what makes the sky blue

The sky appears blue because molecules in the Earth's atmosphere, mainly nitrogen and oxygen, scatter sunlight in all directions. This scattering is more effective at shorter wavelengths, which correspond to blue and violet light. Although violet light is scattered even more, our eyes are more sensitive to blue light, so the sky appears blue to us. This phenomenon is known as Rayleigh scattering. Additionally, the blue light scattered across the sky reaches our eyes from every direction, making the sky seem blue during the day.