J. J. Thomson
Sir Joseph John Thomson was an English physicist and Nobel Laureate in Physics, credited with the discovery and identification of the electron, the first subatomic particle to be discovered. In 1897, Thomson showed that cathode rays were composed of unknown negatively charged particles, which he calculated must have bodies much smaller than atoms and a large charge-to-mass ratio. Thomson is credited with finding the first evidence for isotopes of a stable element in 1913, as part of his exploration into the composition of canal rays, his experiments to determine the nature of positively charged particles, with Francis William Aston, were the first use of mass spectrometry and led to the development of the mass spectrograph. Thomson was awarded the 1906 Nobel Prize in Physics for his work on the conduction of electricity in gases. Joseph John Thomson was born 18 December 1856 in Cheetham Hill, Lancashire, England, his mother, Emma Swindells, came from a local textile family. His father, Joseph James Thomson, ran.
He had a brother, Frederick Vernon Thomson, two years younger than he was. J. J. Thomson was a devout Anglican, his early education was in small private schools where he demonstrated outstanding talent and interest in science. In 1870, he was admitted to Owens College in Manchester at the unusually young age of 14, his parents planned to enroll him as an apprentice engineer to Sharp-Stewart & Co, a locomotive manufacturer, but these plans were cut short when his father died in 1873. He moved on to Trinity College, Cambridge, in 1876. In 1880, he obtained his Bachelor of Arts degree in mathematics, he applied for and became a Fellow of Trinity College in 1881. Thomson received his Master of Arts degree in 1883. In 1890, Thomson married Rose Elisabeth Paget, one of his former students, daughter of Sir George Edward Paget, KCB, a physician and Regius Professor of Physic at Cambridge at the church of St. Mary the Less, they had one son, George Paget Thomson, one daughter, Joan Paget Thomson. On 22 December 1884, Thomson was appointed Cavendish Professor of Physics at the University of Cambridge.
The appointment caused considerable surprise, given that candidates such as Osborne Reynolds or Richard Glazebrook were older and more experienced in laboratory work. Thomson was known for his work as a mathematician, he was awarded a Nobel Prize in 1906, "in recognition of the great merits of his theoretical and experimental investigations on the conduction of electricity by gases." He was knighted in 1908 and appointed to the Order of Merit in 1912. In 1914, he gave the Romanes Lecture in Oxford on "The atomic theory". In 1918, he became Master of Trinity College, where he remained until his death. Joseph John Thomson died on 30 August 1940. One of Thomson's greatest contributions to modern science was in his role as a gifted teacher. One of his students was Ernest Rutherford, who succeeded him as Cavendish Professor of Physics. In addition to Thomson himself, six of his research assistants won Nobel Prizes in physics, two won Nobel prizes in chemistry. In addition, Thomson's son won the 1937 Nobel Prize in physics for proving the wave-like properties of electrons.
Thomson's prize-winning master's work, Treatise on the motion of vortex rings, shows his early interest in atomic structure. In it, Thomson mathematically described the motions of William Thomson's vortex theory of atoms. Thomson published a number of papers addressing both mathematical and experimental issues of electromagnetism, he examined the electromagnetic theory of light of James Clerk Maxwell, introduced the concept of electromagnetic mass of a charged particle, demonstrated that a moving charged body would increase in mass. Much of his work in mathematical modelling of chemical processes can be thought of as early computational chemistry. In further work, published in book form as Applications of dynamics to physics and chemistry, Thomson addressed the transformation of energy in mathematical and theoretical terms, suggesting that all energy might be kinetic, his next book, Notes on recent researches in electricity and magnetism, built upon Maxwell's Treatise upon electricity and magnetism, was sometimes referred to as "the third volume of Maxwell".
