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Fizeau's Measurement Of The Speed Of Light In Air
In 1848−49, Hippolyte Fizeau used a toothed wheel apparatus to perform an absolute measurement of the speed of light in air. Subsequent experiments performed by Marie Alfred Cornu in 1872–76 improved the methodology and made a more accurate measurement. Fizeau's determination of the speed of light In 1848–49, Hippolyte Fizeau determined the speed of light using an intense light source at the bell tower of his father's holiday home in Suresnes, and a mirror 8,633 meters away on Montmartre. The light source was interrupted by a rotating cogwheel with 720 notches that could be rotated at a variable speed several times a second. (Figure 1) Fizeau increased the rotation speed of the cogwheel until light passing through one notch of the cogwheel would be completely eclipsed by the adjacent tooth. At 12.6 rotations per second, the light was eclipsed. At twice this speed (25.2 rotations per second), it was again visible as it passed through the next notch. At 3 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hippolyte Fizeau
Armand Hippolyte Louis Fizeau FRS FRSE MIF (; 23 September 181918 September 1896) was a French physicist, best known for measuring the speed of light in the namesake 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 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 8 kilometers away. The beam passed through the gaps between teeth of a rapidly rotating wheel. The speed of the wheel was increased until the returning light hit the next tooth and could not be seen. Fizeau calc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Speed Of Light
The speed of light in vacuum, commonly denoted , is a universal physical constant that is important in many areas of physics. The speed of light is exactly equal to ). According to the special theory of relativity, is the upper limit for the speed at which conventional matter or energy (and thus any signal carrying information) can travel through space. All forms of electromagnetic radiation, including visible light, travel at the speed of light. For many practical purposes, light and other electromagnetic waves will appear to propagate instantaneously, but for long distances and very sensitive measurements, their finite speed has noticeable effects. Starlight viewed on Earth left the stars many years ago, allowing humans to study the history of the universe by viewing distant objects. When communicating with distant space probes, it can take minutes to hours for signals to travel from Earth to the spacecraft and vice versa. In computing, the speed of light fixes th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Marie Alfred Cornu
Marie Alfred Cornu (; 6 March 1841 – 12 April 1902) was a French physicist. The French generally refer to him as Alfred Cornu. Life Cornu was born at Orléans to François Cornu and Sophie Poinsellier. He was educated at the École polytechnique and the École des mines. Upon the death of Émile Verdet in 1866, Cornu became, in 1867, Verdet's successor as professor of experimental physics at the École polytechnique, where he remained throughout his life. Although he made various excursions into other branches of physical science, undertaking, for example, with Jean-Baptistin Baille about 1870 a repetition of Cavendish's experiment for determining the gravitational constant ''G'', his original work was mainly concerned with optics and spectroscopy. In particular he carried out a classical redetermination of the speed of light by A. H. L. Fizeau's method (see Fizeau-Foucault Apparatus), introducing various improvements in the apparatus, which added greatly to the accuracy of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fizeau
Armand Hippolyte Louis Fizeau FRS FRSE MIF (; 23 September 181918 September 1896) was a French physicist, best known for measuring the speed of light in the namesake 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 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 8 kilometers away. The beam passed through the gaps between teeth of a rapidly rotating wheel. The speed of the wheel was increased until the returning light hit the next tooth and could not be seen. Fizeau calcu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Suresnes
Suresnes () is a Communes of France, commune in the western suburbs of Paris, Île-de-France. Located in Hauts-de-Seine, from the centre of Paris, it had a population of 49,145 as of 2016. The nearest communes are Nanterre, Puteaux, Rueil-Malmaison, Saint-Cloud and Boulogne-Billancourt. It is served by two stops on Île-de-France tramway Line 2 and Suresnes–Mont-Valérien station on the Transilien network, both giving access to La Défense and its RER A and Paris Métro Line 1 services. Suresnes's landmarks include the Mémorial de la France combattante and Suresnes American Cemetery and Memorial below Fort Mont-Valérien, as well as Foch Hospital in the town centre. History Fort Mont-Valérien (along with its Mémorial de la France combattante) is situated in the commune, as is Suresnes American Cemetery and Memorial. Suresnes has an elegant view of Paris and the Eiffel Tower, as does neighbouring Saint-Cloud. Robert Ormond Maugham, the father of W. Somerset Maugham, built a � ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Montmartre
Montmartre ( , ) is a large hill in Paris's northern 18th arrondissement. It is high and gives its name to the surrounding district, part of the Right Bank. The historic district established by the City of Paris in 1995 is bordered by Rue Caulaincourt and Rue Custine on the north, the Rue de Clignancourt on the east and the Boulevard de Clichy and Boulevard de Rochechouart to the south, containing . Montmartre is primarily known for its artistic history, the white-domed Basilica of the Sacré-Cœur on its summit, as well as a nightclub district. The other church on the hill, Saint Pierre de Montmartre, built in 1147, was the church of the prestigious Montmartre Abbey. On 15 August 1534, Saint Ignatius of Loyola, Saint Francis Xavier and five other companions bound themselves by vows in the Martyrium of Saint Denis, 11 Rue Yvonne Le Tac, the first step in the creation of the Jesuits. Near the end of the 19th century and at the beginning of the 20th, during the Belle Époq ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chronograph Chart Used In Cornu's Speed Of Light Determination
