The planet Earth goes around our star, the Sun. Along its trajectory it passes through different distances with respect to it. When it reaches winter solstice it agrees that it is the shortest day and the longest night in the northern hemisphere and conversely in the southern hemisphere. This day is usually the December 21.

The winter solstice is a key event that marks a change in the natural and astronomical cycles. Starting from the winter solstice, in the northern hemisphere the nights begin to gradually shorten until the summer solstice in June.

What happens on the winter solstice?

Planet Earth reaches a point on its path where the Sun's rays strike the surface in the same way more oblique. This happens because the Earth is more inclined and the rays of the Sun hardly arrive perpendicularly. This causes fewer hours of sunlight, making it the shortest day of the year. For more details on this phenomenon, you can consult this related article.

There is a misconception in general society about winter and summer depending on the distance from the Earth to the Sun. It is understood that summer is hotter because the Earth is closer to the Sun, and winter is colder because we are farther away. However, the Earth's orbit around the Sun, known as its orbit, is elliptical. At the vernal and winter equinoxes, the Earth and the Sun are in alignment. at the same distance and on the same inclination. However, contrary to popular belief, the Earth is closer to the Sun in winter and further away in summer. How can it be then that we are colder in winter?

More than the position of the Earth with respect to the Sun, what influences the temperatures of the planet is the tilt with which the sun's rays hit the surface. In winter, at the solstice, the Earth is closest to the Sun, but its tilt is the highest in the Northern Hemisphere. That is why when the rays reach the earth's surface too inclined, the day is shorter and they are also weaker, so they do not heat the air as much and it is colder. In the southern hemisphere the opposite occurs. The rays hit the earth's surface in a more perpendicular and direct way so that for them, on December 21, summer begins. This situation of the Earth with respect to the Sun is called Perihelion.

On the other hand, in summer, the Earth is the furthest from the Sun in its entire trajectory. However, the inclination in the northern hemisphere makes the Sun's rays fall more perpendicular to the northern hemisphere and therefore it is warmer and the days are longer. This situation of the Earth with respect to the Sun is called Aphelion.

The winter solstice and culture

Throughout history, humans have celebrated the winter solstice. For some cultures the beginning of the year is December 21, coinciding with the onset of winter. Some Indo-European tribes also had festivities and rituals celebrating this day. The Romans celebrated Saturnalia, in honor of the homonymous god, and in subsequent days they paid homage to Mithras, in honor of the deity of light inherited from the Persians. You can learn more about the history and interesting facts about the winter solstice at this link: curiosities of the solstice.

For ancient traditions, the winter solstice represents the triumph of light over darkness. It's curious that this is so even though there are fewer hours of daylight in winter. However, this is because, starting with the winter solstice, the nights will become increasingly shorter, and therefore, the day will conquer the night.

The winter solstice also gives rise to many pagan festivals and rites. December 21 was celebrated in the Stonehenge since the Sun of the winter solstice aligns with the most important rocks of this monument. Today in Guatemala, the winter solstice is still celebrated through the ritual of the "Dance of the flyers". This dance consists of several people turning and dancing around a stake.

Goseck's circle

This circle is located in Germany in Saxony-Anhalt. It consists of a series of concentric rings that are nailed to the ground. It is estimated, according to archaeologists and historians around it 7.000 years old and that it was a site of religious rituals and sacrifices. When they discovered it, they noticed two doors in the outer circle aligned with the winter solstice. This suggests that its construction was due to a kind of tribute to this time of year.

Stonehenge, Great Britain

As we mentioned earlier, the winter solstice was also celebrated at Stonehenge, thanks to the sun's rays aligning with the central altar and the sacrificial stone. This monument is about 5.000 years old and is known throughout most of the world, having been an important site for rituals and astronomical observations for hundreds of years. If you'd like to learn more about the solstices and equinoxes, you can consult this article on solstices and equinoxes.

Newgrange, Ireland

There is a mound built hace 5.000 años Covered in grass and riddled with tunnels and canals in northeast Ireland. Only on the day of the winter solstice does the sun enter all the main chambers, which, according to some experts, indicates that the structure was built to commemorate this date. To better understand the phenomena associated with winter, you can read about interesting curiosities of winter.

Tulum, Mexico

On the eastern coast of Mexico, on the Yucatan Peninsula, Tulum is an ancient walled city that belonged to the Mayans. One of the buildings built there has a hole in the top that causes a flare effect when the day of the winter and summer solstice lines up with it. This building remained intact until the Mayan population fell with the arrival of the Spanish.

Why does the date of the winter solstice change from year to year?

The day that winter begins can occur on different dates, but always around the same days. The four dates on which it can occur is between December 20 and 23, Both inclusive. This is due to the way the sequence of years fits into our calendar. It depends on whether the year is a leap year or not and the length of each of the Earth's orbits around the Sun. When the Earth makes one exact revolution around the Sun, it is known as a tropical year. You can find more information about the difference in dates for the winter solstice by consulting this meteorological explanation.

Throughout our XNUMXst century, winter will begin in the days 20 22 of the December.

The winter solstice and climate change

Natural variations of the Earth's orbit, including those related to precession, redistribute, over extended periods of time, the incident solar radiation on the earth's surface.

Earth's precession or wobble is the spinning top-like motion of the Earth's axis. The axis describes an imaginary circle in space and makes a revolution. every 22.000 years. What does this have to do with global warming and climate change?

Precession of the Earth. Source:: http://www.teinteresasaber.com/2011/04/cuales-son-los-movimientos-de-la-tierra.html

Over the past million years, these subtle variations in the Earth's axis have triggered significant decreases and increases in atmospheric concentrations of methane and carbon dioxide. It is known that greenhouse gas concentrations respond mainly to variations during the boreal hemisphere summer, that is, the time of year when the north pole points to the Sun.

Summer heat in the Northern Hemisphere reaches its peak once every 22.000 years, when the northern summer coincides with the Earth's closest approach to the Sun, and the Northern Hemisphere receives the most intense solar radiation. To understand the relationship between climate and seasons, you can consult this article about the seasons of the year.

On the contrary, the summer heat reaches its minimum 11.000 years later, once the earth's axis has turned to have the opposite orientation. The northern hemisphere will then have the minimum summer solar radiation because the Earth is in the position further away from the sun.

Methane and carbon dioxide concentrations rose and fell in harmony with changes in incident solar radiation on planet Earth throughout the last 250.000 years.

At the winter solstice, the sun's rays are weaker.[/caption>

Every 11.000 years there is a winter solstice which is warmer since the incident solar radiation in the northern hemisphere is greater and, on the contrary, there is another winter solstice when completing the precession lap, which is colder Since the sun's rays arrive at a more slanted angle. It's said that greenhouse gas concentrations are increasing naturally because we're approaching the precession period, when the planet receives more solar radiation. However, we know very well that naturally, they wouldn't increase that much. It's due to human activities that the average global temperature is rising so dramatically.

With all this you can know a little more about the Winter Solstice and its relevance in world cultures and throughout history.