“Whenever I gaze up at the moon, I feel like I’m on a time machine. I am back to that precious pinpoint of time, standing on the foreboding — yet beautiful — Sea of Tranquility. I could see our shining blue planet Earth poised in the darkness of space.” –Buzz Aldrin
Seen from afar, Earth is often described as a pale blue dot. But why is our planet blue? Is it because the skies are blue? That can’t be right, or the clouds and icecaps would appear blue-hued as well. Is it because the blue skies are reflected by the oceans? That can’t be right either, or we wouldn’t see different shades of blue at different oceanic depths.
The answer lies in the properties of water itself: it absorbs different wavelengths of light with different efficiencies, and is worst at absorbing blue light. That’s why, the deeper you go, the bluer underwater marine life appears, and that’s also why the blue light is most efficiently reflected back off the water, at all depths, and into space.
The Earth may not be our Solar System’s only blue planet, but the physics of its blueness is unique! Find out the full story on Forbes today.