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Move your mouse over the image to see latitude and longitude

diagram showing latitude and longitude

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Latitude and longitude come from simple spherical geometry.

A line of latitude or Line of Parallel is an imaginary line around the earth that runs parallel to the equator. It shows in degrees (º) how far north or south a place is. The latitude of 0 degrees is on the equator — an imaginary line on the earth's surface. The equator divides the earth into the Northern Hemisphere and Southern Hemisphere (from Greek hemi = half). In the Galapagos Islands, the equator line passes through the northern part of Isabela, the biggest island in the archipelago. Look at a map of the world to see the other places though which the equator passes. The angle between the equator and the poles is 90 degrees so the Poles are at 90 degrees north or south. The farthest north or south you can go is 90 degrees, which puts you on the North or South Pole.

A line of Longitude shows distance in degrees you are east or west from a special line that joins the north and South Pole. The world turns west to east (anticlockwise from above). So defining a 0 line is more arbitrary than for latitude — hence, the Greenwich Meridian and Greenwich Mean Time had to be created. To make lines of longitude, slice through the earth at the equator where you'll make a horizontal circle. Divide the edge of this horizontal circle into two sets of 180 degrees (East or West). The 0 degree line passes through Greenwich to make the Greenwich Meridian. Next, make imaginary lines north and south from the equator that they converge on each pole. Now you have the meridians or lines of Longitude.

In the 18th century England was the world's greatest sea power and had a large Navy. The country had the most technologically advanced observatory in the world. Observatories are special laboratories for studying meteorology and astronomy. When maritime nations gathered to choose the special north-south line they decided the line should run though the main telescope of the Royal Greenwich Observatory. Ever since that meeting, mapmakers have the placed the 0 degree Longitude Meridian running through Greenwich, England in London. This also explains why all the world's time zones are relative to Greenwich Mean Time (GMT).

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Learn more about longitude and latitude

"These tested Our Horizon —
Then disappeared
As Birds before achieving
A Latitude."
Emily Dickinson These tested Our Horizon 1955

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