The color of the sky different states The weather varies, varying from whitish to intense blue. A theory explaining the color of the sky was developed by Rayleigh.
According to this theory, the color of the sky is explained by the fact that the rays of the sun, repeatedly reflected from air molecules and tiny particles of dust, are scattered in the atmosphere. Light waves of different lengths are scattered differently by molecules: air molecules scatter predominantly the short-wavelength part of the visible solar spectrum, i.e. blue, indigo and violet rays, and since the intensity of the violet part of the spectrum is low compared to the blue and blue parts, the sky appears blue or blue.
The significant brightness of the sky is explained by the fact that the earth's atmosphere has a significant thickness and light is scattered by a huge number of molecules.
At high altitudes, for example, when observing from spaceships, rarefied layers of the atmosphere remain above the observer's head with fewer molecules scattering light, and therefore the brightness of the sky decreases. The sky seems darker, its color changes with increasing altitude. The sky appears darker, its color changing from dark blue to dark purple with increasing altitude. Obviously, at even higher altitudes and outside the atmosphere, the sky appears black to the observer.
If the air contains a large number of relatively large particles, then these particles will also disperse longer ones. light waves. In this case, the sky takes on a whitish color. Large water drops, or water crystals, that make up clouds, scatter all spectral colors approximately equally, and the cloudy sky therefore has a pale grey colour.
This is confirmed by observations, during which meteorological conditions and the corresponding color of the sky over the city of Novokuznetsk were noted.
The characteristic shades in the color of the sky on November 28-29 are due to the presence industrial emissions, which concentrate in the air with a decrease in temperature and lack of wind.
The color of the sky is also influenced by the character and color earth's surface, as well as atmospheric density.
Exponential law of decreasing atmospheric density with height.
The barometric formula describes the decrease in atmospheric density with altitude general outline; it does not take into account wind, convection currents, or temperature changes. In addition, the height should not be too high so that the dependence of the acceleration g on height can be neglected.
The barometric formula is associated with the name of the Austrian physicist Ludwig Boltzmann. But the first indications of the exponential nature of the decrease in air density with height were actually contained in Newton’s studies on the refraction of light in the atmosphere and were used in the compilation of an updated refraction table.
The graphs given show how, in the process of studying astronomical refraction, ideas about general character changes in the refractive index of the atmosphere with altitude.
- corresponds to Kepler's theory
- Newton's original theory of refraction
- refined Newtonian and modern theory refraction of light in the atmosphere
Refraction of light in the atmosphere
The atmosphere is an optically inhomogeneous medium, so the trajectory light beam in the atmosphere is always curvilinear to some extent. The bending of light rays as they pass through the atmosphere is called refraction of light in the atmosphere.
There are astronomical and terrestrial refraction. In the first case, the curvature of light rays coming to an earthly observer from celestial bodies. In the second case, the curvature of light rays coming to the observer from earthly objects is considered. In both cases, due to the bending of light rays, the observer may see the object in a direction that is not the one that corresponds to reality; the object may appear distorted. It is possible to observe an object even when it is actually behind the horizon. Thus, the refraction of light in the earth's atmosphere can lead to peculiar optical illusions.
Let us assume that the atmosphere consists of a set of optically homogeneous horizontal layers of equal thickness; the refractive index changes abruptly from one layer to another, gradually increasing in the direction from upper layers to the lower ones. This purely speculative situation is shown.
In reality, the density of the atmosphere, and therefore its refractive index, changes with height not in jumps, but continuously. Therefore, the trajectory of a light beam is not a broken line, but a curved line.
Let us assume that the ray shown in the figure passes to the observer from some celestial object. If there were no refraction of light in the atmosphere, then this object would be visible to the observer at an angle ά. Due to refraction, the observer sees the object not at an angle ά, but at an angle φ. Since φ ά, the object appears to be higher above the horizon than it actually is. In other words, the observed zenith distance of an object is less than the actual zenith distance. The difference Ώ = ά – φ is called the refraction angle.
According to modern data, the maximum refraction angle is 35".
When an observer watches the sunset and sees how the lower edge of the luminary touched the horizon, in reality this moment this edge is already 35" below the horizon line. It is interesting that the upper edge of the solar disk is raised less by refraction - only 29". Therefore, the setting Sun appears slightly flattened vertically.
