Karla Knight, age ii, of Cape Elizabeth, Maine, for her question:
How many time zones are the in the world?
A calendar day begins at midnight. But when it is midnight in New Zealand, it is high noon in London. In Tokyo, it is nine in the morning when the clocks of Rio de Janeiro say it is nine in the evening. The time zones were planned to settle this global confusion of the clocks.
The world's time zones are based on circles and every circle is divided into 360 equal degrees. As the earth rotates around its axis, it too circles through 360 degrees. It rotates once in 24 hours, so in one hour it rotates through 15 degrees of a Circle.
Each time zone is planned to account for one of the 24 hours of a calendar day. If you guessed that the world has 24 time zones, you would be right. Time creeps westward and each zone is one hour ahead of the zone to the west and one hour behind the zone to the east.
The lines between the zones are planned to follow the lines of longitude that run from pole to pole. If a zone line ran through a big city, the people to the west would be an hour behind those in the east. For this reason, the zones bend around large population areas. On the ocean, most of the zones are straight, though some bend around island groups.
The time zones are also related to the circles of latitude that run around the globe. In one hour, time marches across 25 degrees of all the lines of latitude. The largest circle of latitude is the equator and here 15 degrees equals about one thousand miles. North and south of the big circle, the globe tapers towards the poles and the circles of latitude get smaller. The degrees Of latitude get shorter.
At the equator, the time zones are about 1,000 miles apart. North and south of the equator, they get closer together. The 24 time zones divide the globe like 24 sections of an orange.
Portland, Maine and Portland, Oregon are separated by four time zones. It is 9 a.m. In Oregon when the clocks of Maine say noon. These four time zones equal one¬ sixth of the distance around the globe, with its 24 time zones.
Every hour, the sun seems to travel 15 degrees of a great circle over the sly. Actually, the sun does not circle around our little planet. The earth rotates, facing the sun with first one side, then another. The earth rotates 15 degrees in an hour, which makes the sun seem to travel 15 degrees every hour over the sky.