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If you've ever studied geography, you've probably heard the terms "longitude" and "latitude." These imaginary curves around Earth show distance in degrees from north to south and east to west. On a flat map, these curves are displayed as horizontal lines (latitude) and vertical lines (longitude). The starting point for lines of latitude is the equator, but finding a starting point for longitude was a little trickier. Today, the prime meridian is the line of zero degrees longitude that separates the Eastern Hemisphere from the Western Hemisphere. It runs through Greenwich, England. In fact, you may have heard the expression "Greenwich Mean Time" or "GMT," because this zero degree line is also the line from which all global time is measured. But did you know that this line was once in a completely different place?
Take a look at a map of the continent of Africa. Off this continent's western coast, you will see the Madeira Islands. These islands are located in the Atlantic Ocean, about 350 miles off the coast of the African nation of Morocco. Portugal owns the Madeira Islands, and it has for hundreds of years. In 1506, Portuguese mapmaker Pedro Reinel first drew a prime meridian through the Madeira Islands. Since the Portuguese were leaders in sea power and trade, the rest of the world honored that mark for more than 300 years. But as the British became more dominant on the seas, they began drawing maps with lines of their own. In the 1800s, countries began to argue over the world's nautical lines and global marks. Measuring time and distance around the globe must have been very confusing!
As more nations began to embark on global travel and trade, it was clear that there would have to be an agreement on where the zero degree line, or prime meridian would be. In 1884, the president of the United States called for a conference of nations in Washington, D.C., to determine just that. The conference decided that the prime meridian was to be located in Greenwich, England. But the continent of Africa still plays an important role in this chapter of world geography. The prime meridian runs through the African nations of Algeria, Mali, Togo, Burkina Faso, and Ghana. And Africa is the only continent where you can find both the prime meridian (0 degrees longitude) and the equator (0 degrees latitude).
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