We’ve all looked up and seen a beautiful blue sky — but have you ever wondered why it’s blue? And is it always blue?
Let’s break it down.
☀️ Why the Sky Looks Blue
The sky appears blue due to a phenomenon called Rayleigh scattering. Sunlight is made of all colors, but as it passes through the atmosphere, the shorter wavelengths — especially blue and violet — get scattered in all directions by the molecules in the air.
So why don’t we see violet?
“Although violet light is scattered more, our eyes are more sensitive to blue light,” explains NASA. “Also, some violet is absorbed by the upper atmosphere.”
→ NASA Earth Observatory: Why is the Sky Blue?
🌇 Why Sunsets Are Red and Orange
During sunrise and sunset, the sunlight has to travel through more atmosphere, scattering all the blue and green light out of view. What’s left? Reds, oranges, and pinks.
A study in the Journal of the Atmospheric Sciences found that red light intensity increases significantly at low solar angles, creating the dramatic hues we love.
→ Journal of the Atmospheric Sciences Study (2008)
🌈 Can the Sky Be Other Colors?
Yes! Depending on the conditions, the sky can also appear:
- White or gray (due to water vapor or pollution)
- Pink or purple (during certain sunrises or sunsets)
- Black (at night or when viewed from space)
🧠 Expert Insight
“The sky is not blue because of reflection — it’s blue because the atmosphere acts like a filter,”
says astrophysicist Dr. Neil deGrasse Tyson.
→ Dr. Tyson in “Astrophysics for People in a Hurry”