Amazing sunsets
When considering the refraction of light, it is necessary to take into account, along with the systematic change in air density with height, also a series additional factors, many of which are quite random in nature. We are talking about the influence on the refractive index of air of convection currents and wind, air temperature at different points in the atmosphere above different areas earth's surface.
Features of the state of the atmosphere and, above all, features of the heating of the atmosphere in its lower layers over various parts of the earth's surface lead to the uniqueness of the observed sunsets.
Blind lane. Sometimes the Sun seems to set not behind the horizon, but behind some invisible line located above the horizon. This phenomenon is observed in the absence of any clouds on the horizon. If you climb to the top of the hill at this time, you can observe an even stranger picture: now the Sun sets below the horizon, but at the same time solar disk turns out to be cut, as it were, by a horizontal “blind stripe”, the position of which in relation to the horizon line remains unchanged. These unusual sunsets can be seen, according to eyewitnesses, in different geographical areas, for example, in the village of Bolshoy Kamen, Primorsky Territory and the city of Sochi, Krasnodar Territory.
This picture is observed if the air near the Earth itself turns out to be cold, and above there is a layer of relatively warm air. In this case, the refractive index of air changes with height approximately as shown in the graph; the transition from the lower cold layer of air to the warm one lying above it can lead to a rather sharp drop in the refractive index. For simplicity, we assume that this decline occurs abruptly and that therefore there is a clearly defined interface between the cold and warm layers, located at a certain height h1 above the Earth’s surface. In the figure, nx denotes the refractive index of air in the cold layer, and nt – in the warm layer near the border with the cold one.
The refractive index of air differs very little from unity, therefore, for greater clarity, vertical axis This figure shows the values not of the refractive index itself, but of its excess over unity, i.e. difference n-1.
The picture of the change in the refractive index presented in Fig. 4b) was used to construct the ray path in Fig. 5, which shows part of the surface globe and an adjacent layer of cold air of thickness hο.
If you gradually increase φ, starting from zero, the angle α2 will also increase. Let us assume that at a certain value φ = φ´ the angle α2 becomes equal limit angleαο , corresponding to the complete internal reflection at the border of cold and warm layers; in this case sin α1 = 1. Angle αο corresponds to beam BA in Figure 5; it forms an angle β = 90˚ - φ´ with the horizontal. The observer will not receive rays that enter the cold layer at points whose angular height above the horizon is less than the angular height of point B, i.e. less than angle β. This explains the blind spot.
Green ray. A green beam is a very effective flash. green light, sometimes observed at sunset and sunrise. The flash duration is only 1-2 seconds. The phenomenon is as follows: if the Sun sets at clear sky, then with sufficient transparency of the air, you can sometimes observe how the last visible point of the Sun quickly changes its color from pale yellow or orange-red to bright green. At sunrise the same phenomenon can be observed, but with in reverse order alternating colors.
Emergence green beam can be explained by taking into account the change in refractive index with light frequency.
Typically, the refractive index increases with increasing frequency. Rays with a higher refractive frequency are stronger. This means that blue-green rays undergo stronger refraction compared to red rays.
Let us assume that there is refraction of light in the atmosphere, but no scattering of light. In this case, the upper and bottom edge the solar disk near the horizon should be colored in the colors of the rainbow. Let in the spectrum sunlight there are only two colors - green and red; The "white" solar disk can be viewed in in this case in the form of green and red disks superimposed on each other. The refraction of light in the atmosphere raises the green disk above the horizon in to a greater extent than red. Therefore, the observer would have to see the setting Sun as it is shown in Fig. 6a) . The upper edge of the solar disk would be green and the lower edge red; in the central part of the disk a mixture of colors would be observed, i.e. a white color would be observed.
In reality, one cannot ignore the scattering of light in the atmosphere. It leads to the fact that rays with a higher frequency are eliminated more efficiently from the light beam coming from the Sun. So the green border on top of the disk will not be visible, and the entire disk will look reddish rather than white. If, however, almost the entire solar disk has gone beyond the horizon, only its very upper edge remains, and the weather is clear and calm, the air is clean, then in this case the observer can see the bright green edge of the Sun along with a scattering of bright green rays
Municipal budget educational institution
"Kislovskaya secondary school" Tomsk district
Research
Topic: “Why is the sunset red...”
(Light dispersion)
Work completed: ,
student of class 5A
Supervisor;
chemistry teacher
1. Introduction …………………………………………………………… 3
2. Main part………………………………………………………4
3. What is light……………………………………………………….. 4
Subject of study– sunset and sky.
