttingen. His original ambition was to become a mathematician, and he studied mathematics, first at Göttingen and then at Freiburg and Berlin. In his sixth semester he returned to Göttingen, where he came under the influence of W. Voigt and as a result began to study theoretical physics. Drude’s dissertation, under Voigt’s direction, was a purely theoretical treatment of the equations governing the reflection and refraction of light at the boundaries of absorbing crystals.

Drude worked with Voigt at Göttingen until 1894. He then moved to Leipzig where he pursued both theoretical and practical researches on the propagation of electromagnetic waves and wireless telegraphy, as well as continuing his work on physical optics. His interest in the physical determinants of optical constants led him toward an attempt to correlate and account for the optical, electrical, thermal, and chemical properties of substances. Drude’s interest in these problems was stimulated by his own growing conviction, based on studies begun in 1888, that Maxwell’s electromagnetic theory was superior to the older mechanical view of light. This conviction led him to publish Physik des Äthers (1894), one of the first German books to base explanations of electrical and optical effects on Maxwell’s theory. By 1898 Drude had begun to consider these matters within the structure of the theory of electrons; indeed, he thereby laid the foundation for understanding such phenomena as conduction in metals, thermal conductivity, and optical properties of metals as interactions of the electrical charges of substances with their environment.In 1894 Drude married Emilie Regelsberger, the daughter of a Göttingen jurist. With the death of Wiedemann in 1889, he assumed the editorship of Annalen der Physik, the most prestigious of physics journals. In 1901, shortly after the publication of his Lehrbuch der Optik, Drude moved to Giessen where he became director of the Institute of Physics.

In Giessen, where he remained until 1905, Drude continued his work in optics and the electron theory. Having declined other appointments, it was only with some reluctance that he answered the call to Berlin to take over directorship of the physics institute. Almost immediately after Drude assumed this position, the size of the institute’s staff was enlarged by a third in order to meet the demands of the increase of both the theoretical and the practical work that he brought with him. He died suddenly and unexpectedly within a year of moving to Berlin.Drude’s chief contributions fall into two categories: his early work in physical optics, in which he concentrated on the relationship between the physical properties and the optical characteristics of crystals, and his later work, in which he attempted to explain both physical and optical properties in a unified theory. In both phases theory and experiment were carefully interwoven; the transition in Drude’s orientation is closely correlated with his change from a mechanical to an electromagnetic view of optical phenomena.Drude may be considered the intellectual descendant of Franz Neumann—the first of Germany’s great theoretical physicists, who developed a mechanical theory of light propagation based on the work of Fresnel and closely related to Fresnel’s own theory. It was a mechanical theory which assumed that light oscillations were of a mechanical-elastic nature, transmitted through an ether conceived of as an elastic solid. Neumann’s theory had its counterparts in England and France but was distinguished by the power and rigor of the mathematical analysis and by the assumption that the density of the ether is the same in all bodies. This leads to the conclusion that the displacement of ether particles in a plane polarized ray is in the plane of polarization. (The Fresnel theory assumed that the elasticity of the ether was the same in all bodies, leading to the conclusion that the displacement of ether particles is perpendicular to the plane of polarization.) Neumann was not only a theoretical physicist. At Königsberg he worked both in the physics department and the department of mineralogy. It was quite natural then that he should do extensive work on the optical properties of crystals. His laboratory was well equipped to investigate the structure of crystals and their elastic properties. Voigt, whose work continued that of Neumann, was particularly interested in magneto-and electro-optics. Drude’s dissertation was a direct offshoot of Voigt’s work. Voigt then set him the problem of checking his work in the laboratory, using crystals of bournonite. The experimental difficulties were great, and Drude almost immediately realized that the optical constants of such crystals were not independent of the state of the crystal’s surface. He discovered that the index of refraction and the coefficient of reflection of a crystal changed steadily from the time it was freshly cleaved. With characteristic care and thoroughness Drude then undertook a reexamination of the optical constants of a wide variety of absorbing substances, making measurements as difficult and exacting as those of the original experiments. When he was finished the optical constants of a wide variety of substances were known to an accuracy hitherto unthinkable.

