MadSci Network: Astronomy |
Thank you David, an excellent question! So is the apsidal precession 112ky or 134 ky - which answer is right? I could not determine the source for the Calendar Wiki data. However the short answer: neither, or perhaps both. Allow me to explain. First the basics. The earth's orbit is not a perfect circle. It follows an elliptical path thru the heavens. The period apsidal precession is about 112,000 years. Calculations need to account for gravitational influences, which is not necessarily limited to that of the earth and sun. If attempting to measure, what's your reference? The solar system itself is following an orbit through our galaxy. According to E.M. Standish, the observed precession of earth's perihelion is 11.45 arc-seconds/year, which computes to approximately the 112 year number quoted. I hope this answers your question. For more reading, I would suggest: http://www- spof.gsfc.nasa.gov/stargaze/Sprecess.htm http://www.astro.gla.ac.uk/honours/labs/solar_system/papers/laskar.pdf a> h
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