Research hypotheses:
The sun has rays that color the sky in different colors;
Red color can be obtained in laboratory conditions.
The relevance of my topic lies in the fact that it will be interesting and useful for listeners because many people look at the clear blue sky, admire it, and few know why it is so blue during the day, and red at sunset, and what gives it such a color.
2. Main part
At first glance, this question seems simple, but in fact it affects deep aspects of the refraction of light in the atmosphere. Before you can understand the answer to this question, you need to have an idea of what light is..jpg" align="left" height="1 src=">
What is light?
Sunlight is energy. The heat of the sun's rays, focused by the lens, turns into fire. Light and heat are reflected by white surfaces and absorbed by black ones. That's why white clothes colder than black.
What is the nature of light? The first person to seriously attempt to study light was Isaac Newton. He believed that light consists of corpuscular particles that are fired like bullets. But some characteristics of light could not be explained by this theory.
Another scientist, Huygens, proposed a different explanation for the nature of light. He developed the "wave" theory of light. He believed that light formed pulses, or waves, in the same way that a stone thrown into a pond creates waves.
What views do scientists today hold on the origin of light? It is currently believed that light waves have characteristics both particles and waves at the same time. Experiments are being conducted to confirm both theories.
Light consists of photons - weightless particles with no mass, traveling at a speed of about 300,000 km/s and having wave properties. Frequency wave oscillations light determines its color. In addition, the higher the oscillation frequency, the shorter the wavelength. Each color has its own vibration frequency and wavelength. White sunlight is made up of many colors that can be seen when it is refracted through a glass prism.
1. A prism decomposes light.
2. White light is complex.
If you look closely at the passage of light through triangular prism, then you can see that the decomposition of white light begins as soon as the light passes from the air into the glass. Instead of glass, you can use other materials that are transparent to light.
It is remarkable that this experiment has survived centuries, and its methodology is still used in laboratories without significant changes.
dispersio (lat.) – scattering, dispersion - dispersion
I. Newton's experiments on dispersion.
I. Newton was the first to study the phenomenon of light dispersion and is considered one of his most important scientific merits. No wonder on his tombstone, erected in 1731 and decorated with figures of young men who hold his emblems in their hands major discoveries, one figure holds a prism, and the inscription on the monument contains the words: “He investigated the difference in light rays and the various properties that appeared at the same time, which no one had previously suspected.” The last statement is not entirely accurate. Dispersion was known earlier, but it was not studied in detail. While improving telescopes, Newton noticed that the image produced by the lens was colored at the edges. By examining edges colored by refraction, Newton made his discoveries in the field of optics.
Visible spectrum
When the beam is decomposed white a spectrum is formed in the prism in which radiation of different wavelengths is refracted under different angles. Colors included in the spectrum, that is, those colors that can be produced by light waves of one wavelength (or a very narrow range), are called spectral colors. Primary spectral colors (having proper name), as well as the emission characteristics of these colors, are presented in the table:
Each “color” in the spectrum must be matched with a light wave of a certain length
The simplest idea of the spectrum can be obtained by looking at a rainbow. White light, refracted in water droplets, forms a rainbow, since it consists of many rays of all colors, and they are refracted differently: red ones are the weakest, blue and violet are the strongest. Astronomers study the spectra of the Sun, stars, planets, and comets, since a lot can be learned from the spectra.
Nitrogen" href="/text/category/azot/" rel="bookmark">nitrogen. Red and blue light interact differently with oxygen. Since the wavelength of blue roughly corresponds to the size of an oxygen atom and because of this blue light is scattered by oxygen in different sides, while red light calmly passes through the atmospheric layer. In fact, even more disperses into the atmosphere purple light, however, the human eye is less sensitive to it than to blue light. The result is that the human eye catches blue light scattered by oxygen from all sides, which is why the sky appears blue to us.
Without an atmosphere on Earth, the Sun would appear to us as a bright white star and the sky would be black.
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Unusual phenomena
https://pandia.ru/text/80/039/images/image008_21.jpg" alt=" Polar Lights" align="left" width="140" height="217 src="> Auroras Since ancient times, people have admired the majestic picture of the auroras and wondered about their origin. One of the earliest mentions of auroras is found in Aristotle. In his “Meteorology”, written 2300 years ago, you can read: “Sometimes on clear nights many phenomena are observed in the sky - gaps, gaps, blood-red color...
