The Sun undoubtedly has a great effect on our lives , but perhaps more than we thought, and not only on daily or annual scales, but also throughout the centuries and millennia . To begin with, the Sun dictates our circadian rhythm and that is why the vast majority of people lead a daytime life and take advantage of the night to rest. These circadian rhythms are more evident when we disrupt them , when traveling, for example, to a remote destination in such a way that our body follows a time rhythm that does not correspond to that of the place where we are or when a person shifts their sleeping hours to the day, which which can cause insomnia and other health problems.
The Sun can also affect us seasonally, through seasonal affective disorders . The most common of these is the small depression that many people suffer in winter , due to the decrease in daylight hours that causes the decrease or increase of certain hormones in our body. We also need regular exposure to sunlight to synthesize healthy amounts of vitamin D and other essential compounds for the body.
Therefore, given the great effect that the king of stars has on our health and well-being, it is not surprising that it has been worshiped in so many cultures as a deity. However, the Sun not only affects us humans as individuals or as animals that we are, but also affects our environment , the world around us.
For example, a certain correlation is known between solar cycles lasting 22 years and periods of greatest drought. These 22-year cycles consist of two sunspot cycles, each lasting 11 years, between which an inversion of the magnetic field of said spots occurs. At the beginning of 8 of the last 9 cycles, more intense periods of drought have been observed in North America.
Another possible connection and whose study continues to this day is the one that could exist between the levels of solar activity and the increase in circulation in our atmosphere . This increase in circulation would be caused by an increase in the energy available in the system, which would cause greater meteorological activity. But these effects can also be felt on time scales beyond a year or a decade. In fact, the Maunder Minimum , a record low in solar activity and sunspot numbers that occurred for almost a century towards the end of the 17th century, coincided with the start of the Little Ice Age that affected Europe until the 19th century. . During this period there was a general drop in temperatures and there are numerous records of lakes and rivers beginning to freeze around this time, as well as a record of two years in which the Baltic Sea completely froze, the River Thames froze the height of London allowing its inhabitants to hold fairs on it and the Swedish army crossed to Denmark on the ice in 1658 to attack Copenhagen. Today it is known that this period of low temperatures had part of its origin in an increasing volcanic activity , although solar activity could also have had an influence.
Another much better understood and studied relationship is that between solar activity and disturbances in the Earth’s magnetic field . Particles emitted during solar flares or coronal mass ejections reach Earth and cause much more powerful and bright auroras. The same thing happened on September 1, 1859. The Sun’s emissions caused northern lights that were observed in Havana, Hawaii and Rome .
In recent years we have begun to study and understand how solar activity can affect our telecommunications networks , the electrical system and our technology in general. At present we are not able to predict when, where or with what intensity these solar flares that can affect our technological society so much will occur, although this is an area of growing study due to its economic and social importance.
Something that will certainly affect our planet, although probably not humans or at least not you and me specifically, will be the increasing luminosity of the Sun as part of its stellar evolution and its journey through the main sequence. This increasing luminosity is believed to be sufficient to speed up the evaporation of the Earth’s oceans in about 500 million years , so that liquid water will have disappeared from the Earth’s surface in about 1 billion years. Long before this happens , life will have disappeared from the face of the Earth , although other bodies in the solar system, such as Titan or other large moons in the solar system, could achieve favorable surface conditions at this time for the presence of liquid water.
Brehm N, Bayliss A, Christl M et al. Eleven-year solar cycles over the last millennium