The length of a degree of latitude on Earth’s surface is about 69 miles, and is fairly constant because lines of latitude are all parallel and equally distant.

It is a different story with longitude lines, as they gradually converge toward the poles. One degree of longitude at the equator equals 69.17 miles, but as you move toward the poles, the distance between longitude lines diminishes. At 40º latitude, a degree of longitude equals 53 miles, at 60º the length of a degree of longitude is about 35 miles (approximately one-half of the equatorial length) and at 90º, where all lines meet, it is 0 miles. Meridians are sometimes called “hour lines” because Earth turns 15º, or the distance of one meridian, in one hour.

In the morning, your city is turning toward the sun. It passes under the sun at noon and turns away from it at night. Noon is the time when the sun is the highest in the sky above you.

It takes twenty-four hours for Earth to make one complete rotation. Therefore, each of the twenty-four meridians on your globe, or a space of 15º, represents one hour of time.