What is The sky?
The sky is defined as what corresponds to the surface of the earth upward, and thus it has included many parts of the universe, but it can be clearly defined as the area that corresponds to the surface of the earth, from the sea level to a height of 100 km, a region called the Carmen Line, a border that separates the sky and space, So that the boundary is in one of the atmosphere’s layers.
Why is the sky blue?
Gases and molecules around the globe surround the problem of the atmosphere, or what is known as the sky, especially nitrogen and oxygen gases, and those gases are known to be invisible, but when the sun’s rays penetrate the atmosphere, they are exposed to the gas molecules that constitute it, and therefore these molecules analyze the white light that contains what It is called the colors of the spectrum of different wavelengths, and then these gases absorb the wavelengths of colors such as red and green except for those that are blue and which they reflect only, which gives that blue to the sky.
The atmosphere extends from the Earth’s surface up to space in the form of layers, each of which has certain characteristics, and therefore the sky joins the atmosphere, but only to certain layers, and the most important layers of the atmosphere that represent the sky are the following: –
The Troposphere is the first layer of the atmosphere that extends from the surface of the land to a height of 10 km and is the layer in which climate changes occur and touches the surface of the earth directly, and therefore living organisms live in this layer.
The stratosphere is considered the second layer of the atmosphere and extends up to 50 km above the surface of the earth. This layer contains the so-called ozone layer that absorbs ultraviolet light from the sun’s rays, and is characterized by high temperatures with increasing altitude.
The mesosphere is located directly above the stratosphere, so that its distance from the Earth reaches 85 km, and it has only about 1% of the atmospheric pressure on the surface of the sea. .
After that the layers of the atmosphere are considered from within the outer space, so that there are three other layers, which are the thermosphere, the exosphere, and the enosphere, which reach a height of 190 km above the surface of the earth.These layers are distinguished by properties that differ from those of the atmosphere, known as the sky of the earth, so that they possess radiative, ionic properties and zero gravity.
Sky color and lighting
White sunlight consists of a mixture of several colors, and sunlight appears to us tilted to yellow, because yellow photons are predominant with the presence of red, green, blue and purple photons, but they are below the level of seeing the human eye. The interaction between sunlight and air shows us some familiar scenes in our daily life. In addition to other rare beautiful scenery.
Among the familiar scenes is the distinctive blue sky color, which varies from the dark color that we see during the day in the middle of the sky above our heads when we are on the tops of the mountains, to the multiple colors that result from scattering light, and the crowd compositions of the atmosphere’s atmosphere are compared in size with the visible wavelength . Under this condition, the atmospheric particles change the direction of the movement of the solar photons when they collide with them. The wave; the red and yellow light of sunlight passes through the air in a very large percentage, while photons of blue and violet are subjected to dispersal in the atmosphere and reach the surface of the earth from many other directions of the atmosphere. Violet light indulges in blue color, so blue photons are predominant in sunlight, and the eye is more sensitive to long wavelengths, so we see the color of the sky blue, and the degree of blue changes according to the direction of looking at the sky, so the blue color is light towards the horizon due to the increase in thickness Atmosphere. The color of the sky above our heads when viewed from mountain peaks or airplanes is close to the color purple. Moonlight causes the same effects when the sky is clear and the moon is full, so the color of the sky becomes dark blue.