The sky appears blue because of a phenomenon called Rayleigh scattering. When the sun’s light enters the Earth’s atmosphere, it encounters various molecules such as oxygen and nitrogen. These molecules scatter the sunlight in all directions. However, the shorter blue wavelengths of light are scattered more than the longer red wavelengths of light. This is because the blue light has a shorter wavelength and interacts more with the molecules in the atmosphere. As a result, when we look up at the sky during the day, we see more blue light scattered in our direction, which makes the sky appear blue.