Someone once asked...
Someone answered with kindness...
Honestly? Rayleigh scattering — sunlight hits our atmosphere and blue light, which travels in shorter, choppier waves, gets bounced around way more than red or yellow light does. So by the time it reaches your eyes, the sky's flinging blue at you from every direction. But the question I always find more interesting is why it's not violet, since violet scatters even more than blue. Turns out our eyes are just less sensitive to violet, and some of it gets absorbed high in the atmosphere before it even gets to us. So blue wins by a kind of technicality.
Another soul answered...
On clear days, the air contains countless tiny particles such as dust, water droplets and ice crystals. As sunlight travels through the atmosphere, longer‑wavelength red, orange and yellow light pass straight through and reach the ground. In contrast, shorter‑wavelength blue, violet and indigo light are readily scattered in all directions by these airborne particles, giving the sky its characteristic azure‑blue colour. Only a fraction of the blue light gets scattered. Most blue and violet rays avoid these particles and reach Earth’s surface directly. For this reason, the white light arriving on Earth still consists of the full spectrum: red, orange, yellow, green, blue, indigo and violet. Have you ever noticed how much bluer the sky looks after heavy rain? The clearer the weather, the deeper the blue. This happens because clear conditions bring a high concentration of dust, water droplets and ice crystals in the air.
Another soul answered...
You know, as a kid, I used to think the sky was blue simply because it was reflecting the vastness of the ocean. It was such a poetic idea, but the real explanation turns out to be even more fascinating. It’s all about a daily light show happening right above our heads called Rayleigh scattering.