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. 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 any point the globe 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. As sunlight reaches our atmosphere, the molecules in the air scatter the blue light, allowing the red 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.
This 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.
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We welcome the most inquisitive on the pages of our site! Today we will touch on a question that often worries inquisitive minds (especially children's), but not everyone finds an opportunity to figure out why is the sky blue because the air is actually transparent. Let's try to answer it briefly.
What does Wikipedia say?
If we don’t know something, then we can always find the answer in Wikipedia. So let's take a look there and see what this resource tells us.
As a matter of fact, here is a link to the relevant material.
Well said on Wikipedia! True, somehow it is not very clear. The only thing that can be sorted out is the fact that the sun's rays reach our atmosphere, something happens to them, and we see a blue sky. No, this will not work, let's try to understand in more detail and in a more understandable language why the sky is blue.
In fact, the reason for everything is such a thing as " light scattering»!
Light scattering
So, the Sun emits rays that are white. White, as you know, includes all the colors of the spectrum visible to us. Evidence of that - rainbow. It arises for the reason that sunlight, falling into water droplets, is refracted and breaks up into different colors. We also observe blue skies for a similar reason.
This is how a rainbow is formed You may be interested in:
The fact is that there are many gas molecules in the air, which scatter sunlight. Light particles scatter in different directions, so the blue color of the sky is visible to both earthlings and astronauts from the ISS in the form of a blue halo. But why is it blue, because there are at least seven colors in the spectrum, as they say: "Every hunter wants to know where the pheasant is sitting!".
Interesting fact! A person inhales about 20 kg of air per day. We get this volume by taking 22,000 breaths a day.
Why is the sky blue?
Each color has its own wavelength. In the following figure, you can see how this indicator varies.
Violet diffuses too much, and the colors from green to red, on the contrary, do not scatter very intensively. So it turns out, blue and blue particles are the golden mean. Violet, despite the fact that it scatters better than blue, we do not notice because of our perception: with the same brightness, blue is perceived by our eyes much better than its counterpart.
That's pretty much how it goes Here is a good video on this topic, which helped us to understand this issue.
On a clear sunny day, the sky above us has a bright blue color. In the evening, at sunset, the sky takes on a deep red color with numerous shades that is pleasing to the eye. So why is the sky blue during the day? What makes a sunset red? How does transparent air shimmer with blue and red hues at different times of the day?
I will present 2 answers here: the first one is more simplified for the general reader, the second one is more scientific and accurate. Choose for yourself which one you like.
1. Why is the sky blue and not green? Answer for dummies
Light from the sun or a lamp looks white, but white is actually a mixture of all 7 existing colors: red, orange, yellow, green, cyan, indigo, and violet (Figure 1). The sky (atmosphere) is filled with air. Air is a mixture of tiny gas molecules and small pieces of solid material such as dust. As sunlight travels through air, it collides with air particles. When a beam of light hits gas molecules, it can "bounce" in the other direction (scatter).
Some component colors of white light, such as red and orange, pass directly from the Sun into our eyes without scattering. But most blue rays "bounce" off air particles in all directions. Thus, the whole sky is literally pierced with blue rays. When you look up, some of this blue light reaches your eye and you see blue light from all over your head! Here, in fact, why the sky is blue!
Naturally, everything is simplified to the maximum, but below is a paragraph where the property of our beloved sky above our heads is more fundamentally described and the reasons that explain why the color of the sky is blue and not green after all!
2. Why is the sky blue? advanced answer
Let's take a closer look at the nature of light and color. Color, as everyone knows, is a property of light that our eyes and brain can perceive and define. Light from the sun is a large amount of white rays, which consist of all 7 colors of the rainbow. Light has the property of dispersion (Fig. 1). Everything is illuminated by the Sun, but some objects reflect rays of only one color, for example, blue, while other objects only reflect rays of yellow, etc. This is how a person defines colors. So, the Sun shines on the Earth with its white rays, but the atmosphere (a thick layer of air) envelops it, and when this white (consisting of all colors) ray passes through the atmosphere, it is the air that scatters (spreads) all 7 colored rays of the white sun ray, but with greater force, it is its blue-blue rays (in other words, the atmosphere literally begins to glow blue). Other colors directly fall from the Sun into our eyes (Fig. 2).
Why is blue the color most diffused in the atmosphere? This is a natural phenomenon, and it is described physical law Rayleigh. To put it more simply, there is a formula that Rayleigh derived in 1871, and which determines how the scattering of light (a beam) depends on the color of this beam (that is, on such a property of the beam as its wavelength). And it just so happened that the sky-blue color has the shortest wavelength and, accordingly, the greatest dispersion.
Why is the sky red during sunrise and sunset? At sunset or sunrise, the sun is low on the horizon, which causes the sun's rays to fall obliquely
yut to Earth. The beam length, of course, increases many times (Fig. 3), and therefore, at such a huge distance, almost the entire short-wavelength (blue-blue) part of the spectrum is scattered in the atmosphere and does not reach the Earth's surface. Only long waves, yellow-red, reach us. This is exactly the color the sky takes on during sunrise and sunset. That is why the sky, in addition to blue and blue, is also yellow and red!
