The ancient people made attempts to determine the size of the Earth. About 2,000 years ago a Greek astronomer, Eratosthenes, who lived In Alexandria in Egypt succeeded in calculating the size of the earth almost accurately, according to him, the earth’s circumference at the equator was 41,140 kms. It was very close to the actual circumference of the earth, as known today.

The actual equatorial circumference of the earth is 40,076 km, where as the polar circumference is 40,006 km. The difference between the two is 70 km. The earth’s equatorial diameter is 12,757 km and the polar diameter is 12,714 km. The difference is 43 km. The geoids shape of the earth makes the circumference through the poles little less than that along the equator. The total surface area of the earth is 510. 9 million sq kms of the surface area, 71 % is covered by water mass and 29% is covered by landmass. The water mass is 361 million sq.kms and the land area is 149 million sq.kms. The land area is divided into seven continents and many island. The continents are Asia, Africa, and North America, South America, Antarctica, Europe and Australia.

The water area consist of five ocean, namely, the pacific Ocean, the Atlantic Ocean, the Indian Ocean, the Antarctic ocean and the Arctic Ocean and many gulfs, bays and seas. The globe is divided into two hemispheres, namely the northern hemisphere and the southern hemisphere, by the equator. The northern hemisphere contains 2/3 of the land and the southern hemisphere contains 1/3 of the land. The zero degree meridians decide the globe into two hemispheres, namely, the eastern hemisphere and the western hemisphere.