Thank you Piero and John. But after your answers my problem remains.
1. The equation of time can explain no more than about 31 minutes. The difference I descirbe is 21 hours and 10 minutes. 2. I describe a difference between two parts of the elliptical orbit of the earth which are symmetrical with regard to the sun. It is not the difference between winter and to summer but the 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. I look out for a further explanation. Willy Leenders Flanders in Belgium 50.9 N 5.4 E mailto:[EMAIL PROTECTED] john shepherd wrote: > >On Mon, 25 Mar 2002, Willy Leenders wrote: > > > >> 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 > - -
