Covering around 71% of the Earth’s surface, water is one of, if not the most fundamental components of life on Earth. We’ve all seen it, consumed it and even swam in it. So when asked what colour it actually is, there should be little debate. Pour yourself a cool cup of water and it looks clear and colourless.
Yet the oceans, where 96.5% of the Earth’s water is held, appears blue. Why is this?
While it wouldn’t be untrue to think that the ocean only appears blue as the water is reflecting the sky, there’s more to it than that. In reality, it is a slightly blue molecule, but maybe not the blue you’d expect. Unlike the deep blue of the ocean, water molecules’ colour is a light turquoise, caused by weak amounts of absorption in the red part of the visible spectrum. This is what gives glacial ice its dramatic colour.
So why isn’t all water this colour? Basically, it is very rare that you’ll encounter completely pure water in your everyday life. Different impurities, such as salts, minerals and plant matter, change the colour of the liquid we see. But what about the “pure” bottled water? Well, it still contains small amounts of impurities too, and for a good reason. Despite being made mostly of it ourselves, drinking pure water can kill you. Pure water can cause what is known as “water poisoning”, where cells absorb too much water, and can burst. In extreme cases this can cause brain damage, a coma and even death. Water is just another example of the secrets our great planet contains if we choose to look closely enough.
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