Those solar panels on your roof will struggle a bit today; it is the shortest day of the year, and the sun is low in the sky, with its light travelling through the most atmosphere. Tim Wall at Discovery News notes that it is a very important day in history:
In the northern hemisphere, knowing when the dark days of winter would start to lengthen could give hope to people trying to make the harvest of the previous year stave off starvation for a few more months. The day was so important, that some of humanity's earliest monumental structures were aligned with the rising or setting of the sun on the winter solstice. Stonehenge in England, for example, is lined up with the winter solstice.
Tim also notes that it is party time:
The Romans celebrated Saturnalia around the time of the solstice with revelry and a social switcheroo in which masters served the slaves. Further north, Germanic and Norse tribes celebrated Yule by burning a massive log in honor of Thor, a tradition some still observe.
Others have started new traditions; in Toronto, they take back the streets for a parade and festival, "non profit, hand made and commercial free since 1987." It is a glorious sight.
I love the winter solstice; from now on, for those of us in the northern hemisphere, every day will be a little bit brighter and a little bit longer. Happy Solstice to you all.