Tell me why the sky is blue. Why is the sky blue and the sunset red? Description, photo and video. The phenomenon of blue sky in terms of physics

Sunlight is white, that is, it includes all the colors of the spectrum. It would seem that the sky should also be white, but it is blue.

Surely your child knows the phrase "Every Hunter Wants to Know Where the Pheasant Sits", which helps to remember the colors of the rainbow. And a rainbow is the best way to understand how light breaks up into waves of different frequencies. The longest wavelength is for red, the shortest for violet and blue.

The air, which contains gas molecules, microcrystals of ice and water drops, scatters light with a shorter wavelength more strongly, so there are eight times more blue and purple colors in the sky than red ones. This effect is called Rayleigh scattering.

Draw an analogy with balls rolling down a corrugated board. The larger the ball, the less likely it is to veer off course or get stuck.

Explain why the sky cannot be other colors

Why isn't the sky purple?

It is logical to assume that the sky should be purple, because this color has the shortest wavelength. But here the features of sunlight and the structure of the human eye come into play. The spectrum of sunlight is uneven, there are fewer shades of violet in it than other colors. And part of the spectrum is not visible to the human eye, which further reduces the percentage of shades of purple in the sky.

Why isn't the sky green?

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A child may ask, "Since scattering increases with decreasing wavelength, why isn't the sky green?" Not only blue rays are scattered in the atmosphere. Their wave is the shortest, so they are the most noticeable and brightest. But if the human eye were arranged differently, the sky would seem green to us. After all, the wavelength of this color is slightly longer than that of blue.

Light is arranged differently than paint. If you mix green, blue and purple paints, you get a dark color. With light, the opposite is true: the more colors are mixed, the lighter the result is.

Tell me about the sunset

We see blue skies when the Sun shines from above. When it approaches the horizon, and the angle of incidence of the sun's rays decreases, the rays go tangentially, passing a much larger path. Because of this, waves of the blue-blue spectrum are absorbed in the atmosphere and do not reach the Earth. Red and yellow colors scatter in the atmosphere. Therefore, at sunset the sky turns red.

The light loves to play tricks on us, but, as a result, a multi-coloredebo, for the sake of which it is worth going on a trip.

The answer to the question: "Why is the sky blue?" almost the same as “Why do colors exist?” The color is light as we are able to accept it. The sky consists of many colors (dominant - blue), because it is saturated with light.

Visible light, a type of electromagnetic radiation, is a narrow subset of a broad spectrum of energy that includes radio waves, microwaves, ultraviolet light, x-rays, and gamma radiation. The white light that the sun emits is a combination of all the different wavelengths of electromagnetic waves available to our eyes.

Color appears when our eyes are focused on only certain wavelengths. Red light, for example, is the slowest wave we can see: energy travels in long and undulating ripples. Blue, on the other hand, appears to be the fastest: energy that quivers in a changeable and fast rhythm.

The sky changes its color to white due to the sun hitting the Earth's atmosphere. Light waves - along with the rest of the electromagnetic spectrum - will travel in a straight line until they hit something.

The sky is often beyond our view due to the presence of complex combinations of gas and particles. White light travels a long way to get from the sun to our eyes.

The most pierced are blue waves. Due to its small size, this wave has a high probability of being hit as an obstacle and dispersed in all directions. Ultimately, the sky from anywhere in the world will look blue.

When a whole spectrum of visible color penetrates the sky, not only red and blue waves are hardly distinguishable, but also orange, yellow, green, purple ..

Looking up at the sky at noon, you'll notice the blue egg of a beautiful robin, a cotton candy-streaked sunset, or a dramatic red dawn—it's all tricks of the light.

It turns out that these tricks ennoble some attractions or help create great travel photos.

Most of the time, the sky above the earth's surface appears in a blue color. But think about it: is the sky really that color? What about rainy days or "red skies at night" that sailors enjoy?

The sky is blue due to sunlight interacting with our atmosphere. If you have ever played with a prism or seen a rainbow, then you probably know that light is made up of many different colors. Suffice it to recall the well-known phrase about a hunter who wants to know the location of a pheasant. Thus, the sky consists of red, orange, yellow, green, blue, indigo and violet.

These colors make up a tiny part of the electromagnetic spectrum, which includes ultraviolet waves, microwaves, and radio waves. Accordingly, the white light that comes from the sun is a combination of different wavelengths of electromagnetic waves that we can see with our own eyes.

Light is driven by waves of completely different wavelengths: short waves that produce blue light and long waves that produce red light. Thanks to sunlight reaches our atmosphere, the molecules in the air scatter the blue light, allowing the red light to pass through. Scientists call this Rayleigh scattering.

When the sun is high in the sky, it shows its true color: white. At sunrise and sunset, we see the sun in red hues. This is due to the fact that sunlight passes through a thick layer of our atmosphere. The blue and green light is scattered, allowing the red light to pass through and illuminate the clouds in gorgeous scarlet, orange and pink.

