14. What time is it? That's a very good question! From morning to night, clocks help us to plan our day. They tell us when things begin and when they end.
Before clock, people tell time by watching the sun move across the sky. They started work when the sun came up in the east. At noon, when the sun was very high, they ate and rested. When the sun disappeared in the west, they went to bed.
Today, we know that the sun doesn't move around the Earth. As the Earth turns, the sun seems to be moving across the sky. It takes the Earth a day to make one complete turn.
A day is divided into hours, minutes and seconds. There are 24 hours in a day. There are 60 minutes in an hour. How many minutes are there in a day? 24*60=1,440. There are 1,440 minutes in a day.
We measure time by other movements, too. The Earth travels around the sun. It takes the Earth a year to go around the sun once. One year is 12 months, or just over 52 weeks. To be very accurate (准确的), it takes the Earth 365 days, 5 hours, 49 minutes and 12 seconds to go around the sun.
We divide the Earth into 24 time zones. Each time zone is one hour apart from the next time zone. For example, when it is 10:00 a.m. in Beijing, it is 9:00 p.m. in New York.
Because of the clocks and calendars (日历), we can measure time very easily. However, it is the movement of the Earth that really allows us to measure time.