Tuesday, March 21, 2006

Tuesday Beakful of Astro-Knowledge

The Earth wobbles slightly (about 23.5 degrees from vertical) on its axis, due to the same forces that make a toy top wobble slightly as it spins. The technical term for the wobble is "precession," and it takes about 25, 800 years for the earth to complete one precession cycle, where the projection of the Earth's axis traces out circle against the backdrop of the stars.

This phenomenon has two practical effects for Earthlings. First, the pole stars change periodically as the axis traces out that circle. Second, the signs of the Tropical Zodiac (the one used for most newspaper horoscopes) drift out of sync with the position of the sun on the Zodiac. Details on both in future Beakfuls. Stay tuned to find out what your actual astrological sign is.

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