The Science Behind the Blue Evening Sky: Why is it Blue Instead of Red/Orange?

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In summary, the color of the evening sky depends on the direction you are looking. When facing the setting sun, there is usually a hint of orange or red due to particles in the atmosphere. However, when looking up or away, the sky appears blue due to the scattering of blue light. It is important to be cautious when observing the color of the sky, as our perceptions can be influenced by context. This topic is often debated and there is a lot of misinformation, so it is important to fact check against basic theories.
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Fiona Rozario
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I know the question is generally "Why is the evening sky red/orange?" but actually the evening sky is very rarely red/orange. On most evenings it is blue. Why is it blue? Shouldn't it be red/orangish? Does the location on Earth have anything to do with this?
 
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It depends on which direction you are looking. Looking towards the setting Sun, you will always get at least a hint of orange / red, which is stronger when the atmosphere is full of scattering particles likedust or water droplets / thin clouds. The blue colour can be seen when you look up or away because there is still comparatively more blue light scattered downwards.
You need to be careful when assessing the colour of the sky (and many other things) because your observational powers are very much affected by context (we are very subjective about these things).
I always use the terms "reddish" and "bluish", to allow for this. This is one of those topics that are frequently discussed and there is a lot of misinformation flying around about it. Don't believe everything you read and check it all against basic theory. :smile:
 

1. Why does the sky appear blue in the evening?

The sky appears blue in the evening due to a phenomenon called Rayleigh scattering. This is when sunlight enters the Earth's atmosphere and gets scattered by the gas molecules in the air. Blue light has a shorter wavelength and is scattered more easily, making it the dominant color we see in the sky.

2. Does the color of the evening sky change depending on where you are on Earth?

Yes, the color of the evening sky can vary depending on your location on Earth. This is because the amount of gas molecules in the atmosphere can differ, causing the sunlight to scatter differently and creating variations in the color of the sky.

3. Can the weather affect the color of the evening sky?

Yes, weather conditions such as cloud cover and humidity can affect the color of the evening sky. On a cloudy day, the clouds can block and scatter the sunlight, causing the sky to appear less blue. Humidity can also affect the amount of water vapor in the air, which can impact the way sunlight is scattered and the color of the sky.

4. Why does the evening sky sometimes appear more purple or pink?

The evening sky can appear more purple or pink due to a phenomenon called scattering. During sunrise and sunset, the angle of the sun is lower, and the sunlight has to travel through more of the Earth's atmosphere. This causes the blue light to scatter more, making the sky appear more purple or pink.

5. Is there a specific time when the evening sky appears bluer?

The evening sky appears bluer when the sun is closer to the horizon. This is because the sunlight has to travel through more of the Earth's atmosphere before reaching our eyes, causing more scattering of the blue light and making the sky appear bluer. As the sun rises higher in the sky, the blue light is scattered less, and the sky may appear less blue.

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