This relationship was the key to solving the "Longitude Problem" of the 18th century. While latitude could be found by the height of the sun or stars, determining longitude required knowing the precise time at a reference point (like Greenwich) while at sea. The invention of the marine chronometer—a clock that could keep accurate time amidst the rolling waves of the ocean—allowed sailors to calculate their east-west position by comparing local noon with the time back home.
When we talk about "meridian longitude," we are referring to the angular distance of a place east or west of a specific reference line known as the . The Prime Meridian: Point Zero
A is an imaginary North-South line that runs from the North Pole to the South Pole. Unlike lines of latitude (parallels), which get smaller as they move toward the poles, every meridian is exactly the same length—half of a great circle.
is an imaginary vertical line that runs from the North Pole to the South Pole. These lines are used to measure
Meridian longitude is the geographic coordinate system that measures distances east or west of a designated zero-point line known as the Prime Meridian. While latitude lines circle the Earth parallel to the Equator, longitude lines—or meridians—run vertically from the North Pole to the South Pole. Together, these imaginary lines form a grid system that allows humans to pinpoint any exact location on Earth, navigate the oceans, and standardize time across continents. meridian longitude
), and rotates once every 24 hours, the world is divided into time zones based on meridians, with each 15∘15 raised to the composed with power of longitude roughly representing one hour of time change ( per hour).
While political borders often force time zone boundaries to bend around states and nations, the underlying grid of meridian longitude remains the rigid architecture keeping our global financial markets, aviation grids, and internet servers perfectly synchronized. 6. The Space Age: From Greenwhich to GPS
To help explore coordinate systems or apply this information, tell me:
Positioned exactly halfway around the world from the Prime Meridian. Crossing this line shifts the calendar calendar day forward or backward. Why Greenwich, England? This relationship was the key to solving the
40.7128°, -74.0060° (West is represented by a negative sign) Why Longitude Distances Are Shrinking
All 360 meridians converge into a single point. The distance between them shrinks to zero .
| 对比项 | 经度（子午线） | 纬度 | | :--- | :--- | :--- | | | 南北走向 | 东西走向 | | 形状 | 半圆 | 整圆 | | 长度 | 每条经线长度相等： 约20004公里 | 不等长，赤道上最长，两极处缩短为点 | | 间隔 | 1度经度 的距离随纬度变化，赤道处约 111公里 | 1度纬度 的距离约为 111公里 ，基本恒定 |
The local time on your ship (calculated by the position of the Sun). When we talk about "meridian longitude," we are
Understanding these fundamental components of navigation allows us to pinpoint any location on Earth with precision. Share public link
Meridians divide the Earth into the Eastern Hemisphere (up to 180° East) and the Western Hemisphere (up to 180° West).
To prevent splitting countries or island groups into two different days, the actual International Date Line zigzags around political borders rather than strictly following the 180th meridian. The Longitude Problem: A Historic Scientific Quest
