Why are rain clouds dark? Why is the sky blue and the sunset red? Why is the sunset red
Despite scientific progress and free access to many sources of information, it is rare that a person can correctly answer the question of why the sky is blue.
Why is the sky blue or blue during the day?
White light - which is what the Sun emits - is made up of seven parts of the color spectrum: red, orange, yellow, green, blue, indigo and violet. The little rhyme that has been known since school - “Every Hunter Wants to Know Where the Pheasant Sits” - precisely determines the colors of this spectrum by the initial letters of each word. Each color has its own wavelength of light: red is the longest and violet is the shortest.
The sky (atmosphere) familiar to us consists of solid microparticles, tiny drops of water and gas molecules. For a long time, there have been several erroneous assumptions trying to explain why the sky is blue:
- the atmosphere, consisting of tiny particles of water and molecules of various gases, allows the rays of the blue spectrum to pass through well and does not allow the rays of the red spectrum to touch the Earth;
- Small solid particles - such as dust - suspended in the air scatter blue and violet wavelengths the least, and because of this they manage to reach the Earth's surface, unlike other colors of the spectrum.
These hypotheses were supported by many famous scientists, but research by the English physicist John Rayleigh showed that it is not solid particles that are the main cause of light scattering. It is the molecules of gases in the atmosphere that separate light into color components. A white ray of sunlight, colliding with a gas particle in the sky, scatters (scatters) in different directions.
When it collides with a gas molecule, each of the seven color components of white light is scattered. At the same time, light with longer waves (the red component of the spectrum, which also includes orange and yellow) is scattered less well than light with short waves (the blue component of the spectrum). Because of this, after scattering, eight times more blue spectrum colors remain in the air than red ones.
Although violet has the shortest wavelength, the sky still appears blue due to the mixture of violet and green waves. In addition, our eyes perceive blue color better than violet, given the same brightness of both. It is these facts that determine the color scheme of the sky: the atmosphere is literally filled with rays of blue-blue color.
Why then is the sunset red?
However, the sky is not always blue. The question naturally arises: if we see blue skies all day, why is the sunset red? We found out above that red color is least scattered by gas molecules. During sunset, the Sun approaches the horizon and the sun's ray is directed towards the Earth's surface not vertically, as during the day, but at an angle.
Therefore, the path it takes through the atmosphere is much longer than what it takes 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.
Why are the clouds white?
Let's touch on the topic of clouds. Why are there white clouds in the blue sky? First, let's remember how they are formed. Moist air containing invisible steam, heated at the surface of the earth, rises and expands due to the fact that the air pressure is less at the top. As the air expands, it cools. When water vapor reaches a certain temperature, it condenses around atmospheric dust and other suspended solids, resulting in tiny droplets of water that coalesce to form a cloud.
Despite their relatively small size, water particles are much larger than gas molecules. And if, when meeting air molecules, the sun's rays are scattered, then when they meet water droplets, the light is reflected from them. In this case, the initially white ray of sunlight does not change its color and at the same time “colors” the molecules of the clouds white.
It’s a great pleasure to watch the cumulus clouds passing by in the summer and try to explain why they are sometimes light and sometimes dark. When the cloud is illuminated by the Sun, it is dazzling white, but when the cloud passes above us, its base becomes gray or completely dark. The drops of water in the cloud are so closely located to each other that it appears as an almost completely opaque white body - white because light penetrates the cloud with difficulty, but is very well reflected by the numerous drops. If the Sun is covered by cumulus clouds, they appear dark, but the edges of the clouds are always light: "every cloud has a silver lining."
