What time is it around the world?
When one half of the world is in daylight, the other half is in darkness. If everywhere on Earth was the same time then it would mean that half of the world would be dark during the day and light at night, which would not be very useful to the people who live there.
The history behind time zones:
Many towns and cities around the world used to set clocks based on observing the sun and the stars. This occurred prior to the late 19th century. Dawn and dusk occur at different times at different places because of the Earth's rotation. Originally, the need for time zones arose in Britain when English mariners needed to know the longitude at sea. By dividing the world into several sections, or time zones, this was much more simple. When the first time zone division emerged, each zone was divided according to its local noon. This was also based on daylight hours, which vary in different parts of the world at a given second, based on the position of the Earth to the sun. Time zones were created to give a uniform standard of time, but at the original time of the first internationally recognized time zone’s emergence, various countries had their own time zone standards. According to reports from Greenwich Mean Time’s website, before the coming of railways to Britain, there was no need for each city to keep in sync with another city’s exact time. For example, the city of Bristol had their own different local time than London did. Before GMT became regulated as the first time zone standard, some pre-1880 British clocks had two minute hands; one to display the local time and the other to display Greenwich Mean Time.
Today the whole of Britain is in the same time zone, however some countries are so large that they cover more than one timezone.
What are time zones?
The Earth is separated into lines of longitude (or segments) of 15 o each, starting at Greenwich, in England. Time zones were created to help people know what time is it now in another parts of the world. There are 24 separate segments or time zones. Below is a map showing their boundaries. The time zones are not exactly straight lines because, where possible they go around the edges of countries, so that the time in that country is constant.
Homework: Using your knowledge from our lesson today, please explain why we have time zones and work out which country celebrates the New Year first on Earth. The sheet is below if you need to print one.