Earth

Earth Earth, in geology and astronomy In geology and astronomy, the fifth largest planet of the solar system and the only planet definitely known to support life are known as Earth. Gravitational forces have molded the earth, like all celestial bodies, into a spherical shape. However, the earth is not an exact sphere, being slightly flattened at the poles and bulging at the equator. The equatorial diameter is c.7,926 mi (12,760 km) and the polar diameter 7,900 mi (12,720 km); the circumference at the equator is c.24,830 mi (40,000 km). The surface of the earth is divided into dry land and oceans, the dry land occupying c.57.5 million sq mi (148.9 million sq km), and the oceans c.139.5 million sq mi (361.3 million sq km). The earth is surrounded by an envelope of gases called the atmosphere, of which the greater part is nitrogen and oxygen. The Geologic Earth Knowledge of the earth’s interior has been gathered by three methods: by the analysis of earthquake waves passing through the earth (see seismology), by analogy with the composition of meteorites, and by consideration of the earth’s size, shape, and density. Research by these methods indicates that the earth has a zoned interior, earth, mi, km, earth’s, , sun, million, mantle, crust, called, surface, rock, energy, core, between, time, through, thought, sq, rocks, origin, northern, earthquake, density, axis, zone, waves, system, solar, sial, planet, passing, outer, one, melting, interior, hemisphere, gravitational, form, equator, direct, day, crustal, continents, boundary, average, winter, very, upper, types