What is a Magnetic Compass? - Definition & History

Instructor: Matthew Helmer

Matt is an upcoming Ph.D. graduate and archaeologist. He has taught Anthropology, Geography, and Art History at the university level.

Compasses revolutionized the way humans were able to explore the globe, and they still form the foundation of navigational science today. This lesson reviews the history and function of the magnetic compass.

Compasses: One of the World's First Gadgets?

Lodestone spoon from China ca. 300 BC
Lodestone Spoon

How does a Compass Work?

Magnetic compasses operate by placing a magnetized needle on a pivot point, which pulls the needle towards the North and South Poles of the Earth. Compasses revolutionized navigation by including cardinal directions (North, South, East, and West) combined with the idea of the 360 degree circular plane around the needle.

A compass needle will always point to Magnetic North--provided there are no magnetic disruptions in the area--which allows navigators to plot what are known as azimuths and bearings. Compass bearings plot the degree angle between Magnetic North and the orientation of the compass. Bearings are always recorded clockwise in a magnetic compass where North=0 or 360 degrees, East=90 degrees, South=180 degrees, West=270 degrees. Therefore, by facing any direction, an individual can calculate their orientation by counting the number of degrees clockwise their direction varies from the North-aligned arrow. In this way, compasses also revolutionized map-making. Bearings could be aligned with degrees and landmarks on maps, allowing for accurate navigation regardless of visibility. Compasses contributed greatly to the science of map-making, known as cartography.

Early Magnetic Compasses

European dry compass, 18th century
Maritime Compass
wet compassesdry compasses

Compasses Today

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