In it, Thomson emphasized physical methods and experimentation and included extensive figures and diagrams of apparatus, including a number for the passage of electricity through gases. His third book, Elements of the mathematical theory of electricity and magnetism was a readable introduction to a wide variety of subjects, achieved considerable popularity as a textbook. A series of four lectures, given by Thomson on a visit to Princeton University in 1896, were subsequently published as Discharge of electricity through gases. Thomson presented a series of six lectures at Yale University in 1904. Several scientists, such as William Prout and Norman Lockyer, had suggested that atoms were built up from a more fundamental unit, but they envisioned this unit to be the size of the smallest atom, hydrogen. Thomson in 1897 was the first to suggest that one of the fundamental units was more than 1,000 times smaller than an atom, suggesting th
In particle physics, quantum electrodynamics is the relativistic quantum field theory of electrodynamics. In essence, it describes how light and matter interact and is the first theory where full agreement between quantum mechanics and special relativity is achieved. QED mathematically describes all phenomena involving electrically charged particles interacting by means of exchange of photons and represents the quantum counterpart of classical electromagnetism giving a complete account of matter and light interaction. In technical terms, QED can be described as a perturbation theory of the electromagnetic quantum vacuum. Richard Feynman called it "the jewel of physics" for its accurate predictions of quantities like the anomalous magnetic moment of the electron and the Lamb shift of the energy levels of hydrogen; the first formulation of a quantum theory describing radiation and matter interaction is attributed to British scientist Paul Dirac, able to compute the coefficient of spontaneous emission of an atom.
Dirac described the quantization of the electromagnetic field as an ensemble of harmonic oscillators with the introduction of the concept of creation and annihilation operators of particles. In the following years, with contributions from Wolfgang Pauli, Eugene Wigner, Pascual Jordan, Werner Heisenberg and an elegant formulation of quantum electrodynamics due to Enrico Fermi, physicists came to believe that, in principle, it would be possible to perform any computation for any physical process involving photons and charged particles. However, further studies by Felix Bloch with Arnold Nordsieck, Victor Weisskopf, in 1937 and 1939, revealed that such computations were reliable only at a first order of perturbation theory, a problem pointed out by Robert Oppenheimer. At higher orders in the series infinities emerged, making such computations meaningless and casting serious doubts on the internal consistency of the theory itself. With no solution for this problem known at the time, it appeared that a fundamental incompatibility existed between special relativity and quantum mechanics.
Difficulties with the theory increased through the end of the 1940s. Improvements in microwave technology made it possible to take more precise measurements of the shift of the levels of a hydrogen atom, now known as the Lamb shift and magnetic moment of the electron; these experiments exposed discrepancies. A first indication of a possible way out was given by Hans Bethe in 1947, after attending the Shelter Island Conference. While he was traveling by train from the conference to Schenectady he made the first non-relativistic computation of the shift of the lines of the hydrogen atom as measured by Lamb and Retherford. Despite the limitations of the computation, agreement was excellent; the idea was to attach infinities to corrections of mass and charge that were fixed to a finite value by experiments. In this way, the infinities get absorbed in those constants and yield a finite result in good agreement with experiments; this procedure was named renormalization. Based on Bethe's intuition and fundamental papers on the subject by Shin'ichirō Tomonaga, Julian Schwinger, Richard Feynman and Freeman Dyson, it was possible to get covariant formulations that were finite at any order in a perturbation series of quantum electrodynamics.
Shin'ichirō Tomonaga, Julian Schwinger and Richard Feynman were jointly awarded with a Nobel prize in physics in 1965 for their work in this area. Their contributions, those of Freeman Dyson, were about covariant and gauge invariant formulations of quantum electrodynamics that allow computations of observables at any order of perturbation theory. Feynman's mathematical technique, based on his diagrams seemed different from the field-theoretic, operator-based approach of Schwinger and Tomonaga, but Freeman Dyson showed that the two approaches were equivalent. Renormalization, the need to attach a physical meaning at certain divergences appearing in the theory through integrals, has subsequently become one of the fundamental aspects of quantum field theory and has come to be seen as a criterion for a theory's general acceptability. Though renormalization works well in practice, Feynman was never comfortable with its mathematical validity referring to renormalization as a "shell game" and "hocus pocus".
QED has served as the template for all subsequent quantum field theories. One such subsequent theory is quantum chromodynamics, which began in the early 1960s and attained its present form in the 1970s work by H. David Politzer, Sidney Coleman, David Gross and Frank Wilczek. Building on the pioneering work of Schwinger, Gerald Guralnik, Dick Hagen, Tom Kibble, Peter Higgs, Jeffrey Goldstone, others, Sheldon Lee Glashow, Steven Weinberg and Abdus Salam independently showed how the weak nuclear force and quantum electrodynamics could be merged into a single electroweak force. Near the end of his life, Richard P. Feynman gave a series of lectures on QED intended for the lay public; these lectures were transcribed and published as Feynman, QED: The strange theory of light and matter, a classic non-mathematical exposition of QED from the point of view articulated below. The key components of Feynman's presentation of QED are three basic actions. A photon goes from time to another place and time. An electron goes from time to another place and time.
