Explain · analogy
Why the sky is blue in terms of a pinball machine
The sky is basically a massive, overhead pinball machine where sunlight is the ball being smacked around by the atmosphere.
Sunlight arrives from the sun as a multi-coloured ball, containing every hue from red to violet, hurtling into the gas molecules of our upper atmosphere. These molecules act like those little rubber bumpers on a tabletop game, but they are incredibly biased against short wavelengths. While the reds and oranges zoom straight past the obstacles to hit the far side of the table, the blue light gets clipped by every single bumper it passes. It pinballs wildly in every direction, ricocheting off nitrogen and oxygen until it hits your eye, making the entire sky look like it has been lit up by a moody teenager with a glow stick.
When the sun sets, the light has to travel through a much thicker gauntlet of these gas molecule bumpers to reach you. By the time it clears the queue of obstacles, all the blue light has been scattered off into the stratosphere, leaving only the reds and oranges to finish the journey. It is essentially the physics equivalent of losing your marbles, only to have the ones that survive the collision turn into a romantic postcard of a sunset. Even the atmosphere loves a dramatic exit after spending the entire day making a mess of the blue light.
Where the analogy breaks downA pinball machine has a metal ball that stays in play, whereas light is scattered by gas molecules and carries on to your eye.