With most of the East coast already blanketed in snow, it is difficult to believe that winter is just beginning in the Northern Hemisphere. For today, December 21st marks the first official day of winter. Often referred to as winter solstice, it is also the shortest day of the year.

Conversely, in the Southern Hemisphere, today marks the beginning of summer, also referred to as summer solstice or the longest day of the year. The roles will be reversed on June 21st.

The primary reason for the different seasons in the two hemispheres is that as the Earth rotates around the sun, it also revolves around its own axis. However, this rotation is not straight, but tilted at an angle of 23.5 degrees, causing there to be less light delivered to the Northern Hemisphere and more to the Southern Hemisphere at this particular time. The solstices occur when the sun is the furthest from Equator, the imaginary line that divides the Earth into the two hemispheres.

While we know the scientific reason behind the winter solstice today, for ancient cultures this day marked the turning point of the cold dark winters and the fear that the energy-giving sun was leaving them. That's because, after this date, the days started to become longer again, and while many months of winter remained, people knew that the sun would be back.

They therefore not only performed elaborate ceremonies during this time but also, built some of their finest structures, which included tombs, temples, cairns and other sacred observatories.

One of the most famous examples of this is Stonehenge. Located in Wiltshire, England, this pre-historic burial site, is believed to have been constructed to celebrate the winter solstice. Hundreds of people still gather here each year, to celebrate a pagan tradition called Yule, one of the oldest known solstice-related events.

Another famous site is Newgrange in Boyne Valley, Ireland (see picture), which is thought to be over 5,000 years old. It is a huge stone structure that was designed to receive a shaft of light into its central chamber at the dawn of winter solstice.

The light, in turn, illuminates incredibly intricate carvings. The whole event lasts for about 17 minutes and is so popular even today, that tickets to view it are distributed via lottery. Historians estimate that it must have taken 300 men about 20 years to build such an elaborate structure in those ancient times.

In the USA, many cities have started their own winter solstice traditions. The city of Seattle holds a Fire Festival at the Seattle Center, which includes among other things, circus acts, fire-eaters and interpretive dancers. In Chicago, the day is celebrated with a Winter Festival that includes moonlight walks through a preserve and learning about animal survival and feeding habits, during the cold winter. With roasted chestnuts and hot chocolate served around a huge bonfire, this cozy event is quite popular in the windy city.

Do you have a favorite winter solstice tradition in your town or with your family? If so, be sure to share it with all of us, by adding your comments below.

wikipedia.org,seattlecenter.com,explorechicago.org