|
Ottaviano Fabrizio Mossotti
Ottaviano-Fabrizio Mossotti (18 April 1791 – 20 March 1863) was an Italian physicist who was exiled from Italy for his liberal ideas. During the First Italian War of Independence he led a "battalion of students," part of a delegation from the Grand Duchy of Tuscany. He later taught astronomy and physics at the University of Buenos Aires. His name is associated with a type of multiple-element lens for correcting spherical aberration and coma, but not chromatic aberration. His studies on dielectrics led to important results: the Clausius-Mossotti formula is partly named after him, and his views on dielectric behavior helped lead James Clerk Maxwell to devise his theory of the displacement current, which led in turn to the theoretical prediction of electromagnetic waves. Mossotti was chair of experimental physics in Buenos Aires (1827–1835) and taught numerous Argentinian physicians his views on dielectrics, thereby becoming influential on the Argentine-German neurobiological ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Novara
Novara (, Novarese: ) is the capital city of the province of Novara in the Piedmont region in northwest Italy, to the west of Milan. With 101,916 inhabitants (on 1 January 2021), it is the second most populous city in Piedmont after Turin. It is an important crossroads for commercial traffic along the routes from Milan to Turin and from Genoa to Switzerland. Novara lies between the rivers Agogna and Terdoppio in northeastern Piedmont, from Milan and from Turin. History Novara was founded around 89 BC by the Romans, when the local Gauls obtained the Roman citizenship. Its name is formed from ''Nov'', meaning "new", and ''Aria'', the name the Cisalpine Gauls used for the surrounding region. Ancient ''Novaria'', which dates to the time of the Ligures and the Celts, was a municipium and was situated on the road from Vercellae (Vercelli) to (Mediolanum) Milan. Its position on perpendicular roads (still intact today) dates to the time of the Romans. After the city was destroyed in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coma (optics)
In optics (especially telescopes), the coma (), or comatic aberration, in an optical system refers to aberration inherent to certain optical designs or due to imperfection in the lens or other components that results in off-axis point sources such as stars appearing distorted, appearing to have a tail (coma) like a comet. Specifically, coma is defined as a variation in magnification over the entrance pupil. In refractive or diffractive optical systems, especially those imaging a wide spectral range, coma can be a function of wavelength, in which case it is a form of chromatic aberration. Overview Coma is an inherent property of telescopes using parabolic mirrors. Unlike a spherical mirror, a bundle of parallel rays parallel to the optical axis will be perfectly focused to a point (the mirror is free of spherical aberration), no matter where they strike the mirror. However, this is only true if the rays are parallel to the axis of the parabola. When the incoming rays strike the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1863 Deaths
Events January–March * January 1 – Abraham Lincoln signs the Emancipation Proclamation during the third year of the American Civil War, making the abolition of slavery in the Confederate states an official war goal. It proclaims the freedom of 3.1 million of the nation's four million slaves and immediately frees 50,000 of them, with the rest freed as Union armies advance. * January 2 – Lucius Tar Painting Master Company (''Teerfarbenfabrik Meirter Lucius''), predecessor of Hoechst, as a worldwide chemical manufacturing brand, founded in a suburb of Frankfurt am Main, Germany. * January 4 – The New Apostolic Church, a Christian and chiliastic church, is established in Hamburg, Germany. * January 7 – In the Swiss canton of Ticino, the village of Bedretto is partly destroyed and 29 killed, by an avalanche. * January 8 ** The Yorkshire County Cricket Club is founded at the Adelphi Hotel, in Sheffield, England. ** American Civil War &ndash ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1791 Births
Events January–March * January 1 – Austrian composer Joseph Haydn arrives in England, to perform a series of concerts. * January 2 – Northwest Indian War: Big Bottom Massacre – The war begins in the Ohio Country, with this massacre. * January 12 – Holy Roman troops reenter Liège, heralding the end of the Liège Revolution, and the restoration of its Prince-Bishops. * January 25 – The British Parliament passes the Constitutional Act 1791, splitting the old province of Quebec into Upper and Lower Canada. * February 8 – The Bank of the United States, based in Philadelphia, is incorporated by the federal government with a 20-year charter and started with $10,000,000 capital.''Harper's Encyclopaedia of United States History from 458 A. D. to 1909'', ed. by Benson John Lossing and, Woodrow Wilson (Harper & Brothers, 1910) p169 * February 21 – The United States opens diplomatic relations with Portugal. * March 2 – Fr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fundamental Forces
In physics, the fundamental interactions, also known as fundamental forces, are the interactions that do not appear to be reducible to more basic interactions. There are four fundamental interactions known to exist: the gravitational and electromagnetic interactions, which produce significant long-range forces whose effects can be seen directly in everyday life, and the strong and weak interactions, which produce forces at minuscule, subatomic distances and govern nuclear interactions. Some scientists hypothesize that a fifth force might exist, but these hypotheses remain speculative. Each of the known fundamental interactions can be described mathematically as a ''field''. The gravitational force is attributed to the curvature of spacetime, described by Einstein's general theory of relativity. The other three are discrete quantum fields, and their interactions are mediated by elementary particles described by the Standard Model of particle physics. Within the Standard Mode ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hendrik Antoon Lorentz
Hendrik Antoon Lorentz (; 18 July 1853 – 4 February 1928) was a Dutch physicist who shared the 1902 Nobel Prize in Physics with Pieter Zeeman for the discovery and theoretical explanation of the Zeeman effect. He also derived the Lorentz transformation underpinning Albert Einstein's special theory of relativity, as well as the Lorentz force, which describes the combined electric and magnetic forces acting on a charged particle in an electromagnetic field. Lorentz was also responsible for the Lorentz oscillator model, a classical model used to describe the anomalous dispersion observed in dielectric materials when the driving frequency of the electric field was near the resonant frequency, resulting in abnormal refractive indices. According to the biography published by the Nobel Foundation, "It may well be said that Lorentz was regarded by all theoretical physicists as the world's leading spirit, who completed what was left unfinished by his predecessors and prepared the g ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hologram
