Earth as seen from orbit. Sapphire marbles can be seen spinning in the void. There is a reason to call it the blue planet. 71% of the surface is water. This color is very easy to understand. It controls our perspective.
But why blue?
Most people guess the sky. They only see the sea as a mirror. If the sky is blue, the sea reflects it. If the sky is gray and stormy, the sea will also appear gray. This is true. This is the most obvious reason. This is not the main reason either.
Cave workers and divers know this. Enter the underwater cave. Blocks the sky. A white light shines on the surface of the water. The water is still blue.
How light travels underwater
The answer lies in physics. Especially absorption.
Sunlight is white. It is actually a mixture of all the colors of the visible spectrum. When light hits the ocean, two things happen. Some bounces off. However, some ended up in the water. It will bend. It travels down.
This is where the magic happens. Water molecules eat light. They absorb different wavelengths at different rates.
Red and yellow waves are underdogs. They disappeared quickly. The red and yellow colors disappear at a depth of 10-30 meters. The green wave lasts a long time. But by 60 meters, even they disappear.
Blue is stubborn. Penetrates to the deepest level. This is the last color to absorb and finally disappear at 90 meters. So when we look at the ocean, we see the light that has survived the journey. What we see is blue because it is the only remaining wavelength.
Green exception
It’s not always blue.
Sometimes the water turns green. This happens when phytoplankton is present. These contain chlorophyll.
Chlorophyll prefers to absorb blue light. Use this energy for growth. When these plants are Abundant in the water, the blue waves are quickly swallowed up. The green waves are still there. The ocean shifts from blue to green.
Therefore, the color of seawater is determined by the substances in the seawater. Clear water reveals the physics of absorption. Opaque water reveals biology. Both can tell something about the health of the planet.
When you look at the sea, you see blue. I think it’s 天のいたずら。 it’s not. This is 生り残语の教訓です。 戦いだがが通過とは The spectrum of water filter. 青がりますます。
We are only looking at the surface, so what else are we missing?
