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Name: Marlene
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Age: 12
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Date: 10/5/2003

What is a sidereal day?

The sidereal day is the time the Earth takes to rotate 360 degrees, that is in relation to the stars. It is 23 hours 56 minutes 4.09 seconds in length when one compares it with mean solar day which is 24 hours in length. [The Earth rotates 360.98 degrees in 24 hours.]

The difference is caused by the Earth's orbital motion, and that the Earth travels around one reference point [the mean Sun], but not the other [an extremely distant star or stars].

Howard Barnes

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