And now, for a complete understanding of all of the above, a few words about what the atmosphere is like.
What is the atmosphere (vault of heaven)?
The atmosphere is a mixture of gas molecules and other materials that surround the Earth. Basically, the atmosphere consists of nitrogen gases (78%) and oxygen (21%). Gases and water (in the form of vapours, droplets and ice crystals) are the most common constituent parts atmosphere. There are also small amounts of other gases, as well as many fine particulate matter such as dust, soot, ash, salt from the oceans, etc. The composition of the atmosphere changes with geographical location, the weather and much more. Somewhere there may be more water in the air after a rainstorm or near the ocean, somewhere volcanoes erupt large amounts of dust particles high into the atmosphere.
The atmosphere is denser in its lower part, near the Earth. It gradually thins out with height. There is no sharp gap between atmosphere and space. That is why we see overflows of blue and blue in the sky, precisely because the atmosphere in the sky is different everywhere, has different structure and properties.
We are all used 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 change does not occupy the minds of most adults, which cannot be said about children. They are constantly wondering why the sky is blue in terms of physics or what turns the sunset red. Let's try to understand these not the most simple questions.
changeable
It is worth starting with the answer to the question of what, in fact, the sky is. AT ancient world it was really seen as a dome covering the Earth. Today, however, hardly anyone does not know that, no matter how high a curious explorer rises, he will not be able to reach this dome. The sky is not a thing, but rather a panorama that opens 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 what has risen above the clouds, a completely different view opens up than from the earth at this time.
A clear sky is blue, but as soon as clouds run in, it becomes gray, leaden or off-white. The night sky is black, sometimes you can see reddish areas on it. This is a reflection of the artificial lighting of the city. The reason for all such changes is light and its interaction with air and particles of various substances in it.
The nature of color
In order to answer the question of why the sky is blue from the point of view of physics, you need to remember what color is. This is a wave of a certain length. The light coming from the Sun to the Earth is seen as white. Even from Newton's experiments, it is known what a beam of seven rays is: 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 a short wavelength. The decomposition of light into a spectrum occurs when it collides with molecules of various substances, while 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 have sought to discover a phenomenon or process that scatters light in the planet's atmosphere in such a way that only blue reaches us as a result. The first candidates for the role of such particles were waters. It was believed that they absorb red light and transmit blue, and as a result we see the sky of blue color. The subsequent calculations, however, showed that the amount of ozone, ice crystals and water vapor molecules that is in the atmosphere is not enough to give the sky a blue color.
Reason for pollution
At the next stage of research, John Tyndall suggested that the role of the desired particles is played by dust. Blue light has the greatest resistance to scattering, and therefore is able to pass through all layers of dust and other suspended particles. Tyndall conducted an experiment that confirmed his assumption. He created a model of smog in the laboratory and illuminated it with bright white light. Smog took on a blue tint. The scientist made an unambiguous conclusion from his study: the color of the sky is determined by dust particles, that is, if the Earth's air was clean, then not blue, but white skies shone over people's heads.
Lord's study
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 paints the space above our heads in a shade familiar to us. It's in the air itself. Gas molecules absorb the largest, and primarily the longest, wavelengths equivalent to red. The blue dissipates. This is exactly what today explains what color the sky we see in clear weather.
The attentive will notice that, following the logic of scientists, the dome overhead should be purple, since it is this color that has the shortest wavelength in the visible range. However, this is not a mistake: the proportion of violet in the spectrum is much less than blue, and the human eye is more sensitive to the latter. In fact, the blue we see is the result of mixing blue with purple and some other colors.
sunsets and clouds
Everyone knows that at different times of the day you can see a different color of the sky. Photos of the most beautiful sunsets over the sea or lake are a great illustration of this. All sorts 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 overcome a much longer path through the atmosphere than at the height of the day. In this case, the light of the blue-green part of the spectrum is scattered in different directions and the clouds located near the horizon line become colored in shades of red.
When clouds cover the sky, the picture changes completely. unable to overcome the dense layer, and most of them 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 when impressive clouds cover the sky, absorbing part of the rays for the second time.
Other skies
Interestingly, on other planets solar system when viewed from the surface, one can see the sky, very different from the earth. On the space objects deprived of the atmosphere, the sun's rays freely reach the surface. As a result, the sky here is black, without any hue whatsoever. Such a 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, which is saturated with the atmosphere of the planet. It is painted in different shades of red and orange. When the Sun rises above the horizon, the Martian sky becomes pinkish-red, while the part of it immediately surrounding the disk of the star appears blue or even purple.
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 the 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.
The study of the daytime space overhead reveals no less wonders than the study of 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 off the bat.
Despite scientific progress and free access to many sources of information, a 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. 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 the longer light waves 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 on blue sky White clouds? 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.