🌤️ We look at the sky every day... but ever wonder, "Why blue?"

The first answer many people think of may be that the sky reflects the color of the sea. 🌊

But in fact, even if we are in the middle of a continent with no sea nearby, the sky is still blue. 😆

The answer to this is hidden in the light of the sun + Earth's atmosphere.

☀️ Let's start with the sun.

The light from the sun that we see as white light is actually made up of many colors, from purple, blue, green, yellow, orange to red.

Each color has an unequal wavelength.

Purple and blue side light have short wavelengths, red light has longer wavelengths.

And the fun started when these lights came into the atmosphere.

🔵 Why did it finally become "blue"?

There are very small molecules in the air, such as nitrogen and oxygen.

As sunlight travels in and collides with these molecules, some of the light is scattered out in different directions.

This phenomenon is called Rayleigh Scattering.

The important thing is...

Short-wavelength light is more scattering than long-wavelength light.

So blue light is spread across the sky rather than red light.

When we look up, wherever we look, a blue light is scattered into our eyes.

So the brain interprets...

"The sky is blue." 🌤️

💜 What about purple? Wavelengths are shorter than blue, aren't they?

Yes, sir. And the purple light was greatly scattering by Rayleigh, too.

But what we see is not just scattering, it is related to the spectrum of sunlight, atmospheric absorption, and the sensitivity of the human eye to each wavelength.

When these factors add up, we perceive the sky as blue / blue rather than purple.

🌅 Then why did the evening the sky become orange and red?

This is the same physics.

During the daytime, the sun is relatively high. Light travels through the atmosphere a shorter distance.

But during sunrise or sunset, light must travel through the atmosphere a much longer distance.

Along the way, light of short wavelengths like blue was scattered much out of the line that came to our eyes.

What's left comes to us more is light with longer wavelengths, for example.

🟡 Yellow

🟠 Orange

🔴 Red

So we saw a beautiful sunset that many people like to take pictures of. 🌅

And this is a great example of...

The ordinary things we see every day are sometimes more physics hidden behind than we think.

Tomorrow, if you look up at the blue sky, imagine that the light from the sun is traveling through space, into the atmosphere, hitting tiny molecules and scattering into our eyes.

The same sky might seem a little more interesting. ☀️🌎

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