We explain what the Greenwich Meridian is and the history of this imaginary line. We also explain how it is used for location, navigation, and global timekeeping.
What is the Greenwich Meridian?
The Greenwich Meridian, also called the zero meridian, base meridian, or prime meridian, is the imaginary vertical line that divides the world map into two identical halves and from which longitude is measured. It is also the meridian that marks the world’s standard base time, to which hours are added or subtracted to determine the time zones of each country.
The location of this imaginary line gets its name because it crosses the British town of Greenwich, England, and because the Royal Greenwich Observatory, built in 1675, was located there. In addition to the United Kingdom, the meridian crosses other countries, and it is common to find signs marking its location in France, Spain, Algeria, Mali, Burkina Faso, Ghana, and Togo. You must read about Numbering System once.
The Greenwich meridian divides the planet into two semicircles of 180° each, segmented into 15° time zones (the result of dividing 360° of the complete circumference by 24 hours).
Characteristics of the Greenwich Meridian
The Greenwich Meridian has the following characteristics:
- It is the 0° meridian, from which the planet is divided into two hemispheres: east and west.
- It is considered the world’s prime meridian.
- It crosses the English town of Greenwich, hence its name.
- It was adopted as the basis of the planetary coordinate system in 1884.
- It is the basis for calculating time throughout the world.
History of the Greenwich Meridian
The decision to adopt the Greenwich Meridian as the basis for the time and coordinate system was made in 1884 in Washington, D.C., United States, at a convention attended by 41 delegates from 25 countries.
There, the universalization of this system was agreed upon, since different meridians were used as a guide in various places, such as Paris, Rome, Copenhagen, Jerusalem, and St. Petersburg. The resolution met with disapproval from countries such as the Dominican Republic, with abstentions from France and Brazil, but Greenwich was ultimately established as the 0° meridian, which remains the case today.
GPS Systems: There is a very slight angular difference (5.3 seconds) between the Greenwich Meridian and the reference meridian used by contemporary GPS systems. This is because a more precise definition of the reference meridian was introduced in 1984, known as the IERS (International Earth Rotation and Reference Systems Service) Reference Meridian, which establishes the Greenwich Meridian as approximately 102 meters east of its original position. Maybe you should definitely read about Social Mobility once.
Greenwich Meridian and Time Zones
The Greenwich Meridian is the reference point from which all time zones on the planet are calculated. Coordinated Universal Time (UTC) has its zero point on this meridian and is the global time standard currently used.
Time zones for other countries are calculated from UTC 0. For example, if a location has a UTC+3 time zone, it means that it is three hours later than the locations crossed by the Greenwich Meridian. If a location has UTC-5, it means that it is five hours earlier.
Latitude and Longitude
Latitude is an angular measurement used to determine the position of a point on the Earth’s surface in a north-south direction. It is measured in degrees and ranges from 0° at the equator to 90° at the poles.
Longitude, on the other hand, is an angular measurement used to determine the position of a point on the Earth’s surface in an east-west direction. Like latitude, it is measured in degrees and ranges from the Greenwich Meridian (0°) eastward and westward to a maximum of 180°, where the Greenwich Meridian is located.
Using latitude and longitude, the geographic coordinates of any point on the planet’s surface can be determined. For example, Mexico City is located at 19° north latitude and 99° west longitude. This means it is located 19° north of the equator and 99° west of the Greenwich Meridian.
References
All the information we offer is supported by authoritative and up-to-date bibliographic sources, ensuring reliable content in line with our editorial principles.
- Hernández, L. (2022). Greenwich: Why did it become the sole reference meridian and origin of geographic longitude?. LaSexta. lasexta.com
- McKeever, A. (n.d.). Curiosities (and madness) of the world’s time zones. National Geographic. nationalgeographic.es
- Galileo Galilei Planetarium. (n.d.). The Earth. Rotational motion. Time zones. planetario.buenosaires.gob.ar
- Velasco, M. (2024). Greenwich Meridian: The watchmaker who discovered how to measure longitude at sea. La Vanguardia. lavanguardia.com
