A is an imaginary vertical line on the Earth's surface that connects the North and South Poles. These lines are used to measure longitude , which indicates how far east or west a location is from a starting point called the Prime Meridian. Core Concepts What is longitude? - NOAA's National Ocean Service
Greenwich Mean Time (GMT), based on the Prime Meridian, was long used as the international time standard. Today, it has been succeeded by Coordinated Universal Time (UTC), which is kept precise by atomic clocks but remains anchored to the Prime Meridian grid. The International Date Line
The conference established that the day begins at mean midnight on the Prime Meridian.
A self-taught English clockmaker named solved the problem. Between 1730 and 1761, he developed a series of highly accurate marine chronometers—clocks that could keep precise time aboard a rolling, pitching ship despite changes in temperature, humidity, and pressure. His fourth model, H4, looked like a large pocket watch and lost only 5 seconds over a 81-day voyage to Jamaica.
Any pair of opposing meridians (such as 0° and 180°) forms a "Great Circle" that divides the Earth into two equal halves, or hemispheres. The History of the Prime Meridian meridian longitude
: Unlike lines of latitude (parallels), all meridians meet at the poles. Variable Distance
值得注意的是，经度1度的覆盖范围会随着纬度升高而变窄。到了北纬60度（靠近斯堪的纳维亚半岛或加拿大北部）的地方，两条经线之间的实际距离仅约为赤道的一半，约。
As mentioned, the 180th meridian is the basis for the International Date Line. It is also used as a reference for some national boundaries and time zone offsets (UTC+12 to UTC-12). Countries like Fiji, New Zealand, and Russia have territories near this meridian.
Meridian longitude lines are foundational to geography, navigation, and timekeeping. They allow us to divide the globe into a manageable, measurable, and standardized system, ensuring that whether we are setting our watches or finding our way home, we are all using the same global language of location. If you are interested, I can: A is an imaginary vertical line on the
Historically, determining latitude (North-South) was easy—you simply measured the angle of the North Star or the sun. However, determining longitude (East-West) was the greatest scientific challenge of the 18th century.
The time at the Prime Meridian (0°) serves as the global baseline.
The meridian longitude system transforms our chaotic, spinning planet into an orderly, navigable map. From John Harrison’s heroic mechanical clocks to the satellite arrays fueling modern GPS, these imaginary lines from pole to pole remain the quiet infrastructure supporting global trade, travel, and communication. To help me tailor this article further, let me know:
A meridian is an imaginary half-circle on the Earth's surface that connects the Geographic North Pole to the Geographic South Pole. Key Characteristics of Meridians - NOAA's National Ocean Service Greenwich Mean Time
between two points using their longitude/latitude.
Just as the equator is the starting point for latitude, the is the starting point for longitude (
At the equator, one degree of longitude is approximately 111 kilometers. As you move toward the poles, this distance shrinks, becoming zero at the exact pole point. 4. Meridians, Time Zones, and Navigation