Understand longitudes, prime meridians (Greenwich and ancient Ujjayinī), and how crossing latitudes and longitudes creates a grid to locate places.
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Hook revealing that India had its own prime meridian long before Greenwich.
The Greenwich Meridian isn't the first prime meridian! Centuries before Europe set the standard, Indian astronomers used a 'middle line' (madhya rekhā) passing through the ancient city of Ujjayinī (today's Ujjain) as their zero reference point!
Map showing the ancient Ujjayinī meridian running through India.
Centuries ago, Indian astronomers used a 'middle line' running through Ujjayinī to calculate global coordinates.
Explanation of longitudes, meridians, and prime meridians.
Imagine traveling from the North Pole to the South Pole by the shortest possible line. These half-circle lines are called meridians of longitude. Unlike parallels of latitude, all meridians are exactly the same length.
Practice recalling key longitude facts.
Lines of longitude are half-circles that run from pole to pole and are also called . To measure them, the internationally accepted 0° line passes through in London. However, in ancient Indian astronomy, the reference prime meridian passed through the city of . Whether you travel east or west from the prime meridian, the 180° East and 180° West lines meet to form the line on the back of the globe.
How latitudes and longitudes combine to create coordinates.
When you put parallels of latitude (running east-west) and meridians of longitude (running north-south) together on a globe, they intersect to form a grid.
Visual analogy comparing Earth's grid to a chessboard.
Just like a chess piece relies on a row and a column, earthly locations rely on intersecting latitude and longitude lines.
Identify how coordinates work.
To locate a place accurately on Earth, you need both its latitude and its _____.
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