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{{short description|none}} <!-- "none" is preferred when the title is sufficiently descriptive; see [[WP:SDNONE]] -->
[[File:Southern Song Figure Holding Land Compass (9872744925).jpg|thumb|[[Song dynasty]] figurine of a man holding a compass]]
The [[compass]] is a [[magnetometer]] used for [[navigation]] and orientation that shows direction in regards to the [[Cardinal direction|geographic cardinal points]]. The structure of a compass consists of the compass rose, which displays the four main directions on it: [[East]] (E), [[South]] (S), [[West]] (W) and [[North]] (N). The angle increases in the clockwise position. North corresponds to 0°, so east is 90°, south is 180° and west is 270°.
The history of the compass started more than 2000 years ago during the [[Han dynasty]] (202 BC – 220 AD). The first compasses were made of [[lodestone]], a naturally magnetized stone of iron, in Han dynasty China.<ref name="cambridge1">{{cite book|last=Lowrie|first=William|title=Fundamentals of Geophysics|year=2007|publisher=Cambridge University Press|location=London|isbn=978-0-521-67596-3|pages=281 |ol=7751496M|url=https://openlibrary.org/books/OL7751496M/Fundamentals_of_Geophysics |quote=Early in the Han dynasty, between 300 and 200 BC, the Chinese fashioned a rudimentary compass out of lodestone. [...] This compass may have been used in the search for gems and in the selection of sites for houses. [...] Their directive power led to the use of compasses for navigation [...]}}</ref><ref>{{Cite journal|last=Shu-hua|first=Li|title=Origine de la Boussole II. Aimant et Boussole|url=http://dx.doi.org/10.1086/348315|journal=Isis|year=1954|volume=45|issue=2|pages=175–177|doi=10.1086/348315|s2cid=143585290|issn=0021-1753|via=JSTOR}}</ref> It was called the "South Pointing Fish" and was used for land navigation by the mid-11th century during the [[Song dynasty]] (960–1279 AD). [[Shen Kuo]] provided the first explicit description of a magnetized needle in 1088 and [[Zhu Yu (author)|Zhu Yu]] mentioned its use in maritime navigation in the text ''Pingzhou Table Talks'', dated 1111–1117.<ref name="merrill" /><ref>{{Cite journal|title=Science and Civilisation in China. Volume IV, Physics and Physical Technology. Part 1, Physics. By <italic>Joseph Needham et al.</italic> (New York: Cambridge University Press. 1962. Pp. xxxiv, 434. $15.00.)|url=http://dx.doi.org/10.1086/ahr/68.2.463|journal=The American Historical Review|year=1963|doi=10.1086/ahr/68.2.463|issn=1937-5239}}</ref> Later compasses were made of iron needles, magnetized by striking them with a lodestone. Magnetized needles and compasses were first described in medieval Europe by the English theologian [[Alexander Neckam]] (1157–1217 AD). The first
== Navigation prior to the compass ==
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The compass was invented in China during the [[Han dynasty]] between the 2nd century BC and 1st century AD where it was called the '''"south-governor"'''(''sīnán'' {{lang|zh|司南}}) or '''"South Pointing Fish"''' ({{lang|zh|指南魚}}).<ref name=merrill /> The magnetic compass was not, at first, used for navigation, but for [[geomancy]] and [[fortune-telling]] by the [[China|Chinese]]. The earliest [[China|Chinese]] [[magnetic]] compasses were possibly used to order and harmonize buildings by the geomantic principles of ''[[feng shui]]''. These early compasses were made with [[lodestone]], a form of the mineral [[magnetite]] that is a naturally occurring [[magnet]] and aligns itself with the Earth's magnetic field.<ref name="Guarnieri 7-1"/> People in ancient China discovered that if a lodestone was suspended so it could turn freely, it would always point toward the magnetic poles. Early compasses were used to choose areas suitable for building houses, growing crops, and to search for rare gems. Compasses were later adapted for navigation during the [[Song dynasty]] in the 11th century.<ref name="cambridge1" />
Based on Krotser and Coe's discovery of an [[Olmec]] [[hematite]] artifact in [[Mesoamerica]], [[radiocarbon dating|radiocarbon dated]] to 1400–1000 BC, astronomer John Carlson has hypothesized that the Olmec might have used the geomagnetic [[lodestone]] earlier than 1000 BC for [[geomancy]], a method of [[divination]], which if proven true, predates the Chinese use of magnetism for [[feng shui]] by a millennium.<ref name="John B. Carlson 1975">John B. Carlson, "Lodestone Compass: Chinese or Olmec Primacy? Multidisciplinary Analysis of an Olmec Hematite Artifact from San Lorenzo, Veracruz, Mexico", ''Science'', New Series, Vol. 189, No. 4205 (5 September 1975), pp. 753-760 (1975)</ref> Carlson speculates that the Olmecs used similar artifacts as a directional device for astronomical or [[geomancy|geomantic]] purposes but does not suggest navigational usage. The artifact is part of a polished [[hematite]] bar with a groove at one end, possibly used for sighting. Carlson's claims have been disputed by other scientific researchers, who have suggested that the artifact is actually a constituent piece of a decorative ornament and not a purposely built compass.