Express.co.uk has been working with the team at Google, who helped us discover the most-searched science questions on Google in 2019. One of the most asked is ‘why is the sky blue?’. In short, the sky is blue during the daytime because when light from the Sun reaches our atmosphere, it is scattered by particles and gasses of nitrogen and oxygen. It is important to remember although the Sun looks white and yellow, it is actually made up of a plethora of colours – as is made evident during a rainbow when water droplets disperses the light.
But the reason the sky is permanently blue is that the blue wavelength moves in shorter waves than the other colours from the Sun.
Shorter wavelengths, such as blue, are scattered more than the longer wavelengths – with red being the longest – which is why blue dominates the sky.
NASA’s website said: “Sunlight reaches Earth’s atmosphere and is scattered in all directions by all the gases and particles in the air.
“Blue light is scattered in all directions by the tiny molecules of air in Earth’s atmosphere. Blue is scattered more than other colours because it travels as shorter, smaller waves.
However, the longest wavelength which comes from the Sun is actually violet.
The reason the sky looks blue rather than violet is because the human eye is much more sensitive to the former, meaning it is what we detect.
You may notice that the sky sometimes looks red during sunset, but this is because the light from the sun is being bent when it passes through the Earth’s atmosphere.
This bizarre effect is known as ‘Rayleigh scattering’, which filters out bands of green and violet – which blue is positioned in between in the spectrum – light in the atmosphere, leaving just a red glow.