Why the Sky Is Blue (But Sunsets Are Red)
Sunlight looks white, but it's actually all colours mixed together. Blue light bounces around in the atmosphere, turning the whole sky blue. At sunset, light travels further and the blue scatters away — leaving only the warm reds and oranges.
Two facts about the same sunlight. One for the dinner table, one for the next clear evening.
The Sky Is Blue Because Blue Light Can't Travel in a Straight Line
Sunlight looks white, but it is every colour mixed together. You can see this when rain splits it into a rainbow.
Here is where it gets interesting. When sunlight hits Earth's atmosphere, it collides with tiny gas particles. Most colours pass through without much fuss, but blue light bounces off those particles in every direction, scattering across the entire sky. It is essentially ricocheting around above your head all day long. Red and orange light, meanwhile, cuts straight through. You do not notice it as much because it is not being flung around in all directions.
Try this: fill a glass with water, stir in a few drops of milk, and shine a torch through it in a dark room. From the side, the water glows faintly blue. From behind the glass, the light looks warmer, more orange. You have just built a tiny atmosphere on your kitchen table.
Sunsets Are Red Because the Blue Already Left
At sunset, the Sun sits low on the horizon. Its light has to travel through far more atmosphere to reach your eyes than it does at midday. All that extra distance means the blue light scatters away long before it gets to you. What arrives is whatever is left: the reds, the oranges, the deep golds.
The same Sun. The same light. Just a longer journey. I find that oddly satisfying: every sunset is not the Sun changing colour, it is you seeing what was always there once the blue gets out of the way.
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