Thus the distribution of light and shadow gives us interesting information about the different parts of the cloud - upper, lower, front, back and about the actual shape of this huge formation. It is not always easy to get a correct idea of its proportions, as well as the position of the cloud in relation to the Sun. If, for example, the clouds are located in front of me, and the Sun is some distance above it, I will be puzzled to see only shadows (Fig. 169, a). I can't imagine the grandeur
Rice. 169. Light and shadows on cumulus clouds: a) how we see landscapes
observer, viewed from north to south; b) erroneous personal impressions of the observer and the picture he expects to see; c) how things are in reality. In cases b) and c) the observer looks from east to west. The sun is in the south.
distance to the Sun, I unconsciously consider it very close and therefore it seems to me that part AB should be illuminated (Fig. 169, 6). In fact, the sun's rays illuminating the cloud run parallel to the line connecting the Sun with my eye (Fig. 169, c).
No matter how capricious the play of light and shadow may be, no matter how complicated the matter may be by the shadows cast by one cloud on another, it seems impossible to explain by this alone all the differences in the colors of cumulus clouds.
I. Levitan
When the sky clears after a storm and there are only a few cumulus clouds left on it, brightly illuminated by the Sun and located so that the shadow of one of them cannot fall on another, these clouds become darker and darker and, finally, before completely disappearing , turn blue-black. The general impression is that the thin parts of cumulus clouds seen against a blue sky are not "blue+white" (as one might expect), but "blue+black".
On the other hand, a cumulus cloud appears gray when seen against the background of another large cloud that is completely white, so there cannot be any question of an increase in brightness simply due to an increase in the overall thickness of the layers. The physics of these phenomena, although observed daily, are still not well understood. Of course, we should be very careful about the idea that clouds actually absorb light; one must first try to explain the phenomenon by assuming that clouds are solid white formations, then remember that they are really nothing more than light-scattering fog, and finally consider that clouds may contain dark dust particles.
It is interesting to compare clouds with the white steam (not smoke!) of a steam locomotive. In some cases, the steam appears whiter when viewed at a greater angle to the incident light, and less bright when observed from the direction of the Sun, when the eye perceives rays reflected almost in the direction of incidence. In other cases, regardless of viewing direction, the vapor is much brighter than the brightest parts of the cumulus; This may be due to the greater distance to the clouds and the attenuation of light due to scattering in the air.
Georgy Nissky. Autumn. Semaphores
Dark cumulus clouds often appear bluish at great distances. This is not the color of the clouds themselves, but the light scattered in the atmosphere between the cloud and our eye. The further away such a dark cloud is, the closer its color approaches the color of the sky. On the other hand, bright clouds near the horizon become yellowish.
We should also consider other clouds and try to explain, for example, why rain clouds are so gray, why thunderclouds have a special lead color visible next to the faded orange. Isn’t this dust? Our information about all this, however, is so incomplete that we will limit ourselves to calling on the reader to make independent observations.
The distribution of brightness across the vault of heaven, when it is completely and evenly covered with clouds, is very characteristic and seems to complement the distribution in a clear sky. Compare, for example, using a mirror, the zenith and the horizon: with a clear sky, the zenith is always darker; The brightness ratio ranges from 3 to 5 (photos X1X and XX).
In the section on the question Why are clouds white and thunderclouds black? given by the author Natalya Natalya the best answer is that in ordinary clouds there are usually few water droplets; rather, there are not droplets, but very small particles. Sunlight is reflected from the outside of such particles. With such reflection, refraction does not occur; accordingly, the reflected light remains white. In thunderclouds (even in large dense clouds) there is much more water, which means more light is absorbed, but the likelihood that the light is reflected upwards from the ground also increases - so the clouds below appear dark... In clouds (clouds) there is nothing except water (in the form of steam or ice crystals), in fact this is the essence of the cloud/cloud. Clouds may also appear blacker due to the relatively low altitude of the “flight”, and the sun may shine more to the side than to the center above.
Reply from Pmmkemeuts[newbie]
because the rays of the sun do not pass through it
Reply from Leonid[guru]
It's all about the size of the CLOUD ITSELF, and last but not least, the size of the water droplets. Just if you look carefully, even ordinary clouds come in different shades - with a transition from white to gray. That is, it is clear that 1) white differs from gray simply in the amount of light that reaches the lower boundary of the cloud, and 2) the key factor here is how much sunlight needs to travel through the cloud. The thicker the cloud (thunderclouds are several kilometers thick!), the more light is scattered/absorbed. This means that the less of it reaches the lower boundary of the cloud. This means that the darker it looks from BOTTOM. If you look at a thundercloud from above (it’s easy from an airplane), then all the clouds there are white, because reflection occurs the same way, and absorption, when you look from the SIDE OF THE LIGHT SOURCE, does not affect it.
