Which city is used as the reference point for 0 degrees of longitude?

The invisible line that marks zero degrees of longitude, known as the Prime Meridian, runs through Greenwich, England. This crucial geographical reference point divides the Earth into the Eastern and Western Hemispheres, much like the Equator separates north from south. Its establishment was a pivotal moment in global navigation and timekeeping, providing a universal benchmark for location.

The selection of Greenwich as the world's Prime Meridian was not arbitrary but the result of an international agreement. In October 1884, delegates from 25 nations gathered in Washington D.C. for the International Meridian Conference. After extensive discussions, they voted to adopt the meridian passing through the Airy Transit Circle at the Royal Observatory in Greenwich as the international standard. A key reason for this choice was that by then, a significant majority of the world's ships were already using charts based on the Greenwich Meridian, making it the most practical and least disruptive option for global standardization.

This decision had profound implications beyond just mapping. The conference also recommended a global time zone system based on Greenwich Mean Time (GMT), intrinsically linking longitude to the measurement of time. Although modern scientific advancements have led to the International Reference Meridian (IRM), which is slightly east of the historical line, the original Greenwich Meridian remains a powerful symbol and a popular landmark. Visitors to the Royal Observatory can even stand with one foot in the Eastern Hemisphere and the other in the Western, a tangible connection to this fundamental concept of world geography.