Holography is a technique that enables a wavefront to be recorded and later re-constructed. Holography is best known as a method of generating real three-dimensional images, but it also has a wide range of other Holography#Applications, applications. In principle, it is possible to make a hologram for any type of Holography#Non-optical holography, wave. A hologram is made by superimposing a second wavefront (normally called the reference beam) on the wavefront of interest, thereby generating an interference pattern which is recorded on a physical medium. When only the second wavefront illuminates the interference pattern, it is diffracted to recreate the original wavefront. Holograms can also be Computer-generated holography, computer-generated by modelling the two wavefronts and adding them together digitally. The resulting digital image is then printed onto a suitable mask or film and illuminated by a suitable source to reconstruct the wavefront of interest. Overview and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Standing Wave
In physics, a standing wave, also known as a stationary wave, is a wave that oscillates in time but whose peak amplitude profile does not move in space. The peak amplitude of the wave oscillations at any point in space is constant with respect to time, and the oscillations at different points throughout the wave are in phase. The locations at which the absolute value of the amplitude is minimum are called nodes, and the locations where the absolute value of the amplitude is maximum are called antinodes. Standing waves were first noticed by Michael Faraday in 1831. Faraday observed standing waves on the surface of a liquid in a vibrating container. Franz Melde coined the term "standing wave" (German: ''stehende Welle'' or ''Stehwelle'') around 1860 and demonstrated the phenomenon in his classic experiment with vibrating strings. This phenomenon can occur because the medium is moving in the direction opposite to the movement of the wave, or it can arise in a stationary medium ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neurobiology
Neuroscience is the scientific study of the nervous system (the brain, spinal cord, and peripheral nervous system), its functions and disorders. It is a multidisciplinary science that combines physiology, anatomy, molecular biology, developmental biology, cytology, psychology, physics, computer science, chemistry, medicine, statistics, and mathematical modeling to understand the fundamental and emergent properties of neurons, glia and neural circuits. The understanding of the biological basis of learning, memory, behavior, perception, and consciousness has been described by Eric Kandel as the "epic challenge" of the biological sciences. The scope of neuroscience has broadened over time to include different approaches used to study the nervous system at different scales. The techniques used by neuroscientists have expanded enormously, from molecular and cellular studies of individual neurons to imaging of sensory, motor and cognitive tasks in the brain. History The earliest ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dielectric
In electromagnetism, a dielectric (or dielectric medium) is an electrical insulator that can be polarised by an applied electric field. When a dielectric material is placed in an electric field, electric charges do not flow through the material as they do in an electrical conductor, because they have no loosely bound, or free, electrons that may drift through the material, but instead they shift, only slightly, from their average equilibrium positions, causing dielectric polarisation. Because of dielectric polarisation, positive charges are displaced in the direction of the field and negative charges shift in the direction opposite to the field (for example, if the field is moving parallel to the positive ''x'' axis, the negative charges will shift in the negative ''x'' direction). This creates an internal electric field that reduces the overall field within the dielectric itself. If a dielectric is composed of weakly bonded molecules, those molecules not only become polaris ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electromagnetic Waves
In physics, electromagnetic radiation (EMR) consists of waves of the electromagnetic (EM) field, which propagate through space and carry momentum and electromagnetic radiant energy. It includes radio waves, microwaves, infrared, (visible) light, ultraviolet, X-rays, and gamma rays. All of these waves form part of the electromagnetic spectrum. Classically, electromagnetic radiation consists of electromagnetic waves, which are synchronized oscillations of electric and magnetic fields. Depending on the frequency of oscillation, different wavelengths of electromagnetic spectrum are produced. In a vacuum, electromagnetic waves travel at the speed of light, commonly denoted ''c''. In homogeneous, isotropic media, the oscillations of the two fields are perpendicular to each other and perpendicular to the direction of energy and wave propagation, forming a transverse wave. The position of an electromagnetic wave within the electromagnetic spectrum can be characterized by either its ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Displacement Current
In electromagnetism, displacement current density is the quantity appearing in Maxwell's equations that is defined in terms of the rate of change of , the electric displacement field. Displacement current density has the same units as electric current density, and it is a source of the magnetic field just as actual current is. However it is not an electric current of moving charges, but a time-varying electric field. In physical materials (as opposed to vacuum), there is also a contribution from the slight motion of charges bound in atoms, called dielectric polarization. The idea was conceived by James Clerk Maxwell in his 1861 paper On Physical Lines of Force, Part III' in connection with the displacement of electric particles in a dielectric medium. Maxwell added displacement current to the electric current term in Ampère's Circuital Law. In his 1865 paper A Dynamical Theory of the Electromagnetic Field Maxwell used this amended version of Ampère's Circuital Law to de ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
