Winter solstice 2012 is on Thursday 21 June
Sunset on Port Hacking, Sydney, NSW on 17 May 2012. Photo Nick Lomb
The winter solstice is the day when the Sun reaches its furthest north position in the sky and starts moving back towards the south. It marks one of the main turning points in the year with the others being the equinoxes and the summer solstice in December. This year winter solstice is on Thursday 21 June. From that day on the days start becoming longer and night time shorter.
In ancient Europe the winter solstice (in December in the northern hemisphere) was a time of celebration. The Romans had a week-long celebration called Saturnalia during which all wars had to stop and courts did not try criminals. Later this festival became Dies Natalis of Sol Invicti or the Birthday of the Unconquerable Sun celebrated on 25 December each year.
Changes in the length of daylight in Sydney around the time of the winter solstice. Chart Nick Lomb
As indicated above the length of daylight, that is the time between sunrise and set, starts increasing from the time of the solstice. From then on we can start to look forward to longer days, but only slowly. As can be seen from the chart, there is no noticeable change from day to day on the days immediately before and after the solstice. The name solstice comes from this fact as it means the Sun stands still. Soon though the length of daylight starts to increase.
In many countries the seasons are fixed in reference to the four astronomical turning points so that we could take the start of winter from the day of the solstice. In Australia, however, the seasons traditionally start on the first of the appropriate month so that winter has already begun on 1 June. This fits in well with our weather for it takes a while for the ground and the oceans to come into equilibrium with the minimum of heat received from the Sun at this time. The coldest days hence tend to be in the middle of July and so in the middle of the three-month winter period.
On Thursday 21 June we have reached the shortest day of the year. From now on things are bound to improve. Let’s celebrate!