referansemeridianen

Referansemeridianen, often translated as the prime meridian, is a meridian in astronomy and geographic coordinate systems at which longitude is defined to be 0 degrees. It is the meridian that, along with the 180th meridian, forms a great circle that divides the Earth into the Eastern and Western Hemispheres. The choice of which meridian to designate as the prime meridian is arbitrary, but the Greenwich Meridian, passing through the Royal Observatory in Greenwich, London, is the most widely accepted and used as the reference meridian.

Historically, various countries and institutions used their own prime meridians. However, through international agreement, the Greenwich Meridian was adopted as the standard in the late 19th century. This standardization was crucial for navigation, cartography, and global communication. The concept of a reference meridian is fundamental to the geographic coordinate system, which uses latitude and longitude to pinpoint any location on the Earth's surface.

The prime meridian, in conjunction with the equator (0 degrees latitude), divides the Earth into four quadrants. Longitude is measured in degrees east and west of the prime meridian, up to 180 degrees. The prime meridian plays a significant role in timekeeping as well, as it serves as the reference for Coordinated Universal Time (UTC), which is the primary time standard by which the world regulates clocks and time.