|Light-year (distance traveled by light in one year) ||5,880,000,000,000 mi|
|Parsec (parallax of one second, or stellar distances) ||3.259 light-years|
|Velocity of light ||c. 186,282.4 mi/sec|
|Astronomical unit (A.U.), or mean distance Earth to Sun ||ca. 93,000,000 mi1|
|Mean distance, Earth to Moon ||238,860 mi|
|General precession ||50',.26|
|Obliquity of the ecliptic ||23° 27'8'.26-0'.4684(t-1900)2|
|Equatorial radius of Earth ||3963.34 statute mi|
|Polar radius of Earth ||3949.99 statute mi|
|Earth's mean radius ||3958.89 statute mi|
|Oblateness of Earth ||1/297|
|Equatorial horizontal parallax of the moon ||57'2'.70|
|Earth's mean velocity in orbit ||18.5 mi/sec|
|Sidereal year ||365d.2564|
|Tropical year ||365d.2422|
|Sidereal month ||27d.3217|
|Synodic month ||29d.5306|
|Mean sidereal day ||23h56m4s.091 of mean solar time|
|Mean solar day ||24h3m56s.555 of sidereal time|
1. Actual mean distance derived from radar bounces: 92,935,700 mi. The value of 92,897,400 mi (based on parallax of 8".80) is used in calculations.
2. t refers to the year in question, for example, 2003.
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