Meridian Longitude [updated]

Because the Earth rotates 15° per hour, knowing your longitude requires knowing the exact time at a reference point (like Greenwich) and the local time on your ship. If your local noon (sun at its highest point) occurs 2 hours after noon in London, you are 30° west of London.

While latitude lines are equally spaced, meridian longitude lines are farthest apart at the Equator (about 111 km per degree) and converge to zero distance at the poles. This convergence has important implications for navigation and mapping projections.

Most confusion arises between longitude and latitude. Here is the differentiator:

Today, we no longer need to look at the stars or carry mechanical marine chronometers to find our position. However, the foundational rules of meridian longitude remain critical to modern infrastructure. 1. Global Positioning System (GPS)

如果把地球想象成一个橘子，瓣与瓣之间的分割线就好比子午线。这些线并非随意排列，它们汇聚于两极，为全球定位提供了最基础的网状坐标系统。