Carbon 14

1. Status - under construction
   
   
   
2. Index
   
   
   
   1. Master index of this blog
      
   2. Introduction to this blog
      
   3. Revision history
      
   4. Introduction
      
   5. What material can be dated
      
   6. Why not other material
      
   7. What plants and animals can be dated
      
   8. Why not other plants and animals
      
   9. What ages can be dated
      
   10. Why not other ages
       
   11. What happens outside those parameters
       
   12. How is the measuring done
       
   13. 
       
   
   
3. Revsion history
   
   
   
   • Date - activity
     
   • 11/03/06 - started layout
     
   • 11/01/06 - started page
     
   
   
   
4. Introduction
   
   Radiocarbon dating (or radiometric dating) is a interesting subject, even for a novice. While there are many factors to take into account, the factors are understandable at a high level. Radiometric dating is used, as the name implies, to discover the age of a substance which contains carbon atoms. The age is expressed as, for example, 10,000 years BP (before the present).
   
   The first set of issues are what material, what subset of the material, and what ages of the material can be dated by this method and what happens when material outside those parameters is dated.
   
   The second set of issues is the handling, preparation, and measuring of the substance.
   
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5. What material can be dated
   
   Clearly, since the method is called carbon-14 dating (14C) this process is exclusivly related to matter containing carbon. Carbon-14 is created when a nitrogen atom (1xN) accepts a xxx. The modified carbon atom is unstable (it doesn't want the extra xxx) and will eventually give the xxx up.
   
   The material must be from a plant or animal (a living thing) because the material must be part of something that breathed or absorbed 14C from the atmosphere or ate another living thing that did.
   
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6. Why not other material
   
   Obviously, material without any carbon in it can not have the carbon measured.
   
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7. What plants and animals can be dated
   
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8. Why not other plants and animals
   
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9. What ages can be dated
   
   An atom of 14C has a half life of approximately 5715 years. This means that if a sample once contained two atoms then 5715 years later the sample probably contains one. If a sample once contained four atoms of 14C then 11,430 years later it probably contains one.
   
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10. Why not other ages
    
    A sample of once living material containing carbon will have 14C from three sources. The first is the 14C from the atmosphere. The second is the 14C created while the sample was buried. The third is contamination which will be discussed a little later. In this section we assume that the sample is not contaminated.
    
    After many (just over 45) half-lives have passed then there is so little 14C remaining that the "real" 14C can not be separated from the "background" 14C.
    
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11. What happens outside those parmeters
    
    If one is trying to discredit radiometric dating then it is tempting to prove that the method is broken by using it outside the parameters. This is similar to complaining that a body thermometer does not work because it will not correctly give the temperature of boiling water.
    
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12. How is the measuring done
    
    The measuring is accomplished using a mass-spectrometer. This instrument measures the ratio of 14C to 12C. Note that counting the number of decays is not the method used and this is due to the long period of time between decays.
    
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    NosyNed says in message 3 that "Radio carbon dating is good for, at the extremes, up to about 50,000 years."
    
    
    Bret reports in message 9 that "Saying C14 is produced within the earth is based on faith (belief) not facts by fringe scientists that have the need to believe C14 is being produced within the earth under normal conditions."
    
    nemesis juggernaut gives a highly rebutted introduction to carbon dating in message 17 (especially in message 21 by crashfrog).
    
    JonF reports in message 18 that
    
    
    in message x that
    
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