Space questions, answered
Why is the sky blue?
Because air scatters the Sun's blue light more than its red light. Sunlight hits the molecules in our atmosphere, and the shorter, bluer wavelengths bounce around the sky in every direction — so that's the colour we see overhead.
This is called Rayleigh scattering: smaller wavelengths (blue and violet) scatter far more than longer ones (red and orange). Our eyes are more sensitive to blue than violet, and some violet is absorbed high up, so the sky reads as blue.
At sunrise and sunset the light travels through much more air, scattering the blue away entirely and leaving the reds and oranges — which is why the sky turns fiery at the horizon.
People also ask
Why are sunsets red?
Near the horizon, sunlight passes through more atmosphere, which scatters out the blue and leaves the longer red and orange wavelengths.
Sources: NASA — why is the sky blue