102,807
edits
Changes
From Nordan Symposia
Jump to navigationJump to searchno edit summary
[[File:lighterstill.jpg]][[File:Compass.jpg|right|frame]]
*Date: [http://www.wikipedia.org/wiki/14th_Century 14th century]
==Definitions==
*1 a : [[boundary]], [[circumference]] <within the compass of the city walls>
:b : a [[circumscribed]] [[space]] <within the narrow compass of 21 pages — V. L. Parrington>
:c : range, scope <the compass of my [[voice]]>
*2 : a curved or roundabout [[course]] <a compass of [[seven]] days' [[journey]] — 2 Kings 3:9
*3 a : a device for determining directions by means of a [[magnetic]] needle or [[group]] of needles turning freely on a pivot and pointing to the magnetic north
:b : any of various nonmagnetic devices that indicate direction
:c : an instrument for describing [[circles]] or transferring [[measurements]] that consists of two pointed branches joined at the top by a pivot —usually used in plural —called also pair of compasses
*4 : direction 6c <his [[moral]] compass>
==Descriptions==
A '''compass''' is a [[navigational]] [[instrument]] for determining direction [[relative]] to the [[Earth]]'s [http://en.wikipedia.org/wiki/Magnetic_pole magnetic poles]. It consists of a magnetized pointer (usually marked on the North end) free to align itself with [[Earth]]'s [http://en.wikipedia.org/wiki/Earth%27s_magnetic_field magnetic field]. The compass greatly improved the safety and efficiency of [[travel]], especially [[ocean]] travel. A compass can be used to [[calculate]] heading, used with a sextant to calculate [http://en.wikipedia.org/wiki/Latitude latitude], and with a [http://en.wikipedia.org/wiki/Marine_chronometer marine chronometer] to calculate [http://en.wikipedia.org/wiki/Longitude longitude]. It thus provides a much improved [[navigational ]] [[capability]] that has only been recently supplanted by modern devices such as the [http://en.wikipedia.org/wiki/Global_Positioning_System Global Positioning System (GPS)]. A compass is any [[magnetically]] [[sensitive]] device capable of indicating the direction of the [http://en.wikipedia.org/wiki/North_Magnetic_Pole magnetic north] of a [[planet]]'s [http://en.wikipedia.org/wiki/Magnetosphere magnetosphere]. The face of the compass generally highlights the [http://en.wikipedia.org/wiki/Cardinal_direction cardinal points] of north, south, east and west. Often, compasses are built as a stand alone sealed [[instrument]] with a magnetized bar or needle turning freely upon a pivot, or moving in a [[fluid]], thus able to point in a northerly and southerly direction. The compass was [[invented]] in [http://en.wikipedia.org/wiki/Ancient_China ancient China] sometime before the 2nd century, and was used for [[navigation]] by the 11th century. The dry compass was [[invented]] in [http://en.wikipedia.org/wiki/Middle_Ages medieval] Europe around 1300. This was supplanted in the early 20th century by the liquid-filled magnetic compass.
Other, more accurate, devices have been [[invented]] for determining north that do not depend on the Earth's magnetic field for operation (known in such cases as [http://en.wikipedia.org/wiki/True_north true north], as opposed to [http://en.wikipedia.org/wiki/Magnetic_north magnetic north]). A [http://en.wikipedia.org/wiki/Gyrocompass gyrocompass] or [http://en.wikipedia.org/wiki/Astrocompass astrocompass] can be used to find true north, while being unaffected by stray [[magnetic]] fields, nearby [[electrical]] [[power]] [[circuits]] or nearby masses of ferrous metals. A recent [[development]] is the electronic compass, or [http://en.wikipedia.org/wiki/Fibre_optic_gyrocompass fibre optic gyrocompass], which detects the [[magnetic]] directions without [[potentially]] [[fallible]] moving parts. This device frequently appears as an [[optional]] subsystem built into GPS receivers. However, magnetic compasses remain popular, especially in remote areas, as they are cheap, durable, and require no electrical power supply.[http://en.wikipedia.org/wiki/Compass]
[[Category: General Reference]]
