The Greenwich Meridian It is an imaginary line that is fundamental for measuring longitudes and time zones. This geographical reference has played a key role in navigation, astronomy and geography, defining how we organize time globally. Although we take its importance for granted today, the history behind its choice is fascinating and full of controversy.
Since ancient times, humans have needed a reference point to locate oneself in the world, but Greenwich was not always the chosen one. Over the centuries, different civilizations used different meridians, until it was officially established in 1884 at an international conference. Why was this decision made? Was it always like this? Join us to explore this history and learn all the details of the Meridian Zero.
What is the Greenwich Meridian?
El Greenwich Meridian, also called Meridian Zero o Prime meridian, is an imaginary line that connects the North and South Poles, dividing the Earth into two hemispheres: East and West. It is considered the reference point for measuring longitude and also establishes the basis of the time zone system. To better understand this measurement, it is useful to know How is longitude measured on Earth?.
This meridian crosses the Royal Greenwich Observatory, located in London, England. At a time when navigation and cartography required a common system, it was determined that this would be the world reference point. The choice was not a coincidence, since Great Britain had a great influence on trade and navigation at that time.
History of the Zero Meridian
Although today the Greenwich Meridian is a global standard, was not always located in London. In ancient times, the most common reference point was on the island of El Hierro, in the Canary Islands. This meridian was widely used by European navigators because it marked the westernmost point of the known world.
In 1634, France proposed the meridian of the island of El Hierro as a reference, and many maps used it for centuries. However, with the rise of the British Empire and the need for international consensus, the situation changed.
En 1884, the International Meridian Conference, held in Washington DC, determined that the prime meridian would pass through Greenwich. The British proposal received 22 votes in favour, with only one country voting against (Dominican Republic). France and Brazil abstained from voting and continued to use the Paris meridian for years.
The Greenwich Meridian and time zones
One of the main impacts of the Greenwich Meridian is the Creation of time zonesThe world time system is based on this meridian, establishing the base time known as Greenwich Mean Time (GMT) or Greenwich Mean Time. To understand how this system works, you can consult Time zones in detail.
Each time zone represents a 15° longitude band, equivalent to a time difference with respect to GMT. For example, if it's 12:00 in Greenwich, in a region with GMT+2 it will be 14:00, while in an area with GMT-5 it will be 07:00. If you'd like to learn more about how these time zones work, you can check out .
Why was Greenwich chosen as the prime meridian?
There are several reasons why Greenwich was chosen as the global benchmark:
- Influence of the British EmpireIn the 19th century, Great Britain was one of the world's major powers, and many maps and navigation charts already used Greenwich as a reference.
- Common use in navigationBritish ships relied on the Greenwich system to calculate their position at sea, which facilitated its adoption internationally.
- Relationship with the railway system: Before time zones were standardized, each city could have its own local time, which caused problems for rail transport. Greenwich helped establish a unified reference.
The Greenwich Meridian today
Today, the Greenwich Meridian remains the reference point for measuring longitude, but its role in time zones has been partially replaced by the Coordinated Universal Time (UTC). This system is more accurate and is based on atomic clocks. To learn more about the evolution of time measurement systems, you can visit what are meridiansFurthermore, the GPS system's accuracy is also based on a meridian slightly offset from Greenwich, resulting in a measurement difference of a few meters.
Although its role has changed over time, the Greenwich Meridian remains a global reference symbol and a key point in the history of navigation and geography. Its adoption as a standard allowed for the unification of maps, the development of time zones, and the synchronization of time measurement systems, essential elements in our modern society.