This work occupied Drude from 1887 to 1891. During this period, too, he first became interested in Maxwell’s work in electrodynamics, stimulated by Hertz’s detection of electromagnetic radiation. Maxwell’s treatise of 1873 was translated into German in 1882; but Maxwell’s views were not widely accepted. The mechanical view of light propagation still held sway, and it had been under the influence of that theory that Drude had been working.Drude did not become an immediate convert to the electromagnetic point of view. In 1888 he began an intensive four-year study, first immersing himself in the electromagnetic point of view, then reexamining the mechanical theory of light. He did not feel obliged to reject the mechanical theory which—although it presented some difficulty, especially in regard to the propagation of transverse waves through an elastic medium—had served so well.Finally Drude took a phenomenological approach, attempting to remove nonessential elements from the mechanical formulation of optics. He argued that the differential equations and the imposed boundary conditions must be retained while assumptions about the mechanical nature of light waves and the elasticity of the ether were extraneous. He published the fruits of his investigation in a paper entitled “In wie weit genügen die bisherigen Lichttheorien den Anforderungen der praktischen Physik?” (1892). In this paper Drude pointed out that if the investigator restricted himself to differential equations and necessary boundary conditions, which he designated as the “explanation system” (Erklärungssystem), the mechanical and electromagnetic theories were equivalent. For example, to transform the mechanical view to the electromagnetic view, instead of such terms as “density,” “elasticity,” and “velocity of the ether,” one needed only to substitute “magnetic permeability,” “dielectric constant,” and “magnetic field strength.” Drude’s paper was much in the spirit of Hertz’s own assertions about Maxwell’s theory—that the Maxwell theory should be considered as Maxwell differential equations.

Drude gradually took up the electromagnetic view-point. In another paper of 1892, “Ueber magnetiooptische Erscheinungen,” he developed a system of equations directly from Maxwell’s equations to account for Kerr’s discovery that the reflectivity of magnetic substances (iron, cobalt, and nickel) is influenced by the state of magnetization and for Kundt’s observation that the plane of polarization of light is rotated in passing through thin plates of these substances. Although the ease with which Maxwell’s theory allowed such work to be done was important to Drude, he did not yet advocate one theory to the exclusion of the other. Rather, for another two years he lectured at Göttingen on the Maxwell theory; these lectures led to the publication of his first book, Die Physik des Äthers (1894). As a result of the heuristic effect that Maxwell’s theory had on his own work between 1894 and 1898, Drude became an advocate of the electromagnetic view.With his move to Leipzig, Drude’s work on physical constants and his work on electromagnetic radiation began to merge into one set of coherent concerns. Drude had already hinted in some of his published work that by using the electromagnetic theory one might be able to explain electrical and optical properties of matter as the interaction of electromagnetic fields with electrical charges contained within the body. The publication of Lorentz’ electron theory between 1892 and 1895 undoubtedly spurred him in that direction.Shortly after arriving at Leipzig in 1894, Drude undertook further investigations on the relationship between optical and electrical constants and the constitution of substances. Using seventy to eighty centimeters radiation, he measured coefficients of absorption in a wide variety of solutions and compared these to coefficients of conductivity for the same solutions. According to Maxwellian theory, a close correlation should have existed between electrical conductivity and absorption of light—the higher the conductivity, the greater should be the absorption. Drude found, however, that this was not always the case. For example, the absorption coefficients of amyl alcohol and copper salt solutions might be the same, whereas the conductivity of the copper salt solution might be thousands of times greater than the conductivity of the alcohol. By careful and controlled experimentation, Drude found that, in fact, a whole class of substances absorbed seventy-five centimeters electromagnetic radiation—quite independent of their coefficient of conductivity when it was measured by direct current methods. The same substances also exhibited a marked deviation from expected values of their dielectric constants and also exhibited anomalous dispersion. Drude was able to demonstrate that selective absorption of seventy-five centimeters radiation was directly related to the chemical structure of substances and that it was the hydroxyl radical (OH) that was responsible. Thus he developed a new practical analytic tool for chemists.The problem presented some theoretical difficulties. The obvious explanation for selective absorption would have to be based on the hypothesis that it represented a resonance phenomenon with the natural period of the molecular constituents of the substance; this suggested to Drude that the natural period at the atomic level was not independent of the particular molecular arrangement since a much higher resonance frequency would be expected of independent considerations.

