Why is the sky blue during the day and red in the evening? What color is the sky? Why is the sky blue from a physics point of view? Blue violet sky.
Why the sky is blue?
“Dad, why is the sky blue and not, say, green or purple?”
Children, when they begin to explore the world around them, very actively ask questions. Hundreds of questions a day about everything that comes into focus. All you can hear is “why, why.” And dad (or mom) just can’t “fall face down in the dirt” and lose authority by saying “I don’t know.” How can this even be, since he has been living for a very long time and knows such basic things for sure from his childhood?
And dad, of course, knows why the sky is suddenly blue 😉, and if he suddenly forgot something, he carefully reads what is written below.
What color is sunlight?
To understand the color of the sky and understand why it is this way, you first need to find out what color the sunlight is. This question seems elementary.
“Yellow,” the baby will tell you, but here he will have to be surprised for the first time.
“But it’s not yellow!”
O_O – these are the eyes the baby will have (obviously something is wrong with dad).
“Come on, raise your head, dad! It's yellow! Why not? Very much so!”
“But no!” Then dad makes an authoritative face and says:
“In fact, the color of the sun and its rays is white, and the fact that we see it yellow is because it becomes so after passing through the air.”
What is white made of?
“What colors do you know?” - the father asks the child.
“Green, yellow, red, white...” the baby begins to list.
“Good girl! All the colors you listed, except white, are simple colors. But the white one is special! There is no such thing as just white in nature, but it appears when you put all the simple colors together.
It's like in a game when you need to collect parts of an object. So you take one part, the second, the third, etc., and when you collect everything - TADAM! You get the whole item! So is white - it consists of all colors, and if you take at least some shade from it, it will no longer be white. It's clear?"
“Yeah,” the baby nods.
So what's up with the color of the sky? Why is it blue?
“This is all very interesting, but I think you’re going off topic. What about the color of the sky? Why is it like this?
“I’m just getting to this point. I told you elementary things so that I could explain more complex things in my fingers.
Regarding the sky, I must say this. Scientists have not yet found an absolutely accurate answer, but there are two simple theories that explain why the shade of the sky is blue. I'll tell you both.
First theory:
A large number of particles fly in the air that surrounds the earth - these are various gases, dust particles, water particles, etc. When a white ray from the sun (and, as you remember, it is not by itself, but all the colors together) hits the air, it collides with particles of air and particles that fly in the air, and begins to crumble into the colors of which it was composed.
It turned out that not all of them are equally nimble, some are very clumsy, they scatter in the air when they collide with some particles, while others, very fast, dodge collisions and fly to the Earth.
Blue rays are slow, they hit obstacles more often than others and scatter (scatter) in all directions, illuminating the air with blue light.
Second theory a little more complicated:
Scientists suggest that particles of air that surround the Earth absorb the sun's rays. They seem to be charged by these rays, and then begin to emit their own light in all directions.
Well, for example, like a door on a stove. Do you remember how I showed you how the door was black at first, and then it warmed up and began to glow red? Do you remember?
“Yeah, I remember. Why did you remember the stove?” .
“Yes, because it’s the same here. Air particles receive energy from the sun's rays and then begin to glow. Different gases glow differently. The fact that we see the sky blue, according to this theory, it is thanks to the gases that make up our air (oxygen and nitrogen) that they emit a blue color. But if instead of them there were, for example, neon (there is such a gas), then the sky would glow red-orange, but we would not be able to enjoy this spectacle, because wouldn't be able to breathe.
Therefore, I think that even if it remains blue, blue is also nothing, right?”
“I agree,” the baby nodded, and a minute later, seeing the dog, he asked the following vital question: “Dad,
Everyone has long known how inquisitive children are. They sometimes ask questions that make adults blush. It seems that everything is elementary and simple, however, it is difficult for many parents to give an answer at the same moment. In order to avoid getting into such difficult and awkward situations when talking with a child, you need to prepare for them thoroughly.
Therefore, we will look at the questions that are most often heard from children and that are of interest to adults.
The phrase asking about the shade of the sky puts many parents in a rather awkward position. Children are interested in why the sky is light blue, not yellow, not red, because space is black? But if we, adults, find it difficult to answer, it means that we ourselves do not really know the answer to this question, and it has never occurred to us to ask it. And many, not knowing the correct answer, change the topic.
Light, which consists of 7 shades of the spectrum, usually passes through the atmosphere. A collision of solar photons occurs with many gas molecules contained in the air. This leads to a phenomenon called scattering. The most interesting point concerns the number of particles that emit short-wave blue radiation. There are 8 times more of them. It turns out that on the way to Earth the shade of the sun's rays changes from white to light blue. How to explain all this to a child? But the child is still very small, why talk to him about photons of solar rays that collide with gas molecules.
Short answer in conversation for children
The air that surrounds us contains tiny and constantly moving particles - gases, dust particles, specks, water vapor. They are so small that they can only be seen under a microscope, and sunlight is a harmony of seven shades. The beam that passes through the air has to collide with small particles. And this leads to the fact that the shades in it are separated. And since there is more light blue in the color spectrum, that’s all we see. Or you can simply answer briefly that the sun's rays color the air in a light blue hue.
