YOU are made of carbon. So are your pets and all your houseplants. Every living thing on Earth owes its existence to carbon atoms\u2019 ability to join up with other elements in a bewildering number of ways and form complex molecules. But the abundance of this element in our universe depends on a seemingly miraculous coincidence \u2013 an excited state of the carbon nucleus that our best models say shouldn\u2019t exist<\/a>, but clearly does.<\/p>\n The nature of this weird form of carbon has baffled us for more than 60 years, much to the distress of nuclear physicists. Its existence is so essential in the sequence of reactions making life possible that our failure to explain it is deeply embarrassing. \u201cWe need this state to exist for us to be here and yet it is extremely unusual in nuclear physics terms,\u201d says David Jenkins at the University of York<\/a>, UK. \u201cCracking this problem has become a matter of pride.\u201d And yet the more we learn, the more confusing things seem to become.<\/p><\/blockquote>\n This is from “Life\u2019s subatomic secret: How we\u2019re cracking the Hoyle state<\/em><\/a>,” by Marcus Chown<\/span> (NewScientist<\/strong><\/em>, 22 October 2016, paywall), and I’d never heard of this particular mystery before. It’s fascinating stuff – but, being high energy physics, is way beyond me. I can sort of follow this:<\/p>\n Source: openclipart.org<\/strong><\/a><\/p><\/div>\n The first step in carbon manufacture is to fuse nuclei of the lightest element, hydrogen, to make the second-lightest, helium. The next step ought to be for two helium-4 nuclei \u2013 each containing two protons and two neutrons \u2013 to fuse to make beryllium-8<\/a>. This would then grab another helium to make carbon-12. Except there is a snag. Beryllium-8 is highly unstable, meaning it decays in the blink of an eye \u2013 too quickly to produce the amount of carbon that exists in the universe.<\/p>\n The other possibility is that three helium-4 nuclei come together simultaneously inside bloated, dying stars known as red giants, where all the hydrogen has burned off to leave an extremely dense and hot core of helium. But this process is so rare that even over the aeons since the big bang, it couldn\u2019t have produced enough carbon.<\/p><\/blockquote>\n But after that I get lost (why is beryllium-8 unstable?<\/em>1<\/sup> for example) , except to understand they’re using supercomputers to computationally model the problem.<\/p>\n I think there’s two reasons an article like this fascinates me. First, physicists are some of the smartest folks in the world, so it’s good to see them bemused.<\/p>\n Second, the activity of attacking a puzzling mystery often leads to all sorts of interesting knowledge. I can’t wait to see if that’s true of this mystery.<\/p>\n 1<\/sup>The\u00a0Isotopes of beryllium<\/a> page in Wikipedia is actually fascinating, not for the why, but the what. For example,<\/p>\n The rate at which the short-lived 7<\/sup>Be is transferred from the air to the ground is controlled in part by the weather. 7<\/sup>Be decay in the sun is one of the sources of solar neutrinos<\/a>, and the first type ever detected using the Homestake experiment<\/a>. Presence of 7<\/sup>Be in sediments is often used to establish that they are fresh, i.e. less than about 3\u20134 months in age, or about two half-lives of 7<\/sup>Be.<\/p><\/blockquote>\n","protected":false},"excerpt":{"rendered":" I must admit my interest is whetted when an article on physics starts out, YOU are made of carbon. So are your pets and all your houseplants. Every living thing on Earth owes its existence to carbon atoms\u2019 ability to join up with other elements in a bewildering number of \u2026 Continue reading \n
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