Blue Sky

The blue color of the sky is a fascinating phenomenon explained by Rayleigh scattering. When sunlight enters Earth's atmosphere, it interacts with air molecules and tiny particles. These particles scatter shorter wavelengths of light (like blue and violet) more effectively than longer wavelengths (like red). Even though violet light is scattered even more than blue, our eyes are less sensitive to violet, and some of it gets absorbed in the upper atmosphere. Consequently, the sky predominantly appears blue to us during the day.

At sunrise and sunset, the sun’s light must travel through a much thicker layer of the atmosphere. In this longer path, most of the blue light is scattered away before reaching the observer's eyes. What remains are the longer wavelengths like red and orange, which gives these times of day their dramatic, warm hues (色調).

Microsoft Copilot and edited