It looks like there's a fire burning."
Why does a clear beam ripple at night?
What thin flame spreads into the firmament?
Like lightning without threatening clouds
Striving from the ground to the zenith?
How can it be that a frozen ball
Was there a fire in the middle of winter?
What is the aurora? How is it formed?
Answer. Aurora is a luminescent glow resulting from the interaction of charged particles (electrons and protons) flying from the Sun with atoms and molecules earth's atmosphere. The appearance of these charged particles in certain areas of the atmosphere and at certain altitudes is the result of interaction solar wind With magnetic field Earth.
Aerosol" href="/text/category/ayerozolmz/" rel="bookmark">aerosol dispersion of dust and moisture, these are the main cause of decomposition sunny color(variance). At the zenith position, the incidence of the sun's ray on the aerosol components of the air occurs almost at a right angle, their layer between the observer's eyes and the sun is insignificant. The lower the sun descends to the horizon, the more the layer thickness increases atmospheric air and the amount of aerosol suspension in it. The sun's rays, relative to the observer, change the angle of incidence on suspended particles, and then dispersion of sunlight is observed. So, as mentioned above, sunlight is made up of seven primary colors. Every color is like electromagnetic wave, has its own length and ability to disperse in the atmosphere. The primary colors of the spectrum are arranged in order on a scale, from red to violet. Least ability The color red is susceptible to scattering (and therefore absorption) in the atmosphere. With the phenomenon of dispersion, all colors that follow red on the scale are scattered by the components of the aerosol suspension and absorbed by them. The observer sees only red color. This means that the thicker the layer of atmospheric air, the higher the density of the suspended matter, the more rays of the spectrum will be scattered and absorbed. Famous a natural phenomenon: after the powerful eruption of the Krakatoa volcano in 1883, in different places planet, for several years, unusually bright, red sunsets were observed. This is explained by the powerful release of volcanic dust into the atmosphere during the eruption.
I think that my research will not end here. I still have questions. I want to know:
What happens when light rays pass through various liquids and solutions;
How light is reflected and absorbed.
Having completed this work, I became convinced of how many amazing and useful things there are for practical activities may involve the phenomenon of light refraction. It was this that allowed me to understand why the sunset is red.
Literature
1. , Physics. Chemistry. 5-6 grades Textbook. M.: Bustard, 2009, p.106
2. Damask steel phenomena in nature. M.: Education, 1974, 143 p.
3. “Who makes the rainbow?” – Kvant 1988, No. 6, p. 46.
4. Newton I. Lectures on optics. Tarasov in nature. – M.: Education, 1988
Internet resources:
1. http://potomy. ru/ Why is the sky blue?
2. http://www. voprosy-kak-i-pochemu. ru Why is the sky blue?
3. http://expirience. ru/category/education/
We are all accustomed to the fact that the color of the sky is a variable characteristic. Fog, clouds, time of day - everything affects the color of the dome overhead. Its daily shift does not occupy the minds of most adults, which cannot be said about children. They are constantly wondering why the sky is physically blue or what makes a sunset red. Let's try to understand these not so simple questions.
Changeable
It’s worth starting by answering the question of what the sky actually represents. IN ancient world it was truly seen as a dome covering the Earth. Today, however, hardly anyone does not know that, no matter how high the curious explorer rises, he will not be able to reach this dome. The sky is not a thing, but rather a panorama that opens up when viewed from the surface of the planet, a kind of appearance woven from light. Moreover, if you observe from different points, it may look different. So, from rising above the clouds, a completely different view opens up than from the ground at this time.
A clear sky is blue, but as soon as clouds come in, it becomes gray, leaden or dirty white. The night sky is black, sometimes you can see reddish areas on it. This is the reflection of the artificial lighting of the city. The reason for all such changes is light and its interaction with air and particles. various substances in him.
The nature of color
In order to answer the question of why the sky is blue from a physics point of view, we need to remember what color is. This is a wave of a certain length. Light coming from the Sun to the Earth is seen as white. It has been known since Newton's experiments that it is a beam of seven rays: red, orange, yellow, green, blue, indigo and violet. Colors differ in wavelength. The red-orange spectrum includes waves that are the most impressive in this parameter. parts of the spectrum are characterized by short wavelengths. The decomposition of light into a spectrum occurs when it collides with molecules of various substances, and some of the waves can be absorbed, and some can be scattered.
