Compass

A navigational instrument whose magnetized needle aligns with Earth’s magnetic field, indicating magnetic north and helping determine direction.

Magnetic dipole: A pair of equal, opposite magnetic poles separated by a distance, producing a characteristic magnetic field. A compass needle behaves approximately like a tiny magnetic dipole.
Lodestone: Naturally magnetized magnetite that attracts iron and can align with Earth's magnetic field. Lodestones supplied early magnetic direction-finding devices.
Orienteering: A sport in which participants navigate unfamiliar terrain using a map and compass. Competitors use a compass to maintain bearings between control points.
True north: The direction along Earth's surface toward the geographic North Pole. A magnetic compass points toward magnetic north, not directly toward true north.
Earth's magnetic field: The magnetic field surrounding Earth, generated mainly by motion in its liquid outer core. The needle aligns with the field’s horizontal component.
Han dynasty: A Chinese imperial dynasty that ruled from 206 BCE to 220 CE. Magnetic direction-finding objects are described in texts from this period.
Dead reckoning: Navigation that estimates position by advancing from a known point using direction, speed, and elapsed time. A compass supplies the direction component of the estimate.
Magnetic north: The direction indicated by Earth's magnetic field, which shifts over time and location. This is the reference direction a compass needle follows.
Magnetic declination: The angle between geographic north and magnetic north at a particular location. It explains why a compass bearing may differ from a true-north bearing.
Song dynasty: A Chinese dynasty that ruled from 960 to 1279 CE. Accounts from the Song period describe compasses used for navigation.

Linked from 24 pages