The spring equinox was about at 3-20-2002 18:50 UT
Midsummer is about at 6-21-2002 13:10 UT
The autumn equinox is about at 9-23-2002 04:40 UT
The difference between the time from spring equinox to midsummer on one
hand and the time from midsummer to autumn equinox on the other hand is
about 21:10 hours.
One should suppose there will be no difference in time between the
positions of the sun at declination 23.44 to 0 and between the
positions at declination 0 and -23.44.
Can anyone give me an explication of this difference?
Willy Leenders,
you found experimentally that seasons have not the same lenght!! You found
also Equation-of-Time. Look at http://www.analemma.com/
My best regards
Piero Ranfagni
The equation of time contains two factors, one due to the inclination
of the Earths axis to the plane of its orbit and the other is due to
the variation in speed of the Earth in its orbit. See
http://www.uwrf.edu/sundial/Eqntime.html . The variation of speed
which is due to the elliptical nature of the Earth's orbit (Kepler's
Law of Areas) is the contribution which causes the effect Willy
Leenders describes. We are closest to the Sun on Jan 4th and hence
moving fastest, hence in the Northern hemisphere Winter is shorter
than Summer:-)
--
Emeritus Professor John P.G.Shepherd
Physics Department
University of Wisconsin-River Falls
410 S. 3rd. St.
River Falls,WI 54022
Phone (715)-425-6203
Fax (715)-425-0652
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