Rayleigh scattering can also affect the Moon. When the Moon passes through the shadow cast by the Earth during a total lunar eclipse, blue and green light is scattered in the Earth's atmosphere, giving way to red light. Our atmosphere is like a magnifying glass that reflects red sunlight onto the moon. Such a display can give it an eerie dark red hue.

That is why many cultures, including Australian indigenous groups, associate lunar eclipses with blood.

And finally, where does the sky begin?

This is a tricky question. A bird flying 50 meters above ground level is in the sky. However, planes are also located there, but at an altitude of over 10,000 meters.

The sky is only part of our atmosphere. A huge amount of atmosphere stretches up to 16 km, and this is where Rayleigh scattering occurs.

Relax and don't let the snake unravel?

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Why the sky is blue?

“Dad, why is the sky blue and not, say, green or purple?”
Children when they start learning the world are very active in asking questions. Hundreds of questions a day about anything that comes under the spotlight. All you hear is "why-why". And dad (or mom) by no means can "fall face down" and lose authority, saying "I don't know." How can this even be, because he has been living for a very long time and knows such elementary things for sure from his childhood?
And dad, of course, knows why this 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, you first need to find out what color the sunlight has. 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 - the baby will have approximately the same eyes (something is clearly wrong with dad).
“Come on, raise your head, dad! It's yellow! Why is it not? Very much yes!”
“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 up of?

"What colors do you know?" the child's father asks.
"Green, yellow, red, white ..." - the kid begins to list.
“Clever! All those colors that you listed, except for white, are simple colors. But the white one is special! In nature, there is no just white, but it appears if you put together all the simple colors.
It's like in a game when you need to collect parts of an object. Here 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 at least some shade is taken away from it, it will no longer be white. Understandably?"
"Yeah," the kid nods.

So what's up with the color of the sky? Why is it blue?

“All this is very interesting, but, in my opinion, you are moving away from the topic. How about the color of the sky? Why is it like this?
“I'm just getting there. I told you elementary things so that more complex ones could be explained on the fingers.
As for the sky, I must say this. Scientists have not yet found an absolutely exact answer, but there are two simple theories that explain why the shade of the sky is blue. I'll tell you both.

First theory:

In the air that surrounds the earth, a large number of particles fly - these are different 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) enters the air, then colliding with particles of air and particles that fly in the air, it begins to crumble into the colors of which it consisted.
It turned out that not all of them are equally fast, some are very clumsy, they disperse in the air, colliding with some particles, while others, very fast, dodge collisions and reach the Earth.
Blue rays are clumsy, they most often fall on obstacles and scatter (scatter) in all directions, illuminating the air with blue light.

Second theory a little more complicated:

Scientists suggest that particles of the air that surrounds the Earth absorb the sun's rays. They, as it were, are charged from these rays, and then begin to radiate their own light in all directions.

Well, for example, like a door on a stove. Remember, I showed you how the door was black at first, and then warmed up, warmed up and began to glow red? Do you remember?
“Yeah, I remember. And why did you remember the stove? .
“Yes, because it is the same here. Particles of air 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 would be, 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. couldn't breathe.
Therefore, I think that even if it remains blue, blue is also okay, right?
“I agree,” the kid nodded, and after a minute, when he saw the dog, he asked the following vital question: “Dad, and

When the wind throws a white fluffy transparent cape over the beautiful blue sky, people begin to look up more and more often. If at the same time it also puts on a large gray fur coat with silver threads of rain, then those around hide from it under umbrellas. If the outfit is dark purple, then everyone is sitting at home and wanting to see the sunny blue sky.

And only when such a long-awaited sunny blue sky appears, which puts on a dazzling blue dress decorated with golden sunbeams, people rejoice - and smiling, leave their homes in anticipation of good weather.

The question of why the sky is blue has puzzled people's minds since time immemorial. Greek legends have found their answer. They claimed that this shade is given to it by the purest rock crystal.

At the time of Leonardo da Vinci and Goethe, they were also looking for an answer to the question why the sky is blue. They believed that the blue color of the sky is obtained by mixing light with darkness. But later this theory was refuted as untenable, since it turned out that by combining these colors, you can get only the tones of the gray spectrum, but not the color one.

After some time, the answer to the question of why the sky is blue was tried to be explained in the 18th century by Mariotte, Bouguer and Euler. They believed that this was the natural color of the particles that make up the air. This theory was popular even at the beginning of the next century, especially when it was found that liquid oxygen is blue, and liquid ozone is blue.

The first more or less sensible idea was given by Saussure, who suggested that if the air were completely clean, without impurities, the sky would turn out to be black. But since the atmosphere contains various elements (for example, steam or water drops), they, by reflecting color, give the sky the desired shade.

After that, scientists began to get closer and closer to the truth. Arago discovered polarization, one of the characteristics of scattered light that bounces off the sky. In this discovery, the scientist was definitely helped by physics. Later, other researchers began to look for the answer. At the same time, the question of why the sky is blue was so interesting for scientists that a huge number of different experiments were carried out to clarify it, which led to the idea that the main reason for the appearance blue color that the rays of our Sun are simply scattered in the atmosphere.

