Juan Carlos Beamin

“ Almost every change occurring in the sky was perceived as problematics or bad omens, especially in the case of wonders involving the Moon and the Sun, mainly the eclipses.
There are stories and myths about eclipses in almost every culture and in the five continents. Through these narratives, we can notice both cultural and social differences. However, before questioning such beliefs, let’s remember what the Sun and the Moon represent. The Sun gives us its energy and heat and, therefore, is essential in every aspect of life. ”

“ Out of the eight planets that the Solar System has, in the third one closest to the Sun, life developed. In the beginning, 3 billion years ago, there were only bacteria, but this was increasing in time and diversifying. And today, as human beings, we can do research and understand how did we get here and amaze at everything that exists. ”

“ THE SUN
THE BRIGHTNESS OF STARS
The Sun is the nearest star to us, and its luminosity makes it special from the rest. We can see its intense brightness since it is “very close” to us, merely to 150 million kilometers away, whereas the next closest star is no less than 39,762,576,000,000 kilometers away (39 trillion kilometers) . Two thousand times farther!
Most of the stars in the Universe are, in fact, smaller and brighter than our Sun. Nevertheless, it is surprising that most of the ones we can see at night are actually, larger, hotter, and brighter. ”

“ To turn on a light, a telephone or a computer, to move a car, to warm ourselves in winter and refresh in summer, to walk, or even read these lines, we need energy. So, where does this energy come from? There are different sources. We can burn some fuel to warm up or move, or take advantage of the wind or the falling water on a waterfall to turn it into kinetic energy useful for other purposes. We can also take the solar light and turn it into chemical energy, keep it within batteries, and then use them to run our electronic devices. ”

“ Even plants can transform solar light, air, water, and minerals into sugars to generate energy through other chemical processes, but how is the energy that comes from the Sun produced?
The Sun is mainly made up of hydrogen and helium, the most lightweight and common elements in the whole Universe, besides small quantities of chemical components such as carbon, nitrogen, oxygen, iron, sodium, calcium, and magnesium, among others.
In contrast to the Earth conditions, the Sun possess an enormous gravity due to its gigantic mass, which makes its core particularly hot. ”

“ In the case of the Earth with the Sun, it doesn’t happen because the Earth rotates 365.25 times per orbit.
The fact that we always see the same face of the Moon made us jump into the conclusion that it has a dark side. There is indeed a side we can’t see from Earth, but that doesn’t mean that it doesn’t get any light and it is always dark because of the Sun lights up every inch of the Moon in different moments of the lunar phase. For instance, during the New Moon phase, the Sun is entirely lightning up the side that we can’t see. ”

“ Fortunately, the light produced at the center of the stars pass through their atmosphere and approach us, acting just like the light we produce on Earth. Also, their atoms behave the same way in the star as in the laboratory, which means that first, we study the kind of light atoms produce on Earth, and the colors they emit, and also how bright is every color.
For instance, if the gas of an element is heated, the brightness of its color is always the same. So, thanks to the laws of quantum physics, we can precisely calculate how much energy that brightness means. ”

“ Some of the properties that make water an essential element for life development on Earth are: it is an excellent solvent, it provides suitable conditions to many chemical reactions, and it allows the transfer of substances between cells and their environment. Also, the heat capacity of water -that is the amount of energy required to increase one Celsius degree- is very high, which means that in comparison with other elements such as rocks or metal, water takes more time to heat, remaining the surface temperature of the planet stable with slight variations between day and night. ”

“ After two hundred million years, the first galaxies showed up, and from then on, a new transformation began: the large amount of light that stars produce makes electrons split up inside hydrogen atoms, so the Universe is ionized again (as in the beginning) , and that’s how it is up to date.
Going forward in time, the Universe continues to expand; new galaxies and stars are formed, some of them explode as supernovae and inject some other materials into the Universe; galaxies merge with each other, grow, and trigger the formation of new stars. ”

“ On the one hand, this enormous distance is something great because if the Earth were closer, the amount of light and energy that it would receive would be much higher. Therefore, the temperature would increase, putting the development of life in danger. On the other hand, if we were further, it would be the opposite: the lack of energy and low temperatures would make the living existence on our planet difficult. ”

