|
The history of electromagnetic theory begins with ancient measures to deal with atmospheric electricity, in particular lightning.〔Bruno Kolbe, Francis ed Legge, Joseph Skellon, tr., "''(An Introduction to Electricity )''". Kegan Paul, Trench, Trübner, 1908. 429 pages. (Page 391 ). (cf., "() ''high poles covered with copper plates and with gilded tops were erected 'to break the stones coming from on high'.'' J. Dümichen, Baugeschichte des Dendera-Tempels, Strassburg, 1877")〕 People then had little understanding of electricity, and were unable to scientifically explain the phenomena.〔Urbanitzky, A. v., & Wormell, R. (1886). (Electricity in the service of man: a popular and practical treatise on the applications of electricity in modern life ). London: Cassell &.〕 In the 19th century there was a unification of the history of electric theory with the history of magnetic theory. It became clear that electricity should be treated jointly with magnetism, because wherever charges are in motion electric current results and, magnetism is due to electric current.〔Lyons, T. A. (1901). ''A treatise on electromagnetic phenomena, and on the compass and its deviations aboard ship. Mathematical, theoretical, and practical''. New York: J. Wiley & Sons.〕 The source term for electric field is electric charge where as that for magnetic field is electric current( charges in motion). Magnetism was not fully explained until the idea of magnetic induction was developed.〔''Encyclopædia Britannica'' (1890). New York: The Henry G. Allen Company.〕 Electricity was not fully explained until the idea of electric charge was developed. ==Ancient and classical history== The knowledge of static electricity dates back to the earliest civilizations, but for millennia it remained merely an interesting and mystifying phenomenon, without a theory to explain its behavior and often confused with magnetism. The ancients were acquainted with rather curious properties possessed by two minerals, amber (, ''electron'') and magnetic iron ore (Greek: Μάγνης λίθος, ''Magnes lithos'', "the Magnesian stone, lodestone"). Amber, when rubbed, attracts light bodies; magnetic iron ore has the power of attracting iron.〔Whittaker, E. T. (1910). A history of the theories of aether and electricity from the age of Descartes to the close of the 19th century. Dublin University Press series. London: Longmans, Green and Co.; ().〕 Based on his find of an Olmec hematite artifact in Central America, the American astronomer John Carlson has suggested that "the Olmec may have discovered and used the geomagnetic lodestone compass earlier than 1000 BC". If true, this "predates the Chinese discovery of the geomagnetic lodestone compass by more than a millennium".〔Carlson, John B. (1975) "Lodestone Compass: Chinese or Olmec Primacy?: Multidisciplinary analysis of an Olmec hematite artifact from San Lorenzo, Veracruz, Mexico", ''Science'', 189 (4205 : 5 September), p. 753-760, . p. 753–760〕〔(Lodestone Compass: Chinese or Olmec Primacy?: Multidisciplinary analysis of an Olmec hematite artifact from San Lorenzo, Veracruz, Mexico - Carlson 189 (4205): 753 - Science )〕 Carlson speculates that the Olmecs may have used similar artifacts as a directional device for astrological or geomantic purposes, or to orient their temples, the dwellings of the living or the interments of the dead. The earliest Chinese literature reference to ''magnetism'' lies in a 4th-century BC book called ''Book of the Devil Valley Master'' (鬼谷子): "The lodestone makes iron come or it attracts it."〔Li Shu-hua, p. 175〕 Long before any knowledge of electromagnetism existed, people were aware of the effects of electricity. Lightning and other manifestations of electricity such as St. Elmo's fire were known in ancient times, but it was not understood that these phenomena had a common origin.〔Maver, William, Jr.: "Electricity, its History and Progress", (The Encyclopedia Americana; a library of universal knowledge, vol. X, pp. 172ff ). (1918). New York: Encyclopedia Americana Corp.〕 Ancient Egyptians were aware of shocks when interacting with electric fish (such as the electric catfish) or other animals (such as electric eels).〔Heinrich Karl Brugsch-Bey and Henry Danby Seymour, "''(A History of Egypt Under the Pharaohs )''". J. Murray, 1881. Page 422. (cf., (the symbol of a )'' 'serpent' is rather a fish, which still serves, in the Coptic language, to designate the electric fish'' ())〕 The shocks from animals were apparent to observers since pre-history by a variety of peoples that came into contact with them. Texts from 2750 BC by the ancient Egyptians referred to these fish as "thunderer of the Nile" and saw them as the "protectors" of all the other fish.〔 Another possible approach to the discovery of the identity of lightning and electricity from any other source, is to be attributed to the Arabs, who before the 15th century used the same Arabic word for lightning (''barq'') and the electric ray.〔 Thales of Miletus, writing at around 600 BC, noted that rubbing fur on various substances such as amber would cause them to attract specks of dust and other light objects.〔Seeman, Bernard and Barry, James E. ''The Story of Electricity and Magnetism'', Harvey House 1967, p. 19〕 Thales wrote on the effect now known as static electricity. The Greeks noted that if they rubbed the amber for long enough they could even get an electric spark to jump. The electrostatic phenomena was again reported millennia later by Roman and Arabic naturalists and physicians. Several ancient writers, such as Pliny the Elder and Scribonius Largus, attested to the numbing effect of electric shocks delivered by catfish and torpedo rays. Pliny in his books writes: "The ancient Tuscans by their learning hold that there are nine gods that send forth lightning and those of eleven sorts." This was in general the early pagan idea of lightning.〔 The ancients held some concept that shocks could travel along conducting objects.〔 〕 Patients suffering from ailments such as gout or headache were directed to touch electric fish in the hope that the powerful jolt might cure them.〔 〕 A number of objects found in Iraq in 1938 dated to the early centuries AD (Sassanid Mesopotamia), called the Baghdad Battery, resembles a galvanic cell and is believed by some to have been used for electroplating.〔(Riddle of 'Baghdad's batteries' ). BBC News.〕 The claims are controversial because of supporting evidence and theories for the uses of the artifacts,〔After the Second World War, Willard Gray demonstrated current production by a reconstruction of the inferred battery design when filled with grape juice. W. Jansen experimented with 1,4-Benzoquinone (some beetles produce quinones) and vinegar in a cell and got satisfactory performance.〕〔An alternative, but still electrical explanation was offered by Paul Keyser. It was suggested that a priest or healer, using an iron spatula to compound a vinegar based potion in a copper vessel, may have felt an electrical tingle and used the phenomenon either for electro-acupuncture, or to amaze supplicants by electrifying a metal statue.〕 physical evidence on the objects conducive for electrical functions,〔Copper and iron form an electrochemical couple, so that in the presence of any electrolyte, an electric potential (voltage) will be produced. König had observed a number of very fine silver objects from ancient Iraq which were plated with very thin layers of gold, and speculated that they were electroplated using batteries of these "cells".〕 and if they were electrical in nature. As a result the nature of these objects is based on speculation, and the function of these artifacts remains in doubt.〔Corder, Gregory, "Using an Unconventional History of the Battery to engage students and explore the importance of evidence", Virginia Journal of Science Education 1〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「History of electromagnetic theory」の詳細全文を読む スポンサード リンク
|