An electron absorbs a photon at a certain place and time. These actions are represented in the form of visual shorthand by the three basic elements of Feynman diagrams: a wavy line for the photon, a straight line for the electron and a junction of two straight lines and a wavy one for a vertex representing em
Johannes Diderik van der Waals
Johannes Diderik van der Waals was a Dutch theoretical physicist and thermodynamicist famous for his work on an equation of state for gases and liquids. His name is associated with the van der Waals equation of state that describes the behavior of gases and their condensation to the liquid phase, his name is associated with van der Waals forces, with van der Waals molecules, with van der Waals radii. As James Clerk Maxwell said about Van der Waals, "there can be no doubt that the name of Van der Waals will soon be among the foremost in molecular science."In his 1873 thesis, van der Waals noted the non-ideality of real gases and attributed it to the existence of intermolecular interactions. He introduced the first equation of state derived by the assumption of a finite volume occupied by the constituent molecules. Spearheaded by Ernst Mach and Wilhelm Ostwald, a strong philosophical current that denied the existence of molecules arose towards the end of the 19th century; the molecular existence was considered the molecular hypothesis unnecessary.
At the time van der Waals' thesis was written, the molecular structure of fluids had not been accepted by most physicists, liquid and vapor were considered as chemically distinct. But van der Waals's work affirmed the reality of molecules and allowed an assessment of their size and attractive strength, his new formula revolutionized the study of equations of state. By comparing his equation of state with experimental data, Van der Waals was able to obtain estimates for the actual size of molecules and the strength of their mutual attraction; the effect of Van der Waals's work on molecular physics in the 20th century was direct and fundamental. By introducing parameters characterizing molecular size and attraction in constructing his equation of state, Van der Waals set the tone for modern molecular science; that molecular aspects such as size, shape and multipolar interactions should form the basis for mathematical formulations of the thermodynamic and transport properties of fluids is presently considered an axiom.
With the help of the van der Waals's equation of state, the critical-point parameters of gases could be predicted from thermodynamic measurements made at much higher temperatures. Nitrogen, oxygen and helium subsequently succumbed to liquefaction. Heike Kamerlingh Onnes was influenced by the pioneer work of van der Waals. In 1908, Onnes became the first to make liquid helium. Van der Waals started his career as a school teacher, he became the first physics professor of the University of Amsterdam when in 1877 the old Athenaeum was upgraded to Municipal University. Van der Waals won the 1910 Nobel Prize in physics for his work on the equation of state for gases and liquids. Johannes Diderik van der Waals was born on 23 November 1837 in Leiden in the Netherlands, he was the eldest of ten children born to Elisabeth van den Berg. His father was a carpenter in Leiden; as was usual for working-class children in the 19th century, he did not go to the kind of secondary school that would have given him the right to enter university.
Instead he went to a school of “advanced primary education”, which he finished at the age of fifteen. He became a teacher's apprentice in an elementary school. Between 1856 and 1861 he followed courses and gained the necessary qualifications to become a primary school teacher and head teacher. In 1862, he began to attend lectures in mathematics and astronomy at the University in his city of birth, although he was not qualified to be enrolled as a regular student in part because of his lack of education in classical languages. However, the University of Leiden had a provision that enabled outside students to take up to four courses a year. In 1863 the Dutch government started a new kind of secondary school. Van der Waals—at that time head of an elementary school—wanted to become a HBS teacher in mathematics and physics and spent two years studying in his spare time for the required examinations. In 1865, he was appointed as a physics teacher at the HBS in Deventer and in 1866, he received such a position in The Hague, close enough to Leiden to allow van der Waals to resume his courses at the University there.
In September 1865, just before moving to Deventer, van der Waals married the eighteen-year-old Anna Magdalena Smit. Van der Waals still lacked the knowledge of the classical languages that would have given him the right to enter university as a regular student and to take examinations. However, it so happened that the law regulating the university entrance was changed and dispensation from the study of classical languages could be given by the minister of education. Van der Waals was given this dispensation and passed the qualification exams in physics and mathematics for doctoral studies. At Leiden University, on June 14, 1873, he defended his doctoral thesis Over de Continuïteit van den Gas- en Vloeistoftoestand under Pieter Rijke. In the thesis, he introduced the concepts of molecular attraction. In September 1877 van der Waals was appointed the first professor of physics at the newly founded Municipal University of Amsterdam. Two of his notable colleagues were the physical chemist Jacobus Henricus van't Hoff and the biologist Hugo de Vries.
