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Natural Science Forum / Physics / General Physics / January 2007Interval before Nuclear Decay
My background in physics comes from Nuclear Power School in the Navy (back in the early 1970's). The Navy sent me to school so that I could operate an S5W nuclear propulsion plant (not alone, of course). So, since the '70's anything more that I've learned about nuclear physics, I've learned informally. I have a question. A nucleus, say cobalt 60, decays. I know how to calculate the probability that it will decay within some certain interval of time, but I can't predict exactly when it will decay. Is there any way, in principle, to predict the exact time that the nucleus will decay? Does any current theory account for why the nucleus decays at one instant in time and not another? I think I've stated the question clearly enough--any thoughts? David >My background in physics comes from Nuclear Power School in the Navy >(back in the early 1970's). The Navy sent me to school so that I [quoted text clipped - 6 lines] >calculate the probability that it will decay within some certain >interval of time, but I can't predict exactly when it will decay. Indeed. >Is there any way, in principle, to predict the exact time that the >nucleus will decay? As far as we know, no. > Does any current theory account for why the >nucleus decays at one instant in time and not another? Current theory not only doesn't account for why it decays in one moment and not another, but most explicitly states that there is no reason for it to decay in one moment versus another. There are just probabilities, that's all. Mati Meron | "When you argue with a fool, meron@cars.uchicago.edu | chances are he is doing just the same" Thanks much! This was what I was taught back in the 1970's, but I had to admit that my education in physics might be out of date. This group looked so hopelessly clogged with the ravings of the mentally ill, that I wasn't sure my message would get through the noise. Thanks again. David On Jan 30, 11:48 am, mme...@cars3.uchicago.edu wrote: > In article <1170182312.081159.53...@h3g2000cwc.googlegroups.com>, "da5id65...@yahoo.com" <da5id65...@yahoo.com> writes: > [quoted text clipped - 26 lines] > Mati Meron | "When you argue with a fool, > m...@cars.uchicago.edu | chances are he is doing just the same" >Thanks much! > >This was what I was taught back in the 1970's, but I had to admit that >my education in physics might be out of date. Oh, it seems fine, to me. >This group looked so hopelessly clogged with the ravings of the >mentally ill, that I wasn't sure my message would get through the >noise. Well, rational messages stand out of the noise, fortunately. As for the mentally ill, I suspect that there is somewhere a group of psychotherapists who direct their patients to post on sci.physics as a form of therapy (vent out their frustrations, agressions, whatever):-) >Thanks again. You're very welcome. Mati Meron | "When you argue with a fool, meron@cars.uchicago.edu | chances are he is doing just the same" > My background in physics comes from Nuclear Power School in the Navy > (back in the early 1970's). The Navy sent me to school so that I [quoted text clipped - 6 lines] > calculate the probability that it will decay within some certain > interval of time, but I can't predict exactly when it will decay. No--Radioactivity appears to be a random process, i.e. it is impossible to predict when an atomic nucleus will decay or which nuclei in a sample will. > Is there any way, in principle, to predict the exact time that the > nucleus will decay? Does any current theory account for why the [quoted text clipped - 3 lines] > > David On Jan 30, 10:38 am, "da5id65...@yahoo.com" <da5id65...@yahoo.com> wrote: > My background in physics comes from Nuclear Power School in the Navy > (back in the early 1970's). The Navy sent me to school so that I [quoted text clipped - 10 lines] > nucleus will decay? Does any current theory account for why the > nucleus decays at one instant in time and not another? To the best of our knowledge, the decay process is completely random. There is a certain probability that it will decay within the next second, and if it does not do so, it starts all over again. It's like tossing a coin until you finally get a 'head': if your first toss was a 'tail', the coin does not remember that fact, so the next toss is in no way affected.' In a large lump of material, the total decay process is the aggregate of many, many individual processes, so it looks regular. However, if you take a small lump, or a lump with low density of radioactive material, you can hear the individual decays in the earphones of a Geiger counter. How do current theories account for this? Well, they describe the decay process using Quantum Mechanics, which describes nature in an inherently random fashion. Many folks don't like that---including Albert Einstein---but it seems to be perfectly in accord with all known experimental results. R.G. Vickson > I think I've stated the question clearly enough--any thoughts? > > David Yes, we used gamma and neutron detectors regularly in the normal operation of the reactor plant. My using cobalt 60 as an example was not arbitrary. That particular isotope was a constant annoyance. The physics we were taught accounted for what we observed in our regular work. It also underlay the applied science we called "reactor kinetics" (k effective and the six factor formula). You might think that we wouldn't have to understand nuclear fission to operate the reactor (imagine Homer Simpson), but Rickover **certainly** didn't see it that way. We were taught *theory*, and I think understanding it *was* of practical, everyday value. Ah, brings back memories. Hard to believe it was all 30 years ago. David > On Jan 30, 10:38 am, "da5id65...@yahoo.com" <da5id65...@yahoo.com> > wrote: [quoted text clipped - 38 lines] > > > David > My background in physics comes from Nuclear Power School in the Navy > (back in the early 1970's). The Navy sent me to school so that I [quoted text clipped - 12 lines] > > I think I've stated the question clearly enough--any thoughts? the time interval between decays is described by a possion distribution > My background in physics comes from Nuclear Power School in the Navy > (back in the early 1970's). The Navy sent me to school so that I [quoted text clipped - 14 lines] > > David Think popcorn. Raise the temperature to the critical point and the corn kernels start popping. But which ones and when? Will E. Google groups seems to be malfunctioning. Maybe they're revising it again. They should just leave it alone! Sorry. Anyway, popcorn is a nice image. It's still interestingly counterintuitive (ituition being not normally based on seeing reality at the quantum level, I suppose) that something happens for no more reason than that is has a probablity greater than zero. What about the Big Bang? Perhaps the universe began because it was possible. Cool! David > What about the Big Bang? Perhaps the universe began because it was > possible. Cool! You've got it! :-) Bob  Signature"Things should be described as simply as possible, but no simpler." A. Einstein > I have a question. A nucleus, say cobalt 60, decays. I know > how to [quoted text clipped - 3 lines] > Is there any way, in principle, to predict the exact time that the > nucleus will decay? No. > Does any current theory account for why the nucleus decays > at one instant in time and not another? No. HUP is intrinsic. The decay constant yields a complete description. [Old Man] > David |
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