\nSo I thought about this, and said by the combustion of hydrogen-containing fuels, but immediately realized that this wasn’t going to cut it (yes, I could have said ‘respiration’ and talked about haem-Cu reductases and oxygen atmospheres but I want to riff off that for another blog entry. Besides, chemistry then<\/em> biology, right?). <\/p>\n \nHow can you understand that H + O 2<\/sub> \u2014> H 2<\/sub> O if you don’t know what H or O are?<\/p>\n \nWe started basic. Real<\/em> basic. Back when the Universe formed, I said, all that there were was hydrogen atoms (I lied), and drew a little circle. I said that there’s more hydrogen than anything else in the universe and that hydrogen atoms are actually friendly little things and like to go around in pairs. I then said that if you squish hydrogen molecules together you can turn them into liquid, but if you do this even more they fuse<\/em> and become ‘helium’. I said that hydrogen atoms weigh ‘one’ (‘one what<\/em>?’ asked YP, incisively. Good girl), but that helium atoms are number ‘two’, weigh ‘four’, and are very unfriendly.<\/p>\n \nIf you then squeeze helium together in the same way you can get beryllium, and then oxygen atoms, which like to be friends with two other atoms.<\/p>\n \n‘Oh,’ said EP, ‘the weight<\/em> is twice the number<\/em>?’<\/p>\n \n‘Up to a point, yes. But the weight gets bigger quicker, so chlorine\u2014which we put in the pool, yes?\u2014is number 17 but weighs 36, for example’ (I know, I know, shut up. It’s close enough).<\/p>\n \nIf you could mix these first atoms together in the right way, in the middle of stars, I continued, you can get the other atoms, like carbon. And carbon, you see, is really<\/em> friendly and likes to make friends with four other atoms, like hydrogen, and then you get methane. Sometimes it makes friends with other carbon atoms, and do you know what this is?<\/p>\n \n \nIt’s what the lead in this pencil is made of. And if you organize the carbon atoms a bit differently so they stick out of the paper you get diamond.<\/p>\n \n“Coo-oool” chorussed the Pawns.<\/p>\n \nAnd the incredible thing is that all these atoms were made in stars right back at the beginning of the Universe, billions of years ago. And when a star dies<\/em> \u2014<\/p>\n \n‘That’s when the sun gets bigger than the solar system and then shrinks to nothing’ said YP.<\/p>\n \nExactly. When a star dies, or goes ‘nova’, these new atoms are spread into space and form part of new stars, and planets, and you and me. We’re made from bits of old stars. <\/p>\n \n‘Wow.’ <\/p>\n \n(And that piece of news was shared rapidly and enthusiastically at school on Wednesday).<\/p>\n \n \nSo what happens, I said, drawing butane, is if you have a molecule like this with all carbons and hydrogens all friendly and happy, and add an oxygen molecule\u2014which is what happens when you burn things\u2014then because oxygen is friendly with just about every atom (including itself) it breaks all these other bonds, and you get carbon dioxide (because oxygen is such a good friend with carbon there only needs to be two) and…<\/p>\n \nwater. Dihydrogen monoxide. H 2<\/sub> O. <\/p>\n \nAnd that’s how we make it. <\/p>\n \n \nI said that we can also break water apart: if we stick an electric current through water it splits into hydrogen and oxygen gas. Their little eyes lit up and before they could ask if we might try that, I changed the subject.<\/p>\n \nI told them that the process by which we got our atoms of all sizes is called ‘fusion’, and asked them if they knew what ‘fission’ was. That’s when I drew a uranium atom. <\/p>\n \n‘OK, you’ve heard of nuclear weapons? Atomic bombs? No?’<\/p>\n \nI explained that if you had a lump of uranium about this size it would be warm, and it would give you radiation burns and cancer, because all the time it’s spitting out little things that are a bit like hydrogen atoms\u2014they weigh ‘one’ and they’re travelling very fast. And when one of these neutrons hits another uranium atom, it will break it apart, and two or three more neutrons will come out, and they’ll hit two or three more uranium atoms and… they got the point of a chain reaction. Each time this happens, I said, you get an enormous amount of heat given off. And if you have two pieces of uranium, and bang them together very quickly like *this*<\/em>, you’ll wipe out Sydney.<\/p>\n \n \nSeriously, I said. It’s so powerful, it would kill everyone within five miles.<\/p>\n \n‘Could you make one?’ they asked, horrified and fascinated. No, I explained, I couldn’t make one. You’d need a lot of money and machines and people.<\/p>\n \n‘I hope people never do it,’ said EP, fervently.<\/p>\n \n‘Sweetheart,’ I said, ‘it has been done.’ And I told them about Nagasaki and Hiroshima, about the hundred thousand people that were killed each time, about how certain people were worried because they think North Korea and Iran might be trying to make this sort of bomb instead of using uranium for power generation like they claim to be trying to do, and how the countries that do make these bombs are very scared to use them because they know how deadly they are.<\/p>\n \nBut, I said, you can control this reaction and use it in powerstations. France makes most of its electricity this way. It’s clean, there’s no greenhouse gasses\u2014<\/p>\n \n‘Why don’t we all do that then?’ demanded YP.<\/p>\n \nI said it’s a political issue. I said the Greenies were intellectually inconsistent. I said there had<\/em> been accidents\u2014Three Mile Island and Chernobyl\u2014but the technology then wasn’t as good as it is now and people hadn’t followed safety procedures.<\/p>\n \n‘Well that was stupid, then,’ said YP.<\/p>\n \nHell, if a nine year old can figure it out, it can’t be that difficult, can it?<\/p>\n \nAnd then I said, as powerful as fission is, fusion\u2014the process in the middle of stars that makes them hot, the process that makes all the atoms that make you and me and the earth and everything in it, how we get the H and the O and the C and everything<\/em> \u2014is yet more powerful. Each time you fuse hydrogen, you get much more energy than you do from splitting uranium.<\/p>\n \n‘Oh,’ said EP, nonchalantly, ‘we’ve been told about fusion power. Why don’t we use it?’ and then I had to explain why they couldn’t come into the lab and try to fuse hydrogen or make liquid helium: except it was time for school and we were running late.<\/p>\n","protected":false},"excerpt":{"rendered":" “How do we make water?” That was the question I was asked on Wednesday morning, by the Younger Pawn (YP, nine on 5th November). Not, as you might expect, “where does water come from?” but specifically, “how do we make … Continue reading ![\"\"](\"http:\/\/friendfeed.s3.amazonaws.com\/6dc57b84ed96bfec086b1318e23c4d1b103f6195\")
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