Why is the sun red at sunset? Why the sun is red: mythology, omens. Black sky and white sun

One of distinguishing features man is curiosity. Probably everyone, as a child, looked at the sky and wondered: “why is the sky blue?”. As it turns out, the answers to such seemingly simple questions require some knowledge in the field of physics, and therefore not every parent will be able to correctly explain to the child the reason for this phenomenon.

Consider this issue from a scientific point of view.

The wavelength range of electromagnetic radiation covers almost the entire spectrum of electromagnetic radiation, which includes radiation visible to humans. The image below shows the dependence of the intensity of solar radiation on the wavelength of this radiation.

Analyzing this image, one can note the fact that visible radiation is also represented by uneven intensity for radiation of different wavelengths. So a relatively small contribution to visible radiation makes the violet color, and the largest - blue and green colors.

Why the sky is blue?

First of all, we are led to this question by the fact that air is a colorless gas and should not emit blue light. It is obvious that the cause of such radiation is our star.

As you know, white light is actually a combination of radiation of all colors of the visible spectrum. Using a prism, you can explicitly decompose light into the entire range of colors. A similar effect occurs in the sky after rain and forms a rainbow. When sunlight enters the earth's atmosphere, it begins to scatter, i.e. radiation changes its direction. However, the peculiarity of the composition of air is such that when light enters it, radiation with a short wavelength is scattered more than long-wave radiation. Thus, taking into account the spectrum shown earlier, it can be seen that red and orange light will practically not change its trajectory, passing through the air, while violet and blue radiation will noticeably change their direction. For this reason, a kind of "wandering" short-wave light appears in the air, which is constantly scattered in this medium. As a result of the described phenomenon, it seems that short-wave radiation of the visible spectrum (violet, blue, blue) is emitted at every point in the sky.

The well-known fact of the perception of radiation is that the human eye can catch, see, radiation only if it directly hits the eye. Then, looking at the sky, you will most likely see the shades of that visible radiation, the wavelength of which is the smallest, since it is it that scatters best in the air.

Why don't you see a distinctly red color when you look at the Sun? Firstly, a person is unlikely to be able to carefully examine the Sun, since intense radiation can damage the visual organ. Secondly, despite the existence of such a phenomenon as the scattering of light in the air, nevertheless, most of the light emitted by the Sun reaches the surface of the Earth without being scattered. Therefore, all the colors of the visible spectrum of radiation are combined, forming light with a more pronounced white color.

Let us return to the light scattered by the air, the color of which, as we have already determined, should have the smallest wavelength. Of the visible radiation, violet has the shortest wavelength, followed by blue, and has a slightly longer wavelength. blue color. Taking into account the uneven intensity of the solar radiation, it becomes clear that the contribution of the violet color is negligible. Therefore, the largest contribution to the radiation scattered by the air is blue, followed by blue.

Why is the sunset red?

In the case when the Sun hides behind the horizon, we can observe the same long-wave radiation of red-orange color. In this case, the light from the Sun must travel a noticeably greater distance in the Earth's atmosphere before reaching the observer's eyes. In the place where the radiation of the Sun begins to interact with the atmosphere, blue and blue colors are most pronounced. However, with distance, shortwave radiation loses its intensity, as it is significantly scattered along the way. While longwave radiation does an excellent job of overcoming such large distances. This is why the Sun is red at sunset.

As mentioned earlier, although long-wave radiation is weakly scattered in air, there is still scattering. Therefore, being on the horizon, the Sun emits light, from which only the radiation of red-orange hues reaches the observer, which has some time to dissipate in the atmosphere, forming the previously mentioned "stray" light. The latter paints the sky in variegated shades of red and orange.

Why are clouds white?

Speaking of clouds, we know that they are made up of microscopic droplets of liquid that scatter visible light almost uniformly, regardless of the wavelength of the radiation. Then the scattered light, directed in all directions from the droplet, is scattered again on other droplets. In this case, the combination of radiation of all wavelengths is preserved, and the clouds "glow" (reflect) in white.

If the weather is cloudy, then solar radiation reaches the Earth's surface in an insignificant amount. In the case of large clouds, or a large number of them, some fraction sunlight is absorbed, because the sky dims and takes on a gray color.

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 the studies of 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 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 color scheme sky: the atmosphere is literally filled with rays of blue-blue color.

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. Wet air, containing invisible vapor, heating up at 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. Upon reaching certain temperature water vapor condenses around atmospheric dust and other suspended solids to form 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, 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 “colors” in White color cloud molecules.

It would seem that at school every diligent and not very diligent student knows what colors the spectrum is decomposed into, what each of the colors represents. However, no matter how diligently a child studies, he will never be answered the main questions that have been troubling his restless mind from the very beginning. early childhood: why is the sky blue and why is the sunset red?

If you plunge a little into physics, you can find that the red spectrum has the worst scattering. That is why, in order for the lights of an object to be visible from afar, they are made red. And yet, why is the sunset red and not blue or green?

Let's try to think logically. When the sun is directly at the horizon, its rays have to overcome a much greater layer of the atmosphere than when the sun is at its zenith. Due to its low scattering, the red color passes through this layer of the atmosphere almost unhindered, and all other colors of the spectrum are scattered so strongly, passing through the thickness of the Earth's air space, that they are actually not visible at all. That's why the sunset is red!

From this we can conclude that the sunset will be the redder, the greater the layer of the atmosphere between the sun and our eye. Also, in order for the sunset to be redder, or even crimson, you just need to dust and pollute the air, then colors other than red will scatter even more.

The world around us is full of amazing wonders, but we often do not pay attention to them. Admiring the clear blue of the spring sky or the bright colors of the sunset, we do not even think about why the sky changes color with the change of time of day.


