The Big Blue Sky
I have so many vivid memories, as do many others, of being a kid and being so curious. I would roll down a grassy hill, ride a bike, or simply just look up... and every time I found myself wondering why the sky is blue. Why couldn't it be green? It was something I wondered for so long. Both of my parents are in the science field, so every time I asked, and they TRIED to answer, I never understood because it was so overly complicated. Surely anyone now can look it up, but to this day I find it so interesting and I enjoy sharing it.
So why is the sky blue?
A lot of other smart people have wondered that too. And it took a long time to figure it out! To the human eye its blue, but it's actually all of the colors (Why is the sky blue? rmg.co.uk). I will be sharing what I've learned about what makes the sky blue, why the blue fades at sunset, and the color of the sky on other planets.
The light from the Sun looks white. But it is really made up of all the colors of the rainbow. When white light shines through a prism, the light is separated into all its colors. Like energy passing through the ocean, light energy travels in waves, too. Some light travels in short, "choppy" waves. Other light travels in long, lazy waves. Blue light waves are shorter than red light waves. Sunlight reaches Earth's atmosphere and is scattered in all directions by all the gases and particles in the air (Why Is the Sky Blue? scijinks.gov). Blue light is scattered in all directions by the tiny molecules of air in Earth's atmosphere. Blue is scattered more than other colors because it travels as shorter, smaller waves. This is why we see a blue sky most of the time.
(Photos taken by me, top to bottom they're located in
Costa Rica, Maryland, Spain and Hawaii)
But what makes a red sunset?
When the air is clear the sunset will appear yellow, because the light from the sun has passed a long distance through air and some of the blue light has been scattered away. If the air is polluted with small particles, natural or otherwise, the sunset will be more red. Sunsets over the sea may also be orange, due to salt particles in the air.
The sky around the sun is seen reddened, as well as the light coming directly from the sun (Why Is the Sky Blue? math.ucr.edu). This is because all light is scattered relatively well through small angles—but blue light is then more likely to be scattered twice or more over the greater distances, leaving the yellow, red and orange colors.
(Photos taken of/by me, top to bottom in Florida, Alabama, Indiana, Michigan, Hawaii, Hawaii, Oak Hill Apartments and Olivet College!)
Along with the blue and sunset colors on Earth, let’s now examine how they compare to the sky colors on other planets.
Have you ever wondered if the sky is blue on other planets, too?
It all depends on what’s in the atmosphere! For example, Mars has a very thin atmosphere made mostly of carbon dioxide and filled with fine dust particles. These fine particles scatter light differently than the gases and particles in Earth’s atmosphere.
Photos from NASA’s rovers and landers on Mars have shown us that at sunset there is actually the opposite of what you’d experience on Earth (Why Is the Sky Blue? spaceplace.nasa.gov). During the daytime, the Martian sky takes on an orange or reddish color. But as the Sun sets, the sky around the Sun begins to take on a blue-gray tone.
Science teaches us all about why the sky is blue, why the colors change during a sunset and how the skies are different on other planets. Maybe next time you look up at the sky, you’ll view it differently
So basically, to summarize everything, the sky appears blue to the human eye as the short waves of blue light are scattered more than the other colors in the spectrum, making the blue light more visible (Why is the sky blue? metoffice.gov.uk).
(I took this picture at the beginning of a sunrise in Escanaba, which is in Michigan's Upper Peninsula!)