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Hippolyte Fizeau
Armand Hippolyte Louis Fizeau (; 23 September 1819 – 18 September 1896) was a French physicist who, in 1849, measured the speed of light to within 5% accuracy. In 1851, he measured the speed of light in moving water in an experiment known as the Fizeau experiment. Biography Fizeau was born in Paris to Louis and Beatrice Fizeau. He married into the de Jussieu botanical family. His earliest work was concerned with improvements in photographic processes. Following suggestions by François Arago, Léon Foucault and Fizeau collaborated in a series of investigations on the Interference (wave propagation), interference of light and heat. In 1848, he predicted the redshifting of electromagnetic waves. In 1849, Fizeau calculated a value for the speed of light to a better precision than the previous value determined by Ole Rømer in 1676. He used a beam of light reflected from a mirror 8633 meters away. The beam passed through the gaps between the teeth of a rapidly rotating wheel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eugène Pirou
Louis Eugène Pirou (26 September 1841 – 30 September 1909) was a French photographer and filmmaker, known primarily for his portraits of celebrities and scenes from the Paris Commune. He was awarded a gold medal at the Exposition Universelle of 1889. Life and work He owned numerous studios in Paris, mostly on the Boulevard Saint-Germain, but he also operated one at an old evangelical mission on the Rue Royale. That one was sold to a photographer named Arthur Herbert, in 1889, with permission to use Pirou's name. In 1898, Herbert sold the studio to the brothers Georges and Oscar Mascré (1865-1943), who continued to use Pirou's name without his permission. Pirou lost a complicated lawsuit against the brothers, who compounded the fraud by referring to the studio as "Otto-Pirou", in reference to Otto Wegener, a Swedish-born photographer who was also not associated with them.Camille Blot-Wellens, "Eugène Pirou, portraitiste de la Belle Époque", in ''Revue de la Bibliothèq ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Léon Foucault
Jean Bernard Léon Foucault (, ; ; 18 September 1819 – 11 February 1868) was a French physicist best known for his demonstration of the Foucault pendulum, a device demonstrating the effect of Earth's rotation. He also made an early measurement of the speed of light, discovered eddy currents, and is credited with naming the gyroscope. Early years The son of a publisher, Foucault was born in Paris on 18 September 1819. After an education received chiefly at home, he studied medicine, which he abandoned in favour of physics due to a blood phobia. He first directed his attention to the improvement of Louis Daguerre's photographic processes. For three years he was experimental assistant to Alfred Donné (1801–1878) in his course of lectures on microscopic anatomy. With Hippolyte Fizeau he carried out a series of investigations on the intensity of the light of the sun, as compared with that of carbon in the arc lamp, and of lime in the flame of the oxyhydrogen blowpipe; on the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1889 World's Fair
The of 1889 (), better known in English as the 1889 Paris Exposition, was a world's fair held in Paris, France, from 6 May to 31 October 1889. It was the fifth of ten major expositions held in the city between 1855 and 1937. It attracted more than thirty-two million visitors. The most famous structure created for the exposition, and still remaining, is the Eiffel Tower. Organization The exposition was held to celebrate the 100th anniversary of the Storming of the Bastille, which marked the beginning of French Revolution, and was also seen as a way to stimulate the economy and pull France out of an economic recession. The exposition attracted 61,722 official exhibitors, of whom twenty-five thousand were from outside of France. Admission price Admission to the exposition cost forty centimes, at a time when the price of an "economy" plate of meat and vegetables in a Paris cafe was ten centimes. Visitors paid an additional price for several of the exposition's most popular att ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of The 72 Names On The Eiffel Tower
On the Eiffel Tower, 72 names of France, French men (scientists, engineers, and mathematicians) are engraved in recognition of their contributions. Gustave Eiffel chose this "invocation of science" because of his concern over the Eiffel Tower#Artists' protest, protests against the tower, and chose names of those who had distinguished themselves since 1789. The engravings are found on the sides of the tower under the first balcony, in letters about tall, and were originally painted in gold. The engraving was painted over at the beginning of the 20th century and restored in 1986–87 by Société Nouvelle d'exploitation de la Tour Eiffel, the company that the city of Paris contracts to operate the Tower. The repainting of 2010–11 restored the letters to their original gold colour. There are also names of the engineers who helped build the Tower and design its architecture on a plaque on the top of the Tower, where a laboratory was built as well. List Location The list is spl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bureau Des Longitudes
__NOTOC__ The ''Bureau des Longitudes'' () is a French scientific institution, founded by decree of 25 June 1795 and charged with the improvement of nautical navigation, standardisation of time-keeping, geodesy and astronomical observation. During the 19th century, it was responsible for synchronizing clocks across the world. It was headed during this time by François Arago and Henri Poincaré. The Bureau now functions as an academy and still meets monthly to discuss topics related to astronomy. The Bureau was founded by the National Convention after it heard a report drawn up jointly by the Committee of Navy, the Committee of Finances and the Committee of State education. Henri Grégoire had brought to the attention of the National Convention France's failing maritime power and the naval mastery of England, proposing that improvements in navigation would lay the foundations for a renaissance in naval strength. As a result, the Bureau was established with authority over the P ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Académie Des Sciences
The French Academy of Sciences (, ) is a learned society, founded in 1666 by Louis XIV at the suggestion of Jean-Baptiste Colbert, to encourage and protect the spirit of French Scientific method, scientific research. It was at the forefront of scientific developments in Europe in the 17th and 18th centuries, and is one of the earliest Academy of Sciences, Academies of Sciences. Currently headed by Patrick Flandrin (President of the academy), it is one of the five Academies of the . __TOC__ History The Academy of Sciences traces its origin to Colbert's plan to create a general academy. He chose a small group of scholars who met on 22 December 1666 in the King's library, near the present-day Bibliothèque nationale de France, Bibliothèque Nationale, and thereafter held twice-weekly working meetings there in the two rooms assigned to the group. The first 30 years of the academy's existence were relatively informal, since no statutes had as yet been laid down for the ins ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crystal