We are accustomed to bright blue on a fine sunny day and to the fact that in autumn the sky becomes hazy-gray, losing its bright colors. But if you ask modern man about why this happens, the vast majority of us, once armed with school knowledge of physics, are unlikely to be able to answer this simple question. Meanwhile, there is nothing complicated in the explanation.

What is color?

From school course In physics, we should be aware that differences in the color perception of objects depend on the wavelength of light. Our eye can only distinguish a fairly narrow range of wave radiation, with blue being the shortest and red being the longest. Between these two primary colors lies our entire palette of color perception, expressed by wave radiation in different ranges.

A white sunbeam actually consists of waves of all color ranges, which is easy to verify by passing it through a glass prism - you probably remember this school experience. In order to remember the sequence of changing wavelengths, i.e. the sequence of colors in the spectrum of daylight, invented a funny phrase about a hunter that each of us learned in school: Every Hunter Wants to Know, etc.


Since red light waves are the longest, they are the least susceptible to scattering during transmission. Therefore, when you need to visually highlight an object, they use mainly red color, which is clearly visible from afar in any weather.

Therefore, a stop signal or any other warning light is red, not green or blue.

Why does the sky turn red at sunset?

In the evening hours before sunset, the sun's rays fall on the surface of the earth at an angle, and not directly. They have to overcome a much thicker layer of the atmosphere than in daytime when the surface of the earth is illuminated by the direct rays of the sun.

At this time, the atmosphere acts as a color filter, which scatters the rays of almost the entire visible range, except for the red ones, which are the longest and therefore most resistant to interference. All other light waves are either scattered or absorbed by water vapor and dust particles present in the atmosphere.

The lower the sun drops in relation to the horizon, the thicker the layer of the atmosphere the light rays have to overcome. Therefore, their color is increasingly shifted towards the red part of the spectrum. This phenomenon is associated folk omen, saying that the red sunset portends strong wind the next day.


The wind originates in the high layers of the atmosphere and at a great distance from the observer. Oblique solar rays highlight the outlined zone of atmospheric radiation, in which there is much more dust and vapor than in a calm atmosphere. Therefore, before a windy day, we see a particularly red, bright sunset.

Why is the sky blue during the day?

Differences in the length of light waves also explain the pure blue of the daytime sky. When falling sun rays directly on the surface of the earth, the layer of the atmosphere they overcome has the smallest thickness.

Scattering of light waves occurs when they collide with gas molecules that make up air, and in this situation, the short-wavelength light range is the most stable, i.e. blue and purple light waves. On a fine windless day, the sky acquires amazing depth and blueness. But why do we then see blue and not purple sky?

The fact is that the cells of the human eye, which are responsible for color perception, perceive blue much better than purple. Yet purple is too close to the edge of the perceptual range.

That is why we see the sky as bright blue if there are no scattering components in the atmosphere, except for air molecules. When there's enough in the atmosphere a large number of dust - for example, in a hot summer in the city - the sky seems to fade, losing its bright blue.

Gray sky of bad weather

Now it is clear why the autumn bad weather and winter slush make the sky hopelessly gray. A large amount of water vapor in the atmosphere leads to the dispersion of all components of the white light beam without exception. Light rays are crushed in the smallest droplets and water molecules, losing their direction and mixing over the entire range of the spectrum.


Therefore, light rays reach the surface, as if passed through a giant diffuser. We perceive this phenomenon as a grayish-white color of the sky. As soon as moisture is removed from the atmosphere, the sky turns bright blue again.

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On a clear, sunny day, the sky looks bright blue.

In the evening, at sunset, the sky turns red, pink and orange.

Why the sky is blue? What turns the sunset red?

In answering these questions, we must study light and the earth's atmosphere.

Atmosphere

Also, in small amounts, there are other gases and small solid particles: dust particles, soot, pollen and salt from the ocean.
The composition of the atmosphere changes with location, weather, and other things.

For example, there may be more water in the air after a hurricane or near the ocean. Volcanoes can release large amounts of ash into the atmosphere. Pollution can add various gases and soot. The atmosphere is tightly pressed to the entire surface of the Earth. Gradually, it becomes thinner if you rise higher and higher. There is no clear boundary between the atmosphere and space.

light waves

Electromagnetic waves move in space at a speed close to 300,000 km/h. This is called the speed of light.

light color

Colors are constantly mixed into one. At one end of the spectrum are red and orange colors. They gradually turn into yellow, green, blue, blue and purple. Colors have different wavelength, frequency and energy. Purple with the shortest wavelength in the visible spectrum. This means that it has the highest frequency and energy.

With red, the opposite is true: the frequency and energy are the lowest, but the wavelength is the longest.

light in the air

Dust particles and water droplets are much larger than the wavelength of visible light. Light, colliding with these particles, is reflected and changes the trajectory of movement. Various colors light is reflected equally from the particles. The reflected light remains white, as it continues to contain all colors in a mixed form.

Gas molecules are much smaller than the wavelength of visible light. When light collides with them, anything can happen. For example, it can be absorbed by molecules. And then they will begin to radiate it, but in the other direction. All colors are absorbed, but blue makes it stronger than all other colors. This process is called "Rayleigh scattering" (after the English physicist Lord Rayleigh, who first discovered this phenomenon in 1870).

Why the sky is blue?

At the very horizon, the color of the sky is not so saturated, this is due to the fact that he has to go through a larger volume of air.

Black sky and white sun

Why is the sunset red?

Around the setting sun, the sky can take on different colors.

It looks especially spectacular when many small particles are suspended in the sky. They reflect light in different directions, and the sky turns red, orange and pink.