The sun is the most important natural factor for all life on Earth. Almost all ancient peoples had a cult of the Sun or its personification in the form of some deity. In those days, almost all natural phenomena were associated with the Sun (and, by the way, were not far from the truth). Man was too dependent on nature, and nature is highly dependent on the sun. A slight decrease in solar activity led to a decrease in temperature and other climate changes. The cold snap caused crop failures, followed by hunger and death. Given that fluctuations in solar activity are not short-lived, mortality was massive and well remembered by survivors.
Scientists have gradually come to understand how the sun “works”. The side effects of its work are also described and well studied. The main problem is the scale of the Sun compared to the Earth. Even at the present level of development of technology, mankind is not able to adequately respond to changes in solar activity. Do not count as an effective response in the event of a powerful magnetic storm, advice to cores to stock up on validol or warnings about possible failures in communication and computer networks! And this is while the Sun is operating in a “normal mode”, without serious fluctuations in activity.
Alternatively, you can look at Venus. For hypothetical Venusians (and even in the middle of the twentieth century, they seriously expected to find life on Venus), failures in communication systems would definitely be the least of the problems. The Earth's atmosphere protects us from the destructive part of solar radiation. The atmosphere of Venus only aggravates its effect, and even raises the already unbearable temperature. Venus and Mercury are too hot, Mars and the planets farther from the Sun are too cold. The combination "Sun - Earth" is thus unique. At least within the boundaries of the foreseeable part of the Metagalaxy.
The sun is also unique in that so far it is the only star available (with big, of course, reservations) for more or less subject research. While studying other stars, scientists use the Sun both as a standard and as an instrument.
1. The main physical characteristics of the Sun are difficult to represent in terms of values familiar to us; it is much more appropriate to resort to comparisons. So, the diameter of the Sun exceeds the Earth by 109 times, the mass is almost 333,000 times, the surface area is 12,000 times, and the volume of the Sun is 1.3 million times the size of the earth. If we compare the relative sizes of the Sun and the Earth with the space separating them, we get a ball with a diameter of 1 millimeter (Earth), which lies 10 meters from a tennis ball (Sun). Continuing the analogy, the diameter of the solar system will be 800 meters, and the distance to the nearest star will be 2,700 kilometers. The total density of the Sun is 1.4 times that of water. The force of gravity on the star closest to us is 28 times that of Earth. A solar day - a revolution around its axis - lasts about 25 Earth days and a year - a revolution around the center of the Galaxy - more than 225 million years. The Sun consists of hydrogen, helium and minor impurities of other substances.
2. The sun gives heat and light as a result of thermonuclear reactions - the process of fusion of lighter atoms into heavier ones. In the case of our luminary, the release of energy can (of course, at a rough to primitive level) be described as the conversion of hydrogen into helium. In fact, of course, the physics of the process is much more complicated. And not so long ago, according to historical standards, scientists believed that the Sun shines and gives heat due to ordinary, simply very large-scale, combustion. In particular, the outstanding British astronomer William Herschel, until his death in 1822, believed that the Sun is a hollow spherical fire, on the inner surface of which there are territories suitable for human habitation. Later it was calculated that if the Sun were entirely made of high quality coal, it would have burned out in 5,000 years.
3. Much of the knowledge about the sun is purely theoretical. For example, the temperature of the surface of our star is determined by color. That is, the substances that make up the sun's surface, at a similar temperature, acquire a similar color. But temperature is far from the only effect on materials. There is tremendous pressure on the Sun, substances are not in a static position, the luminary has a relatively weak magnetic field, etc. However, in the foreseeable future, no one will be able to verify such data. As well as the data on thousands of other stars that astronomers obtained by comparing their performance with the sun.
4. The Sun - and we, as inhabitants of the Solar System, together with it - are the real deep provincials of the Metagalaxy. If we draw an analogy between Metagalaxy and Russia, then the Sun is the most ordinary regional center somewhere in the Northern Urals. The Sun is located at the periphery of one of the not the largest arms of the Milky Way galaxy, which, again, is one of the average galaxies on the periphery of the Metagalaxy. Isaac Asimov mocks over the location of the Milky Way, the Sun and the Earth in his epic "Foundation". It describes a huge Galactic Empire that unites millions of planets. Although it all started with the Earth, the inhabitants of the empire do not remember this, and even the most narrow specialists even talk about the name of the Earth in a conjectural tone - the empire has forgotten about such a wilderness.
