I used to be a very inquisitive child; while I was capable of seeing the beauty in my surroundings, I was not blind to the fact that said beauty usually hides questions that cannot be answered by my then limited mental faculties. One of the questions that I kept asking adults was “Why is the sky blue?”
The answer was usually “Shut the hell up and eat your vegetables” but sometimes I’d get lucky and I get rough explanations like “the sky is not really blue. It just looks blue Because Science.”
Eventually, I grew up and forgot all about the sky and its stupid blue color, because my inquisitive teenage mind was busy answering questions that I deemed more practical (e.g. where da pron at?)
Then science went full dick on me and revealed that the principles behind the sky’s blue shade is actually a lot more complicated than I thought: It may have a lot to do with rocks, phosphorous and ancient algae, according to a new study:
For the first two billion years of Earth’s history or so, the sky was probably orange. We’re not sure whether that’s really true — no one’s been able to hop in a time machine and go back and check — but based on what we know about the chemistry of that time period, there’s a good chance the atmosphere’s primary component was methane (CH4), which would’ve cast a strange pall over our young planet.
These days, the atmosphere is mostly nitrogen and oxygen. Sunlight is made up of all the colors of the rainbow (as well as many wavelengths we can’t see); as it jostles through air molecules, blue light is most efficiently reflected, so our eyes end up experiencing a beautiful azure shade.
How did it change from orange to blue? About 2.5 billion years ago, the newest fad in organisms was photosynthesis — the ability to to turn sunlight, carbon dioxide (CO2) and water into sugar. Armed with the latest evolutionary accoutrement, ancient algae had it made — an everlasting food source and all the world’s oceans to expand into.