Prime Meridian

Figure 1.2.2, Can you see how longitude lines, or meridians, are not the same distance apart? (http://wwp.greenwichmeridian.com)

Figure 1.2.3, Can you see how the international date line does not run directly on the meridian? (“Standard Time Zones of the World,” CIA World Factbook, 2007.)

Zero degrees longitude, or the prime meridian as it is also called, is the longitude line which runs through Greenwich, England. The degrees continue 180° east and 180° west around the globe, where they meet. This occurs close to the international date line in the Pacific Ocean, which is around 180°; however, as you can see from Figure 1.2.3, it meanders back and forth a bit in order to keep all communities on the same day! You will learn more about the time zones in lesson 3. For now, just remember that the longitude lines west of the prime meridian all the way to the international date line are western longitude lines, and the longitude lines east of the prime meridian all the way to the international date line are eastern longitude lines. So if I wanted to show that a city is located at 130° west of the prime meridian, I would write it like this: 130° W. If it were located 130° east of the prime meridian I would write it like this: 130° E, as you can see in Figure 1.2.2.

This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 Unported License. For more information about this and other OCW projects at BYU, visit http://ocw.byu.edu.