Joking (original) answer
Everyone thinks that the air is transparent, but it is a light blue shade. We are very, very far from the sun. Looking at the top, we can only see a thick layer of air. It is so pure that it appears light blue. It is also possible to jokingly answer that it is light blue, because in the game of who is faster, the light blue shade always wins.
Funny answer for adults
Why the sky is blue? - This is all my family, the blue ones always have this!
Video presentation to children
Why is the sea blue, the grass green, and the sunset red?
Sea
The hue of the sea water depends on how deep the rays penetrate. The sea has good abilities in absorbing and scattering any rays. But the yellow tint of the beam is absorbed much faster, even not at depth. And the absorption of the blue tint of the beam is very slow, even at great depths. That's why it seems to us that the water in the sea is blue. The shade of the sea can be transparent, blue, or green.
Grass
The green leaf absorbs carbon dioxide into the cells and releases oxygen into the air. He desperately needs this. But what does this have to do with? The sun is the main source of life. The sun's rays fall on the leaves. Their cells contain a green substance called chlorophyll. Leaves and grass live well thanks to their chlorophyll content, which produces essential nutrients.
The substances produced by chlorophyll are well known to us in the form of sugar, starch and protein. They are found both in the cells of plants, animals, and in the cells of the human body. And the production of these useful substances occurs from carbon dioxide. The green leaf is an amazing factory. If the sun's rays touched a leaf, then we can talk about their wonderful life. If there is no sunlight, then there is no factory.
Sunset
You've probably often wondered about the color of the sky at sunset. Perhaps many people are interested in why the sky at sunset is sometimes scarlet and sometimes red. What is this connected with?
This is because red is the longest wavelength of light. It can break through a thick layer of air. But why does it look light blue only in clear weather?
And this is also explained quite simply. When the weather is cloudy, most of the sun's rays simply do not reach the surface of the earth. And what can still break through begins to refract drops of water suspended in the air. The light wave is distorted. If the color of the sky is gray, then this is the same process, but with larger clouds. So we examined the question regarding the blueness of the sky and the redness of the sunset. These issues can be studied in more detail by becoming familiar with the objective laws of physics.
Why are the skies blue from the point of view of science: physics, chemistry?
Our planet is surrounded by air, which forms the atmosphere. Atmospheric air contains large amounts of oxygen, carbon dioxide, nitrogen, water vapor, and microscopic dust particles that are constantly moving.
Sunlight manages to penetrate the atmospheric layers of air. Gases contained in the air work in the decomposition of white light into 7 components, spectra. These are all the colors of the rainbow and that is why it seems to us that the sky is light blue. The Moon has no atmosphere and appears to be black. Astronauts entering orbit on spaceships get to see a beautiful black velvet sky with sparkling stars and planets.
Wikipedia about the blue color of the sky
Wikipedia informs that the sky only appears light blue. In reality, all other colors of rays, in addition to light blue, indigo and violet, are scattered by the sky. All of them together appear light blue to us.
Why is it light blue?
Sunlight has 7 colors in its spectrum that are connected together - red, orange, yellow, light blue, indigo and violet. You can look at the pictures and remember the rainbow. Each ray needs to pass through a thick air layer. And at this moment the shades splash. Light blue is visible to us more than others, since it is very persistent.
What does the Bible say: what makes the sky blue?
The sky is light blue because the Almighty wanted to create it that way.
Expression about blue sky translated into English
Out of a clear blue sky - clear blue sky.
Scientists have found blue skies on Pluto and traces of lakes on Mars
Scientists have discovered organic particles called tholins in Pluto's atmosphere. They themselves are gray or red. When they reflect sunlight, the atmosphere of this planet appears light blue. In addition, several small areas covered with ice were discovered here.
Another discovery has a connection with the planet Mars. Scientists prove that in the distant past for many years, the surface of this planet was covered with lakes. Not long before this, there was some evidence of the existence of salt water on Mars. It is the flow of salt water that many scientists believe is responsible for the fact that the planet's surface has dark stripes. They appear at a time when the temperature on a given planet rises above - 23 degrees. They disappear when cold weather sets in.
The bottomless blue sky amazes with its splendor and purity. Whether the Creator created it this way or whether it appeared on its own during the process of formation is not so important.
The main thing is that on clear sunny days a person sees a beautiful blue expanse of sky above his head, which fills his heart and soul with the light of life. Many poetic lines have been written about the blueness of the firmament; the blue-blue sky is captured in thousands of amateur and professional photographs; the sky inspires artists to create truly magical landscapes and, finally, the transparent blue sky can be called a symbol of Eternity and Love.
While admiring the beauty of the sky, many of us do not think about why the sky is blue during daylight hours. But one day, having decided to find the answer to this question, a person may encounter obscure explanations.
If you are by nature more of a lyricist than a physicist, then what is written in this article will seem clear and accessible to you. And simply knowing the reason why the sky is blue will not deprive you of a reverent attitude towards the infinitely blue, like a huge sea.