5. Solar eclipses - periods of time when the Moon partially or completely covers the Earth from the Sun - a phenomenon that has long been considered mysterious and ominous. Not only does the Sun suddenly disappear from the firmament, but it happens with great irregularity. Somewhere between solar eclipses, tens of years can pass, somewhere the Sun “disappears” much more often. For example, in Southern Siberia, in the Altai Republic, total solar eclipses took place in 2006-2008 with a difference of just over 2.5 years. The most famous eclipse of the Sun occurred in the spring of 33 AD. e. in Judea on the day when, according to the Bible, Jesus Christ was crucified. This eclipse is confirmed by astronomers' calculations. From the solar eclipse on October 22, 2137 BC. the confirmed history of China begins - then there was a total eclipse, dated in the annals to the 5th year of the reign of Emperor Chung Kang. At the same time, the first documented death in the name of science occurred. The court astrologers Hee and Ho made a mistake with the dating of the eclipse and were executed for incompetence. Calculations of solar eclipses have helped date a number of other historical events.
6. The fact that there are spots on the Sun was already well known at the time of Kozma Prutkov. Sunspots are like terrestrial volcanic eruptions. The only difference is in scale - spots are more than 10,000 kilometers in size, and in the nature of the ejection - on the Earth volcanoes eject material objects, in the Sun through the spots powerful magnetic impulses fly out. They slightly suppress the movement of particles near the surface of the luminary. The temperature, accordingly, decreases, and the color of the surface area becomes darker. Some stains last for months. It was their movement that confirmed the rotation of the Sun around its own axis. The number of sunspots that characterize solar activity varies with a cycle of 11 years from one minimum to another (there are other cycles, but they are much longer). Why the interval is exactly 11 years is unknown. Fluctuations in solar activity are far from being an object of purely scientific interest. They affect the Earth's weather and climate in general. During periods of high activity, epidemics occur more often, and the risk of natural disasters and droughts increases. Even in healthy people, performance is significantly reduced, and in those suffering from cardiovascular diseases, the risk of strokes and heart attacks increases.
7. Solar days, defined as the interval between the passage of the Sun of the same point, more often the zenith, in the firmament, the concept is very imprecise. Both the angle of inclination of the globe and the speed of the Earth's orbit change, changing the size of the day. The current day, which is obtained by dividing the conditional tropical year into 365.2422 parts, has a very distant relationship to the real movement of the Sun in the sky. Close numbers, nothing more. From the obtained artificial index, the duration of hours, minutes and seconds is derived by division. No wonder the motto of the Parisian guild of watchmakers was the words “The sun deceptively shows the time”.
8. On Earth, the Sun, of course, can help determine the cardinal points. However, all known ways of using it for this purpose are guilty of great inaccuracy. For example, the well-known method of determining the direction to the south using a clock, when the hour hand is oriented towards the sun, and south is defined as half the angle between this hand and the number 6 or 12, can lead to an error of 20 or more degrees. The hands move along the dial in a horizontal plane, and the movement of the Sun across the sky is much more complicated. Therefore, this method can be used if you need to walk a couple of kilometers through the forest to the outskirts of the city. In the taiga, dozens of kilometers from famous landmarks, it is useless.
9. The phenomenon of white nights in St. Petersburg is known to everyone. Due to the fact that in summer the Sun hides behind the horizon only for a short time and shallowly at night, the Northern capital is decently illuminated even at deep nights. The youth and status of the city play a role in the wide popularity of the St. Petersburg White Nights. In Stockholm, summer nights are no darker than St. Petersburg ones, but people live there not for 300 years, but much longer, and have not seen anything outlandish in them for a long time. Arkhangelsk The sun illuminates at night better than Petersburg, but not many poets, writers and artists have come out of the Pomors. Starting from 65 ° 42 ′ north latitude, the Sun does not hide behind the horizon for three months. Of course, this means that for three months in winter there is pitch darkness, illuminated, if and when you are lucky, with the Northern Lights. Unfortunately, in the north of Chukotka and the Solovetsky Islands, poets are even worse than in Arkhangelsk. Therefore, the Chukchi black days are as little known to the general public as the Solovetsky white nights.
