Effects of Earth’s Rotation

During the early days, people determined time by the crowing of cocks at sunrise and sunset. For them, morning begins when the cock crows at sunrise. The same thing happens at sunset; the cock crows and nighttime begins. Later on, scientists learned about determining the time and the length of day and night based on the rotation of Earth. They divided Earth’s surface into 24 time zones that correspond to the 24 meridians of longitude, or lines running north and south on Earth’s surface from pole to pole, which are set at 15° intervals. The time zone starts from the prime meridian at 0° longitude located at Greenwich, England. The line on Earth exactly opposite the prime meridian is both 180° east longitude and 180° west longitude. Earth rotates through 360° in 24 hours or 15° every hour. When Earth has rotated 15°, one hour has passed. After 120°, eight hours have passed.

You can imagine the passing of time as Earth rotates. The sun rises at around 6 o’clock in the morning and sets at 6 o’clock in the evening. This takes place in 12 hours when Earth has gone 12 meridians. Another 12 hours lapse in the evening as Earth passes another 12 meridians until it completes one rotation.