Saturday, December 22, 2007

Happy Solstice!

The solstice occurs now, on 22 December 2007 at 1:08 AM EST (06:08 UT).  It is the moment that the Sun is farthest from the celestial equator.   It is when the Earth's axis is aligned with the line between the Earth and Sun such that the Northern Hemisphere is tilted away, and the Southern Hemisphere towards the Sun. 

This makes today the shortest day of the year and the start of winter here in the Northern Hemisphere, and  the longest day of the year and the start of summer in the Southern Hemisphere. 

Above is the oldest solar observatory in the Americas, in Chankillo, Peru.  It has been there since the 4th century BC, but it was just discovered this year.  The point where the Sun rises moves up and down the 300m length of the hill, from solstice to solstice.

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