This Friday is the winter solstice, an astronomical phenomenon that marks the beginning of astronomical winter and his hand reaches the longest night of 2018 in the northern hemisphere (and the shortest in the southern hemisphere), the 21 to 22 from December. These are the eight keys you need to know to welcome winter with ownership:
What is a solstice? "They are the moments of the year in which the Sun reaches its greater or lesser apparent height in the sky, and the duration of the day or night is the maximum of the year, respectively. This behavior is also reversed in each hemisphere, so this will be the Winter Solstice in the northern hemisphere, and summer in the southern hemisphere ", explains the doctor in Astrophysics Alfred Rosenbeg.
Thus, the day on which the winter solstice happens, the Sun reaches its maximum South declination (-23º 27 ') and during several days its maximum height at noon does not change. Therefore, this circumstance is called solstice (from Latin solstitium, which means "still sun") of winter. At this moment in the southern hemisphere, summer begins. The day of the winter solstice corresponds to the longest day of the year: around this date there is the day when the Sun rises later and the day when it sets sooner.
When is it produced exactly? The solstice, which marks the beginning of the astronomical winter, will be this Friday, December 21 at 23.23 in the peninsular Spain. The winter will last 89 days and 20 hours and end on March 20 with the beginning of spring.
Why does it change from one year to the next? "The reason why they do not happen exactly the same day and at the same time each year is that the terrestrial orbital period is not exact: it takes 365,2425 … days In a full turn around the Sun. To a large extent, this is compensated by the introduction of leap years but there are still small time differences that sometimes jump a day, "says Rosenberg, researcher and disseminator of the Institute of Astrophysics of the Canary Islands .
Actually, the variation is small. The beginning of winter can occur, at most, on four different dates of the calendar, always between December 20 and 23. Throughout the 21st century, winter will always start between 20 and 23 (official Spanish date), with its earliest start in 2096 and the latest, in 2003.
Is it the shortest day (and the longest night)? Indeed, it is the shortest day of the year in the northern hemisphere, that is, in which the sun is less than the horizon, and the longest in the south and we only have 9 hours and 17 minutes of sun, in front of us. at 3 pm and 3 minutes, which lasted the longest day of the year, on June 21.
Since when do we know the solstices? "The oldest civilizations (even extremely isolated, such as the one of Easter Island) already knew these ephemeris perfectly, there being festivities related to these in almost all civilizations. There are even those who propose that in Stone age they could have already possessed this knowledge, "Rosenberg explains.
And Christmas, what does it have to do? "Just as the full Moon marks Holy Week and the Carnival, Christmas or the night of San Juan may be related to the solstices, festivities possibly inherited from pagan festivities. It will be difficult to confirm or deny this point, "adds the astrophysicist.
Mónica Cornejo Valle, professor of Anthropology of Religions of the Complutense of Madrid, emphasizes that "some historians maintain that the celebrations that on our calendar coincide with the end of December and the beginning of January have their origin in the agrarian cults that would celebrate the Winter Solstice, the time when the days begin to lengthen again ". The Romans celebrated the festivities dedicated to Saturn, god of time and agriculture, which included the exchange of gifts and ended with the festivities of the Unconquered Sun on December 25.
The Winter Solstice It is celebrated today by many cultures. In Peru, it is the Inti Raymi, an Inca ceremony that pays tribute to the Sun. In Bolivia, the Willka Kuti, which in Aymara means "the return of the sun" and the Chileans and Argentines gather in the festival of Mapuche origin We Tripantu. In Guatemala there is a dance of the flyers, in which several people revolve and dance around a stake, and in Scandinavia, the festival of Juul.
In Spain, the dolmens of the town of Antequera in Malaga celebrate the festival with a special activity and the City Council of Madrid prepares a "great parade of light" with thousands of lanterns to celebrate in Madrid Rio the longest night of the year.
How will be the weather like? According to Meteorology Statal Agency, for January and February "there is a greater probability that the temperature reaches higher than normal values in the eastern half of the peninsula and the Balearic Islands". In the rest of Spain "there are no significant differences". As for the rains, "there is a greater probability that rainfall is higher than normal in the Iberian Peninsula and the Balearic Islands. In the Canary Islands there are no significant differences. "
What do the heavens bring us this winter? During this season, we will have several phenomena in our sky, from a partial solar eclipseBetween January 5 and 6 only visible from Asia to a total eclipse of the moon on January 21 which will be visible in Spain.