IDENTIFY TIME ZONES AND CALCULATE TIME.Longitude and time zonesIn lesson 1 you learned the terms longitude, meridian, and prime meridian. In addition to location, these terms also relate to the rotation of the earth and the time of day. This is how it works: because it takes the earth twenty-four hours to rotate, the earth is divided into twenty-four time zones, each one hour apart. Each time zone covers about 15º of longitude. By international agreement, longitude is measured from the prime meridian in Greenwich, England. When the sun is exactly overhead in Greenwich, which is 0º longitude, it is noon there. The time zones west of 0º are earlier than Greenwich, and the time zones east of 0º are later than Greenwich. Every 15º represents one hour, so if it is 3:00 p.m. in Greenwich, then it is 2:00 p.m.15º west of Greenwich, and it is 4:00 p.m. 15º east of Greenwich.
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