Eastward Journey Popular Science｜Interesting Understanding of Earth's Atmosphere
The reason why we living on the surface of the earth can be free from cosmic rays and solar radiation depends entirely on the protective shield of the earth's atmosphere.
In addition to protecting us, the earth's atmosphere also provides us with oxygen. However, the atmosphere is not only composed of oxygen, but also various inert gases such as nitrogen, carbon dioxide, argon, and helium. Although oxygen allows us to Breathing, but carbon dioxide, water vapor and other gases are also important. Nitrogen alone accounts for 78% of the composition of the atmosphere, and oxygen is only about one-fifth. Their combination makes up the entire atmosphere.
The earth is surrounded by the atmosphere, which can be divided into four parts from bottom to top, namely the troposphere, stratosphere, mesosphere and ionosphere. Beyond that is the extremely thin outer space.
The troposphere is the layer where we humans live. Its height is below about 12 kilometers. The atmosphere here is relatively active. Hot and cold air are constantly convection. The hot air goes up and the cold air goes down, forming a Different weather climates and various winds.
The stratosphere is special. It is located above the troposphere 50 kilometers below. It is hot in the upper layer and cold in the lower layer. The air flows flat, which is also the origin of its name.
The mesosphere refers to the area below 80 kilometers above the stratosphere. It is characterized by extremely active convection, which is stronger than the troposphere. Because the temperature in this area changes greatly with altitude, which also increases Increases the up and down flow of hot and cold air.
The ionosphere refers to the area outside the mesosphere. In fact, part of the atmosphere in the mesosphere is already in an ionized state. Because it is outside the atmosphere, the ionosphere receives the strongest ultraviolet rays and cosmic rays from the sun, causing the atmosphere to Molecules are ionized, forming an ionosphere.
After talking about the distribution of the atmosphere, let’s briefly explain why the sky is blue. Theoretically, the light from the sun shining on the earth is white. It is a collection of light of various colors. But after The earth's atmosphere turned blue, why?
The principle is very simple, it is the scattering of light. As for why it is blue, we have to talk about the wavelengths of different lights. From red, orange, yellow, blue to purple, the wavelengths gradually become shorter. , the frequency gradually increases
According to the principle of Rayleigh scattering, the scattering intensity of light is related to the wavelength of the light and the size of the object causing the scattering. Simply put, the size of the tiny particles in the air exactly matches the wavelength of the blue light. , resulting in the scattering intensity of blue light being about ten times that of red light and other lights when light travels through the atmosphere
In other words, the blue part of the white light is weakened by scattering, so we see the sun appear a little brighter Red, and the blue light scattered in the atmosphere around the sun becomes the "blue sky" in our eyes.