Until his retirement at the age of 70 van der Waals remained at the Amsterdam University. He was succeeded by his
Nobel Prize in Physics
The Nobel Prize in Physics is a yearly award given by the Royal Swedish Academy of Sciences for those who have made the most outstanding contributions for humankind in the field of physics. It is one of the five Nobel Prizes established by the will of Alfred Nobel in 1895 and awarded since 1901; the first Nobel Prize in Physics was awarded to physicist Wilhelm Röntgen in recognition of the extraordinary services he rendered by the discovery of the remarkable rays. This award is administered by the Nobel Foundation and regarded as the most prestigious award that a scientist can receive in physics, it is presented in Stockholm at an annual ceremony on 10 December, the anniversary of Nobel's death. Through 2018, a total of 209 individuals have been awarded the prize. Only three women have won the Nobel Prize in Physics: Marie Curie in 1903, Maria Goeppert Mayer in 1963, Donna Strickland in 2018. Alfred Nobel, in his last will and testament, stated that his wealth be used to create a series of prizes for those who confer the "greatest benefit on mankind" in the fields of physics, peace, physiology or medicine, literature.
Though Nobel wrote several wills during his lifetime, the last one was written a year before he died and was signed at the Swedish-Norwegian Club in Paris on 27 November 1895. Nobel bequeathed 94% of his total assets, 31 million Swedish kronor, to establish and endow the five Nobel Prizes. Due to the level of skepticism surrounding the will, it was not until April 26, 1897 that it was approved by the Storting; the executors of his will were Ragnar Sohlman and Rudolf Lilljequist, who formed the Nobel Foundation to take care of Nobel's fortune and organise the prizes. The members of the Norwegian Nobel Committee who were to award the Peace Prize were appointed shortly after the will was approved; the prize-awarding organisations followed: the Karolinska Institutet on June 7, the Swedish Academy on June 9, the Royal Swedish Academy of Sciences on June 11. The Nobel Foundation reached an agreement on guidelines for how the Nobel Prize should be awarded. In 1900, the Nobel Foundation's newly created statutes were promulgated by King Oscar II.
According to Nobel's will, The Royal Swedish Academy of sciences were to award the Prize in Physics. A maximum of three Nobel laureates and two different works may be selected for the Nobel Prize in Physics. Compared with other Nobel Prizes, the nomination and selection process for the prize in Physics is long and rigorous; this is a key reason why it has grown in importance over the years to become the most important prize in Physics. The Nobel laureates are selected by the Nobel Committee for Physics, a Nobel Committee that consists of five members elected by The Royal Swedish Academy of Sciences. In the first stage that begins in September, around 3,000 people – selected university professors, Nobel Laureates in Physics and Chemistry, etc. – are sent confidential forms to nominate candidates. The completed nomination forms arrive at the Nobel Committee no than 31 January of the following year; these nominees are scrutinized and discussed by experts who narrow it to fifteen names. The committee submits a report with recommendations on the final candidates into the Academy, where, in the Physics Class, it is further discussed.
The Academy makes the final selection of the Laureates in Physics through a majority vote. The names of the nominees are never publicly announced, neither are they told that they have been considered for the prize. Nomination records are sealed for fifty years. While posthumous nominations are not permitted, awards can be made if the individual died in the months between the decision of the prize committee and the ceremony in December. Prior to 1974, posthumous awards were permitted; the rules for the Nobel Prize in Physics require that the significance of achievements being recognized has been "tested by time". In practice, it means that the lag between the discovery and the award is on the order of 20 years and can be much longer. For example, half of the 1983 Nobel Prize in Physics was awarded to Subrahmanyan Chandrasekhar for his work on stellar structure and evolution, done during the 1930s; as a downside of this approach, not all scientists live long enough for their work to be recognized.
Some important scientific discoveries are never considered for a prize, as the discoverers die by the time the impact of their work is appreciated. A Physics Nobel Prize laureate earns a gold medal, a diploma bearing a citation, a sum of money; the Nobel Prize medals, minted by Myntverket in Sweden and the Mint of Norway since 1902, are registered trademarks of the Nobel Foundation. Each medal has an image of Alfred Nobel in left profile on the obverse; the Nobel Prize medals for Physics, Physiology or Medicine, Literature have identical obverses, showing the image of Alfred Nobel and the years of his birth and death. Nobel's portrait appears on the obverse of the Nobel Peace Prize medal and the Medal for the Prize in Economics, but with a different design; the image on the reverse of a medal varies according to the institution awarding the prize. The reverse sides of the Nobel Prize medals for Chemistry and Physics share the same design of Nature, as a Goddess, whose veil is held up by the Genius of Science.
