The sky appears blue to our eyes because of a phenomenon called Rayleigh scattering. When sunlight reaches the Earth's atmosphere, it is made up of many different colors of light, including red, orange, yellow, green, blue, indigo, and violet. When these colors of light encounter the tiny molecules and particles in the Earth's atmosphere, they scatter in all directions. Blue light has a shorter wavelength and higher frequency than the other colors of light, so it scatters more easily. This means that when we look up at the sky, we see more blue light scattered in our direction. That's why we see the sky as blue.