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The Earth - third planet from the Sun The Earth is about 93 million miles from the Sun. It is about 7920 miles in diameter. Its weight is about 6,000,000,000,000,000,000,000 tons. It is the only place in the whole Universe where water is known to exist in liquid form. Its atmosphere is composed mostly of Nitrogen and Oxygen, together with some Argon, Carbon Dioxide, Water Vapour and other gases. It has a liquid metallic core, which gives rise to its magnetic field. The Earth has one natural satellite, the Moon, which orbits the Earth every 27.32 days. The interval between Full Moons, a so-called "lunar month" is 29.53 days. |
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There are also many thousands of artificial satellites, mostly at an altitude of a few hundred miles. Some satellites, those used for TV transmissions, are in geostationary orbit, 22,400 miles above the surface. |
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