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Thread: Radioactive Decay

  1. #1 Radioactive Decay 
    Forum Bachelors Degree x(x-y)'s Avatar
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    I am aware that radioactive decay is a form of exponential decay as the common ratio of the decay of a radioactive isotope is 0 < x > 1. So obviously, as with all exponential decay, the number being multiplied by the common ratio will never become zero- just asymptotically approach zero.

    However, this is where I am slightly confused- as if you have a finite amount of radioactive substance which has a decay rate between 0 and 1, then surely (given enough time) there will be literally "none" of the substance left; it will all have decayed. Is there some law of physics which prevents the entirety of a substance decaying? As I understand exponential decay in mathematical terms, but not in terms of a finite amount of substance which will continue decaying.


    "Nature doesn't care what we call it, she just does it anyway" - R. Feynman
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  3. #2  
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    Any single atom has a finite probability of decaying during a given time interval. If there is a large enough number of them, the radioactive isotope follows an exponential decay rule. When you get down to the last atom, it comes down to probability. It might last a second or another million years.


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  4. #3  
    Reptile Dysfunction drowsy turtle's Avatar
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    Unless it is constantly being observed, in which case it is constantly being forced into the non-decayed superposition and will never decay.
    "The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at or repair." ~ Douglas Adams
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  5. #4  
    Forum Radioactive Isotope MagiMaster's Avatar
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    Every atom in the universe is (for a given definition of constant) being constantly observed.
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  6. #5  
    Reptile Dysfunction drowsy turtle's Avatar
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    And for a given definition of observed presumably?
    "The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at or repair." ~ Douglas Adams
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  7. #6  
    Forum Radioactive Isotope MagiMaster's Avatar
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    No, that's fairly well defined already. (It has nothing to do with humans.)
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