Investigation of the cause
Many scientists have tried to explain why the sky is blue in terms of physics. All researchers sought to discover a phenomenon or process that scatters light in the planet's atmosphere in such a way that, as a result, only blue light reaches us. The first candidates for the role of such particles were water. It was believed that they absorb red light and transmit blue light, and as a result we see a blue sky. Subsequent calculations, however, showed that the amount of ozone, ice crystals and water vapor molecules in the atmosphere is not enough to give the sky a blue color.
The reason is pollution
On next stage Research by John Tyndall suggested that dust plays the role of the desired particles. Blue light has the greatest resistance to scattering, and therefore is able to pass through all layers of dust and other suspended particles. Tindall conducted an experiment that confirmed his assumption. He created a smog model in the laboratory and illuminated it with bright white light. The smog took on a blue tint. The scientist made an unambiguous conclusion from his research: the color of the sky is determined by dust particles, that is, if the Earth’s air was clean, then the skies above people’s heads would glow not blue, but white.
Lord's Research
The final point on the question of why the sky is blue (from the point of view of physics) was put by the English scientist, Lord D. Rayleigh. He proved that it is not dust or smog that colors the space above our heads in the shade we are familiar with. It's in the air itself. Gas molecules absorb most and primarily the longest wavelengths, equivalent to red. The blue dissipates. This is precisely how today we explain the color of the sky we see in clear weather.
Those attentive will notice that, following the logic of scientists, the dome overhead should be purple, since this color has the shortest wavelength in the visible range. However, this is not a mistake: the proportion of violet in the spectrum is much smaller than blue, and human eyes are more sensitive to the latter. In fact, the blue we see is the result of mixing blue with violet and some other colors.
Sunsets and clouds
Everyone knows that in different time days you can see different colour sky. Photos of beautiful sunsets over the sea or lake are a perfect illustration of this. All kinds of shades of red and yellow combined with blue and dark blue make such a spectacle unforgettable. And it is explained by the same scattering of light. The fact is that during sunset and dawn, the sun's rays have to travel a much longer path through the atmosphere than at the height of the day. In this case, the light from the blue-green part of the spectrum is scattered in different directions and clouds located near the horizon become colored in shades of red.
When the sky becomes clouded, the picture changes completely. unable to overcome the dense layer, and most of they simply do not reach the ground. The rays that managed to pass through the clouds meet with water drops of rain and clouds, which again distort the light. As a result of all these transformations, white light reaches the earth if the clouds are small in size, and gray light when the sky is covered by impressive clouds that absorb part of the rays for the second time.
Other skies
It's interesting that on other planets solar system When viewed from the surface, one can see a sky very different from that on earth. On space objects deprived of the atmosphere, the sun's rays freely reach the surface. As a result, the sky here is black, without any shade. This picture can be seen on the Moon, Mercury and Pluto.
The Martian sky has a red-orange hue. The reason for this lies in the dust that fills the planet’s atmosphere. She is painted in different shades red and orange. When the Sun rises above the horizon, the Martian sky turns pinkish-red, while the area immediately surrounding the disk of the luminary appears blue or even violet.
The sky above Saturn is the same color as on Earth. Aquamarine skies stretch over Uranus. The reason lies in the methane haze located in the upper planets.
Venus is hidden from the eyes of researchers by a dense layer of clouds. It does not allow rays of the blue-green spectrum to reach the surface of the planet, so the sky here is yellow-orange with a gray stripe along the horizon.
Exploring the space overhead during the day reveals no less wonders than studying the starry sky. Understanding the processes occurring in the clouds and behind them helps to understand the reason for things that are quite familiar to the average person, which, however, not everyone can explain right away.
Why the sky is blue? It is difficult to find an answer to such a simple question. Many scientists racked their brains in search of an answer. The best solution problems proposed about 100 years ago English physicist Lord John Rayleigh.
The sun emits dazzlingly pure white light. This means that the color of the sky should be the same, but it is still blue. What happens to white light in the earth's atmosphere?
White light is a mixture of colored rays. Using a prism we can make a rainbow.
The prism splits the white beam into colored stripes:
■Red
■Orange
■ Yellow
■ Green
■ Blue
■ Blue
■ Purple
Combining together, these rays again form white light. It can be assumed that sunlight is first split into colored components. Then something happens, and only blue rays reach the surface of the Earth.
So why is the sky blue?