The organization of Drude’s Lehrbuch der Optik (1900) reflects his own approach to problems in optics. The first half of the book is devoted almost exclusively to the phenomena and to their mathematical characterization. Then, after a brief outline of the mechanical and electromagnetic theories, Drude gives what he considers to be the advantages of the electromagnetic theory: first, transverse waves are a direct consequence of Maxwell’s conception of electromagnetic interaction; second, special boundary conditions are not required in the electromagnetic theory for radiation in the optical region of the spectrum; and third, the velocity of light can be determined directly from electromagnetic experiments. “In fact,” Drude wrote, “it is an epoch-making advance in natural science when in this way two originally distinct fields of investigation, like optics and electricity, are brought into relations which can be made the subject of quantitative measurements” .Drude’s move to Giessen thus occurred at a time when he was intent on understanding the optical, thermal, and electrical properties of metals by application of the electron theory. Drude was not the only person interested in such a practical application of the electron theory. Both J. J. Thomson and E. Riecke made substantial though different contributions. In the theory developed by Drude every metal contains a large number of free electrons, which he treated as a gas, the electrons having an average kinetic energy equal to the average kinetic energy of the atoms and molecules of the substance. The essential difference between conductors and nonconductors was that nonconductors contained relatively few free electrons. In early versions of his theory, Drude assumed that both positive and negative electrons were part of the “gas” but in a later simplification assumed that only negative electrons were mobile. Using the temperature of the substance as an index of the average kinetic energy of the particles in the electron gas, the velocity of the electrons should be enormous if it were not for the very small mean free path—due, mainly, to collisions with atomic centers.Consider a neutral conductor, not under the influence of an electric force. Since the motion of the electron gas is perfectly random, there should be no net charge created at any point and no net transfer of electricity from one point to another. Under the influence of an electric field, however, there should be an increase in the average velocity of electrons in one direction and a decrease in their average velocity in the opposite direction. Such a situation would constitute an electric current whose intensity should be theoretically calculable. Drude arrived at the result that the electrical conductivity would be given by  where e is the charge on a single electron, N is the number of electrons per unit volume, l is the mean free path, m is the mass of the electron, and u is the average velocity of the electrons. Since the electrons are treated as a gas, the average kinetic energy of the gas should be proportional to the absolute temperature. The coefficient of conductivity may thus be expressed as absolute temperature:where T is the temperature and α is a universal constant.The power of Drude’s analysis lies in that when one turns to different phenomena, such as thermal conductivity, the analysis is similar. Suppose the ends of a metal bar be maintained at different temperatures. The conduction of heat in the metal is due to collisions between the free electrons. The mean free path, however, is determined as before by collisions with essentially stationary metal atoms. Based on these assumptions, the coefficient of thermal conductivity for a substance is given by Drude used a scheme of this type to account for such things as thermoelectric and magnetoelectric effects. While agreement with experimental results was never perfect, it was usually within the right order of magnitude. For example, the ratio of Drude’s values for the thermal and electrical conductivity of a substance is proportional to the absolute temperature:Since α and e are both universal constants, Drude would have predicted that the ratio of thermal to electric conductivity at a given temperature was the same for all metals. Although this is not precisely true it is a good approximation to what was known to be the case experimentally.Drude did not make these researches serially; typically, he had several different research projects in progress at the same time—in addition to lecturing, directing doctoral students, heading the various physical institutes, and editing the Annalen der Physik. Drude carried this diverse and taxing load with grace and performed his duties with characteristic thoroughness.

Drude died a week after he had written the foreword to the second edition of his Lehrbuch der Optik and six days after he had given his inaugural speech at the Berlin Academy—a speech in which he sketched plans for future research.The crater Drude on the Moon is named after him.The Paul-Drude-Institut für Festkörperelektro, in Berlin, was named in his honor.

