ASK THE METEOROLOGIST – THE SKY
“What is the sky?”
The sky is a mixture of gases and the two predominant gases are Nitrogen and Oxygen. Nitrogen (N2) makes up 78% of the atmosphere and Oxygen(O2) represents 21% while the remaining 1% are trace gases, Argon gas and water make up the majority of the remaining gases. The sky appears blue due to what’s called Rayleigh scattering. As sunlight passes through the atmosphere most of the longer wavelengths pass straight through like red, orange and yellow. Shorter wavelengths, like blue absorbs the light and thus that’s what we see. The absorbed blue light is radiated in different directions all across the sky and that’s why the sky looks blue. At sunset the sun is lower to the horizon and has to pass through more of the atmosphere so more of the shorter wavelengths are absorbed and thus we see red and orange at sunset.