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Old 03-04-2012, 11:21 PM   #79
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Arrow Axial tilt

In astronomy, axial tilt, known to astronomers as obliquity, is the angle between an object's rotational axis, and its orbital axis, or, equivalently, the angle between its equatorial plane and orbital plane. It differs from orbital inclination.

In the solar system, the Earth's orbital plane is known as the ecliptic plane, and so the Earth's axial tilt is officially called the obliquity of the ecliptic. It is denoted by the Greek letter ε...Epsilon (uppercase Ε, lowercase ε or lunate ϵ; Greek: έψιλον) is the fifth letter of the Greek alphabet...The initial sound value of Ε was determined by the vowel occurring in the Phoenician letter name He, which made it a natural choice for being reinterpreted from a consonant symbol to a vowel symbol denoting an [e] sound...E flat major is the fundamental key of Freemasonry...

Because the planet Venus has an axial tilt of 177° its rotation can be considered retrograde, opposite that of most of the other planets. The north pole of Venus is "upside down" relative to its orbit. The planet Uranus has a tilt of 97°, hence it rotates "on its side", its north pole being almost in the plane of its orbit...Over the course of an orbit, the angle of the axial tilt does not change, and the orientation of the axis remains the same relative to the background stars. This causes one pole to be directed toward the Sun on one side of the orbit, and the other pole on the other side, the cause of the seasons on the Earth...

Last edited by lightgiver; 03-04-2012 at 11:23 PM.
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