Robert Boyle

Boyle was born in Ireland.Among the many contenders for the title of "Father of Modern Chemistry" is Robert Boyle (January 25, 1627 - December 30, 1691). Boyle was the first prominent scientist to perform controlled experiments and to publish his work with elaborate details concerning procedure, apparatus and observations. He assembled what we would today call a "research group", developed a key piece of apparatus - the vacuum pump, was instrumental in founding the Royal Society, and deserves at least partial credit for the famous gas law which bears his name. As the youngest of fourteen children of the wealthiest man in the British Isles, Boyle's opportunities were almost unlimited. However, while still in adolescence, he chose the pseudonym Philaretus (Lover of Truth) and a life of scientific inquiry seemed almost inevitable. He was educated in the finest possible manner of this day, first studying at Eton and later travelling the Continent with a tutor and his older brother Francis. He learned philosophy, religion, languages, mathematics, and - perhaps most significantly - the new physics of Bacon, Descartes, and Galileo. The physical scientists and their new theories concerning air and vacuum, the movement of planets, and the circulation of blood were to sway his thinking much more than the alchemists.

Although his research clearly has its roots in the alchemical tradition, Boyle is largely regarded today as the first modern chemist, and therefore one of the founders of modern chemistry, and one of the pioneers of modern experimental scientific method.He is best known for Boyle's law, which describes the inversely proportional relationship between the absolute pressure and volume of a gas, if the temperature is kept constant within a closed system. Among his works, The Sceptical Chymist is seen as a cornerstone book in the field of chemistry.

Boyle published copiously on topics ranging across several fields of science, philosophy, and theology. His first major scientific report, The Spring and Weight of the Air, was published in 1660 and described experiments using a new vacuum pump of his design. Previous pumps, invented by von Guericke (of Magdeburg hemisphere fame), required the strenuous efforts of two men and provided dubious results. Boyle's pump could be operated easily and efficiently by one man. With it Boyle demonstrated that the sound of a bell in the receiver (a thirty quart vacuum chamber) faded as the air was removed, proving that air was necessary for the transmission of sound. In further experiments, he also proved that air was necessary for life and for a candle flame. Boyle felt that his experiments confirmed a mechanical view of nature as opposed to the Aristotelian, non-empirical approach to science. Today we are so accustomed to empirical science that we have difficulty understanding how one could attempt scientific work using only logic. Boyle's empiricism established him as a founder of the modern scientific method and his arguments were so persuasive as to win many important converts, most notably Isaac Newton.The second edition of The Spring and Weight of the Air, published in 1662, contained the pressure - volume inverse relationship which is familiar to every chemistry student as Boyle's Law. In performing the experiments which led to this generalization, Boyle used mercury in a J-tube and made measurements of the volume of the trapped gas at pressures both higher and lower than normal atmospheric pressure. There is some controversy in naming the relationship after Boyle since much of the work was actually performed by his assistant Robert Hooke, however, the experimental concept originated with Boyle. Furthermore, Boyle was dedicated to the idea of experimental proof of theories while Hooke felt that theories should appeal to reason.Boyle's best known contribution to scientific knowledge is the 1661 publication of The Sceptical Chymist in which he discusses the idea of an element. Aristotelian science held that elements were not just the simplest of all substances but were also necessary ingredients of all bodies, i.e., if water is an element then all bodies must contain at least a small amount of water. Boyle's idea of an element was somewhat vague and certainly not "modern" in the 20th century sense. But he presented persuasive experimental evidence that most of the commonly accepted elements (fire, water, salt, mercury, etc) did not meet both of the Aristotelian criteria.In The Sceptical Chymist , Boyle makes a clear break with the alchemists' tradition of secrecy with his conviction and insistence on publishing in great experimental detail. It is noteworthy that Boyle was among the first to publish the details of his work, including unsuccessful experiments, but Boyle was never able to abandon the beliefs of alchemy. He believed in transmutation of the elements and in 1676, he reported to the Royal Society on his attempts to change quicksilver into gold. He believed that he was near success in this endeavor.

