Why does the sky turn red at sunset?
The Real Answer
Sunsets turn red and orange because sunlight has to travel through much more atmosphere when the Sun is near the horizon. Along that longer path, shorter blue wavelengths are scattered away more strongly, leaving proportionally more red, orange, and yellow light reaching your eyes.
Dust, smoke, pollution, and other particles in the atmosphere can change the effect, sometimes producing especially dramatic colors and sometimes dulling them instead. That's why two sunsets from the same location can look completely different even though the basic physics hasn't changed.
The sun isn't actually changing color — it's just that all the blue light gave up and left, and now you're looking at the leftovers. We've built our entire aesthetic of 'nature's beauty' on the fact that the sun is leaving and taking the good light with it.
The Dunce Dynamics Institute Examines Why People Ask This
This is usually asked by someone who just stopped and actually looked at a sunset for the first time in years — which is rare because we're mostly staring at our phones. Once you notice it, it's impossible to stop wondering. Most people assume it's the sun turning red, when really it's more of a cosmic game of musical chairs where blue light loses every time.