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'''Earth''' is the name for the planet on which humankind lives. It is the third planet from the [[Sun]].
'''Earth''' is the name for the planet on which humankind lives. It is the third planet from the [[Sun]].
It orbits at an average distance of about 93 million miles (150 million km) from the Sun in an almost circular orbit. It takes light (and other forms of electromagnetic radiation) approximately 500 seconds to travel from the Sun to the Earth, i.e. the distance can also be stated as "500 light-seconds." The distance to nearby stars is made by measuring the stellar [[parallax]] between observations when the earth is at opposite ends of its orbit, so the earth's orbit itself is a measuring stick for astronomical distances, and is known as the ''astronomical unit'' (A. U.) It is worth noting that if the Earth were slightly closer to the Sun, it would be too hot for life (just as Venus is) while if Earth were slightly further away from the Sun, water would freeze and life would be impossible. The fact that the Earth is the perfect distance away from the Sun is taken by many [[Christian|Christians]] to be evidence of [[God]]'s existence. <ref>http://www.everystudent.com/features/isthere.html</ref>
It orbits at an average distance of about 93 million miles (150 million km) from the Sun in an almost circular orbit. It takes light (and other forms of electromagnetic radiation) approximately 500 seconds to travel from the Sun to the Earth, i.e. the distance can also be stated as "500 light-seconds." The distance to nearby stars is made by measuring the stellar [[parallax]] between observations when the earth is at opposite ends of its orbit, so the earth's orbit itself is a measuring stick for astronomical distances, and is known as the ''astronomical unit'' (A. U.) It is worth noting that if the Earth were slightly closer to the Sun, it would be too hot for life (just as Venus is) while if Earth were slightly further away from the Sun, water would freeze and life would be impossible. The fact that the Earth is the perfect distance away from the Sun is taken by many [[Christian|Christians]] to be evidence of [[God]]'s existence. <ref>http://www.everystudent.com/features/isthere.html</ref> However, this could be said for any species around any planet around any star, so there is nothing particularly special about fine-tuning conditions for life on Earth.
The Earth is approximately 8000 miles (13000 km) in diameter, so its circumference is approximately 8000·π = about 25,000 miles (40,000 km). Its surface area is approximately 4·π (4000 mi)<sup>2</sup> = 200 million square miles (510 million km<sup>2</sup>). It has been said that Earth should really be called "water:" most of the Earth's surface, about 70%, is covered by water. In fact, the Pacific and Indian oceans alone cover about half of the Earth.
The Earth is approximately 8000 miles (13000 km) in diameter, so its circumference is approximately 8000·π = about 25,000 miles (40,000 km). Its surface area is approximately 4·π (4000 mi)<sup>2</sup> = 200 million square miles (510 million km<sup>2</sup>). It has been said that Earth should really be called "water:" most of the Earth's surface, about 70%, is covered by water. In fact, the Pacific and Indian oceans alone cover about half of the Earth.