 state, you've changed the chemistry of everything else that happens on Earth. So originally, if we go back more than three billion years, Earth probably had this hazy orange sky that was full of methane and carbon dioxide and was kind of smoggy. When life started to oxygenate the atmosphere, it shifted the color of the sky to the blue part of the spectrum by changing the chemical composition of the air. So life is really why we have a blue sky in the first place.