Reply from Lexus Swift[guru]
Since white clouds are composed mainly of large drops of water, sunlight passing through them is not separated into its components and remains white. Thunderclouds have a denser structure and reflect rays of light back upward, so it appears to us that the clouds are black.
Reply from Fourth Dimension[guru]
The size of the water droplets in the cloud is quite large, and light is reflected from their outer surface. With this reflection, the light does not decompose into its component colors, but remains white. Very dense clouds appear black because they allow little sunlight to pass through - it is either absorbed by water droplets in the cloud or reflected upward.
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Why are clouds white and clouds black, how are clouds and mirages born, and is it true that there is a Society of Cloud Lovers? Let's talk.
This is the motto of The Cloud Appreciation Society, an international organization founded in 2004 in England by Gavin Praetor-Pinney. It unites 30,000 cloud lovers from 94 countries. These are people who dream of revealing the beauty of the cloudy sky to others. Join us!
You just need to lie on the grass and watch the clouds. Or just look up. Anytime you want.
How is a cloud born?
When hot air mixes with cold air, it cools and can reach its dew point. Condensation occurs. Water vapor, settling on a particle in the air, turns into drops or ice crystals, which, when collected together, form a cloud.
Most often this happens when hot air rises from the ground and meets cold air above - in the atmosphere. A cloud-like phenomenon can also be observed at the surface of the earth. Earth or water, heated during the day, cools more slowly than air. When cold night air comes into contact with warm air near the surface of the earth or water, fog is formed.
Yes, yes, fog also consists of cloud elements. It is essentially a large cloud lying on the ground.
Why are clouds white and clouds black?
If clouds are made of droplets, why are they white? Because cloud elements reflect light: crystals and droplets glisten in the rays of the sun. And the smaller the elements in size and the more of them in number, the whiter the cloud.
Gray, bluish and black thunderclouds consist of the same drops. It’s just that, in heavy clouds, they can cast shadows on each other (and even on themselves), which is why they appear darker. There are also denser clouds - they consist of large crystals and drops, so the rays of the sun cannot penetrate through them. They appear dark and ominous when viewed from the ground.
But if you fly over them, for example on an airplane, they will be completely white.
How a mirage is formed
A cloud forms when warm air rises. This hot rising air current is called a thermal. Birds and gliders soar on it.
The thermal can be seen if you look at a paved road on a hot day. It seems that the air above the asphalt is shaking, and the road seems to be covered with puddles. This phenomenon is called a mirage.
A mirage can be seen when hot and cold air that have different densities meet. At the boundary of media with different densities, a ray of light is refracted, and we see a mirage.
Clouds are not just wisps of cotton that block the sun. They are no less beautiful than the stars. After reading this book, you will see for yourself.
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 oppressing 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 fact the atmospheric dome is closer to a violet hue when viewed 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
Over the territory of 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 you devote at least one day to what is happening above our heads and carefully observe natural processes, you will notice a gradation of color that 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 and the absence of a large number of clouds, which, accumulating water, gradually sink 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 the maximum rise of the celestial 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 pass tangentially to the surface of the Earth, the light emitted by them needs to travel a longer path, which means they are scattered 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 at high altitudes, 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 shapes, and therefore 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 overtones, 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...
The tones in which the sky plays depends on the intensity of light radiation and the wavelength reaching the planet, so in winter, even on clear days, it is bluish-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 layers of the atmosphere, distorting the light, dissipates.
Scientists have found that on other planets the sky may not have the usual blue and gray colors at all; on Mars, for example, it is pink even at the height of daylight.