The phenomenon of the sky turning red during sunset is primarily due to the scattering of sunlight by the Earth’s atmosphere. To understand this, we need to consider the way light interacts with particles in the atmosphere.
The Earth’s atmosphere contains various particles such as molecules, tiny water droplets, and dust particles. These particles can scatter sunlight in different ways depending on the size of the particles and the wavelength of the light. Sunlight consists of different colors or wavelengths, ranging from shorter blue and green wavelengths to longer red and orange wavelengths.
During sunset, the sun is lower in the sky, and the sunlight has to pass through a larger portion of the Earth’s atmosphere before reaching our eyes. As sunlight travels through the atmosphere, it encounters more air molecules and particles compared to when the sun is directly overhead.
The shorter blue and green wavelengths of light are scattered more easily by the molecules and smaller particles in the atmosphere through a process called Rayleigh scattering. This scattering causes the blue and green light to scatter in different directions, making the sky appear blue during the daytime when the sun is higher in the sky.
However, during sunset, when sunlight has to pass through a larger portion of the atmosphere, the shorter blue and green wavelengths get scattered out of our line of sight more effectively. This scattering reduces the amount of blue and green light reaching our eyes, making the sky appear red or orange.
In addition to Rayleigh scattering, another type of scattering called Mie scattering plays a role in the color of the sunset. Mie scattering occurs when sunlight interacts with larger particles, such as dust, pollutants, or water droplets in the atmosphere. These larger particles can scatter all colors of light, but they tend to scatter shorter blue and green wavelengths more efficiently than longer red wavelengths.
Therefore, during a sunset, the remaining sunlight reaching our eyes is enriched with longer red and orange wavelengths because the shorter blue and green wavelengths have been scattered out of our line of sight. This causes the sky to appear red or orange, and it often creates a beautiful and vibrant display of colors during sunset.
It’s worth noting that atmospheric conditions, such as the presence of pollution, dust, or other particles, can influence the intensity and range of colors observed during a sunset. Additionally, the precise colors and their variations can also be influenced by factors like cloud cover, humidity, and the overall composition of the atmosphere at a given location.