Comments on: Roman shipwreck to aid in search for neutrinos http://www.thehistoryblog.com/archives/6054 History fetish? What history fetish? Wed, 08 Feb 2012 17:54:06 +0000 hourly 1 http://wordpress.org/?v=3.2.1 By: livius drusus http://www.thehistoryblog.com/archives/6054/comment-page-1#comment-48599 livius drusus Sat, 29 May 2010 04:01:59 +0000 http://www.thehistoryblog.com/?p=6054#comment-48599 Well, when I wouldn't call them impurities, really. The ore is just a mixture of several elements. There's uranium in various stages of decay, silver, copper, even gold. That's no good for commercial purposes, of course, because the buyers aren't paying for a mixture of a bunch of stuff; it's the lead they want, so part of the mining process is separating it from things that are not lead. Well, when I wouldn’t call them impurities, really. The ore is just a mixture of several elements. There’s uranium in various stages of decay, silver, copper, even gold. That’s no good for commercial purposes, of course, because the buyers aren’t paying for a mixture of a bunch of stuff; it’s the lead they want, so part of the mining process is separating it from things that are not lead.

]]> By: rwmg http://www.thehistoryblog.com/archives/6054/comment-page-1#comment-48598 rwmg Sat, 29 May 2010 03:56:38 +0000 http://www.thehistoryblog.com/?p=6054#comment-48598 So lead ingots are purer lead and aren't absorbing radiation from the impurities? OK, that makes sense to me. So lead ingots are purer lead and aren’t absorbing radiation from the impurities? OK, that makes sense to me.

]]> By: livius drusus http://www.thehistoryblog.com/archives/6054/comment-page-1#comment-48594 livius drusus Sat, 29 May 2010 02:09:22 +0000 http://www.thehistoryblog.com/?p=6054#comment-48594 The radioactive isotopes still decay even when they're in the ground, but they're also replenished by the continual decay of radioactive minerals around them. Let me see if I can explain this halfway intelligently. Lead-210, the primary radioactive isotope in the ingots, is the product of the decay chain of uranium-238. It takes billions of years for radioactive uranium to decay into lead-210. Once the lead is removed from the ground and crushed/roasted/melted into pure lead ingots, all of the other elements that are steps in the uranium decay chain are left behind, so what you're left with is a small fraction of radioactive lead-210 mixed in with all the stable lead isotopes. Lead-210 has a very short half-life of just over 22 years. These 2000-year-old ingots, therefore, have seen their lead-210 content decrease by half almost a hundred times, and there was never much in there to begin with. That's about as good as it's going to get to for the physicists studying neutrinos. Does that make sense? The radioactive isotopes still decay even when they’re in the ground, but they’re also replenished by the continual decay of radioactive minerals around them.

Let me see if I can explain this halfway intelligently. Lead-210, the primary radioactive isotope in the ingots, is the product of the decay chain of uranium-238. It takes billions of years for radioactive uranium to decay into lead-210. Once the lead is removed from the ground and crushed/roasted/melted into pure lead ingots, all of the other elements that are steps in the uranium decay chain are left behind, so what you’re left with is a small fraction of radioactive lead-210 mixed in with all the stable lead isotopes.

Lead-210 has a very short half-life of just over 22 years. These 2000-year-old ingots, therefore, have seen their lead-210 content decrease by half almost a hundred times, and there was never much in there to begin with. That’s about as good as it’s going to get to for the physicists studying neutrinos.

Does that make sense?

]]> By: rwmg http://www.thehistoryblog.com/archives/6054/comment-page-1#comment-48591 rwmg Sat, 29 May 2010 00:46:54 +0000 http://www.thehistoryblog.com/?p=6054#comment-48591 I'm curious. What is the difference between lead taken out of the ground and lead in the ground that the radioactive isotopes of lead which has been taken out of the ground decay while the radioactive isotopes of lead which is still in the ground don't? I’m curious. What is the difference between lead taken out of the ground and lead in the ground that the radioactive isotopes of lead which has been taken out of the ground decay while the radioactive isotopes of lead which is still in the ground don’t?

]]> By: livius drusus http://www.thehistoryblog.com/archives/6054/comment-page-1#comment-48577 livius drusus Fri, 28 May 2010 17:12:09 +0000 http://www.thehistoryblog.com/?p=6054#comment-48577 Now you've gone and made me look up Clive Cussler. I have enough to read, dammit! :angry: Now you’ve gone and made me look up Clive Cussler. I have enough to read, dammit! :angry:

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