What causes the seasons?
· A season is a subdivision of the year, marked by changes in weather, ecology, and hours of daylight. Seasons result from the yearly revolution of the Earth around the Sun and the tilt of the Earth's axis relative to the plane of revolution...
· Tilt of Earth's axis causes sunlight to fall differently on Earth, at different times of the year.
Sidereal Day...
· A mean sidereal day is about 23 hours, 56 minutes, 4.0916 seconds (23.9344699 hours or 0.99726958 mean solar days), the time it takes the Earth to make one rotation relative to the vernal equinox. (Due to nutation, an actual sidereal day is not quite so constant.)
· How long it takes ANY star to make 1 full circuit through the sky.
Solar Day...
· one rotation of Earth: the time taken for the Earth to make a complete revolution on its axis, measured with respect to the Sun..... 24 HR day.
· average time it takes the sun to make 1 circuit through the sky
Precession...
· a change in the orientation of the rotational axis of a rotating body. It can be defined as a change in direction of the rotation axis in which the second Euler angle (nutation) is constant.
· A gradual movement that changes the orientation of Earth's axis, in space.
· Earth's precession takes approximately 26,000 YRS
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