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Op donderdag 26 november 2009 12:05 schreef Intrepidity het volgende:[..]
Ik twijfel niet aan het feit dat ze de temperatuur af kunnen leiden aan bepaalde factoren, maar hoe kan de link met verminderde zonneactiviteit gelegd worden? Het is niet alsof mensen toen fijn een logboekje met zonnestormen e.d. bijhielden
Toch wel! De Chinezen ontdekten deze zonnevlekken al vóór Christus.
En in Europa zijn ze gewoon geobserveerd en bijgehouden vanaf de 16e eeuw
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[edit] History
Black and white drawing showing latin script surrounding two concentric circles with two black dots inside the inner circle
A drawing of a sunspot in the Chronicles of John of Worcester
Apparent references to sunspots were made by Chinese astronomers in 28 BC (Hanshu, 27), who probably could see the largest groups of spots when the wind-borne dust filtered the sun's glare in Central Asian deserts. A large sunspot was also seen at the time of Charlemagne's death in A.D. 813. On 17 March 807 the Benedictine monk Adelmus observed a large sunspot, which was visible for eight days. Adelmus thought he was observing a transit of Mercury.[8] Sunspot activity in 1129 was described by John of Worcester. Averroes also provided a description of sunspots in the 12th century.[9] However, these early observations were misinterpreted until Galileo gave the correct explanation in 1612.
They were first observed telescopically in late 1610 by the English astronomer Thomas Harriot and Frisian astronomers Johannes and David Fabricius, who published a description in June 1611. At the latter time Galileo had been showing sunspots to astronomers in Rome, and Christoph Scheiner had probably been observing the spots for two or three months. The ensuing priority dispute between Galileo and Scheiner, neither of whom knew of the Fabricius' work, was thus as pointless as it was bitter.
Sunspots had some importance in the debate over the nature of the solar system. They showed that the Sun rotated, and their comings and goings showed that the Sun changed, contrary to Aristotle. The details of their apparent motion could not be readily explained except in the heliocentric system of Copernicus.
The cyclic variation of the number of sunspots was first observed by Heinrich Schwabe between 1826 and 1843 and led Rudolf Wolf to make systematic observations starting in 1848. The Wolf number is a measure of individual spots and spot groupings, which correlates to a number of solar observables. Also in 1848, Joseph Henry projected an image of the Sun onto a screen and determined that sunspots were cooler than the surrounding surface.[10]
Wolf also studied the historical record in an attempt to establish a database on past cyclic variations. His database extended only to 1700, although the technology and techniques for careful solar observations were first available in 1610. Gustav Spörer later suggested a 70-year period before 1716 in which sunspots were rarely observed as the reason for Wolf's inability to extend the cycles into the seventeenth century. The economist William Stanley Jevons suggested that there is a relationship between sunspots and business cycle crises. He reasoned that sunspots affect earth's weather, which, in turn, influences crops and, therefore, the economy.[11]
Edward Maunder later suggested that the Sun had changed from a period in which sunspots all but disappeared from the solar surface to a renewal of sunspot cycles starting in 1700. Careful studies revealed the problem not to be a lack of observational data but included references to negative observations. Adding to this understanding of the absence of solar cycles were observations of aurorae, which were absent at the same time. Even the lack of a solar corona during solar eclipses was noted prior to 1715.
Sunspots were rarely observed during the second part of 17th century in the time called the Maunder Minimum (1645–1717).
After the resumption of sunspot activity, Heinrich Schwabe in 1844 in "Astronomische Nachrichten"(Astronomical News) reported a periodic change in the number of sunspots. Since 1991, the Royal Observatory of Belgium acts as the World data center for the Sunspot Index.
Recent measurements, based also on observation of infra-red spectral lines, have suggested that sunspot activity may again be disappearing, possibly leading to a new minimum.[12]