Now that we can travel so fast by jet plane over big distances, the differences in time have become even more startling. We can leave New York at a certain hour, for example, and arrive in Los Angeles just a little while later-on the clock.
The reason for this is that the U.S.A. is divided into time zones. This division was adopted in 1833, when the United States was divided into four time belts or zones-Eastern, central, mountain, and Pacific.
The division was based on meridians, the imaginary lines that run around the earth through the North and South Poles. The time kept in each belt varies exactly an hour from the belt next to it. And the time kept everywhere within each belt is exactly the same.
As you move from one belt to another, going east, the time advances an hour. If you go west, it goes back an hour. But the time belts do not follow perfectly straight lines. The reason for this is that some community may be closely linked with an area very near it and wish to keep the same time. For example, Georgia, most of Florida, and the lower peninsula of Michigan could all be in the central time zone, but they include themselves in the Eastern zone.
The whole world is divided into time zones exactly as the United States is. Every 15 degrees as one goes around the world, in terms of meridians, there is a new time zone. Where does the measuring start?
It starts in Greenwich, England, which has 0-degree meredian running through it. As you move east from Greenwich, you add an hour to Greenwich time every 15 degrees. As you move west from Greenwich, you subtract an hour from Greenwich time in the same way.
So when it is 12:00 noon in Greenwich, it is 4:00 in the morning in California, because you have moved west nine 15-degrees interval, and it is 2:00 in the afternoon in Egypt, beause you have moved east two 15-degrees intervals.
Exactly on the opposite side of the world from Greenwich is an imaginary line called "the International Date Line". If you cross this line moving west, you "lose" a whole day, and if you cross it moving east, you "gain" a whole day.
The reason for this is that the U.S.A. is divided into time zones. This division was adopted in 1833, when the United States was divided into four time belts or zones-Eastern, central, mountain, and Pacific.
The division was based on meridians, the imaginary lines that run around the earth through the North and South Poles. The time kept in each belt varies exactly an hour from the belt next to it. And the time kept everywhere within each belt is exactly the same.
As you move from one belt to another, going east, the time advances an hour. If you go west, it goes back an hour. But the time belts do not follow perfectly straight lines. The reason for this is that some community may be closely linked with an area very near it and wish to keep the same time. For example, Georgia, most of Florida, and the lower peninsula of Michigan could all be in the central time zone, but they include themselves in the Eastern zone.
The whole world is divided into time zones exactly as the United States is. Every 15 degrees as one goes around the world, in terms of meridians, there is a new time zone. Where does the measuring start?
It starts in Greenwich, England, which has 0-degree meredian running through it. As you move east from Greenwich, you add an hour to Greenwich time every 15 degrees. As you move west from Greenwich, you subtract an hour from Greenwich time in the same way.
So when it is 12:00 noon in Greenwich, it is 4:00 in the morning in California, because you have moved west nine 15-degrees interval, and it is 2:00 in the afternoon in Egypt, beause you have moved east two 15-degrees intervals.
Exactly on the opposite side of the world from Greenwich is an imaginary line called "the International Date Line". If you cross this line moving west, you "lose" a whole day, and if you cross it moving east, you "gain" a whole day.
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