Saturday, February 28, 2004
About time [25770]
The Earth wobbles. It wobbles on its axis like a spinning top, but very very slowly, which is why you've never noticed. It leans at an angle of 23.5° and gradually spins round once every 25770 years thanks to a phenomenon called precession of the equinoxes. At present the North Pole points pretty much towards Polaris, a small star in the constellation of Ursa Minor, but this gradually changes as the Earth's axis traces out a giant circle in the sky. In 2000 BC our pole star was Thuban, in the constellation of Draco, and around the time of Julius Caesar there was no pole star at all. Polaris reaches its closest to the pole in AD 2102, then the pole moves on to Alderamin in AD 7500, Deneb in AD 10000 and the bright star Vega in AD 13000. As the constellations shift in the sky, so the signs of the Zodiac also shift from their original positions, moving backwards one sign every 2150 years. The Spring Equinox isn't really in Aries any more, it's been travelling through Pisces for the last two millennia and is now entering Aquarius. Which is just one reason why astrology is bollocks.
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