These medals and the ones for Physiology/Medicine and Literature were designed by Erik Lindberg in 1902. Nobel laureates receive a diploma directly from the hands of the
Duchy of Brunswick
The Duchy of Brunswick was a historical German state. Its capital was the city of Brunswick, it was established as the successor state of the Principality of Brunswick-Wolfenbüttel by the Congress of Vienna in 1815. In the course of the 19th-century history of Germany, the duchy was part of the German Confederation, the North German Confederation and from 1871 the German Empire, it was disestablished after the end of World War I, its territory incorporated into the Weimar Republic as the Free State of Brunswick. The title "Duke of Brunswick and Lüneburg" was held, from 1235 on, by various members of the Welf family who ruled several small territories in northwest Germany; these holdings did not have all of the formal characteristics of a modern unitary state, being neither compact nor indivisible. When several sons of a Duke competed for power, the lands became divided between them; the unifying element of all these territories was that they were ruled by male-line descendants of Duke Otto I. After several early divisions, Brunswick-Lüneburg re-unified under Duke Magnus II.
Following his death, his three sons jointly ruled the Duchy. After the murder of their brother Frederick I, Duke of Brunswick-Lüneburg, brothers Bernard and Henry redivided the land, Henry receiving the territory of Wolfenbüttel. Albert the Tall 1269–1279. Received the southern half of Brunswick-Lüneburg as Prince of Wolfenbüttel while his brother John became Prince of Lüneburg. Albert's sons first ruled jointly, but in 1291 divided the Wolfenbüttel territory: Henry the Admirable became Prince of Grubenhagen 1291–1322 Albert II the Fat became Prince of Göttingen 1286–1318 William received Wolfenbüttel proper but died in 1292. Wolfenbüttel fell to his brother Albert II. Otto the Mild 1318 -- 1344, son of Albert II, was Prince of Prince of Göttingen. After his death his son Ernest became Prince of Göttingen 1344–1367. Magnus the Pious became Prince of Wolfenbüttel 1344–1369. Magnus' son Magnus II with the Necklace, Prince of Wolfenbüttel 1369–1373, claimed the Principality of Lüneburg against Albert of Saxe-Wittenberg.
The War of the Lüneburg Succession continued until 1388. Frederick 1373–1400, son of Magnus II, conquered Lüneburg in 1388. Succeeded by his brothers: Henry the Mild, 1400–1408 Bernard, 1409–1428. Returned control of Wolfenbüttel to his nephew, Henry's son. William the Victorious 1428–1432, nephew. Was deprived by his brother: Henry the Peaceful 1432–1473, moved the residence to Wolfenbüttel. William the Victorious 1473–1482, again. William regained control of Wolfenbüttel after his brother's death, left the Principality to his two sons: Frederick III 1482–1484. Imprisoned and deprived of power by his younger brother: William IV 1484–1491. Took control of all of Wolfenbüttel ceded Wolfenbüttel to his sons. Died 1495. Co-rulers, sons of William IV: Eric I 1491–1494. Divided the territory in 1494, taking Calenberg. Henry IV 1491–1514. Sole ruler in Wolfenbüttel from 1494. Henry V 1514–1568. Son of Henry IV. Converted to Lutheranism. Julius 1568–1589. Son of Henry V. Acquired Calenberg in 1584 on the death of his cousin Eric II.
Henry Julius 1589–1613, son. Frederick Ulrich 1613–1634, son. Last of the male descendants of Albert the Tall. On Frederick Ulrich's death, his complex of territories passed to a line of distant cousins ruling in Lüneburg. Wolfenbüttel was awarded to Augustus, son of Henry of Dannenberg. Augustus 1635–1666 Augustus's sons succeeded him, sometimes ruling together: Rudolph Augustus 1666–1704 Anthony Ulrich 1685–1702, 1704–1714. Disputed with Hanover. Deposed 1702–1704 for allying with France in the War of the Spanish Succession. Converted to Catholicism 1709. Anthony Ulrich's sons succeeded him in sequence: Augustus William 1714–1731 Louis Rudolph 1731–1735 Ferdinand Albert March–September 1735. Grandson of Augustus the Younger. Charles I 1735–1780. Son of Ferdinand Albert. Moved the ducal court from Wolfenbüttel to Braunschweig in 1753. Charles William Ferdinand 1780–1806. Son of Charles I. Died in battle at Jena. Frederick William 1806–1807, 1813–1815. Son of Charles William Ferdinand. During the Napoleonic Wars, from 1806 to 1813, France occupied Brunswick-Wolfenbüttel.