<ref>{{cite book|last=Needham|first=Joseph |author2=Lu Gwei-Djen|title=Trans-Pacific Echoes and Resonances: Listening Once Again |publisher=World Scientific |year=1985 |page=21}}</ref> Several other hematite or magnetite artifacts have been found at pre-Columbian archaeological sites in Mexico and Guatemala.<ref name="A. P. Guimarães 2004">{{cite journal | last1 = Guimarães | first1 = A. P. | year = 2004 | title = Mexico and the early history of magnetism | journal = Revista Mexicana de Fisica | volume = 50 | pages = 51–53 | bibcode = 2004RMxFE..50...51G }}</ref><ref>{{cite web |url=http://www.dartmouth.edu/~izapa/CS-MM-Chap.%203.htm |title=Chapter 3 |publisher=Dartmouth.edu |access-date=2015-06-06 |archive-date=2012-07-16 |archive-url=https://web.archive.org/web/20120716191610/http://www.dartmouth.edu/~izapa/CS-MM-Chap.%203.htm |url-status=dead }}</ref>
== Early navigational compass ==
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In the Mediterranean, the introduction of the compass, at first only known as a magnetized pointer floating in a bowl of water,<ref>Kreutz, p. 368–369</ref> went hand in hand with improvements in [[dead reckoning]] methods, and the development of [[Portolan chart]]s, leading to more navigation during winter months in the second half of the 13th century.<ref>Lane, p. 606f.</ref><ref name="Guarnieri 7-1"/> While the practice from ancient times had been to curtail sea travel between October and April, due in part to the lack of dependable clear skies during the Mediterranean winter, the prolongation of the sailing season resulted in a gradual, but sustained increase in shipping movement; by around 1290 the sailing season could start in late January or February, and end in December.<ref>Lane, p. 608</ref> The additional few months were of considerable economic importance. For instance, it enabled [[Venice|Venetian]] convoys to make two round trips a year to the [[Levant]], instead of one.<ref>Lane, p. 608 & 610</ref>
Between 1295 and 1302, [[Flavio Gioja]] converted the compass from a needle floating in water to what we use today, a round box with a compass card that rotates 360 degrees attached to a magnetic element.<ref name=":0">{{Cite book|url=https://archive.org/details/riddleofcompass00acze|title=The riddle of the compass : the invention that changed the world|last=Aczel|first=Amir D.|date=2001|publisher=Harcourt|isbn=0151005060|edition=1st|location=New York|oclc=45102891|url-access=registration}}</ref>
At the same time, traffic between the Mediterranean and northern Europe also increased, with the first evidence of direct commercial voyages from the Mediterranean into the English Channel coming in the closing decades of the 13th century, and one factor may be that the compass made traversal of the [[Bay of Biscay]] safer and easier.<ref>Lane, p. 608 & 613</ref> However, critics like Kreutz have suggested that it was later in 1410 that anyone really started steering by compass.<ref>Kreutz, p. 372–373</ref>
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[[File: Al-Ashraf compass and qibla diagram.png|thumb|[[Al-Ashraf Umar II|Al-Ashraf]]'s diagram of the compass and Qibla. From MS Cairo TR 105, copied in Yemen, 1293.<ref name=Schmidl />]]
The earliest reference to a compass in the [[Muslim world]] occurs in a [[Persian language|Persian]] talebook from 1232, ''[[Jawami ul-Hikayat]]'',<ref name="Barbara M. Kreutz 370" /> where a compass is used for navigation during a trip in the [[Red Sea]] or the [[Persian Gulf]].<ref name=OEPST
Late in the 13th century, the [[Yemen]]i Sultan and [[Islamic astronomy|astronomer]] [[al-Malik al-Ashraf]] described the use of the compass as a "[[Qibla]] indicator" to find the direction to [[Mecca]].<ref>{{cite journal | last1 = Savage-Smith | first1 = Emilie|author-link1 =Emilie Savage-Smith | year = 1988 | title = Gleanings from an Arabist's Workshop: Current Trends in the Study of Medieval Islamic Science and Medicine | journal = [[Isis (journal)|Isis]] | volume = 79 | issue = 2| pages = 246–266 [263] | doi=10.1086/354701| pmid = 3049439 | s2cid = 33884974 }}</ref> In a treatise about [[astrolabes]] and [[sundials]], al-Ashraf includes several paragraphs on the construction of a compass bowl (ṭāsa). He then uses the compass to determine the north point, the [[meridian (astronomy)|meridian]] (khaṭṭ niṣf al-nahār), and the Qibla. This is the first mention of a compass in a medieval Islamic scientific text and its earliest known use as a Qibla indicator, although al-Ashraf did not claim to be the first to use it for this purpose.<ref name=Schmidl /><ref name=BEA>{{cite encyclopedia | editor = Thomas Hockey|display-editors=etal | last = Schmidl | first = Petra G. | title=Ashraf: al‐Malik al‐Ashraf (Mumahhid al‐Dīn) ʿUmar ibn Yūsuf ibn ʿUmar ibn ʿAlī ibn Rasūl | encyclopedia = The Biographical Encyclopedia of Astronomers | publisher = Springer | year = 2007 | location = New York | pages = 66–7 | url=http://islamsci.mcgill.ca/RASI/BEA/Ashraf_BEA.htm | isbn=9780387310220}} ([http://islamsci.mcgill.ca/RASI/BEA/Ashraf_BEA.pdf PDF version])</ref>
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