There are several possible explanations. The air surrounding the Earth is a mixture of gases: nitrogen, oxygen, argon and others. There is also water vapor and ice crystals in the atmosphere. Dust and other particles are suspended in the air fine particles. In the upper layers of the atmosphere there is a layer of ozone. Could this be the reason? Some scientists believed that ozone and water molecules absorb red rays and transmit blue ones. But it turned out that there was simply not enough ozone and water in the atmosphere to color the sky blue.
In 1869, an Englishman John Tindall suggested that dust and other particles scatter light. Blue light scatters into least degree and passes through layers of such particles, reaching the surface of the Earth. In his laboratory, he created a model of smog and illuminated it with a bright white beam. The smog turned a deep blue. Tindall decided that if the air were absolutely clear, then nothing would scatter the light, and we could admire the bright white sky. Lord Rayleigh also supported this idea, but not for long. In 1899 he published his explanation:
It is air, not dust or smoke, that colors the sky blue.
The main theory about the blue color of the sky
Some of the sun's rays pass between gas molecules without colliding with them and reach the Earth's surface unchanged. The other, larger part is absorbed by gas molecules. When photons are absorbed, molecules become excited, that is, they are charged with energy, and then emit it in the form of photons. These secondary photons have different lengths waves and can be any color - from red to purple. They scatter in all directions: towards the Earth, and towards the Sun, and to the sides. Lord Rayleigh suggested that the color of the emitted beam depends on the predominance of quanta of one color or another in the beam. When a gas molecule collides with photons of solar rays, there are eight blue quanta per secondary red quantum.
What is the result? Intense blue light literally pours down on us from all directions from billions of gas molecules in the atmosphere. This light has photons of other colors mixed in, so it is not purely blue.
Why then is the sunset red?
However, the sky is not always blue. The question naturally arises: if we see throughout the day blue sky why is the sunset red? Red color is the least scattered by gas molecules. During sunset, the Sun approaches the horizon and Sunbeam directed towards the surface of the Earth not vertically, as during the day, but at an angle.
Therefore, the path it takes through the atmosphere is much Furthermore that it takes place during the day when the Sun is high. Because of this, the blue-blue spectrum is absorbed in a thick layer of the atmosphere, not reaching the Earth. And longer light waves of the red-yellow spectrum reach the surface of the Earth, coloring the sky and clouds in the red and yellow colors characteristic of sunset.
Scientific explanation
Above we gave the answer comparatively in simple language. Below we quote the rationale using scientific terms and formulas.
Excerpt from Wiki:
The reason the sky appears blue is because the air scatters short-wavelength light more than long-wavelength light. The intensity of Rayleigh scattering, caused by fluctuations in the number of molecules of air gases in volumes commensurate with the wavelengths of light, is proportional to 1/λ 4, λ is the wavelength, i.e., the violet region visible spectrum scatters approximately 16 times more intensely than red. Because blue light has a shorter wavelength, at the end of the visible spectrum, it is scattered more into the atmosphere than red light. Due to this, the part of the sky outside the direction of the Sun has a blue color (but not violet, since solar spectrum uneven and the intensity of the violet color in it is less, and also due to the less sensitivity of the eye to purple color and more to blue, which irritates not only those sensitive to blue color cones in the retina, but also sensitive to red and green rays).
During sunset and dawn, light travels tangentially to the earth's surface, so that the path traveled by light in the atmosphere becomes much longer than during the day. Because of this, most of the blue and even green light is scattered from direct sunlight, so the direct light of the sun, as well as the clouds it illuminates and the sky near the horizon, are colored red.
Probably, with a different composition of the atmosphere, for example, on other planets, the color of the sky, including at sunset, may be different. For example, the color of the sky on Mars is reddish pink.
Scattering and absorption are the main reasons for the weakening of light intensity in the atmosphere. Scattering varies as a function of the ratio of the diameter of the scattering particle to the wavelength of the light. When this ratio is less than 1/10, Rayleigh scattering occurs, in which the scattering coefficient is proportional to 1/λ 4 . At larger values of the ratio of the size of the scattering particles to the wavelength, the scattering law changes according to the Gustave Mie Equation; when this ratio is greater than 10, the laws of geometric optics are applied with sufficient accuracy for practice.
