Cotton Candy Skies: Sweeter than they may seem?
The lack of a sunset, is hopefully a result of a cloudy day or unfortunately a result of an extremely smoggy day, when there’s too many toxic chemicals in the atmosphere that all light rays are scattered and no colour reaches your eyes.
A sucker for sunsets? Join the club! During lockdown in the concrete jungle of Colombo, sunsets from my roof were one thing that I looked for the most. The pretty pinks and purples the sky turned into reminded me very much of cotton candy or bombaimuttai that we were devoid of at the time. Once lockdown was lifted for a short while and life almost went back to normal, I watched the sunset in Kandy once, the city with the highest level of air pollution in Sri Lanka, and the sky was ablaze!
Sunsets from any part of our island nation are bound to be beautiful. Either the sun paints the sky in shades of pink and purple, with hints of orange and yellow, looking like cotton candy — delicious, or the sky transforms from light blue and fluffy white to shades of fiery orange and fierce red — if Chicken Licken were around she’d scream “The sky is on fire!”
While cotton candy and fiery skies at dusk make for the perfect Instagram story, they might just be a tad bit sweeter than that.
According to the science of sunsets, the different colours that we see are a result of the different wavelengths of visible light — each wave length is viewed at a different colour. Colours like violet and indigo, that is on the inner end of a rainbow, have shorter wave lengths and the fiery reds and oranges, seen on the outer end, have longer wave lengths.
As these light waves travel through air, which is made up of its own molecules like oxygen and nitrogen, the shorter light beams are scattered, while the longer ones are not — this selective scattering is known as ‘Rayleigh scattering’. The sky is blue during the day time because the violet and blue waves are scattered the most — and the human eye is more sensitive to blue than violet. As the sun moves from East to West so does the distance between the Earth and the Sun — when the sun is setting (or rising) is when it is furthest away from Earth.
What does this mean for a sunset? There’s more atmosphere through which the light waves must travel. At noon the distance between the Earth and Sun is short — so we see more blue than orange, but when the sun sets the light waves have to travel a longer distance and experience more molecules in the atmosphere — causing further scattering of shorter waves — to reach our eyes and so we are more likely to see more orange than violet.
What makes it worse for cotton candy skies is air pollution. Smoke from vehicles, factories, households etc. in big cities add other molecules other than oxygen and nitrogen into the mix causing further scattering of light waves — this includes chlorofluorocarbons (greenhouse gases), hydrocarbons, sulfuric acid and lots of other unpleasant pollutants. (Julia Layton)
So here’s a key for assessing air pollution through sunsets:
The more pink, purple and cotton candy it looks — chances are the air is not too polluted that day.
The more red, orange and fiery it is — high possibility that the air is quite harmful.
The lack of a sunset, is hopefully a result of a cloudy day or unfortunately a result of an extremely smoggy day, when there’s too many toxic chemicals in the atmosphere that all light rays are scattered and no colour reaches your eyes.
Sources: Julia Layton https://science.howstuffworks.com/environmental/green-science/smog-sunset.htm
