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==Unusual characteristics of the Moon==

==Unusual characteristics of the Moon==

Unlike most planets in the solar system, Earth has only one moon and it has several striking characteristics:   

Unlike most planets in the solar system, Earth has only one moon, and it has several striking characteristics:   

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|1.

|During recent history the Moon has had roughly same size as the [[Sun]] when viewed from Earth.  This creates a situation which permits phenomenal solar eclipses to occur. The odds of that symmetry occurring by chance are very small. That symmetry will not last forever.

|During recent history the Moon has had roughly same size as the [[Sun]] when viewed from Earth.  This creates a situation which permits phenomenal solar eclipses to occur. The odds of this symmetry occurring by chance are very small. The symmetry will not last forever.

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|2.

|2.

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|4.

|4.

|The Moon is currently receding from the Earth at less than 6 inches per year. The Moon could never have been closer than about 11,000 miles or it would have been broken up by tidal forces. If the rate of recession is assumed to have averaged about 6 inches per year, the Moon's present distance of about 250,000 miles implies an age for the Moon of no more than 2.6 billion years.{{fact}} However, the tidal forces between Earth and Moon are not constant, and so simply extrapolating from the current rate of change is not strictly valid.{{fact}}

|The Moon is currently receding from the Earth at 1.5 inches (3.8 cm) per year<ref>NASA [http://sunearth.gsfc.nasa.gov/eclipse/SEhelp/ApolloLaser.html]</ref>. The Moon could never have been closer than about 11,000 miles or it would have been broken up by tidal forces. If the rate of recession were stayed constant at 3.8 cm per year, it would take 9.6 billion years for the lunar distance to recess from 11,000 miles to the present distance of about 240,000 miles.  However, the tidal torque between Earth and the Moon would not be constant if the [[continental drift|continents drift]], so a simple linear extrapolation is not valid.{{fact}}

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