A chronograph is a specific type of watch that is used as a stopwatch combined with a display watch. A basic chronograph has an independent sweep second hand and a minute sub-dial; it can be started, stopped, and returned to zero by successive pressure on the stem. More complex chronographs use additional complications and can have multiple sub-dials to measure seconds, minutes, hours and even fractions of a second. In addition, many modern chronographs use moveable bezels as tachymeters for rapid calculations of speed or distance. Louis Moinet invented the chronograph in 1816 for use in tracking astronomical objects. Chronographs were also used heavily in artillery fire in the mid to late 1800s. More modern uses of chronographs involve aircraft piloting, auto racing, diving and submarine maneuvering. Since the 1980s, the term ''chronograph'' has also been applied to all digital watches that incorporate a stopwatch function. History The term ''chronograph'' comes from the G ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paris Observatory
The Paris Observatory (french: Observatoire de Paris ), a research institution of the Paris Sciences et Lettres University, is the foremost astronomical observatory of France, and one of the largest astronomical centers in the world. Its historic building is on the Left Bank of the Seine in central Paris, but most of the staff work on a satellite campus in Meudon, a suburb southwest of Paris. The Paris Observatory was founded in 1667. Construction was completed by the early 1670s and coincided with a major push for increased science, and the founding of the Royal Academy of Sciences. King Louis XIV's minister of finance organized a "scientific powerhouse" to increase understanding of astronomy, maritime navigation, and science in general. Through the centuries the Paris Observatory has continued in support of astronomical activities, and in the 21st century connects multiple sites and organizations, supporting astronomy and science, past and present. Constitution Adminis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Urbain Le Verrier
Urbain Jean Joseph Le Verrier FRS (FOR) HFRSE (; 11 March 1811 – 23 September 1877) was a French astronomer and mathematician who specialized in celestial mechanics and is best known for predicting the existence and position of Neptune using only mathematics. The calculations were made to explain discrepancies with Uranus's orbit and the laws of Kepler and Newton. Le Verrier sent the coordinates to Johann Gottfried Galle in Berlin, asking him to verify. Galle found Neptune in the same night he received Le Verrier's letter, within 1° of the predicted position. The discovery of Neptune is widely regarded as a dramatic validation of celestial mechanics, and is one of the most remarkable moments of 19th-century science. Biography Early years Le Verrier was born at Saint-Lô, Manche, France, in a modest bourgeois family, his parents being, Louis-Baptiste Le Verrier and Marie-Jeanne-Josephine-Pauline de Baudre. He studied at École Polytechnique. He briefly studied chemistry ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Speed Of Light
The speed of light in vacuum, commonly denoted , is a universal physical constant that is important in many areas of physics. The speed of light is exactly equal to ). According to the special theory of relativity, is the upper limit for the speed at which conventional matter or energy (and thus any signal carrying information) can travel through space. All forms of electromagnetic radiation, including visible light, travel at the speed of light. For many practical purposes, light and other electromagnetic waves will appear to propagate instantaneously, but for long distances and very sensitive measurements, their finite speed has noticeable effects. Starlight viewed on Earth left the stars many years ago, allowing humans to study the history of the universe by viewing distant objects. When communicating with distant space probes, it can take minutes to hours for signals to travel from Earth to the spacecraft and vice versa. In computing, the speed of light fixes th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fizeau Experiment
The Fizeau experiment was carried out by Hippolyte Fizeau in 1851 to measure the relative speeds of light in moving water. Fizeau used a special interferometer arrangement to measure the effect of movement of a medium upon the speed of light. According to the theories prevailing at the time, light traveling through a moving medium would be dragged along by the medium, so that the measured speed of the light would be a simple sum of its speed ''through'' the medium plus the speed ''of'' the medium. Fizeau indeed detected a dragging effect, but the magnitude of the effect that he observed was far lower than expected. When he repeated the experiment with air in place of water he observed no effect. His results seemingly supported the partial aether-drag hypothesis of Fresnel, a situation that was disconcerting to most physicists. Over half a century passed before a satisfactory explanation of Fizeau's unexpected measurement was developed with the advent of Albert Einstein's theor ... [...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, suggest ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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