Latitude, Longitude and Time Zones
Longitude and latitude are imaginary lines that circle the Earth. They are used to exactly pinpoint where a person or object is located. These lines are located on maps and measured in degrees. Each degree is divided into 60 minutes and each minute has 60 seconds.
Latitude describes east-west lines that circle the Earth parallel to the equator. Any point along the equator has a latitude of 0°. While the equator is the longest of these lines, they become shorter the farther you move to the poles, which have a latitude of 90°. The equator divides the earth into a northern and southern hemisphere. Each degree has the same distance, roughly 69 miles (111 km).
On its way around the sun, the Earth tilts its axis towards and away from it. This is the reason for special lines of latitude:
- Tropic of Cancer (23 ½ ° north of the equator) – the sun appears directly overhead in June
- Tropic of Capricorn (23 ½ ° south of the equator) – the sun appears directly overhead in December
- Arctic Circle (66 ½ ° north of the equator) – the sun is constantly above the horizon in June. Daylight lasts for 24 hours in June.
- Antarctic Circle (66 ½ ° south of the equator) - the sun is constantly above the horizon in December. Daylight lasts for 24 hours.
Longitude and Latitude
Longitude or meridians are lines that run from north to south across the globe. The starting point for this system (0°) is the British Royal Observatory in Greenwich, England. This prime meridian was chosen at a time when England was dominant in making maps and navigating. Locations west of this line have a longitude of up to 179° west; those to the east have a longitude of up to 179° east. The 180th meridian is exactly on the opposite side of the globe, in the middle of the Pacific Ocean. This is also the International Date Line. Travellers who travel westwards across the dateline change to the following day.
The distance between each degree of longitude varies. It is largest at the equator (69 miles) and shortest at the poles (0 miles) where the lines come together there.
Coordinates are numbers that locate a certain point on this system. New York, for example, lies at 41° North and 74° West. While navigators in the Middle Ages and during the Age of Exploration used sextants and the stars to determine their location, we use satellites and GPS to pinpoint our exact location anywhere on earth.
Because the earth rotates around its axis once a day, it is divided into 24 different time zones. The starting point for these time zones is the prime meridian in Greenwich, also called Greenwich Mean Time. Theoretically, every 15° east or west of Greenwich means one hour more or less. In practice, however, time zones do not go through the middle of countries.
Larger countries that span thousands of km, for example Russia or the United States, have several time zones. On the other hand, the Chinese Communists changed the country to one time zone when they took over after World War II.
The world's time zones
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- appear =to be seen
- axis = the line around which the Earth turns
- certain = special
- circle = go around
- constantly = always
- degree = unit for measuring a circle
- describe = define, explain
- determine = find out
- divide = split, separate
- dominant = leading, to be number one
- globe = Earth
- GPS = Global Positioning System = system that uses radio signals from satellites to show your exact positon on Earth
- hemisphere = half of the Earth
- however = but
- imaginary = not real
- in practice = in the real world
- locate = find an exact position
- map = a drawing of an area that shows cities, rivers, mountains and where they lie
- navigator = officer on a ship who plans which way to go or which route to take
- observatory = special building from which scientists watch the moon, stars and the planets
- opposite = on the other side
- parallel = line that are the same distance from each other
- pinpoint = locate
- prime = major, most important
- rotate = go around
- roughly = about
- sextant = object for measuring angles between the stars in order to find out where you are
- span = stretch across
- take over = get control of
- theoretically = in theory
- tilt = move, tip
- vary = different
- westwards = to the west