Meridians Of Longitudes 【2025-2026】
Meridians of longitude are half-circles of great circles connecting the Earth’s North and South Poles. Unlike parallels of latitude, which decrease in length poleward, all meridians are equal in length and converge at the poles. This paper explores the geometric properties of meridians, their historical determination, their critical function in establishing global time zones, and their modern definition within geodetic reference systems (e.g., WGS84). The prime meridian’s arbitrary yet conventional selection demonstrates the blend of natural geometry and human agreement that underpins global navigation.
The Earth is not a perfect sphere but an oblate spheroid. Geodesy defines meridians as ellipses (not perfect circles) on a reference ellipsoid (e.g., WGS84). The length of a meridian arc from equator to pole is about 10,002 km, varying slightly with latitude due to flattening. meridians of longitudes
Because no natural meridian exists (unlike the equator, defined by rotation), a zero meridian must be chosen by convention. Historically, many nations used their own capital observatories (Paris, Cadiz, Washington, etc.). Meridians of longitude are half-circles of great circles
ClickView 3m Show all Vertical Orientation: Unlike parallels of latitude which run horizontally, meridians run from top to bottom. Intersection: All meridians converge and meet at the North and South Poles. Equal Length: Every meridian is approximately the same length because they all span from pole to pole. Variable Spacing: Meridians are widest apart at the Equator (roughly 111 km or 69 miles) and get closer together as they approach the poles. Great Circles: Each meridian is half of a "great circle"; two opposing meridians (like 0° and 180°) together form a full circle that divides the Earth into two equal halves. Facebook +8 Major Meridians Prime Meridian (0°): Passes through the Royal Observatory in Greenwich, England . It is the starting point for measuring longitude and divides the Earth into the Eastern and Western Hemispheres. International Date Line (180°): Located exactly opposite the Prime Meridian. It serves as the transition point for calendar days, though it zig-zags to avoid splitting countries into two different dates. BBC +6 Measurement and Navigation Degrees: Longitude is measured from 0° to 180° East (E) and 0° to 180° West (W). Subdivisions: For precision, degrees are divided into 60 minutes ('), and each minute into 60 seconds ("). Time Zones: The Earth rotates 360° in 24 hours, meaning every 15° of longitude represents a one-hour difference in local time. Global Positioning: By combining a longitude coordinate with a latitude coordinate (e.g., 40° N, 30° W), any exact location on Earth can be pinpointed. Australian National Maritime Museum +8 Would you like to see how to The length of a meridian arc from equator
The term comes from the Latin meridies , meaning "midday." Historically, this is because the Sun crosses a specific meridian (reaches its highest point in the sky) at the same local time for all locations along that line.
Meridians of longitude, also known as lines of longitude, are imaginary lines that run from the North Pole to the South Pole on a globe or map. They are used to measure the distance east or west of a point from a reference meridian, which is the Prime Meridian. The Prime Meridian passes through Greenwich, England, and is designated as 0° longitude.
