0 Members and 1 Guest are viewing this topic.
Everything underwater looks very blue doesn't it? The reason for this, and hence the "blueness" of the sea, is similar in some ways to the reason that the sky is blue.Water molecules resemble tiny boomerangs, with a central oxygen atom at the apex and two hydrogen atoms at the tips. These molecules can soak up light in the infrared (heat) end of the spectrum. This is why water vapour in the atmosphere is a more potent greenhouse gas than carbon dioxide.But in the ocean, where water molecules are surrounded by many other water molecules, a phenomenon called hydrogen bonding occurs. These are weak "inter-molecular" attractive forces; put simply, water is what's known as a "polarised molecule". The central oxygen pulls the electrons of the two hydrogens towards itself, making the hydrogens slightly plus and the oxygen slightly minus. Since unlike charges attract, a hydrogen on one molecule will be attracted to the oxygen of another, adjacent, water molecule. This makes water sticky and accounts for its wonderful life-sustaining properties.The consequence of this hydrogen bonding is that it makes the molecules "stiffer" so when light hits water, instead of absorbing just in the infrared it begins to absorb more strongly at visible red wavelengths too. Because red wavelengths are being soaked up, leaving relatively more blue light behind, the water looks blue. And the deeper you go the more pronounced this effect, so the "bluer" everything looks.Ice also does this, which is why the thick walls of ice at the Earth's poles, and on glaciers, have that beautiful blue hue. Chris