Colors of the Sky

Akku: Mommy, why is the sky red during sunset and sunrise?

Wow Akku, this is a very common question all the kids love to know. First let me explain why the sky is blue.

The light from the Sun looks white. But it is really made up of all the colors of the rainbow. Earth’s atmosphere is a mixture of the molecules (both gas and other types) that surround the earth. When sunlight reaches Earth’s atmosphere, light of longer wavelengths, like red, yellow, and orange, easily passes through, while light of shorter wavelengths, such as blue and violet, is absorbed and then scattered in all directions by the gas molecules. 

When you look up at the sky during the day, this scattered blue and violet light reaches your eyes, however, the human eye is more receptive to blue frequencies than violet frequencies, so the sky looks blue. Scientists call this Rayleigh scattering. This is why we see a blue sky most of the time.

Akku: Wow, that’s so cool. So mommy, is the sky blue on other planets, too?

It all depends on what’s in the atmosphere. For example, Mars has a very thin atmosphere made up 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 that at sunset there is actually the opposite of what we experience on Earth. 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-grey tone.

Akku: Interesting! But mommy, then why is the sky red during sunset and sunrise?

During sunsets and sunrises, when the Sun is closer to the horizon, sunlight passes through more air than during the day, when the sun is higher in the sky. More atmosphere means more molecules to scatter the violet and blue light away from your eyes.

If the path is long enough, all of the blue and violet light scatters out of our line of sight. The other colors continue on their way to our eyes. This is why sunsets are often yellow, orange, and red. And because red has the longest wavelength of any visible light, the sun is red when it’s on the horizon.

Akku: Wow nice. Thanks Mommy! This is a lot of info. See you later.

Sure Sweetie! Waiting for more curious questions! 

Can I touch a Rainbow?

Akku: Mommy how is a rainbow formed?

Akku, you got a really complicated question this time. It’s a hard thing to explain. Before I start, you need to understand two things – reflection and refraction..

rain drop

Akku: Yes I know it’s something related to bending and bouncing of light, right mom?

That’s correct. The bouncing back of rays of light from a shiny surface is called Reflection of light. Whereas, the change in the direction of light when it passes through a different medium is known as Refraction of light.

So rainbows are formed when the sunlight passes through raindrops. The light is refracted as it enters the droplet and then reflects off its inside. And this causes all the amazing colors of the rainbow.


Akku: But why do we see only 7 colors?

Visible light, that is sunlight is made up of various wavelengths, and each wavelength appears as a different color: red, orange, yellow, green, blue, indigo and violet. Red light, for example, bends at a different angle than violet light. A great way to remember these colors is to think of a man’s name: ROY G BIV. When the sunlight passes through raindrop, it acts like a tiny prism and each color bends differently due to different wavelengths, thus splitting the light into seven colors.

Akku: Wow thanks for that ROY tip. Can we see a rainbow every time it rains?

Not all the time. The best time to catch a rainbow is when it’s sunny and raining. There is an even better chance when the sun is at a lower angle, so early or later in the day. On the other hand, if the angle is not right, the rainbow formed will not be visible. The key is to face the rain and have your back to the sun.

clay rainbow

Akku: Next time I am definitely going to see a rainbow. Hurray!! And Mom, can we touch a rainbow?

Can you touch light? No, right? Same way rainbow is just an optical illusion, so you just can’t catch up to it. When you move, so does it. We can’t touch it, neither feel it. It’s just light.

Akku: Oh yeah. Can we at least go the end of the rainbow and find the treasure?

I wish we could. But that’s also not possible. There is no end to a rainbow, it’s an optical illusion! Even though they look like an arch to us, rainbows are actually full circles. We see only part of the circle because the horizon blocks the rest of it from our view. Pilots high in the sky do sometimes report seeing genuine full-circle rainbows.

Akku: Wow!! I never knew that rainbow has a full circle. Cool! But I have seen a double rainbow. How does that happen?

Oh yeah ! A double rainbow happens when the light bends and reflects off the water drops in the air twice. In other words, the second rainbow is a reflection of the first rainbow. The second rainbow formed will be lighter in color and the colors will be reversed, just like a mirror reflection.

double rainbow

Akku: Nice! A mirror effect. Can a rainbow appear during night?

Oh yes, they’re called moonbows! The night time rainbow is extremely uncommon and occurs only when the moon is sufficiently brilliant and positioned properly with respect to falling rain to produce the delightful effect.

lunar rainbow
Photo of a Lunar Rainbow taken from the Zambia side of Victoria Falls. Photo courtesy Calvin Bradshaw (
Akku: That must be really beautiful. Thanks so much mom for this amazing facts about rainbows! See you later, Bye!

Mom: You are welcome dear!

The way I see it, if you want the rainbow, you gotta put up with the rain.
― Dolly Parton