<P> In astronomy, axial tilt, also known 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 . </P> <P> At an obliquity of zero, the two axes point in the same direction; i.e., the rotational axis is perpendicular to the orbital plane . Earth's obliquity oscillates between 22.1 and 24.5 degrees on a 41,000 - year cycle; the earth's mean obliquity is currently 23 ° 26 ′ 12.8" (or 23.4369 °) and decreasing . </P> <P> Over the course of an orbit, the obliquity usually does not change considerably, and the orientation of the axis remains the same relative to the background stars . This causes one pole to be directed more 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 . </P>

The earth axis of rotation is always inclined at an angle of