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Venus Synodic Period

  1. Feb 16, 2006 #1
    The passage below is quotted from wikipedia:

    "The cycle between one maximum elongation and the next lasts 584 days. After these 584 days Venus is visible in a position 72 degrees away from the previous one. Since 5 * 584 = 2920, which is equivalent to 8 * 365 Venus returns to the same point in the sky every 8 years (minus two leap days). This was known as the Sothis cycle in ancient Egypt, and was familiar to the Maya as well. Another association is with the Moon, because 2920 days equal almost exactly 99 lunations (29.5 * 99 = 2920.5)."

    My question is why it will be 72 degrees away?
  2. jcsd
  3. Feb 16, 2006 #2

    If the max. elongation cycle would coincide every two years then every 730 days it would occur at the same point in the sky.
    Since the actual cycle of 584 days is 146 days short of the full cycle, then it is fractionally short by 146/730 ths of the full 360* circle.
    (I think :uhh: )
    146da./730da. X 360 degrees of a full circle = 72 *

    Last edited: Feb 16, 2006
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