from 1,000,000 BC to 1,000,000 AD
Variations for 4,000 BC to 8,000 AD
According
to Meeus
(More Mathematical Astronomy Morsels, Chapter 33) Bretagnon
published in 1984 an algorithm for the eccentricity e valid
for a very long period of time:
The
time T is expressed in thousands of years from the epoch
1850.0. The sums have 19 terms.
This
method gives good results from 1,000,000 BC to 1,000,000
AD.
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The Earth's orbital eccentricity changes with a period of about 100,000 years in the range of to 0.06:
The mean value of the eccentricity is 0,02674, the present value is 0.01670.
The
perihelon distance d_{P} for an ellipse of semimajor
axis a and eccentricity e is:
d_{P}
/ a = 1  e The
amount of solar radiation S received by the Earth
(
"insolation")
is proportional to the square of the inverse:
d_{P}/a = 1  e
S / S_{2000}
from 2000
d_{A}/a = 1 + e
S / S_{2000}
from 2000
Perihelion Aphelion The
difference of the insolation at perihelion and at aphelion
is 7 % at present, and 17 % for the maximum
eccentricity.
For the minimum value of the eccentricity e the amount of
solar radiation received by the Earth (insolation) is 3 %
less than at present, and for the maximum value of e the
radiation is 9 % greater than at present.
For the minimum value of the eccentricity e the amount of
solar radiation received by the Earth (insolation) is 3 %
greater than at present, and for the maximum value of e the
radiation is 8 % less.
Variations for 4,000 BC to 8,000 AD
(c) 2006 J. Giesen
2006, Mar 24