This afternoon, at 17:58 Greek time, the Sun will be at Winter Solstice, so will start and typically this winter in Greece and more generally in the northern hemisphere. Tonight will be the longest of the year lasting about 14.5 hours, according to Dionysis Simopoulos, honorary director of the Eugenides Planetarium. In fact, it will coincide with the peak of the last rain of the year, the Arctic.
Etymologically, according to the National Observatory of Athens, “solstice” comes from the words “sun” and “I stand” or “stop”. Near the winter solstice (a few days before or after) the Sun seems to be slowing down its apparent movement to the south. On the day of the solstice this motion is zeroed and then reversed.
During the winter solstice the Sun reaches its lowest point at dusk and then we spend the longest night of the year. The equinoxes are the days of the year where the length of the day is equal to the length of the night. Every year two equinoxes occur.
The phenomena of equinoxes and solstices occur on all the planets of each solar system, whose axis of rotation is inclined with respect to the plane of rotation around their star. Solstices and equinoxes occur because not all days of the year are equal in length. In summer the days are longer and the nights shorter, while the opposite happens in winter, when the days are shorter and the nights longer. This is because, as our Earth orbits the Sun, its axis of rotation is inclined to the plane of orbit, about 23 ° 26 degrees, and this plane is called the ecliptic.
As a result of the inclination of the axis of rotation in half a year (from the spring to the autumnal equinox – March 20 to September 22) the northern hemisphere “tilts” towards the Sun, with the maximum being observed around June 21, at the summer solstice, while in the other half of the year the southern hemisphere is the one that “leans” more towards the Sun, with the maximum around December 21, at the winter solstice. Solstices and equinoxes essentially determine the length of the seasons.
According to D. Simopoulos, the winter solstice today is between the 20th and the 23rd of December, although the last time it happened on the 23rd of December was in 1903 and the next one will be in 2303. Even more rare is the 20th of December, with the next to happen in 2080. These differences are due to the Gregorian Calendar, which each year has 365 days, except for the leap years with their 366 days.
The ancient peoples especially celebrated the days of the winter solstice. This tradition was continued by the Greeks with Saturns and the Romans with Saturnalia from December 18 to 24 and the central celebration of December 25, the “Day of the Birth of the Invincible Sun”, when the fact was celebrated that the Sun was beginning to rise again. in heaven and let the days grow. The first Christians, who were outlawed in Rome and could not meet or attend church together, held meetings secretly in their catacombs. They decided to celebrate Christmas on December 25, when the Romans were busy with their own feasts of Saturnalia.
But why does the winter solstice not occur today on December 25, as in the time of Christ, but on December 21? The problem, according to Mr. Simopoulos, begins with the Julian Calendar introduced by Julius Caesar in 44 BC, which had its own imperfections, because it lost one day every 128 years. The Julian calendar had established the winter solstice on December 25, but over the years the added small error had shifted the actual date of the winter solstice.
Thus in 325 AD, the year of the Council of Nicaea, the winter solstice was postponed and occurred on December 22. However, the transfer of the winter solstice continued without correction until the year 1582, when the winter solstice occurred on December 12. Then, Pope Gregory XIII introduced a new reform, which is why the new calendar, the one we use today, is called Gregorian, and loses only one day in 4,000 years. The Gregorian Reformation shifted the position of the calendar forward based on the year of the Council of Nicaea and not the year of the introduction of the Julian calendar, 44 BC. That is why the winter solstice occurs today on December 21st.