Most often, the sky is the dome-shaped space above the earth, which consists of a mixture of nitrogen, oxygen, carbon dioxide and water vapor. The blue color of the sky comes from the sun's rays penetrating the atmosphere. What happens in the sky with the rays of the sun, which are multicolored by nature? When sunlight hits air molecules, it scatters onto them. And the smaller components of the air mass - electrons - emit this light. 
According to Rayleigh's law, light with shorter wavelengths scatters faster. And the blue, indigo and violet color spectrum, into which a solar ray decomposes during interaction with gases, has a significantly shorter wavelength than red, yellow, orange and green. As a result, it turns out that blue-blue directly depends on the speed of dispersion of waves corresponding in color.
The same principle explains the red color of the sky at sunset. As night approaches, the Earth's atmospheric layer increases, and short rays of the blue, blue and violet spectrum are scattered in the upper layers. And in that part of the atmosphere that a person sees, the rays of the red spectrum predominate.
Whatever the sky above our heads, it is inseparably connected with all the processes occurring in the Earth’s atmosphere. Whether it rains or snows, the sky will certainly turn gray. In inclement weather the sky is said to frown or cry. This means that in people’s imaginations the sky is captured in blue-blue tones.
The dream of a blue sky on rainy days never leaves a person. Even those who love the melancholy mood evoked by rain look forward to the sunbeam appearing from behind the clouds and the sky shining with its alluring blue.
In summer there is nothing more beautiful than lying in the soft fragrant grass and looking at the sky. To drown your eyes in it and not think about why it is so blue. Watch the measured flight of birds and not remember that the sky can be truly angry. 
Trying to see angels in the sky and not feel the hot rays of the sun on your skin. You can experiment with the sky, show your imagination, just live. And, following the famous lines of the Russian poet Boris Pasternak
“In everything I want to get to the very essence
In work, in search of a path, in heartfelt turmoil..."
to get to the essence of the sky, which is certainly contained in its wonderful blueness.
To do this, you don’t need to become an artist, poet, musician - you can learn to feel the sky not only above your head, but also inside yourself, being a teacher, a taxi driver, and a businessman. By sorting life along the color spectrum, like a sunbeam, you need to quickly become a participant in various events and at the same time scatter exceptionally pure, kind light, reminding people of the blue sky.
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 known from 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 solid particles are not 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.
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.
The ancient Greeks believed: “The sky is blue because it is made of the purest rock crystal!” Moreover, the crystal is multi-layered - that is why it has a blue color. If you place a piece of ordinary glass in front of you, it will be transparent. However, if you put several pieces in a pile and try to look through them, it turns out that you will see not what is actually behind the entire structure, but some kind of incomprehensible blueness.
So in our case, the sky is a series of crystal spheres, which are located one inside the other with jewelry precision. In the middle of this entire set of spheres is the Earth with its fortresses, taverns, roads, mountain peaks, temples, cities and seas. On one sphere there is a brightly blazing Sun. On the other sphere is the Moon. The third sphere is strewn with an endless number of stars, which every now and then break away from the crystal surface and fall down. All other spheres place on themselves one of a large number of planets.
All these spheres rotate, and each has its own direction and speed. They rotate without grinding or creaking, and in the very center of this amazing system our unique and important planet is located in the “global” emptiness. Must be a magnificent sight!
The ancient Greeks sincerely believed in this theory of why the sky is blue. However, what exactly made them think so? After all, the sky cannot be touched, it can only be contemplated. Contemplate and reflect, build the most incredible guesses. Nowadays, such guesses are usually called “scientific theory”, but the ancient Greeks did not bother and called them that - guesses.
Why is the sky blue (according to scientists)?
Modern scientists were able to find the correct answer and prove why the sky is blue. Physics hid this secret for quite a long time, or rather the atmosphere of our planet. As everyone knows, air itself is a colorless gas, however, when the sun's rays penetrate it, the light begins to break up into 7 primary colors:
Since in this process blue and blue colors have a clear advantage - that’s why we see the sky as blue-blue.
The most successful example of this process is the comparison of day and night. At night there are no sun rays, since the Sun will currently illuminate the opposite side of the planet. Thanks to the absence of light, we can see the true color of the atmosphere, to be precise, the absence of any color, transparency. Through the transparent air we have the opportunity to see other galaxies, stars, plateaus, black space. The moment the Sun begins to illuminate our side of the planet again, the sky becomes azure. Thus, the sky is a kind of blue curtain, behind which space is hidden from us during daylight hours. That is why the sky is blue during the day and transparent at night, which is why it seems black to us.
Why is the sky blue only during clear weather? The fact is that in cloudy weather the entire spectrum of light rays is simply unable to penetrate to the surface of the Earth, and those few rays that were able to reach us are refracted by water, which is suspended at a very high altitude. It is this water that distorts light waves.
Now you are convinced that the whole reason for the change in the colors of the sky is in the unshakable laws of physics.