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More than 2,000 years ago, Greek astronomers knew that the earth was a sphere, and was able to find the approximate size of its diameter. But photographs taken from the Apollo spacecraft in 1960 shows what the earth looks and it in the only accurate way to represent all the features of the world. When we look at a globe, we can only see one hemisphere at a time.
You can see vertical and horizontal lines on the globe or on a map. These lines are imaginary lines, drawn only in the globe or maps. The equator in the basis for all the horizontal lines known as latitudes and along with each latitude makes a complete circle. The equator 0° latitude passes exactly through the halfway between the North Pole and the South Pole, the two opposite ends of the earth. It thus divides the earth's surface into the northern and southern hemisphere. There are altogether 180 latitudes, 90 on each of the two hemispheres. They are marked N or S according to their hemispheres. The latitudes are of varied lengths; the equator is the longest and poles (90°) merely a point or no more a circle.
While the latitudes run east to west, the longitudes run north to south converging at the poles. There is no prime longitude as the equator, the longest and at the midway between the two poles could be. All longitudes are half circles and of equal lengths. They form a right angle at the equator. Of the total 360 longitudes, the one passing through Greenwich in London in arbitrarily taken as the prime Meridian, the basis for all longitudes.The prime Meridian and 180° longitude, just opposite, together divide the earth's surface into two hemispheres- the eastern and western hemisphere. The lines on the eastern hemisphere are marked E and the ones in the west carry W for their notification.
The International Date Line is the line which separates the east and west time by twelve hours. It divides the world into day and night.It is not straight to maintain the same time within the country.
The local time is based on the meridian through a specific area or area expressed with references to the meridian. It is the time of a particular region or area passing through the meridian line. The local timesvaries from place to place and it is determined by the status of the place like longitude and latitude.