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Hi everyone, Helium is the second most common element after Hydrogen. Most Helium was produced during the begining of the universe, when the whole universe ended up about 75% hydrogen and 25% helium and just about nothing else. Since that time helium manufacture has taken place in stars, where under the right conditions, at about 15 million degrees, hydrogen is fused in a multi step process to form Helium. Roughly speaking 4 protons form 1 helium (two protons and two neutrons) and some other bits and pieces and heaps of energy. This is not the helium that we use to breathe when diving. In a large star (I think about twice ours or more, but I don't have the figures) as the hydrogen runs out the innner part of the star contracts and heats up. (in our star the end will be different, but this bit is much the same) The outer part of the star will expand, as it is held up by the greater flux of radiation pressure generated by the hotter interior. It will now start "burning" the helium and as that runs out, other elements. These reactions produce less energy than the hydrogen burning and the star contracts further in the center. Eventually an "ash of a hard to fuse element builds up in the centre of the star. (I think it's oxygen, but don't quote me) Eventually the stars fires go out and it collapses gravitaionally. The center all fuses at once and all the elements we know that are above oxygen on the periodic table get created all at once. This blows the star to bits and the new elements are spewed out all over at great speed. This is were most of the stuff that makes up your body (and the earth) were created. Making these elements requires that energy is put in (oposite to making the lighter elements where you get energy out) so most of these elements "want" to break up and make iron56 which is the lowest energy element. They do this by emitting an Alpha particle (He atom without electrons). This is called "radioactivity" and is the source of Helium we use here on earth. Helium is found naturally in the air and is a by-prduct of air distillation. It is about one quater as common as neon in the air. Since the only source of neon is air distillation, we could expect that if our only source of He was air distillation, then it would be four times as expensive as neon. The best price I have got for neon here in Australia is $0.73 per litre if I buy 10 000 litres at a time. Four times this is $2.92 per litre or about $2.15 in US dollars per litre. Or about $60 US per cubic foot. Roll on rebreathers. Cheers Jason O-)
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