Why Is the Sky Blue?
When you look up on a clear day, the sky looks bright blue. But why blue? Why not green or purple? The answer is in the way sunlight travels through the air.
Sunlight Is Not Just White
The light from the sun looks white, but it’s actually a mix of many colors. You can see this in a rainbow—red, orange, yellow, green, blue, and violet. Each color is like a different “flavor” of light.
👉 Example: Think of sunlight like a box of colored pencils. You don’t see them separately at first, but they’re all there.
What Happens in the Sky
When sunlight enters the air around Earth, it bumps into tiny gas molecules (like oxygen and nitrogen). This makes the light spread out in all directions. This spreading is called “scattering.”
Blue light scatters the most because it travels in short, quick waves.
Red light scatters the least because it travels in long waves.
👉 Example: Imagine throwing small stones and big balls into a pond. The small stones make ripples spread out quickly, just like blue light. The big balls make slower, wider ripples, like red light.
Since blue light scatters more, we see the whole sky filled with blue.
Why Sunsets Are Red or Orange
At sunset or sunrise, the sun is lower on the horizon. The light has to travel through more air. By the time it reaches your eyes, most of the blue has scattered away, and the leftover colors are red and orange.
👉 Example: It’s like shining a flashlight through a glass of water. If the water is shallow, the light passes easily. If the water is deep, the light looks darker and changes color.
Why Clouds Look White or Gray
Clouds are made of water droplets. These droplets scatter all colors equally, which mixes them back into white. On dark, rainy days, the clouds are thicker and block more light, making them look gray.
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