I meant "angular momentum", not just momentum. Sorry. -----Original Message----- From: sundial-boun...@uni-koeln.de [mailto:sundial-boun...@uni-koeln.de] On Behalf Of Hank de Wit Sent: Friday, 25 March 2011 11:23 To: Sundial List Subject: RE: varying speed? [SEC=UNCLASSIFIED]
Hi Brent, Indeed it does change Brent. The Earth's orbit is slightly elliptical with the Sun at one of the foci of the ellipse, which means during part of it's orbit the Earth is closer to the Sun than 6 months later. Due to conservation of momentum (remember the ice-skater pulling their arms in while spinning and getting faster) the Earth moves faster in it's orbit when closer to the Sun. This is also known as Kepler's second law, "a line joining a planet and the Sun sweeps out equal areas during equal intervals of time". See: http://en.wikipedia.org/wiki/Kepler's_laws_of_planetary_motion Many regards Hank de Wit Adelaide, Australia -----Original Message----- From: sundial-boun...@uni-koeln.de [mailto:sundial-boun...@uni-koeln.de] On Behalf Of Brent Sent: Friday, 25 March 2011 11:03 To: Sundial List Subject: varying speed? 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 --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial
