Meridian Longitude Upd -

between two points using their longitude/latitude.

Harrison’s H-4 chronometer (1761) was accurate enough to win the British Longitude Prize. This mechanical breakthrough turned meridian longitude from a theoretical abstraction into a practical tool. meridian longitude

For centuries, determining longitude at sea was the greatest challenge facing sailors. The solution came from comparing local time (determined by the Sun’s position) with the time at a reference meridian (e.g., Greenwich). Every hour of difference equals 15° of longitude. between two points using their longitude/latitude

It is measured in , minutes , and seconds (or decimal degrees). For centuries, determining longitude at sea was the

The link between longitude and time is so fundamental that it literally divides our days. The world is divided into 24 primary time zones, each roughly 15° of longitude wide, corresponding to one hour of the Earth's rotation. The starting point is , which is effectively the mean solar time at the IERS Reference Meridian.

Understanding is crucial for understanding how we divide our planet for time, navigation, and mapping.

Every measurement needs a starting point. For latitude, nature provides an obvious baseline: the equator. For longitude, however, there is no natural starting point. Any meridian could theoretically serve as the baseline.