“ Actually, most of the planets have been found by this technique, either from telescopes on Earth or space ones.
The Kepler space telescope, which is currently on the TESS mission and, in the near future the PLATO mission, have been and will be responsible for discovering new planets, such as the Earth, orbiting other stars, and bringing humanity one step closer to the search for another possible Earth where life may exist because, despite the progress achieved, the most crucial question remains unanswered: Is there life beyond our planet? ”

“ In spite of these extreme examples, which seems to be so high or so deep for us, if we could compare Earth at a scale of a billiard ball, Earth would be much more even than the surface of a brand-new ball. ”

“ The Sun, however, doesn’t have a stellar neighbor, but only planets. The binary stars can have different separations or orbits, and these are oriented randomly in the sky. Since there are many stars in our Galaxy, some binary stars orbit a plane very aligned with the Earth, so then, in a particular region of its orbit, a star passes in front of the other, blocking the brightness of the one in the back. ”

“ So, by observing the edges of the Sun, we can see colder, outer layers, that’s why it looks slightly darker.
Something similar can be observed in the Earth’s atmosphere. The stars in the sky look clearer and static when we look up, whereas if we look to the horizon, they look blurred and blinking because the stars above cross fewer atmospheric layers to approach us.
Nearby the center of the star, a part of the light we observe is in the depths of it, where the temperature is higher, which means more light. ”

“ An eccentric orbit would cause us to get very close to the Sun in a short time, but in that period, life would experience significant changes: it would be fire everywhere and a lot of UV radiation which would kill bacteria, causing damage to the living creatures here on the Earth surface. The rest of the time, we would be far from the Sun, which would bring a brief ice age every year, and by the freeze of everything and the lack of both energy and light, it would be significantly hard to survive. ”

“ Even though, as human beings, we have lived on this planet for thousands of years, yet there are many things we don’t understand completely. For example, though the Earth is almost a perfect sphere, slightly flatten on its poles, we still have to discover why the south pole is a little bit bulkier than the north pole. ”

“ A thin layer of air surrounds the Earth that we denominate the atmosphere as a whole, which protects us from the Sun’s UV radiation and from particles such as cosmic rays, and it also provides us oxygen to breathe. ”

“ The energy that our planet lost by rotating so slow transferred to the Moon’s orbit and caused the Moon to move away, and consequently, to move slightly slower.
Today, our satellite moves away about four centimeters from us every year. Such is the case that in 100 years more, the day would last two thousandths of a second less, which means that in the not-too-distant future, the Moon is going to look smaller than we see it today, tides won’t change so much as they do currently, and the day is going to have more than 24 hours. ”

“ The inner part of the Earth is hard to explore. One may think that the best way to know what it is inside is to dig a hole and take samples, but that is not only difficult to do but also extremely expensive.
An alternative way to study the inner part of our planet is to see how does the energy transfer from the rocks. The Earth is very active in tectonic terms. Earthquakes and volcanic eruptions happen since the plates are periodically moving, and the energy that this movement produces travel across the rocks. ”

“ The ancient Greeks were right when they thought that the Moon phases could be explained through its relative motion around the Earth and that it is much closer than the Sun. The reason why we can see some brightness, even in those parts where the Sun can’t light directly, is because of the sunlight reflection on the Earth’s surface. ”

“ There is a force known as the tidal force, and it occurs since the gravity force gets weaker while things are separated by greater distances. This difference in the distance also makes a difference in the gravitational attraction among two points, making the closer region higher and the opposite region lower. That is the reason why the tidal force “faint” too fast, but is stronger when the distance between the involved bodies is short.
For instance, in the case of the Earth and the Moon, we say that its distance is, on average, 384,000 km. ”

“ This regolith may vary its thickness between 2 to 20 meters, so every time a mission land on the Moon, it leaves a record of that event. Even though the Moon is covered in this dust, most of its surface (under this layer) has basalt, a volcanic rock, or, in this case, from a lunar core rock that resurfaced after meteors impacts.
The Moon, unlike stars like the Sun, but like the planets, doesn’t emit light itself but reflects the light that comes from the Sun, which happens due to the lack of mass to produce energy in its core. ”

