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Little-known facts about lunar eclipses

By: Astrodamus
Last night's total lunar eclipse (in conjunction with the winter solstice no less) was awesome to see. It also had us here in Colorado Springs one-upping each other with eclipse trivia. Little-known eclipse fact #1: The impending eclipse had us debating how the Moon looks from the southern hemisphere. In Australia, the Moon phases appear backward because we are looking "down" toward the equator from Colorado while those in Australia are looking "up." We put together a scenario in STK to show this: Little-known eclipse fact #2: Eclipses are easy to predict if you know some orbital mechanics, but most people don’t. One major reason for the difficulty is that neither the Earth’s orbit about the Sun, nor the Moon’s orbit about the Earth, are circular. The noticeable eccentricities lead to some interesting (and sometimes useful) phenomena, just as the Earth’s bulge makes Sunsynch possible. These phenomena include figuring out when Easter occurs. Something like the 14 days after the first lunation following the spring equinox. Little-known eclipse fact #3: Christmas is this week, but did you know that the phases of the Moon contribute to why we celebrate Christmas on 25 December? One account is that Mary conceived at the spring equinox, when all growth and renewal begins. Count nine months after that and you get 25 Dec on whatever calendar someone figured all of this out on. Then some countries (like England) refused to adopt the Gregorian calendar when the Pope mandated it in the late 1500s. (Guess why? Remember Henry VIII?) So the Julian calendar and the Gregorian calendar kept slipping until in the 1700s the discrepancy was 11 days. No one was sure which calendar to use for Christmas, so they celebrated for 12 days, just to be safe. The Russian Orthodox Church still uses the Julian calendar. They celebrate Christmas on 7 Jan in Russia. One reason that England had to change was that Easter was slipping farther and farther into the summer. George Washington was born on 11 Feb 1732 but had to celebrate his birthday on 22 Feb after England adopted the Gregorian calendar in 1758. If they had accrued time in an uninterrupted sequence of standard seconds in the beginning, this would not have been a problem. We have a whitepaper from the August AIAA GNC Conference “The Debate Over UTC and Leap Seconds” if this topic interests you. Happy holidays!
Posted: 12/22/2010 5:59:40 PM


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