Explanation

Rayleigh, a British researcher, was the first to create a mathematically sound answer to molecular light scattering. He suggested that light is scattered not because of the impurities that the atmosphere possesses, but because of the air molecules themselves. His theory was developed - and here are the conclusions scientists came to.

The sun's rays make their way to the Earth through its atmosphere (a thick layer of air), the so-called air shell of the planet. The dark sky is completely filled with air, which, despite being completely transparent, is not a void, but consists of gas molecules - nitrogen (78%) and oxygen (21%), as well as water droplets, steam, ice crystals and small pieces of solid material (for example, particles of dust, soot, ash, ocean salt, etc.).

Some rays manage to freely pass between gas molecules, completely bypassing them, and therefore reach the surface of our planet without changes, but most of the rays collide with gas molecules that come into an excited state, receive energy and release multi-colored rays in different directions, completely coloring the sky, resulting in a sunny blue sky.

White light itself consists of all the colors of the rainbow, which can often be seen when it is broken down into its component parts. It so happens that blue and violet colors scatter the most because they are the shortest part of the spectrum, since they have the shortest wavelength.

When mixed in an atmosphere of blue and purple with a small amount of red, yellow and green, the sky begins to "glow" blue.

Since the atmosphere of our planet is not homogeneous, but quite different (it is denser near the Earth's surface than at the top), it has a different structure and properties, we can observe blue overflows. Before sunset or sunrise, when the length of the sun's rays increases significantly, blue and purple colors are scattered in the atmosphere and absolutely do not reach the surface of our planet. The yellow-red waves successfully reach, which we observe in the sky during this period of time.

At night, when the sun's rays, falling on a certain side of the planet, have no opportunity, the atmosphere there becomes transparent, and we see the "black" space. This is how astronauts above the atmosphere see it. It is worth noting that the astronauts were lucky, because when they are over 15 km above the earth's surface, during the day they can simultaneously observe the Sun and stars.

Sky color on other planets

Since the color of the sky is largely dependent on the atmosphere, it is not surprising that on different planets it is of different colors. Interestingly, the atmosphere of Saturn is the same color as on our planet.

Very beautiful aquamarine skies of Uranus. Its atmosphere consists mainly of helium and hydrogen. It also contains methane, which completely absorbs red and scatters green and blue. The blue skies of Neptune: in the atmosphere of this planet there is not as much helium and hydrogen as ours, but there is a lot of methane, which neutralizes the red light.

The atmosphere on the Moon, a satellite of the Earth, as well as on Mercury and Pluto, is completely absent, therefore, light rays are not reflected, so the sky is black here, and the stars are easily distinguishable. blue and green colors the sun's rays are completely absorbed by the atmosphere of Venus, and when the Sun is near the horizon, the skies here are yellow.

Despite scientific progress and free access to many sources of information, rare person can correctly answer the question why the sky is blue.

Why is the sky blue during the day?

White light - namely, it radiates from the Sun - consists of seven parts of the color spectrum: red, orange, yellow, green, blue, indigo and violet. The counting rhyme known from school - "Every Hunter Wants to Know Where the Pheasant Sits" - just determines the colors of this spectrum by the initial letters of each of the words. Each color has its own wavelength of light: the longest for red and the shortest for purple.

The sky (atmosphere) familiar to us consists of solid microparticles, tiny drops of water and gas molecules. Over time, there have been several misconceptions trying to explain why the sky is blue:

• the atmosphere, consisting of the smallest particles of water and molecules of various gases, passes the rays of the blue spectrum well and does not allow the rays of the red spectrum to touch the Earth;
• small solid particles - for example, dust - suspended in the air scatter blue and violet waves 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 studies English physics 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 the light into color components. A white sunbeam, colliding with a gas particle in the sky, scatters (scatters) in different directions.

When colliding with a gas molecule, each of the seven color components of white light is scattered. In this case, light with longer wavelengths (the red component of the spectrum, which also includes orange and yellow) is scattered worse 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 wavelengths. In addition, our eyes perceive blue better than purple, with the same brightness of both. It is these facts that determine the color scheme of the sky: the atmosphere is literally filled with blue-blue rays.

Why is the sunset red then?

However, the sky is not always blue. The question naturally arises: if we see blue skies all day long, why is the sunset red? Above, we found that red is the least scattered by gas molecules. During sunset, the Sun approaches the horizon and the sunbeam is directed to the Earth's surface not vertically, as during the day, but at an angle.

Therefore, the path that 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 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, warms up near the surface of the earth, rises and expands due to the fact that the air pressure at the top is less. As it expands, the air cools. When a certain temperature is reached, water vapor condenses around atmospheric dust and other suspended solids, and as a result, tiny droplets of water are formed, the merger of which forms a cloud.

Despite their relatively small size, water particles are much larger than gas molecules. And if, meeting air molecules, the sun's rays are scattered, then when they meet water drops, the light is reflected from them. At the same time, the initially white sunbeam does not change its color and at the same time “paints” the cloud molecules white.