Died in battle at Quatre Bras. Frederick William's son Charles became the first Duke of independent Brunswick; the territory of Wolfenbüttel was recognized as a sovereign state by the Congress of Vienna in 1815. It had been a portion of the medieval Duchy of Brunswick-Lüneburg. From 1705 onward, all other portions of Brunswick-Lüneburg except Wolfenbüttel had been held by the Prince of Calenberg and Celle, i.e. the Elector of Hanover, but the Wolfenbüttel line retained its independence from Hanover. The Wolfenbüttel principality had for the period from 1807 to 1813 been held as part of the Kingdom of Westphalia; the Congress turned it into an independent country under the name Duchy of Brunswick. The underage Duke Charles, the eldest son of Duke Frederick William, was put under the guardianship of George IV, the Prince Regent of the United Kingdom and Hanover. First, the young duke had a dispute over the date of his majority. In 1827, Charles declared some of the laws made during his minority invalid, which caused conflicts.
After the German Confederation intervened, Charles was forced to accept those laws. His administration was considered misguided. In the aftermath of the July Revolution in 1830, Charles had to abdicate, his absolutist governing style had alienated the nobil
The magnetic moment is the magnetic strength and orientation of a magnet or other object that produces a magnetic field. Examples of objects that have magnetic moments include: loops of electric current, permanent magnets, elementary particles, various molecules, many astronomical objects. More the term magnetic moment refers to a system's magnetic dipole moment, the component of the magnetic moment that can be represented by an equivalent magnetic dipole: a magnetic north and south pole separated by a small distance; the magnetic dipole component is sufficient for large enough distances. Higher order terms may be needed in addition to the dipole moment for extended objects; the magnetic dipole moment of an object is defined in terms of the torque that object experiences in a given magnetic field. The same applied magnetic field creates larger torques on objects with larger magnetic moments; the strength of this torque depends not only on the magnitude of the magnetic moment but on its orientation relative to the direction of the magnetic field.
The magnetic moment may be considered, therefore. The direction of the magnetic moment points from the south to north pole of the magnet; the magnetic field of a magnetic dipole is proportional to its magnetic dipole moment. The dipole component of an object's magnetic field is symmetric about the direction of its magnetic dipole moment, decreases as the inverse cube of the distance from the object; the magnetic moment can be defined as a vector relating the aligning torque on the object from an externally applied magnetic field to the field vector itself. The relationship is given by: τ = m × B where τ is the torque acting on the dipole, B is the external magnetic field, m is the magnetic moment; this definition is based on how one could, in principle, measure the magnetic moment of an unknown sample. For a current loop, this definition leads to the magnitude of the magnetic dipole moment equaling the product of the current times the area of the loop. Further, this definition allows the calculation of the expected magnetic moment for any known macroscopic current distribution.
An alternative definition is useful for thermodynamics calculations of the magnetic moment. In this definition, the magnetic dipole moment of a system is the negative gradient of its intrinsic energy, with respect to external magnetic field: m = − x ^ ∂ U i n t ∂ B x − y ^ ∂ U i n t ∂ B y − z ^ ∂ U i n t ∂ B z. Generically, the intrinsic energy includes the self-field energy of the system plus the energy of the internal workings of the system. For example, for a hydrogen atom in a 2p state in an external field, the self-field energy is negligible, so the internal energy is the eigenenergy of the 2p state, which includes Coulomb potential energy and the kinetic energy of the electron; the interaction-field energy between the internal dipoles and external fields is not part of this internal energy. The unit for magnetic moment in International System of Units base units is A⋅m2, where A is ampere and m is meter; this unit has equivalents in other SI derived units including: A ⋅ m 2 = N ⋅ m T = J T, where N is newton, T is tesla, J is joule.
