rames to Greg, Cassie, Karen, Sofia, Tommy on 9 Nov 2013. This question was also asked by asommer, jrourke.
Thomas Doherty-Bone answered on 9 Nov 2013:
Is it really blue? or is that the colour that our visual system picks up above others? An animal without colour vision (like a dog) or different sensitivity to the spectrum of light (maybe a pigeon) might see the sky differently. Right now I see the sky is grey – lots of puffy clouds packed together!!!
We are bombarded by all sorts of electromagnetic rays, the minute spectrum we can see, the visual spectrum is red-orange-yellow-green-blue-indigo-violate (or “Richard Of York Gave Battle In Vain” as a reminder). We don’t see radio waves, gamma rays, ultraviolet rays, etc. So why do we see blue when the clouds are gone and the sun is shining?
I’ve had a peek at NASA’s web page, and their explanation is that because blue light waves are smaller than the other colours, its the one that is less refracted (scattered) by the Earth’s atmosphere.
And I don’t know why clouds are puffy and I am not sure if cloud scientists know either. But yes, there are cloud scientists out there. Puffy clouds are called cumulus clouds.
Cassandra Raby answered on 9 Nov 2013:
So light from the sun is white – and white light is actually all the colours of light combined (like if you squished the different colours of light from a rainbow it would be white). But the reason why the colours of a rainbow are seperate is because each colour of light is wavy, but they all have different types of waves.
Now blue has the shortest of all the waves, so when the sun light reaches the air around earth it is the one that is most affected! The blue light hits all the particles in the air and that makes it bounce everywhere!
So clouds look puffy… but the closer you get to them the less puffy they look. Have you ever walked through a mist? That’s what clouds are – a lot of water droplets in the air. All these water droplets collect together when air has pushed them into the sky – and so you get areas where the droplets are which are how clouds, and patches where there aren’t any… and it causes the cloud to have a puffy look to them.
Karen Bacon answered on 11 Nov 2013:
The sky usually appears blue (but not always – think of sunrise and sunset on a clear day) to us because when the visible light emitted by the sun reaches Earth it is scattered by the molecules in our atmosphere. Blue light has the shortest wavelength of all visible light and as a result it is spread around the most by the air particles in the atmosphere. That is why the sky appears blue most of the time.
Clouds are made up of water molecules, sometimes in the form of ice crystals. When sunlight hits the water molecules, the light is scattered evenly, making the clouds appear white. The puffy texture of cumulus clouds is because the water molecules are loosely packed in the cloud and they spread out laterally (length wise, not height wise). The loose packing of the water molecules allows the clouds to appear puffy. These clouds are sometimes called “fair weather clouds” because they seldom bring rain, once again because they do not have tightly packed water molecules. Their life-time is usually between 5 and 40 minutes.