Earth seen from Space. India lies in the centre, with Africa and the Middle East to the left.Our own planet, Earth, is the third planet from the Sun. It is the largest of the four inner, or terrestrial, planets and the fifth largest planet of all. Earth’s distance from the Sun, neither too close nor too far, provides exactly the right temperature range for water to exist in its liquid state. About 71% of the Earth’s surface is taken up by oceans. Liquid water is essential for the existence of life. Earth is the the only world in the Universe where both liquid water and life is known to exist.
Travelling at about 30 kilometres (18.5 miles) per second, Earth takes just over 365 days (an Earth year) to complete one orbit. As it goes, it spins on its axis once every 24 hours. This makes the Sun appear to rise at dawn, pass across the sky and set at dusk, giving us day and night. Earth is itself orbited by the Moon, which takes 27 days to go round it.
Earth is not quite a perfect ball or sphere, but slightly squashed at top and bottom. This shape is known as an oblate spheroid.
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