On October 13, 1884, the Greenwich meridian was adopted as the prime meridian, the imaginary north-south line where the longitude is 0 degrees. The Greenwich meridian divides the Earth into the Eastern and Western Hemispheres.

Unlike parallels of latitude, which are defined by their distance from the Equator and the poles (mathematically defined regions), the prime meridian is arbitrary and had to be agreed upon by the scientific community. U.S. President Chester A. Arthur asked delegates from 25 nations to meet in Washington, D.C., in order to select a site. Participants voted on the meridian that passes through the Royal Observatory, Greenwich, in London, England.

Today, the Greenwich meridian is visible in London at night in the form of a green laser beam pointing north from the Royal Observatory.

adopt
Verb

to formally raise and care for a child of other biological parents.

arbitrary
Adjective

determined by choice, not by standards or rules.

arbitrary
Adjective

determined by choice, not by standards or rules.

delegate
Noun

representative in government or a person who represents someone else.

Noun

imaginary line around the Earth, another planet, or star running east-west, 0 degrees latitude.

Noun

half of a sphere, or ball-shaped object.

laser
Noun

(acronym for light amplification by stimulated emission of radiation) an instrument that emits a thin beam of light that does not fade over long distances.

Noun

distance north or south of the Equator, measured in degrees.

Noun

distance east or west of the prime meridian, measured in degrees.

meridian
Noun

line of longitude, dividing the Earth by north-south.

Noun

imaginary line around the Earth running north-south, 0 degrees longitude.

More Dates in History

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