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The Earth's "orbital variance" is the "in breath and out breath" of the Earth's orbit over geologic and astrological "macro"ages.
The length of a solar day (Earth's polar axis rotation) remains quite constant from year to year and age to age. The difference between the tropical year (calendar) and the sidereal year (transiting fixed stars) is called "Precession".
Precession according to my "Orbital Variance Theory", is caused by "slight" contraction of the earth's orbit over very long periods of time.
The tilt of the Earth on her axis accounts for seasonal changes; the expansion and contraction of the Earth's orbit accounts for the extraordinarily "wide" global climate fluctuations.
The global climate fluctuations extend from Ice Ages to Great Floods and perhaps, even beyond. Orbital fluctuations are, in my opinion, the real cause of our present condition of "global warming".
The "Great Flood" period occurred somewhere between the Ice Age (Earth farthest from the Sun) and whatever opposite conditions arise as the Earth's presently contracting orbit continues to gradually, but constantly, draw us nearer to the Sun.
The Orbital Variance Theory also includes a recession of the equinox which is the bi-polar companion to our present observation of PREcession .
The expanding and contracting of the Earth's orbit takes place over such expansive periods of time that recorded history would make no mention nor observation of recession.
The precessional period occurs during the gradually contracting phase of the Earth's orbit.
The recessional period occurs during the "expanding" phase.
Theoretically there is a mean period where the solar year and sidereal year are identical. This mean period can be easily computed.
The first edition of The Encyclopaedia Britannica, 1771 (Astronomy, page 453) records the length of the solar year as 365.2564 days and the Earth's mean distance from the Sun at 94,725,840 miles. The astronomical measurements from 1771 are greater than our present calculations (365.2422 and 93,000,000+/-) and indicate that our orbit is presently in a contracting phase with global warming as a natural result.
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