y'all imma have to start unfollowing people who reblog that do you love the colour of the sky post like there is a rEASON we started making memes about it in the first place its because it was boring and annoying to scroll past and guess what? it still is those exact things
Why are the clouds of different colours? or better worded, why does the sunset displays different colours? what causes all the colours in the sky?
Hello, sorry this is so late! I’ve been far too busy lately. Keep your science questions coming, but I’ll be a long time in answering them!
Blue sky - when the Sun is high up in a clear sky
Light from the Sun is white - a mixture of all the different colours of the rainbow blended together, that can be separated out with a prism or a raindrop. Air molecules scatter sunlight around, spreading it all over the sky and making the whole sky glow. (This is why the daytime sky is dark on the Moon - there’s no air to scatter the light, spread it around and make the sky glow). Blue light is scattered the most, making the sky glow blue. By contrast, more red, orange, yellow and green light aren’t scattered as much, meaning when we look straight up at the Sun it contains more of these colours and less of the blue - that’s why the Sun looks yellow, even though it’s white.
Red sky - around the Sun at sunset and sunrise
During a sunset, we’re looking at the Sun through more air than when it’s high up in the sky. As the sunlight passes through that extra air, so much blue light gets scattered out of it (and enough green and yellow light as well) to make the Sun and sky around it look orange-red.
Clouds around the sky will also reflect the light from the setting sun, making them look red too. The rest of the sky looks dark blue, because as the sun sets there’s less and less light from it, until it fades to black as night approaches (or turns to bright blue as the Sun rises.)
Clouds are made of tiny droplets of water that scatter sunlight, much like the sky does. However, while air molecules prefer to scatter blue light over other colours, water droplets will scatter all colours equally. Since sunlight is white, that means clouds will scatter all of that white sunlight, spread it throughout the cloud and give it a lovely fluffy white colour.
The tops of all clouds are white (unless it’s sunrise or sunset, in which case they can be red because the light illuminating them is red). If you’ve ever been in an aeroplane you’ll have seen this - all the clouds look uniformly white from above! (It’s the same in photos of Earth from space - all the clouds look white, except for a few on the day/night boundary.)
However, deep rain clouds with lots of water droplets scatter so much light around that not much light ends up penetrating all the way to the cloud base. That means deep, tall clouds get darker as you go further down. Looking at their base from underground, some deep rainclouds packed densely with water droplets can be light grey, dark grey or even almost black in a storm.
Other cloud colours
Sometimes, very distant clouds can look yellow for the same reason the Sun looks yellow - we’re looking at them through a lot of air, so some of the blue light gets scattered out from them, leaving the clouds with a yellowish tint.
The sky can also turn other colours because of impurities - soot and smoke particles and other chemicals - that scatter light differently from the normal air molecules in the sky or water droplets in clouds. After big volcanic eruptions ash and soot in the sky can produce different coloured skies - the eruption of Krakatoa in 1883 produced some unusually vivid red, orange and pink sunsets, and darker blue days, thanks to volcanic ash in the air around the globe.
Auroras are another phenomenon that can cause vivid colours in the sky, as charged particles from the Sun are channelled by Earth’s magnetic field to strike the air near the poles, excite electrons in the air molecules, and create shimmering curtains of light. The colours come from electrons in different molecules in the air becoming excited in different ways - yellow and green come from oxygen, red and purple come from nitrogen molecules in the lower atmosphere, and blue comes from nitrogen atoms in the upper atmosphere, with traces of other colours from rarer elements.
Rainbows of course are another colour phenomenon in the sky, along with related phenomena like sun dogs, haloes and so on. Go to that link to find out more about them!
Finally, the sky on other planets looks different because of the different substances in the air. As mentioned before on Mercury or the Moon the daytime sky would be black because the Sun’s light wouldn’t be scattered and spread over the sky by air. Venus’ clouds look yellowish because they’re laced with sulphuric acid, and the surface is bathed in a yellow glow because of it.
Mars’ skies can sometimes be dark blue, but they’re usually pinkish-red because of tiny particles of red dust suspended in the air from frequent dust storms. Mars’ air is a lot thinner than ours, so at sunset the sunlight doesn’t pass through enough air to scatter lots of blue light out of it and create a red sunset like it would on Earth - but it does scatter enough blue light to make the region around the Sun glow blue, even if the sky is filled with red dust. That means Martian sunsets are the opposite of ours - a red sky with blue sunsets!
(Photograph of a sunset on Mars, from NASA. Notice how most of the sky is red while the setting Sun is blue! Source)
Jupiter’s clouds have all kinds of different chemicals in them, making them white, grey, red, brown, orange, pink, yellow, beige, sometimes blue… all kinds of colours, that change every day with Jupiter’s weather! We don’t yet know the chemicals responsible for all of these colours - we still don’t for example know why the famous Great Red Spot is red. Saturn’s atmosphere is covered with a butterscotch-coloured haze, while its largest moon Titan has a thick atmosphere covered in orange smog made up of particles of organic haze. Uranus and Neptune have high levels of gaseous methane in their atmospheres together with hazes and clouds of liquid and solid methane droplets. This methane absorbs red light and scatters green and blue light, giving these planets a blue-green, sea-coloured sky (hence Neptune’s name!). And finally Pluto’s atmosphere is mostly nitrogen, like Earth, so its sky is a familiar, Earth-like blue - albeit very dark and only really visibly glowing at sunset or sunrise, when the sunlight has a lot of air to go through.
(Image taken by NASA’s New Horizons probe. Pluto’s atmosphere is thinner than ours, so sunsets and sunrises on Pluto would look blue for the same reason Mars’ do. Also, the sunlight is much weaker here! Image source)
Check out this link for more information on extraterrestrial skies!
So hopefully you now know why the daytime sky is blue, why sunsets are red, why clouds are white and sometimes grey, how auroras, pollution and volcanic activity can create other colours, and what colour the sky is on other worlds. There’s an infamous Tumblr meme - “do you love the colour of the sky? Which one?” and it’s implied that means “which colour?”. But after finding out about the sky on other worlds, you might want to ask “which sky?”