While latitude lines give us the comfortable, parallel circles that wrap horizontally around the Earth, meridians of longitude are the unsung heroes of navigation and timekeeping. They run from pole to pole, dictating not only where we are east or west, but when we are. Understanding meridian longitude is essential for everyone from airline pilots and astronomers to hikers and history buffs.
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This convergence is why polar maps are often displayed using different projections (like the Azimuthal projection) rather than the standard Mercator projection, which grotesquely exaggerates the size of polar regions. meridian longitude
A meridian is an imaginary half-circle from the North Pole to the South Pole. Unlike latitude (which has a natural zero at the equator), longitude’s zero line is —chosen by people, not nature. While latitude lines give us the comfortable, parallel
: All meridians meet at the North and South Poles. This means the distance between meridians is greatest at the Equator and decreases to zero as they approach the poles. (Invoking related search suggestions
The tipping point came in the 19th century with the rise of rail travel and transatlantic cables. In October 1884, 25 nations convened in Washington, D.C., for the International Meridian Conference. Despite French abstention, the vote was decisive: the Greenwich Meridian would become the world’s universal reference. Why Greenwich? By 1884, over 70% of the world’s shipping charts already used it, thanks to Britain’s maritime dominance and the accuracy of the Greenwich chronometers.