21 March 2008

Spring has Sprung

With the Vernal Equinox having just passed, and the Full Moon occurring today, the conditions for Easter have been met. Roughly, Easter happens on the Sunday after the first full moon of spring. Easter can be no earlier than 22 March, because the ecclesiastical reckoning of spring is fixed at 21 March. Interestingly, Easter, this year on 23 March, last happened on 22 March in 1818, and won't happen again on that "earliest" date until 2285. The latest date for Easter is 25 April. The spring moon, or paschal moon, is also not astronomically exact. Tables based on lunar months are used to determine new and full moons so that churches all over the world can have a fixed calendar. The notion of a "month" is full of amazing complexities, since our moon and our sun hurl through space on their own schedules. We'd love to be able to divide up the seasons in nice, neat, 30-day months in (12 x 30) 360-day years, but nature doesn't cooperate. Sit down sometime and wrap your mind around sidereal and synodic orbital periods. A humbling endeavor, to be sure. Here in Siskiyou County, the winter is slowly slipping away as the sun climbs higher in the sky. I'm looking forward to a beautiful spring.

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