What colour is water?
The Ocean
is blue because water is a blue substance.
Many
people are sure that bodies of water are blue because the water reflects the
sky. But wouldn't this only make the shiny surface-reflections look blue? And
doesn't water sometimes remain blue on cloudy
days? Exactly. There's no
mystery here; water looks blue because water *is* blue. Pure water is a blue
chemical. It's not just the sky that creates the colours we see.
But
what if you pour yourself a drink; in that case the water is clear, right? Well
...it's not blue as far as your eyes can tell. But what if the water in your
cup actually was slightly blue. You'd never see it. You'd only notice the
blue colour if your cup was many feet wide.
In
fact, that's exactly how it works: pure water is nearly clear, but it's very slightly
blue. A small amount of water is too thin a layer, so a small amount looks
clear rather than blue. But look through thirty feet of water, especially with
a white sandy bottom, and you'll see a strong colour. Gaze into a hundred feet
of deep pure mountain lake water against a white rocky bottom on a sunny day. You'll
see exactly what colour the water actually has. Yet if you scoop a canteen full
of that lake water, it will seem totally clear.
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