Why is the sky blue?

What you need to know

Sunlight looks white because it contains many visible wavelengths. When it enters Earth’s atmosphere, molecules scatter the shorter wavelengths much more strongly than the longer red wavelengths. Blue light is therefore scattered across the sky and reaches your eyes from many directions. Violet is even shorter, but the Sun emits less of it, some is absorbed, and human vision is less sensitive to violet, so the sky appears blue rather than violet. At sunrise and sunset, sunlight travels through more atmosphere, scattering much of the blue light out of the direct path and leaving warmer reds and oranges.