In 1654, Boyle had joined a small group of the most influential English scientists, mathematicians, philosophers and physicians who had been meeting weekly in London and in Oxford since 1645. In 1662 the group was chartered as the Royal Society which exists today as the oldest continuous scientific society in the world. The motto of this prestigious organization, "Nullius in Verba" means "nothing in words", i.e., all science should be experimentally based. In 1680, Robert Boyle was elected president of the Royal Society, but declined the honor because the required oath violated his religious principles.The first use of the term "chemical analysis" is attributed to Boyle who used it in the same sense that we understand it today. He performed assays on gold and silver, tested for copper with ammonia, tested for salt in water with silver nitrate, and devised a thirty item test for mineral water analysis. In addition, he observed that all acids turned a particular vegetable indicator from blue to red and all alkalis turned the indicator green. He found that some substances did not change the color of the indicator and concluded that these were neutral. He thus provided an operational method of classifying substances.Boyle never married and from the age of 41 lived with his sister Katherine, Lady Ranelagh. He was a shy man with deep religious convictions. He had been a pious youth spending some years in the care of the village parson, Mr. W. Douch. Then at the age of 13, during a violent thunderstorm, he experienced a religious conversion not unlike that of St. Paul. Although an ardent defender of the Anglican Church, he was tolerant of the religious views of others and in later years became particularly sympathetic to the Dissenters. He was offered a position in the clergy but felt a stronger commitment to science. He saw no conflict between the two. He wrote widely on religious themes and gave financial support to his his friend Edward Pococke to translate the New Testament into Malayan. He left a large portion of his considerable estate to charitable organizations.

Robert Boyle died in London on December 30, 1691. He was buried in the Church of Saint-Martin-in-the-Fields next to his sister. Later the church was demolished and no record was made as to where his remains were moved.Typically, Robert Boyle is remembered solely for Boyle's Law. It is clear that he contributed much more to the development of modern chemical thought. Robert Boyle has been deservedly called "a Mighty Chemist".

Max Planck

Max Karl Ernst Ludwig Planck was born in Kiel, Germany, on April 23, 1858, the son of Julius Wilhelm and Emma (néePatzig) Planck.  He is regarded as the founder of quantum theory, for which he received the Nobel Prize in Physics in 1918.His father was Professor of Constitutional Law in the University of Kiel, and later in Göttingen.Planck studied at the Universities of Munich and Berlin, where his teachers included Kirchhoff and Helmholtz, and received his doctorate of philosophy at Munich in 1879. He was Privatdozent in Munich from 1880 to 1885, then Associate Professor of Theoretical Physics at Kiel until 1889, in which year he succeeded Kirchhoff as Professor at Berlin University, where he remained until his retirement in 1926. Afterwards he became President of the Kaiser Wilhelm Society for the Promotion of Science, a post he held until 1937. The Prussian Academy of Sciences appointed him a member in 1894 and Permanent Secretary in 1912.

Planck's earliest work was on the subject of thermodynamics, an interest he acquired from his studies under Kirchhoff, whom he greatly admired, and very considerably from reading R. Clausius' publications. He published papers on entropy, on thermoelectric ity and on the theory of dilute solutions.At the same time also the problems of radiation processes engaged his attention and he showed that these were to be considered as electromagnetic in nature. From these studies he was led to the problem of the distribution of energy in the spectrum of full radiation. Experimental observations on the wavelength distribution of the energy emitted by a black body as a function of temperature were at variance with the predictions of classical physics. Planck was able to deduce the relationship between the energy and the frequency of radiation. In a paper published in 1900, he announced his derivation of the relationship: this was based on the revolutionary idea that the energy emitted by a resonator could only take on discrete values or quanta. The energy for a resonator of frequency v is hv where h is a universal constant, now called Planck's constant.This was not only Planck's most important work but also marked a turning point in the history of physics. The importance of the discovery, with its far-reaching effect on classical physics, was not appreciated at first. However the evidence for its validity gradually became overwhelming as its application accounted for many discrepancies between observed phenomena and classical theory. Among these applications and developments may be mentioned Einstein's explanation of the photoelectric effect.

