Why does the sky turn red at night?

We usually see that the sky is always blue during the day, but it turns red in the morning or at night, which is really wonderful. As we know, the earth is surrounded by a thick atmosphere. Although the air is transparent, it contains many tiny dust, ice crystals and water droplets. Sunlight can only reach the surface of the earth through this thick atmosphere.

Sunlight consists of red, orange, yellow, green, blue, indigo, purple and other colors. During the day, sunlight passes through the atmosphere, and the red light has the longest wavelength and the strongest transmission ability, and has been transmitted to the ground. The sunlight at dusk obliquely passes through the atmosphere, and the light travels much farther in the air than during the day. Easily dispersed blue light is scattered on the road far away from us, and almost no blue light can enter our eyes. But red light can travel far and enter our eyes through the atmosphere, so the sky we see is red.

Maybe you usually notice that the sun is red in the morning and evening. When there is a lot of dust in the air, the sun and lights are red. This is because blue is lost when passing through dust and water droplets, and only red light is reflected into our eyes.

We call this phenomenon that the sky is red in the morning and evening rosy clouds. In the morning, the sun rises in the east. If there is too much water vapor in the atmosphere, some short-wavelength blue light, blue light and purple light in sunlight are scattered by the atmosphere, only red light, orange light and yellow light penetrate the atmosphere, and the sky is dyed red and orange to form a sunrise.

The appearance of a bright red and golden sunset indicates that the weather in the upper reaches of our west has turned fine or the clouds have split, and the sunlight can penetrate to form a sunset glow, indicating that the rain clouds hanging over the local area are about to move eastward and the weather will turn fine.

sunset glow