The biannual event of the solstice is upon us – summer – the longest day of the year or – winter – the shortest day. In the northern hemisphere it is summer, in the south it is winter. This is happening on Sunday June 21, 2015. During the following six months the cycle will be reversed until on December 22 and the winter solstice will take place in the north.
So, what are these events and why do they deserve at least a passing nod. They mark the changes of the four seasons which affect all of us. Sunday, in the northern hemisphere, is the longest day with the greatest amount of sunlight falling on the northern part of Earth. Warm / hot weather occurs shortly before and afterwards. The reason for the regular seasonal transitions are caused by the Earth’s tilt on its axis relative to its orbital plane. This allows progressive variations of the amount sunlight reaching the ever changing surfaces, from north to south and vice versa, of the Earth during its orbit of the sun.
Among the most obvious other events following solstices are that they approximately mark the halfway point between the changes of the clocks to summer time, and later in the year to winter time wherever day light saving is used.
In history different peoples have assigned various meanings such as the tradition of ancient Egyptians who believed that they regulated the volumes of water in the Nile which was of great importance to their agriculture. Thus, their annual calendar coincided with the solstices.
In England the Stonehenge historical site with its large stone tablets constructed about 5,000 years ago, form a circle aligned with midsummer sunrise and midwinter sunset. The exact purpose is unclear but may have been used for ancient astronomy and fixing the dates of annual rituals.
The fact of the existence of solstices have thus been known from antiquity. Modern technology enables us the fix the exact time to the minute when the Earth will be at the furthest position in its orbit relative to either the most northern or southerly point.
If you happen to have read this very abbreviated rationale noting why the solstice on Sunday is of some brief interest, have a good day and enjoy whatever the weather that follows may be.