How C14 works

1. Status - under construction
   
   
   
2. Index
   
   
   
   1. Master index of this blog
      
   2. Introduction to this blog
      
   3. Revision history
      
   4. Introduction
      
   5. Piggy-bank example
      
   6. Given/assumed
      
   7. Figuring the percent
      
   8. And there you have it
      
   
   
3. Revsion history
   
   
   
   • Date - activity
     
   • 11/08/06 - introduction, piggy bank
     
   • 11/07/06 - started page
     
   
   
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4. Introduction
   
   Because this will be a long presentation (a couple of pages) it seemed correct to isolate it. The process that 14C goes through happens over thousands of years. Trying to explain in detail a process that occurs on that time scale would be difficult for me so I will use a piggy-bank example to introduce the concept.
   
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5. The piggy bank example
   
   Suppose you own an empty piggy-bank. In this case, you want to save some money but you want to spend some too. So, you decide to put a dime a day into the initially empty bank and take out 10% of what is in there for spending money. Here is how the first several days would go:
   
   
   
   
   1. 10 cents in makes 10 cents in the bank; 10% of 10 cents in the bank is 1 cent for spending money leaving 9 cents
      
   2. 10 cents in makes 19 cents in the bank 10% of which is (rounded up) 2 cents to spend leaving 17 cents
      
   3. 10 cents in = 27 cents in the bank, 10% of that is 3 cents to spend leaving 24 cents
      
   4. add 10 = 34, 10% = 3, 31 left in the bank
      
   5. add 10 = 41, 10% = 4, 37 left in the bank
      
   6. add 10 = 47, 10% = 5, 42 left in the bank
      
   7. add 10 = 52, 10% = 5, 47 left in the bank
      
   8. add 10 = 57, 10% = 6, 51 left in the bank
      
   9. add 10 = 61, 10% = 6, 55 left in the bank
      
   10. add 10 = 65, 10% = 7, 58 left in the bank
       
   11. add 10 = 68, 10% = 7, 61 left in the bank
       
   12. add 10 = 71, 10% = 7, 64 left in the bank
       
   13. add 10 = 74, 10% = 7, 67 left in the bank
       
   14. add 10 = 77, 10% = 8, 69 left in the bank
       
   
   
   As you can see, the pennies available at the end of each turn increases rapidly at first then begins to grow more and more slowly as the 10% coming out takes a larger amount. After several more turns, there would obviously be over 90 cents in the bank. When the amount in the bank became 95 cents then you would put a dime in and take a dime out (9.5 cents rounded up). The amount in the bank would remain 95 cents forever.
   
   This is the process for 14C also.
   
   One final note: visualizing taking 10% out was easy to understand but the calculation would work the same if we said we wanted to keep 90% in the bank.
   
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6. Given/assumed
   
   Now, we have an idea of the process. What do we know?
   
   
   
   
   1. the atmosphere and anything that breathes or absorbs air becomes the bank where the 14C is stored
      
   2. 22 formations occur per second (looking for verification) becomes the deposits
      
   3. any one 14C atom will probably stay in the atmosphere for 5715 years (half-life of 5715 years)
      
   
   
   
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7. Figuring the percentage
   
   The percent to be taken out (the spending money in the piggy-bank example) can be calculated. What percent of removal will result in one-half (50%) as much being in the atmosphere after 5715 years? Another way to say this is what percent would I need to keep each turn to have 50% remaining in 5715 years. The value of 0.99988 works. On a calculator which can process exponentiation (y^x) enter "0.99988 y^x 5715 =" and the result is about .503 or roughly 50% remaining after 5715 years.
   
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8. And there you have it
   
   
   
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