Planck's work on the quantum theory, as it came to be known, was published in the Annalen der Physik. His work is summarized in two books Thermodynamik (Thermodynamics) (1897) and Theorie der Wärmestrahlung (Theory of heat radiat ion) (1906).He was elected to Foreign Membership of the Royal Society in 1926, being awarded the Society's Copley Medal in 1928.Planck faced a troubled and tragic period in his life during the period of the Nazi government in Germany, when he felt it his duty to remain in his country but was openly opposed to some of the Government's policies, particularly as regards the persecution of the Jews. In the last weeks of the war he suffered great hardship after his home was destroyed by bombing.He was revered by his colleagues not only for the importance of his discoveries but for his great personal qualities. He was also a gifted pianist and is said to have at one time considered music as a career.

Planck was twice married. Upon his appointment, in 1885, to Associate Professor in his native town Kiel he married a friend of his childhood, Marie Merck, who died in 1909. He remarried her cousin Marga von Hösslin. Three of his children died young, leaving him with two sons.He suffered a personal tragedy when one of them was executed for his part in an unsuccessful attempt to assassinate Hitler in 1944.He died at Göttingen on October 4, 1947.

George Boole

George Boole's father, John Boole (1779–1848), was a tradesman of limited means, but of "studious character and active mind".Being especially interested in mathematical science and logic, the father gave his son his first lessons; but the extraordinary mathematical talents of George Boole did not manifest themselves in early life. At first, his favorite subject was classics. By his teens, he had learned Latin, Greek, German, Italian, and French.ith these languages, he was able to read a wide variety of Christian theology. Combining his interests in mathematics and theology, he compared the Christian trinity of Father, Son, and Holy Ghost with the three dimensions of space, and was attracted to the Hebrew conception of God as an absolute unity. Boole considered converting to Judaism but in the end choose Unitarianism.The original Working Class Boy Made Good, Boole was born in the wrong time, in the wrong place, and definitely in the wrong class - he didn't have a hope of growing up to be a mathematical genius, but he did it anyway.

Born in the English industrial town of Lincoln, Boole was lucky enough to have a father who passed along his own love of math. Young George took to learning like a politician to a pay rise and, by the age of eight, had outgrown his father's self-taught limits.A family friend stepped in to teach the boy basic Latin, and was exhausted within a few years. Boole was translating Latin poetry by the age of twelve. By the time he hit puberty, the adolescent George was fluent in German, Italian and French. At 16 he became an assistant teacher, at 20 he opened his own school.Over the next few years, depending mainly on mathematical journals borrowed from the local Mechanic's Institute, Boole struggled with Isaac Newton's 'Principia' and the works of 18th and 19th century French mathematicians Pierre-Simon Laplace and Joseph-Louis Lagrange. He had soon mastered the most intricate mathematical principles of his day.It was time to move on.

At the age of 24, George Boole published his first paper ('Researches on the Theory of Analytical Transformations') in the Cambridge Mathematical Journal. Over the next ten years, his star rose as a steady stream of original articles began to push the limits of mathematics.By 1844 he was concentrating on the uses of combined algebra and calculus to process infinitely small and large figures, and, in that same year, received a Royal Society medal for his contributions to analysis.Boole soon began to see the possibilities for applying his algebra to the solution of logical problems. Boole's 1847 work, 'The Mathematical Analysis of Logic', not only expanded on Gottfried Leibniz' earlier speculations on the correlation between logic and math, but argued that logic was principally a discipline of mathematics, rather than philosophy.It was this paper that won him, not only the admiration of the distinguished logician Augustus de Morgan (a mentor of Ada Byron's), but a place on the faculty of Ireland's Queen's College.Without a school to run, Boole began to delve deeper into his own work, concentrating on refining his 'Mathematical Analysis', and determined to find a way to encode logical arguments into an indicative language that could be manipulated and solved mathematically.He came up with a type of linguistic algebra, the three most basic operations of which were (and still are) AND, OR and NOT. It was these three functions that formed the basis of his premise, and were the only operations necessary to perform comparisons or basic mathematical functions.Boole's system (detailed in his 'An Investigation of the Laws of Thought, on Which Are Founded the Mathematical Theories of Logic and Probabilities', 1854) was based on a binary approach, processing only two objects - the yes-no, true-false, on-off, zero-one approach.Surprisingly, given his standing in the academic community, Boole's idea was either criticised or completely ignored by the majority of his peers. Luckily, American logician Charles Sanders Peirce was more open-minded.Twelve years after Boole's 'Investigation' was published, Pierce gave a brief speech describing Boole's idea to the American Academy of Arts and Sciences - and then spent more than 20 years modifying and expanding it, realising the potential for use in electronic circuitry and eventually designing a fundamental electrical logic circuit.Pierce never actually built his theoretical logic circuit, being himself more of a logician than an electrician, but he did introduce boolean algebra into his university logic philosophy courses.Eventually, one bright student - Claude Shannon - picked up the idea and ran with it.

