What color is the sky? Why is the sky blue in terms of physics?

We are all used to the fact that the color of the sky is a non-permanent characteristic. Fog, clouds, time of day - everything affects the color of the dome overhead. Its daily shift does not take the minds of most adults, which can not be said of children. They are constantly interested in why the sky is blue in terms of physics or what colors the sunset in red. Let's try to understand these not very simple questions.

Changeable

It begins with an answer to the question about what the sky itself is. In the ancient world, it really looked like a dome covering the Earth. Today, however, hardly anyone does not know that, no matter how high a curious researcher is raised, 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 visibility woven from the light. And if you observe from different points, it can look different. So, from the porthole of the plane, which rose above the clouds, a completely different view opens up than from the ground at this time.

The clear sky is blue, but it is worthwhile to run to the clouds - and it becomes gray, leaden or dirty-white. The night sky is black, sometimes you can see reddish patches on it. This is a reflection of artificial illumination of the city. The reason for all such changes is light and its interaction with air and particles of various substances in it.

Nature of color

In order to answer the question of why the sky is blue in terms of physics, we need to remember what color is. It is a wave of a certain length. The light coming from the Sun to the Earth is seen as white. Even with Newton's experiments, it is known that white light is a beam of seven rays: red, orange, yellow, green, blue, blue and violet. Colors differ in wavelength. The red-orange spectrum includes the waves most impressive in this parameter. The colors of the blue-green part 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 scattered.

Study of the cause

Many scientists have tried to explain why the sky is blue, in terms of physics. All researchers sought to discover a phenomenon or process that in the atmosphere of the planet disperses light in such a way that as a result only the blue reaches us. The first candidates for the role of such particles were molecules of ozone and water. It was believed that they absorb red light and let the blue pass, and as a result we see the sky blue. 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 make the sky blue.

The reason for the contamination

At the next stage of research by John Tyndall, it was suggested that the role of the particles sought is played by dust. Blue light has the greatest resistance to dispersion, 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 smog model in the laboratory and lit it with a bright white light. Smog acquired a blue tinge. The scientist made an unambiguous conclusion from his research: the color of the sky is determined by particles of dust, that is, if the air of the Earth was clean, then over the heads of people shone not blue, but white heavens.

The study of the lord

The final point in the question of why the sky is blue (in terms of physics), put the English scientist, Lord D. Rayleigh. He proved that it is not dust or smog that stains the space above his head in a habitual for us shade. It's in the air itself. Gas molecules absorb most of the light and, in the first place, the longest wavelengths, equivalent to red. Blue at the same time dissipates. This is precisely how today we see the color of the sky in clear weather.

Attentive will notice that, following the logic of scientists, the dome overhead should be purple, because this color has the shortest wavelength in the visible range. However, this is not an error: the proportion of violet in the spectrum is much less than blue, and the human eyes are 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 the different colors of the sky. A photo of beautiful sunsets over the sea or a lake is a perfect illustration of this. All sorts of shades of red and yellow in combination with blue and dark blue make this spectacle unforgettable. And it is explained by the same dispersion of light. The fact is that during sunset and dawn, the sun's rays have to overcome a much larger 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 the sky clouds, the picture changes completely. The sun's rays can not 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 light. As a result of all these transformations, white light reaches the earth, if the clouds are small in size, and gray, when the sky closes the imposing clouds, reabsorbing a part of the rays.

Other skies

It is interesting that on other planets of the solar system, when viewed from the surface, one can see the sky, which is very different from the terrestrial one. On space objects, deprived of the atmosphere, the sun's rays freely reach the surface. As a result, the sky here is black, without any shade. 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 its portion, directly surrounding the disk of the star, is seen as blue or even purple.

The sky above Saturn is the same color as on Earth. Above Uranus are aquamarine skies. The reason lies in the methane haze, located in the upper atmosphere of the planet.

Venus from the eyes of researchers hides a dense layer of clouds. He does not allow to reach the surface of the planet with the rays of the blue-green spectrum, so the sky here is yellow-orange with a gray strip along the horizon.

The study of the daytime space above the head reveals no less miracles than the study of the starry sky. Understanding the processes that take place in the clouds and behind them helps to comprehend the reason for the rather common things for the layman, which, nevertheless, can not be explained on the move by far not everyone.