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Cloud Week: What Makes The Sky Blue?
November 3, 2020 at 06:26 PM EST
By WeatherBug's Chris Sayles
Have you ever wondered why the sky portrays that baby blue color on a picture-perfect day? Well, there’s a few scientific facts that will help clear up this mystery.
The Million Dollar Question: Why Is the Sky Blue?
Short answer: the sky isn’t really blue; in fact, the sky has no color at all. Researchers have found that the blue color that we see on a clear day is based off how sunlight “scatters” through our atmosphere. Think of a prism and how it is made of glass and when light travels through the prism, colors of the rainbow radiate from it. This is how to think of the sky, a thin prism layer that when white light from the sun beams through it we see the bluish color as a result.
Okay, but why Blue? Why Not Purple?
Great question! If you recall that useful acronym from grade school that outlined the colors of the rainbow, ROY G. BIV, you’ll remember that certain colors react to light differently than others. For example, red, orange and yellow have lower energy levels than blue, indigo and violet. Meaning that when sunlight passes through our atmospheric prism, red, orange and yellow will scatter the least.
The result is similar on the other side of the coin; colors such as blue, indigo and violet scatter the most, which is why we see these colors more predominately. This scattering is known as Rayleigh scattering, named after Lord Rayleigh, and means that as the white light from the sun shines through our atmospheric prism, molecular collisions by atoms take place. So, long answer short? The sky is technically indigo and violet too, but because these colors have so much energy it is mainly kept at near the top of the atmosphere where we can’t see them unless we’re piloting a spacecraft.
What About the Colorful Sunsets and Sunrises?
These are amazing to gawk at after a long day of work or school, but there’s a little secret that may make one rethink this “breath of fresh air.” Remember how we mentioned that light is scattered through our atmosphere, radiating that beautiful blue color we see? Well, the same is still true at the end and beginning of the day as well. It’s just that there may be more at work here.
There’s an old meteorological saying that pirates used in the Northern Hemisphere when deciding to venture out at sea: “Red sky at night, sailor’s delight!” and “Red sky in the morning, sailor’s take warning!” Both sayings depict what happens when there is enough “stuff” in the atmosphere that sunlight has to “scatter” through, giving off a reddish hue in the sky. Now based off of pollution in the atmosphere or how much dust particles are present, that will determine the color that is portrayed. Because the sun is at a lower angle in the sky, colors such as red, yellow and orange are more readily to be seen through these particles.
Now it’s a “delight” when you witness this red sky at night because that could mean that stormy weather is moving out of your area.
On the other hand, you should probably “take warning” the next time you see a red sky in the morning because that most likely means unsettling weather may be rumbling through your area shortly.
Image: Blue sky frames a cumulus cloud (Wikimedia Commons)
The Million Dollar Question: Why Is the Sky Blue?
Short answer: the sky isn’t really blue; in fact, the sky has no color at all. Researchers have found that the blue color that we see on a clear day is based off how sunlight “scatters” through our atmosphere. Think of a prism and how it is made of glass and when light travels through the prism, colors of the rainbow radiate from it. This is how to think of the sky, a thin prism layer that when white light from the sun beams through it we see the bluish color as a result.
Okay, but why Blue? Why Not Purple?
Great question! If you recall that useful acronym from grade school that outlined the colors of the rainbow, ROY G. BIV, you’ll remember that certain colors react to light differently than others. For example, red, orange and yellow have lower energy levels than blue, indigo and violet. Meaning that when sunlight passes through our atmospheric prism, red, orange and yellow will scatter the least.
The result is similar on the other side of the coin; colors such as blue, indigo and violet scatter the most, which is why we see these colors more predominately. This scattering is known as Rayleigh scattering, named after Lord Rayleigh, and means that as the white light from the sun shines through our atmospheric prism, molecular collisions by atoms take place. So, long answer short? The sky is technically indigo and violet too, but because these colors have so much energy it is mainly kept at near the top of the atmosphere where we can’t see them unless we’re piloting a spacecraft.
What About the Colorful Sunsets and Sunrises?
These are amazing to gawk at after a long day of work or school, but there’s a little secret that may make one rethink this “breath of fresh air.” Remember how we mentioned that light is scattered through our atmosphere, radiating that beautiful blue color we see? Well, the same is still true at the end and beginning of the day as well. It’s just that there may be more at work here.
There’s an old meteorological saying that pirates used in the Northern Hemisphere when deciding to venture out at sea: “Red sky at night, sailor’s delight!” and “Red sky in the morning, sailor’s take warning!” Both sayings depict what happens when there is enough “stuff” in the atmosphere that sunlight has to “scatter” through, giving off a reddish hue in the sky. Now based off of pollution in the atmosphere or how much dust particles are present, that will determine the color that is portrayed. Because the sun is at a lower angle in the sky, colors such as red, yellow and orange are more readily to be seen through these particles.
Now it’s a “delight” when you witness this red sky at night because that could mean that stormy weather is moving out of your area.
On the other hand, you should probably “take warning” the next time you see a red sky in the morning because that most likely means unsettling weather may be rumbling through your area shortly.
Image: Blue sky frames a cumulus cloud (Wikimedia Commons)