A compass is a navigational instrument that measures directions in a frame of reference that is stationary relative to the surface of the earth. The frame of reference defines the four cardinal directions (or points) – north, south, east, and west. Intermediate directions are also defined. Usually, a diagram called a compass rose, which shows the directions (with their names usually abbreviated to initials), is marked on the compass. When the compass is in use, the rose is aligned with the real directions in the frame of reference, so, for example, the "N" mark on the rose really points to the north. Frequently, in addition to the rose or sometimes instead of it, angle markings in degrees are shown on the compass. North corresponds to zero degrees, and the angles increase clockwise, so east is 90 degrees, south is 180, and west is 270. These numbers allow the compass to show azimuths or bearings, which are commonly stated in this notation.
There are two widely used and radically different types of compass. The magnetic compass contains a magnet that interacts with the earth's magnetic field and aligns itself to point to the magnetic poles. The gyrocompass (sometimes spelled with a hyphen, or as one word) contains a rapidly spinning wheel whose rotation interacts dynamically with the rotation of the earth so as to make the wheel precess, losing energy to friction until its axis of rotation is parallel with the earth's.
The magnetic compass was first invented as a device for divination as early as the Chinese Han Dynasty. The compass was used in Song Dynasty China by the military for navigational orienteering by 1040-1044, and was used for maritime navigation by 1117. The use of a compass is recorded in Western Europe between 1187 and 1202, and in Persia in 1232. The dry compass was invented in Europe around 1300. This was supplanted in the early 20th century by the liquid-filled magnetic compass.
Read more about Compass: Types of Compasses, History, Modern Compasses, Using A Compass
Famous quotes containing the word compass:
“Histories of the world omitted China; if a Chinaman invented compass or movable type or gunpowder we promptly “forgot it” and named their European inventors. In short, we regarded China as a sort of different and quite inconsequential planet.”
—W.E.B. (William Edward Burghardt)
“loosely bound
By countless silken ties of love and thought
To everything on earth the compass round,”
—Robert Frost (1874–1963)
“To “give style” to one’s character—a rare and noble art! Those practice it who compass all that their natures present as strengths and weaknesses and then fit them into an artistic plan until every one appears as art and reason and even weakness enchants the eye.”
—Friedrich Nietzsche (1844–1900)