Today remained unseasonably mild, so I decided take two vacation hours and visit the UMass Sunwheel for the 3:30 program on the Winter Solstice, which happened this morning in the wee hours.  Those of you who have followed my blog since the beginning will recall that I’ve posted about this event before, but hey, I like going out there and reflecting on the seasons, so bear with me again.

The crowd gathers at the center of the circle of stones.

This year, Professor Judith Young, driving force behind the creation of the Sunwheel, was unable to be with us; UMass astronomer Steven Schneider hosted the event in her place.  Dr. Schneider began with an overview of the Sunwheel and the science behind the weather patterns we observe on a daily basis.  Like Stonehenge, the UMass Sunwheel marks the changing of the seasons, which themselves are due to the earth tilting on its axis.  At the Winter Solstice in the northern hemisphere, we experience the longest night of the year, and the shortest day, because at this point in the year, the earth’s North Pole is tilted farthest away from the sun.  Temperature lags behind sunlight, so we’ll experience the coldest weather of the year about a month from now.

Professor Schneider gestures at the tall standing stone.

There’s always a lot of information to absorb from these sessions; this time around I want to pass along some of the cultural lore that was discussed. For example:

• The main axis of the Temple of Luxor, built in Egypt around 1400 BCE, is oriented to the Winter Solstice
• The main axis of Stonehenge on Salisbury Plain in England, built around 2600 BCE, is oriented to the Summer Solstice
• Knowing when the seasons changed was important to pre-literate agricultural societies because they could plant crops and harvest according to the calendar, rather than on a whim
• Because they were people of the tropics, Polynesians did not conceive of the sky as a celestial sphere, but rather as a celestial cylinder
• Rising of bright stars such as Sirius and Arcturus was tracked by ancient astronomers, so the UMass Sunwheel includes stone markers for these
• Eclipses fascinated ancient astronomers and remain dazzling phenomena for us moderns as well
• On 20 May 2012, an annular eclipse of the sun will be visible in New Mexico; on 13 November a total solar eclipse will be observable in Australia
• Our moon’s orbit wobbles and precesses over an 18.6 year cycle; we experienced a Major Lunar Standstill in 2006 so the next Minor will be in 2015
• The earth’s orbit precesses over a 25,000 year cycle, which means that astrological tables based on zodiac signs developed 2000 years ago are now off by about a month

A low-lying cloud obscured the horizon, but we all, about 50 of us, were glad we stayed to see the sun set around 4:20 pm.

The sun sets behind the Winter Solstice standing stone on 22 December.