A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macroscopic single crystals are usually identifiable by their geometrical shape, consisting of flat faces with specific, characteristic orientations. The scientific study of crystals and crystal formation is known as crystallography. The process of crystal formation via mechanisms of crystal growth is called crystallization or solidification. The word ''crystal'' derives from the Ancient Greek word (), meaning both "ice" and " rock crystal", from (), "icy cold, frost". Examples of large crystals include snowflakes, diamonds, and table salt. Most inorganic solids are not crystals but polycrystals, i.e. many microscopic crystals fused together into a single solid. Polycrystals include most metals, rocks, ceramics, and ice. A third cat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermal Expansion
Thermal expansion is the tendency of matter to increase in length, area, or volume, changing its size and density, in response to an increase in temperature (usually excluding phase transitions). Substances usually contract with decreasing temperature (thermal contraction), with rare exceptions within limited temperature ranges ('' negative thermal expansion''). Temperature is a monotonic function of the average molecular kinetic energy of a substance. As energy in particles increases, they start moving faster and faster, weakening the intermolecular forces between them and therefore expanding the substance. When a substance is heated, molecules begin to vibrate and move more, usually creating more distance between themselves. The relative expansion (also called strain) divided by the change in temperature is called the material's coefficient of linear thermal expansion and generally varies with temperature. Prediction If an equation of state is available, it can be used t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Capacitor
In electrical engineering, a capacitor is a device that stores electrical energy by accumulating electric charges on two closely spaced surfaces that are insulated from each other. The capacitor was originally known as the condenser, a term still encountered in a few compound names, such as the '' condenser microphone''. It is a passive electronic component with two terminals. The utility of a capacitor depends on its capacitance. While some capacitance exists between any two electrical conductors in proximity in a circuit, a capacitor is a component designed specifically to add capacitance to some part of the circuit. The physical form and construction of practical capacitors vary widely and many types of capacitor are in common use. Most capacitors contain at least two electrical conductors, often in the form of metallic plates or surfaces separated by a dielectric medium. A conductor may be a foil, thin film, sintered bead of metal, or an electrolyte. The nonconductin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Doppler Effect
The Doppler effect (also Doppler shift) is the change in the frequency of a wave in relation to an observer who is moving relative to the source of the wave. The ''Doppler effect'' is named after the physicist Christian Doppler, who described the phenomenon in 1842. A common example of Doppler shift is the change of pitch heard when a vehicle sounding a horn approaches and recedes from an observer. Compared to the emitted frequency, the received frequency is higher during the approach, identical at the instant of passing by, and lower during the recession. When the source of the sound wave is moving towards the observer, each successive cycle of the wave is emitted from a position closer to the observer than the previous cycle. Hence, from the observer's perspective, the time between cycles is reduced, meaning the frequency is increased. Conversely, if the source of the sound wave is moving away from the observer, each cycle of the wave is emitted from a position farther from ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Foucault's Measurements Of The Speed Of Light
In 1850, Léon Foucault used a rotating mirror to perform a differential measurement of the speed of light in water versus its speed in air. In 1862, he used a similar apparatus to measure the speed of light in the air. Background In 1834, Charles Wheatstone developed a method of using a rapidly rotating mirror to study transient phenomena, and applied this method to measure the velocity of electricity in a wire and the duration of an electric spark. He communicated to François Arago the idea that his method could be adapted to a study of the speed of light. The early-to-mid 1800s were a period of intense debate on the particle-versus-wave nature of light. Although the observation of the Arago spot in 1819 may have seemed to settle the matter definitively in favor of Fresnel's wave theory of light, various concerns continued to appear to be addressed more satisfactorily by Newton's corpuscular theory. Arago expanded upon Wheatstone's concept in an 1838 publication, suggesting ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ole Rømer
Ole Christensen Rømer (; 25 September 1644 – 19 September 1710) was a Danes, Danish astronomer who, in 1676, first demonstrated that light travels at a finite speed. Rømer also invented the modern thermometer showing the temperature between two fixed points, namely the points at which water respectively boils and freezes. Rømer made his discovery regarding the speed of light while working at the Paris Observatory, Royal Observatory in Paris and studying Jupiter's moon Io (moon), Io. He estimated that light takes about 11 minutes to travel from the Sun to Earth. Using today's knowledge of the Astronomical unit, Sun-Earth distance, this would amount to a speed of light of approximately 220,000 kilometers per second, compared to today's accepted value of just under 300,000 kilometers per second. In scientific literature, alternative spellings such as "Roemer", "Römer", or "Romer" are common. Biography Rømer was born on 25 September 1644 in Aarhus to merchant and skipper ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
