Your question brought to my mind an old doubt. As the points of perihelion and aphelion are continually changing (in a very slowly way, but they are), so the EoT is also changing from an year to another, right? I mean, if a century ago perihelion and aphelion occurred not in january and july, but in december and june (it's only an example, I don't know how much time does it need to change), then the EoT was different.
2011/3/25 Marcelo <mmanil...@gmail.com> > Hello Brent, > > as long as I know, the Earth's speed really has a variation throughout the > year, for its orbit being ellliptical, with the Sun in one of the ellipse > focuses, it is faster when nearer to the sun (perihelion) and slower when > its at maximum distance from it (aphelion). > > Both the perihelion and aphelion are upon the ellipse's major axis. > > As a result, the sun's apparent ecliptical longitude changes a little > slower in july than it does in january. > > Further, as Earth's axis has a declination of ~ 23.5 degrees, that means > that the Sun's apparent longitude measured upon the Equator is slightly > different of its ecliptical longitude (measured upon the Earth's orbit > plan). > > So, neither is the Sun moving from West to East regulary throughout the > year, neither is its movement on the ecliptic equal to that on the Equator - > if Sun moves 1 degree with relation to the ecliptic, it may move 58 minutes > of arc with relation to the celestial equator. > > > 2011/3/24 Brent <bren...@verizon.net> > >> Hello again; >> >> I read this at: >> http://www.sundialsoc.org.uk/HDSW.htm >> >> Part 17 >> >When we look at the Sun we are observing it from a moving >> >platform. It is the varying speed around its elliptical >> >orbit and the tilted axis which are responsible for the >> >daily variations accounted for by the Equation of Time. >> >> I'm confused about the varying speed part. >> Does the earth actually change speed as it travels around >> the sun or is it just the way we perceive it? >> >> thanks again; >> brent >> >> --------------------------------------------------- >> https://lists.uni-koeln.de/mailman/listinfo/sundial >> >> >
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