Page 41 - Exercise 1

Page 41 - Exercise 1

THE EARTH rotates on its axis. It takes 24 hours to turn. This means that the time isn’t the same in different parts of the world.

Until the 19th century, towns in the same country often had different times. This was because people told the time by the local position of the sun. It didn’t matter, because people didn’t travel very much and they travelled very slowly. However, all that changed when railways arrived. People could now travel quickly from town to town, so they needed a standard time. In 1884, countries agreed to an international time system with 24 zones.

The time zones start from the Prime Meridian at Greenwich in London. In all places east of Greenwich, the day starts earlier. In all places west of Greenwich, the day starts later.

Most countries are in one time zone, but some large countries have more than one. There are five time zones in the USA (excluding Hawaii). So when it’s 9 am in New York, it’s only 6 am in Los Angeles.

Australia has three time zones and Russia has nine!

The system of time zones starts in Greenwich. On the other side of the world is the International Date Line. When you cross this line, you don’t just change hours, you change days. So you can travel from today back into yesterday!