Boole published a number of papers following his 'Investigation', the two most influential probably being a 'Treatise on Differential Equations' (1859) and 'Treatise on the Calculus of Finite Differences' (1860).Unfortunately, Boole's life was cut short when he died of a 'feverish cold' at the age of 49, after walking 2 miles through the rain to get to class and then lecturing in wet clothes (proving, once again, that genius and common sense sometimes have a less than nodding acquaintance).With George Boole's 'Mathematical Analysis' and 'Investigation', boolean algebra, sometimes known as boolean logic, came into being.His two value system, separating arguments into different classes which can then be processed according to the presence or absence of a certain property, enabled any proposition - regardless of the number of individual items - to draw logical conclusions.Boole's texts led to the development of applications he could never have imagined.

Friedrich Hund

Friedrich Hund was born in Karlsruhe on February 4th 1896. He was  employed by University of Rostock. Hund graduated from University of Leipzig and University of Rostock. He worked as a physicist.Hund worked at the Universities of Rostock,Leipzig,Jena,FrankfurtamMain and Gottingen.Hund worked with prestigious physicists as Schrodinger,Dirac,Heisenberg,Max Born and Walter Bothe. At that time, he was Born's assistant, working with quantum interpretation of band spectra of diatomic molecules.

After his studies of mathematics, physics, and geography in Marburg and Göttingen, he worked as a private lecturer for theoretical physics in Göttingen (1925), professor in Rostock (1927), Leipzig (1929), Jena (1946), Frankfurt/Main (1951) and from 1957 again in Göttingen. Additionally, he stayed in Copenhagen (1926) with Niels Bohr and lectured on the atom at Harvard University in Cambridge, Massachusetts (1928). He published more than 250 papers and essays in total. Hund made pivotal contributions to quantum theory - especially concerning the structure of the atom and of molecular spectra.

In fact, Robert S.Mulliken, who was awarded the 1966 Nobel Prize in chemistry for molecular orbital theory, always proclaimed the great influence Hund's work had on his own and that he would have gladly shared the Nobel prize with Hund. In recognition of the importance of Hund's contributions, MO theory is often referred to as the Hund-Mulliken MO theory.Hund's rule of maximum multiplicity is another eponym and, in 1926, Hund discovered the so-called tunnel effect or quantum tunnelling.The Hund's cases, which are particular regimes in molecular angular momentum coupling, and Hund's rules, which govern electron configurations, are important in spectroscopy and quantum chemistry. In chemistry, the first rule, Hund's rule of maximum multiplicity, is especially important and is often referred to as simply Hund's Rule.

On the occasion of his 100th birthday, the book: Friedrich Hund: Geschichte der physikalischen Begriffe [History of Physical Concepts] (Heidelberg, Berlin, Oxford), Spektrum, Akademie Verlag 1996, ISBN 3-8274-0083-X was published. A review was also written by Werner Kutzelnigg.Besides many different honors bestowed upon him, Friedrich Hund became an honorary citizen of Jena/Saale, and a street in Jena was named after him. Since June 2004, in Göttingen, a part of the new building of the Physics Department was given the Friedrich-Hund-Platz 1 address. The same name was chosen for the Institute for Theoretical Physics at the University of Göttingen.

He was a member of the International Academy of Quantum Molecular Science. He died in Göttingen in March 1997 aged 101 years and 1 month old.