Although torque and energy are dimensionally equivalent, torques are never expressed in units of energy. In the CGS system, there are several different sets of electromagnetism units, of which the main ones are ESU, EMU. Among these, there are two alternative units of magnetic dipole moment: 1 statA ⋅ cm 2 = 3.33564095 × 10 − 14 A ⋅ m 2 1 erg G = 10 − 3 A ⋅ m 2,where statA is statamperes, cm is centimeters, erg is ergs, G is gauss. The ratio of these two non-equivalent CGS units is equal to the speed of light in free space, expressed in cm⋅s−1. All formula
Guglielmo Marconi, 1st Marquis of Marconi was an Italian inventor and electrical engineer, known for his pioneering work on long-distance radio transmission, development of Marconi's law, a radio telegraph system. He is credited as the inventor of radio, he shared the 1909 Nobel Prize in Physics with Karl Ferdinand Braun "in recognition of their contributions to the development of wireless telegraphy". Marconi was an entrepreneur and founder of The Wireless Telegraph & Signal Company in the United Kingdom in 1897, he succeeded in making an engineering and commercial success of radio by innovating and building on the work of previous experimenters and physicists. In 1929, Marconi was ennobled as a Marchese by King Victor Emmanuel III of Italy, and, in 1931, he set up the Vatican Radio for Pope Pius XI. Marconi was born into the Italian nobility as Guglielmo Giovanni Maria Marconi in Bologna on 25 April 1874, the second son of Giuseppe Marconi and his Irish/Scot wife Annie Jameson. Marconi had a brother, a stepbrother, Luigi.
Between the ages of two and six and his elder brother Alfonso lived with their mother in the English town of Bedford. Marconi did not go on to formal higher education. Instead, he learned chemistry and physics at home from a series of private tutors hired by his parents, his family hired additional tutors for Guglielmo in the winter when they would leave Bologna for the warmer climate of Tuscany or Florence. Marconi noted an important mentor was professor Vincenzo Rosa, a high school physics teacher in Livorno. Rosa taught the 17-year-old Marconi the basics of physical phenomena as well as new theories on electricity. At the age of 18 back in Bologna Marconi became acquainted with University of Bologna physicist Augusto Righi, who had done research on Heinrich Hertz's work. Righi permitted Marconi to attend lectures at the university and to use the University's laboratory and library. From youth, Marconi was interested in electricity. In the early 1890s, he began working on the idea of "wireless telegraphy"—i.e. the transmission of telegraph messages without connecting wires as used by the electric telegraph.
This was not a new idea. A new development came from Heinrich Hertz, who, in 1888, demonstrated that one could produce and detect electromagnetic radiation. At the time, this radiation was called "Hertzian" waves, is now referred to as radio waves. There was a great deal of interest in radio waves in the physics community, but this interest was in the scientific phenomenon, not in its potential as a communication method. Physicists looked on radio waves as an invisible form of light that could only travel along a line of sight path, limiting its range to the visual horizon like existing forms of visual signaling. Hertz's death in 1894 brought published reviews of his earlier discoveries including a demonstration on the transmission and detection of radio waves by the British physicist Oliver Lodge and an article about Hertz's work by Augusto Righi. Righi's article renewed Marconi's interest in developing a wireless telegraphy system based on radio waves, a line of inquiry that Marconi noted that other inventors did not seem to be pursuing.
At the age of 20, Marconi began to conduct experiments in radio waves, building much of his own equipment in the attic of his home at the Villa Griffone in Pontecchio, Italy with the help of his butler Mignani. Marconi built on Hertz's original experiments and, at the suggestion of Righi, began using a coherer, an early detector based on the 1890 findings of French physicist Edouard Branly and used in Lodge's experiments, that changed resistance when exposed to radio waves. In the summer of 1894, he built a storm alarm made up of a battery, a coherer, an electric bell, which went off when it picked up the radio waves generated by lightning. Late one night, in December 1894, Marconi demonstrated a radio transmitter and receiver to his mother, a set-up that made a bell ring on the other side of the room by pushing a telegraphic button on a bench. Supported by his father, Marconi continued to read through the literature and picked up on the ideas of physicists who were experimenting with radio waves.
He developed devices, such as portable transmitters and receiver systems, that could work over long distances, turning what was a laboratory experiment into a useful communication system. Marconi came up with a functional system with many components: A simple oscillator or spark-producing radio transmitter. In the summer of 1895, Marconi moved his experiments outdoors on his father's estate in Bologna, he tried different arrangements and shapes of antenna bu