The beauty of the sky has been depicted more than once by artists, described by writers and poets, even people who are very far from art stare into this alluring abyss, admire it, finding neither words nor sufficient emotions to express those feelings that stir the soul and mind. The heights attract a person in any role, it is beautiful with its crystal blue surface, no less attractive are its seething streams of white-gray clouds, replaced by light inclusions of cirrus clouds or lush cumulus “lambs”. And no matter how melancholy the cloudy sky may look, enveloping with its depth, deafening and pressing with its entire mass, it also causes a storm of emotions and experiences, bringing thoughts to a special wave.
Beauty is seen by the beholder
Each person perceives the world differently. For some, it is gloomy and gray, while others, on the contrary, see only a blooming, green planet full of colors. We also evaluate the heavens above our heads differently. If we take into account a person with ordinary color perception, then he will see the sky as it is commonly considered - blue, gray, pinkish at sunset, smoky-gray at dawn.
In fact, these colors are only what our eyes and brain are able to convey to us. It is easiest for human eyes to perceive a cloudy sky as gray. In clear weather, we have endless azure overhead, but in reality the atmospheric dome is closer violet shade, if you look at it from the Earth.
In this publication, we will find out why the sky is gray on a cloudy day and what determines the saturation of this color; we will also find out how its color changes throughout the day and year and what affects these processes.
Bottomless ocean above
Above the territory European countries The sky in the warm season usually amazes with its richness. Sometimes you can say about it that it is blue-blue. However, if we devote at least one day to what is happening above our heads and carefully observe natural processes, then you can notice a gradation of color, which changes very much from the moment the sun rises until the moment it completely sets.
In summer, the sky seems so clear and visually high due to low humidity, lack of large quantity clouds that, accumulating water, gradually descend closer to the ground. In clear weather, our gaze does not even look hundreds of meters ahead, but at a distance of 1-1.5 km. That is why we perceive the sky as high and bright - the absence of interference in the path of light rays in the atmosphere ensures that they do not refract, and the eyes perceive its color as blue.
Why does the sky change color
This change is described by science, although not as picturesquely as by writers, and is called diffuse radiation of the sky. Speaking in simple and accessible language for the reader, the processes of color formation in the skies can be explained as follows. The light that the sun emits passes through the air layer around the Earth, which scatters it. This process occurs more simply with short-length waves. During maximum rise heavenly body above our planet, at a point located outside its direction, the brightest and most saturated blue color will be observed.
However, when the sun sets or rises, its rays travel tangentially to the surface of the Earth, the light emitted by them needs to travel more long haul, which means they disperse in the air to a much greater extent than during the day. As a result, a person perceives the sky in pink and red colors in the morning and evening. This phenomenon is most visible when there is a cloudy sky above us. Clouds and clouds then become very bright, the glow of the setting sun colors them in stunning
Stormsteel
But what is a cloudy sky? Why does it become like this? This phenomenon is one of the links in the water cycle of nature. Rising upward in the form of steam, water particles enter the atmospheric layer with a lower temperature. Accumulating and cooling on high altitude, they connect with each other, turning into drops. At that moment when these particles are still very small, beautiful white cumulus clouds appear to our eyes. However, the larger the drops become, the more gray there is in the clouds.
Sometimes, looking at the sky through which these huge “lambs” float, you can see that one part of them is painted gray, while others even take on a steel, thunderous hue. This transformation is explained by the fact that drops in clouds have different sizes and shape, which is why they refract light differently. When the sky is completely cloudy, it is entirely painted in mousy gray tones, only white light reaches us.
Vast smoky expanses
There are days when the gray cloudy sky does not have a single clearing. This happens when the concentration of clouds and clouds is very high, they envelop the entire visual space above. Sometimes they are perceived as a huge pressing mass, ready to collapse on your head. Moreover, this phenomenon is most characteristically demonstrated in autumn and winter, when the air temperature is low, but the humidity, on the contrary, is high and is at the level of 80-90%.
On such days, the clouds are very close to the earth's surface; they are located only a hundred or two meters from it. The description of a cloudy sky often has melancholic and depressive notes, and this is most likely connected precisely with those sensations that arise when you feel alone with this gloomy colossus, ready to fall on you with rain and cold.
But everything could have been different...
What tones the sky plays depends on the intensity light radiation and wavelengths reaching the planet, so in winter even in clear days it is gray-blue. But the closer spring is and the higher the sun is, the brighter its blue, especially on days when the haze in the upper atmosphere, which distorts the light, dissipates.
Scientists have found that on other planets the sky may not have the blue and blue colors we are accustomed to. gray colors, on Mars, for example, it is pink even at the height of daylight.