“ In this case, the energy is the one which transforms, and the mass is only a type of energy, such as light and heat. The famous formulae E=mc2, which reads “energy = mass times the speed of light squared,” precisely stands for this: if the mass of something is multiplied by the speed of light squared, it is obtained its rest energy. ”

“ A Moon eclipse is visible from anywhere on the terrestrial globe that is on the same side as the Moon, whereas a solar eclipse is only visible from a small part of the Earth since our planet is larger than the Moon, so that it can hide the sunlight from the whole surface. ”

“ Watch directly at the Sun is harmful to our sight. The brightness is so intense that our retina can be irreversibly damaged. So, if we want to watch the Sun directly, we must do it using the right implements. ”

“ The photosphere is the visible layer of the Sun. When we talk about the temperature of a star, we generally refer to the photosphere’s temperature, and the light of the mentioned layer is also useful to do chemical analysis of the stars. ”

“ We can see that if the Moon is at a minimum distance from the Earth, it doesn’t matter at what distance is the Earth from the Sun if the conditions form an eclipse are given, the total eclipse is seen. ”

“ Even today that we know the Moon is a great rock and the Sun a giant ball of plasma, some people decide not coming out of their houses and not watch the eclipse just for fear. Other urban myths state that eclipses are dangerous for pregnant women sitting outdoor during the eclipse, or it is even more dangerous to look at the Sun during the eclipse instead at any other time. ”

“ There are times when Venus or Mercury pass in front of the Sun, and we can see it with the right telescopes. They can’t eclipse the Sun entirely due to the considerable distance that separates the Earth from these two planets, blocking a small part of the sunlight, which are called transits. ”

“ Considering this, people who live eclipses offer prayers dedicated to the Sun through songs, asking if it can back to life to light up the world again and don’t leave them.
In general, myths and beliefs have something in common in different parts of the world: they cause fear due to the sudden change of the most visible celestial bodies, those which affects the most in our lives, but also there are very noticeable changes you can tell by the environment and the threating dangers. ”

“ The magnetic field is a force field. The Earth has a great magnetic field that seems to be related to the terrestrial core composition, a core of molten iron. This magnetic field acts like a protective shield, deflecting the high-speed particles coming from the Sun. ”

“ Although, in fact, the process is a little more complicated because as the Moon moves away from the Earth, the tides are slightly weaker, and, as a result, the Moon moves slower away, which would increase the time we have to keep observing total eclipses. However, in that timescale, the Sun would not be the same size, actually, it would grow a little bit, accelerating the effect that the Moon produces when moves away. As a consequence, the change of the Sun size would accelerate the process to leave us without total eclipses in about 500 million years more. ”

“ Then, looking from inside out is the mantle, a layer where most of the Earth’s mass is concentrated (about 67 %) and corresponds to 84 % of its total volume. In there, the most considerable part of both seismic and volcanic activity happens. In some cases, during the collision of plates, an element of the material in the upper mantle and the oceanic crust raise, allowing us to have access to rocks that belong to the mantle. These places, which are crucial to understanding the composition of the upper Earth’s mantle, are called ophiolites. ”

“ If both Sun and Moon’s sizes are known, can we know at which distance is each from the Earth?
2 · At what distance must be the Moon from the Earth for a total and an annular eclipse to occur? Does it depend on Earth-Sun distance?
Answers
The Earth is an elliptical (almost circular) orbit around the Sun, just like the Moon around the Earth. The maximum and minimum distances from the Earth to the Sun are 147 and 152 million kilometers, respectively, and the Sun has a diameter of 1,391,400 km. ”

“ Chile and Argentina are going to witness two total eclipses of the Sun during 2019 and 2020. In the maps below, you can see the exact point where this wonder will be visible. The red line traces the central and long-lasting path. The blue lines trace the bounds from where the total eclipse happens. Out of that region, you can only see a partial solar eclipse.
In the region of Coquimbo, the last total eclipse of the Sun was seen in 1893, 126 years ago, whereas La Araucanía has waited since 1467 to witness this phenomenon again. ”

“ In a distant future, we no longer can be witnesses of total solar eclipses since the Moon, even in its closest-to-the-Earth position, it won’t be able to block the Sun completely, and there will be only annular or partial eclipses. ”