10. Sunlight is white. It acquires a different color only when passing through the Earth's atmosphere at different angles, refracting through the air and the particles contained in it. Along the way, the earth's atmosphere scatters and attenuates sunlight. Distant planets, practically devoid of atmosphere, are not at all gloomy kingdoms of darkness. On Pluto during the day it is many times brighter than on Earth on a full moon with a clear sky. This means that it is 30 times brighter there than on the brightest of the St. Petersburg white nights.
11. The attraction of the moon, as you know, acts equally on the entire surface of the earth. The reaction is not the same: if the hard rocks of the earth's crust rise and fall to a maximum of a couple of centimeters, then ebb and flow occur in the World Ocean, measured in meters. The sun acts on the globe with a force similar in effect, but 170 times more powerful. But because of the distance, the tidal force of the Sun on Earth is 2.5 times less than a similar lunar impact. Moreover, the Moon acts almost directly on the Earth, and the Sun acts on the common center of mass of the Earth-Moon system. That is why there are not separate solar and lunar tides on Earth, but their sum. Sometimes the lunar tide increases, regardless of the phase of our satellite, sometimes it weakens at the moment when the solar and lunar gravitation act separately.
12. From the point of view of stellar age, the Sun is in full bloom. It has existed for about 4.5 billion years. For stars, this is just the age of maturity. Gradually, the luminary will begin to warm up and give more and more heat to the surrounding space. In about a billion years, the Sun will become 10% warmer, which is enough to almost completely destroy life on Earth. The sun will begin to expand rapidly, while its temperature is enough for hydrogen to start burning in the outer shell. The star will turn into a red giant. At about 12.5 billion years old, the Sun will begin to rapidly lose mass - substances from the outer shell will be carried away by the solar wind. The star will shrink again, and then briefly turn back into a red giant again. By the standards of the Universe, this phase will not last long - tens of millions of years. Then the Sun will again throw off the outer layers. They will become a planetary nebula, in the middle of which will be a slowly fading and cooling white dwarf.
13. Due to the very high temperature in the Sun's atmosphere (it is millions of degrees and is comparable to the temperature of the core), spacecraft cannot explore the star from close range. In the mid-1970s, German astronomers launched the Helios satellites in the direction of the Sun. Their almost sole purpose was to get as close to the sun as possible. Communication with the first spacecraft ended at a distance of 47 million kilometers from the Sun. "Helios B" climbed further, approaching the star at 44 million kilometers. Such expensive experiments were never repeated. Interestingly, in order to launch a spacecraft into an optimal near-solar orbit, it must be sent through Jupiter, which is five times farther from the Earth than to the Sun. There, the device performs a special maneuver, and is sent to the Sun, using Jupiter's gravity.
14. Since 1994, on the initiative of the European Chapter of the International Society of Solar Energy, Sun Day is celebrated annually on May 3 On this day, events promoting the use of solar energy are held: excursions to solar power plants, children's drawing contests, solar-powered car runs, seminars and conferences. And in the DPRK, Sun Day is one of the largest national holidays. True, he has nothing to do with our luminary. It is the birthday of the DPRK founder Kim Il Sung. It is celebrated on April 19.
15. In a hypothetical case, if the Sun goes out and stops emitting heat (but remains in its place), an instant catastrophe will not happen. The photosynthesis of plants will stop, but only the smallest representatives of the flora will quickly die, and the trees will live for several more months. The most serious negative factor will be a drop in temperature. Within a few days, it will drop immediately to -17 ° С, while now the average annual temperature on Earth is + 14.2 ° С. The changes in nature will be colossal, but some people will have time to escape. In Iceland, for example, more than 80% of energy is obtained from sources heated by volcanic heat, and they will not go anywhere. Some will be able to take refuge in underground shelters. On the whole, all this will be a slow extinction of the planet.
