Why are sunsets so many colors if the sun is white?
In: Planetary Science
Have you wondered why rainbows are so many colours if the sun is white? How leaves look green and mud brown and where any colours come from, if the sun is white?
[Rainbow colours](https://education.nationalgeographic.org/resource/rainbow/) (pic) (red, orange, yellow, green, blue, indigo, violet, and all the shades in between) don’t have black or white or brown among them. When we see all those ‘real’ colours together, that looks white to us. The sun shines all the colours. If we see no light, that’s black.
Leaves reflect just the green bit, they absorb the rest, so we see them as green.
Mud reflects several colours – orangey, yellowy, reddy parts of the rainbow – and not very brightly – which we see as browns.
Seen from space, [Earth has a very thin atmosphere](https://assets.wired.com/photos/w_2400/wp-content/uploads/2014/12/2014bluemarble_2014089_lrg.jpg) (pic) so when it’s midday and the Sun is overhead, light is coming straight down through a little bit of air to get to you.
When [it’s sunset time](https://www.reddit.com/media?url=https%3A%2F%2Fpreview.redd.it%2F65llnn0pvdh71.jpg%3Fauto%3Dwebp%26s%3D1c5abb4320ce46174b7a66bb8cd2843a30537037) (pic), the light is coming ‘sideways’ through many miles and miles of air to get to you.
The sun from space is a white dot surrounded by black; it’s air which looks blue and that’s because it has lots of stuff in it – water droplets, clouds, dust, gasses – and they all mess up the straight lines of the sun’s light and curve it around and throw it all over the place – like a golf ball catching on the edge of the hole and curving round and going off again at a different angle, happening zillions of times on light rays in the air. It’s [Rayleigh Scattering](https://en.wikipedia.org/wiki/Rayleigh_scattering) (Wikipedia) and it works more on the bluer end of the rainbow colours than on the redder end.
During the day with the sun overhead, the thin air is enough to curve the blue throwing lots of it sideways to our eyes, red tends to go straight on down and not hit enough air to get curved, meaning it goes down and we don’t see much of it. Making the sky look more blue. But at sunset when the light is coming sideways through a lot of air, there’s a lot more curving, and a lot more of the sun’s light gets scattered – the blue gets thrown about so much that lots of it goes up and away, and the reds and oranges and yellow now pass enough dust and water drops that they do get curved and light up the sky in those colours.
The sun gives white light, which is all colours of light mixed together. When you shine sunlight through a prism, you get a rainbow, because the various wavelengths that make up white light refract by different amounts.
During the day, the sky appears blue because that’s the colour that gets scattered the most by the earth’s atmosphere. But when the sun is close to setting, the blue light gets scattered away from our eyes, and that way we can see the longer wavelengths like yellow and red.
The sun is white, which means it contains all colours. If the sun only contained blue colors it would be blue, if it contained only blue and red it would be purple, as that is a mix of blue and red.
This means that you can change the color of light by removing some of the colors in that light. For example, if we had a purple light but removed all the red from it, it would look blue.
The atmosphere works sort of like a filter for the light. When the white light hits the atmosphere, the atmosphere will mostly let the blue light through while the other colors are stopped, so we only see the blue light making the sky blue.
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