The prime meridian is the longitude line of zero degrees that is officially recognized as being at the Royal Observatory in Greenwich, London. There was a time when there were multiple prime meridians, as recognized by different countries since a prime meridian can technically be any longitude line. However, it is now agreed upon that the only official prime meridian is the one that goes through Greenwich, London.
The Beginning of the Prime Meridian
The concept of a prime meridian began to form when people became more curious about the timeliness of their travels. As trading and traveling continued to expand in the 1700s, merchants, travelers, and scientists needed a way to calculated the time it would take to travel back and forth between destinations. Although the compass was a great invention for determining the direction in which one was going or should go, it could not give estimates of the time it would take to reach the destination; having a prime meridian would solve that. With a prime meridian, locations on Earth would be measured by their distance to the east or the west of the prime meridian line. Then, based on that distance and where the location was on a map, the current time would either increase or decrease as one would travel east or west.
Prime Meridian Confusion
The only problem was that countries could not agree on where the prime meridian was. Again, a prime meridian could technically be any longitude line. Countries would decide their own prime meridians by measuring where a line of longitude passed through their capital city. Needless to say, this confused many people and made calculating time an unorthodox and nonuniform process. Many countries even published and distributed completely different maps within their own cities and towns.
An Official Prime Meridian
In 1851, Sir George Airy recognized the Royal Observatory in Greenwich, London, as a prime meridian – a decision that would bring the world closer to having an official prime meridian. The Royal Observatory, which was erected in 1675, was already deemed the beginning of longitude (the y-axis measuring from east to west) in the British coordinate system, so it made sense to have it as the prime meridian that England used.
Since England had a litany of colonies and so much influence over the world at that time, many people already considered the Royal Observatory to be the prime meridian. Despite this, there was still no official prime meridian and confusion remained about how to calculate time and measure distance. In 1884, the International Meridian Conference convened in Washington, D.C., and officially recognized the Royal Observatory in Greenwich, London, as the only official prime meridian.
Coordinated Universal Time and the International Date Line
With the creation of an official prime meridian also came the creation of Coordinated Universal Time (UTC time). UTC time is the starting point by which all time is measured. As people travel from east to west, and vice versa, time increases or decreases based on how far away their location is from the prime meridian (the UTC time zone). This led to the establishment of modern-day time zones. In addition to time zones, the International Date Line (IDL) was created. The IDL is the meridian (also known as a longitude line) that is positioned at 180 degrees longitude.
In conclusion, if not for the prime meridian, there would be no concept of time zones, the world’s understanding of longitude and latitude wouldn’t be as clear, and calculating time would be a lot more difficult. That would be hard to imagine in today’s world in which we use systems, like GPS, that rely so heavily on what the prime meridian established.