Check the meanings of the words in the box. Read the text and match the words to numbers 1-7 on the map (Kiểm tra nghĩa của các từ trong hộp. Đọc văn bản và nối các từ với số 1-7 trên bản đồ)
Time zones
Time zones helps us know what time it is in different parts of the world. This is because when the Earth rotates, the sun shines on only one part of the Earth, so when it's the morning in your country, it's night-time in another country.
The Earth has got twenty-four time zones. The lines for each time zone go from north to south. These are called lines of longitude. The line on the map at 0° longitude is called the Prime Meridian. This line goes through Greenwich, in London. The time there is called Greenwich Mean Time (GMT). The Earth rotates 15° of longitude every hour (24 x 15° = 360°). Places east of the Prime Meridian are ahead of GMT. For example, Istanbul is about 30° cast of the Prime Meridian, so the time there is GMT plus two hours. Places west of the Prime Meridian are behind GMT. For example, Rio is about 45° west of the Prime Meridian, so the time there is GMT minus three hours. So when it is 12 p.m. in London, it is 2 p.m. in Istanbul and 9 a.m. in Rio.
